Geomorphological evidence of neotectonic deformation in the … · 2017-02-14 · Fluvial...

Geomorphology 228 (2015) 579–596

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Geomorphology

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Geomorphological evidence of neotectonic deformation in the CarnarvonBasin, Western Australia

Beau B. Whitney ⁎, James V. HengeshThe Centre for Offshore Foundation Systems, The University of Western Australia, M053, 35 Stirling Highway, Crawley, Perth, Western Australia 6009, Australia

⁎ Corresponding author. Tel.: +61 4 1221 4726.E-mail addresses: [email protected], beau.whitne

(B.B. Whitney), [email protected] (J.V. Hengesh

http://dx.doi.org/10.1016/j.geomorph.2014.10.0200169-555X/© 2014 The Authors. Published by Elsevier B.V

a b s t r a c t
a r t i c l e i n f o
Article history:Received 16 May 2014Received in revised form 1 October 2014Accepted 13 October 2014Available online 23 October 2014

Keywords:Fluvial geomorphologyAvulsionSCRNeotectonicWestern Australia

This study examines channel-scale morphodynamics of ephemeral streams in the onshore Carnarvon basin in aridwest-central Western Australia. The rivers in this region have low gradients, the landscape has low relief, and therates of climatically and tectonically driven geomorphic processes also are low. As a result, the rivers in theCarnarvon alluvial plain are highly sensitive to minor perturbations in base level, channel slope, and fluvial energy.We use channel planform adjustments, streamgradient changes, and floodplain profiles acrossmultiple ephemeralstreams within a variety of catchments and flow regimes to determine if tectonically driven land level changes areaffecting channel form and fluvial processes. Growth of individual fold segments is shown to have altered streamand floodplain gradients and triggered repeated avulsions at structurally controlled nodes. Aligned perturbationsin channel formacrossmultiple channel-fold intersections provide systematic geomorphic evidence for the locationand orientation of neotectonic structures in the region. These features occur as a belt of low relief anticlines in theCarnarvon alluvial plain.

© 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/3.0/).

1. Introduction

This study assesses the fluvial geomorphology of the Gascoyne andLyndon rivers and adjacent streams within the Carnarvon basin inwest-central Western Australia (Fig. 1). The region herein referred toas the Carnarvon alluvial plain is arid with ephemeral low gradientalluvial rivers and includes the Minilya plain of Hocking et al. (1985a,b) in the north and the Gascoyne alluvial plain or old delta system ofPassmore (1968) in the south. We use channel planform characteristicsand avulsion histories to assesswhether previously unidentified tectonicdeformation is evident in the fluvial geomorphological record. Channelcharacteristics are mapped and evaluated using digital elevation dataon a number of channels that range in size from the 865-km-longGascoyne River, Western Australia's longest river, to unnamed streamsjust a few kilometers long. Channel response to gradient changes ob-served across this range of scales varies systematically in relation tostream characteristics (e.g., discharge, flow frequency) and variationsin fold amplitudes.

River channels and bedforms are highly sensitive to changes in fluvialgradients (Holbrook and Schumm, 1999) and arguably the lower a river'sgradient the more sensitive it is to these changes. Ephemeral drylandrivers may not adjust their gradients in response to allogenic controls asrapidly as perennial streams (Schummet al., 2000), and as a consequence,

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evidence of channel gradient changes can have greater longevity inthe landscape (Bull and Kirkby, 2002; Nanson et al., 2002). Tectonicinfluences have been identified as amongst themost significant allogeniccontrol at the field and at the laboratory scale (Ouchi, 1985).

Digital elevation models (DEMs) have been used extensively toidentify and assess tectonic control on alluvial systems (e.g., Timár,2003; Timár et al., 2005; El Hamdouni et al., 2008; Petrovski andTimár, 2010; Zámolyi et al., 2010; Özkaymak and Sözbilir, 2012; Baghaet al., 2014). We utilize the approaches of Willemin and Knuepfer(1994) and Pearce et al. (2004) applied to digital elevation data. Wefirst mapped the fluvial geomorphological characteristics in the vicinityof a known Quaternary active fold and document the fluvial response.We then use the results to identify similar stream channel responseselsewhere in the Carnarvon alluvial plain and test whether these channelresponses are related to underlying folds.

Our investigation builds on the approach presented by Pearce et al.(2004) for analyzing ephemeral stream response to active tectonics. Wedemonstrate the use of remotely sensed data in recognizing neotectonicstructures in arid land settings and document a regional-scale pattern ofneotectonic deformation in this part of Western Australia.

2. Regional setting

2.1. Geology

The Carnarvon basin contains over 13 kmof Palaeozoic andMesozoicmarine sedimentary rocks overlying crystalline basement (Playford and

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Lyndon Ri

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Minilya River

Ga scoy ne River

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Offshore fault, dashedwhere inferred

Geological Province boundary

Gascoyne Junction

Fig. 1. Map of the study region showing geologic provinces and neotectonic structures.

580 B.B. Whitney, J.V. Hengesh / Geomorphology 228 (2015) 579–596

Johnstone, 1959; Hocking et al., 1987; Hocking, 1990). Near the lowerGascoyne River, the Mesozoic package is about 450 m thick (Allen,1972b). The Cenozoic section consists of over 60mofmarine carbonatesunconformably overlain by terrigenous floodplain deposits (Allen,1972b). The Carnarvon alluvial plain is an aggrading surface with manytens ofmeters of Quaternary alluviumoverlying Cenozoic andCretaceousbedrock (Baxter, 1966; Allen, 1972a,1972b). The entire sedimentarypackage thickens and dips gently to the west.

