etters 247 (2006) 82–100www.elsevier.com/locate/epsl

Earth and Planetary Science L

Cenozoic orogenic growth in the Central Andes: Evidence fromsedimentary rock provenance and apatite fission trackthermochronology in the Fiambalá Basin, southernmost

Puna Plateau margin (NW Argentina)

B. Carrapa ⁎, M.R. Strecker, E.R. Sobel

Institut für Geowissenschaften, Universtität Potsdam, 14476 Golm, Germany

Received 10 November 2005; received in revised form 2 March 2006; accepted 6 April 2006

Editor: V. Courtillot

Abstract

Intramontane sedimentary basins along the margin of continental plateaus often preserve strata that contain fundamentalinformation regarding the pattern of orogenic growth. The sedimentary record of the clastic Miocene–Pliocene sequence depositedin the Fiambalá Basin, at the southern margin of the Puna Plateau (NW Argentina), documents the late Miocene paleodrainageevolution from headwaters to the west, towards headwaters in the ranges that constitute the border of the Puna Plateau to the north.Apatite Fission track (AFT) thermochronology of sedimentary and basement rocks show that the southern Puna Plateau was thesource for the youngest, middle Miocene, detrital population detected in late Miocene rocks; and that the margin of the PunaPlateau expressed a high relief, possibly similar to or higher than at present, by late Miocene time. Cooling ages obtained frombasement rocks at the southern Puna margin suggest that exhumation started in the Oligocene and continued until the middleMiocene. We interpret the basin reorganization and the creation of a high relief plateau margin to be the direct response of thesource–basin system to a wholesale surface uplift event that may have occurred during the late Cenozoic in the Puna–Altiplanoregion. At this time coeval paleodrainage reorganization is observed not only in the Fiambalá Basin, but also in different basinsalong the southern and eastern Puna margin, suggesting a genetic link between the last stage of plateau formation and basinresponse. However, this event did not cause sufficient exhumation of basin bounding ranges to be recorded by AFTthermochronology. Our new data thus document a decoupling between late Cenozoic surface uplift and exhumation in the southernPuna Plateau. High relief achieved at the Puna margin by late Miocene time is linked to Oligocene–Miocene exhumation; nosignificant erosion (<3 km) has occurred since in this arid highland.© 2006 Elsevier B.V. All rights reserved.

Keywords: plateau; sedimentary basin; provenance; thermochronology; exhumation; uplift; relief

⁎ Corresponding author.E-mail addresses: carrapa@geo.uni-potsdam.de (B. Carrapa),

strecker@geo.uni-potsdam.de (M.R. Strecker),sobel@rz.uni-potsdam.de (E.R. Sobel).

0012-821X/$ - see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.epsl.2006.04.010

1. Introduction

Orogenic plateaus, such as Tibet or the AndeanPuna–Altiplano region, are areas of high mean-surfaceelevation, which exert a fundamental influence on

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atmospheric circulation, precipitation patterns, andmodes of erosion and sedimentation. With 3700 maverage elevation, the arid, Andean Puna–AltiplanoPlateau of Argentina and Bolivia is the second largestplateau on Earth, after Tibet (e.g., [1]). Little is stillknown about the timing, patterns or mechanisms ofplateau formation. Paleoelevation and oxygen isotopedata available in the Bolivian Altiplano suggest thatmost of the plateau surface uplift may have occurred in

Fig. 1. DEM of the Puna–Altiplano plateau; thick dashed black and white linMaksaev and Zentilli [10]. White box shows the location of Fig. 2, the stCordillera between ca. 22 and 13 Ma is recorded by AFT from both detrcharacterized by AFT ages between 24±3 and 29±2 Ma ages [13]. CR: ChanSF: Sierra Famatina range, characterized by 47±4 Ma AFTage; SU and SM cand 253±8 AFT ages respectively [28]. Slc: Sierra de los Colorados area, wharea corresponds to coeval along strike deformation and exhumation between[61]. White dashed line corresponds to the extension to the north of the SieAmerica with elevations over 3000 m in gray modified after Horton et al. [7

the last 10 Ma [2–4]. However, the lack of quantitativedata for most of the extensive plateau region, especiallyin the south, has prevented the validation of thisscenario. Also, it is unclear how range exhumationand sedimentary basin architecture along the margin ofthe plateau would have responded to such an upliftevent.

Although many studies have focused on theformation of the Puna–Altiplano region, unresolved

e denotes area exhumed between 30 and 50 Ma, based on AFT data ofudy area. A: Angastaco Basin, where the exhumation of the Easternital samples [23] and from vertical profiles [61]. C: Calalaste range,go Real, characterized by AFT ages between 29±3 and 38±3 Ma [23].orrespond to Sierra Umango and Sierra Fertile, characterized by 147±6ere ca. 14 Ma detrital AFT population has been recorded [67]. Striped12 and 25 Ma, based on data from Carrapa et al. [13] and Deeken et al.rra Famatina range (SF). The inset figure shows the portion of South2].

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questions remain, including what uplift mechanism wasresponsible, and what spatial–temporal uplift patternswere characteristic of the evolution of this region (e.g.[1,5–7]). Recent data show that regional deformation ofthe present plateau region started in the Paleocene–Eocene in the Bolivian Altiplano (e.g. [6,8,9]) and in theCoastal Cordillera of Chile [10], and in the Eocene–Oligocene in the Puna Plateau and Eastern Cordillera ofArgentina [11–13]. In particular, structural data suggestthat most of the shortening occurred before the lateCenozoic [5,7,9,14,15]. If shortening and crustalthickening were the main driving mechanism for plateauuplift, a region with high elevation and/or high reliefmay have existed already at that time. Alternativemechanisms for plateau uplift include isostatic upliftfollowing lithospheric delamination [2,16,17], magmat-ic addition [15], underplating of material removed fromthe forearc by subduction erosion [18,19], and possiblythe flow of ductile lower crust from areas of excessshortening into areas that have a deficit of shortening[20,21]. Lithospheric delamination and ensuing whole-sale plateau uplift have been proposed to have occurredbetween 8 and 3 Ma [22] in the region of the present-daysouthern Puna Plateau. Sedimentological and thermo-chronological data from the southern Puna Plateau andthe Argentine Eastern Cordillera show that deformationdriving exhumation started already in Eocene–Oligo-cene time, contributing to the development of basincompartmentalization and eventually internal drainageconditions (e.g. [11,13,23]). However, it is not clearwhen the plateau reached geomorphic conditions similarto present, and if and how the attainment of such ageomorphic phenomenon is related to a wholesale, lateCenozoic tectonic uplift event.

In summary, different data sets from the Puna–Altiplano region and its margins suggest that wide-spread deformation and exhumation of individualranges had occurred already in Oligocene time in thepresent-day plateau realm, which may have beenfollowed by a surface uplift event in the Mio-Pliocene.The amount of exhumation related to these early events

Fig. 2. (A) Geological map of the Fiambalá Basin and surrounding regionQuaternary volcanics, 2) Mio-Pliocene volcanics (andesite–dacites), 3) Qumetamorphic rocks, 5) Paleozoic granites, 6) Triassic–Jurassic gabbros, 7)metavolcanites, 9) Cambrian phyllites, schists and metavolcanics, 10) Perm(Grupo Paganzo), 11) Ordovician granodiorites and minor gabbros, 12) MioFormation) and Quaternary, 14) late Miocene–Pliocene distal facies: a) Guanto the transect along which the stratigraphic sections were measured. Distal frectangle: northern vertical profile (Cerro Negro: CN); gray inset rectangle: eato sample UP78-9 (Sierra de las Planchades: Pl); light gray square corresponlisted in Table 1. (B) Simplified profile (A–A′) through the investigated sectformations; Q: Quaternary.

and the timing of the inferred last surface uplift are stillpoorly constrained. In particular, it is not clear whetherexhumation and surface uplift occurred at the same timeand were linked (i.e. were coupled).

Sedimentary rocks preserved within and along themargin of the Puna Plateau provide important informa-tion about the timing and potentially the processesresponsible for establishing the morphological featurescharacteristic of the present-day plateau. For example,sedimentary basins located within the present-dayplateau, such as in the Calalaste region (Fig. 1), recordthe direct response of drainage basin reorganization toexhumation of intra-basin ranges in Eocene–Oligocenetime [13]. Likewise, intramontane basins in the EasternCordillera, and in the transition between the ArgentineSierras Pampeanas province and the Puna, show asimilar response to the progressive unroofing ofbounding ranges that deform and exhume as the plateaugrows spatially and temporally along its margins (e.g.[11,24–26]).

