“source to sink” sedimentology and petrology of a dryland ...€¦ · carbonate and clay...

“Source to Sink” Sedimentology and Petrology of a Dryland Fluvial System, and Implications for Reservoir Quality,

Lake Eyre Basin, Central Australia.

Saju Menacherry Bachelor of Science (Geology), University of Calicut, India. Master of Science (Geology), University of Kerala, India.

Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy

Australian School of Petroleum Faculty of Science

The University of Adelaide Australia

March 2008

“Source to Sink” Sedimentology and Petrology Chapter 6: Results (Modern Sediments)

Saju Menacherry - 123 -

CHAPTER 6 RESULTS (MODERN SEDIMENTS)

The results of chemical analysis, sieve analysis, various multivariate analysis, petrography, cathodoluminescence, x-ray powder diffraction analysis, and scanning electron microscopy analysis are all provided referenced to proximal, medial and distal areas of the Umbum Creek catchment.

6.1 CHEMICAL ANALYSIS The weight percentage of carbonates, clay, iron oxides and organic materials derived from chemical analysis data of the sand fraction is presented as a function graph (Table 6.1; Fig. 6.1). The graph represents the variability of composition of carbonates, clay and organic materials from each locality, and shows that there is a consistency with respect to sample composition of samples located in the proximal to the distal reaches of the Umbum Creek Drainage network.

6.1.1 PROXIMAL

The sediments from the proximal area (especially locations 13, 11, 12 and 10) of the Umbum Creek network deliver the highest amount of carbonates, clay and organic materials due to the lack of chemical weathering resulting from the short sediment storage time prior to sediment transportation to other downstream locations, which agrees the conclusion with Grantham and Velbel, (1988). Samples from location 10 yield the highest content of carbonate, clay, and organic materials because of the temporary accumulation of upstream carbonate sediments and clay materials in this area as the low gradient. The most carbonate grains are generated from the meta-sedimentary provenance of the proximal end with minor amounts of recycled carbonate grains have been derived from the sedimentary formations of Mesozoic deposits.

6.1.2 MEDIAL

The medial area of the Umbum Creek drainage network contains less carbonate, clay and organic materials in comparison to the proximal and distal sections, due to carbonate dissolution, little local input and the lack of clay coating on the grains. Chemical analysis suggests that variations in carbonate and clay content depends on controlling factors such as local source rock lithology influx, transporting medium and processes, residence time while in transportation, and degree of



Table 6.1: The weight percentage of carbonates, clay and organic materials in modem Umbum Creek sediments (sand fraction).

Chemical analysis of upstream and downstream samples

Location - Geographic Position

Sampling

Point

Sample Wt.(gms)

Before

analysis

Sample Wt.(gms)

after

analysis

Wt% of Carbonates, Iron

oxides, organic

materials & Clay

George Ck source 14(1) 50.00 48.82 2.36

George Ck source 14(2) 50.00 48.83 2.34

Hope Ck source 13(1) 50.00 48.70 2.60

Hope Ck source 13(2) 50.00 44.49 11.02

Davenport Ck Source 11(1) 50.05 47.21 2.84

Davenport Ck Source 11(2) 50.01 45.52 4.49

Intersection- Hope Ck & George Ck 12(1) 50.01 47.74 4.54

Intersection- Hope Ck & George Ck 12(2) 50.00 46.79 6.42

Sunny Ck Source 6(1) 50.02 49.50 1.04

Sunny Ck Source 6(2) 50.01 49.64 0.74

Davenport Ck 10(1) 50.00 46.56 6.88

Davenport Ck 10(2) 50.00 42.09 15.82

Davenport Ck meets George Ck 9(1) 50.01 48.90 2.22

Davenport Ck meets George Ck 9(2) 50.00 49.23 1.54

Sunny Ck Middle 5(1) 50.02 48.00 4.04

Sunny Ck Middle 5(2) 50.00 49.18 1.64

George Ck Intersection- Umbum Ck 8(1) 50.00 49.69 0.62

Umbum Ck Intersection- George Ck 8(2) 50.00 49.52 0.96

Palaeo - Neales 15(1) 50.01 47.05 2.96

Palaeo - Neales 15(2) 50.04 48.17 1.87

Umbum Ck 7(1) 50.00 47.72 4.56

Umbum Ck 7(2) 50.00 49.48 1.04

Sunny Ck →Mouth 4(1) 50.01 48.70 2.62

Sunny Ck →Mouth 4(2) 50.02 47.95 4.14

Intersection Umbum & Sunny Ck 3(1) 50.01 48.30 3.42

Intersection Umbum & Sunny Ck 3(2) 50.00 47.83 4.34

Gibber Plains 2(1) 50.01 49.04 1.94

Gibber Plains 2(2) 50.05 49.80 0.50

Umbum Creek Delta 1(1) 50.03 47.84 4.38

Umbum Creek Delta 1(2) 50.00 45.15 9.70



Figu

re 6.

1 Gra

ph re

pres

entin

g the

weig

ht pe

rcenta

ge of

carb

onate

s, cla

y and

orga

nic m

ateria

ls in

the U

mbum

Cre

ek m

oder

n sed

imen

ts.

Note

: sam

ples w

ith hi

gh va

lues (

wt %

> 8%

) are

deriv

ed fr

om H

ope C

reek

(13-

2), D

aven

port

Cree

k (10

-2) a

nd U

mbum

Cre

ek (T

ermi

nal s

play c

omple

x) (1

-2).



weathering (chemical and mechanical) processes (Suttner et al., 1981; Johnsson, 1993). The lower content of carbonates and clay coating on grains in these ‘medial’ samples is indicative of little influx from Eromanga Basin sedimentary deposits and a longer sediment storage time than proximal samples, which promotes chemical weathering.

6.1.3 DISTAL

The Umbum Creek distal section is dominated by fluvio-aeolian transportation and very low relief. The sand composition maturity increases downstream, indicating extended transportation, loner lived exposure to weathering conditions and less sediment supply from the nearby sedimentary outcrops. Location 1 reveals an increased content of carbonates, clay and organic materials due to sediment flux from the adjacent Palaeogene formations and detrital clay deposited with the sand grains in the terminal splay setting (Lang et al., 2004). The presence of carbonate or calcrete lithic fragments in these samples is associated with the Cenozoic carbonate clasts and the calcrete deposits outcropping in this area.

