Copyright

by

Benjamin Charles Siks

2011

The Thesis Committee for Benjamin Charles Siks Certifies that this is the approved version of the following thesis:

Sedimentary, structural, and provenance record of the Cianzo basin,

Puna plateau-Eastern Cordillera boundary, NW Argentina

APPROVED BY

SUPERVISING COMMITTEE:

Brian K. Horton

Ronald J. Steel

Kitty Milliken

Supervisor:

Sedimentary, structural, and provenance record of the Cianzo basin,

Puna plateau-Eastern Cordillera boundary, NW Argentina

by

Benjamin Charles Siks, B.S. Geo.

Thesis

Presented to the Faculty of the Graduate School of

The University of Texas at Austin

in Partial Fulfillment

of the Requirements

for the Degree of

Master of Science in Geological Sciences

The University of Texas at Austin

May 2011

iv

Acknowledgements

This work could not have been completed without the support of my future wife,

Ashley Bens, my mother Debbie Stann, my father Jan Siks, my siblings, my supervisor

Dr. Brian Horton, my committee members Dr. Ron Steel and Dr. Kitty Milliken, as well

as the members of my research group, and finally the loyal support of my border collie

Pippin.

v

Abstract

Sedimentary, structural, and provenance record of the Cianzo basin,

Puna plateau-Eastern Cordillera boundary, NW Argentina

Benjamin Charles Siks, MS GeoSci

The University of Texas at Austin, 2011

Supervisor: Brian K. Horton

The fault-bounded Cianzo basin represents a Cenozoic intermontane depocenter

between the Puna plateau and Eastern Cordillera of the central Andean fold-thrust belt in

northern Argentina. New characterizations of fold-thrust structure, nonmarine

sedimentation, and sediment provenance for the shortening-induced Cianzo basin at 23°S

help constrain the origin, interconnectedness, and subsequent uplift and exhumation of

the basin, which may serve as an analogue for other intermontane hinterland basins in the

Andes. Structural mapping of the Cianzo basin reveals SW and NE-plunging synclines

within the >6000 m-thick, upsection coarsening Cenozoic clastic succession in the shared

footwall of the N-striking, E-directed Cianzo thrust fault and transverse, NE-striking

Hornocal fault. Growth stratal relationships within upper Miocene levels of the

succession indicate syncontractional sedimentation directly adjacent to the Hornocal

fault.

Measured stratigraphic sections and clastic sedimentary lithofacies of Cenozoic

basin-fill deposits show upsection changes from (1) a distal fluvial system recorded by

vi

fine-grained, paleosol-rich, heavily bioturbated sandstones and mudstones

(Paleocene‒Eocene Santa Bárbara Subgroup, ~400 m), to (2) a braided fluvial system

represented by cross-stratified sandstones and interbedded mudstones with 0.3 to 8 m

upsection-fining sequences (Upper Eocene–Oligocene Casa Grande Formation, ~1400

m), to (3) a distributary fluvial system in the distal sectors of a distributary fluvial

megafan represented by structureless sheetflood sandstones, stratified pebble

conglomerates and sandstones, and interbedded overbank mudstones (Miocene Río

Grande Formation, ~3300 m), to (4) a proximal alluvial fan system with thick

conglomerates interbedded with thin discontinuous sandstone lenses (upper Miocene

Pisungo Formation, ~1600 m).

New 40Ar/39Ar geochronological results for five interbedded volcanic tuffs

indicate distributary fluvial deposition of the uppermost Río Grande Formation from

16.31 ± 0.6 Ma to 9.69 ± 0.05 Ma. Sandstone petrographic results show distinct

upsection trends in lithic and feldspar content in the Casa Grande, Río Grande, and

Pisungo formations, potentially distinguishing western magmatic arc (Western

Cordillera) sediment sources from evolving eastern thrust-belt sources (Puna‒Eastern

Cordillera). In addition to growth stratal relationships and 40Ar/39Ar constraints,

conglomerate clast compositions reflect distinct lithologic differences, constraining the

activation of the Cianzo thrust and coeval movement on the reactivated Hornocal fault.

Finally, U-Pb geochronological analyses of sandstone detrital zircon populations in

conjunction with paleocurrent data and depositional facies patterns help distinguish

localized sources from more distal sources west of the basin, revealing a systematic

eastward advance of Eocene to Miocene fold-thrust deformation in the central Andes of

northern Argentina.

vii

Table of Contents

List of tables ........................................................................................................... ix

List of figures ...........................................................................................................x

Chapter 1. Introduction and geologic context .........................................................1

Introduction .....................................................................................................1

Geologic setting ..............................................................................................3

Chapter 2. Tectonic, stratigraphic, and structural framework ................................7

Tectonic history ..............................................................................................7

Regional stratigraphy ....................................................................................10

Structural framework ....................................................................................13

Growth strata .................................................................................................16

Chapter 3. Sedimentology and stratigraphy ..........................................................19

Facies associations ........................................................................................19 40Ar/39Ar age geochronology ........................................................................34

Chapter 4. Depositional systems ............................................................................36

Chapter 5. Provenance ...........................................................................................40

Sandstone compositons .................................................................................40

Conglomerate clast compositions .................................................................46

Detrital zircon U-Pb geochronology .............................................................48

Chapter 6. Basin reconstruction and discussion ....................................................55

Santa Bárbara Group .....................................................................................55

Casa Grande Formation ................................................................................56

Río Grande Formation ..................................................................................57

Pisungo Formation ........................................................................................58

Chapter 7. Conclusions ..........................................................................................61

Appendix 1. Point count tables .............................................................................65

Appendix 2. Clast count tables .............................................................................67

Appendix 3. U-Pb geochronological results .........................................................69

viii

Appendix 4. McBride, 2008 U-Pb results .............................................................85

References ..............................................................................................................89

ix

List of Tables

Table 1. Description and interpretation of lithofacies . ...................................20

Table 2. Summary of facies associations and interpretations .........................21

Table 3. 40Ar/39Ar data for interbedded tuffs ..................................................35

Table 4. Parameters for sandstone mineraloglical point counting. .................41

x

List of Figures

Figure 1. Overview map of South America .......................................................4

Figure 2. Regional structures and provenace terranes in northern Argentina. ...6

Figure 3. Location of Cianzo basin and regional structures. ..............................9

Figure 4. Regional stratigraphy of the Cianzo basin ........................................11

Figure 5. Geologic map of Cianzo basin and surronding structures ................14

Figure 6. Growth strata within the Pisungo Formation ....................................18

Figure 7. Simplified stratigraphic section of Cenozoic fill ..............................22

Figure 8. Measured stratigraphic sections in the Cianzo basin ........................23

Figure 9. Lower Río Grande facies photographs .............................................26

Figure 10. Upper Río Grande facies photographs ..............................................29

Figure 11. Pisungo facies photographs...............................................................33

Figure 12. Depostional systems evolution diagram ...........................................39

Figure 13. Sandstone petrographic ternary diagrams .........................................44

Figure 14. Lithologic conglomerate clast count diagrams .................................47

Figure 15. Detrital zircon U-Pb relative probability plots ..................................51

Figure 16. 2D regional basin reconstruction diagrams .......................................60

1

Chapter 1. Introduction and geologic context

INTRODUCTION

Many studies attribute crustal thickening and surface uplift in the central Andean

fold-thrust belt and Puna‒Altiplano plateau to E‒W shortening of Neogene age (e.g.,

Isacks, 1988; Vandervoort et al., 1995; Baby et al., 1997; Allmendinger et al., 1997;

Jordan et al., 1997; Davila and Astini, 2003). Conversely, other investigations argue that

stratigraphic, provenance, and geochronologic evidence suggest significantly earlier

foreland basin conditions and initial mountain building during the Paleogene (e.g., Starck

and Vergani, 1996; Horton and DeCelles, 1997; Sempere et al., 1997; Kraemer et al.,

1999; Horton et al., 2001; Coutand et al., 2001; Carrapa et al., 2005). Additional debate

surrounds the progression of shortening in the central Andes of Argentina and Bolivia,

with some investigations suggesting sequential advance from west to east, from the

Western Cordillera magmatic arc to the fold-thrust belt of the Eastern Cordillera and

Subandean Zone (e.g., Noblet et al., 1996; Reynolds et al., 2000; Coutand et al., 2001;

DeCelles and Horton, 2003; Kley et al., 2005). Alternatively, others interpret uneven

growth of the orogen in a non-systematic fashion resulting in a series fragmented

intermontane basins (Hongn et al., 2007; Hain et al., 2011; Strecker et al., 2011).

Kinematic and geodynamic models for the total magnitude, duration, and rate of crustal

shortening in the central Andes are greatly affected by these conflicting ideas over the

onset and spatial progression of Andean deformation. Cenozoic basins in the central

Andes provide a critical resource for determining the temporal and spatial context for

pre-, syn-, and post-orogenic fill in these basins, helping to constrain the timing of

shortening and associated crustal thickening (Allmendinger et al., 1997; Horton and

2

DeCelles, 1997; Lamb and Hoke, 1997; Horton, 1998; Horton et al., 2001; Coutand et al.,

2001; Mosquera and Ramos, 2006).

Construction of the Eastern Cordillera and Puna‒plateau in northern Argentina is

not well understood. Some stratigraphic and structure studies interpret earliest shortening

in northern Argentina to have initiated during the Eocene to Oligocene in the Puna

plateau (Kraemer et al., 1999; Coutand et al., 2001). In contrast, other attribute basin

sedimentation in extensional and postrift thermal processes that persisted into the

Oligocene‒early Miocene prior to major Neogene shortening (Jordan et al, 2001; Davila

and Astini, 2003; Marquillas et al., 2005). In southern Bolivia, the main phase of

shortening in the Eastern Cordillera of southern Bolivia is bracketed between ~50-40 and

10 Ma (Gubbels et al., 1993; Horton et al., 2001; Müller et al., 2002; DeCelles and

Horton, 2003; Gillis et al, 2006; Ege et al., 2007). Whereas deformation in the Eastern

Cordillera of Bolivia ceased at ~10 Ma (Gubbels et al., 1993), modern fault scarps and

seismicity in the Eastern Cordillera show that the northern Argentina counterpart remains

active (Cahill et al., 1992; Marrett et al., 1994). Further disagreement among studies of

southern Bolivia and northern Argentina involve conflicting interpretations of either a

systematic eastward advance or an irregular progression of uplift (DeCelles and Horton,

2003; Elger et al., 2005; Ege et al., 2007). Intermontane basins within the ~4‒km‒high

Eastern Cordillera and Puna‒plateau of northern Argentina provide first-order records of

Andean orogenesis and help address the potential integration and segregation of

sedimentary basins developed and subsequently deformed during Cenozoic shortening.

Although there have been numerous investigations of the Cenozoic strata of

northern Argentina (e.g., Boll and Hernández, 1986; Coutand et al., 2001; Hongn et al.,

2007), little is known about the timing of deformation, interconnectedness of presently

isolated basins, and potential fragmentation of a former broad foreland basin into an

3

intermontane hinterland basin configuration. In this paper we present stratigraphic,

structural, geochronological, and petrographic evidence to delineate the depositional

environments, structural setting, age, and provenance signatures of the nonmarine clastic

fill of the Cianzo basin, specifically the Miocene Río Grande Formation and late Miocene

Pisungo Formation. When combined with regional stratigraphic and structural

relationships, a synthesis of the origin, extent, and evolution of shortening-related basins

in the central Andes is proposed utilizing the structural style, timing, and uplift in the

Cianzo basin. Finally, the character and timing of the transition from Mesozoic extension

to Cenozoic shortening, although not precise, is illustrated for northern Argentina.

GEOLOGIC SETTING

The Andes mountains (Figure 1) are the type example of a contractional orogenic

belt formed along an ocean-continent convergent margin. The Nazca plate descends

eastward beneath South America at a dip of ~30° in northernmost Argentina, but farther

to the north and south the angle of subduction is nearly horizontal (Isacks, 1988; Cahill

and Isacks, 1992; Allmendinger et al., 1997). The broad low-relief Puna-Altiplano

plateau at ~4 km altitude is the largest diagnostic topographic feature observed in the

central Andes between ~15°S and ~27°S (roughly 300 km wide and 2000 km long)

(Figure 1)(Isacks, 1988). The Puna-Altiplano plateau is located between the Western and

Eastern Cordilleras, which give the plateau its internal drainage (Coutand et al., 2001).

4

Figure 1. Map of the central Andes showing major tectonomorphic provinces (CC–Coastal Cordillera; LV–Longitudinal Valley (forearc basin); Precordillera (western Andean slope); Western Cordillera (magmatic arc); Altiplano-Puna (orogenic plateau); Eastern Cordillera (retroarc fold-thrust belt); Subandean and Santa Bárbara Zone (foothills fold-thrust belt); SP–Sierras Pampeanas (basement uplifts); Chaco plain (foreland basin) (modified from Horton et al., 2001).

5

The central Andes (Figure 1) are separated into distinct tectonomorphic zones

with diagnostic topographic and stratigraphic components distinguishable from west to

east (Figure 1). Along the western continental margin, the Coastal Cordillera is a

remnant Mesozoic magmatic arc affected by Cenozoic subduction erosion (Rutland,

1971; Allmendinger et al., 1997). The Longitudinal Valley is a forearc basin consisting

of Miocene-Quaternary sedimentary rocks. Farther inland is the Precordillera slope of

the western Andes (Alonso et al., 2006; Arriagada et al., 2006). The Western Cordillera

magmatic arc is composed of dacitic to andesitic stratovolcanoes marking the Chile-

Argentina border and western edge of the Puna plateau (Kay et al., 1994).

In northern Argentina, the 300‒km‒wide Puna plateau is bordered by the Eastern

Cordillera, a thick-skinned, east-verging retroarc fold-thrust belt comprised of mostly

Paleozoic metasedimentary rocks bounding the fold-thrust foothills of the Subandean

zone and lowland Chaco foreland basin in the east (Mon and Salfity, 1995; Kley et al.,

2005). Individual ranges within the Eastern Cordillera reach altitudes ~4000 m in

elevation, and define an along-strike transition from Cambrian-Ordovician strata north of

25°S to faulted Precambrian basement blocks to the south (Mon and Salfity, 1995).

Farther east, the thin-skinned Subandean Zone belt marks the eastern limit of the central

Andes (Echavarria et al., 2003). The Chaco plain is part of a regional Neogene-

Quaternary foreland basin that continues >500 km eastward from southern Bolivia and

northern Argentina to the Precambrian shield in easternmost Argentina, Paraguay, and

Brazil (Horton and DeCelles, 1997).

6

Figure 2. Regional map of the central Andes of northern Argentina, northern Chile, and southern Bolivia, showing the main tectonomorphic zones, major fold‒thrust belts, and faults (solid lines with teeth on hangingwall) overlain on shaded topography (modified from Carrapa and Trimble, 2010). Color shading denotes diagnostic source regions of differing age (Ramos, 2008).

7

Chapter 2. Tectonic, stratigraphic, and structural framework

TECTONIC HISTORY

The tectonomagmatic history of west-central South America controls the

distribution of lithologies of differing ages, which become vitally important when

addressing the composition and U-Pb detrital zircon signatures of potential sediment

sources in northern Argentina (see color shading in Fig. 2). An understanding of pre-

Andean deformation, Mesozoic rifting, and Cenozoic shortening is also required to

constrain deformation styles and depositional models. Described below are the major

tectonomagmatic events, subdivided into two broad groups encompassing Proterozoic-

Paleozoic and Mesozoic-Cenozoic time.

Proterozoic and Paleozoic

The Sunsás–Grenville (1200–1000 Ma; Figure 2) orogenic signal can be traced

across much of South and North America (Ramos, 2008). The Mesoproterozoic Sunsás

event involved the amalgamation of the Antofalla and Arequipa continental terranes

along the Pacific margin of Amazonia, leading to formation of the Rodinia

supercontinent (Ramos, 2008). A principal age signal of this event is ubiquitous in

sedimentary rocks throughout the central Andes (Adams and Miller, 2007; Chew et al.,

2007)

The Pampean orogenic episode (570‒520 Ma; Figure 2) is marked by

Neoproterozoic-Early Cambrian rifting and development of the Puncoviscana basin

(Pankhurst and Rapela, 1998; Zimmermann, 2005; Ramo, 2008). Igneous intrusions and

volcanogenic sediments shed into this basin have distinct age peaks from ~570 to ~520

Ma (Rapela et al., 1998), and represent the widespread Puncoviscana Formation,

characterized by quartzites and phyllites that underwent low-grade metamorphism during

8

subsequent Paleozoic tectonism (Lork and Bahlburg, 1993; Ramos, 2008). An Early

Cambrian switch from a passive margin to subduction zone along the Pacific margin

resulted in closure of the Puncoviscana basin and subsequent emplacement of granitoids

in the Puncoviscana belt (Ramos, 1988, 2008; Omarini et al., 1999)

Initiation of the Famatinian orogenic episode (500‒435 Ma; Figure 2) is marked

by rifting along the western margin of Gondwana at ~ 500 Ma (Ramos, 2008). As

Ordovician rifting continued, a marine clastic platform formed (Ramos, 2008). Marine

siliciclastic and volcaniclastic sediments from sources such as the coeval magmatic arc,

known as the Faja Eruptiva give the clastic Ordovician platform distinct age peaks from

~500 to ~435 Ma (Rapela et al., 1998; Coira et al., 1982, 1999).

Mesozoic and Cenozoic

A zone of continental backarc extension, the Salta Rift, developed in NW

Argentina at ~21°‒25° during Cretaceous time with deposition of the Salta Group across

a widespread, irregular basin (Salfity and Marquillas, 1994; Marquillas et al., 2005).

Cenozoic East-west compression along the western continental margin of central South

America resulted in inversion of local rift structures and initiation of a retroarc fold-thrust

belt (e.g., Marquillas and Salfity, 1988; Mon and Salfity, 1995; Viramonte et al., 1999;

Kley and Monaldi, 2002; Kley et al., 2005; Carrera et al., 2006; Carrera and Muñoz,

2008). Basin fill in northern Argentina records a distinct shift from marine Upper

Cretaceous (Balbuena Subgroup) to nonmarine Paleogene deposition (Santa Bárbara

Subgroup) (Mon and Salfity, 1995; Coutand et al., 2001, Marquillas et al., 2005). Post-

extensional subsidence may have resulted from thermal contraction due to the cooling of

the Salta Rift and Late Cretaceous arc (Jordan and Alonzo, 1987) or, alternatively,

earliest crustal loading by Andean thrust sheets (Kraemer et al., 1999).

9

Figure 3. Generalized geologic map of the Cianzo basin region in northern Argentina (modified from Gonzalez et al., 2003), showing major structures and measured section locations for Cenozoic basin fill. Phanerozoic stratigraphy (pЄp–Precambrian–Cambrian Puncoviscana Formation, Єmn–Cambrian Mesón Group, Osv–Ordovician Santa Victoria Group, SDs–Silurian/Devonian Lipeon/Barite Formations, Cmg–Carboniferious Machareti Group, Kpi–Cretaceous Pirgua Formation, Kbs–Cretaceous Balbuena Subgroup, Esb–Paleogene–Eocene Santa Bárbara Subgroup, Ecg–Eocene–Oligocene Casa Grande Formation, Nrg–Miocene Río Grande Formation, Npi–Miocene Pisungo Formation).

10

REGIONAL STRATIGRAPHY

In the Cianzo basin region of northwest Argentina (Figure 3), the regional

geologic column is composed of three main rock packages (Figure 4); Proterozoic

basement and Paleozoic metasedimentary rocks, Mesozoic synrift strata, and Cenozoic

Andean postrift and foreland basin deposits (Figures 3 and 4) (Coutand et al., 2001;

Allmendinger et al., 1997; Ramos, 2008). Along with the regional lithotectonic and

tectonomorphic (color shading in Figure 7), the distinct attributes of these different rock

packages play an important role in distinguishing the compositional and geochronological

provenance of Cenozoic fill of the Cianzo basin. The Proterozoic–Paleozoic basement

assemblage records the Pampean (570–520 Ma) and Famatinian (500‒435 Ma) Orogenic

events and include: 1) the Puncoviscana Formation (Neoproterozoic–Cambrian)

composed of low-grade metasedimentary rocks intruded by granitoids of the same age

and deformed during Pampean orogenesis (Turner, 1979; Ramos, 2008); 2) the Mesón

Group (Upper Cambrian), a package of quartzites recording shallow marine deposition

and subsequent metamorphism (Turner, 1979); 3) the Santa Victoria Group (Ordovician),

clastic basin fill of a marine platform with related igneous intrusions of the Ordovician

Faja Eruptiva and coeval deformation during the Famatinian deformation (Coutand et al.,

2001; Ramos, 2008); and 4) a Silurian-Devonian succession of shales and sandstones

deposited in shallow marine environments (Starck, 1995).