With this study we aim to determine (1) whenexhumation occurred in the southern plateau marginand if and how it is related to previously proposedmechanisms; (2) whether exhumation was coupledwith a wholesale late Cenozoic surface uplift event;and (3) how such late stage plateau uplift wasreflected in the geological record. In particular, wepresent new sedimentologic and apatite fission track(AFT) thermochronologic data from Mio-Pliocenesedimentary rocks and from Paleozoic basementrocks from the southern margin of the Puna Plateauthat constrain the exhumation history and paleogeo-graphic evolution of this region with respect toplateau–margin growth. Our data document early tomiddle Miocene exhumation of the Puna Plateaumargin associated with the creation of high topogra-phy that provided sediments to the Fiambalá Basin byca. 6 Ma. This was coeval with an importantpaleogeographic reorganization and change in sedi-ment source regions, inferred to be the direct result ofwidespread plateau uplift.

(redrawn from the geological map of Catamarca, 1 :500,000 [73]): 1)aternary evaporites, 4) Cambrian–Ordovician volcanics (dacites) andPermo-Triassic granites, 8) Ordovician phyllites, gneiss, and minor

o-Triassic red sandstones, conglomerates, marls, and related volcanicscene (Guanchin and Tamberia formations), 13) Pliocene (Punashotterchin Formation, b) Punaschotter Formation. The black line correspondacies have been measure at the far NE end of this transect. White insetstern vertical profile (Alto Grande: AG); dark gray square correspondsds to sample UP78-3 (Filo Negro: FN). The ages of these samples areion in the Fiambalá Basin; T: Tamberia, G: Guanchin, P: Punaschotter,

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2. Geological setting

Our study area comprises the southernmost basementranges of the Puna Plateau margin, ca. 4000 m high, andthe adjacent Fiambalá Basin, a Cenozoic sedimentarybasin immediately to the south at ca. 1650 m elevation(Fig. 1). Deformation and exhumation of reverse-faultbounded basement ranges within and on the easternmargin of the present southern Puna began during theOligocene (e.g., [23,27]). AFT cooling ages fromwestern areas record deformation and exhumationcommencing during Eocene and early–middle Miocenetime, respectively [10,28]. To the southeast the Puna istransitional with the reverse-fault bounded SierrasPampeanas basement uplifts, a broken foreland provinceoverlying the flat subduction segment of the Nazca Platebetween 27° and 33°S latitude [29].

The arid Fiambalá Basin contains over 4 km of upperMio-Pliocene rocks belonging to the Tamberia, Guan-chin and Punaschotter formations [30] that record theexhumation and erosion of the surrounding ranges [31–34]. These sediments are distributed throughout theentire basin and reflect ephemeral braided fluvial andalluvial fan depositional environments [35]. The lack ofplant fossils and the presence of mud cracks, halite andgypsum layers [36] suggest that the depositionalenvironment was already arid at time of the Tamberiasediments deposition (ca. 8 Ma). To the west and north–northwest the basin margin mainly comprises Cambro-Ordovician dacites and sedimentary rocks, Paleozoic(Ordovician–Carboniferous) granites, Carboniferous,Permian and Triassic sedimentary rocks as well asTertiary and Quaternary volcanic rocks of predominant-ly andesitic composition [30]. To the northeast and eastthe basin is bounded mainly by Cambrian schists andphyllites and minor sectors with Ordovician–Carbonif-erous granites that constitute the southernmost end ofthe Puna Plateau (Fig. 2).

3. Methods

In order to constrain the exhumation history andpaleogeography of the southern Puna Plateaumargin andthe adjacent ranges during the late Cenozoic, we choosea multidisciplinary approach involving quantitativesedimentological investigations and thermochronologi-cal analysis using apatite fission track dating.

3.1. Sedimentary provenance

Sedimentary provenance analysis was carried out onsedimentary rocks from the Fiambalá Basin in order to

constrain the spatial–temporal evolution of the contribut-ing sediment sources. Sedimentological investigationswere conducted along a NE to SW transect (Fig. 2), theonly transect in the basin along which the completeCenozoic sequence is exposed; this includes the eastern-most outcrops in the basin, which record more distalsources. Clast composition analysis was performedthroughout the complete stratigraphic sequence at eighteenlocalities (Figs. 2 and 3). Pebbles of different lithologieswere counted every 5 to 10 cm (depending on granulo-metry) within a 50×50 cm2 grid. The grid was shiftedparallel to bedding until at least 100 clasts were counted ateach locality, for a total of over 1800 clast counts.

3.2. Apatite fission track thermochronology

Apatite Fission Track (AFT) thermochronology wasperformed on both basement rocks surrounding theFiambalá Basin and sedimentary rocks from the Cenozoicbasin sequence (detrital samples), in order to constrain thecooling and exhumation histories of the source areas aswell as the relationship between exhumation, relief,uplift, and sedimentation. AFT thermochronology pro-vides information on the timing and rates of coolingoccurring at temperature (T) between ca. 60 and 110 °C,defined as the Partial Annealing Zone (PAZ). The exact Tof the upper (hotter) boundary depends on the kineticcharacteristics of the apatites and the cooling rate; theformer can be quantified by measuring the diameter oftrack etch pits, known asDpar [37–39]. In general, apatiteswith smaller Dpar are typical of fluorine-rich apatite andare characterized by lower temperatures of the upperboundary. Fission track-lengths provide information onthe proportion of the cooling history that the sampleexperienced within the PAZ, and hence how quickly theapatite passed through the PAZ. Therefore, in order tointerpret the AFT data in terms of a T–t path an integratedanalysis of fission track age, track length distribution, andkinetic characteristics of the apatite grains is required.Samples were prepared and analyzed following theprocedure described by Sobel and Strecker [40].

About 20 grains for basement samples and 100 grainsfor detrital samples were dated (Table A1 in theAppendix). Confined track-lengths were measured inboth basement and detrital samples together with theangle between the confined track and the C-crystallo-graphic axis (C-axis projected data). Use of the angulardata mitigates track-measurement bias [41] andimproves annealing model results, as confined tracksanneal anisotropically as a function of orientation[37,38]. Apatite etch pit diameter (Dpar) and grainshape were also determined (Table A1 in the Appendix).

Fig. 3. Clast counts (see text for explanation) and simplifiedstratigraphic logs from the Fiambalá Basin. Paleocurrents are indicatedwith rose diagrams; the number of measurements is noted on the side.AFT detrital sample numbers shown in Fig. 6 are marked in italics.Depositional ages are based on magnetostratigraphy [31] and zirconfission track dating on ash layers [32]. Mrl: marls; fS: fine sandstones;mS: middle sandstones; mcg: micro conglomerate; cgl: conglomerates.

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Pooled ages are reported for the basement samples,calculated using the Trackkey program [42] (Table 1), asthey all pass the chi squared test [43,44]. For each detritalsample fission track grain-age distributions were decom-posed following the binomial peak-fit method [45]incorporated in the Binomfit program [46]. In automaticmode, the program provides an iterative search of peakages and number of peaks to find the optimal (best-fit)solution. The best-fit solution is determined by directlycomparing the distribution of the grain data to a predictedmixed binomial distribution. The related best-fit peaksare reported by age, uncertainty, and size (Table 2). Theuncertainty for the peak age is given at 95% confidenceintervals. The size of the individual peaks is reported as afraction (in percent) on the total (Table 2).

Basement samples were collected along two eleva-tion transects from basin bounding ranges to the northand east and from different ranges to the west of thebasin (Fig. 2). The vertical profiles were collected alongthe steepest possible routes between 2291 m to 4072 melevation (northeast, Cerro Negro – CN), and 2165 and3127 (east, Alto Grande – AG). Results from sevensamples from the CN profile are presented in Fig. 4 andTable 1. Unfortunately, only the lowest sample (2165 m)from the AG profile yielded sufficient apatite to provideresults (Table 1). Out of many samples collected to thewest of the basin only two, Sierra de las Planchadas (Pl;Fig. 2) and Filo Negro (FN; Fig. 2), yielded sufficientapatite to provide results. In total, we present resultsfrom ten basement samples and one cobble from thePunaschotter Formation (Table 1).

In addition, five detrital samples from the Tamberia,Guanchin and Punaschotter formations were selected forAFTanalysis (Table 2), representing ca. 1 sample perMaof depositional time. Assuming that the temperature inthe sedimentary basin was never high enough to over-print the original thermochronological signal (discussedin the following), detrital thermochronology providesfundamental information on characteristic cooling ages ofrocks originally present in the adjacent source (e.g.[47,48]) and the timing, rates and patterns at which theserocks were exhumed (e.g. [49–51]). Most detrital fissiontrack thermochronology studies have utilized zircons (e.g.[52,53]) while apatite has only rarely been analyzed (e.g.[54]). Only recently, detrital AFT analysis has beenrecognized as an important tool in resolving youngexhumation histories [11,55]. The advantage of analyzingapatite rather than zircon fission tracks is that the formermineral provides information on the thermal history ofshallower crustal levels due to the lower closuretemperature, thus enabling the identification of coolingevents in regions where little erosion has occurred. When

Table 1Apatite fission track analytical data of the NE vertical profile (VP) and single basement samples and pebble

Samplenumber

Lithology Elevation(m)

No.Xlsa

Rho-S(e5)b

NSc Rho-I(e5)b

NIc P(χ)2

(%)dRho-D(e5)e

NDf Age(Ma)

±1σ U(ppm)

Mean length(μm)

Dpar(μm)

S.D.