6.2 SIEVE ANALYSIS Grain-size distribution characteristics shown on frequency and cumulative plots provide considerable information about the sedimentary components and their distribution types (Pettijohn

et al., 1987). Reconstruction of grain-size trends in fluvial deposits can be used to understand the dominant controls on stratal architecture in foreland basins (DeCelles and Giles, 1996). In addition, grain-size trends can help interpret the sediment supply, tectonic subsidence and palaeoclimate of the region (Ashley, 1978). An intermediate region of rapid changes in grain size and sediment thickness exists where there is a mixed influence of subsidence and sediment supply (Dickinson et

al., 1983; Grantham and Velbel, 1988). The rate of sediment supply from catchment to depositional basin depends primarily upon climate, relief, catchment slope, river gradient and bedrock lithology (Blair and McPherson, 1994; Critelli et

al., 1997). Downstream changes in the percentages of grain types can be the result of stream erosion of bedrock; tributary, stream-bank and slope runoff contributions; selective abrasion or chemical loss; and selective sorting on the basis of shape and specific gravity (Critelli et al., 1997).



As the shape of the grain-size distribution curve vary greatly between samples of different origin, frequency plots of the grain-size distribution are particularly useful for identifying the distribution types of the grain-size components within sample (Sun et al., 2002) (Figs 6.2A, 6.2B & 6.2C and 6.3A, 6.3B & 6.3C) (Appendix 7 and 8). Grain size data were used to calculate grain size distribution trends along the river network from tributary channels and the main channel.

6.2.1 PROXIMAL

The grain-size analysis reveals that most samples from the proximal end of the Umbum Creek catchment were unimodal (Table 6.2), although there are also a few bimodal samples (14(1), 14(2), 13(1), 10(2), 9(2) and 5(2)) (Figs 6.2A, 6.2B & 6.2C and 6.3A, 6.3B & 6.3C). Hydraulic energy transports particles in three modes: by suspension, saltation or traction depending on the particle size (Heller and Paola, 1992; Robinson and Slingerland, 1998a). These grain-size groups are usually deposited together to form bimodal sediments when the transporting current slackens. Grain-size analysis of proximal creek samples reveals a predominance of upper medium sized sand. A downstream coarsening trend is evident, with moderately sorted coarse sand (1.73-0.52

φ) observed downstream (Table 6.2; Figs 6.4, 6.5 & 6.6).

The change of grain size downstream as in Figures 6.4, 6.5 and 6.6 is erratic because of the influence of sediment mixing from the local source and the entrance of another tributary to the main Umbum Creek. However, the overall grain-size trend line of each tributary suggests that grain size increases downstream. In addition, grains are sub-angular to sub-rounded in the most part of proximal end of the network. However these samples showing rounded grains along the channels, because of the reworking of grains from earlier deposited sandstone and siltstone. Changes in grain size and sorting are interpreted as the result of sediment influx from interfluves and adjacent dune field. In the proximal area of the drainage network, grain size varies through the addition of coarser sediments from the tributaries and the coarse-grained sediment supply from older sedimentary formations.

6.2.2 MEDIAL

Grain-size distribution graph shows that the downstream coarsening in grain size continues in the medial area of the Umbum Creek network. The source of each tributary at the proximal end of the network is characterised by medium grain size due to influence from the alluvial sediments derived from the foothills of the Davenport Ranges. Although some of the sample analysis shows decreasing grain-size (Figs 6.4, 6.5 & 6.6) downstream, however drainage patterns involve eroding



coarser sediments from the old formations (Eromanga Basin) in the tributaries, leading to coarser

grain-size in the medial area of the network (1.17-0.51 φ). Samples from the medial section are

unimodal throughout (Table 6.2). The moderate sorting and the sub-angular to rounded grain texture suggest more influx of sediments from reworking of the older (Eromanga Basin) sedimentary deposits.

6.2.3 DISTAL

Grain size analysis of all distal samples comprises lower to upper coarse sand except sample 3(2)

which shows a grain size of upper medium sand (1.19- 0.43 φ) (Figs 6.4, 6.5 & 6.6). Distal sample

grains are moderately sorted (Table 6.2). The distal end samples indicated either a bimodal—3(1), 3(2), 2(2), 1(1)—or a unimodal distribution—2(1), 1(2)—according to the influence of either aeolian or fluvial transportation. As the Umbum Creek network approaches the distal end, the collective effect of fluvio-aeolian interaction causes the sediments to become mostly bimodal. Most of the detrital material from the unimodal samples is supplied by surface run-off, and, therefore, the type of precipitation greatly influences the grain-size distribution of the sediments which agrees the observations with Robinson and Slingerland, (1998b). The distal end of the river system shows sub-angular to well-rounded grains, an outcome of aeolian processes. Grain-size variation in the distal area of the network depends on aggradation rates associated with lateral sediment influxes and aeolian reworking.



F

igure

6.2A

Gra

ph sh

owing

the f

requ

ency

curve

of th

e gra

in siz

e var

iation

from

lowe

r coa

rse to

uppe

r med

ium an

d bim

odal

distrib

ution

of si

eve a

nalys

is

in

the U

mbum

Cre

ek m

oder

n sed

imen

ts fro

m pr

oxim

al loc

ation

s.



Figu

re 6.

2B G

raph

show

ing th

e fre

quen

cy cu

rve of

the c

oarse

r gra

in siz

e and

unim

odal

distrib

ution

of si

eve a

nalys

is in

the U

mbum

Cre

ek m

oder

n

sed

imen

ts fro

m me

dial lo

catio

ns.



F

igure

6.2C

Gra

ph sh

owing

the f

requ

ency

curve

of th

e gra

in siz

e var

iation

from

lowe

r upp

er co

arse

and u

nimod

al dis

tributi

on of

siev

e ana

lysis

in

the

Umb

um C

reek

mod

ern s

edim

ents

from

distal

loca

tions

.



F

igure

6.3A

Gra

ph sh

owing

the c

umula

tive c

urve

of th

e gra

in siz

e var

iation

from

lowe

r coa

rse to

uppe

r med

ium an

d bim

odal

distrib

ution

of si

eve

ana

lysis

in the

Umb

um C

reek

mod

ern s

edim

ents

from

the pr

oxim

al loc

ation

s.



F

igure

6.3B

Gra

ph sh

owing

the c

umula

tive c

urve

of th

e coa

rser g

rain

size a

nd un

imod

al dis

tributi

on of

siev

e ana

lysis

in the

Umb

um C

reek

mod

ern

sed

imen

ts fro

m the

med

ial lo

catio

ns.