11

Figure 4. Stratigraphic nomenclature for the Cianzo basin and surrounding regions along the Puna plateau–Eastern Cordillera boundary, northern Argentina (ages from Boll and Hernández, 1986; Gonzales et al., 2003)

12

The Mesozoic–Cenozoic stratigraphic succession unconformably overlies

Precambrian and Paleozoic rocks and can be subdivided into three main Andean

tectonostratigraphic units: synrift, postrift, and foreland basin deposits (Figure 4). These

units recorded the evolution from Cretaceous extension, with Neocomian to Campanian

deposition of the synrift Pirgua Subgroup (lower Salta Group) to a subsequent postrift

and foreland basin deposition of the Maastrichtian through Paleogene Balbuena and

Santa Bárbara Subgroups (upper Salta Group) and upper Eocene through Miocene Casa

Grande, Río Grande, and Pisungo formations (Orán Group)(Salfity and Marquillas, 1994;

Coutand et al., 2001; Marquillas et al., 2005). The Salta Group is composed of three

subgroups encompassing changing depositional environments from a backarc rift to

postrift setting (Marquillas et al., 2005). The Cretaceous Pirgua Subgroup represents

early synrift basin fill composed dominantly of conglomerates and sandstones

(Marquillas et al., 2005). The Balbuena Subgroup is a postrift sequence characterized by

a lower eolian sandstone (Lecho Formation) overlain by a marginal marine limestone

(Yacoraite Formation), with deposition from the Maastrichtian to early Paleocene

(Marquillas et al., 2005). The Paleocene‒Eocene Santa Bárbara Subgroup comprises

three formations composed of fine- to medium-grained sandstones, mudstones, and

paleosols representing reduced accumulation rates (Marquillas et al., 2005).

The upper Eocene–upper Miocene age Orán Group (Boll and Hernández, 1986) is

an upsection-coarsening assemblage of three nonmarine formations. The Casa Grande,

Río Grande, Pisungo formations, comprise the fill of Cianzo basin and are the primary

focus of this study.

13

STRUCTURAL FRAMEWORK

New geologic mapping documents cross-cutting and overlapping relationships

that reveal the geometry, sequence, and relative timing of sedimentation and deformation

in the Cianzo basin. The principal structures in the field study area include: (1) ) the NE-

striking, Hornocal fault; (2) the N-striking, E-directed Cianzo thrust; (3) the N-striking,

W-directed Zenta thrust; (4) SW and NE-trending synclines in Cenozoic clastic

succession in the footwall of Hornocal fault; (5) the N-trending Cianzo syncline south of

the Hornocal fault (Amengual and Zanettini 1973, Kley et al., 2005).

14

Figure 5. Geologic map of the Cianzo basin showing structural and stratigraphic relationships among the Cianzo thrust, Hornocal fault, Hornocal footwall syncline, and Cianzo syncline, as well as locations of growth strata (Fig. 6).

15

The NE-striking Hornocal fault is a steep, SE-dipping, sinistral reverse fault with

a minimal displacement estimated at ~6500 m that places Cretaceous‒Paleogene strata

(Salta Group) over Oligocene‒Miocene basin fill, and marks the southern and eastern

margins of the Cianzo basin (Figures 3 and 5) (Amengual and Zanettini, 1973, Kley et

al., 2005). The Hornocal fault marks the former northern margin of a Cretaceous

extensional subbasin and originated as a large transverse normal fault during

Neocomian‒Cenomanian deposition of the conglomeratic Pirgua Subgroup within the

Salta rift system (Salfity and Marquillas, 1994). Evidence for Cretaceous normal

displacement on the Hornocal fault come from: (1) the selective presentation of thick

sedimentary packages of Cretaceous and upper Paleozoic strata only on the south flank of

the fault; (2) coarse‒grained, fault proximal facies in the exceptionally thick (~2400 m)

Pirgua Subgroup: and (3) normal offset still observed in the northeast limit of the

Hornocal fault (Figure 3)(Kley et al., 2005). Subsequent east-west Andean compression

led to inversion of some extensional faults, with the NE-trending Hornocal fault

reactivated as an oblique reverse fault with a significant strike-slip component (Kley et

al., 2005). The N-striking, E-verging Cianzo thrust (Figures 3 and 5) marks the western

margin of the Cianzo basin, placing Neoproterozoic-Cambrian low-grade

metasedimentary rocks (Puncoviscana Formation and Mesón Group) eastward over

Cenozoic sedimentary rocks (Santa Bárbara subgroup, and Casa Grande, Río Grande, and

Pisungo formations).

At the southwestern extent of the Cianzo basin, the Hornocal fault intersects the

Cianzo thrust in map view (Figures 3 and 5). Field mapping of cross-cutting

relationships illustrate that the Cianzo thrust cross-cuts the Hornocal fault. Although

fault displacement may have been partially contemporaneous, this relationship requires

final motion on the Cianzo thrust post-dates final activity on the Hornocal fault.

16

Although the Hornocal fault is commonly considered a single structure, new

mapping reveals two parallel NE-striking, SE-dipping strands of the Hornocal fault in the

southwestern part of the study area (Figure 5). The shorter northern fault strand places

hangingwall Cretaceous‒Oligocene strata against the upper Oligocene‒Miocene Río

Grande Formation in the footwall. Although the Río Grande strata are folded into a

footwall syncline, the upper Miocene Pisungo Formation unconformably overlaps this

northern fault strand and therefore post-dates its displacement. In contrast, the main

thoroughgoing strand of the Hornocal fault to the south cuts the Pisungo Formation,

forming a well developed overturned asymmetrical footwall syncline. An apparent left

lateral separation of the Cretaceous‒Paleogene boundary by ~1.1 km (Figure 5), which

appears to conflict with the dextral interpretation of Kley et al. (2005). However, this

apparent offset can be partially explained by vertical motion and erosional beveling of a

previously formed Cianzo syncline on the southern fault block. Although dextral motion

remains plausible, the required vertical motion and well-developed footwall syncline

suggest the Hornocal accommodated significant reverse displacement during Cenozoic

shortening. To the northeast, the Hornocal fault merges with the N-striking, W-directed

Zenta thrust, which places Ordovician rocks over Cenozoic basin fill (Figure 3)(Kley et

al., 2005). The complex cross-cutting geometric linkage of the Hornocal fault with the

Zenta fault suggests a kinematically linked system accommodating shortening and dextral

transpression in the Cianzo basin.

GROWTH STRATA

The results of structural and stratigraphic mapping along the southeastern margin

of the Cianzo basin reveal growth strata in a footwall syncline over the Hornocal fault

17

(Figure 5). Bedding geometries preserved in conglomeratic deposits of the upper

Pisungo Formation correlate with motion along on the Hornocal fault and progressive

tilting during deposition (Figure 6). These footwall growth strata in the Pisungo

Formation indicate that the Hornocal fault was active during late Miocene deposition, as

demonstrated by internal geometries of Pisungo conglomerate beds (Figure 6).

The first line of evidence for growth strata includes an upsection change in the dip

of Pisungo conglomeratic strata closest to the Hornocal fault, in the partially overturned

southeastern limb of the syncline. The dip values gradually change upsection from

70°ESE overturned, to 45°WNW, which constitutes a total rotation of ~115° on the

southeastern limb (Figure 6). The second line of evidence for growth strata in the

Pisungo Formation comes from a change in bed thickness across the axis of the syncline.

A thinner (~40 m) section comprises the southeastern syncline limb adjacent to the

Hornocal fault. Whereas the equivalent section in the northwestern limb has a much

greater thickness of ~80 m (Figure 6). Finally, internal angular unconformities in the

southeastern limb (Figure 6) suggest syndepositional tilting movement during Pisungo

deposition. These three lines of geometric evidence (upsection decrease in dip, internal

angular unconformities, and thinning toward structure) require progressive

syndepositional tilting, most likely on the flank of a fault propagation fold at the tip of the

Hornocal fault (e.g., Zapata and Allmendinger, 1996; Horton, 1998; Horton et al., 2002),

instead of illustrating growth triangle features (Suppe et al., 1992).

18

Figure 6. Photographs and line drawing of stratal geometries within the conglomeratic Pisungo Formation defining an asymmetric overturned footwall syncline adjacent to the Hornocal fault. (A) Photomosaic and (B, C) line drawing of footwall syncline identifying pre-growth succession and overlying growth stratal succession with internal angular unconformities, stratigraphic thickening away from the fault, and upsection decrease in stratal dip (from 70° overturned to 45° upright).

19

Chapter 3. Sedimentology

FACIES ASSOCIATIONS

A total of six stratigraphic sections were measured in the Cenozoic fill of the

Cianzo basin, comprising a continuous succession from the Paleocene‒Eocene Santa

Bárbara Subgroup to the top of the upper Miocene Pisungo Formation (Figures 7 and 8).

Individual beds were measured at a 10 cm scale using a 1.5 m Jacob staff. Correlations

among sections were made by projecting distinctive stratigraphic horizons along strike.

The following sedimentological descriptions and interpretations are based on measured

sections of the Upper Río Grande and Pisungo formations, which can be divided into 6

facies associations representative of braided fluvial systems, distributary fluvial

(megafan) systems and alluvial fans (Table 2). Each facies association consists of an

assemblage of individual lithofacies, using categories modified from Miall (1977, 1996)

and Uba (2005) (Table 1). Descriptive and interpretative summaries of the mudstone

(F1), sandstone (S1, S2), and conglomerate (G1, G2, G3) facies associations are provided

in Table 2.

20

Table 1. Summary of lithofacies for the Río Grande and Pisungo formations (after Miall, 1985, 1996; Uba et al., 2005) Code Description Thickness Interpretation

Fm Structureless mudstone; occasional pedogenic alteration; sharp basal contacts

0.1–10 c m

Suspension fallout deposits in overbank settings

Fl Finely laminated mudstone; occasionally calcareous; sharp basal contacts

0.1–10 cm Suspension fallout deposits in overbank settings

Sl Planar laminated, moderately to well sorted, subrounded, very fine- to fine-grained sandstone; sharp basal contacts

0.2–3 m Plane-bed deposition, lower flow regime in channels

Sm Structureless, tabular bedded, moderately sorted, subangular to subrounded, medium- to very coarse-grained sandstone; sharp basal contacts

0.2–3 m Rapid sheetflow or sediment gravity flow, with unconfined deposition

Sh Horizontally stratified, poorly sorted, very fine- to coarse-grained sandstone; occasional pebble lags; slightly erosive contacts

0.4–4 m Plane-bed deposition in channels, upper flow regime

St Trough cross-stratified, lens-shaped, poorly to well sorted, subangular, fine- to medium-grained sandstone; occasional pebble lags; erosive basal contacts

0.2–3 m Migration of 3D sand dunes in channels

Sp Low angle, tabular cross-stratified, moderately sorted, subrounded, very fine- to coarse-grained sandstone; occasional pebble lags

0.3–3.5 m Migration of 2D sand dunes in channels

Sb Bioturbated, moderately to well sorted, subangular to subrounded, very fine- to medium-grained sandstone

0.2–3 m Overbank or abandoned channel deposit

Gh Horizontally stratified, lens-shaped, poorly sorted, clast supported, imbricated, subrounded, pebble–cobble conglomerate; normal grading intervals

0.1–3 m Longitudinal bars deposited during high discharge

Gt Trough cross-stratified, lens-shaped, moderately sorted, clast supported, imbricated, subangular to subrounded, pebble conglomerate; normal grading intervals

0.1–3 m Transverse bars deposited in channels

Gd Structureless, poorly sorted, clast and matrix supported, subrounded to rounded, pebble–boulder conglomerate

1–10 m Rapid deposition by streamfloods, or sediment gravity flows

Gco Horizontally stratified, moderately sorted, clast supported, slightly imbricated, pebble–cobble conglomerate; inverse grading

1–5 m Traction bedload deposition by sheetflows

21

Table 2. Summary of facies associations and interpretations for the Río Grande and Pisungo formations Facies association Lithofacies Description Interval thickness Interpretation Stratigraphic

occurrence F1: Mudstone Fm, Fl Structureless, laminated, reddish brown mudstone;

pedogenically altered; interbedded intervals contain facies association S1

≤ 8 m Suspension fallout deposition in fluvial overbank setting

Río Grande Fm (lower)

S1: Thick bedded, structureless sandstone

Sm, Sb Structureless, tabular, fine- to coarse-grained sandstone; sharp basal contacts; commonly associated with facies association F1, comprising normally graded intervals 0.3–8 m thick

< 25 m Sheetflood deposition in distal fluvial settings

Río Grande Fm (lower)

S2: Cross-stratified sandstone

Sh, St, Sp, Sl Medium- to coarse-grained, cross-stratified sandstone; common pebble lags; lens-shaped beds with erosive basal contacts; normal grading

< 6 m Upper and lower flow regime channel, base, and bartop sand deposition in a fluvial system

Río Grande Fm (lower, upper)

G1: Upsection fining, cross-stratified pebble conglomerate and sandstone

Gt, Sp, St, Sh Lens-shaped, well-sorted, imbricated, clast supported, pebble conglomerate with interbedded medium- to coarse-grained sandstones; normal grading into facies association S2 is common; erosive basal contacts

< 20 m Gravelly and sandy channel deposition in a distributary braided fluvial system

Río Grande Fm (lower, upper)

G2: Horizontally stratified pebble–cobble conglomerate

Gh, Gt, Gco Horizontally stratified, moderately sorted, imbricated, clast-supported, pebble–cobble conglomerate with interbedded medium- to very coarse-grained sandstone; sharp to slightly erosional basal contact

≤ 80 m Sheetflows on an alluvial fan Pisungo Fm

G3: Structureless, laterally extensive pebble–boulder conglomerate

Gd, Gt, Gh Structureless, laterally extensive, poorly sorted, clast and matrix supported pebble–boulder conglomerate with rare interbedded coarse- to very coarse-grained sandstone lenses; sharp basal contact

>100 m Gravelly hyperconcentrated flows on an alluvial fan and rare clast rich debris flows

Pisungo Fm

22

Figure 7. Generalized stratigraphic column for the Cianzo basin showing major stratigraphic units, approximate depositional ages, and upsection increase in grain size.

23

Figure 8. Composite measured stratigraphic section of Cenozoic clastic fill of the Cianzo basin (see Fig. 3 for location) showing lithologic relationships, stratigraphic units (Santa Bárbara Group, Casa Grande Formation, Río Grande Formation, Pisungo Formation), paleocurrents, conglomerate clast counts, sandstone petrographic samples, detrital zircon samples, and volcanic tuff samples with corresponding 40Ar/39Ar ages.

24

F1. Mudstone

Description

Facies association F1 consists of fine-grained structureless (massive) and

laminated mudstone beds (Figure 9B). Evidence for pedogenic alteration, bioturbation,

and small (< 2 cm) calcareous nodules are present throughout the mudstones. Individual

bed thickness ranges from 0.1‒10 cm, and extend laterally for 15-20 m (Figure 9A, C).

Larger intervals constitute packages up to 8 m thick (Figure 9C, D, and E). Contacts with

underlying beds are sharp and non-erosive (Figure 9B). The mudstone lithofacies are

typically interbedded with the S1 facies association, completing overall upsection-fining

sequences with thicknesses ranging from 0.3 to 8 m and occurrence is typically in the

lower Río Grande Formation.

Interpretation

Facies association F1 is interpreted as overbank deposits of a fluvial floodplain.

The presence of fine laminae suggest deposition from a standing body of water, most

likely due to separate events representing individual floods or by continual slow settling

of fine-grained sediment from suspension (Miall, 1996). Bioturbation, blocky pedogenic

structures, and calcareous nodules all suggest a semiarid environment with stabilization

of the floodplain between flooding events (Miall, 1996).

S1. Thick bedded, structureless sandstone

Description

Facies association S1 is characterized by fine- to coarse-grained, structureless,

tabular sandstones. The sandstone beds lack any distinct sedimentary structures to define

25

internal stratification (Figure 9C, D). Thicknesses of sandstone beds range from 0.1–6 m,

and extend laterally for 20–60 m (Figure 9A, C). Large intervals of stacked sandstone

sheets can reach up to 25 m in thickness (Figure 9C). Basal contacts are typically sharp

and planar, giving the sandstone beds a tabular appearance (Figure 9B, D). Upsection

fining characteristics are commonly developed, and are typically associated with facies

association F1 (Figure 9A, B, C, D). Rare carbonate nodules and isolated zones of

bioturbation occur in some units of S1, typically in the lower Río Grande Formation.

Interpretation

Facies association S1 is interpreted as hyperconcentrated sandy sheet floods on

distal regions of a distributary fluvial system (Steel and Aasheim, 1978; Hampton and

Horton, 2007; Weissmann et al., 2010). The internally structureless character of the beds

in conjunction with the texture, lack of channelization, and tabular geometry of the S1

beds, indicate that unconfined flows spread out over relatively planar surfaces during

upper flow regime conditions (DeCelles et al., 1991; Hartley, 1993). As flows waned,

progressively finer materials were deposited, resulting in upsection fining sequences

(Miall, 1996).

26

Figure 9. Photographs of distal braided fluvial facies associations F1 and F2 in the lower Río Grande Formation. (A) Laterally extensive, interbedded sandstones (S1) and mudstones (F1) showing Río Grande / Pisungo contact (B) Interbedded stratified sandstone and mudstone with blocky pedogenic structures, hammer for scale. (C) Tabular, nonerosive interbedded structureless sandstones and mudstones. (D) Thick, nonerosive structureless, homogeneous sandstones and mudstones.

S2. Cross-stratified sandstone

Description

Facies association S2 is characterized by medium- to coarse-grained, cross-

stratified sandstones. Low angle tabular cross-stratification commonly grades into

horizontal stratification (Figure 10B, C). Trough cross-stratification geometries are

observed throughout the sandstone lithofacies, typically with erosive contacts and

incisional relief up to 0.4 m (Figure 10A). Pebble lags commonly define the bases of

27

cross-stratified beds (Figure 10D), which range from 0.1 to 1.5 m thick and extend

laterally for 5-20 m. Most of the remaining basal contacts are commonly sharp and

nonerosive (Figure 10B), although gradational contacts with conglomerate facies

associations G1 are typically within tabular upsection-fining intervals that are 0.8–6 m

thick (Figure 10A, B, C, D).

Interpretation

Facies association S2 is interpreted as sandstone channel and bartop deposits

(Nemec and Steel, 1984). Trough stratification represents migrating three dimensional

dunes (Reading, 1996), which would likely developed during higher stage flows in the

fluvial system (Miall, 1996). The horizontally stratified sandstones are interpreted as

channel-fill deposits, most likely deposited in the upper levels of the channels under

upper flow regime conditions (Stear, 1985; Reading, 1996). The low angle tabular cross-

stratified sandstones are interpreted as two-dimensional dunes or simple bars transitional

into upper plane bed conditions (Reading, 1996). Facies association G1 is commonly

interbedded with S2 deposits, which principally represent sandy channel deposits

(DeCelles et al., 1991).

G1. Upsection fining, cross-stratified, pebble conglomerate with interbedded

sandstones

Description

Facies association G1 is principally composed of well-sorted, clast-supported,

pebble conglomerates (~80%) with interbedded sandstones lenses (~20%). Conglomerate

beds have lenticular shapes, internal trough stratification, and extend laterally for 10–20

m (Figure 10A, C). Stratification is crudely defined by changes in clast size, erosional

contacts, and scour surfaces (Figure 10A, D). Individual beds range in thickness from

28

0.2–3 m, although intervals stacked intervals up to 20 m thick make differentiation of

individual beds difficult (Figure 10B, C). The conglomeratic matrix is primarily

medium-grained sandstone, with clast rich zones and imbrication common in scours

(Figure 10A, D). Interbedded sandstones lenses are composed of medium- to coarse-

grained, subangular sandstones that help define crude trough stratification in the

conglomeratic intervals (Figure 10A). These lenses range from 0.1–0.6 m thick, extend

laterally from 1–20 m, and are interspersed throughout conglomeratic packages up to 20

m thick. Basal bed contacts are erosive with incisional relief typically around 0.5 m for

conglomerates and 0.1 m for sandstones (Figure 10A, C). Weak imbrication of clasts

occurs to some degree in the basal portion of trough structures. Commonly associated

with the G1 facies association are sandstones beds of the S2 sandstone facies association,

which collectively define gradational upsection-fining packages 1–4 m thick.

Interpretation

Facies association G1 is interpreted to have sedimentary features characteristic of

fluvial gravels deposited in a distributary fluvial system (Nemec and Steel, 1984; Kelly

and Olson, 1993; Miall, 1996; Reading, 1996). The upsection-fining cycles observed

within this facies association were likely generated by the lateral migration of channels

accompanied by deposition on inner channels and aggradation of abandon channel

reaches (Rust, 1972; Nemec and Steel, 1984; Miall, 1996). Alternatively, these packages

also occur due to a progressive decrease in discharge through time and the subsequent

backfilling of channelized areas (Reading, 1996; Miall, 1996). The thin sandstone lenses

throughout the G1 packages interpreted to represent deposition within channels during

low flow stages (Miall, 1996).