041B(UP61-10) VP (CN), granite, NE 4072 25 3.200 493 27.409 4222 90.15 10.771 4444 23.1 1.2 30.33 NA 1.8 0.3042B(UP61-12) VP (CN), granite, NE 3785 10 1.040 22 9.265 196 92.46 10.688 4444 22.0 5.0 10.69 NA 2.1 0.2042A(UP61-13) VP (CN), granite, NE 3463 20 1.193 141 12.356 1460 96.05 10.647 4444 18.9 1.7 14.02 NA 1.9 0.2042B(UP60-1) VP (CN), granite, NE 3190 22 0.418 45 5.356 576 84.08 13.232 5168 19.0 3.0 4.83 NA 1.8 0.2045A(UP60-2) VP (CN), granite, NE 2889 20 4.172 724 54.501 9458 0.09 13.144 51.68 18.4 0.8 52.00 14 ± 1.0 2.1 0.2046A(UP60-3) VP (CN), granite, NE 2584 20 2.880 547 46.752 8879 98.72 13.057 5168 14.8 0.7 44.29 NA 2.1 0.2048(UP60-4) VP (CN), granite, NE 2291 20 1.679 201 23.312 2791 60.8 12.97 5168 17.1 1.3 20.73 NA 1.9 0.2149(UP78-9) (P1), granite, W 2952 16 2.279 82 13.204 4775 89.6 11.037 4612 34.6 4.2 17.31 NA 1.8 0.3116-1(UP78-3) (FN), phyllite, W 4635 15 2.119 107 12.495 631 63.5 11.943 4612 43.9 4.4 15.32 NA 1.9 0.1161-1(UP79-5) Granite east (Alto Grande) 2165 20 0.621 69 8.429 939 11.33 9.7876 3922 13.1 1.7 12.18 NA 1.7 0.2177 (79-11) Granite cobble,

(Pliocene Punaschotter Fm.)1648 19 7.767 1310 16.186 2730 42.62 9.3689 3922 81.3 3.4 21.28 NA 1.9 0.1

AFT analytical data for the vertical profiles (VP), basement samples and pebble; the sample indicated in bold is the one modeled in Fig. 7.CN: vertical profile along the Cerro Negro (north-east); Pl: single sample from the Sierra de las Planchadas to the west; AG: single sample from a vertical profile along the Alto Grande to the east.Sample 177 is a cobble from the Punaschotter Formation (refer to Fig. 3). Samples analyzed with a Leica DMRM microscope with drawing tube located above a digitizing tablet and a Kinetekcomputer-controlled stage driven by the FTStage program [74].Analysis performed with reflected and transmitted light at 1250× magnification. Samples were irradiated at Oregon State University. Samples where etched in 5.5 M nitric acid at 21 °C for 20 s.Following irradiation, the mica external detectors were etched with 21 °C in 40% hydrofluoric acid for 45 min. The pooled age is reported for all samples as they pass the χ2 test, suggesting that theyrepresent a single population. Error is 1σ, calculated using the zeta calibration method [75] with zeta of 364.1±4.8 for apatite [unpublished data, 2006, B. Carrapa].a No. Xls is the number of individual crystals dated.b Rho-S and Rho-I are the spontaneous and induced track density measured, respectively (tracks/cm2).c NS and NI are the number of spontaneous and induced tracks counted, respectively.d (χ)2 (%) is the chi-square probability [45,76]. Values greater than 5% are considered to pass this test and represent a single population of ages.e Rho-D is the induced track density in external detector adjacent to CN5 dosimetry glass (tracks/cm2).f ND is the number of tracks counted in determining Rho-D. Dpar: fission track etch pit measurements, SD is the related standard deviation.

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Table 2Detrital populations of samples from the Fiambalá clastic sequence

Sample Approximate depostional age N P1 P2 P3 P4 P5 P6

Punaschotter 177 t<3.6 100 11.1±1 30.0±2.8 57.2±5.5 92.9±18.360.60% 23.5% 10.7%

Guanchin 053 3.6< t<5.7 129 14.0<1.5 36.3±3 81.7±7.9 127.1±10.6 217.5±92.125.10% 22% 15.50% 34.10% 3.30%

Guanchin 054⁎ 3.6< t<5.7 110 14.4±1.6 43.0±3.7 92.0±6.5 167.8±923.20% 32.10% 22.40% 22.20%

Tamberia 050⁎ 5.7< t<8 117 13.8±1.7 37.2±4.6 71.4±6.1 123.3±11.6 206.0±47.331.60% 23.70% 21.60% 19.10% 4%

Tamberia 003 5.7< t<8 108 49.7±4.6 121.9±12.257.30% 42.70%

⁎ Modeled samples in Fig. 6.

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applying detrital AFT thermochronology, a large numberof grains and related lengths must be analyzed in order toobtain a statistically significant representation of agespresent in the source region.

3.3. Track-length modeling

Track-length modeling was carried out on basementand detrital samples using the multikinetic annealingmodel AFTSolve [56] in order to better define theexhumation history of specific sediment sources and toconstrain the maximum degree of burial re-heating,respectively. In the latter case, modeling was performedon selected detrital populations from the stratigraphi-cally oldest (and deepest) samples 050 and 054 from theTamberia and Guanchin formations, respectively, forwhich enough data for modeling were available.Populations were selected for which sufficient lengthscould be associated with specific age grains, in order to

Fig. 4. Plot of AFT age versus elevation in km for basement samplescollected from the southern Puna margin (CN, see Fig. 2 for location andTable 1 for tabulated data); the grey sample (UP60-2) ismodeled in Fig. 7.

check on possible annealing due to burial-related re-heating. When modeling a specific age detrital popula-tion, an important issue is that the ages belonging to asingle population might be derived from a broadspectrum of possible sources that experienced similar,but not necessarily identical thermal histories. Further-more, a detrital apatite population is typically composedof a range of ages that may be derived from differentelevations within the same range. Consequently, thespectrum of lengths in a specific population may reflectboth multiple cooling events prior to exhumation andvariations due to different elevations of the source unit,potentially overprinted by re-heating due to burial andsubsequent cooling. Considering that multiple coolingevents may have affected the original source prior todeposition, correctly constraining this portion of thecooling path in the model is difficult. Therefore, it isclear that modeling detrital samples is challenging andmust be undertaken with caution. Therefore, we canonly make reasonable hypotheses about the thermalhistory of the original source prior to deposition in thebasin if independent geological constraints are available.

In the following section, track-length modeling isapplied to test hypotheses about the amount of re-heating experienced due to burial of the samples duringthe formation of the Fiambalá Basin. The initial timeconstraint is set at double (at least) the pooled age of thesample or detrital population to ensure that the first-formed tracks are all completely annealed, therebyavoiding potential boundary condition artifacts [56].

4. Results and discussions

4.1. Sedimentary evolution

Sedimentation in the Fiambalá Basin commencedbetween ca. 8 and 5.7 Ma with the deposition of theTamberia Formation [30,32]. It comprises massive,

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generally structureless sandstones, with occasionalplanar cross-bedded strata grading into well sorted,parallel bedded conglomerates toward the top (Fig. 3).The clast composition of the upper Tamberia Formationis characterized by dacitic volcanics and red sandstonesand minor andesitic volcanics; granites are also present.These lithologies, particularly the red sandstone clasts,are typical of Cambro-Ordovician and Permo-Triassicrocks from western sources. Granites are typical of bothwestern and north-eastern sources. Paleocurrent direc-tions measured in an imbricated conglomerate layer(Pc10), from the upper part of this formation, suggest afirst contribution from the north-east (Fig. 3).

The Guanchin Formation was deposited between ca.5.7 Ma and 3.6 Ma [32]. It comprises mainly trough andplanar cross bedded sandstones with occasional CaCO3

bearing paleosols and silicified tree trunks, alternatingwith conglomerate lenses with silt intraclasts. Towardthe top of the formation these rocks grade into coarsesandstones and conglomerates. The lower part of theGuanchin Formation is mainly composed of Ordoviciandacite clasts typical of western sources. The upper partof the Guanchin Formation is still dominated byvolcanic clasts. However, an increase in the abundanceof granite clasts in the upper Guanchin Formation withrespect to the underlying Tamberia Formation mayeither represent the progressive unroofing of westerncrystalline sources or/and an expansion of the sourcearea involving north-eastern granitic sources. Impor-tantly, distal facies of these sediments, exposed fartherbasinward, record the first unequivocal influx of schist/phyllite sourced in the southern Puna margin.