F

igure

6.3C

Gra

ph sh

owing

the c

umula

tive c

urve

of th

e gra

in siz

e var

iation

from

lowe

r upp

er co

arse

and u

nimod

al dis

tributi

on of

siev

e ana

lysis

in t

he U

mbum

Cre

ek m

oder

n sed

imen

ts fro

m the

dista

l loca

tions

.



Figure 6.4 Graphs representing mean grain size of sand fraction from the Sunny Creek and Davenport Creek, tributaries of Umbum Creek showing in apparent overall proximal to distal downstream coarsening trends.



Figure 6.5 Graphs representing mean grain size of sand fraction from the Hope Creek and George Creek, tributaries of Umbum Creek showing in apparent overall proximal to distal downstream coarsening trends.



Fig

ure 6

.6 Gr

aph r

epre

senti

ng th

e mea

n gra

in siz

e dist

ributi

on of

all u

pstre

am an

d dow

nstre

am sa

mple

point

s in t

he U

mbum

Cre

ek ne

twor

k sho

wing

the

appa

rent

down

strea

m co

arse

ning t

rend

.



6.2.4 MULTIVARIATE ANALYSIS – SIEVE GRAIN SIZE DATA

Multivariate analysis encompasses a number of different algorithms and methods for grouping objects of similar kinds. Cluster analysis was performed using Ward's hierarchical agglomerative method and the Euclidean distance measure (Ward, 1963). Q-mode cluster analysis is used to divide the results into different and distinct groups. Cluster analysis on grain size data was applied in order to evaluate the relationship between the quantitative variables. Multivariate analysis was used on the grain-size data of modern sand in order to classify them into sedimentary zones and to reveal the mixing effects in the dry land setting with respect to medium of transportation and climate. An easily readable dendrogram displays five clusters I -- V, which are separated using an

appropriate similarity distance of –1.6 (Fig. 6.7). The grain sizes in cluster I (1.19- 0.52φ) comprise

upper-medium to lower-coarse sand as sediments were transported through the proximal, medial and distal area of Sunny Creek into Umbum Creek. The sand in cluster II shows the coarsest

mean grain size (0.79- 0.43 φ) in the distal end of Umbum Creek. Cluster III sands are mostly

lower-coarse in grain size (1.09- 0.52 φ) having been sampled from the proximal and medial areas.

Table 6.2: Umbum Creek modern sands grain size analysis data - results. Cluster III also suggests a downstream coarsening trend (Fig. 6.7). In addition, samples in cluster IV are from the proximal area of Davenport Creek and show downstream coarsening (1.43- 0.52

φ) than other proximal end samples. The mean grain sizes of sands in cluster V are between 1.83

and 0.72 φ and represent proximal area samples. Cluster V samples are mainly derived from influx

of material from the sediment source area of Hope and George Creeks (Fig. 6.7).



Table 6.2: Umbum Creek modern sands grain size analysis data - results.



The samples in clusters I -- II were derived from Sunny and Umbum creeks in the proximal and medial area of the network (Fig. 6.7), indicating that the Mesozoic and Cenozoic sedimentary outcrops are actively supplying sediments to this part of the network. Clusters IV and V represent input from the proximal end of the Davenport, Hope and George creeks and show a finer grain size than that observed in other clusters. This suggests the influence of the sediment yield from the meta-sedimentary Davenport Ranges and sedimentary Mesozoic outcrops through the mixing effect of the confluences. Clusters I and II are dominantly coarse-grained sand, whereas clusters IV and V comprise medium to lower coarse-grained sands. Cluster III varies in grain-size due to the mixing effect from the Sunny and Umbum Creek confluences (Fig. 6.7). The presence of coarse-grained sand in cluster I and II samples results from the mixing effect of fluvio-aeolian transportation in the downstream distal end of the Umbum Creek network.

6.3 PETROGRAPHY Petrographical parameters and ternary plots such as QFR – (Quartz, Feldspar, and Rock fragment), QtFL – (Qt-total quartz, F-feldspar, L-lithic fragments), QmFLt - (Qm-quartz monocrystalline, F-feldspar, Lt- total lithics), QFkFp - (Q-quartz, Fk- K-feldspar, Fp-plagioclase feldspar), LmLvLs – (Lm-metamorphic lithic fragment, Lv-volcanic lithic fragment, Ls-sedimentary lithic fragment), LmLssLsc – (Lm-metamorphic lithic fragment, Lss-sedimentary siliciclastic fragment, Lsc- sedimentary carbonate fragment) and LssLsdLsl – (Lss- sedimentary siliciclastic fragment, Lsd-carbonate dolomite fragment, Lsl-carbonate limestone fragment) were used to discriminate the provenance of sand-sized grains using same methods of Dickinson, (1985) and Ingersoll et al., (1993). The major components of modern sands collected from Umbum Creek and its tributaries are monocrystalline and polycrystalline quartz, feldspar grains, and volcanic, metamorphic and sedimentary rock fragments (Appendix 3). Metamorphic rock fragments were classified according to two protolith compositions, and each was farther subdivided according to composition as illustrated by earlier workers such as Vezzoli et al., (2004) and Bernet and Bassett, (2005). Sedimentary and volcanic rock fragments were classified in a similar way.



Figure 6.7 Dendrogram given by “Q-mode” cluster analysis using a mean grain size distribution, showing clusters I- V. Note clusters I and III correspond to samples derived from Sunny Creek and Umbum Creek, and clusters IV and V from Davenport, Hope and George Creeks. Cluster II indicates the samples grain size distribution from distal end of the Umbum Creek, Cluster IV and V are denotes the grain size distribution from proximal area of the catchment.



Figur

e 6.8

Summ

ary f

igure

detai

ling t

he pe

rcenta

ge of

grain

comp

ositio

n of U

mbum

Cre

ek m

oder

n sed

imen

ts. N

ote th

e dow

nstre

am tr

end o

f incre

asing

mono

crysta

lline q

uartz

, and

also

the d

owns

tream

tren

d of in

creas

ing lit

hics i

n Sun

ny C

reek

.