The Carnarvon alluvial plain is a low-relief feature, dropping ~1 mper 1000 m from the base of the Kennedy Range escarpment to thecoast (Fig. 1). The Kennedy Range escarpment rises abruptly 100 m inelevation and demarcates where west-flowing drainages transitionfrom bedrock to alluvial systems. The Lyndon, Minilya, and Gascoynerivers flow from east to west across the Carnarvon alluvial plain. Therivers locally have incised into older floodplain deposits, but underlyingCenozoic or Cretaceous bedrock outcrops are rare. Near the coast,Pleistocene and Holocene nearshore deposits (beaches and dunes)are preserved.

The most conspicuous surface features on the Carnarvon alluvialplain are NW–SE oriented longitudinal dunes that overlie aggradedalluvial floodplain deposits. The dunes commonly are over 100 kmlong and 10 m high with a ridge-form pattern. The interdune troughscommonly are a fewhundredmeterswide. The troughs locally channelizesurface flow and are dotted with clay pans.

2.2. Tectonics

The western margin of the Australian continent was extendedand thinned during the Late Triassic to Early Cretaceous rifting andfragmentation of Gondwana (AGSO North West Shelf Study Group,1994). Reactivation of Gondwana era rift-related structures is welldocumented in the Carnarvon basin (cf, Clark et al., 2012). The mostrecent structural reactivation is widely attributed to the reorganizationof the northern Australian plate boundary that initiated during theNeogene (Densley et al., 2000; Kaiko and Tait, 2001; Audley-Charles,2004, 2011; Cathro and Karner, 2006; Keep et al., 2007; Hengeshet al., 2011) when the horizontal stress field in the Carnarvon basinrealigned to east–west compression (Hillis and Reynolds, 2000, 2003;Hillis et al., 2008; Müller et al., 2012).

Old rift-related normal structures act as zones of weakness and arebeing preferentially exploited to accommodate crustal shortening(Sykes, 1978; Crone et al., 1997; Cathro and Karner, 2006; Revetset al., 2009; Keep et al., 2012; Müller et al., 2012; McPherson et al.,2013). Former rift-related extensional structures have undergonetransform and contractional reactivation leading to structural inversionof basin sequences (Densley et al., 2000; King et al., 2010).

A system of late Neogene to Quaternary anticlines occurs onshoreandoffshore. The anticlines are commonly developed as fault propagationfolds above blind oblique reverse faults (McWhae et al., 1956; Boutakoff,1963; Hocking, 1988; Hillis et al., 2008). Many of the reactivated faultsshow little evidence for net-reverse slip motion (Iasky and Mory, 1999),indicating either limited reverse slip or recent onset of inversion.

The most topographically expressed folds in the Carnarvon basinoccur in the Cape region and include the Cape Range, Rough Range,Cape Cuvier, Giralia, and Minilya anticlines (Fig. 2). A number ofresearchers have documented the tectonic deformation of the Caperegion and suggest this deformation may be ongoing (Raggatt, 1936;Clarke, 1938; Teichert, 1948; Condon et al., 1955, 1956; Raynor andCondon, 1964; Logan et al., 1970; Hocking et al., 1987; Kendrick et al.,1991; Clark et al., 2012). Folding of the last interglacial shorelinedeposits demonstrates growth of these anticlines through lateQuaternary time (Denman and van de Graaff, 1977; Veeh et al., 1979;Clark et al., 2012; McPherson et al., 2013). The Rocky Pool anticlinelocated southeast of the Cape region is the most prominent structurein the Carnarvon alluvial plain, and late Quaternary deformation hasbeen documented (Allen, 1972a).

2.3. Climate

The Carnarvon alluvial plain is an arid regionwith ~220mm averageannual precipitation and 2900 mm average annual evaporation(Dodson, 2009). Rainfall generally is attributed to tropical depressionsand cyclones and falls in abrupt high-intensity summer downpours(Wyrwoll et al., 2000). As a consequence, precipitation variesconsiderably from year to year. On average, the Gascoyne Riverflows for only 2 to 4 months 1.5 times per year; two years in a decadeit fails to flow altogether (Allen, 1972b). Average annual discharge isbetween ~450 and 864 × 106 m3. However, during major floods itmay exceed 3700 × 106 m3 (Allen, 1972b; Dodson, 2009). Typicallydischarge decreases downstream from flow loss through infiltration(Dodson, 2009). The sporadic and dynamic nature of the GascoyneRiver is illustrated by rainfall data collected over the past century. AtGascoyne Junction (Fig. 1) the average annual rainfall over the pastcentury is 214 mm, whereas the highest recorded daily rainfall duringthe same period is 293 mm (Dodson, 2009).

2.4. Fluvial geomorphology

The Gascoyne River is the longest river inWestern Australia and hasa drainage basin area of ~79,000 km2 (Dodson, 2009). The GascoyneRiver is an ephemeral dryland river and has a dendritic channel form

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Minilya River

Minilya Folds

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ul t

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Fig. 2. SRTM-derived shaded relief digital elevation model of the Cape region: LA, Lyndonanticline.Fold axes from Hocking et al. (1985a).

581B.B. Whitney, J.V. Hengesh / Geomorphology 228 (2015) 579–596

as it drains the southwestern corner of the Pilbara craton and adjacentGascoyne Province. Within the Pilbara craton and Gascoyne Province,the river's course is confined within a low relief bedrock valley with afloodplain that is up to 6 km wide; it has the channel morphology ofan underfit stream.

The Gascoyne and Lyndon rivers transition from bedrock to alluvialchannels where they exit the Kennedy Range. This transition delimitsthe deeply weathered and erosional terrain to the east, from the coastaldepositional and alluvial terrain to thewest. Downstreamof the KennedyRange, the rivers are unconfined alluvial systems with avulsion anddistributary channels (Fig. 3). Across the Carnarvon alluvial plain riversare sand-dominated and meet the general descriptions of types 2 and 4anabranching rivers of Nanson and Knighton (1996); rivers generallyare straight with cohesive banks, vegetated elongate mid-channel bars,and localized in-channel aggradation.