The Guanchin Formation is separated by an angularunconformity and overlain by the Punaschotter Forma-tion [32,34], which should be younger than 3.6 Ma [32].To date, no other radiometric ages are available for thesesediments in the Fiambalá Basin. The PunaschotterFormation consists of ca. 500-m-thick, disorganized andpoorly sorted conglomerates that are deeply incised andpreserved in isolated outcrops in the basin. Clast countsreveal a broad compositional variation, but with a largecomponent of the same Puna-related schist/phyllitelithologies found in the upper Guanchin Formation.Paleocurrent data measured on ca. 100 imbricated clasts

Fig. 5. Radial plots of detrital ages recorded in the Tamberia, Guanchin andautomatic mode using the Binomfit program of Brandon [46]. Mean Dpar valuplots shown in Ma; (L) denotes mean length. Arrows in sample 177 indicate ttext); histograms are provided for the lengths counted for each sample. Note twith previous studies; corrected values are indicated. The light gray area correblack line to the best fit.

(Pc19-20) from the easternmost preserved units clearlyrecord a provenance from the north–northeast (Fig. 3).

4.2. Exhumation history of the southern Puna revealedby apatite fission track thermochronology of basementsources

The ca. 1800 m AFT vertical profile (CN; Fig. 2)documents that basement rocks at the southern Punamargin passed through the partial annealing zone(PAZ: ca. 110°– 60° [57,58]) between 14.7±0.7 Maand 23.1±1.2 Ma (Fig. 4), from which an apparentmean exhumation rate of ca. 0.2 mm/yr can beinferred. This estimate neglects possible affects ofadvection; however, this is justified by the relativelyslow exhumation rate [59]. The onset of more rapidexhumation is represented by a break in slope on anage–elevation plot [60]. Unfortunately, this featureapparently occurred at an elevation above the presentlypreserved ridge crest and therefore can potentially onlybe preserved in the detrital record. Although wecannot determine the precise onset of more rapidexhumation, it must have been prior to ca. 24 Ma,when the highest elevation sample cooled through thePAZ. Length measurements were only possible onsample UP60-2 (2889 m) and yield an average valueof 14.5±1 μm.

A single sample from the eastern vertical profile(UP79-5), collected at 2165m, has a pooled age of 13.1±1.7 Ma (Fig. 2; Table 1). This age is remarkably similarto ages characteristic of the lower portion of the northernvertical profile, suggesting that the eastern basin-bounding range is the southward structural continuationof the southern Puna margin, and that eastern sources arecharacterized by early to middle Miocene ages (Fig. 2).A single granite sample (UP78-9) collected at 2952 mwest of the basin has a pooled age of 34.6±4.2 Ma (Fig.2; Table 1). A single sample of phyllite (UP78-3), fromthe west, yields a pooled age of 43.9±4.4 Ma (Fig. 2;Table 1). Both ages are in agreement with other agesreported from regions to the west and southwest [10,28]and document that these source regions were subject toan important Eocene–Oligocene cooling and exhuma-tion event.

Punaschotter formations and corresponding populations calculated ines and related standard deviations (S.D.) are provided). Ages on radialhe two components forming the binomial fitting curve (discussed in thehat lengths are in this case non-corrected for c-axis to allow comparisonsponds to acceptable fits, the dark gray area to good fits, and the dashed

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4.3. Detrital apatite fission track thermochronoloy

Using the Binomfit program on the five analyzeddetrital samples decomposes them into 2 to 5 compo-nents per sample. Examination of these componentssuggests that they belong to 6 discrete age groups(populations: P) (Table 2). Based on these age clusterswe assigned to the age populations P1 through P6. Thisimplies that a specific sample has only a subset of the 6possible populations; these population numbers are notalways consecutive. Table A1 in the Appendix containsraw data of all detrital samples including length and Dparvalues for each grain; mean length and Dpar values arepresented in Fig. 5.

In order to interpret detrital AFT ages in terms ofprovenance and/or cooling and exhumation events ofa specific sediment source we need to be able toexclude important annealing due to post-depositionalburial re-heating. Considering the total estimatedthickness of ca. 4 km of the Fiambalá Basin, post-depositional heating, annealing, and subsequent cool-ing are carefully addressed here. Several lines ofevidence strongly argue against significant burial-related annealing following deposition in the Fiam-balá Basin. Firstly, all detrital age populations areolder than the depositional ages and all samplescontain at least two discrete populations, indicatingthat none of the analyzed samples were subjected tototal or significant annealing after deposition. This isalso confirmed by the mean length trend that tends todecrease up-section (Fig. 5). If significant partialannealing due to burial induced re-heating hadoccurred, shorter track lengths in the bottom (deepest)sample would be expected. Secondly, the central agesincrease systematically down-section while the pop-ulation ages are relatively consistent, whereas partial-ly annealed samples would show the opposite pattern(Table 2; Fig. 5). Thirdly, the mean track lengthsobserved from the adjacent ranges, which are thelikely source of our sediments as indicated bysediment provenance data, are from 10 to 13 μm[28,61] and are very similar to the ones observed inthe detrital samples, indicating that no significantpartial annealing has occurred after deposition.

4.4. Estimation of annealing due to post burial heatingfrom heat flow density analysis

The calculation of the maximum amount of heatingrelated to burial is here attempted by first performingheat flow density analysis. Heat flow data are notavailable in the study area; however, data from Bolivia

[62], suggest that heat flow in the Eastern Cordillera isbetween 60 and 40 mW m−2 (Q0). We consider a rangeof plausible thermal conductivity values based onliterature (e.g., [63]); we apply values from 3.0 to2.0 W m−1 K−1 for the 4 km thick sandstones andconglomerates of the Fiambalá Basin. The followingsimplified equation, assumes thermal steady state and itis used to calculate the maximum temperature (T)beneath a sedimentary layer with 4 km thickness (zsed),assuming thermal steady state:

T ¼ Ts þ ðQ0zsed=KÞwhere Ts is the temperature at the surface (∼10 °C;Climatic Atlas of South America [64]), Q0 is the heatflow, zsed is the thickness of the sedimentary pile and Kis the thermal conductivity. Following this equation weobtain values between 63 °C (Q0=40 mW m− 2 andK=2) and 130 °C (Q0=60 mW m− 2 and K=3) forthe base of the stratigraphic sequence. It must be notedthat these values are obtained on a calculation based onthermal steady state and therefore can only be used asmaximum estimates of the re-heating caused by burial.

4.5. Thermal modeling of detrital populations:implications for maximum burial temperatures

Combined, the presented evidence documents thatannealing related to burial in the Fiambalá Basinplayed a minor role in the thermal history of the detritalsamples. However, thermal modeling of the P4population from sample 050 (Tamberia Formation)and sample 054 (Guanchin Formation) is presented inorder to further examine cooling following heating dueto burial between ca. 8 and 3.6 Ma (Fig. 6). T–tconstraints have been applied based on independentdata from the Sierra Pampeanas ranges presented byCoughlin et al. [28] and Jordan et al. [65]. AFT datafrom the Sierra Famatina range, directly to the west ofthe Fiambalá Basin (SF; Fig. 2), suggest that this rangeunderwent two phases of cooling: the first one betweenca. 40 and ca. 60 Ma and the second at ca. 10 Ma.Track length modeling suggests that a re-heating eventoccurred between these two cooling episodes [28]; thisre-heating is attributed to burial by a hypothesizedforeland basin sequence [28]. Isopach map reconstruc-tions and AFT data suggest that the Sierra Famatinarange, together with other ranges in the SierraPampeanas, were once covered by a thick pile ofsediments that were eroded in the Miocene during themain deformation and exhumation phase in this region[28]. In particular, farther south, at ca. 29°S, Jordan etal. [66] show the presence of a continuous foreland

Fig. 6. AFTSolve thermal modeling of population P4 in sample 050 and 054 from the Tamberia and Guanchin formations respectively. For T–tconstraints refer to the text. Lengths reported are corrected with respect to the c-axis for modeling purposes (see text for more details).

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basin at ca. 20 Ma; this may also have formerly beenpresent in the north. In accord with this geologicalevidence, a T constraint of 60–120 °C has been appliedat 2 Ma steps between 25 and 15 Ma to test thehypothesis of cooling following burial caused by thesediments of a foreland basin in the early Miocene(Fig. 6). The best solution was obtained at 18 Ma;acceptable and no fits were obtained when suchconstraint was not applied for samples 050 and 054,respectively.

Specific model input parameters for sample 050(Tamberia Formation) include a T constraint of 10–20 °C at ca. 8 Ma because the source for the Tamberiasediments must have been at the surface at the time ofsediment deposition; a T constraint of 40–70 °C at5.7 Ma was applied to test burial heating caused bydeposition of sediments belonging to the TamberiaFormation; a T constraint of 50–86 °C at ca. 3.5 Ma wasapplied to test burial heating caused by deposition ofsediments corresponding to the Tamberia, Guanchin andPunaschotter formations. Modeling results show that thebest fit for the maximum burial T experienced by thesample is ca. 60 °C (Fig. 6).

An additional modeling exercise was performed onthe P4 population from sample 054 from the GuanchinFormation, stratigraphically above sample 050 (Figs. 3and 6). The same general T–t constraints as for sample050 were used. A T constraint of 10–20 °C was appliedat ca. 5.5 Ma and one at 35–72 °C was applied at ca.3.5 Ma to test burial heating caused by deposition ofGuanchin and Punaschotter sediments. Our modelingresults show that the best fit for the maximum burial Texperienced by the sample is less than 60 °C (Fig. 6).These results support the evidence presented above,documenting negligible annealing due to post-deposi-tional burial in the Fiambalá Basin.