29

Figure 10. Photographs of distributary fluvial facies associations S2 and G1 from upper Río Grande Formation. (A) Interbedded trough cross-stratified sandstones and pebble conglomerates. (B) Structureless sandstones (S1) overlain by stratified conglomerates (G1). (C) Transitional from fluvial trough cross-stratified sandstones and conglomerates into overlying alluvial fan lithofacies. (D) Horizontally stratified sandstones defined by pebble stringers.

G2. Horizontally stratified pebble‒cobble conglomerate with interbedded sandstone

Description

Facies association G2 is characterized by a horizontally stratified, moderately

sorted, clast-supported, pebble‒cobble conglomerates (~90%) with interbedded

sandstones (~10%). Conglomerate beds are typically tabular to broadly lens shaped, with

distinct zones dominated by pebbles or cobbles (Figure 11A, D, E), which define

horizontal stratification. Thicknesses of individual conglomerate beds range from 0.2 to

30

1.5 m, although intervals of stacked beds may reach up to 80 m in thickness, making

identification of discrete beds difficult (Figure 11D). Conglomerate beds typically persist

laterally up to 30 m in outcrop. The matrix of these clast-supported conglomerates

consists of fine- to medium-grained sandstone (Figure 11E). Interbedded sandstone

lenses are composed of poorly sorted, medium- to very coarse-grained sandstones, and

contain crude trough cross-stratification with incision into the underlying conglomerate

beds (Figure 11A). These lenses extend laterally from 2–15 m, are typically 0.2–1.5 m

thick, and are commonly interspersed throughout the conglomerate intervals. The basal

contacts of the conglomerate beds are sharp to slightly erosional with incisional relief up

to 0.3 m, while interbedded sandstone scours show slight erosion with incisional relief up

to 0.5 m (Figure 11A, D).

Interpretation

The G2 facies association is interpreted as ephemeral sheetflows in a proximal

alluvial fan environment (Nemec and Steel, 1984; Miall, 1996). The conglomeratic

deposits show typical features of poorly confined sheetflows in very shallow channels

containing low‒relief longitudinal bars (Nemec and Steel, 1984; Hartley, 1993; Miall,

1996). These features include horizontal stratification, slight imbrication, moderate

sorting, and sharp basal to slightly erosive contacts. Interbedded sandstone lenses with

trough geometries are interpreted to represent late stage sheetflows and small stream flow

conditions on an alluvial fan, with localized incision into underlying sheetflow deposits

(Nemec and Steel, 1984; Kelly and Olson, 1993; Miall, 1996).

G3. Structureless, laterally extensive pebble to boulder conglomerate with interbedded

sandstone

31

Description

The G3 facies association is characterized by poorly sorted, clast- and matrix-

supported, cobble‒boulder conglomerates (~90%) with interbedded sandstones lenses

(~10%). Conglomerate beds are structureless, lacking internal sedimentary structures to

define stratification (Figure 11B, D). Thicknesses of individual conglomerate beds range

from 0.2‒4 m and extend laterally from 10‒50 m. Large intervals of stacked

conglomerate beds occur in packages >100 m thick, making identification of individual

conglomerate beds difficult (Figure 11B). Interbedded sandstone lenses allow for

discrimination of individual conglomerate beds (Figure 11A). The sandstone lenses are

moderately sorted, coarse- to very coarse-grained, trough cross-stratified and define bed

boundaries within conglomerate rich intervals. Sandstones range from 0.2‒ 1.5 m thick,

persist laterally for 2‒15 m, and are interspersed throughout the G3 conglomerates,

although a decrease in the proportion of sandstone occurs upsection in the Pisungo

Formation. Basal contacts within conglomerate packages are sharp and nonerosive,

although interbedded sandstone troughs show minor erosion with incisional relief up to

0.5 m

Interpretation

Facies G3 is interpreted to represent unconfined hyperconcentrated flood flows

(Smith, 1986; Miall, 1996), consistent with the extensive sheet geometries, poor sorting,

lack of internal structure, sharp basal contacts, and mixed clast- and matrix-supported

beds. Hyperconcentrated flows are transitional between normal stream flows and debris

flows (Smith, 1986) and are characteristic of ephemeral discharge by sediment gravity

flows in a semiarid alluvial fan environment (Flint and Turner, 1988; Hartley, 1993;

Miall, 1996). Interbedded sandstone lenses with scour surfaces are interpreted to

32

represent late-stage flood flow or stream flow on an alluvial fan (Nemec and Steel, 1984;

Kelly and Olson, 1993; Miall, 1996).

33

Figure 11. Photographs of conglomeratic alluvial fan facies associations G2 and G3 of the Pisungo Formation. (A) Laterally extensive (15-20 m) horizontally stratified pebble-cobble conglomerates (Gh) incised by trough cross-stratified sandstone lenses (St). (B) Structureless, clast- and matrix-supported, poorly sorted, pebble–boulder conglomerates (Gd). (C) Imbricated, horizontally stratified pebble conglomerate (Gh). (D) Horizontally stratified (Gco) deposits overlain by structureless hyperconcentrated flow deposits (Gd). (E) Poorly sorted, boulder to cobble, fining upsection ephemeral sheetflood conglomerates.

34

40AR/39AR GEOCHRONOLOGY

40Ar/39Ar geochronological results from interbedded ash-fall tuffs provide

constraints of the depositional age on the upper Río Grande Formation (Table 3). Field

samples of tuff horizons were collected by David Gingrich and Dr. Brian K. Horton.

Total fusion laser 40Ar/39Ar analyses were performed on five samples containing

separated sanidine and biotite grains at the New Mexico Geochronology Research

Laboratory. Weighted mean ages and 2σ errors are calculated for each sample and are

reported in Table 3.

The five samples collected for 40Ar/39Ar analyses are from the 2591–4781 m

levels in the Río Grande Formation (Figure 8). All five samples were collected from ash-

fall tuff beds with a modest degree of reworking. The lowest ash-fall sample dated

(RA793) has a weighted mean age of 16.31 ± 0.6 Ma (Table 3), while the youngest dated

tuff (RB2033) has a weighted mean age of 9.69 ± 0.05 (Table 3). From these results, we

calculate average sediment accumulation rates for the Río Grande Formaion.

Accumulation rates in the lowest sampling intervals (lower to middle Río Grande

Formation) have an average rate of 273 m/Myr, whereas the higher levels (upper Río

Grande Formation) show an increase to 577 m/Myr. These new 40Ar/39Ar results span

from early to late Miocene and constrain the uppermost Río Grande Formation to

Miocene age. Assuming uniform accumulation rates, the Pisungo Formation is defined

as late Miocene age.

35

Table 3. 40Ar/39Ar data for interbedded tuffs within Río Grande Formation Sample Level (m) Mineral Age (Ma) ± 2σ (Ma) Lithology n MSWD RB2033 4781 Sanidine 9.69 0.05 tuff 13 1.3 RB1077 3825 Sanidine 11.35 0.03 tuff 9 0.7 RB735 3483 Biotite 12.95 0.22 tuff 22 1.2 RB335 3103 Biotite 13.38 0.25 tuff 11 2.3 RA793 2591 Biotite 16.31 0.60 tuff 20 2

n = number of grains analyzed. MSWD = mean square of weighted deviates.

36

Chapter 4. Depositional systems

Clastic sedimentological analyses of the Miocene upper Río Grande and upper

Miocene Pisungo formations in the Cianzo basin reveal an upsection coarsening

succession with facies associations representative of braided fluvial, distributary fluvial

megafans, and alluvial fan processes evolving progressively from distal to proximal

settings (Figure 12).

The sandstone S1 facies associations is interpreted as deposits of

hyperconcentrated sandy sheetflows, consistent with the structureless nature of beds, lack

of channelization, sharp basal contacts, and common association with thick, capping

structureless mudstones (F1) commonly observed in these environments (Steel and

Aasheim, 1978; Hartley, 1993; Kelly and Olsen, 1993; Miall, 1996; Hampton and

Horton, 2007). The associated mudstone F1 facies association is interpreted as

overbank/floodplain deposits in a braided fluvial system, based on characteristic

observations including large bed thickness, structureless to laminated structures, laterally

extensive deposits, non-erosive contacts, and common association with S1 deposits,

completing an overall upsection-fining sequence (Miall, 1996; Hampton and Horton,

2007). These deposystems are interpreted to represent relatively more distal

environments than facies associations in the upper Río Grande and Pisungo Formations

(Figure 12A).

The onset of coarser-grained deposition (G1, S2) and lack of finer grained facies

(F1, S1) in the transitional upper Río Grande Formation may be considered evidence for

the development of proximal sediment sources (Figure 12B). G1 conglomeratic deposits

of the upper Río Grande Formation are interpreted as distributary fluvial channel

systems, consistent with the well-sorted texture, clast imbrication, erosive bed contacts,

37

limited lateral continuity, and trough cross-stratification commonly observed in these

depositional systems (Nemec and Steel, 1984; Miall, 1996; Reading, 1996). The S2

sandstones are interpreted as waning-stage deposition in channel and bartop

environments, consistent with trough cross-stratification, absence of mudstone, and

common association with conglomeratic facies in upsection-fining sequences (DeCelles

et al., 1991; Reading, 1996).

The Miocene upper Río Grande Formation is interpreted to record the progression

of depositional systems from braided fluvial to more proximal settings distributary fluvial

systems (Figure 12A, B) (Kelly and Olsen, 1993; Hampton and Horton, 2007;

Weissmann et al., 2010). The association of upper flow regime sheetflood sandstones

and overbank mudstones characterizing the lower Río Grande Formation (Figure 12A)

are contrasted with the channelized sandstones and conglomerates of a distributary fluvial

system in the upper Río Grande Formation (Figure 12B). This transition is recorded by

an upsection increase in grain size and change in facies associations characterized by

interbedded sandy hyperconcentrated sheetflows (S1) and broad distributary fluvial

system channels (S2, G1) with overbank mudstones (F1). The stratigraphic shift in the

Río Grande Formation illustrates the transition from distal to proximal depositional

environments (Steel and Aasheim, 1978; Hubert and Hyde, 1982; Kelly and Olsen, 1993)

similar to the distributary fluvial megafans in the modern Andean foreland basin (Horton

and DeCelles, 2001; Uba et al., 2005; Hampton and Horton, 2007; Weissmann et al.,

2010). The six main facies associations (F1, S1, S2, G1, G2, G3) are interpreted on the

basis of grain size, sedimentary structures, basal bed contacts, bed thickness and

continuity, and lateral and stratigraphic stacking patterns (Table 1, 2).

The coarse-grained upper Miocene Pisungo Formation is interpreted to represent

deposition in an alluvial fan environment characterized by conglomeratic

38

hyperconcentrated flows (G3) and ephemeral sheetflows (G2) (e.g., Nemec and Steel,

1984; DeCelles et al., 1991; Hartley, 1993; Blair and McPherson, 1994; Miall, 1996).

Supporting evidence for this interpretation and differentiation between the G2 and G3

facies associations are based on sorting, bed thickness, basal contacts, and sedimentary

structures documented in the measured stratigraphic section (Figure 8). The G3

conglomerates of the Pisungo Formation are interpreted as unconfined hyperconcentrated

flows, consistent with extensive sheet-like bedding geometries, sharp basal contacts, poor

sorting, and structureless character (Flint and Turner, 1988; Hartley, 1993; Miall, 1996).

The G2 conglomerates are attributed to ephemeral sheetflows, with characteristic

horizontal stratification, minor clast imbrication, erosive basal contacts, and interbedded

sandstone scours (Nemec and Steel, 1984; Miall, 1996). Both the G2 and G3

conglomeratic deposits are interbedded throughout the Pisungo Formation and are

interpreted as proximal alluvial fan environments (Figure 12C). Supporting evidence for

this broader interpretation come from the proximity to major fold-thrust structures

(Figure 5) with growth strata in the upper Pisungo Formation demonstrating

contemporaneous deformation (Figure 6).

39

Figure 12. Schematic block diagrams showing distal to proximal evolution of Cianzo basin. (A) Lower Río Grande Formation: distal braided fluvial system derived from western source areas. (B) Upper Río Grande Formation: proximal distributary fluvial system. (C) Pisungo Formation: proximal alluvial fan complexes, with growth strata recording syntectonic deposition along the Hornocal fault (Fig. 6).

40

Chapter 5. Provenance

SANDSTONE COMPOSITIONS

Methods

In order to assess the sandstone framework compositions of Cenozoic fill in the

Cianzo basin, 31 medium-grained sandstone samples were collected throughout the Casa

Grande, Río Grande, and Pisungo formations for petrographic analysis. Thin section

construction and staining for potassium and calcium feldspar was completed for each

sample. Injection of blue dye epoxy assisted recognition of grain dissolution versus

original primary pore space within the Río Grande sandstone samples. Point counts of

450 grains per thin section were conducted according to the Gazzi-Dickison method

(Gazzi, 1966; Dickinson, 1970, 1983, 1985; Dickinson and Suzeck, 1979; Ingersoll et

al., 1984). All framework sand grains (>0.0625 mm) were categorized using parameters

defined for this study (Table 4).

41

Table 4. Parameters for sandstone point counts Symbol Description

Qm Monocrystalline quartz Qp Polycrystalline quartz Qpf Foliated polycrystalline quartz Qms Monocrystalline quartz within a sandstone/quartzite lithic grain

Q Total quartz with chert (Qm+Qp+Qpf+Qms+Lch) Qf Total quartz (Qm+Qp+Qpf+Qms) (Folk, 1980) K Potassium feldspar P Plagioclase feldspar F Total feldspar (K+P) Ff Total feldspar fragments (K+P+Lmg+Lvf) (Folk, 1980)

Lsc Carbonate sedimentary lithic fragment Lss Siltstone sedimentary lithic fragment Lch Chert sedimentary lithic fragment Lsm Mudstone/shale sedimentary lithic fragment Ls Total sedimentary lithics (Lsc+Lss+Lch+Lsm+Qms)

Lmp Phyllite metamorphic lithic fragment Lmg Gneiss / metamorphic lithic fragment Lms Schist metamorphic lithic fragment Lm Total metamorphic lithics (Lmp+Lmq+Lms+Qpf) Lvm Mafic volcanic grains Lvf Felsic volcanic grains Lvl Lathwork volcanic grains Lv L

Total volcanic lithic fragments (Lvf+Lvl) Total lithics (Ls+Lm+Lv)

Lt Total polycrystalline lithic fragments (Ls+Lm+Lv+Qp) Lf Total lithic fragments (Lsc+Lss+Lsm+Lmp+Lms+Lvl) (Folk, 1980)

Accessory minerals included biotite, muscovite, amphibole, sphene, and hematite

Results

Sandstone point-count results for all 31 samples are presented in four ternary

diagrams arranged in stratigraphic order (Figure 13). Each diagram depicts a different

framework grain ratio on the basis of defined point-count parameters (Table 4): (A) Qf-

42

Ff-Lf (total quartz-feldspar-lithic fragments; Folk, 1980); (B) Q-F-L (Dickinson, 1983);

(C) Qm-F-Lt (monocrystalline quartz-feldspar-lithic fragments); (D) Lm-Ls-Lv

(metamorphic-sedimentary-volcanic lithic fragments). Grains of monocrystalline quartz

(Qm) and polycrystalline quartz (Qp) are abundant throughout all sampled intervals.

Sedimentary lithic fragments of siltstone and mudstone (Lss, Lsm), metamorphic lithic

fragments of phyllite and schist (Lmp, Lms), and plagioclase and potassium feldspars (P,

K) exhibit upsection trends within the Cianzo stratigraphic section. Volcanic lithic

fragments (Lvl, Lvf), carbonate lithic fragments (Lsc), and chert (Lch) grains are

exceedingly rare throughout the samples. Observed accessory minerals include biotite,

muscovite, amphibole, sphene, and hematite. Secondary porosity and grain replacement

within the sandstone samples are only minor constituents, which implies that the original

detrital assemblage is relatively well-preserved.

The Casa Grande Formation consists of well-sorted, medium-grained sandstones,

with calcite cement and a mean composition of Q84F5L11. Compositions range from

quartzarenite in the lowest stratigraphic levels, subarkose in the lower to middle section

and dominantly sublitharenite in the uppermost section (Figure 13A). The dominant

constituent (up to 73%) is monocrystalline quartz (Qm), followed by polycrystalline

quartz (Qp). Feldspar grains comprise up to ~10% of the modal composition of Casa

Grande sandstones, the highest proportion among all formations. Lithic fragments

comprise only 1-2% in lower stratigraphic levels, but increase upsection in the uppermost

Casa Grande Formation to ~25% (at the expense of diminishing Qm proportions).

Moderately to well-sorted, medium-grained sandstones of the overlying Río

Grande Formation represent sublitharenites compositions in lower stratigraphic levels

and litharenite in the uppermost levels, defining an upsection trend toward more lithic-

rich compositions (Figure 13A) with a mean composition of Q70F3L27. The lower Río

43

Grande samples are sublitharenites with Qm as the main constituent and relatively high

proportions of feldspar (~8%) and volcanic lithics (up to 5%). In contrast, the upper Río

Grande Formation samples are litharenites, with Qm as the main constituent, but with

reduced feldspar and volcanic lithic fragments (~1% combined) and increased

sedimentary and metamorphic lithic fragments (~31% combined).

Samples of sandstones lenses in the conglomeratic Pisungo Formation are

classified as litharenites (Figure 13A), continuing the broad upsection trend toward

increasingly lithic compositions from the underlying Río Grande Formation and have a

mean composition of Q64F1L35. In the Pisungo Formation, Qm remains the largest

component (~50% of modal composition), with lithic fragments constituting 48% and

feldspars the remaining 2%. Additionally, within this trend, an upsection increase in the

proportion of Ls grains is observed, from ~16% in the Río Grande Formation to ~23% in

the Pisungo Formation.

Overall, a composite trend of increasing lithic fragments is observed in the Cianzo

basin-fill succession, from 1-2% in the Casa Grande Formation to 48% in the Pisungo

Formation. Additionally, monocrystalline quartz (Qm) decreases from 73% in the lower

levels to 50% in the upper levels of the basin.

44

Figure 13. (A) Qt-Ft-Lt (with 50% quartz baseline), (B) Q-F-L, (C) Qm-F-L, and (D) Lm-Ls-Lv sandstone ternary diagrams for the Casa Grande Formation (8 samples), Río Grande Formation (14 samples), and Pisungo Formation (7 samples). Gray arrows show upsection increase in total lithic (Lt, L) and sedimentary lithic (Ls) framework grains.

Interpretation

Sandstones at the base of the Casa Grande formation have the highest proportions

of monocrystalline quartz (Qm) and relatively low amounts of lithic and feldspar

fragments, suggesting quartz-rich recycled orogen provenance (Figure 13B, C) (e.g.,

Dickinson, 1983). An upsection decrease in Qm and an increase in sedimentary and

metamorphic lithic fragments (Ls, Lm) is consistent with derivation from a fold-thrust

45

belt (Dickinson, 1985). Volcanic lithic fragments (Lv) and feldspar (F) framework grains

are at the highest observed percentages (up to 5% and 10% respectively) in the Casa

Grande and basal Río Grande formations. When these data are considered in the context

of east-directed paleocurrents (Figure 8), the Casa Grande and lower Río Grande

formations are likely correlated with western sediment sources such as the Andean

magmatic arc with potentially greater contributions of lithic volcanic fragments. The

proportions of sedimentary and metamorphic lithic fragments increase upsection

throughout Casa Grande into the Río Grande. This increase is interpreted to reflect

increasing proximity of sediment sources west of the Cianzo basin in the Puna Plateau

and westernmost Eastern Cordillera.

The Río Grande sandstones show a continued upsection increase in sedimentary

and metamorphic lithic fragments (Ls, Lm)(Figure 13D) and decrease in monocrystalline

quartz (Qm) suggesting a transitional recycled orogen provenance (Figure 13B, C)

(Dickinson, 1983). Sandstone compositions for the upper Río Grande Formation and

overlying Pisungo Formation show a reduction in the feldspathic (F) and volcanic lithic

components (Lv) relative to the Casa Grande Formation. This can be interpreted as

elimination of distal western sediment sources with greater amounts of magmatic-arc

materials. Additional support for this interpretation comes from the increasing proportion

of sedimentary and metamorphic lithic fragments (Figure 13D). Such modal

compositions likely reflect the lithologies of more proximal source terranes, with

sedimentary and metamorphic lithic fragments potentially derived from the most

extensive units: the metasedimentary Precambrian-Cambrian Puncoviscana formation

and younger sedimentary rocks of the Ordovician Santa Victoria Group and Cretaceous

Salta Group.