The Gascoyne and Lyndon distributary systems are positive relieffeatures with architecture similar to alluvial fan and deltaic systems.Channels primarily flow in alluvium and are weakly confined byaggraded flood levees. Cross sections normal to the river are convexup and semiconical in form, unlike the trough-like cross-sectionalform typical of valley-confined river systems. Thus, steeper gradientsexist locally on themargins of flood levees comparedwith downstreamor longitudinal gradients.

Key hydrological and geomorphological characteristics of theGascoyne and Lyndon rivers and adjacent smaller fluvial systems are:(i) channels are dry or contain disconnected ponds prior to seasonalflow; (ii) flow is ephemeral and episodic and may initiate with a bore

or debris flow surge; (iii) sediment often is deposited within channels;(iv) antecedent channel conditions direct the flow front or bore;(v) discharge in the main channel may decrease downstream fromflow loss through transmission (infiltration) into channel bed sandsand overflow into distributary channels; and (vi) hydraulic gradientmay exceed stream channel gradient during extreme precipitationevents.

3. Data and research methodology

We utilize both forward and inverse approaches (Willemin andKnuepfer, 1994) to investigate fluvial response to active tectonics onthe Carnarvon alluvial plain. A previously identified tectonic structure,the Rocky Pool anticline, crosses the Gascoyne River and affects itschannel morphology. Yet elsewhere in the study region channel anom-alies and avulsions occur where tectonic features previously have notbeen recognized. Therefore, we systematically analyze the channelresponse to a neotectonic structure (the forward approach) and makeobservations of similar responses elsewhere within the river systemson the Carnarvon alluvial plain (the inverse approach).

To complete this analysis we:

• analyze remotely sensed data and completed field reconnaissancemapping over approximately 25,000 km2 of the onshore Carnarvonbasin

• use SRTM 3 arc second (10 m) digital elevation data to determinechannel architecture and to conduct tectonic and fluvial dimensionalanalysis;

• derive channel cross sections, channel gradients, braiding index, andsinuosity parameters, and develop topographic profiles utilizingsurvey controlled topography and DEMs; and

• compile and review engineering geology reports prepared forabandoned dam projects on the Gascoyne River.

We utilize data collected by the Geological Survey of WesternAustralia in the 1960s to investigate dam sites on the Gascoyne River(Gordon, 1964; Baxter, 1966, 1967a,1967b,1967c, 1968; Wyatt, 1967;Passmore, 1968; Hancock, 1969a,1969b; Allen, 1972a,1972b). The datainclude survey-controlled longitudinal and cross channel profiles,borehole logs, and geological maps. We integrate these legacy data tocomplement our mapping and descriptions of the surficial geology.

We investigate seven locations where fluvial response to tectonicactivity is evident at the channel scale. Channels are divided into 3 to5 reaches based on their planform characteristics. Channel width,sinuosity, and braiding index were measured in each reach wheredata have adequate resolution. We determine braiding parametersfollowing the methods of Brice (1964) and sinuosity parametersafter Friend and Sinha (1997), as modified from Leopold and Wolman(1957). Channel reaches with braiding indexes (BI) N1.5 are consideredbraided. Channel reaches with sinuosity (P) b1.05 are consideredstraight, and P = 1.05–1.3 are described as sinuous (Brice, 1964).

Channel width is delimited by a sharp contact between the drychannel and green vegetated channel banks and mid-channel bars onthe imagery; a marked contrast exists between brown channel beltsand green vegetated channel thalwegs. Sinuosity is calculated basedon the length of the thalweg divided by the length of the channel beltfor individual reaches. The braiding index can be difficult to determineusing imagery because of the ephemeral nature of the streams. Forexample, the number of observable mid-channel bars varies dependingon the flow stage captured in the image. Most often, the channel belt isdry, and individual braids cannot be distinguished. An example of this isshown in Fig. 7 where the bottom portion of the image was capturedduring lower flows than the top portion. Nonetheless, where thebraiding index is determined it provides a tool to compare the planformof successive channel reaches.

Numerous channels

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9

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1213

Fig. 3.Mapof the southern part of the Carnarvon alluvial plain showing someof the structures discussed in text. RP—Rocky Pool; RPA—Rocky Pool anticline; BHA— Brick House anticline;QA— Quarry anticline; YA— Yandoo anticline; MA—Mundary anticline. Blue shows watercourses and Lake MacLeod. Dark gray lines indicate longitudinal dune crests. Numbers withinpolygons indicate corresponding detailed figures.

Lake MacLeod

CARNARVON

Gradational / unclear contact between young avulsion and young floodplain

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Brown channel / delta

Quarry channelOld floodway - relic distributary channels

Old floodplain - undeveloped drainage

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9 Longitudinal dunes (no symbol) (see Fig. 3)

Fig. 4. Geomorphological map of the lower Gascoyne drainage basin (modified from Baxter, 1968). Numbers 1–10 are hydrogeomorphic units of Quaternary age. RP, Rocky Pool; Q, un-named quarry; D, Doorawarrah homestead; FP, Fishy Pool. See Table 1 for unit descriptions.


Table 1Detailed descriptions of geomorphic units shown in Fig. 4.

(1) Young avulsion: The most recent avulsion and distributary channel of the Gascoyne River system is just north and upstream of Rocky Pool. A 23-km-long distributarychannel flows northwest from Rocky Pool and floods-out prior to reaching the coast or Lake MacLeod. Avulsion occurs when discharge through the main channel becomesconstricted at Rocky Pool and overflows through the young avulsion channel. The channel has a similar expression as the channels on the young floodplain (unit 2) with theexception that the Gascoyne has not constructed a levee at its spillover.