A possible explanation for this negligible amount ofburial-heating annealing during the evolution of theFiambalá Basin could be the combination of a relativelylow and/or unsteady heat flow and syn-depositionaldeformation. This last could have involved migration ofthe basin depocenter during thrust propagation andformation of growth strata. Such processes might haveprevented the clastic sequence from ever reaching athickness of ca. 4 km. Lack of seismic data and 3Doutcrops prevent us from holding such a scenario as the

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sole responsible mechanism; however, evidence of syn-sedimentary deformation in the Fiambalá Basin maysupport this hypothesis [35].

Interestingly, a similar example of minimally resetdetrital samples analyzed from a ca. 6-km-thickstratigraphic sequence in the Angastaco Basin, north-east of the study area (Fig. 1), also documentsnegligible annealing associated with post-depositionalre-heating. A combination of scenarios, similar tothose discussed here, was invoked to explain observa-tions there [11].

4.6. Implications for provenance and sediment sourcerock exhumation

The detrital thermochronologic data obtained fromthe Tamberia, Guanchin, and Punaschotter formationsin the Fiambalá Basin provide important insights intothe evolution of the paleogeography of the surround-ing ranges. Below, we interpret the detrital agepopulations in terms of provenance proxies and asrepresenting cooling and exhumation events of thesediment source.

Sample 003 from the lower part of the TamberiaFormation has two main age populations (P): 121.9±12.2 and 49.7±4.6 Ma, respectively (Fig. 5). Sample050 from the upper part of the Tamberia Formationpresents a wider age spectrum with five populations:206.0±47.3, 123.3±11.6, 71. 4±6.1, 37.2±4.6, and13.8±1.7 Ma. While older populations are similar tothe first sample, the youngest middle Miocenepopulation (P1; Table 2) suggests that a new, differentsource terrain began contributing sediment to theTamberia Formation at about 5.7 Ma. Sample 054from the lower part of the Guanchin Formationcontains age populations of 167.8±17.8, 92.0±12.8,43.0±7.2, and 14.4±3.1 Ma. Sample 053 from theupper member of the Guanchin Formation is charac-terized by age populations of 217.5±194.2, 127.1±21.0, 81.7±15.5, 36.3±5.8, and 14.0±2.8 Ma. Sample177 from the distal Punaschotter Formation (locationPc19 in Fig. 3) contains age populations of 92.9±18.3,57.2±5.5, 30.0±2.8, and 11.1±0.9 Ma. A singlegranite cobble, from the same location as the sandstonesample 177, records a pooled age of 81.3±3.4 Ma(Table 1). Paleocurrent measurements from thislocation unambiguously show provenance from theN–NE (Fig. 3). The Punaschotter Formation reflects asignificant contribution (60%) of middle Miocene ages(P1). P1 from sample 177 is slightly younger comparedto P1 of the underlying samples. However, detailedexamination of the youngest grains in sample 177

suggests volcanic contamination, responsible for mak-ing P1 in sample 177 younger (see Table A1 in theAppendix) compared to other samples. Indeed, theGaussian distribution (Fig. 5) shows that the binomialfitting curve contains two components, at ca. 10 and15 Ma. The younger one could denote contaminationfrom reworked ashes while the older one is closer inage to P1 detected in other samples.

Jurassic and Eocene ages are characteristic ofwestern sources (e.g., [10,28]). Such a source is alsosupported by the late Eocene age recorded in samplesUP78-9 and UP78-3, collected immediately west of thebasin. However, Eocene ages are also characteristic ofeastern sources, as shown by sample 177 (sandstonematrix of conglomerate) from the Punaschotter Forma-tion. The Punaschotter conglomerates at this location arederived from the east as indicated by paleocurrent data(Fig. 3).

A Late Cretaceous age recorded by a single granitecobble derived from the east in the distal PunaschotterFormation (sample 177, location Pc19; Fig. 3) may alsorepresent an easterly source. Cretaceous cooling ages inthis region are typical of eastern sources that have beeninfluenced by events in the vicinity of the CretaceousSalta Rift, such as sectors including the EasternCordillera further north [61] and parts of the northernSierra Pampeanas [40].

In contrast, middle Miocene ages, as recorded in theP1 population are more typical of sources located withinthe southern portion of the Puna Plateau (e.g. [61]) (Fig.1). Grains recording the youngest detrital Miocenepopulation (ranging between 11.1 and 14.4 Ma) aregenerally rounded and not as translucent as volcanicallyderived crystals, but are instead more typical of grainsderived from crystalline basement rocks. This suggeststhat this age population represents an exhumation signalrather than a Miocene volcanic input (i.e. from ashes).Although a limited amount of ash contamination may bepotentially present in the Punaschotter Formation, thiswould not significantly alter the main population age.Grains derived from unconsolidated volcanic sources(i.e. ash flow) are typically euhedral and translucent (seeTable A1 in the Appendix). In particular, similar detritalmiddle Miocene ages (P1) have been detected in theSierra de los Colorados area, immediately southwest ofthe study area (Slc in Fig. 1), and are considered torepresent the exhumation of southern Puna sources [67],thus corroborating our interpretation. In particular thelower part of the northern vertical profile is characterizedby ages typical of middle Miocene detrital population(P1). A sample from the AG range to the east of the basin,at a similar elevation as the lower samples of the CN

Fig. 7. AFTSolve thermal modeling of basement sample UP60-2 (2889 m; lower part of the northern vertical profile), indicated in grey in Fig. 4 and inbold in Table 1. The model was initiated at 200 Ma at T>180 °C; T constraints of 170–90 °C, 140–60 °C and 17–70 °C were applied at 24 and 15 Maand 8 Ma, respectively, to examine cooling indicated by the age–elevation profile (Fig. 4) and the possibility that this part of the range might havebeen at the surface by late Miocene time. Lengths reported are corrected for c-axis for modeling purposes. Refer to text for more details. The lightgray area corresponds to the acceptable fit, the dark gray area to the good fit and the dashed black line to the best fit. Note that lengths are correctedfor c-axis for modeling purposes explained in the text.

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profile, shows similar middle Miocene ages, suggestingthat the two ranges have similar exhumation historiesand that they are not separated by major structures. Thus,we hypnotize that rocks from structural positions similarto the lower part of the northern and eastern verticalprofiles were the likely source for P1, first detected in theupper Tamberia Formation (ca. 6 Ma). This is supportedby paleocurrent data from ca. 6 Ma strata documentingthe first input from northeastern sources at this time (Fig.3). The same P1 detrital age population prevails insamples from the Guanchin Formation. The compositionof this unit in turn is similar to the sediments from thePunaschotter Formation, which is clearly sourced fromthe southern Puna margin. By the time the GuanchinFormation was deposited (3.6< t<5.7 Ma), the sedimentsource had thus evolved toward the north, suggestingthat rocks from the vicinity of the northern profilesupplied sediments. In order to test the hypothesis thatthe range to the northeast of the basin (CN verticalprofile) was the source for P1 in the Fiambalá sedimentstrack length modeling on a sample from the lower part ofthe vertical profile is performed in the following.

4.7. Track length modeling of the northern verticalprofile: implications for the creation of a high reliefplateau margin

The AFT ages and track-length modeling from thebasement profile from the southern Puna margin suggestthat this area was exhumed during the early–middleMiocene. Thermal modeling was performed on sampleUP60-2 (Fig. 7). The model was initiated at 200 Ma atT>180 °C; T constraints of 170–90 °C and 140–60 °C

were applied at 24 and 15 Ma, respectively, to examinecooling indicated by the age–elevation profile (Fig. 4).In order to test the hypothesis that the lower part of therange was exposed by late Miocene time, a T constraintbetween ca. 17 and 70 °C was applied at different timesfrom 10 to 6 Ma at intervals of 2 Ma. The best run wasobtained with the T constraint at 8 Ma and shows that thesample could have cooled below ca. 60 °C by ca. 8 Ma.We hypothesize that rocks characterized by ca. 14 Maages were at the surface by ca. 6 Ma based on the modelof landscape development shown in Fig. 8. The regionbetween the vertical profile and the Fiambalá Basin doesnot contain any mapped structures; therefore, exhuma-tion on this flank of the range must occur by acombination of rock uplift and headward erosion,requiring the exhumation path to approach the surfaceobliquely. However, isochrons representing the layer ofrock that passed through the ca. 110 °C closure isothermat a particular time extend subhorizontally; rocks withroughly the same age as the base of the profile would beexposed on the flank of the range prior to exposure of theparticular rock that was sampled. As headward erosionremoved the flank of the range, the area representing thevertical profile continues to cool as it approaches thesurface; rock uplift due to the isostatic response toerosion will continue even after tectonism has ceased.Alluvial fans sourced from the growing topography willonlap the eroding flank of the range.