46

The sandstones within the Pisungo formation continue the trends observed in the

Río Grande Formation, with an increase in Ls, at the expense of Qm, consistent with a

transitional recycled orogen provenance (Figure 13B, C) (Dickinson, 1983). Increase of

Ls could be attributed to (Figure 13D) local derivation of sedimentary lithic fragments,

due to the close proximity of Cretaceous Salta Group strata in the hangingwall of the

Hornocal fault (Figures 3 and 5). Evidence supporting this interpretation comes from the

Pisungo growth strata demonstrating syndepositional displacement along the fault (Figure

6).

CONGLOMERATE CLAST COUNTS

Methods

Conglomerate clast compositional data were collected at 34 different sites within

the Río Grande and Pisungo formations (Figure 14). Measurements were conducted

using approximately 30 by 30 cm grids, with a minimum of 100 clasts counted.

Although most clasts cannot be identified at the formation level, many can be attributed

to major stratigraphic levels of the region. Cambrian strata (Є) are characterized by

green to brown quartzites, as well as metasedimentary siltstones and phyllites. The

Ordovician stratigraphic section (O) is illustrated by tan to beige, mudstones and

quartzites. Although only a small percentage of the total clasts are from the

Carboniferous section (C), they are distinguished by characteristic black and white

speckled “salt and pepper” quartzites. Cretaceous strata (K) of the Salta Group are

composed of red, maroon quartzites, sandstones, and mudstones. The youngest clasts are

sourced from the Eocene Santa Bárbara Subgroup (P), as represented by distinct purple to

violet medium-grained sandstones that with heavy bioturbation.

47

Figure 14. Conglomerate clast composition data from the Río Grande and Pisungo formations based on >100 clasts counted per station (see Fig. 8 for location).

Results and interpretations

The conglomerate clast data accurately reflect the composition and exhumation

patterns in the sediment source areas. The Río Grande Formation is divided into two

48

compositional categories contrasting the lower and upper levels of the Río Grande

Formation (Figure 14). The principal clasts composing lower Río Grande conglomerates

are Є5O85C0K9 P1, whereas conglomerates of the upper Río Grande Formation are

composed of Є37O28C2K30P3. The significant upsection increase in the relative proportion

of Cambrian (Є) and Cretaceous (K) clasts and decrease in Ordovician (O) clasts are

attributed to reactivation of the Hornocal fault (Cretaceous sources) and initiation of the

Cianzo thrust (Cambrian sources), further suggesting proximal depositional environments

related to fault displacement and increased clast contributions from the uplifted source

areas (Figure 14).

The Pisungo Formation is dominantly composed of pebble to boulder clasts and

can be separated into two compositional categories based on subtle changes in clast

compositions. The lower Pisungo Formation is characterized by Є37O22C3K38P0. The

upper Pisungo Formation is principally composed of Є39O15C1K44P0. The lower Pisungo

Formation clast counts are relatively similar to that of the upper Río Grande. However,

the upper Pisungo clast counts appear to show a slight increase in the relative proportion

of Cretaceous clasts (Figure 14), possibly due to the extremely close proximity of uplifted

source along the Hornocal fault. The diminishing Ordovician clasts throughout the Río

Grande and Pisungo formations most likely represents exhumation of Ordovician strata

from the hangingwall of the Cianzo thrust, which ultimately led to widespread exposure

of the Cambrian section.

DETRITAL ZIRCON U-PB GEOCHRONOLOGY

Methods

49

Four medium- to coarse-grained sandstone samples were collected in the Cianzo

basin-fill succession from the Paleocene Mealla Formation (Santa Bárbara Group), upper

Eocene–Oligocene Casa Grande Formation, Miocene upper Río Grande Formation, and

the upper Miocene Pisungo Formation, with one sample coming from each formation.

Heavy-liquid separation of zircon grains from sandstones was conducted at the

University of Texas at Austin following standard procedures (Gehrels, 2000; Grehels et

al., 2008). U-Pb geochronological analyses were conducted at the University of Arizona

LaserChron Center using laser-ablation-multi-collector inductively coupled plasma-mass-

spectrometry (LA-MC-ICPMS) following the procedures described by Gehrels et al.

(2000, 2006).

For each sample, approximately 120 individual zircon grains were randomly

selected and analyzed, although cracked grains or those with inclusions were avoided. In

order to correct for inter- and intra- element fractionation, fragments of a large zircon

crystal from Sri Lanka with a known age of 564 ± 4 Ma (2σ error) were analyzed

approximately every fifth measurement (Gehrels et al., 2008). Calibration correction

during the analysis typically resulted in an uncertainty of 1-2% (2σ error) for both 206Pb/207Pb and 206Pb/238U ages. Gehrels et al. (2008) provide further details on the

procedures and operating conditions. Accuracy of 206Pb/238U ages is generally greater for

zircon ages less than 1000 Ma whereas 206Pb/207Pb ages are more precise for zircon ages

over 1000 Ma; therefore, 1000 Ma represents the cutoff for the respective U-Pb analysis

ages (Gehrels et al., 2008). Analyses that yielded >10% uncertainty, >30% discordance,

or >5% reverse discordance were discarded from further consideration.

Reported here are a total of 388 detrital zircon U-Pb ages from four sandstone

samples (Figure 15). In addition, 504 detrital zircon U-Pb ages from six samples

(Cambrian Puncoviscana Formation, Cambrian Mesón Group, Carboniferous Las Peñas

50

Formation, Jurassic Tacuru Group, and two Cretaceous Pirgua Subgroup samples)

previously analyzed by McBride (2008) are reported in order to enable more robust

comparisons of potential Paleozoic and Mesozoic sources (Figure 15) following similar

procedures at the same laboratory. These analyses are plotted as age histograms and

relative age-probability curves (Figure 15), which show each age and its uncertainty as a

normal distribution, summing all ages and uncertainties from each sample into a single

age-distribution curve. Individual Age peaks are considered to be significant where

defined by 3 or more analyses (Dickinson and Gehrels, 2008).

51

Figure 15. Detrital zircon U-Pb age distributions for sandstones of the Cianzo basin showing relative age probability plots (black lines) and age histograms (gray bars) arranged in stratigraphic order. Samples are arranged in stratigraphic order, with Cenozoic samples analyzed in this study depicted in the upper 4 plots and 8 additional Mesozoic samples analyzed by McBride (2008) plotted below.

52

Interpretation

Detrital zircon U-Pb age data from the four Paleocene to upper Miocene

sandstones from the Cianzo basin identify source signatures in the geochronological

record of the central Andes. Northern Argentina is dominated by four main zones with

different tectonomagmatic histories (Figure 2). (1) The Mesoproterozoic (1200 - 1000

Ma) Sunsás–Grenville event is best expressed by the Arequipa-Antofalla block and

detrital signature in Neoproterozoic – Cambrian metasedimentary rocks (Finney et al.,

2003; Ramos 2008). (2) The Proterozoic – Paleozoic (~570 to 520 Ma) Pampean event is

characterized by assemblages within the Eastern Cordillera, Santa Bárbara, and

Subandean zones (Rapela et al., 1998; Finney et al., 2003; Loewy et al., 2004). (3) The

Ordovician (~500 Ma to 435 Ma) Famatinian arc signature is best expressed by both

sediments derived from a clastic platform deposited in a basin located between the

Antofalla block and the Pampia craton, (Rapela et al., 1998; Ramos, 2009), as well as

magmatic inputs from the Faja Eruptiva, a series of volcanic and plutonic arc rocks with

published ages of 467 to 476 Ma (Coira et al., 1999). (4) The Permian (305 to 267 Ma)

signature is characterized by metamorphic rocks comprising part of the basement of the

Precordillera of northern Chile (Hervé et al., 1985; Ramos, 2008). Other potential

sources include the Cretaceous–Cenozoic Andean magmatic belt. New U-Pb ages over a

6000 m interval in the Ciano basin show important upsection variations in source signals

(Figure 15).

Detrital zircon U-Pb analyses performed by McBride, 2008, allow us to

characterize local source signatures and can be separated into 3 distinct groups. (1) the

Precambrian – Cambrian Puncoviscana and Cambrian Mesón (Figure 15A, B) show

significant Sunsás-Grenville signatures (1200 – 1000 Ma), as well as Pampean (570 –

520 Ma) age signatures. (2) The Carboniferous Las Peñas Formation (Figure 15C) is

53

characterized by Sunsás-Grenville, Pampean, and Famatinian (500 – 435 Ma) age peaks.

(3) The Jurassic Tacuru Group and Cretaceous Pirgua Subgroup (Figure 15D, E, F)

express age populations related to Sunsás-Grenville and Pampean events.

The Paleocene Mealla Formation (Santa Bárbara Group) has prominent age peaks

at 278, 498, 546, 604, and 1036 Ma (Figure 15G). The Permian age peak at ~278 Ma

indicates a distinct change in sedimentation source in the Cianzo basin. The absence of

known source rocks with this diagnostic Permian signal east of the Western Cordillera

along with east-directed paleocurrents suggest that the sediments carrying this signal are

derived from far western sources. The nearest possible source rocks include the Western

Cordillera of northern Chile, which has numerous isotopic (mostly K/Ar) ages ranging

from ~305 to ~267 Ma (Hervé et al., 1985; Ramos, 2008) and the metamorphic basement

of the Chilean Precordillera with a reported U-Pb age of ~270 Ma (Lucassen et al., 1999).

The distinct age peak at 498 Ma shows a Famatinian arc source (500-435 Ma) which

appears to be restricted to a narrow N-trending belt in the Puna plateau west of the

Cianzo basin (Ramos, 2008). Finally, the increase in the magnitude of Sunsás-Grenville

age peaks suggests greater contributions from Mesoproterozoic basement such as the

Antofalla block of northern Chile and northwestern Argentina.

The upper Eocene – Oligocene Casa Grande Formation records a continuance of

several key provenance signals, such as the Permian (~260 Ma) and Ordovician –

Famatinian (478 Ma) age populations (Figure 15H). The presence of Paleozoic and older

ages (533, 590, 647, and 1050 Ma) suggests a composite provenance signal (Figure 15H)

reflecting the mixing of two or more sources, potentially correlating with continued

sedimentary recycling of the Cambrian Puncoviscana Formation and Mesón Group

(Figure 15A, B). Significantly, all subsequent formations lack the ~260 Ma age peaks and

show a much reduced Sunsás-Grenville age population, indicating unique sources most

54

active during deposition of the Santa Bárbara Subgroup and Casa Grande Formation.

This implies that the Cianzo basin was potentially part of a regionally extensive basin

during Paleocene–Oligocene time that received significant sediment from western source

regions.

A significant age peak for Famatinian cycle input at 468 Ma occurs in the

Miocene upper Río Grande Formation (Figure 15I), likely derived from Famatinian arc

rocks to the west. In addition, the Río Grande Formation also has age peaks at 528, 590,

618, 642, 758, and 1046 Ma, reflecting continued erosion and recycling of the Cambrian

Puncoviscana and Mesón formations (Figure 15A, B).

The upper Miocene Pisungo Formation shows age peaks at 525, 614, 721, 1058,

1233, and 2072 Ma (Figure 15J). This age spectrum shows no Famatinian (Ordovician)

or younger age peaks. We interpret this attribute to isolation of the Cianzo basin from

external sources of sediment due to continued thrusting, uplift, and erosion in the Eastern

Cordillera. The age peak distributions are likely the product of source material shed

directly off of uplifted Cambrian Puncoviscana Formation (Figure 15A) and Salta Group

sources (Figure 15 E, F) along the basin margins related to the Hornocal fault and Cianzo

thrust.

55

Chapter 6. Basin reconstruction and discussion

We propose time-slice reconstructions of Cenozoic basin evolution and associated

deformation for the Cianzo basin and surrounding regions on the basis of lithofacies

assemblages, structural relationships, paleocurrents, conglomerate and sandstone

compositions, and detrital zircon U-Pb age signatures.

SANTA BÁRBARA SUBGROUP

The Santa Bárbara Subgroup is composed of fine-grained sandstones, siltstones,

mudstones, and pervasive paleosols that were regionally deposited in high-sinuosity to

braided fluvial settings, as well as lacustrine environments ranging from shallow mudflats

to open perennial basins (Marquillas et al., 2005). Deposition was likely in either a

thermally subsiding postrift basin with very low subsidence rates (Salfity and Marquillas,

1994; Marquillas et al., 2005) or a distal foreland basin (Horton and DeCelles, 1997;

DeCelles and Horton, 2003). Measured sections reveal a thickness of ~400 m, with

paleocurrents indicating east-directed flow (Figure 8). Detrital zircon U-Pb age peaks (n

≥ 3 grains) show significant populations at 278, 498, 550-600, and 1036 Ma, correlating

to the Permian, Famatinian, Pampean, and Sunsás sources, respectively (Figure 15G). In

comparison to underlying strata, the appearance of 278 and ~500 Ma age peaks and

relative increase in ~1050 Ma populations require major modifications to the drainage

region providing sediment to the Cianzo basin. These results have implications for

defining the margins of the original depositional basin. First, Paleozoic magmatic arc

sources are absent east of the Western Cordillera, with the nearest possible sources in

northern Chile (Coira et al., 1982), requiring a western source. Second, the onset of an

Ordovician (Famatinian) age peak and large relative increase in Mesoproterozoic

(Sunsás) age peaks indicate new and enhanced contributions from western sources,

56

particularly the Antofalla block of northern Chile and the Famatinian arc in the Puna

plateau. Collectively, these facies relationships, sediment dispersal patterns, and U-Pb

age distributions are interpreted as marking early Andean thrusting and foreland basin

evolution in northern Argentina.

CASA GRANDE FORMATION

Upper Eocene–Oligocene fine-grained sandstones and mudstones of the Casa

Grande Formation were deposited in distal braided fluvial settings (Boll and Hernández,

1986). Casa Grande paleocurrents in the Cianzo study region indicate primarily ENE-

directed transport of sediments from western sources. Additionally, sandstone

compositions show the highest observed proportions of feldspar and volcanic lithic

framework grains, possibly related to western magmatic-arc sources (Figure 13). Finally,

the U-Pb signatures show prominent Permian, Famatinian, Pampean, and Sunsás-

Grenville age populations at 260, 478, 533, 590, 647, and 1050 Ma, similar to the Santa

Bárbara Subgroup. However, the enhanced proportions of Permian and Mesoproterozoic

age peaks suggest greater contributions from sources along the Chile – Argentina border.

These combined results suggest that the Cianzo basin formed part of a larger

basin during the Eocene, a basin that persisted westward across the Puna to the Western

Cordillera the Chile–Argentina border, and included subbasins such as the Tres Cruces

and Humahuaca basin (Figure 16A)(Boll and Hernández, 1986; Coutand et al., 2001).

Correlation of the Geste, Quebrada de los Colorados, Casa Grande and upper levels of the

Lumbrera Formations suggests lithostratigraphic equivalence among Eocene–Oligocene

sedimentary units of the Puna to western Eastern Cordillera and a potentially integrated

57

regionally extensive basin at this time (Kraemer et al., 1999; Carrapa and DeCelles,

2008).

RÍO GRANDE FORMATION

Upper Oligocene – Miocene deposition of the >3000 m thick Río Grande

Formation (facies association F1, S1, S2, G1) occurred in broad distributary fluvial

(megafan) systems that recorded increasing proximity of deposition from lower to upper

sections (Figures 8 and 12). Río Grande Formation paleocurrents show ENE-directed

flow, with conglomerate clast compositions in the upper Río Grande Formation revealing

a dramatic increase in Cambrian and Cretaceous clasts, and at the expense of Ordovician

clasts (Figure 14). Río Grande sandstones record an upsection decrease in the relative

proportions of feldspar and volcanic lithic fragments, and increase in sedimentary and

metamorphic lithic content (Figure 13), suggesting reduced input from the magmatic arc.

Finally, the Río Grande Formation detrital zircon U-Pb age populations show the

disappearance of the ~260 Ma peak characterizing the Casa Grande, whereas the

Famatinian arc signal at 468 Ma is retained (Figure 15).

We attribute changing provenance signatures in the Río Grande Formation to

reduced input from western (magmatic arc and basement) sources and increased

contributions from growing topography induced by fold-thrust deformation in the Puna to

westernmost Eastern Cordillera. A ~468 Ma Famatinian arc signal, east directed

paleocurrents, distal facies associations, Ordovician dominated conglomerate

compositions, and feldspathic and volcanic lithic grains suggest a partially connected

basin receiving sediments derived from the west (Figure 16B). Notable changes occur in

the upper Río Grande Formation, with evidence for localized shortening-related uplift

and an approximate middle Miocene activation age of the basin bounding Cianzo thrust,

58

as revealed by the influx and dominance of Cambrian clasts derived from exhumation of

the hangingwall (Figure 16C). Additional evidence for timing of movement on the

Cianzo thrust comes from the 40Ar/39Ar age data (Table 3), which define a significant

increase in sediment accumulation rates, from 273 m/Myr in the lower Río Grande

Formation to 577 m/Myr in the upper Río Grande Formation, correlating with the

upsection trends toward increasingly proximal facies. The loss of the Permian age peak

(~260 Ma) and major reduction in the Sunsás-Grenville (~1050 Ma) ages that are

diagnostic of the Casa Grande Formation (Figure 15) indicates a diminished signal from

the Antofalla block and magmatic arc of northern Chile and westernmost Argentina

(Figure 16B).

PISUNGO

The upper Miocene Pisungo Formation contains ~1600 m of alluvial fan deposits

representing hyperconcentrated flows and ephemeral sheetflood (facies associations G2,

G3)(Nemec and Steel, 1984; Hartley, 1993; Miall, 1996). Conglomerate and sandstone

compositional data (Figures 13 and 14), show increased proportions Cretaceous and

Cambrian clasts as well as a large increase in sedimentary lithic fragments, likely

reflecting local derivation from the Cretaceous–Paleogene Salta Group in the southern

hangingwall block of the Hornocal fault (Figure 3 and 5). Detrital zircon U-Pb age

spectra show; (a) the loss of the Famatinian arc age peaks (500–435 Ma), (b) continued

reduction of Sunsás-Grenville age (1200–1000 Ma), and (c) the dominance of the

Pampean (570–520 Ma) and Sunsás-Grenville orogenic signals.

59

We interpret the shifts in facies and provenance as the closing of the Cianzo basin

to external sources of sediment, due to continued thrust-induced uplift along the Puna

plateau–Eastern Cordillera boundary, including the Cianzo thrust and Hornocal fault

(Figure 16D). Sources for the cobble–boulder conglomerates of Pisungo Formation are

thought to be very locally derived from material eroded directly off the Cianzo thrust

(mostly Cambrian Puncoviscana Formation) and Hornocal fault (mostly Cretaceous–

Paleogene Salta Group) (Figure 12C). The Pisungo Formation overlaps the shorter

northern strand of the Hornocal fault (Figure 5), cut by the main strand of the Hornocal

fault, indicating that fault activation is synchronous with deposition. The cross-cutting

and overlapping relationships of basin-bounding faults with Cianzo basin fill reveal a

complex history, interpreted as follows: 1) initiation of the Cianzo thrust; 2) coeval slip

on the Cianzo thrust and shorter northern strand of the Hornocal fault; 3) coeval motion

on the Cianzo thrust and main southern strand of the Hornocal fault, with evidence of

growth strata; and 4) final displacement on the Cianzo thrust, cutting the Hornocal fault

and Cianzo basin fill in the footwall.

60

Figure 16. Schematic regional cross sections depicting eastward progression of Cenozoic deformation proposed on the basis of structural, stratigraphic, facies, and provenance (paleocurrents, sandstone and conglomerate composition, and detrital zircon U-Pb ages) relationships. (A) Casa Grande deposition in regionally extensive foreland basin. (B) Lower Río Grande deposition involving elimination of westernmost provenance signatures due to basin partitioning. (C) Upper Río Grande deposition illustrating deformation and exhumation of Ordovician source rocks to the west, in greater proximity to the Cianzo basin. (D) Pisungo deposition, showing localized sediment sources reflecting isolation from distal western sources.

61

Chapter 7. Conclusions

Our stratigraphic and structural analysis of the Cenozoic Cianzo basin along the

Puna-Eastern Cordillera boundary in northern Argentina shows provenance,

geochronologic, and compositional patterns characteristic of a sequentially broken

foreland basin, enabling us to address the timing of deformation and complex transition

to the modern intermontane hinterland basin configuration. Additionally,

sedimentological data and mapped cross-cutting and growth strata relationships from the

Cianzo basin delineate the depositional systems. The shift from distal to locally sourced

proximal facies in the evolving foreland basin system, as well as the geometry, style, and

timing of fold-thrust deformation in the evolution from foreland to hinterland conditions.

1. Sedimentary lithofacies and facies associations identified in Cianzo basin fill

illustrate an overall upsection coarsening evolution from distal to proximal deposition

from Eocene to late Miocene time (Casa Grande, Río Grande, and Pisungo

formations). In the upper Oligocene‒Miocene Río Grande Formation, the interbedded

sheet sandstones, mudstones, and channelized sandstones and conglomerates are

characteristic of a distributary fluvial (megafan) system. An upsection coarsening

from the Río Grande Formation to the overlying changes in the Pisungo Formation

illustrates an abrupt shift to more-proximal facies reflecting deposition by sediment

gravity flows of an alluvial fan, consistent with an increased proximity to sediment

sources and contemporaneous motion on basin‒bounding faults.