(2) Young floodplain: The young floodplain covers ~1000 km2. Runoff across the floodplain initiated from the Gascoyne River at a number of spillover locations. The GascoyneRiver has constructed flood levees at the heads of the spillover locations and no longer flows into the channels. These relic channels carry water during precipitation events butflow is generated locally.

(3a) Quarry channel: The Quarry channel is a 10-km-long avulsion channel that flowed northwest from the Boodalia channel. The avulsion node is at an unnamed sand andgravel quarry ~15 km east of Carnarvon. The avulsion channel has a meandering morphology prior to terminating at flood-outs east of Brown Range.(3b) Gascoyne terrace: The Gascoyne Terrace extends ~18 km along the Gascoyne River across the Rocky Pool anticline. The terrace may have developed during episodicavulsions from the Boodalia channel. Once the Gascoyne became the main river channel, flow incised through the terrace deposits.(4) Boodalia channel and delta: The Boodalia channel is a 58-km-long southwest trending paleochannel that flowed to the Boodalia delta. The channel initiates at Rocky Poolwhere it diverges southwest from the main stem of the Gascoyne River. The main channel is relatively straight with a meandering thalweg, similar to the modern GascoyneRiver. Multiple avulsions and multiple distributary channels flow from the Boodalia channel and most are weakly developed, short, flood-levee overflows. The Gascoynechannel was a successful avulsion event from the Boodalia channel. The Boodalia delta is Pleistocene age, tentatively correlated to the Marine Oxygen Isotope stage 5e (MIS)sea level highstand that occurred ~125 ka.

(5) Intermediate floodplain: The intermediate floodplain is a 400-km2 feature on the north side of the Gascoyne River adjacent to Rocky Pool. The surface is internally drainedand contains a number of disconnected clay pans.(6) Brown channel and delta: The Brown channel is an 80-km-long southwest trending paleochannel that flowed to the Brown delta. The Brown channel diverges from themain stem of the Gascoyne River at two locations ~20 and 40 km upstream of Rocky Pool. The channels are anabranches of the same system and rejoin downstream. Thechannel morphology of the anabranches is similar to the old floodway (8a). It has short discontinuous channels and numerous clay pans within a floodway that traverses anddissects the longitudinal dune field. The channel and delta aggraded over 6 km from the Brown Range. Although the channel has incised through the Brown Range, it nolonger reaches the coast. It is a single channel, positive relief feature with bars and levees perched above the adjacent floodplain downstream from where its anabranchesmerge. The Brown delta is Pleistocene age, tentatively correlated to the MIS 7 sea level high stand (Hocking et al., 1987).

(7) Brown Range: The Brown Range comprises a series of beach ridges that parallel the coast just east of the town of Carnarvon. The ridges are up to 20 m high and representformer coastal dune fields. The Brown Range is interpreted as representing MIS 7–240 ka interglacial beach complex (Hocking et al., 1987).(8a) Old floodway: The old floodway is a poorly developed channel system that flows from where the river exits the Kennedy Range to the shore of Lake MacLeod. The oldfloodway consists of a poorly developed distributary network with two main anabranches. The anabranches traverse and dissect the dune field (Fig. 4) and are characterized bynumerous clay pans and short discontinuous channels.

(8b) Old floodplain: The old floodplain is adjacent to the middle and lower reaches of the old floodway. The floodplain contains the footprints of eroded longitudinal dunes.Local clay pans and intermittent ponds are numerous.(9) Longitudinal dunes: Longitudinal dunes cover the oldest floodplain. Dunes are generally oriented northwest-southeast (Fig. 4). Dune crests have an anastomosing patternwith intersecting crests and are often continuous with lengths up to 120 km. The dunes are up to 15 m high and fixed with low scrub and spinifex. Locally interdune troughshave directed and channelized sheetwash surface flow. Numerous clay pans and intermittent ponds dot the floodplain within interdune troughs. Clay pans are moreabundant near active channels. In some locations, the anastomosing pattern of the dunes has created small dune-bounded basins containing clay pans.

(10) Oldest floodplain: The oldest floodplain slopes gently westward dropping ~1 m per 1 km from the Kennedy Range to the coast and locally is weakly incised by the modernGascoyne River. This surface is the top of the Gascoyne alluvium or Pleistocene flood deposits of Allen (1972a). It contains poorly developed and discontinuous east–westoriented distributary drainage networks. Portions of the floodplain surface are internally drained and numerous channels start and stop abruptly. The channel network is arelic feature locally buried by longitudinal dunes.


4. Results

4.1. Surficial geology of the Carnarvon alluvial plain

Three principal fluvial stratigraphic complexes are recognizedon the Carnarvon alluvial plain: active channels, older channels,and floodplains. Active channels include the main stem of theMinilya, Lyndon, and Gascoyne rivers and the young avulsion chan-nel that leaves the Gascoyne River to the north at Rocky Pool; RockyPool is a perennial water hole just downstream of the Rocky Poolanticline on the Gascoyne River. Older channels include the oldfloodway, Brown, Boodalia, and Quarry channels (Fig. 4). Theolder channels act as local catchments and carry flow duringstorm events, but they are relic features. Floodplains are broad allu-vial surfaces where sheetwash is the dominant surface flow processand that contain localized depressions that pond water and formclay pans.

The three principal fluvial stratigraphic complexes (activechannels, older channels, and floodplains) are subdivided into 10distinct time-stratigraphic geomorphic units (Fig. 4, Table 1).The units represent four temporally distinct drainage configura-tions that existed on the Carnarvon alluvial plain. These arethe old floodway and the Brown, Boodalia, and Gascoyne riversystems.

4.2. Neotectonic structures

Seven locations with evidence of neotectonic activity have beenidentified (Figs. 2 and 3) and are discussed below.