5. Conclusions

Provenance and thermochronologic data from theFiambalá Basin at the southern margin of the Puna

Fig. 8. Schematic depiction of the exhumation pathways followed by the 1.8 km vertical profile at 3 time steps. Please note that the figure is not atscale. For simplicity, surface topography is depicted as being in a steady state; dash lines represent the topography at various t-stages. Stars representthe AFT sample locations; light grey swath represents position of the apatite partial annealing zone (PAZ). Lower temperature isotherms are morestrongly warped due to topographic effects [59]. 14 and 17 Ma isochrons depicts layers of rock that passed through the lower portion of PAZ. Notethat these are approximation values from the P1 population (ca. 14 Ma) and the pooled age of sample UP60-2 (Fig. 5). The 17 Ma AFT sample (blackstar) crosses 60 °C isotherm at 8 Ma; by 6 Ma, samples with 14 Ma fission track age are exposed at the surface and deposited in the adjacent basin. Atthis time, the relief must be at least 1.8 km. Curved grey arrows show cooling paths for the lowest and highest samples of the vertical profile; curvaturewith respect to the surface is caused by effects of headward erosion and rock uplift. Sedimentary basin progressively onlaps topography as flank ofrange retreats from the depocenter.

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Plateau show that late Miocene–Pliocene sedimentaryrocks preserved in the basin are derived from theprogressive exhumation and erosion of the basin-bounding ranges. This was coupled (i.e. contempora-neous and genetically linked) with a northward shift inthe evolution of the paleo-drainage system. Initially,the primary source of the Tamberia Formation (ca.

8 Ma) was located to the west, in the Precordillera.With the deposition of the upper Tamberia (sample050) and Guanchin formations (3.6< t<5.7 Ma), a shiftof the source towards the north–northeast is recordedby paleocurrent data and by the first appearance ofclast lithologies typical of the present-day southernmargin of the Puna Plateau.

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Our thermochronological data document that rocksthat supplied middle Miocene detrital apatites to theupper Tamberia and Guanchin strata must have beenexposed at surface at about ca. 6 Ma. Middle Miocenecooling ages are only characteristic of basement rocksthat constitute northern and eastern source areas. Inparticular, 14 Ma ages are characteristic of the lowestpart of the vertical profile to the north, this suggests thatthis structural level of the range (ca. 2300 m) was at thesurface at ca. 6 Ma. Consequently, at least the entirecrustal column that presently overlies this sample (crestalelevation of 4072 m) must had also been exhumed bythen (Fig. 8). The crestal elevation is a minimumestimate, as there has likely been erosion during the last6 Ma. Moreover, the fact that the same ages recorded inthe 6Ma basin strata are still recorded by the range to thenorth suggests that not enough tectonic and or erosionalexhumation has occurred since then to be recorded by theAFT system. Assuming 60 °C as the upper limit of thePAZ, a mean surface temperature of ca. 10 °C and aconservative 20 °C/km paleo-geothermal gradient, lessthan 3 km of upper crust would have been exhumed byerosion since middle Miocene time.

Our data show that the southern margin of the PunaPlateau expressed an high relief by late Miocene time,when sedimentary strata hosting AFT detrital ages of14 Ma (P1) were deposited in the Fiambalá Basin.Rocks of the northern and eastern ranges that providedsediments to the basin in late Miocene time arepresently at ca. 2300 m. Although our new data mayindicate a relief similar or higher than present in thesource region during the latest Miocene, they do notprovide direct information on absolute paleo-eleva-tions. Instead, our data may document a minimumcrestal height of ca. 1800 m above the elevation of theFiambalá Basin at that time. However, more detailedinformation on paleo-elevation and relief conditions arenot available for this region in order to further constrainthe paleo-geographic evolution. Paleo-elevation proxiesfrom the Bolivian Altiplano have been used to suggestthat present plateau elevations further north may havebeen acquired within the last 10 Ma [2–4], implying arapid uplift event subsequent to the main phase ofshortening and crustal thickening. Indeed, this timingfor wholesale plateau uplift broadly coincides with aninferred isostatic uplift event following mantle delam-ination in the southern Puna Plateau sometime between8 and 3 Ma [16,17].

Interestingly, sedimentologic, thermochronologic,paleontologic, and oxygen-isotope data in Mio-Pliocenesedimentary sequences deposited in other intramontanebasins along the eastern margin of the Argentine Puna

Plateau record a similar paleogeographic reorganizationwith evolution of headwaters from the west to the northand north–east [11,24,25,68,69]. In particular, in theneighboring El Cajon Basin (Fig. 1), a reorganization ofthe source and basin depositional environment isrecorded by both seismic reflection and thermochrono-logical data at ca. 6 Ma and is interpreted to result fromplateau–margin growth [13].

Cooling ages from basement ranges in the southernPuna Plateau and detrital AFT data from adjacentintramontane basins [11,13] suggest that the mainphase of exhumation was prior to a late Miocene–earlyPliocene event during which significant changesoccurred in paleo-drainage conditions. In particular,our data suggest that range uplifts existed at thepresent-day southern Puna margin by late Miocenetime and were the result of Oligo-Miocene distributedshortening and exhumation [13]. This is in agreementwith data from the Eastern Cordillera of Argentina tothe northeast [61] and the Bolivian Altiplano [70]. If agenetic link between shortening, crustal thickening,exhumation, and uplift, exists, then a high-elevationand/or high relief region may already have been inplace in the Puna region by Oligo-Miocene time.Although not recorded by AFT, there certainly hasbeen some amount of rock uplift since then, asdocumented by regional paleo-drainage reorganizationand Pliocene reverse faulting observed in the FiambaláBasin and other intramontane sedimentary basins alongthe plateau margin [11,25,71].

Thus, while reverse-fault bounded ranges andintervening, internally drained basins are a typicalfeature of the present-day plateau morphology, thefoundation for this setting may already have beenattained in Oligo-Miocene time. The filling of thesebasins and consequent reduction of local relief withinthe present plateau region also began at that time and hascontinued since then. However, the pronounced changesat the immediate eastern and southern plateau margin inlate Miocene–early Pliocene time suggest that wholesaleplateau uplift may have affected this region, subsequentto the earlier period of distributed shortening and crustalthickening. This younger event is not reflected in theAFT data, presumably due to the arid climate andassociated reduced erosion rates in the Puna region; thesouthern Puna Plateau margin has experienced less thanca. 3 km exhumation since the middle Miocene.

Acknowledgements

We thank Glen R. Murrell for his fundamental helpwith part of fission track analysis, A. Villanueva Garcia

98 B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100

and J. Sosa Gomez for their hospitality and help in thefield. We appreciate the constructive reviews of twoanonymous reviewers as well as the useful comments ofTeresa Jordan on an earlier version of this manuscript.The Alexander von Humboldt Foundation is kindlyacknowledged for supporting B. Carrapa's research atPotsdam. We thank the German Science Foundation forfinancial support (Leibniz-Prize to M. S.) as well as theA. Cox Fund (M.S.), Stanford University.

Appendix A. Supplementary data

Supplementary data associated with this article canbe found, in the online version, at doi:10.1016/j.epsl.2006.04.010.

References

[1] B. Isacks, Uplift of the central Andean plateau and bending ofthe Bolivian orocline, J. Geophys. Res. 93 (1988) 3211–3231.

[2] C. Garzione, P. Molnar, J. Libarkin, B.J. MacFadden, Rapid lateMiocene rise of the Bolivian Altiplano: evidence for removal ofmantle lithosphere, Earth Planet. Sci. Lett. 241 (3–4) (2006)543–556.

[3] P. Ghosh, C.N. Garzione, J.M. Eiler, Rapid uplift of the Altiplanorevealed through 13C–18O bonds in paleosol carbonates, Science311 (5760) (2006) 511–515.

[4] K.M. Gregory-Wodzicki, Uplift history of the Central andNorthern Andes: a review, Geol. Soc. Amer. Bull. 112 (2000)1091–1105.

[5] R. Allmendinger, T. Jordan, S. Kay, B. Isacks, The evolution ofthe Altiplano–Puna Plateau of the Central Andes, Annu. Rev.Earth Planet. Sci. 25 (1997) 139–174.

[6] P. DeCelles, B.K. Horton, Early to middle Tertiary foreland basindevelopment and the history of Andean crustal shortening inBolivia, Geol. Soc. Amer. Bull. 115 (1) (2003) 58–77.

[7] N. McQuarrie, Initial plate geometry, shortening variations, andevolution of the Bolivian orocline, Geology 30 (10) (2002)867–870.

[8] K. Elger, O. Onken, J. Glodny, Plateau-style accumulation ofdeformation: Southern Altiplano, Tectonics 24 (2005),doi:10.1029/2004TC001675.

[9] B.K. Horton, Revised deformation history of the central Andes:inferences from Cenozoic foredeep and intramontane basins ofthe Eastern Cordillera, Bolivia, Tectonics 24 (2005),doi:10.1029/2003TC001619.