2. Conglomerate clast lithologic data differentiate between local sediment sources

(principally lower Paleozoic and Cretaceous rocks), constrain the initiation of the

62

Cianzo thrust during upper Río Grande deposition, and illustrate coeval activity on

the Cianzo thrust and Hornocal fault. Upsection trends in sandstone compositions are

observed throughout the Eocene‒Miocene succession, revealing an overall increase in

the abundance of sedimentary and metamorphic lithic fragments and a decrease in

feldspathic, volcanic lithic, and monocrystalline quartz grains. These variations

suggest a progressive reduction in magmatic arc sources and an increase in fold-thrust

sources, potentially do to eastward advance of the fold-thrust belt into the eastern

Puna and Eastern Cordillera, and structural isolation of western source regions in the

western Puna and Western Cordillera. Paleocurrents throughout upper

Eocene‒Miocene fill demonstrate primarily ENE-directed flow, consistent with

major sediment sources to the west of the basin.

3. The timing and sequence of deformation in the Cianzo basin is constrained by cross-

cutting relationships of faults, growth strata, and isotopic dating of interbedded tuffs.

Cross-cutting relationships among faults and basin fill reveal a complex history of

coeval motion on the Cianzo thrust and Hornocal fault, with final motion on the

Cianzo thrust. Growth strata are characterized by an upsection decrease in bedding

dip, internal angular unconformities, and stratigraphic thinning toward the structure

are recorded in the upper Pisungo Formation demonstrating syndepositional reverse

displacement on the Hornocal fault. 40Ar/39Ar geochronological analysis of

interbedded ash-fall tuffs yield depositional ages ranging from 16.31 ± 0.6 Ma to

9.69 ± 0.05 for the Río Grande Formation, and demonstrate a significant increase in

sediment accumulation rates from the lower to upper Río Grande Formation (~300

m/Myr to ~600 m/Myr).

63

4. Detrital zircon U-Pb ages from Cenozoic sandstones of reveal critical shifts in age

peaks reflecting the activation of more proximal source regions and structural

isolation of distal western sources. The Santa Bárbara Subgroup and Casa Grande

Formation show a significant increase in Sunsás‒Grenville grains (1200‒1000 Ma),

and a distinct Permian peak at ~260 Ma, both of which indicate derivation from west

of the Cianzo basin. Upsection, sandstones of the Río Grande Formation lack Permian

age peaks, but retain an Ordovician signal at ~468 Ma, suggesting input from the

Famatinian magmatic arc rocks west of the Cianzo basin. The upper Miocene

Pisungo Formation shows a loss of this Famatinian signal, correlating with final

isolation of the Cianzo basin as the fold-thrust belt advanced eastward.

5. The integration of structural, sedimentologic, detrital zircon U-Pb geochronology,

Ar/Ar geochronology, paleocurrent, and sandstone and conglomerate compositional

data helps address the history of basin evolution and fold-thrust deformation in the

central Andes of northern Argentina. From these data, we interpreted the following

regional history: 1) an Eocene onset of fold-thrust deformation in the Western

Cordillera to west Puna plateau, as evidenced by western provenance signatures in the

Santa Bárbara Subgroup; 2) A broad Eocene‒Oligocene foreland basin system linked

to an eastward advancing fold-thrust belt; and 3) Miocene partitioning of former

foreland basin into intermontane hinterland basins during fold-thrust deformation and

fault reactivation (inversion) along the Puna plateau‒Eastern Cordillera boundary of

northern Argentina.

64

6. On a regional scale, we interpreted three main regional conclusions; 1) Early

Paleogene Santa Bárbara Subgroup records the onset of deformation in the Andean

Orogeny; 2) A broad east advancing basin system existed in the Cenozoic; and 3)

Eastern Cordillera deformation advanced systematically west to east in northern

Argentina, resulting in progressive fragmentation–partitioning of basins.

65

Appendix 1: Modal sandstone point count data from Cianzo basin

A1. Modal sandstone point count data

Qt-Ft-Lt %

Q-F-L %

Qm-F-L %

Lm-Ls-Lv %

Sample Level (m) Formation Qt Ft Lt

Q F L

Qm F L

Lm Ls Lv

P1489 6466 Pisungo 57.3 2.2 40.4 57.3 2.2 40.4 51.8 2.5 45.7 35.2 63.7 1.1 P1353 6330 Pisungo 66.4 1.8 31.8 66.2 1.6 32.2 58.6 1.9 39.5 38.6 60.7 0.7 P1239 6216 Pisungo 72.8 0.0 27.2 72.4 0.0 27.6 64.4 0.0 35.6 40.3 59.7 0.0 P1062 6039 Pisungo 67.3 0.2 32.4 67.3 0.2 32.4 59.5 0.3 40.2 39.0 61.0 0.0 P919 5896 Pisungo 59.6 0.2 40.1 59.1 0.2 40.7 52.5 0.3 47.3 41.0 59.0 0.0 P697 5674 Pisungo 63.7 0.4 35.9 63.6 0.0 36.4 56.6 0.0 43.4 36.0 64.0 0.0 P604 5581 Pisungo 67.2 1.8 31.0 66.9 1.3 31.8 61.7 1.5 36.8 28.7 71.3 0.0

RC421 4896 Río

Grande 67.9 1.8 30.4 67.6 0.9 31.6 60.2 1.1 38.7 41.5 56.3 2.1

RC335 4810 Río

Grande 69.4 1.6 29.1 68.9 0.9 30.2 60.7 1.1 38.2 46.3 50.7 2.9

RC143 4618 Río

Grande 69.3 0.9 29.8 68.7 0.9 30.4 60.6 1.1 38.3 44.5 55.5 0.0

RC001 4476 Río

Grande 66.4 1.6 32.0 65.6 0.7 33.8 58.4 0.8 40.8 45.4 52.6 2.0

B1667 4467 Río

Grande 71.1 1.8 27.1 70.7 1.1 28.2 64.4 1.3 34.2 46.5 51.2 2.4

B1472 4272 Río

Grande 77.1 2.2 20.7 77.1 2.0 20.9 73.2 2.3 24.5 42.6 56.4 1.1

B1295 4095 Río

Grande 68.9 3.8 27.3 68.4 2.9 28.7 63.6 3.3 33.1 46.5 48.8 4.7

B1044 3844 Río

Grande 68.3 4.7 27.0 67.6 3.6 28.9 63.0 4.1 32.9 52.3 43.1 4.6

B0889 3699 Río

Grande 70.2 4.0 25.7 69.8 3.1 27.1 64.9 3.6 31.5 50.0 42.6 7.4

B0737 3537 Río

Grande 76.3 1.6 22.1 75.8 0.9 23.3 70.5 1.1 28.4 59.0 34.3 6.7

B0593 3393 Río

Grande 74.6 2.9 22.5 74.2 2.0 23.8 68.7 2.4 28.8 51.4 40.2 8.4

B0439 3239 Río

Grande 73.7 4.2 22.0 73.6 2.9 23.6 67.6 3.5 28.9 48.1 44.3 7.5

B0304 3104 Río

Grande 74.3 4.2 21.4 74.0 2.9 23.1 69.0 3.4 27.5 41.3 47.1 11.5

B0160 2960 Río

Grande 72.0 5.1 22.8 71.6 2.7 25.8 68.4 3.0 28.6 35.3 43.1 21.6

B0002 2802 Río

Grande 64.4 8.8 26.8 63.6 8.7 27.8 59.2 9.7 31.1 42.4 48.0 9.6

C1305 1700 Casa

Grande 73.0 2.2 24.8 72.7 1.6 25.8 67.9 1.8 30.3 45.7 50.0 4.3

C1061 1456 Casa

Grande 74.1 10.4 15.5 73.1 9.1 17.8 68.4 10.7 20.9 47.5 41.3 11.3

C908 1303 Casa

Grande 84.8 3.6 11.7 84.0 3.1 12.9 81.4 3.6 15.0 41.4 53.4 5.2

C637 1032 Casa

Grande 87.3 7.1 5.6 87.1 5.6 7.3 84.9 6.5 8.6 48.5 21.2 30.3

C465 860 Casa

Grande 80.9 10.8 8.3 80.2 9.6 10.2 77.8 10.7 11.5 41.3 34.8 23.9

66

C299 694 Casa

Grande 96.6 1.1 2.2 95.6 1.1 3.3 94.1 1.5 4.4 0.0 66.7 33.3

C135 530 Casa

Grande 88.9 6.4 4.7 88.9 5.8 5.3 86.9 6.8 6.3 25.0 45.8 29.2

C12 407 Casa

Grande 91.5 6.5 2.0 91.3 4.9 3.8 88.9 6.3 4.8 82.4 11.8 5.9

67

Appendix B: Conglomerate clast count data

A2. Conglomerate clast composition data Gingrich Clast Counts Category

Sample Level (m) 1 2 3 4 5 6 7 8 9 Total

RA211 1961 69 17 11 7 0 1 0 0 0 105 RA422 2172 73 9 1 11 5 0 0 1 0 100 RA494 2244 92 4 3 6 1 0 2 2 0 110 RA668 2438 77 10 2 8 0 0 2 1 0 100 RB043 2845 47 41 2 9 0 0 0 1 0 100 RB920 2725 49 43 1 6 0 0 0 1 0 100 RB1867 3672 45 31 0 22 0 1 0 1 0 100 RB2109 3914 26 40 0 29 2 0 0 3 0 100 RB2188 3994 16 23 0 27 13 0 0 0 21 100 Siks Clast Counts Category

Sample Level (m) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

RCC029 4523 20 22 9 20 5 3 8 10 1 5 9 0 10 7 3 0 0 132 RCC059 4553 18 23 21 23 3 0 3 5 0 0 9 0 7 3 1 0 0 116 RCC103 4608 7 26 20 27 3 3 10 2 0 5 5 0 10 1 6 0 0 125 RCC213 4721 18 20 24 25 0 3 9 4 0 0 21 0 4 2 4 0 0 134 PA001CC 4988 16 17 23 25 6 2 8 2 10 7 4 1 10 5 3 0 0 139 PA002CC 5188 21 15 23 24 10 0 7 11 6 3 9 0 14 20 7 0 0 170 PA003CC 5232 14 10 23 19 5 1 9 2 6 2 8 0 6 8 8 0 0 121 PA004CC 5270 26 12 45 32 6 1 15 17 7 1 18 0 1 4 0 0 0 185 PA005CC 5310 17 8 18 17 2 2 10 10 6 1 7 0 8 4 3 0 0 113 PA006CC 5368 21 17 8 24 0 0 9 11 4 0 4 0 5 8 0 0 0 111 PA007CC 5412 20 11 12 26 5 2 4 6 2 4 5 0 3 2 1 0 0 103 PA008CC 5462 17 7 17 26 1 2 7 7 2 1 13 3 6 11 6 3 0 129 PA009CC 5486 23 14 19 30 5 2 8 5 4 0 13 0 0 5 9 4 0 141 PA010CC 5622 35 14 13 34 1 2 2 9 2 4 12 0 0 7 2 0 0 137 PA011CC 5644 14 18 21 25 2 1 4 20 2 4 12 0 3 7 0 9 0 142 PA012CC 5716 10 12 28 28 2 2 9 13 2 3 3 0 3 4 0 8 3 130 PA013CC 5842 24 15 21 28 3 3 9 8 1 3 8 0 1 10 3 2 0 139 PA014CC 5910 24 8 28 33 0 0 8 17 0 2 8 0 3 3 2 2 1 139 PA015CC 5966 15 9 16 20 1 0 5 16 0 5 7 1 7 7 2 3 0 114 PA016CC 6078 26 7 14 27 2 2 6 14 1 3 6 0 3 7 3 3 1 125

68

PA017CC 6114 22 7 20 30 0 0 8 10 0 0 14 0 2 6 1 4 0 124 PA018CC 6182 18 7 6 21 1 0 3 10 1 2 7 0 2 4 2 0 0 84 PA019CC 6262 18 5 13 25 2 0 7 15 0 9 1 0 2 4 3 0 0 104 PA020CC 6313 18 3 16 24 0 0 4 10 1 7 3 0 2 8 1 0 0 97 PA021CC 6470 25 8 4 26 0 1 7 5 0 1 3 3 4 10 3 2 0 102

A2. (Continued)

Conglomerate clast classification

Gingrich classification 1. Yellow / green quartzite–(Ordovician 2. Violet / gray quartzite–(Ordovician 3. Green / white quartzite–(Cambrian) 4. Dark red siltstone–(Cretaceous) 5. White / red siltstone–(Cretaceous) 6. Orange sandstone–(Cambrian) 7. White / yellow limestone–(Paleogene) 8. Dark green siltstone–(Cambrian)

Siks classification

1. Purple / red quartzite (Cretaceous) 2. Green quartzite–(Cambrian) 3. Tan / beige quartzite–(Ordovician) 4. Black / White quartzite–(Carboniferous) 5. Vein quartz–(Cambrian) 6. Dark burgundy siltstone–(Cretaceous) 7. Pink / red quartzite–(Cretaceous) 8. Yellow / brown siltstone–(Ordovician) 9. Orange / green quartzite–(Ordovician) 10. Pistachio green silt/mudstone–(Cambrian) 11. Black / red quartzite–(Cretaceous) 12. Light green quartzite–(Ordovician) 13. Dark purple quartzite–(Cretaceous) 14. Dark green / black quartzites–(Cambrian) 15. Bluish gray quartzite–(Ordovician) 16. Violet / red sandstones/mudstones- (Paleogene)

69

Appendix 3: Detrital zircon U-Pb ages

A3. LA-ICP-MS analyses for detrital zircon U-Pb geochronology

Isotope ratios Apparent ages (Ma)

Analysis 207Pb* ± 206Pb* ± error 206Pb* ± 207Pb* ± 206Pb* ± Best age ± Conc 235U* (%) 238U (%) corr. 238U* (Ma) 235U (Ma) 207Pb* (Ma) (Ma) (Ma) (%) SA01, Paleocene Mealla Formation (Santa Bárbara Group) (n = 97) SA01-1 0.8681 2.57 0.1031 0.95 0.3711 632.28 5.75 634.56 12.14 642.72 51.34 632.28 5.75 98.37 SA01-2 0.7150 2.98 0.0878 1.50 0.5034 542.69 7.81 547.69 12.61 568.56 56.02 542.69 7.81 95.45 SA01-3 0.7863 6.74 0.0964 2.50 0.3711 593.46 14.19 589.05 30.15 572.11 136.35 593.46 14.19 103.73 SA01-6 0.7394 1.73 0.0891 0.60 0.3471 550.39 3.17 562.07 7.47 609.60 35.09 550.39 3.17 90.29 SA01-7 6.8523 0.69 0.3832 0.66 0.9554 2090.98 11.71 2,092.51 6.08 2,093.99 3.56 2,093.99 3.56 99.86 SA01-8 13.7650 1.73 0.5098 1.71 0.9896 2655.57 37.30 2,733.67 16.39 2,791.87 4.07 2,791.87 4.07 95.12 SA01-9 0.5939 3.34 0.0768 3.12 0.9337 476.90 14.33 473.36 12.64 456.21 26.56 476.90 14.33 NA SA01-10 5.8750 1.22 0.3537 1.03 0.8456 1952.33 17.40 1,957.55 10.60 1,963.07 11.63 1,963.07 11.63 99.45 SA01-11 1.6761 2.58 0.1539 1.74 0.6727 922.70 14.92 999.50 16.41 1,172.02 37.80 1,172.02 37.80 78.73 SA01-12 0.7456 3.06 0.0930 2.68 0.8782 573.26 14.73 565.69 13.26 535.37 32.00 573.26 14.73 107.08 SA01-13 1.5344 3.21 0.1491 3.09 0.9626 895.98 25.83 944.24 19.72 1,058.57 17.51 1,058.57 17.51 84.64 SA01-14 0.7539 5.33 0.0908 4.86 0.9117 560.17 26.06 570.47 23.26 611.68 47.33 560.17 26.06 91.58 SA01-15 0.7241 2.42 0.0893 1.20 0.4984 551.42 6.37 553.11 10.31 560.09 45.67 551.42 6.37 98.45 SA01-16 0.7242 5.89 0.0877 1.70 0.2895 541.64 8.85 553.13 25.11 600.72 122.06 541.64 8.85 90.16 SA01-17 2.4919 3.18 0.2170 2.93 0.9227 1266.15 33.71 1,269.69 23.03 1,275.67 23.88 1,275.67 23.88 99.25 SA01-18 1.8029 1.71 0.1774 0.88 0.5179 1052.84 8.58 1,046.50 11.14 1,033.27 29.50 1,033.27 29.50 101.89 SA01-19 0.7283 4.59 0.0891 2.20 0.4785 550.03 11.59 555.55 19.66 578.22 87.68 550.03 11.59 95.13 SA01-21 1.6685 5.30 0.1654 5.00 0.9440 986.76 45.79 996.62 33.67 1,018.36 35.43 1,018.36 35.43 96.90 SA01-22 0.1836 24.33 0.0296 4.44 0.1823 187.94 8.22 171.12 38.33 -55.45 589.92 187.94 8.22 NA

70

SA01-23 9.3625 3.38 0.4541 3.30 0.9756 2413.53 66.47 2,374.17 31.05 2,340.53 12.70 2,340.53 12.70 103.12 SA01-24 1.7673 3.30 0.1736 2.98 0.9036 1031.66 28.43 1,033.53 21.40 1,037.46 28.56 1,037.46 28.56 99.44 SA01-25 0.7100 4.74 0.0883 2.76 0.5832 545.28 14.45 544.74 19.99 542.49 84.20 545.28 14.45 100.51 SA01-26 0.6345 3.21 0.0795 1.71 0.5323 493.28 8.11 498.89 12.65 524.69 59.60 493.28 8.11 94.01 SA01-27 7.3847 3.20 0.4041 3.12 0.9733 2187.68 57.83 2,159.11 28.65 2,132.05 12.88 2,132.05 12.88 102.61 SA01-28 5.1293 1.00 0.3374 0.96 0.9627 1874.38 15.65 1,840.97 8.49 1,803.39 4.92 1,803.39 4.92 103.94 SA01-29 1.2850 4.45 0.1379 2.31 0.5199 832.58 18.08 839.10 25.43 856.37 79.03 832.58 18.08 97.22 SA01-30 12.9921 2.19 0.5058 2.15 0.9805 2638.73 46.53 2,679.08 20.67 2,709.66 7.11 2,709.66 7.11 97.38 SA01-31 0.7741 1.64 0.0963 1.17 0.7128 592.45 6.61 582.09 7.26 541.90 25.16 592.45 6.61 109.33 SA01-32 1.8956 1.72 0.1846 1.24 0.7243 1092.10 12.50 1,079.56 11.42 1,054.34 23.87 1,054.34 23.87 103.58 SA01-34 2.1395 2.10 0.1988 1.73 0.8232 1169.06 18.50 1,161.65 14.54 1,147.87 23.72 1,147.87 23.72 101.85 SA01-35 0.8354 5.35 0.0996 4.06 0.7586 611.83 23.69 616.58 24.73 634.11 75.09 611.83 23.69 96.49 SA01-36 1.8539 1.65 0.1823 1.33 0.8073 1079.43 13.23 1,064.82 10.88 1,034.99 19.68 1,034.99 19.68 104.29 SA01-37 2.1111 1.60 0.1982 1.35 0.8475 1165.53 14.42 1,152.43 10.99 1,127.90 16.87 1,127.90 16.87 103.34 SA01-38 17.3748 5.79 0.5806 4.82 0.8317 2951.13 114.05 2,955.76 55.65 2,958.90 51.88 2,958.90 51.88 99.74 SA01-39 0.7174 1.43 0.0903 1.08 0.7559 557.44 5.75 549.13 6.04 514.76 20.51 557.44 5.75 108.29 SA01-40 3.2700 1.66 0.2625 1.20 0.7192 1502.81 16.03 1,473.94 12.93 1,432.59 22.04 1,432.59 22.04 104.90 SA01-41 1.1394 8.06 0.1152 6.06 0.7516 702.70 40.34 772.20 43.62 978.83 108.43 702.70 40.34 71.79 SA01-42 1.8618 1.71 0.1822 1.35 0.7927 1078.78 13.46 1,067.63 11.29 1,044.89 21.03 1,044.89 21.03 103.24 SA01-43 6.4081 2.00 0.3721 1.67 0.8343 2039.27 29.13 2,033.38 17.54 2,027.38 19.49 2,027.38 19.49 100.59 SA01-44 1.9873 4.91 0.1904 1.58 0.3224 1123.47 16.33 1,111.19 33.20 1,087.23 93.27 1,087.23 93.27 103.33 SA01-45 0.6076 8.29 0.0795 3.61 0.4348 493.43 17.13 482.03 31.83 428.15 166.68 493.43 17.13 NA SA01-47 2.8906 3.57 0.2439 3.54 0.9916 1407.03 44.73 1,379.45 26.93 1,337.01 8.94 1,337.01 8.94 105.24 SA01-49 1.0519 2.49 0.1203 1.56 0.6282 732.13 10.82 729.81 12.96 722.69 41.11 732.13 10.82 101.31 SA01-50 0.6198 3.03 0.0799 2.03 0.6703 495.41 9.68 489.70 11.76 463.12 49.80 495.41 9.68 NA SA01-R33 0.5188 3.77 0.0685 1.63 0.4322 427.25 6.74 424.37 13.08 408.74 76.10 427.25 6.74 NA