Quartz and feldspar grains were classified according to inclusions and overgrowth into monocrystalline quartz, polycrystalline quartz of metamorphic or sedimentary origin, twinned and untwined character of plagioclase and K-feldspar and feldspar intergrowths. Other counted grains include micas, fossil/wood fragments and heavy minerals. Point-count results of each sample point are tabulated in Appendix 9. Grain percentages of each sample for the trilinear plots (ternary diagram) were computed and are grouped into the proximal, medial and distal area of the Umbum Creek catchment (Appendix 10). In addition, the grain type percentages plotted against the grain size of each category is tabulated in Appendix 11. The modal composition percentage of sands from the Umbum Creek and its tributaries are shown in Figure 6.8. The modal analysed data were plotted in various graphical illustrations using different ternary diagram which are in consistent with the earlier workers such as QFL ternary diagram (Folk, 1974), a QmFLt ternary diagram (Dickinson and Suczek, 1979; Dickinson et al., 1983), a QFkFp ternary diagram (Dickinson and Suczek, 1979), a QtFL ternary diagram (Dickinson, 1985) and a LmLvLs ternary diagram (Valloni, 1985; Ingersoll et al., 1993).

6.3.1 PROXIMAL

The modal sand composition and percentages of each proximal sample were plotted on ternary diagrams and are tabulated in Appendix 10. The proximal network samples consists of litharenites to sublitharenites as indicated by the QFL diagram, suggesting that while transportation of sediments from source areas (litharenite) to downstream sample points of proximal part, the composition of sediments were changed to sublitharenite (Fig. 6.9A). In addition, the QmFLt, diagram shows that sands from the proximal area of the Umbum Creek network comprise monocrystalline quartz ranging from 36.8% to 74% (Fig.6.9B). The origin of nine samples from the proximal area of the network suggests ‘quartzose recycled’; seven of which are ‘transitional recycled’ (Fig. 6.9B). The very low feldspar content (ranging from 8.8% to 1.2%) in the samples indicates the maturity of the sand composition (Fig. 6.9C). The QtFL ternary diagram (Fig. 6.9D) shows that the samples are most likely derived from a ‘recycled orogen’. The polycrystalline quartz in the proximal samples range from 17.2% to 6.4%, which are most like derived from the Mesozoic sediments. The volcanic and plutonic grains are much lesser than granitic origin (2.4%) (Fig. 6.10B). The metamorphic lithic grains range up to 43.6% (Fig. 6.11A & B) and are abundant at the source areas, but decrease during the course of the drainage network in the proximal area. Sedimentary



lithic fragments range from 20.8% to 1.6% in the proximal area, with sedimentary lithic contents higher than the sedimentary carbonate grains (Fig. 6.11C). The Sunny Creek sediment source area supplies large volumes of monocrystalline and polycrystalline quartz (Fig. 6.12). Mostly these region sediments are derived from Proterozoic sediments as well as from Jurassic and Cretaceous sedimentary units that are fluvial to shallow marine in nature. There appears to be an elevated percentage of monocrystalline quartz in the Sunny Creek source area, but this gradually decreases during transportation downstream due to more sedimentary lithic input to network. Polycrystalline quartz is less common but has the same concentrations with samples throughout the proximal area. The Davenport Creek source sediments stem from Neoproterozoic sequences of the Davenport Ranges and have a comparatively low proportion of monocrystalline quartz and moderate amounts of lithic fragments (Fig. 6.13). Hope Creek delivers the second highest source of mono- and polycrystalline quartz as it is influenced by the sediment supply from local alluvial fans (Tertiary and Quaternary sediments), as well as directly from Davenport Ranges (Fig. 6.14). Sunny Creek sediment source samples have fewer sedimentary lithic grains and more feldspar grains than any other sediment source samples. The George Creek sediment source area has the highest percentage of lithic fragments (metamorphic), which supply the entire fluvial network and the least amount of quartz grains (Fig. 6.15). Hope Creek source samples contain sedimentary and carbonate lithic fragments, which originate from the oldest deposits of the Neoproterozoic: evaporitic clastics and carbonates, sandstone and siltstone. Umbum Creek is formed from the merging of George Creek and Davenport Creek, and Umbum Creek sediments comprise sediments from Davenport Creek, Hope Creek and George Creek (Fig. 6.16). Hope Creek and George Creek supply more lithic fragments and less quartz to Umbum Creek than Davenport Creek does. Although the mixing of the sediments from George Creek and Davenport Creek reduces the amount of quartz in the Umbum stream sediments, at the start of the medial area an increase in quartz grains is noted, most likely due to the quartz grain supply from the Mesozoic outcrops and the disintegration of lithic fragments.



Figure 6.9 QFL ternary diagrams of the proximal area samples showing the percentage of grain composition in the Umbum Creek modern sediments. A. Showing the proximal upstream samples of litharenite changing trend to sublitharenite along the downstream course within the proximal area. B. Detailing the provenance of transitional and quartzose recycled sediments in the proximal area. C. Featuring the compositional maturity of the sediments with very low feldspar content. D. Showing the sediment generation of recycled provenance in the proximal samples. Details are in the Appendix 10.



Figu

re 6.

10 A

. QFL

tern

ary d

iagra

ms sh

owing

the c

hang

e in p

rove

nanc

e of g

rains

from

‘sou

rce to

sink

’ sed

imen

t sam

ples w

ith re

spec

t to sa

mple

locati

ons.

B. L

ithic

grain

comp

ositio

n in U

mbum

Cre

ek m

oder

n sed

imen

ts, sh

owing

meta

morp

hic an

d sed

imen

tary l

ithics

as do

mina

nt in

both

in so

urce

and s

ink ar

eas.



Figure 6.11 Ternary diagrams of lithics distribution in the Umbum Creek modern sediments. A. LmLvLs ternary diagram showing the variation in lithic frame work grains in entire catchment B. LmLssLsc ternary diagram illustrates the lithic grain composition C. Lithic grain composition of LssLsdLsl ternary diagram. These suggest that metamorphic and sedimentary lithics are the dominant lithic grains in the entire Umbum Creek catchment. Details are in the Appendix 10.



Figure 6.12 Various ternary diagrams of Sunny Creek samples showing the percentage of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the majority of Sunny Creek samples of sublitharenite composition trend excluding subarkose (6-2) in the upstream sample. B. QmFLt ternary diagram showing the provenance as “quartzose recycled” sediments in Sunny Creek. C. Ternary diagram featuring the compositional maturity of the sediments with low feldspar content. D. Ternary diagram showing the sediment generation of recycled provenance sediments with high quartz content in the Sunny Creek samples. Details are in the Appendix 10.