4.2.1. Rocky Pool anticlineThe Rocky Pool anticline, as mapped by Allen (1972a), is a fault-

cored fold that strikes northeast (N. 20o E.) transverse to the east–west orientation of the Gascoyne River (Fig. 5). The anticline is themost prominent topographic feature that crosses the Carnarvonalluvial plain. It is cored by Cretaceous calcilutite, which is exposedin the Gascoyne River channel (Fig. 6). The fold is asymmetricalwith a steeper dip on the eastern limb (Fig. 7) (Baxter, 1967b). Thecalcilutite is overlain by Cenozoic siltstone, Cenozoic–Quaternarysandstone, and Quaternary alluvium (Baxter, 1966) (Figs. 6 and 7).Borehole data indicate the depth to the top of the Cretaceous abruptlyincreases upstream and downstream of Rocky Pool (Baxter, 1967a).Quaternary alluvium on both sides of the structure is about 45 m thick,whereas alluvium overlying the structure is 3 m or less (Allen, 1972a).

Hancock (1969b) and Allen (1972b) surmise that the Rocky Poolanticline is an actively growing structure in light of progressive defor-mation of the stratigraphy. The Cenozoic–Quaternary sandstone has amaximum dip of 12°E on the eastern limb (Fig. 7) and is less foldedthan the Cenozoic siltstone, which has a maximum dip of 24°E on theeastern limb (Hancock, 1969a). Laterization of the siltstone pre-datesthe onset of folding as indicated by deformation within the laterizedunit (e.g., boudins) (Hancock, 1969a). In addition, the Quaternaryalluvium overlying the structure appears slightly folded (Allen,1972a). This suggests at least three episodes of deformation: one afterlaterization of the Cenozoic siltstone yet prior to deposition of thesandstone; one after deposition of the sandstone yet prior to depositionof the alluvium; and one after deposition of the alluvium.

The Gascoyne River channel characteristics change across theQuaternary Rocky Pool anticline. At Rocky Pool the channel narrows

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Fig. 5. SRTM-derived digital elevation model of the Gascoyne River and Rocky Pool anticline.


dramatically and incises through the anticline (profiles 21 to 24 inFig. 8). The channel is sinuous both upstream and downstreamof Rocky Pool and is straight across the anticline axis (Table 2).The channel gradient decreases across the anticline; however, theadjacent floodplain surface gradient increases from east to westacross the fold axis (Table 2).

Repeated avulsions have occurred near Rocky Pool. Approximately3 km upstream from Rocky Pool, the Gascoyne River diverges fromthe abandoned 2-km-wide Boodalia channel (Fig. 6). The Boodaliachannel was formerly the main river channel on the Carnarvon alluvialplain (unit 3, Fig. 4). Less than 1 kmupstreamof Rocky Pool on the northbank of the river, a young avulsion channel (unit 1, Fig. 4) cuts intobedrock near the crest of the anticline (Fig. 6 and 7). The elevationsof the young avulsion spillover and the Boodalia channel spilloverare at elevations of ~44 and 46 m, respectively; the elevation ofRocky Pool is 35 m. This indicates overflow from the GascoyneRiver into the young avulsion channel will occur at lower flowsthan overflow into the Boodalia channel.

4.2.2. Rocky Pool anticline (north)The Rocky Pool anticline north of Rocky Pool is expressed at the

surface as a series of low-relief Cenozoic siltstone hills (unit III,Fig. 4) that project through the old floodway (unit 8a, Fig. 4). A 1-km-wide band of aligned siltstone ridges outcrop over 30 km in a northeastdirection then step to the west and continue north for another 20 km(Fig. 5). The elevations of the outcrops increase away from the riverfrom ~55 m adjacent to Rocky Pool to 70 m near the left stepover(Figs. 6C and 9C). Likewise, the heights of their crests above the alluvial

surface increase from 5 m near Rocky Pool to 10 m at the stepover.North of the left stepover, the topography of the northern segment ofthe structure is more subdued and is partially covered by longitudinaldunes (Fig. 5).

The Rocky Pool anticline is crossed by wind and water gaps. The oldfloodway (unit 8a, Fig. 4) crosses the Rocky Pool anticline at a number oflocations. At each location the floodway narrows across the anticlineaxis then widens (fans out) downstream.

The northernmost exposure of the main fold segment is partiallydissected by westward- and eastward-flowing consequent streams oneither side of the fold axis (Fig. 9B). The quantity, maturity, and densityof these streams increase along strike from south to north away from theGascoyneRiver. Supercedent streams (reflecting combined superpositionand antecedence) are deflected along the base of the fold, then flowacross the fold through water gaps, narrowing through the fold axis. Atsome locations ponded water is damned upstream of the fold. Claypans are numerous upstream (east) of the Rocky Pool anticline wherethe gently westward sloping surface gradient of the old floodplain andold floodway have ponded sheetflow along the eastern limb of the fold.

4.2.3. Brick House anticlineThe Brick House anticline is located 15 km east of the town of

Carnarvon (Fig. 3). It is expressed as a subtle ridgeline that trendsnorth–south for ~25 km north of the Gascoyne River. The ridgeline isa remnant of the oldest floodplain (unit 10, Fig. 4) that is preserved ata higher elevation than the adjacent young floodplain (unit 2, Fig. 4).

A seismic survey conducted in 1964 (Raitt and Turpie, 1965)traversed a structure we herein refer to as the Brick House anticline.

E114 10’o

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Siltstone Boodalia Channel Flood surfaces/Terraces

Boodalia Channel

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s) Anticline crest

A

B

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Axis of anticline

5 kmA

C

Clay panChannel

D

B

YA

AC’

CC”

B

Fig. 6. Annotated aerial photograph, geomorphic sketch map, and topographic profiles near Rocky Pool. A) Annotated air photo of a portion of Rocky Pool anticline and Gascoyne Rivershowing the location of topographic profiles A–A′ and B–B′ across the topographic high and channel; RP— Rocky Pool; YA— young avulsion. B) Geomorphic map of Rocky Pool anticline.C) Topographic profile A–A′ across the ridge crest and adjacent slopes. D) Topographic profile B–B′ transverse to the Gascoyne River showing inset terraces.