71

SA01-52 2.1404 4.12 0.2007 3.98 0.9658 1178.97 42.91 1,161.95 28.54 1,130.34 21.29 1,130.34 21.29 104.30 SA01-53 0.3396 11.32 0.0439 6.79 0.5998 276.68 18.39 296.88 29.14 458.92 201.22 276.68 18.39 NA SA01-54 1.2093 2.30 0.1323 1.32 0.5748 801.05 9.96 804.87 12.78 815.48 39.36 801.05 9.96 98.23 SA01-55 0.4726 5.74 0.0638 1.74 0.3031 398.93 6.72 393.00 18.69 358.21 123.46 398.93 6.72 NA SA01-56 0.7642 2.79 0.0941 1.49 0.5328 579.64 8.25 576.43 12.29 563.74 51.50 579.64 8.25 102.82 SA01-58 1.7130 1.84 0.1718 1.44 0.7811 1021.88 13.56 1,013.41 11.78 995.13 23.32 995.13 23.32 102.69 SA01-59 2.9997 2.20 0.2393 1.58 0.7187 1382.93 19.65 1,407.54 16.73 1,444.97 29.09 1,444.97 29.09 95.71 SA01-60 0.7167 3.30 0.0903 1.80 0.5445 557.60 9.60 548.69 13.99 511.91 60.87 557.60 9.60 108.93 SA01-61 13.9048 2.04 0.5345 2.02 0.9876 2760.32 45.26 2,743.24 19.33 2,730.69 5.26 2,730.69 5.26 101.09 SA01-62 0.7167 4.41 0.0899 3.98 0.9018 555.05 21.17 548.74 18.72 522.60 41.85 555.05 21.17 106.21 SA01-63 5.5832 3.00 0.3224 2.89 0.9656 1801.20 45.47 1,913.51 25.81 2,037.52 13.79 2,037.52 13.79 88.40 SA01-66 0.6845 1.94 0.0841 1.28 0.6583 520.34 6.39 529.50 8.02 569.20 31.83 520.34 6.39 91.41 SA01-67 0.7621 2.15 0.0909 1.96 0.9144 560.59 10.54 575.21 9.43 633.42 18.72 560.59 10.54 88.50 SA01-69 0.7901 3.64 0.0955 3.29 0.9055 587.92 18.50 591.20 16.29 603.79 33.40 587.92 18.50 97.37 SA01-71 2.4932 4.77 0.2149 4.28 0.8971 1254.73 48.80 1,270.05 34.59 1,296.06 40.98 1,296.06 40.98 96.81 SA01-73 0.6994 4.94 0.0878 2.88 0.5826 542.41 14.98 538.45 20.65 521.70 88.14 542.41 14.98 103.97 SA01-77 4.9145 1.04 0.3254 0.69 0.6651 1816.20 10.99 1,804.75 8.81 1,791.54 14.20 1,791.54 14.20 101.38 SA01-78 1.9270 2.11 0.1838 1.13 0.5377 1087.89 11.35 1,090.49 14.10 1,095.72 35.58 1,095.72 35.58 99.28 SA01-79 1.3888 1.95 0.1457 0.72 0.3704 876.67 5.93 884.20 11.53 903.07 37.40 876.67 5.93 97.08 SA01-81 0.6028 7.12 0.0781 3.20 0.4496 484.89 14.94 478.98 27.18 450.76 141.31 484.89 14.94 NA SA01-82 0.6329 9.17 0.0813 2.55 0.2783 503.65 12.36 497.93 36.10 471.72 195.19 503.65 12.36 NA SA01-83 0.3416 3.18 0.0466 1.82 0.5722 293.44 5.23 298.42 8.23 337.58 59.15 293.44 5.23 NA SA01-86 0.8871 7.13 0.1050 2.31 0.3234 643.86 14.13 644.81 34.06 648.16 145.11 643.86 14.13 99.34 SA01-87 0.8065 3.52 0.0981 3.26 0.9250 603.16 18.76 600.50 15.97 590.47 29.01 603.16 18.76 102.15 SA01-88 0.5432 2.09 0.0719 1.61 0.7711 447.35 6.96 440.55 7.47 405.17 29.78 447.35 6.96 NA SA01-89 1.7415 5.98 0.1747 4.34 0.7250 1037.93 41.58 1,024.02 38.61 994.44 83.79 994.44 83.79 104.37

72

SA01-90 1.7746 3.09 0.1725 1.55 0.5004 1025.72 14.67 1,036.20 20.08 1,058.40 53.89 1,058.40 53.89 96.91 SA01-91 0.6645 7.72 0.0814 6.30 0.8153 504.45 30.55 517.39 31.32 574.95 97.27 504.45 30.55 87.74 SA01-92 0.7040 3.47 0.0881 1.04 0.2987 544.11 5.41 541.17 14.56 528.83 72.57 544.11 5.41 102.89 SA01-93 0.7887 2.66 0.0954 2.38 0.8950 587.20 13.36 590.46 11.91 602.97 25.66 587.20 13.36 97.38 SA01-94 0.8762 8.39 0.0978 3.94 0.4701 601.70 22.66 638.93 39.81 772.85 156.06 601.70 22.66 77.86 SA01-95 0.8481 3.57 0.1006 3.27 0.9168 618.17 19.29 623.58 16.63 643.28 30.65 618.17 19.29 96.10 SA01-97 0.7604 2.30 0.0938 1.57 0.6851 577.98 8.71 574.25 10.08 559.54 36.52 577.98 8.71 103.29 SA01-98 0.9761 3.07 0.1131 2.84 0.9248 690.58 18.60 691.58 15.40 694.86 24.88 690.58 18.60 99.38 SA01-99 0.9409 6.57 0.1097 1.31 0.1990 671.05 8.33 673.37 32.33 681.12 137.61 671.05 8.33 98.52 SA01-100 12.9147 1.91 0.5266 1.79 0.9417 2727.27 39.90 2,673.45 17.96 2,632.98 10.66 2,632.98 10.66 103.58 SA01-101 0.3118 10.11 0.0420 4.11 0.4062 265.36 10.67 275.61 24.40 363.49 208.66 265.36 10.67 NA SA01-103 0.7879 3.39 0.0972 3.00 0.8827 597.74 17.10 589.99 15.19 560.27 34.76 597.74 17.10 106.69 SA01-104 0.7576 4.53 0.0946 1.59 0.3503 582.58 8.85 572.60 19.84 533.12 93.00 582.58 8.85 109.28 SA01-105 2.0719 4.20 0.1968 4.15 0.9891 1158.22 44.01 1,139.56 28.75 1,104.22 12.40 1,104.22 12.40 104.89 SA01-106 0.7646 3.45 0.0939 0.81 0.2357 578.62 4.49 576.65 15.16 568.92 72.91 578.62 4.49 101.71 SA01-107 4.9703 1.66 0.3296 1.40 0.8442 1836.48 22.37 1,814.28 14.02 1,788.86 16.19 1,788.86 16.19 102.66 SA01-108 0.8824 3.45 0.1039 0.89 0.2564 637.11 5.37 642.25 16.44 660.40 71.55 637.11 5.37 96.47 SA01-110 2.4006 1.80 0.2154 1.44 0.7985 1257.52 16.44 1,242.78 12.92 1,217.31 21.35 1,217.31 21.35 103.30 SA01-111 2.8842 2.82 0.2401 1.10 0.3901 1387.24 13.74 1,377.79 21.29 1,363.15 50.08 1,363.15 50.08 101.77 SA01-113 1.7349 3.05 0.1693 2.19 0.7183 1008.07 20.46 1,021.57 19.66 1,050.62 42.83 1,050.62 42.83 95.95 SA01-114 11.5840 1.30 0.4424 1.27 0.9749 2361.43 25.05 2,571.39 12.15 2,741.31 4.76 2,741.31 4.76 86.14 SA01-115 1.2151 2.65 0.1356 2.20 0.8333 819.48 16.97 807.51 14.74 774.64 30.77 819.48 16.97 105.79 SA01-116 0.8055 1.96 0.0992 1.58 0.8082 609.51 9.21 599.94 8.88 563.91 25.14 609.51 9.21 108.09 SA01-117 2.8126 2.30 0.2359 2.02 0.8797 1365.54 24.90 1,358.89 17.23 1,348.42 21.12 1,348.42 21.12 101.27 SA01-118 31.8918 1.32 0.7245 1.31 0.9918 3512.82 35.48 3,546.96 13.01 3,566.27 2.60 3,566.27 2.60 98.50 SA01-119 0.8161 3.86 0.0982 2.56 0.6637 603.74 14.76 605.87 17.61 613.82 62.38 603.74 14.76 98.36

73

SA01-120 0.8344 3.21 0.1008 1.38 0.4285 619.37 8.12 616.07 14.83 603.97 62.77 619.37 8.12 102.55

SA01-R33 0.5300 7.82 0.0680 1.57 0.2014 423.95 6.46 431.81 27.51 473.97 169.62 423.95 6.46 NA CA184 Eocene - Oligocene Casa Grande Formation (n = 101) CA184-2 12.4076 3.87 0.4750 3.87 0.9991 2505.29 80.32 2,635.76 36.40 2,737.50 2.65 2,737.50 2.65 91.52 CA184-3 1.6691 3.24 0.1643 2.93 0.9026 980.59 26.63 996.84 20.60 1,032.73 28.24 1,032.73 28.24 94.95 CA184-4 2.0236 3.71 0.1925 2.56 0.6917 1134.87 26.69 1,123.45 25.20 1,101.42 53.54 1,101.42 53.54 103.04 CA184-5 0.2984 2.64 0.0413 2.05 0.7776 260.77 5.24 265.19 6.16 304.33 37.81 260.77 5.24 NA CA184-7 1.8297 3.68 0.1786 3.38 0.9177 1059.52 32.98 1,056.16 24.15 1,049.22 29.46 1,049.22 29.46 100.98 CA184-8 1.7937 2.38 0.1741 1.07 0.4502 1034.70 10.26 1,043.17 15.54 1,060.97 42.83 1,060.97 42.83 97.52 CA184-9 1.7683 3.82 0.1705 2.27 0.5935 1014.95 21.31 1,033.91 24.80 1,074.24 61.82 1,074.24 61.82 94.48 CA184-10 0.6804 8.51 0.0816 3.35 0.3935 505.77 16.29 527.04 35.00 620.29 169.02 505.77 16.29 81.54 CA184-11 2.2918 2.05 0.2052 1.89 0.9229 1203.18 20.73 1,209.75 14.47 1,221.52 15.51 1,221.52 15.51 98.50 CA184-12 0.8797 5.72 0.1044 2.10 0.3678 640.03 12.81 640.80 27.17 643.54 114.32 640.03 12.81 99.45 CA184-13 2.4970 2.68 0.2158 2.62 0.9767 1259.51 29.94 1,271.16 19.43 1,290.89 11.19 1,290.89 11.19 97.57 CA184-14 6.2115 3.51 0.3675 3.18 0.9057 2017.73 55.14 2,006.07 30.74 1,994.08 26.48 1,994.08 26.48 101.19 CA184-15 0.3462 5.81 0.0455 3.83 0.6600 286.99 10.76 301.84 15.17 418.32 97.51 286.99 10.76 NA CA184-16 0.2804 7.85 0.0427 2.34 0.2982 269.36 6.18 250.97 17.46 82.42 178.06 269.36 6.18 NA CA184-17 0.7926 6.16 0.0968 1.77 0.2878 595.42 10.08 592.63 27.64 581.95 128.15 595.42 10.08 102.31 CA184-18 1.7735 2.26 0.1736 1.30 0.5744 1032.13 12.38 1,035.80 14.67 1,043.52 37.32 1,043.52 37.32 98.91 CA184-19 3.1366 1.56 0.2447 1.50 0.9650 1410.98 19.02 1,441.72 11.98 1,487.35 7.73 1,487.35 7.73 94.86 CA184-20 0.5663 5.31 0.0765 1.71 0.3213 475.40 7.83 455.63 19.51 357.02 113.64 475.40 7.83 NA CA184-24 0.5735 7.27 0.0737 6.32 0.8687 458.50 27.97 460.26 26.93 469.06 79.79 458.50 27.97 NA CA184-25 1.8252 3.12 0.1773 1.70 0.5450 1052.29 16.50 1,054.56 20.45 1,059.28 52.61 1,059.28 52.61 99.34 CA184-26 0.6642 3.81 0.0856 1.66 0.4369 529.29 8.45 517.18 15.43 464.04 75.89 529.29 8.45 NA CA184-27 0.8890 4.93 0.1010 1.85 0.3749 620.33 10.93 645.81 23.55 735.97 96.73 620.33 10.93 84.29

74

CA184-28 2.2614 2.53 0.2058 2.01 0.7945 1206.19 22.14 1,200.35 17.83 1,189.87 30.37 1,189.87 30.37 101.37 CA184-29 0.5958 7.06 0.0745 1.61 0.2274 463.43 7.18 474.58 26.77 528.86 150.80 463.43 7.18 NA CA184-30 0.7994 7.78 0.0942 1.68 0.2162 580.10 9.34 596.49 35.12 659.29 163.12 580.10 9.34 87.99 CA184-31 0.6536 3.74 0.0802 1.40 0.3736 497.40 6.69 510.72 15.01 570.81 75.51 497.40 6.69 87.14 CA184-32 18.8044 1.29 0.6131 1.27 0.9856 3082.55 31.18 3,031.83 12.45 2,998.38 3.51 2,998.38 3.51 102.81 CA184-33 11.5900 1.56 0.4468 1.52 0.9725 2380.82 30.27 2,571.87 14.62 2,726.07 6.00 2,726.07 6.00 87.34 CA184-34 0.6051 6.14 0.0778 1.51 0.2455 482.97 7.01 480.47 23.50 468.54 131.83 482.97 7.01 NA CA184-35 18.1688 1.30 0.5617 1.14 0.8744 2873.45 26.32 2,998.71 12.50 3,083.80 10.06 3,083.80 10.06 93.18 CA184-37 10.6362 1.75 0.4560 1.70 0.9724 2421.80 34.40 2,491.88 16.26 2,549.49 6.85 2,549.49 6.85 94.99 CA184-39 0.7963 2.91 0.0965 1.32 0.4554 594.14 7.51 594.74 13.08 597.08 56.05 594.14 7.51 99.51 CA184-40 0.7122 5.13 0.0877 1.49 0.2900 541.67 7.72 546.07 21.66 564.45 106.94 541.67 7.72 95.97 CA184-41 3.5605 1.34 0.2742 0.86 0.6423 1561.89 11.98 1,540.79 10.66 1,511.93 19.45 1,511.93 19.45 103.30 CA184-42 0.5714 5.40 0.0739 1.36 0.2516 459.89 6.03 458.92 19.93 454.07 116.02 459.89 6.03 NA CA184-43 0.1707 1.83 0.0251 1.03 0.5642 160.00 1.63 160.01 2.71 160.16 35.44 160.00 1.63 NA CA184-45 0.2608 15.06 0.0412 3.25 0.2156 260.15 8.28 235.33 31.64 -5.66 356.42 260.15 8.28 NA CA184-46 0.8616 5.23 0.1013 1.12 0.2144 622.26 6.65 631.02 24.58 662.50 109.52 622.26 6.65 93.93 CA184-48 0.9463 2.80 0.1124 2.17 0.7750 686.65 14.11 676.16 13.80 641.42 37.98 686.65 14.11 107.05 CA184-49 1.8665 1.93 0.1829 1.63 0.8456 1082.71 16.28 1,069.30 12.77 1,042.02 20.83 1,042.02 20.83 103.91 CA184-50 6.4844 3.61 0.3790 3.49 0.9681 2071.42 61.88 2,043.79 31.75 2,016.01 16.04 2,016.01 16.04 102.75 CA184-51 0.8205 4.71 0.0995 3.03 0.6423 611.39 17.66 608.31 21.57 596.90 78.29 611.39 17.66 102.43 CA184-52 7.0108 3.05 0.3965 3.03 0.9934 2152.96 55.46 2,112.80 27.11 2,073.92 6.18 2,073.92 6.18 103.81 CA184-53 0.7280 3.07 0.0888 2.31 0.7531 548.24 12.16 555.36 13.14 584.68 43.88 548.24 12.16 93.77 CA184-55 11.2196 2.48 0.4936 2.47 0.9968 2586.11 52.61 2,541.55 23.10 2,506.16 3.34 2,506.16 3.34 103.19 CA184-56 1.6057 2.50 0.1649 2.02 0.8076 983.91 18.41 972.45 15.63 946.64 30.15 946.64 30.15 103.94 CA184-57 7.1678 2.13 0.3962 2.12 0.9956 2151.39 38.85 2,132.51 19.01 2,114.33 3.49 2,114.33 3.49 101.75 CA184-58 11.5044 2.94 0.4745 2.93 0.9963 2503.29 60.70 2,564.94 27.44 2,614.02 4.17 2,614.02 4.17 95.76

75

CA184-59 0.8757 4.57 0.1065 3.07 0.6724 652.11 19.05 638.66 21.66 591.37 73.36 652.11 19.05 110.27 CA184-60 0.7538 4.45 0.0922 2.48 0.5588 568.29 13.52 570.44 19.41 578.99 80.12 568.29 13.52 98.15 CA184-61 7.9338 1.76 0.4176 1.73 0.9832 2249.75 32.91 2,223.53 15.89 2,199.44 5.58 2,199.44 5.58 102.29 CA184-63 0.7520 3.03 0.0930 1.63 0.5395 573.34 8.97 569.40 13.21 553.70 55.68 573.34 8.97 103.55 CA184-64 1.8400 1.80 0.1816 1.42 0.7888 1075.80 14.08 1,059.86 11.85 1,027.17 22.41 1,027.17 22.41 104.73 CA184-65 0.7272 2.04 0.0905 1.37 0.6737 558.77 7.36 554.90 8.72 539.07 32.98 558.77 7.36 103.65 CA184-67 13.4096 2.27 0.5245 2.16 0.9549 2718.10 48.00 2,708.93 21.42 2,702.09 11.12 2,702.09 11.12 100.59 CA184-68 0.3307 3.99 0.0456 3.66 0.9181 287.34 10.28 290.08 10.06 312.23 35.93 287.34 10.28 NA CA184-69 0.6493 5.28 0.0847 3.44 0.6528 524.22 17.34 508.07 21.09 435.99 89.04 524.22 17.34 NA CA184-70 0.6835 3.63 0.0861 1.95 0.5366 532.22 9.95 528.86 14.97 514.40 67.32 532.22 9.95 103.46 CA184-71 0.8196 7.17 0.0984 3.13 0.4359 604.80 18.05 607.83 32.82 619.12 139.46 604.80 18.05 97.69 CA184-73 9.3958 1.78 0.4577 1.76 0.9915 2429.50 35.64 2,377.42 16.30 2,333.06 3.95 2,333.06 3.95 104.13 CA184-75 1.7473 1.46 0.1728 1.07 0.7336 1027.42 10.14 1,026.18 9.40 1,023.52 20.01 1,023.52 20.01 100.38 CA184-76 0.6934 3.75 0.0855 2.28 0.6061 528.80 11.55 534.82 15.61 560.60 65.07 528.80 11.55 94.33 CA184-77 1.6676 2.75 0.1659 1.63 0.5935 989.44 14.97 996.25 17.46 1,011.26 44.89 1,011.26 44.89 97.84 CA184-78 5.2873 2.45 0.3333 2.24 0.9148 1854.19 36.04 1,866.81 20.88 1,880.89 17.80 1,880.89 17.80 98.58 CA184-79 19.1069 1.76 0.6083 1.70 0.9650 3063.28 41.38 3,047.23 16.97 3,036.65 7.38 3,036.65 7.38 100.88 CA184-80 1.8661 7.04 0.1781 2.81 0.3987 1056.35 27.35 1,069.15 46.58 1,095.37 129.39 1,095.37 129.39 96.44 CA184-81 1.5402 7.07 0.1534 3.64 0.5154 919.76 31.23 946.56 43.56 1,009.41 122.97 1,009.41 122.97 91.12 CA184-83 0.8947 2.48 0.1061 2.27 0.9163 650.27 14.05 648.91 11.88 644.21 21.32 650.27 14.05 100.94 CA184-84 0.8005 6.08 0.0973 2.95 0.4842 598.59 16.84 597.10 27.48 591.45 115.51 598.59 16.84 101.21 CA184-85 1.7561 4.47 0.1741 2.51 0.5612 1034.60 23.98 1,029.42 28.93 1,018.40 74.97 1,018.40 74.97 101.59 CA184-86 1.9470 1.45 0.1881 1.26 0.8717 1110.97 12.87 1,097.43 9.71 1,070.68 14.25 1,070.68 14.25 103.76 CA184-88 2.3640 2.78 0.2093 1.82 0.6536 1225.34 20.29 1,231.79 19.86 1,243.09 41.25 1,243.09 41.25 98.57 CA184-89 5.2285 1.53 0.3277 1.41 0.9243 1827.24 22.46 1,857.28 13.02 1,891.06 10.49 1,891.06 10.49 96.63 CA184-91 2.3341 3.21 0.1984 3.12 0.9746 1166.64 33.34 1,222.72 22.79 1,323.05 13.91 1,323.05 13.91 88.18