Figure 6.13 Various ternary diagrams of Davenport Creek samples showing the percentage of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the Davenport Creek upstream samples of litharenite changing trend to sublitharenite along the downstream course. B. QmFLt ternary diagram showing the provenance of quartzose recycled sediments except 11-2 as transitional recycled. C. Ternary diagram featuring the maturity of the sediments with low feldspar content. D. Ternary diagram showing the sediment generation from recycled provenance in the Davenport Creek samples. Details are in the Appendix 10.



Figure 6.14 Various ternary diagrams of Hope Creek samples showing the percentage of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the upstream samples of litharenite changing trend to sublitharenite along the downstream course. B. QmFLt ternary diagram showing the provenance of transitional and quartzose recycled sediments in the proximal area. C. Ternary diagram featuring the maturity of the sediments with low feldspar content. D. Ternary diagram showing the sediment generation from recycled provenance in the samples with moderate quartz grains. Details are in the Appendix 10.



Figure 6.15 Various ternary diagrams of George Creek samples showing the percentage of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the upstream samples of litharenite B. QmFLt ternary diagram showing the provenance of transitional recycled sediments in the samples. C. Ternary diagram showing the maturity of the sediments with low feldspar content. D. Ternary diagram featuring the sediment generation from ‘recycled’ provenance in the samples with low quartz content. Details are in the Appendix 10.



Figure 6.16 Various ternary diagrams of Umbum Creek samples showing the percentage of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the Umbum Creek samples of sublitharenite along the downstream course except sample 9-2, which is litharenite. B. QmFLt ternary diagram showing the provenance of mostly quartzose recycled, however a few derived from transitional recycled sediments. C. Ternary diagram showing the maturity of the sediments with low feldspar content. D. Ternary diagram featuring the sediment generation from ‘recycled’ provenance in the samples with moderate to high quartz content. Details are in the Appendix 10.



6.3.2 MEDIAL

The tabulated modal sand composition and percentages of ternary diagrams of each sample from the medial area are detailed in Appendix 10. The medial network samples contain sublitharenites, as illustrated in the QFL diagram (Fig. 6.17A). The QmFLt diagram shows that sand samples from the medial areas of the Umbum Creek network derive from a quartzose recycled provenance (Fig. 6.17B). The QmFLt ternary diagram shows that the composition of monocrystalline quartz ranges from 70.8% to 56.8% (Fig. 6.17B). Where as the feldspar content (1.6% -- 6.8%) indicates more mineralogical maturity of sand composition than in the proximal area (Fig. 6.17C). The samples plotted in the QtFL ternary diagram (Fig. 6.17D) were interpreted as deriving from a recycled orogen provenance. The polycrystalline contents in the medial samples range from 18.8% to 6.8%, which suggests less mechanical weathering in this area. Volcanic grains are absent whilst plutonic grains are rare, ranging from 1.2% to 0.0% (Fig. 6.10B). The metamorphic lithic grains are less common in comparison to the proximal area, as they decrease during the downstream course of the network in the medial area, and comprise 11.6% to 4.8% (Fig. 6.11A & B). The sedimentary lithic fragments range from 16.4% to 7.6% where these fragments are more common than the sedimentary carbonate grains (Fig. 6.11C). Umbum Creek and Sunny Creek sediments share the medial area of the Umbum Creek drainage network, where an increasing linear trend in monocrystalline quartz content is evident (Fig. 6.8). Polycrystalline quartz is more dominant in the Sunny Creek samples whereas the metamorphic lithics are rare (Fig. 6.12). The Umbum Creek samples show more sedimentary lithics than those from Sunny Creek (Fig. 6.16). The mixing of sediments from George, Hope and Davenport Creeks increases the carbonate content in the Umbum Creek sediments. However, there is an overall decrease in carbonate grains along the downstream network. Variations in composition in this section are influenced by sediment influx from drainage patterns, the mixing effect from the supplying interfluves, and weathering of the sediments.



Figure 6.17 Various ternary diagrams of samples from the medial area showing the percentage of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the medial region samples are completely of sublitharenite. B. QmFLt ternary diagram showing the provenance entirely of quartzose recycled sediments in the medial area samples. C. Ternary diagram showing the mineral maturity of the sediments with high quartz and low feldspar content. D. Showing the sediment source from a ‘recycled’ provenance in the medial samples with a high quartz content. Details are in the Appendix 10.



6.3.3 DISTAL

Data from six samples from the distal end of the Umbum Creek drainage network including the modal sand composition and percentages of each sample calculated from the ternary diagram are tabulated in Appendix 10. The distal network samples plot in the sublitharenites portion of the QFL diagram (Fig. 6.18A). The QmFLt diagram suggests a ‘quartzose recycled’ provenance for the four samples in the distal area of the network, another two samples plot in the ‘transitional recycled’ part of this diagram (Fig. 6.18B). Monocrystalline quartz ranges from 62.4% to 43.6% (Fig. 6.18B). With very low feldspar content (4% - 2%) noted in the samples indicating the high compositional maturity of these samples. An exception is sample 3(2) which has 12.4% feldspar (Fig. 6.18C), most likely this particular sample area acquires more feldspar from the locally derived Mesozoic (Bulldog Shale and Etadunna Formations) and Cenozoic sediments. Mesozoic (Bulldog Shale and Etadunna Formations) and Cenozoic deposits originally obtained feldspar rich sediments from Gawler Craton and uplifted Peake and Denison Inliers. The QtFL diagram (Fig. 6.18D) shows the provenance for the samples as ‘recycled orogen’. This suggests sediment source are generally derived from the local outcrop areas. Polycrystalline quartz in the distal samples ranges from 16.0% to 6.8%. Volcanic grains are absent and plutonic grains are very rare, ranging from 1.6% to 0.0% (Fig. 6.10B). The metamorphic lithic grains are less common than other parts of the Umbum Creek network and decrease during the course of the network, comprising 9.6% to 4.4% (Fig. 6.11A & B). Sedimentary lithic contents are more common than sedimentary carbonate grains and range from 26.0% to 17.6% in the distal end (Fig. 6.11C). The distal area of the Umbum Creek network comprises mainly sediments from Umbum and Sunny creeks. The amalgamation of these sediments decreases the monocrystalline and polycrystalline quartz population, but the quartz content increases gradually again farther downstream (Fig. 6.16). The other important variation observed in grain composition is the increase in sedimentary and metamorphic lithics in the distal sediment samples, when compared to proximal and medial areas.