The seismic transect (Raitt and Turpie, 1965, Plate 2) shows a gentle foldwith an axis that is aligned with the ridgeline. The dip angles of seismichorizons change from~1°west to 5° east across the BrickHouse anticline(Raitt and Turpie, 1965). Folded strata are evident in the seismic data,but poor data resolution prevents interpretation of the shallow section.

Channel gradient and planform adjust across the ridgeline (Fig. 10;Table 2). Upstream of the Gascoyne River bridge the main GascoyneRiver channel widens, aggrades, and becomes braided (BI= 2.5) beforeabruptly narrowing along an irrigated stretch of farmland (reachA) (profiles 2 to 4 on Fig. 8; and Fig. 10). The river channel narrows,straightens (P = 1.04), and decreases gradient across the Brick Houseanticline (reach B) compared to upstream (P= 1.06) and downstream(P= 1.09) reaches (Table 2). A 5-km-wide abandonedmeander terraceis preserved along the south bank of theGascoyne River upstreamof thefold axis. Channel characteristics reflect aggradation upstream (reach

A A’

Alluvium (Quaternary)

Sandstone (Cenozoic)

Siltstone (Cenozoic)

Calcilutite (Cretaceous)

24 o

12 o

~15

m

Schematic geologic cross-section A-A’

Unconformity

Fig. 7. Schematic geologic cross section across the Rocky Pool anticline. Oblique aerial Gonorthwest. RP — Rocky Pool; F — small tributary channel flows east during low flows. Riv

A) and downstream of the axis (reach C) and incision through theanticline (reach B).

Several distributary channels that drain local runoff incise throughthe axial ridgeline (unit 2, Fig. 4). Upstream of the fold axis, the chaoticchannel network on the floodplain is dendritic and consolidates to fourmain antecedent channels that cross the ridgeline. The four channelsstraighten and narrow across the axis and fan out downstream.

4.2.4. Yandoo anticlineThe Yandoo anticline forms the northernmost left step over from the

Rocky Pool anticline (Fig. 3). It is expressed as a subtle 17-km-long axialridgeline that trends in a north-northeast direction. The ridgeline iswithin the dune-covered oldest floodplain (unit 10, Fig. 4). The axialridgeline affects the course and planform of Yandoo Creek.

Young

Avulsion Channel s

RP

Zone of aggradation

F

A

A’

Avulsion sill

Rocky Pool anticline

ogle Earth® image of Rocky Pool. View is downstream, approximately to the west–er is 70 m wide at RP.

Doorawarrah

Fishy Pool

3

12

21

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3525

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Quarry anticline

Boodalia Channel

Gascoyne River

Young Avulsion

Rocky Pool

Quarry anticline

Brick House anticline

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60.26

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74.44

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Rocky Pool a

nticline

Fig. 8. Cross sections along the lower 70 km of the Gascoyne River (redrawn from Allen, 1972b). Bolder numbers are the profile numbers. Numbers on the lower left indicate distance inkilometers from the river mouth. Gray polygons are channel sands (mobile). Ticks along river trace correspond to specific cross sections. Relative fold axis locations delineated with an-ticline symbols on the river trace and within the cross sections. Inset DEM is a portion of Fig. 5 showing the young avulsion channels and the Boodalia channel heading from the avulsionnode at Rocky Pool.


Yandoo Creek is one of a number of ephemeral systems that drain thewestern escarpment of the Kennedy Range (Fig. 3). Themain stem of thecreek is ~100 km long and its upper catchment has a well-developeddendritic drainage pattern. Upon exiting the Kennedy Range and enteringthe Carnarvon alluvial plain, Yandoo Creek flows northwest and ischannelized within an interdune trough (Fig. 11). The channel turnsabruptly (N90°) to the south-southwest and flows transverse to thelongitudinal grain of the dune field for ~8 km. It then turns abruptly(~90°) to the northwest. At this bend the channel cuts obliquelyacross the dune field for 8 km until it again becomes confined withinan interdune trough. The end of the channel floods-out within thedune field (Fig. 11).

The conspicuous bends in Yandoo Creek are alignedwith the left stepover north of the Rocky Pool anticline, 15 km north of the northernmostsiltstone outcrop. The Yandoo anticline deflects the creek channel at thislocation.

The Yandoo Creek channel is straight (P= 1.03) and confined withinan interdune troughupstreamof the Yandoo anticline (reachA) (Table 2).It widens, decreases in gradient, and becomes braided (BI = 2) withincreased sinuosity (P = 1.13) along the base of the anticline (reach B).The creek has a single relatively straight channel (P = 1.06) around thefold axis (reach C). Downstream along reach D the channel gradientincreases and it has a distributary network.

The oldest floodplain (unit 10, Fig. 4) slopes gently from east towestexcept where interrupted by the Yandoo anticline. Clay pans andephemeral ponds are concentrated along the eastern base of the fold.

4.2.5. Mundary anticlineTheMundary anticline is the easternmost topographically expressed

fold in the Carnarvon alluvial plain (Fig. 12). It trends northeast for~30 km as a subtle ridge in the old floodplain north of the GascoyneRiver (Fig. 3). The axial ridgeline affects the channel planform ofMundary Creek.

Mundary Creek is one of the main drainages along the westernescarpment of the Kennedy Range (Fig. 3). Its main tributaries have

well-developed dendritic drainage networks in the upper parts oftheir catchments. The north fork of Mundary Creek flows fromnorth to south along the eastern base of the axial ridgeline and hasan asymmetric drainage pattern with all of its major tributariesentering it from the east (Fig. 12).