76

CA184-92 1.7824 2.66 0.1746 1.33 0.4981 1037.53 12.72 1,039.07 17.34 1,042.29 46.63 1,042.29 46.63 99.54 CA184-93 1.0220 2.64 0.1172 1.86 0.7064 714.36 12.60 714.89 13.54 716.55 39.66 714.36 12.60 99.69 CA184-94 0.4489 9.61 0.0633 2.49 0.2587 395.93 9.54 376.48 30.24 258.52 213.65 395.93 9.54 NA CA184-95 1.7907 3.13 0.1752 2.70 0.8638 1040.73 25.99 1,042.07 20.40 1,044.86 31.84 1,044.86 31.84 99.60 CA184-96 1.6991 5.80 0.1659 5.59 0.9638 989.75 51.26 1,008.20 37.06 1,048.54 31.14 1,048.54 31.14 94.39 CA184-97 1.6978 6.29 0.1634 4.71 0.7488 975.64 42.66 1,007.70 40.23 1,078.08 83.74 1,078.08 83.74 90.50 CA184-98 3.2930 2.63 0.2551 2.61 0.9908 1464.87 34.20 1,479.40 20.52 1,500.28 6.73 1,500.28 6.73 97.64 CA184-99 0.2700 6.44 0.0391 2.13 0.3310 247.43 5.17 242.72 13.90 197.44 141.28 247.43 5.17 NA CA184-100 0.7245 8.76 0.0907 8.59 0.9801 559.71 46.03 553.33 37.39 527.20 38.10 559.71 46.03 106.16 CA184-101 1.8118 0.86 0.1766 0.58 0.6822 1048.46 5.65 1,049.72 5.60 1,052.36 12.63 1,052.36 12.63 99.63 CA184-102 0.6970 1.94 0.0865 1.13 0.5800 534.80 5.79 536.97 8.11 546.19 34.61 534.80 5.79 97.92 CA184-103 0.3731 4.67 0.0513 1.76 0.3766 322.64 5.53 321.98 12.88 317.19 98.32 322.64 5.53 NA CA184-104 0.7056 4.12 0.0851 1.51 0.3674 526.38 7.64 542.13 17.29 608.89 82.76 526.38 7.64 86.45 CA184-105 5.0270 2.04 0.3262 1.30 0.6407 1819.99 20.68 1,823.87 17.24 1,828.30 28.34 1,828.30 28.34 99.55 CA184-106 0.9034 2.36 0.1061 1.86 0.7849 650.29 11.48 653.53 11.39 664.76 31.36 650.29 11.48 97.82 CA184-108 0.9676 2.40 0.1128 1.96 0.8162 689.16 12.79 687.21 11.97 680.84 29.61 689.16 12.79 101.22 CA184-109 1.1963 1.84 0.1323 1.11 0.6055 800.89 8.37 798.89 10.15 793.29 30.67 800.89 8.37 100.96 CA184-110 1.8602 1.57 0.1800 1.49 0.9471 1066.81 14.65 1,067.07 10.39 1,067.61 10.14 1,067.61 10.14 99.93 CA184-111 0.6892 3.98 0.0866 2.32 0.5830 535.23 11.91 532.31 16.48 519.81 70.93 535.23 11.91 102.97 CA184-112 1.8147 1.84 0.1778 1.66 0.8987 1054.83 16.13 1,050.77 12.08 1,042.32 16.34 1,042.32 16.34 101.20 CA184-113 1.7395 4.07 0.1748 3.35 0.8229 1038.64 32.12 1,023.29 26.24 990.62 47.01 990.62 47.01 104.85 CA184-114 2.1940 3.01 0.2024 2.56 0.8505 1188.16 27.74 1,179.15 20.97 1,162.63 31.34 1,162.63 31.34 102.20 CA184-115 1.7976 2.79 0.1771 2.40 0.8587 1051.17 23.27 1,044.57 18.23 1,030.77 28.96 1,030.77 28.96 101.98 CA184-116 0.6881 3.28 0.0862 2.88 0.8793 532.82 14.75 531.67 13.58 526.77 34.26 532.82 14.75 101.15 CA184-117 1.9957 3.81 0.1913 3.74 0.9807 1128.60 38.72 1,114.07 25.80 1,085.84 14.94 1,085.84 14.94 103.94 CA184-118 3.6593 3.60 0.2765 3.48 0.9676 1573.54 48.61 1,562.54 28.70 1,547.70 17.07 1,547.70 17.07 101.67

77

CA184-119 0.9113 5.36 0.1064 3.38 0.6315 651.99 20.98 657.75 25.94 677.56 88.82 651.99 20.98 96.23

CA184-120 1.5871 4.91 0.1621 3.48 0.7071 968.59 31.25 965.17 30.62 957.36 71.03 957.36 71.03 101.17 RB835 Miocene Río Grande Formation (n = 96) RB-835-1 8.2903 2.12 0.4189 2.04 0.9628 2255.46 38.82 2,263.26 19.20 2,270.30 9.86 2,270.30 9.86 99.35 RB-835-2 0.6700 3.47 0.0837 1.98 0.5720 518.04 9.87 520.73 14.13 532.54 62.30 518.04 9.87 97.28 RB-835-3 0.7833 2.58 0.0954 2.24 0.8653 587.65 12.55 587.35 11.52 586.19 28.08 587.65 12.55 100.25 RB-835-4 2.2513 2.92 0.2019 1.14 0.3891 1185.62 12.30 1,197.19 20.52 1,218.12 52.89 1,218.12 52.89 97.33 RB-835-7 1.8519 3.31 0.1771 2.87 0.8670 1051.08 27.79 1,064.12 21.80 1,090.94 32.98 1,090.94 32.98 96.35 RB-835-9 1.1087 2.23 0.1262 2.05 0.9210 766.10 14.84 757.55 11.91 732.40 18.40 766.10 14.84 104.60 RB-835-10 5.3029 3.76 0.3311 1.90 0.5042 1843.74 30.40 1,869.34 32.14 1,897.89 58.40 1,897.89 58.40 97.15 RB-835-11 0.6928 9.28 0.0862 1.53 0.1651 532.96 7.83 534.47 38.57 540.90 200.43 532.96 7.83 98.53 RB-835-12 2.8771 1.99 0.2347 1.84 0.9231 1358.87 22.56 1,375.92 15.03 1,402.47 14.69 1,402.47 14.69 96.89 RB-835-14 12.5696 2.28 0.4750 2.23 0.9794 2505.52 46.32 2,647.95 21.43 2,758.65 7.56 2,758.65 7.56 90.82 RB-835-15 0.5993 5.92 0.0755 2.05 0.3469 469.37 9.29 476.80 22.51 512.69 122.02 469.37 9.29 NA RB-835-17 0.6880 7.58 0.0844 3.83 0.5057 522.38 19.24 531.59 31.39 571.36 142.46 522.38 19.24 91.43 RB-835-18 0.5817 1.49 0.0757 1.10 0.7360 470.48 4.98 465.56 5.57 441.33 22.49 470.48 4.98 NA RB-835-20 3.2305 1.22 0.2554 0.87 0.7129 1466.47 11.38 1,464.50 9.44 1,461.64 16.22 1,461.64 16.22 100.33 RB-835-21 1.3076 3.37 0.1406 1.34 0.3963 848.08 10.61 849.06 19.39 851.61 64.31 848.08 10.61 99.59 RB-835-22 1.7888 3.27 0.1739 2.56 0.7834 1033.35 24.45 1,041.39 21.29 1,058.31 40.90 1,058.31 40.90 97.64 RB-835-23 12.2094 1.73 0.4996 1.65 0.9530 2612.18 35.42 2,620.63 16.24 2,627.15 8.72 2,627.15 8.72 99.43 RB-835-24 0.7883 9.28 0.0891 3.93 0.4237 550.43 20.74 590.22 41.55 746.31 177.90 550.43 20.74 73.75 RB-835-25 0.8069 2.61 0.0977 1.61 0.6173 600.84 9.26 600.73 11.85 600.31 44.52 600.84 9.26 100.09 RB-835-26 1.8187 2.80 0.1775 2.77 0.9910 1053.37 26.92 1,052.21 18.32 1,049.80 7.58 1,049.80 7.58 100.34 RB-835-27 0.9046 2.55 0.1052 2.14 0.8391 644.56 13.12 654.19 12.29 687.52 29.59 644.56 13.12 93.75 RB-835-29 28.7933 2.00 0.6719 1.99 0.9964 3313.10 51.62 3,446.50 19.62 3,524.97 2.60 3,524.97 2.60 93.99

78

RB-835-30 12.6241 2.94 0.4771 2.92 0.9928 2514.59 60.85 2,652.02 27.70 2,758.58 5.78 2,758.58 5.78 91.16 RB-835-31 2.6669 2.98 0.2222 1.20 0.4042 1293.37 14.11 1,319.33 22.00 1,361.72 52.51 1,361.72 52.51 94.98 RB-835-32 0.7717 6.31 0.0944 4.83 0.7650 581.30 26.83 580.76 27.91 578.69 88.32 581.30 26.83 100.45 RB-835-34 0.8201 5.46 0.0991 2.60 0.4763 608.90 15.11 608.13 24.98 605.23 103.88 608.90 15.11 100.61 RB-835-35 1.7573 2.55 0.1706 1.77 0.6938 1015.20 16.62 1,029.85 16.51 1,061.11 36.97 1,061.11 36.97 95.67 RB-835-37 0.7069 7.52 0.0857 2.75 0.3659 530.29 14.00 542.92 31.62 596.28 151.73 530.29 14.00 88.93 RB-835-38 0.7064 8.02 0.0881 5.10 0.6367 544.23 26.63 542.59 33.70 535.70 135.42 544.23 26.63 101.59 RB-835-39 0.6300 1.54 0.0797 0.75 0.4862 494.58 3.56 496.12 6.04 503.25 29.63 494.58 3.56 NA RB-835-40 1.6974 4.63 0.1691 4.27 0.9233 1007.07 39.83 1,007.54 29.57 1,008.55 36.02 1,008.55 36.02 99.85 RB-835-41 2.0711 1.87 0.1936 0.92 0.4917 1141.06 9.59 1,139.29 12.77 1,135.91 32.32 1,135.91 32.32 100.45 RB-835-43 0.8540 8.01 0.1019 2.66 0.3326 625.82 15.88 626.86 37.46 630.66 162.83 625.82 15.88 99.23 RB-835-44 0.6120 3.44 0.0773 2.86 0.8336 480.07 13.25 484.85 13.25 507.52 41.76 480.07 13.25 NA RB-835-45 6.2790 3.85 0.3639 3.84 0.9985 2000.49 66.06 2,015.53 33.71 2,030.96 3.74 2,030.96 3.74 98.50 RB-835-46 0.8970 4.15 0.1056 1.67 0.4029 647.15 10.29 650.11 19.91 660.40 81.38 647.15 10.29 97.99 RB-835-47 0.5675 3.88 0.0732 1.85 0.4783 455.64 8.16 456.40 14.26 460.22 75.55 455.64 8.16 NA RB-835-48 0.6689 2.25 0.0831 1.08 0.4780 514.59 5.33 520.04 9.17 544.05 43.23 514.59 5.33 94.58 RB-835-49 1.7860 2.37 0.1779 0.83 0.3490 1055.45 8.07 1,040.37 15.45 1,008.81 45.13 1,008.81 45.13 104.62 RB-835-50 0.8621 3.70 0.1017 1.94 0.5229 624.64 11.53 631.29 17.41 655.17 67.73 624.64 11.53 95.34 RB-835-51 2.0779 1.64 0.1955 1.33 0.8119 1151.12 14.03 1,141.55 11.24 1,123.41 19.06 1,123.41 19.06 102.47 RB-835-52 0.6955 2.54 0.0875 1.91 0.7517 540.64 9.90 536.11 10.58 516.90 36.81 540.64 9.90 104.59 RB-835-53 7.3670 1.87 0.3972 1.77 0.9451 2156.06 32.45 2,156.98 16.75 2,157.83 10.68 2,157.83 10.68 99.92 RB-835-55 0.8756 3.25 0.1044 2.24 0.6889 640.24 13.65 638.61 15.41 632.84 50.75 640.24 13.65 101.17 RB-835-56 4.7913 2.51 0.3231 2.28 0.9074 1804.97 35.84 1,783.37 21.08 1,758.18 19.28 1,758.18 19.28 102.66 RB-835-57 0.8844 2.59 0.1057 1.01 0.3890 647.90 6.21 643.37 12.35 627.46 51.44 647.90 6.21 103.26 RB-835-58 0.8346 2.74 0.1008 1.16 0.4249 618.94 6.87 616.14 12.65 605.82 53.63 618.94 6.87 102.17 RB-835-59 0.8304 6.55 0.0987 4.09 0.6241 606.94 23.67 613.86 30.17 639.48 110.10 606.94 23.67 94.91

79

RB-835-60 0.6936 2.55 0.0863 2.11 0.8305 533.90 10.83 534.94 10.58 539.36 31.01 533.90 10.83 98.99 RB-835-61 0.6832 1.73 0.0853 1.14 0.6586 527.95 5.78 528.72 7.14 532.05 28.55 527.95 5.78 99.23 RB-835-62 1.1152 4.29 0.1251 2.18 0.5076 759.86 15.63 760.66 23.00 762.99 78.02 759.86 15.63 99.59 RB-835-63 4.6418 2.15 0.3094 2.03 0.9411 1737.83 30.89 1,756.82 18.00 1,779.47 13.29 1,779.47 13.29 97.66 RB-835-64 0.9266 2.84 0.1086 2.72 0.9564 664.36 17.17 665.85 13.89 670.88 17.75 664.36 17.17 99.03 RB-835-65 7.8298 1.87 0.3914 1.54 0.8261 2129.37 27.96 2,211.64 16.81 2,288.75 18.10 2,288.75 18.10 93.04 RB-835-66 1.7229 6.30 0.1710 1.08 0.1719 1017.53 10.20 1,017.10 40.52 1,016.18 125.91 1,016.18 125.91 100.13 RB-835-69 0.6989 4.38 0.0876 1.64 0.3740 541.56 8.50 538.13 18.28 523.62 89.05 541.56 8.50 103.43 RB-835-70 1.3413 10.05 0.1343 9.79 0.9741 812.54 74.74 863.79 58.52 997.66 46.19 997.66 46.19 81.44 RB-835-71 15.5583 1.36 0.5549 1.21 0.8898 2845.62 27.89 2,850.07 13.00 2,853.20 10.12 2,853.20 10.12 99.73 RB-835-72 1.6370 2.68 0.1653 1.28 0.4787 985.90 11.72 984.58 16.88 981.65 47.87 981.65 47.87 100.43 RB-835-73 1.2460 11.79 0.1377 6.35 0.5386 831.67 49.55 821.59 66.51 794.37 208.80 831.67 49.55 104.69 RB-835-76 0.6926 2.02 0.0859 1.64 0.8110 531.16 8.34 534.38 8.38 548.17 25.78 531.16 8.34 96.90 RB-835-77 0.7380 3.88 0.0914 1.36 0.3506 563.93 7.35 561.26 16.74 550.45 79.40 563.93 7.35 102.45 RB-835-78 0.6439 4.96 0.0819 3.16 0.6383 507.25 15.43 504.72 19.71 493.23 84.15 507.25 15.43 102.84 RB-835-79 0.6717 2.22 0.0848 1.64 0.7392 524.58 8.26 521.76 9.04 509.43 32.84 524.58 8.26 102.97 RB-835-80 0.6628 3.97 0.0835 1.37 0.3451 516.93 6.80 516.31 16.05 513.54 81.81 516.93 6.80 100.66 RB-835-81 1.6936 1.56 0.1670 1.15 0.7374 995.32 10.63 1,006.11 9.97 1,029.67 21.35 1,029.67 21.35 96.66 RB-835-82 0.7849 2.70 0.0948 1.99 0.7368 584.06 11.12 588.30 12.07 604.65 39.57 584.06 11.12 96.59 RB-835-82 0.6419 2.89 0.0818 1.59 0.5500 506.72 7.74 503.49 11.47 488.83 53.25 506.72 7.74 NA RB-835-83 0.7814 6.67 0.0932 4.27 0.6399 574.18 23.46 586.31 29.73 633.58 110.46 574.18 23.46 90.62 RB-835-84 0.6337 2.87 0.0801 2.64 0.9194 496.97 12.60 498.38 11.29 504.88 24.82 496.97 12.60 98.43 RB-835-85 0.7325 2.91 0.0901 2.36 0.8097 556.22 12.57 558.00 12.51 565.28 37.21 556.22 12.57 98.40 RB-835-86 0.8000 2.22 0.0969 1.81 0.8188 595.93 10.33 596.81 10.00 600.12 27.52 595.93 10.33 99.30 RB-835-87 0.5988 3.36 0.0762 1.74 0.5167 473.32 7.93 476.45 12.79 491.55 63.51 473.32 7.93 NA RB-835-88 23.2245 3.19 0.6046 3.19 0.9989 3048.44 77.52 3,236.40 31.11 3,355.02 2.31 3,355.02 2.31 90.86

80

RB-835-89 12.5969 2.19 0.5016 2.11 0.9608 2620.69 45.38 2,649.99 20.64 2,672.43 10.07 2,672.43 10.07 98.06 RB-835-90 0.6617 4.82 0.0838 4.32 0.8962 518.55 21.50 515.65 19.47 502.81 47.04 518.55 21.50 103.13 RB-835-92 4.8043 1.87 0.3076 1.70 0.9081 1729.04 25.73 1,785.66 15.70 1,852.46 14.14 1,852.46 14.14 93.34 RB-835-93 0.3894 6.21 0.0525 3.83 0.6177 330.00 12.34 333.91 17.67 361.19 110.17 330.00 12.34 NA RB-835-94 1.1174 3.19 0.1237 2.88 0.9018 751.79 20.41 761.72 17.10 790.92 28.95 751.79 20.41 95.05 RB-835-95 0.7330 2.14 0.0901 1.75 0.8202 556.37 9.34 558.33 9.18 566.36 26.61 556.37 9.34 98.24 RB-835-96 0.6930 6.08 0.0867 2.33 0.3836 536.27 12.01 534.58 25.28 527.37 123.20 536.27 12.01 101.69 RB-835-97 0.8663 2.68 0.1028 1.54 0.5742 630.73 9.23 633.54 12.61 643.63 47.07 630.73 9.23 97.99 RB-835-98 2.3704 2.54 0.2109 2.52 0.9938 1233.46 28.32 1,233.73 18.13 1,234.22 5.56 1,234.22 5.56 99.94 RB-835-99 0.5652 4.60 0.0744 2.98 0.6487 462.56 13.32 454.90 16.86 416.35 78.21 462.56 13.32 NA RB-835-100 5.8854 1.33 0.3515 1.27 0.9505 1941.83 21.25 1,959.08 11.58 1,977.34 7.39 1,977.34 7.39 98.20 RB-835-101 1.2033 3.92 0.1277 2.55 0.6503 774.66 18.62 802.09 21.75 879.04 61.65 774.66 18.62 88.13 RB-835-103 1.6934 7.16 0.1695 1.62 0.2260 1009.49 15.12 1,006.06 45.74 998.57 141.86 998.57 141.86 101.09 RB-835-104 1.1420 4.72 0.1253 4.15 0.8796 760.97 29.81 773.46 25.57 809.68 47.00 760.97 29.81 93.98 RB-835-105 0.7709 4.09 0.0943 2.58 0.6301 580.68 14.33 580.29 18.10 578.74 69.10 580.68 14.33 100.34 RB-835-106 0.6924 8.61 0.0864 2.67 0.3100 533.95 13.68 534.22 35.78 535.39 179.44 533.95 13.68 99.73 RB-835-107 1.8035 1.81 0.1776 1.69 0.9293 1054.01 16.39 1,046.72 11.85 1,031.51 13.56 1,031.51 13.56 102.18 RB-835-110 1.9183 1.43 0.1841 1.28 0.8934 1089.09 12.83 1,087.46 9.57 1,084.23 12.89 1,084.23 12.89 100.45 RB-835-112 0.7190 3.84 0.0899 1.93 0.5030 554.66 10.28 550.09 16.32 531.24 72.78 554.66 10.28 104.41 RB-835-114 2.8714 2.29 0.2382 1.84 0.8022 1377.50 22.78 1,374.45 17.24 1,369.70 26.31 1,369.70 26.31 100.57 RB-835-115 1.4349 3.01 0.1500 2.01 0.6684 901.17 16.91 903.58 18.00 909.46 46.05 909.46 46.05 99.09 RB-835-118 5.5409 1.69 0.3498 1.52 0.9041 1933.82 25.46 1,906.96 14.50 1,877.85 12.98 1,877.85 12.98 102.98