Figure 6.18 Various ternary diagrams of samples from the ‘distal’ area showing relative the percentages of grain composition in the Umbum Creek modern sediments. A. QFL ternary diagram showing the entire distal area samples of sublitharenite along the downstream course. B. QmFLt ternary diagram showing the provenance of transitional and quartzose recycled sediments in the distal area. C. Ternary diagram showing the maturity of the sediments with low feldspar content. D. Ternary diagram featuring the sediment generation from the recycled provenance in the distal area samples with moderate to high quartz content. Details are in the Appendix 10.



6.3.4 MULTIVARIATE ANALYSIS – THIN SECTION GRAIN SIZE DATA

Mean grain sizes, measured in microns during the thin section modal analysis (point count) of each grain, are tabulated and plotted in Figure 6.19. Q-mode cluster analysis was performed using a paired group hierarchical agglomerative method and the Euclidean distance measure as described by Ward, (1963). Cluster analysis suggests that the data is ‘spread’ into four clusters (I to IV), which are separated using an appropriate similarity distance of –1.95 (Fig. 6.20). The grain sizes in

cluster I (1.25- 0.57φ) comprise upper-medium to lower-coarse as these sands have been

generated from the Hope Creek sediment source area, where the grain size of these meta-sediments are upper-medium to lower-coarse. This suggests the sediment yield was from the meta-sedimentary outcrops of the Davenport Ranges (Fig. 6.5 & 6.8). Samples in ‘cluster II’ shows mean grain sizes ranging from upper-medium to lower-coarse (1.5 -

0.52 φ) and is restricted to the proximal end of the Umbum Creek network. Clusters I-II comprises

samples from the proximal area of Davenport, Hope and George Creeks. Similarly Cluster III sands come from the proximal and medial areas of the network and are mostly lower-coarse in

grain size (1.09- 0.42 φ). Cluster III samples also show a downstream coarsening trend which is

most likely limited to the mixing effects of coarser grained Sunny Creek sediments. This latter observation suggests that sediment influx from the Mesozoic sedimentary deposits with the Umbum Creek catchment is likely sediment provenance source. Samples in cluster IV are located in the distal area and are characterised by downstream

coarsening. Grain sizes range from upper-medium to upper-coarse (1.21- 0.42 φ). Cluster IV

sands show a wide range of grain size, probably due to the fluvio-aeolian interaction. These sands are confined to the distal end of the network and are generated mainly from the Cenozoic outcrops of the network. In summary grain size of clusters I and II comprise medium to lower coarse-grained sand, whereas the grain size of clusters III and IV comprise coarse-grained sand. Sand generated from the Davenport Ranges, and in area from Mesozoic deposits in the proximal end most likely constitute sediments within clusters I and II. Clusters III and IV include all samples from Sunny and Umbum creeks. Grain sizes in these clusters III and IV are controlled by the inclusion of Mesozoic and Cenozoic sediments. This observation suggests that grain-size variations are caused by sand influx generated from the meta-sedimentary and sedimentary deposits outcropping between the Davenport Ranges and Lake Eyre sediment ‘sink’.



F

igure

6.19

Fre

quen

cy di

stribu

tion g

raph

repr

esen

ting t

he m

ean g

rain

size d

istrib

ution

(mod

al an

alysis

) of th

in se

ction

samp

les po

ints f

rom

along

the

en

tire U

mbum

Cre

ek dr

ainag

e netw

ork.

Note

the co

nsist

ent g

rain-

size r

ange

betw

een 0

.5 –1

.5 Φ



Figure 6.20 Dendrogram given by paired group cluster analysis using mean modal analysis grain size distributions. Showing the clusters I-II from Davenport, Hope and George Creeks, and clusters III – IV from Sunny Creek and Umbum Creek respectively. Note that cluster IV represent the distal area of the drainage network, whilst cluster III represents the medial area and cluster I – II share the proximal area of the Umbum Creek network.



6.3.5 MULTIVARIATE ANALYSIS – SAND COMPOSITION

The numerical classification of the framework compositions (quartz-feldspar-rock fragments) of thirteen samples was accomplished using hierarchical Q-mode cluster analysis (Appendix 10). The resulting dendrogram groups them into three clusters (A, B and C) using a similarity distance of –30 (Fig. 6.21). The sand compositions in cluster A are characterised by high quartz (59.6% -- 43.2%), low feldspar (3.6% -- 1.2%) and the presence of many rock fragments (54.0% -- 36.8%). This suggests sediment yield from the meta-sedimentary outcrops of the Davenport Ranges and that Cluster A primarily represents the proximal end of the Umbum Creek network. However, distal sample 1(1) is also included in cluster A due to high rock fragments, resulting from lithic fragments generated from Cenozoic sediment which is consistent with the earlier observations with Callen et al., (1986) and Alley, (1998). The sand composition in cluster B is high in quartz (71.6% -- 63.6%), higher in feldspar (12.4% -- 2.0%) with fewer rock fragments (29.6% -- 24.0%). Cluster B is constrained to the medial and distal area of the drainage network. This indicates that the sediment generation is locally influenced and is more likely to be Mesozoic sedimentary in origin. This is because sediments reworked from the Mesozoic sedimentary deposits have had little time to disintegrate through the weathering processes. The cluster C sand composition is very high in quartz (84.0% -- 72.0%), sparse in feldspar (8.8% -- 1.2%), and has comparatively less rock fragments (22.8% -- 7.2%) compared to other clusters. Cluster C suggests the increasing trend in quartz content is mainly due to the mixing effect of Mesozoic and Cenozoic sediments. In addition, Cluster A is dependent on the metamorphic rock fragments from the Davenport Ranges and Cenozoic deposits. Clusters B and C shows a linear trend which suggests the increase in quartz content from the medial to the distal part of the network, whilst feldspar and lithic proportions decrease.



Figure 6.21 Hierarchical “Q-mode” cluster analysis grouping 30 sand sized samples into clusters A-C, based on framework grain (Quartz – Feldspar – Lithic fragments) composition. Cluster A samples dominates with lithic grain fragments, cluster B samples indicates quartz and feldspar grains dominance, whilst cluster C samples showing abundance in quartz grains only.