[10] V. Maksaev, M. Zentilli, Fission track thermochronology of theDomeyko Cordillera, Northern Chile: implications for Andeantectonics and porphyry copper metallogenesis, Explor. Min.Geol. 8 (1) (2000) 65–89.

[11] I. Coutand, B. Carrapa, A. Deeken, A.K. Schmitt, E. Sobel, M.R.Strecker, Orogenic plateau formation and lateral growth ofcompressional basins and ranges: insights from sandstonepetrography and detrital apatite fission-track thermochronologyin the Angastaco Basin, NW Argentina, Basin Res. 18 (2006)1–26.

[12] A. Deeken, E.R. Sobel, M.R. Haschke, M.R. Strecker, U. Riller,Age of initiation and growth pattern of the Puna Plateau, NW-

Argentina, constrained by AFT thermochronology, 10th Interna-tional Fission Track Conference electronic volume, 2004,pp. 82–83, Amsterdam.

[13] B. Carrapa, D. Adelmann, G.E. Hilley, E. Mortimer, E. Sobel, M.R. Strecker, Oligocene range uplift and development of plateaumorphology in the southern central Andes, Tectonics 24 (2005)1–19.

[14] B.K. Horton, P. DeCelles, The modern foreland basin systemadjacent to the Central Andes, Geology 25 (1997) 895–898.

[15] S. Lamb, L. Hoke, Origin of the high plateau in the CentralAndes, Bolivia, South America, Tectonics 16 (1997) 623–649.

[16] S. Kay, The Andean margin—a major site for the destructionof Phanerozoic crust and mantle lithosphere, InternationalGeological Conference Electronic Abstract Volume, Florence,2004.

[17] S.M. Kay, B. Coira, J. Viramonte, Young mafic back-arc volcanicrocks as indicators of continental lithospheric delaminationbeneath the Argentine Puna Plateau, Central Andes, J. Geophys.Res. 99 (B12) (1994) 24323–24339.

[18] M. Schmitz, A balanced model of the southern Central Andes,Tectonics 13 (1994) 484–492.

[19] P. Baby, P. Rochat, G. Mascle, G. Hérail, Neogene shorteningcontribution to crustal thickening in the back-arc of the centralAndes, Geology 25 (1997) 883–886.

[20] J. Kley, C.R. Monaldi, Tectonic shortening and crustal thicknessin the Central Andes: how good is the correlation? Geology 1998(26) (1998) 723–726.

[21] X. Yuan, S.V. Sobolev, R. King, O. Oncken, New constraints onsubduction and collision in the central Andes from P to Sconverted seismic waves, Nature 408 (2000) 958–961.

[22] S. Kay, C. Mpdozis, Magmatism as a probe to the Neogeneshallowing of the Nazca plate beneath the modern Chilean flat-slab, J. South Am. Earth Sci. 15 (1) (2004) 39–57.

[23] I. Coutand, P.R. Cobbold, M. de Urreiztieta, P. Gautier, A.Chauvin, D. Gapais, E.A. Rossello, O. Lòpez-Gamundí, Styleand history of Andean deformation, Puna Plateau, NorthwesternArgentina, Tectonics 20 (2001) 210–234.

[24] G.E. Hilley, M.R. Strecker, Processes of oscillatory basin fillingand excavation in a tectonically active orogen: Quebrada delToro, NW Argentina, Geol. Soc. Amer. Bull. 117 (7/8) (2005),doi:10.1130/B25602.1.

[25] E. Mortimer, B. Carrapa, I. Coutand, L. Schoenbohm, J. SosaGomez, E. Sobel, M.R. Strecker, Sedimentary basin compart-mentalisation in response to diachronic thrusting in the SierraPampeanas basin and range domain: El Cajon–Campo Arenalbasin, NW Argentina, Geol. Soc. Amer. Bull., submitted forpublication.

[26] M.R. Strecker, P. Cerveny, A.L. Bloom, D. Malizia, LateCenozoic tectonism and landscape development in the forelandof the Andes: Northern Sierras Pampeanas (26°–28°), Argentina,Tectonics 8 (3) (1989) 517–534.

[27] D. Adelmann, Känozoische Beckenentwicklung in der südlichenPuna am Beispiel des Salar de Antofolla (NW-Argentinien), FreiUniversitäat, Berlin, 2001.

[28] T.J. Coughlin, P.B. O'Sullivan, B.P. Kohn, J.H. Rodney, Apatitefission-track thermochronology of the Sierras Pampeanas, centralwestern Argentina: implications for the mechanism of plateauuplift in the Andes, Geology 26 (11) (1998) 999–1002.

[29] T.E. Jordan, B.L. Isacks, R.W. Allmendinger, J.A. Brewer, V.A.Ramos, C.J. Ando, Andean tectonics related to geometry ofsubducting Nazca Plate, Geol. Soc. Amer. Bull. 94 (1983)341–361.

99B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100

[30] G. Turner, Descripcion geologica de la Hoja 13b, Chaschuil,Provincias de Catamarca y la Rioja, Bol. Dir. Nac. Geol. y Min.106 (1967) 0–78.

[31] K.T. Tabutt, Fission Track Chronology of Foreland Basins, Inthe Eastern Andes: Magmatic and Tectonic Implications,Master thesis, Dartmouth College, Hanover, New Hampshire,1986, p. 100.

[32] J.H. Reynolds, Chronology of Neogene Tectonics in WesternArgentina (27°–33°S) Based on the Magnetic PolarityStratigraphy of Foreland Basin Sediments, Ph.D. thesis,Dartmouth College, Hanover, New Hampshire, 1987, p. 100,p. 353.

[33] T.E. Jordan, R.N. Alonso, Cenozoic Stratigraphy and Basintectonics of the Andes Mountains, 20°–28° South Latitude, Am.Assoc. Pet. Geol. Bull. 71 (1987) 49–64.

[34] W. Penck, Der Südrand der Puna de Atacama. Ein Beitrag zurKenntnis des andinen Gebirgstypus und zur Frage der Gebirgs-bildung, Abh. Math.-Phys. Kl. Sächs. Akad. Wiss. 37 (S) (1920)420.

[35] B. Carrapa, M.R. Strecker, E.R. Sobel, Sedimentary, tectonicsand thermochronologix evolution of the southernmost end of thePuna Plateau (NW Argentina): the intramontane Bolson deFiambala, International Geological Conference Electronic Ab-stract Volume, 2004, pp. 126–147, Florence.

[36] G.E. Bossi, C.M. Muruaga, J.C. Gavriloff, Sierras Pampeanas,in: G.G. Bonorino, R. Omarini, J. Viramonte (Eds.), XIVCongreso Geologico Argentino, 1999, Salta.

[37] R.A. Ketcham, R.A. Donelick, W.D. Carlson, Variability ofapatite fission-track annealing kinetics: III. Extrapolation togeological time scales, Am. Mineral. 84 (9) (1999) 1235–1255.

[38] R.A. Donelick, R.A. Ketchman, W.D. Carlson, Variability ofapatite fission track annealing kinetics: II. Crystallographicorientation effects, Am. Mineral. 84 (1999) 1224–1234.

[39] K. Gallagher, R. Brown, C. Johnson, Fission track analysis andits applications to geological problems, Annu. Rev. Earth Planet.Sci. 26 (1998) 519–572.

[40] E. Sobel, M.R. Strecker, Uplift, exhumation and precipitation:tectonic and climatic control of Late Cenozoic landscapeevolution in the northern Sierras Pampeanas, Argentina, BasinRes. 15 (4) (2003) 431–451.

[41] J. Barbarand, A.J. Hurford, A. Carter, Variation in apatite fission-track length measurement: implications for thermal historymodelling, Chem. Geol. 198 (2003) 77–106.

[42] I. Dunkl, Trackkey, windows program for calculation andgraphical presentation of EDM fission track data, version 4.2:http://www.sediment.uni-goettingen.de/staff/dunkl/software/trackkey.html, 2002.

[43] R.F. Galbraith, On statistical models for fission track counts,Math. Geol. 13 (1981) 471–478.

[44] P.F. Green, A new look at statistics in fission track dating, Nucl.Tracks Radiat. Meas. 5 (1981) 77–86.

[45] R.F. Galbraith, P.F. Green, Estimating the component ages in afinite mixture, Nucl. Tracks Radiat. Meas. 17 (1990) 197–206.

[46] M.T. Brandon, Decomposition of mixed age distributions usingBinomfit, On Track, Newsl. Int. Fission Track Community 24(2002) 13–18.

[47] J.I. Garver, M.T. Brandon, T.M.K. Roden, P.J.J. Kamp,Exhumation history of orogenic highlands determined by detritalfission-track thermochronology, in: U. Ring, M.T. Brandon, G.S.Lister, S.D. Willett (Eds.), Exhumation Processes: NormalFaulting, Ductile Flow and Erosion, vol. 154, GeologicalSociety, London, 1999, pp. 283–304.