Individual tributaries of Mundary Creek have distributary channelsthat fan out across 30 km2 forming a zone of aggradation upstreamof the anticline (Fig. 12B). Downstream of this zone of aggradation,the forks join and flowwest through a 1400-m-wide braided channelnetwork. The planform of the channel's lowest 23 km (reaches A, B,and C; Fig. 12) systematically changes as it flows across the foldaxis. Upstream of the fold, the channel is steep, narrow, and sinuous(P= 1.14) (reach A) (Table 2). The channel gradient decreases and isbraided (BI = 2) where it crosses the fold (reach B). The creek is asingle straight channel (P = 1.01) for 2 km downstream of the fold(reach C), then distributes into three floodout channels in the dunefield (reach D).

The oldest floodplain (unit 10, Fig. 4) slopes gently from east to westexcept where interrupted by the Mundary anticline (profile F–F′,Fig. 12C). Clay pans are concentrated along the base of both fold limbs.The channel planform of the old floodway between the GascoyneRiver and Mundary Creek also shows a pattern of channel wideningand aggradation upstream and downstream of the fold and channelnarrowing and incision through the fold axis (Fig. 12A).

4.2.6. Quarry anticlineThe Quarry anticline is located between the Brick House and Rocky

Pool anticlines and affects the channel planform of the Gascoyne Riverand Boodalia channel (Fig. 3). The anticline is ~12 km long and trendsin a north-northeast direction. Its length and location are inferred fromaligned channel planform changes that follow the regional structuraltrend.

The Quarry avulsion formed three channels that exit thewest side ofthe Boodalia channel at an unnamed sand and gravel quarry (Fig. 13).The three anabranching channels are weakly incised (b1 m) through

Table 2Channel parameters near anticlines.

East Anticlines West

Rocky Pool anticline

Gascoyne River Reach A Reach B Reach C Reach C´ Reach C´´

Gradient 0.0010 – 0.0008

width (m) 1200 70 300

P 1.09 – 1.15

B.I. 2.5 0 2.3

Boodalia channel

Gradient – – – 0.0010

Young avulsion channel

Gradient – – – – 0.0012

Intermediate floodplain

Gradient 0.0006 – 0.0008


Gascoyne River Reach A Reach B Reach C

Gradient 0.0012 0.0008 0.0008

Width (m) 915 200 400

P 1.06 1.04 1.09

B.I. 2.5 0 0

Yandoo anticline

Yandoo Creek Reach A Reach B Reach C Reach D

Gradient 0.0011 0.0009 0.0011 0.0012

Width (m) 210 1000 200 dist.

P 1.03 1.13 1.06 –

B.I. – 2 0 –

Mundary anticline

Mundary Creek Reach A Reach B Reach C Reach D

Gradient 0.0020 0.0014 0.0023 –

Width (m) 90 1410 160 dist.

P 1.14 1.10 1.01 –

B.I. – 2 0 –

Quarry anticline

Boodalia – Quarry channels Reach A Reach B Reach C Reach D Reach E

Gradient – – – – –

Width (m) 300 1000 900 500 110

P 1.17 1.14 1.02 1.20 –

B.I. 2.1 4 4.2 0 –

Gascoyne River Reach A Reach B Reach C Reach D

Gradient – – –

Width (m) 515 820 580 610

P nd 1.13 1.03 1.05

B.I. 2.2 3.6 0 –

Lyndon anticline

Lyndon River Reach A Reach B Reach C Reach D

Gradient 0.0012 0.0005 0.0016 –

Width (m) 160 70 180 dist.

P 1.09 1.05 1.06 –

B.I. – – – –

B.I. is braiding index. P is sinuosity. Braiding index “0” indicates no mid-channel bars were observed in the reach. (–) indicates either no data were available or no measurements weremade. Dist. indicates reach is distributary. Gray and italicized cells indicate fold axis locations.


the adjacent floodplain. A topographic profile adjacent to the Quarry andBoodalia channels shows a subtle convexity (topographic high) coinci-dent with the avulsion location (Quarry channel reach C) (Fig. 13).Along reach A, the Boodalia channel is 300 m wide and sinuous (P =1.17) upstream of the Quarry avulsion (Table 1). The channel widens atthe Quarry, becomes braided (BI = 4), and remains sinuous (P = 1.14)(reach B). The three anabranching avulsion channels are straight (P =1.02) for ~2 km (reach C) then join together into a sinuous channel(P= 1.20) downstream (reach D). The Quarry channel has a distributarynetwork and floods-out east of the Brown Range (reach E) (Fig. 13).

The Boodalia channel is deflected south along the eastern limb of thefold at the Quarry (Fig. 13). The thalweg along this part of the channel isless sinuous than elsewhere and is confined along the eastern channelbank—deflected away from the fold.

The northern end of the Quarry anticline intersects the GascoyneRiver (reach B). Across the fold axis in Reach B the Gascoyne Riverwidens and becomes braided (BI = 3.6; P = 1.13) (Table 2).Downstream of the fold axis in reach C, the river narrows andstraightens (P = 1.03). In reach D, the channel widens and sinuosityincreases (P=1.20). Reach D in part could be responding to the change

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Fig. 9.Annotated aerial photograph, geomorphic sketchmap, and topographic profiles along the northern end of the Rocky Pool anticline. A) Annotated air photo of a portion of Rocky Poolanticline showing the location of topographic profile C–C′ across the topographic high. B)Geomorphicmap of the northern extent of the Rocky Pool anticline. Note the consequent streamson the fold limbs. C) Topographic profile C–C′ across the ridge crest and adjacent slopes.


in gradient associated with the downstream Brick House anticline(profiles 10 to 12 in Fig. 8).