6.4 CATHODOLUMINESCENCE (CL) Cathodoluminescence analysis on selected samples was performed to farther verify frame work grain lithology and provenance. The main intention of the cathodoluminescence analysis was to verify and cross check the provenance of frame work grains, which are already identified through petrographic works. Petrographic data can be integrated with cathodoluminescence analysis (Bernet and Bassett, 2005) to confirm sources of quartz, carbonate and feldspar grains. Quartz grains, identified as plutonic in origin by petrographic techniques were interpreted to be of the same origin by cathodoluminescence analysis. Similar identification was made on volcanic, metamorphic, feldspar, silcrete and calcrete grains using cathodoluminescence images (Fig. 6.22), which are agreed with the conclusions of previous workers like Seyedolali et al., (1997), Kwon and Boggs Jr, (2002), Richter et al., (2003) and Bernet and Bassett, (2005). Figure 6.22 shows the comparison of provenance and grain interpretations based on cathodoluminescence with those based on petrographic data. The application of integrated cathodoluminescence and petrographic provenance analysis of frame work grains are demonstrated here for four locations—1(2), 15(2), 5(2) and 9(2)—from the modern Umbum Creek sands. Results show that sediment source rock interpretation based solely on standard petrographic techniques of quartz may yield exactly the same interpretation as that based on cathodoluminescence analysis of quartz. This agrees with previous workers especially with Seyedolali et al., (1997) and Bernet and Bassett, (2005). The modal quartz sand compositions were tabulated from combined cathodoluminescence and petrographic analysis of the four samples and from the petrographic analysis of thirty samples. The tabulated data are detailed in Appendix 9. The quartz provenance discrimination ternary diagrams were plotted using percentages of the three main quartz grain types observed (volcanic, plutonic and metamorphic quartz) (Fig. 6.23). These plots reveal ~ 57% plutonic quartz, ~ 38% metamorphic quartz and ~ 5% volcanic quartz grains. These results demonstrate that plutonic quartz is the most abundant component in the majority of sediment samples, which are preferentially abundant in Sunny Creek, and less abundant from George Creek, reflecting the influence of plutonic basement, and to a lesser degree a metamorphic or mixed basement (Fig. 6.23).



Farther analysis of quartz types shows that plutonic rocks were more significant than metamorphic rocks as sources for quartz frame work in most of the ‘medial’ and ‘distal’ samples, whereas metamorphic rocks were a more dominant source for ‘proximal’ samples. The high incidence of plutonic quartz grains in the ‘medial’ and ‘distal’ samples probably represent recycled quartz grains from the sedimentary deposits of Mesozoic and Cenozoic in the Umbum Creek catchment, those sediment provenance are plutonic/basement rocks. Fewer volcanic quartz grains were observed in the modern samples than expected with respect to sediment provenance through the petrographic analysis of the sediment source rocks. The ternary diagram suggests an abundance of metamorphic quartz in the ‘proximal’ source areas of Davenport, Hope and George creeks. Along the drainage network, more plutonic quartz grains than metamorphic grains are supplied to the modern sediment population. Where ‘medial’ samples have a higher abundance of plutonic quartz grains than those of metamorphic origin (Fig. 6.23). In contrast ‘distal’ samples vary in their composition of plutonic to metamorphic quartz grains. For example, sample 3(1), has a high abundance of plutonic quartz grains, as result of the combined mixing effect of the proximal and medial sediments. However, samples from the downstream ‘distal’ drainage network have more metamorphic quartz grains. For example in sample 1(1), the maximum amount of metamorphic quartz grains in this region is most likely limited to recycled metamorphic grains derived from early Cenozoic sedimentary rocks; especially those outcropping near the distal region of the network. On the other hand, the sample 1(2) in the ‘distal’ part of the drainage network retains the dominance of plutonic quartz grains. This may be due to the mixing effect of older (recycled) Mesozoic sedimentary deposits near the Umbum Creek terminal splay.



Figure 6.22 Cathodoluminescence photomicrographs of various quartz lithotypes and lithic fragments. A. Quartz grains under plane polarized light, P- monocrystalline quartz of igneous origin, V- monocrystalline quartz of volcanic origin, M- monocrystalline quartz of metamorphic origin. B. Cathodoluminescence photomicrograph of quartz grains. Illustrating different quartz grain provenances as the same as identified in (A). C. Photomicrograph showing carbonate grain (C) under polarized light D. Photomicrograph of carbonate grain under cathodoluminescence E. Photomicrograph showing silcrete (S) and feldspar (F) under polarized light F. Photomicrograph of silcrete (S) and feldspar (F) under cathodoluminescence.



Figure 6.23 Ternary diagram showing the relative percentage of quartz grain compositions in the Umbum Creek modern sediments. Note the importance of plutonic quartz (‘medial’ samples) with respect to metamorphic quartz in ‘proximal’ samples.



6.5 X-RAY POWDER DIFFRACTION (XRD) XRD analysis was performed on three selected samples: 6 (1) from the proximal, 15 (1) from the medial and 1 (2) from the distal area of Umbum Creek (Figs 6.24A, 6.24B and 6.24C). The relevance of the XRD analysis on selected samples to achieve the information in various mineralogy and composition of clay sized particles in samples, the result suggest different sediment modifying processes (mechanical and chemical disintegration, winnowing and diagenesis) and clay sized fraction in dry land environments mainly in proximal, medial and distal parts of the Umbum Creek catchment. The XRD results are mainly used to compare variation in the mineralogy and composition of the samples in three parts of the Umbum Creek drainage network with respect to the clay fraction sediment provenance. The total mineral assemblages of the proximal (6 –1) sample include quartz, microcline, albite and haematite. The absence of a clay mineral assemblage indicates that the sediment in the source area of Sunny Creek is derived mostly from meta-sedimentary and sedimentary rocks with little clay content. The clay fraction mineralogy of sample (15-1) from the medial area of the network is enriched in quartz, microcline, kaolinite, hematite, ilmenite, albite and illite. The mudstone clasts eroded from the Bulldog Shale are a prominent supplier of clay minerals to the medial area of the system. The mineralogical character of the distal end sample (1-2) is slightly different from that of the proximal and medial samples. The distal sample exhibits a mineralogy that includes quartz, halite, gypsum, kaolinite, sanidine, hematite and albite. Kaolinite is a prominent component of modern fluvial sediment and is most probably derived from the Bulldog Shale. The results of clay fraction (<2 micron fraction) XRD analysis show that quartz constitutes the major content of any sample. Feldspar, clay minerals, hematite, gypsum and halite constitute minor amounts within the clay fraction of these samples. The results indicate that kaolinite is the main kaolin type present in the medial and distal areas of the Umbum Creek network. Minor trace amounts of albite (Na-plagioclase) were also present in samples, and are interpreted as having formed from the albitisation of detrital potassium feldspars (orthoclase and microcline). The occurrence of halite indicates an evaporative (lacustrine) depositional environment with both dry and wet conditions. The presence of hematite within the fine fraction sediments suggests prolonged weathering of iron-bearing rocks in arid climatic conditions. The presence of sanidine was noted in clay fraction and suggests that the evolution of sanidine most likely by the weathering of volcanic grains supplied from Cenozoic meta-sedimentary deposits of the Davenport Ranges.