RB-835-119 0.7119 6.62 0.0890 2.91 0.4387 549.88 15.32 545.86 27.98 529.14 130.54 549.88 15.32 103.92 PA3 late Miocene Pisungo Formation (n = 94) PA3-15 0.8442 2.73 0.0985 1.87 0.6846 605.64 10.82 621.48 12.71 679.58 42.57 605.64 10.82 89.12

81

PA3-16 0.7278 1.30 0.0893 0.98 0.7517 551.39 5.17 555.26 5.56 571.19 18.64 551.39 5.17 96.53 PA3-17 0.8637 4.65 0.1031 1.60 0.3446 632.58 9.65 632.13 21.87 630.54 93.98 632.58 9.65 100.32 PA3-18 6.4779 2.10 0.3675 0.76 0.3616 2017.62 13.14 2,042.90 18.46 2,068.51 34.48 2,068.51 34.48 97.54 PA3-19 0.7935 2.46 0.0957 2.17 0.8802 589.44 12.21 593.15 11.06 607.35 25.28 589.44 12.21 97.05 PA3-20 20.6755 2.30 0.5712 2.29 0.9958 2912.89 53.60 3,123.50 22.25 3,261.80 3.32 3,261.80 3.32 89.30 PA3-22 0.1927 3.04 0.0285 2.44 0.8031 181.17 4.36 178.92 4.99 149.29 42.48 181.17 4.36 NA PA3-23 0.8295 2.66 0.1003 2.08 0.7798 616.30 12.20 613.35 12.26 602.45 36.07 616.30 12.20 102.30 PA3-24 0.6355 3.17 0.0809 1.94 0.6116 501.57 9.36 499.49 12.51 489.96 55.35 501.57 9.36 NA PA3-26 2.3252 1.39 0.2073 1.35 0.9670 1214.16 14.89 1,220.00 9.88 1,230.37 6.97 1,230.37 6.97 98.68 PA3-27 2.3887 1.20 0.2121 1.12 0.9320 1239.96 12.62 1,239.23 8.59 1,237.99 8.55 1,237.99 8.55 100.16 PA3-27 0.7030 6.45 0.0858 2.42 0.3749 530.82 12.32 540.57 27.04 581.87 129.96 530.82 12.32 91.23 PA3-28 0.6563 4.81 0.0812 1.16 0.2403 503.52 5.60 512.32 19.36 551.78 101.99 503.52 5.60 91.25 PA3-29 2.7241 2.11 0.2284 1.59 0.7531 1326.05 19.05 1,335.06 15.68 1,349.54 26.81 1,349.54 26.81 98.26 PA3-30 0.8934 2.85 0.1046 1.38 0.4836 641.48 8.42 648.21 13.66 671.72 53.39 641.48 8.42 95.50 PA3-31 0.6812 2.78 0.0845 1.75 0.6285 522.89 8.77 527.52 11.42 547.57 47.16 522.89 8.77 95.49 PA3-33 0.3759 9.04 0.0548 1.33 0.1472 344.11 4.46 324.00 25.09 181.87 208.71 344.11 4.46 NA PA3-34 5.4358 1.26 0.3408 0.96 0.7593 1890.47 15.68 1,890.52 10.81 1,890.57 14.76 1,890.57 14.76 99.99 PA3-35 0.8788 3.78 0.1051 1.02 0.2703 644.10 6.26 640.35 17.96 627.14 78.48 644.10 6.26 102.70 PA3-36 1.0648 7.35 0.1172 7.17 0.9757 714.44 48.50 736.18 38.51 802.90 33.76 714.44 48.50 88.98 PA3-37 3.0220 2.61 0.2443 1.85 0.7086 1408.98 23.41 1,413.20 19.92 1,419.54 35.21 1,419.54 35.21 99.26 PA3-38 0.8105 2.04 0.0980 1.13 0.5541 602.56 6.50 602.72 9.27 603.30 36.75 602.56 6.50 99.88 PA3-39 0.7300 4.27 0.0903 1.93 0.4511 557.19 10.29 556.56 18.31 554.00 83.26 557.19 10.29 100.58 PA3-40 0.9077 5.27 0.1057 2.63 0.4977 647.91 16.18 655.82 25.49 683.11 97.73 647.91 16.18 94.85 PA3-41 0.6834 4.61 0.0849 1.13 0.2444 525.29 5.69 528.81 19.01 544.04 97.80 525.29 5.69 96.55 PA3-42 2.3504 1.66 0.2081 1.60 0.9621 1218.86 17.72 1,227.68 11.81 1,243.23 8.86 1,243.23 8.86 98.04 PA3-43 1.1719 1.76 0.1281 0.82 0.4657 777.09 5.99 787.52 9.62 817.20 32.48 777.09 5.99 95.09

82

PA3-44 0.6906 2.81 0.0868 1.09 0.3873 536.59 5.60 533.17 11.64 518.53 56.81 536.59 5.60 103.48 PA3-46 11.9033 2.00 0.4469 1.97 0.9825 2381.66 39.17 2,596.82 18.76 2,769.22 6.12 2,769.22 6.12 86.00 PA3-47 0.7163 1.61 0.0880 1.04 0.6428 543.74 5.40 548.48 6.83 568.25 26.86 543.74 5.40 95.69 PA3-48 0.6613 4.15 0.0813 2.44 0.5889 504.17 11.84 515.39 16.76 565.41 73.03 504.17 11.84 89.17 PA3-49 1.8751 4.76 0.1824 3.64 0.7646 1079.87 36.17 1,072.33 31.52 1,057.06 61.77 1,057.06 61.77 102.16 PA3-50 0.7222 3.07 0.0894 1.16 0.3761 551.85 6.11 551.99 13.08 552.57 62.14 551.85 6.11 99.87 PA3-51 1.5183 3.13 0.1522 2.85 0.9119 913.15 24.29 937.81 19.16 996.18 26.08 996.18 26.08 91.67 PA3-52 1.7713 1.01 0.1717 0.76 0.7544 1021.65 7.21 1,035.01 6.57 1,063.39 13.36 1,063.39 13.36 96.07 PA3-53 0.6854 2.09 0.0839 1.46 0.6971 519.22 7.26 530.06 8.62 577.01 32.52 519.22 7.26 89.99 PA3-54 2.6472 2.09 0.2222 1.91 0.9139 1293.38 22.41 1,313.88 15.42 1,347.47 16.40 1,347.47 16.40 95.99 PA3-55 0.7942 1.92 0.0955 1.51 0.7836 588.12 8.48 593.57 8.65 614.42 25.85 588.12 8.48 95.72 PA3-56 0.9255 3.19 0.1074 2.00 0.6265 657.61 12.48 665.25 15.55 691.21 52.95 657.61 12.48 95.14 PA3-57 0.8437 2.39 0.1005 1.55 0.6469 617.32 9.12 621.20 11.13 635.35 39.29 617.32 9.12 97.16 PA3-58 0.7373 2.68 0.0904 1.58 0.5897 557.68 8.45 560.83 11.56 573.63 47.09 557.68 8.45 97.22 PA3-60 1.6664 2.10 0.1658 1.89 0.9031 988.89 17.36 995.80 13.31 1,011.02 18.25 1,011.02 18.25 97.81 PA3-61 1.8052 2.46 0.1744 2.04 0.8301 1036.22 19.52 1,047.33 16.06 1,070.61 27.53 1,070.61 27.53 96.79 PA3-63 0.6308 1.34 0.0799 1.07 0.8012 495.33 5.12 496.59 5.26 502.36 17.63 495.33 5.12 NA PA3-64 0.7115 3.13 0.0876 2.47 0.7913 541.52 12.85 545.65 13.20 562.89 41.64 541.52 12.85 96.20 PA3-65 0.6904 2.39 0.0858 1.65 0.6905 530.74 8.39 533.01 9.89 542.75 37.71 530.74 8.39 97.79 PA3-67 1.0661 3.41 0.1162 3.18 0.9319 708.79 21.33 736.83 17.87 823.04 25.82 708.79 21.33 86.12 PA3-68 6.8460 1.14 0.3873 1.11 0.9764 2110.42 20.02 2,091.69 10.10 2,073.28 4.34 2,073.28 4.34 101.79 PA3-70 5.3955 2.75 0.3402 2.64 0.9573 1887.74 43.14 1,884.14 23.59 1,880.17 14.34 1,880.17 14.34 100.40 PA3-71 0.0200 10.67 0.0030 4.94 0.4633 19.17 0.95 20.09 2.12 131.58 222.76 19.17 0.95 NA PA3-72 0.7295 3.22 0.0887 1.32 0.4091 547.75 6.92 556.24 13.79 591.15 63.73 547.75 6.92 92.66 PA3-73 0.1059 12.91 0.0150 2.83 0.2195 96.16 2.71 102.24 12.56 246.43 291.13 96.16 2.71 NA PA3-74 2.2493 2.23 0.2052 2.14 0.9561 1203.24 23.44 1,196.58 15.70 1,184.58 12.94 1,184.58 12.94 101.58

83

PA3-76 0.8408 1.14 0.1006 0.74 0.6477 617.66 4.33 619.60 5.27 626.68 18.67 617.66 4.33 98.56 PA3-77 1.9175 2.47 0.1846 2.27 0.9207 1092.15 22.81 1,087.19 16.46 1,077.29 19.31 1,077.29 19.31 101.38 PA3-80 0.8540 4.00 0.1020 2.71 0.6779 626.25 16.18 626.87 18.71 629.06 63.34 626.25 16.18 99.55 PA3-81 11.6994 0.75 0.4780 0.69 0.9231 2518.39 14.49 2,580.65 7.04 2,629.91 4.81 2,629.91 4.81 95.76 PA3-84 13.0500 1.78 0.5056 1.77 0.9935 2637.76 38.33 2,683.28 16.81 2,717.74 3.36 2,717.74 3.36 97.06 PA3-85 1.0584 4.09 0.1172 1.84 0.4494 714.18 12.44 733.01 21.37 791.00 76.75 714.18 12.44 90.29 PA3-87 6.6420 2.73 0.3521 2.29 0.8390 1944.50 38.49 2,064.95 24.12 2,187.38 25.86 2,187.38 25.86 88.90 PA3-87 7.0185 1.83 0.3739 1.67 0.9111 2047.94 29.27 2,113.77 16.28 2,178.43 13.14 2,178.43 13.14 94.01 PA3-88 11.9150 1.80 0.5066 1.61 0.8982 2642.21 35.01 2,597.75 16.84 2,563.25 13.22 2,563.25 13.22 103.08 PA3-89 6.4376 1.30 0.3643 1.20 0.9195 2002.50 20.63 2,037.41 11.45 2,072.93 9.02 2,072.93 9.02 96.60 PA3-90 0.7046 2.09 0.0873 1.42 0.6804 539.55 7.36 541.51 8.77 549.81 33.45 539.55 7.36 98.13 PA3-91 2.7440 4.22 0.2283 4.09 0.9698 1325.53 49.05 1,340.46 31.42 1,364.36 19.84 1,364.36 19.84 97.15 PA3-92 0.8674 1.17 0.1027 0.51 0.4337 630.34 3.05 634.14 5.52 647.72 22.65 630.34 3.05 97.32 PA3-93 0.5802 2.67 0.0744 0.75 0.2826 462.53 3.37 464.62 9.96 474.93 56.68 462.53 3.37 NA PA3-96 4.8656 2.00 0.3189 1.83 0.9145 1784.58 28.47 1,796.32 16.82 1,809.98 14.68 1,809.98 14.68 98.60 PA3-97 1.6660 3.25 0.1658 1.29 0.3962 988.84 11.80 995.67 20.62 1,010.71 60.50 1,010.71 60.50 97.84 PA3-99 1.4569 3.80 0.1482 3.58 0.9413 890.66 29.78 912.73 22.91 966.51 26.20 966.51 26.20 92.15 PA3-101 0.1719 6.20 0.0248 2.05 0.3306 157.94 3.20 161.04 9.23 206.88 135.79 157.94 3.20 NA PA3-103 0.8132 3.19 0.0980 1.77 0.5542 602.88 10.18 604.25 14.53 609.35 57.43 602.88 10.18 98.94 PA3-104 0.8502 3.49 0.1002 2.66 0.7628 615.81 15.64 624.74 16.29 657.19 48.42 615.81 15.64 93.70 PA3-105 0.6707 3.27 0.0848 1.26 0.3846 524.42 6.34 521.12 13.34 506.70 66.44 524.42 6.34 103.50 PA3-106 4.6635 2.84 0.3140 2.68 0.9419 1760.27 41.25 1,760.72 23.77 1,761.23 17.45 1,761.23 17.45 99.95 PA3-107 0.8252 6.52 0.1001 1.78 0.2723 614.93 10.42 610.94 29.95 596.17 136.06 614.93 10.42 103.15 PA3-108 0.9937 4.17 0.1135 2.22 0.5319 693.29 14.58 700.59 21.11 724.05 74.91 693.29 14.58 95.75 PA3-110 2.7149 2.31 0.2321 2.27 0.9840 1345.43 27.58 1,332.54 17.13 1,311.87 7.99 1,311.87 7.99 102.56 PA3-111 0.9376 2.98 0.1078 0.85 0.2845 660.07 5.32 671.61 14.64 710.48 60.73 660.07 5.32 92.91

84

PA3-113 11.8380 2.69 0.4482 2.67 0.9935 2387.14 53.31 2,591.67 25.19 2,755.68 5.04 2,755.68 5.04 86.63 PA3-114 0.4702 4.70 0.0630 2.03 0.4317 393.90 7.75 391.34 15.25 376.20 95.34 393.90 7.75 NA PA3-116 0.6734 3.70 0.0851 0.93 0.2509 526.64 4.70 522.79 15.12 506.01 78.85 526.64 4.70 104.08 PA3-118 1.1938 1.48 0.1318 1.25 0.8457 797.93 9.39 797.72 8.17 797.14 16.57 797.93 9.39 100.10 PA3-119 1.2599 6.53 0.1356 5.27 0.8075 819.46 40.58 827.86 36.98 850.49 80.10 819.46 40.58 96.35

PA3-120 6.5395 4.83 0.3714 2.27 0.4699 2036.15 39.65 2,051.23 42.59 2,066.40 75.25 2,066.40 75.25 98.54

85

Appendix 4. Detrital zircon U-Pb ages from McBride, 2008

A4. Detrital zircon U-Pb ages from McBride, 2008 Cambrian

Puncoviscana ± Cambria

Meson ± Carboniferou

s ± Jurassic Tacuru

Grp ± Cretaceous

Pirgua 1 ± Cretaceous Pirgua

2 ± 513 6 488 5 310 8 167 3 150 1 159 3 515 9 492 21 313 19 176 2 173 3 183 4 524 5 506 11 315 29 240 5 261 5 188 6 524 7 506 11 332 7 249 3 263 5 262 6 524 8 511 6 365 12 476 11 263 3 335 8 526 6 513 5 380 4 485 7 471 9 507 6 526 11 514 5 402 8 486 7 481 11 508 7 528 12 514 11 407 5 495 26 486 8 516 9 529 10 515 9 413 20 498 8 495 10 518 6 530 10 517 5 422 13 500 9 498 15 521 6 531 11 518 6 445 6 500 5 504 7 522 17 532 9 520 9 466 8 501 7 519 7 529 11 534 12 520 6 467 7 504 5 530 11 537 9 536 5 524 5 473 10 505 5 532 5 538 15 538 7 525 5 475 15 508 7 533 5 542 11 538 5 525 5 479 8 517 10 537 6 544 7 539 5 528 5 480 14 517 7 540 8 546 10 539 5 529 5 500 11 520 9 542 5 555 14 539 9 529 10 519 13 520 9 542 8 556 5 541 5 532 10 521 5 525 7 543 11 556 5

86

541 5 532 10 530 7 527 5 553 7 557 16 544 6 533 5 538 13 528 13 558 8 558 5 544 5 533 15 550 15 534 5 561 8 559 6 549 5 534 5 559 8 537 16 565 5 559 7 549 5 538 6 560 17 539 9 565 10 560 5 550 5 538 7 564 7 539 7 567 5 566 14 550 21 539 5 567 17 539 5 570 6 572 6 551 8 539 5 569 16 540 12 570 9 573 5 553 5 541 14 569 9 541 13 572 11 580 6 555 6 542 7 571 7 541 12 573 5 582 14 556 8 546 5 572 27 542 10 575 7 586 11 559 22 547 9 576 11 546 41 576 7 590 14 560 6 556 5 577 26 548 8 578 9 602 6 563 16 557 5 581 16 550 12 581 6 604 11 572 7 561 5 581 12 550 5 582 6 606 18 621 9 571 9 582 12 554 11 586 6 606 9 624 16 581 11 583 19 555 12 589 18 606 6 647 6 601 11 584 14 559 17 596 6 608 6 671 14 626 6 585 16 561 5 600 6 613 12 691 7 637 6 585 20 562 5 602 12 618 20 705 7 639 6 586 9 564 19 614 6 626 13 710 22 643 6 587 16 565 14 621 15 639 11 956 12 679 6 589 18 565 22 749 7 639 15 959 18 705 7 591 15 566 13 763 7 656 27

1006 45 706 8 593 9 568 13 847 11 656 6 1018 53 904 8 594 8 570 13 871 8 686 28 1024 78 1009 86 598 15 574 5 873 33 705 7

87

1027 20 1013 55 602 13 575 8 910 29 732 9 1030 85 1019 52 610 16 575 7 933 9 734 12 1037 65 1023 84 613 6 576 15 946 9 769 8 1040 57 1040 49 623 18 578 13 999 68 806 12 1043 76 1041 ## 635 9 581 6 1019 50 878 22 1044 31 1051 38 636 15 584 12 1021 31 890 15 1047 63 1059 48 644 10 585 16 1027 20 916 17 1047 47 1072 58 650 10 585 6 1031 40 920 20 1070 52 1085 29 669 21 588 32 1034 32 973 66 1072 70 1186 48 716 8 592 6 1036 35 1032 37 1080 35 1204 86 746 38 592 6 1045 62 1047 65 1098 48 1205 49 788 19 603 9 1046 74 1051 47 1109 58 1317 45 929 30 610 9 1094 89 1061 47 1116 56 1617 92 948 21 619 11 1095 25 1071 56 1121 32 1796 ## 1012 34 623 11 1099 20 1073 42 1123 69 1803 74 1029 33 635 15 1166 25 1074 60 1246 49 1921 63 1042 52 649 10 1179 40 1075 28 1260 68 1926 65 1047 43 679 6 1200 34 1087 44 1327 39 1943 58 1055 37 783 20 1208 26 1113 45 1786 58 1959 ## 1062 25 802 8 1417 67 1150 55 1994 70 1976 58 1083 42 806 10 1458 23 1175 ## 2060 47 1980 23 1144 ## 822 13 1750 44 1204 48 2153 70 1988 49 1154 27 874 33 1767 18 1356 ## 2473 34 2005 29 1296 33 952 20 1768 21 1367 45 2482 29 2033 31 1299 52 977 9 1789 23 1465 50 2642 52 2051 37 1422 20 982 9 1810 40 1484 34 2746 31 2078 52 1797 69 1035 34 1833 25 1490 94

88

2767 67 2093 38 1884 35 1069 43 1911 33 1506 50 2095 59 1919 24 1081 90 2116 33 1512 ## 2096 95 1987 47 1106 39 2680 20 1787 54 2109 53 2025 29 1109 57 2696 29 1976 45 2113 41 2306 38 1123 51 2925 16 2043 62 2128 20 2553 24 1156 37 2045 35 2133 41 2618 17 1250 45 2586 17 2163 32 2619 38 1444 61 2681 17 2171 46 2716 23 1867 51 2711 70 2173 53 2732 37 1897 24 3080 56 2193 55 3252 40 1981 57 2196 73 2005 18 2213 32 2064 34 2255 72 2088 22 2676 29 2161 31 3529 37 2215 18 3337 57

89

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