[48] Y.M.R. Najman, M.S. Pringle, M.R.W. Johson, A.H.F. Robert-son, J.R. Wijbrans, Laser 40Ar/39Ar dating of single detritalmuscovite grains from early foreland-basin sedimentary depositsin India: implications for early Himalayan evolution, Geology 25(6) (1997) 535–538.

[49] B. Carrapa, J. Wijbrans, G. Bertotti, Episodic exhumation in theWestern Alps, Geology 31 (7) (2003) 601–604.

[50] P. Copel, T.M. Harrison, Episodic uplift in the Himalaya revealedby 40Ar/39Ar analysis of detrital K-feldspar and muscovite,Bengal fan, Geology 18 (1990) 354–357.

[51] Y.M.R. Najman, A. Carter, O. Grahame, E. Garzanti, Provenanceof Eocene foreland basin sediments, Nepal: constraints to thetiming and diachroneity of early Himalayan orogenesis, Geology33 (4) (2005) 309–312.

[52] M.T. Brandon, J.A. Vance, Tectonic evolution of the CenozoicOlympic subduction complex, Washington State, as deducedfrom fission track ages for detrital zircons, Am. J. Sci. 292 (1992)565–636.

[53] G.M.H. Ruiz, D. Seward, W. Winkler, Detrital thermochrono-logy—a new perspective on hinterland tectonics, an examplefrom the Andean Amazon Basin, Ecuador, Basin Res. 16(2004) 413–430.

[54] E. Sobel, T.A. Dumitru, Exhumation of the margins of thewestern Tarim basin during the Himalayan orogeny, J. Geophys.Res. 102 (1997) 5043–5064.

[55] C. Spiegel, W. Siebel, J. Kuhlemann, W. Frish, Toward acomprehensive provenance analysis: a multi-method approachand its implications for the evolution of the Central Alps, Geol.Soc. Amer. Bull., Spec. Pap. 378 (2004) 37–50.

[56] R.A. Ketcham, Some thoughts on inverse modeling and lengthand kinetic calibration, On Track, Newsl. Int. Fission TrackCommunity (2000 (June)) 9–14.

[57] P.F. Green, I.R. Dubby, G.M. Laslett, K.A. Hegarty, A.J.W.Gleadow, J.F. Lovering, Thermal annealing of fission tracks inapatite: 4. Quantitative modelling techniques and extension togeological timescales, Chem. Geol. 79 (1989) 155–182.

[58] A.J.W. Gleadow, I.R. Duddy, A natural long-term annealingexperiment for apatite, Nucl. Tracks Radiat. Meas. 5 (1981)169–174.

[59] N. Mancktelow, B. Grasemann, Time-dependent effects of heatadvection and topography on cooling histories during erosion,Tectonophysics 270 (1997) 167–195.

[60] P.G. Fitzgerald, T.F. Sorkhabi, T.F. Redfield, E. Stump, Upliftand denudation of the Alaska Range: a case study in the useof apatite fission track thermochronology to determineabsolute uplift parameters, J. Geophys. Res. 100 (1995)20175–20191.

[61] A. Deeken, E. Sobel, I. Coutand, M. Hascke, M. Riller, M.R.Strecker, Construction of the southern Eastern Cordillera, NWArgentina: from Early Cretaceous extension to middle Mioceneshortening, constrained by AFT-thermochronometry, Tectonics(submitted for publication).

[62] M. Springer, A. Förster, Heat-flow density across the CentralAndean subduction zone, Tectonophysics 291 (1998) 123–139.

[63] D.D. Blackwell, J.L. Steele, Thermal conductivity of sedimen-tary rocks: measurement and significance, in: N.D. Naeser, T.H.McCulloh (Eds.), Thermal History of Sedimentary Basins—Methods and Case Histories, Springer, 1988, pp. 13–36.

[64] A.J. Hoffmann, Climatic Atlas of South America, UNESCO,1975.

[65] T.E. Jordan, P. Zeitler, V.A. Ramos, A.J.W. Gleadow, Thermo-chronometric data on the development of the basement peneplain

100 B. Carrapa et al. / Earth and Planetary Science Letters 247 (2006) 82–100

in the Sierras Pampeanas, Argentina, J. South Am. Earth Sci. 2(3) (1989) 207–222.

[66] T. Jordan, F. Schlunegger, N. Cardozo, Unsteady and spatiallyvariable evolution of the Neogene Andean Bermejo forelandbasin Argentina, J. South Am. Earth Sci. 14 (2001) 775–798.

[67] T.J. Coughlin, Linked Orogen–Oblique Fault Zones in theCentral Andes: implications for Andean Orogenesis andMetallogenesis, Univerity of Queensland, 2000.

[68] G.E. Bossi, M.E. Vides, A.L. Ahumada, S.M. Georgieff, C.M.Muruaga, L.M. Ibanez, Analisis de las paleocorrentes y de lavarianza de los componentes a tres niveles, Neogeno del Valle delCajon, Catamarca, Argentina, Asoc. Argent. Sedimentol. 7 (1–2)(2000) 23–47.

[69] K. Kleinert, M.R. Strecker, Changes in moisture regime andecology in response to late Cenozoic orographic barriers: theSanta Maria Valley, Argentina, Geol. Soc. Amer. Bull. 113(2001) 728–742.

[70] H. Ege, E.R. Sobel, E. Scheuber, V. Jacobshagen, Exhumationhistory of the southern Altiplano plateau (southern Bolivia)

constrained by apatite fission-track thermochronology, Tectonics(submitted for publication).

[71] R.W. Allmendinger, Tectonic development, southeastern borderof the Puna Plateau, northwestern Argentine Andes, Geol. Soc.Amer. Bull. 97 (1986) 1070–1082.

[72] B.K. Horton, B.A. Hampton, G.L. Waadners, Paleogenesynorogenic sedimentation in the Altiplano Plateau and implica-tions for initial mountain building in the central Andes, Geol.Soc. Amer. Bull. 113 (2001) 1387–1400.

[73] L.d.V. Martinez, Mapa Geologica de la Provincia de Catamarca,1 :500000, Servicio Geologico Minero Argentino, Buenos Aires,1995.

[74] T.A. Dumitru, A new computer automated microscope stagesystem for fission track analysis, Nucl. Tracks Radiat. Meas. 21(1993) 575–580.

[75] A.J. Hurford, P.F. Green, The zeta age calibration of fission-trackdating, Chem. Geol. 41 (1983) 285–317.

[76] P.F. Green, A new look at statistics in fission-track dating, Nucl.Tracks Radiat. Meas. 5 (1981) 77–86.

ScienceDirect - Earth and Planetary Science Letters : Cenozoic orogenic g...gy in the Fiambalá Basin, southernmost Puna Plateau margin (NW Argentina)

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Earth and Planetary Science Letters Volume 247, Issues 1-2 , 15 July 2006, Pages 82-100

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doi:10.1016/j.epsl.2006.04.010 Copyright © 2006 Elsevier B.V. All rights reserved.

Cenozoic orogenic growth in the Central Andes: Evidence from sedimentary rock provenance and apatite fission track thermochronology in the Fiambalá Basin, southernmost Puna Plateau margin (NW Argentina)

B. Carrapa , a, , M.R. Streckera, and E.R. Sobela, aInstitut für Geowissenschaften, Universtität Potsdam, 14476 Golm, Germany Received 10 November 2005; revised 2 March 2006; accepted 6 April 2006. Editor: V. Courtillot. Available online 12 June 2006.

Abstract

Intramontane sedimentary basins along the margin of continental plateaus often preserve strata that contain fundamental information regarding the pattern of orogenic growth. The sedimentary record of the clastic Miocene–Pliocene sequence deposited in the Fiambalá Basin, at the southern margin of the Puna Plateau (NW Argentina), documents the late Miocene paleodrainage evolution from headwaters to the west, towards headwaters in the ranges that constitute the border of the Puna Plateau to the north. Apatite Fission track (AFT) thermochronology of sedimentary and basement rocks show that the southern Puna Plateau was the source for the youngest, middle Miocene, detrital population detected in late Miocene rocks; and that the margin of the Puna Plateau expressed a high relief, possibly similar to or higher than at present, by late Miocene time. Cooling ages obtained from basement rocks at the southern Puna margin suggest that exhumation started in the Oligocene and continued until the middle Miocene. We interpret the basin reorganization and the creation of a high relief plateau margin to be the direct response of the source–basin system to a wholesale surface uplift event that may have occurred during the late Cenozoic in the Puna–Altiplano region. At this time coeval paleodrainage reorganization is observed not only in the Fiambalá Basin, but also in different basins along the southern and eastern Puna margin, suggesting a genetic link between the last stage of plateau formation and basin response. However, this event did not cause sufficient exhumation of basin bounding ranges to be recorded by AFT thermochronology. Our new data thus document a decoupling between late Cenozoic surface uplift and exhumation in the southern Puna Plateau. High relief achieved at the Puna margin by late Miocene time is linked to Oligocene–Miocene exhumation; no significant erosion (< 3 km) has occurred since in this arid highland.

Keywords: plateau; sedimentary basin; provenance; thermochronology; exhumation; uplift; relief

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