Figu

re 6.

24A

XRD

analy

sis of

Sun

ny C

reek

samp

le (lo

catio

n 6-1

) fro

m the

prox

imal

area

of th

e Umb

um C

reek

drain

age n

etwor

k (cla

y fra

ction

).

Note

quar

tz (d

omina

nt), m

icroc

line,

albite

and h

emati

te (su

bord

inate)

are t

he m

ain m

inera

ls ob

serve

d.



Figu

re 6.

24B

XRD

analy

sis of

palae

o Nea

les du

ne sa

mple

(loca

tion 1

5-1)

in th

e med

ial ar

ea of

the U

mbum

Cre

ek dr

ainag

e netw

ork (

clay f

racti

on).

Note

quar

tz (d

omina

nt), m

icroc

line,

kaoli

nite,

ilmen

ite, il

lite, a

lbite

and h

emati

te (su

bord

inate)

are t

he m

ain m

inera

ls ob

serve

d.



Figu

re 6.

24C

XRD

analy

sis of

Umb

um T

ermi

nal s

play s

ample

(loca

tion 1

-2) o

f the d

istal

area

of th

e Umb

um C

reek

drain

age n

etwor

k (cla

y fra

ction

). N

ote

quar

tz (d

omin

ant),

hal

ite, g

ypsu

m, k

aolin

ite, s

anid

ine,

alb

ite a

nd h

emat

ite (s

ubor

dina

te) a

re m

ain

min

eral

s ob

serv

ed.



6.6 SCANNING ELECTRON MICROSCOPY (SEM)

The SEM analysis offers the possibility of determining the exact nature of very fine intergrowths of authigenic minerals and allows for the accurate chemical analysis of very small particles. SEM has great potential for identifying surface texture, grain coating, and overgrowths, which can assist in the interpretation of depositional and diagenetic environments. Various grain coatings and silica nodules were observed using SEM analysis in this study. The main grain coatings observed were; hematite and anatase coating and clay coating. The grains from the Palaeo-Neales area (sample location 15-1 and 7-2) showed quartz precipitation overgrowths as nodules having nucleated on to grain surfaces, similarly alumino-silicate (clay) coating (Fig. 6.25). The grains coated with alumino-silicate clays were more common in the ‘distal’ end sands than in the ‘proximal’ and ‘medial’ samples (sample location 1-2). Hematite and anatase coatings were observed commonly in silcretes and aeolian reworked grains. Overgrowths on quartz grains and the iron oxide coating on aeolian sand grains were clearly visualised and documented using the SEM. Cementing materials like quartz, calcite and evaporites (salts) are interpreted to represent the ‘first’ as early diagenetic phases. In addition, SEM analysis also revealed the types of clay fractions attached to grains surfaces (sample location 1-2 and 3-1) (Fig. 6.26). In selected samples (15-1, 1-2 and 3-1) grain coats, overgrowths and cementing materials suggested deposition of grains in a dryland setting within an ephemeral river to playa lake environment. This interpretation is consistent with the observation of earlier works like McBride, (1985), Bullard and White, (2002), and Bullard and McTainsh, (2003). SEM analysis on the modern Umbum Creek sediments establishes dryland setting in western Lake Eyre Basin.



Figure 6.25 SEM analysis results showing alumino-silicate filling the cracks (A+1), clay and hematite coating (D+2), overgrowth of quartz (A+2, D+1), growth of quartz nodules (B+1) and feldspar - kaolinite (B+2, C+1) in modern Umbum Creek sediments.



Figure 6.26 SEM analysis results showing clay coating, hematite coating (B+2), quartz cement (B+1), alumino-silicate coating (A+1), quartz cements (C+1) and feldspar - kaolinite overgrowths (D+1) in modern Umbum Creek sediments.



6.7 STEREO- ZOOM BINOCULAR MICROSCOPY Many clasts in the modern sand samples from Umbum Creek exhibit microfeatures that developed through aeolian processes, such as concoidal fractures, elongate depressions, V-shaped percussion features and abrasion fatigue which agrees with the descriptions with Mahaney, (2002). The significance of the stereo-zoom binocular microscopy analysis on selected samples to obtain the information on aeolian processed grains and its textural features in a dry land setting that facilitate the fluvio-aeolian interaction in modern Umbum Creek catchment. Geographically sample locations were selected for the stereo-zoom binocular microscopy study with a intension to represent the region by maximum fluvio-aeolian interaction. The results from the stereo- zoom microscopic analysis (selected samples locations 15-2, 12-2, 1-2 and 3-1) reveals the physical influences of fluvial and aeolian processes on sediment frame work grains. The surface textures of aeolian grains and fluvial reworked grains were clearly identified (Fig. 6.27). The percussion marks and roundness of the aeolian grains were noted and documented. The roundness of the grains indicates the high deflation (wind erosion) in the terminal splay area. In addition the reddish colour of the hematite and anatase coating was clearly observed during stereo-zoom microscopic analysis (Fig. 6.27 A & B). The features (concoidal fractures, elongate depressions, V-shaped percussion) on numerous grain surfaces indicate that fluvio-aeolian interactions were developed under prolonged arid climatic conditions and suggest that the reworking of fluvial grains within the aeolian environment and vice versa. ‘Distal’ end grains exhibit a stronger fluvio-aeolian interaction than the ‘medial’ and ‘proximal’ sediment grains, as distal end grains have been subjected to more prolonged aeolian processes.



Figure 6.27 Stereo- zoom microscopic analysis analysis results. A. & B. illustrating hematite coating and ‘aeolian’ texture (B+1 and B+2). C. Photograph of rounded aeolian grain with grain impact percussion marks (C+1). D. Photograph polycrystalline quartz grain of both fluvial (D+1) and aeolian (D+2) origin.

“source to sink” sedimentology and petrology of a dryland ...€¦ · carbonate and clay...

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