4.2.7. Lyndon anticlineThe Lyndon anticline is located in the northern Carnarvon alluvial

plain (Fig. 2). Folded Miocene Trealla limestone is exposed near thefold axis along the river bank (Fig. 15). The Lyndon anticline overliesthe steeply westward-dipping Marilla fault (Fig. 2) (Crostella, 1995).The anticline has formed an 18-km-long by 5-km-wide ridgeline thatis oriented north–south, perpendicular to the surface gradient of theCarnarvon alluvial plain and the flow direction of the Lyndon River(Hocking et al., 1985a).

The Lyndon River flows west across the Lyndon anticline anddischarges into the northern end of Lake MacLeod (Fig. 2). The riverflows for over 100 km through bedrock highlands and across the alluvialplain then desiccates via an alluvial fan distributary channel network. It isdiscontinuous across a 2-km-long channel gap between its upstream anddownstream channelized reaches. Near this location, Cardabia Creekflows into the Lyndon River from the north (Fig. 14). A zone of aggrada-tion occurs at the confluence of Cardabia Creek and the Lyndon River.

The Lyndon River narrows, straightens (P = 1.05), and decreaseschannel gradient across the fold axis compared with upstream anddownstream reaches (P = 1.06 and P = 1.09, respectively) (Table 2).The channel form is distributarywith a down gradient elongated conicalfan shape downstream of the fold (reach C). In reaches A and B, the riverhas incised through a terrace. Channel characteristics reflect aggradationfollowed by incision upstream of the fold axis.

The Lyndon River has a conspicuous S-shaped curve near its mouthwhere it bends around the tips of two topographically prominent

anticlines (two of theMinilya folds) (Fig. 2). The Lyndon River is anteced-ent through the Lyndon anticline, yet downstream it is supercedentaround the tips of theMinilya folds (Figs. 2 and15). Prominent differencesin channel responses are observed at these two locations as the Minilyafolds are more topographically expressed than the Lyndon anticline.Approximately 4 m of relief is measured across the Lyndon anticlineadjacent to the river, whereas 6 and 15 m of relief are measured acrossthe tips of the Minilya folds (Fig. 14).

5. Discussion

The response of the rivers to tectonic deformation has a majorrole in the overall late Neogene to Quaternary evolution of theCarnarvon alluvial plain. Fluvial geomorphology of major streamsand rivers demonstrate late Neogene to Quaternary active folding. Sixtectonic structures that have influenced fluvial dynamics are identifiedincluding: Rocky Pool, Lyndon River, Mundary, Yandoo, Quarry, andBrick House anticlines. Each of these structures has affected channelmorphology, gradient, sediment carrying capacity, and avulsion historiesof the respective streams. The folds have caused river avulsions that ledto large-scale channel abandonment and channel migration across theplain.

5.1. Response of ephemeral river channels to active tectonics

A pattern of geomorphological responses to changes in fluvialdynamics across neotectonic folds is recognized in the Carnarvon alluvialplain. These geomorphological responses were initially validated at theRocky Pool anticline and subsequently used to identify other neotectonic

E113 50’o

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Channel

Axis of ridge crest

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CGascoyne River

Boodalia Channel

Old floodplain (remnant) Terrace

Coastal H

wy

Brick House (approx.)A B

C

D

D’

5 km

1o 5oSeismic transect

1o 5oSeismic transect

1o 5o Dip of horizons on seismic transect (Raitt and Turpie, 1965)

Fig. 10. Annotated aerial photograph, geomorphic sketch map, and topographic profiles along the Brick House anticline. A) Annotated air photo of a portion of Brick House anticline andGascoyne River showing the location of topographic profile D–D′ across the topographic high and seismic transect fromRaitt and Trupie (1965) showing dip angles. B)Geomorphicmap ofBrick House anticline showing the three stream reaches (A–C) discussed in text. C) Topographic profile D–D′ across the ridge crest and adjacent slopes.


structures in the area. Most structures are traversed by multipledrainages, and channel response on any given feature is a functionof the drainage characteristics and the underlying fold. Aligned changesin channel planform characteristics across multiple channel-fold inter-sections provide geomorphological evidence for the location andorientation of neotectonic structures.

Pearce et al. (2004) provided a conceptualmodel for how ephemeralchannel patterns adjust as a function of tectonic and fluvial controls.Weexpand on thismodel to conceptually illustrate awider range of channelresponses.We present seven idealized channel responses to uplift alongdiscrete neotectonic structures oriented transverse to flow direction(Fig. 15). Channel responses are a function of the tectonic deformationrate and the fluvial rate. The tectonic deformation rate in this area isexpressed as growth of a fold, while fluvial rate is a function of flowfrequency, discharge, and stream power. Seven stages are presentedthat illustrate the variability in the spectrum of response from completetectonic control (Fig. 15A), in which flow is halted and a lake or pond isformed upstream of the fold, to complete fluvial control (Fig. 15G) inwhich the channel is not affected by the fold.

Observed channel responses that correspond to the seven-stagemodel are summarized below:

• Rocky Pool — antecedent channel aggrades and channel widensupstream of the fold and incises across the fold axis (Fig. 15D)

• Rocky Pool north — supercedent channels divert around foldsegments (Fig. 15B)

• Brick House — channel widens and aggrades upstream of the foldaxis, and channel narrows across the fold; smaller channels fanout and distribute flow downstream of the fold axis (Fig. 15D, E)

• Yandoo Creek— channel aggrades upstream of fold axis, locally ponds,and diverts around and aggrades downstreamof the fold (Fig. 15A, B, E)

• Mundary Creek — channel aggrades upstream of fold axis, divertsaround the fold, widens, braids, and aggrades across fold axis anddistributes downstream of the fold (Fig. 15B, C, E);

• Quarry — Boodalia channel widens upstream and is deflected by thefold (Fig. 15B); Gascoyne channel widens and aggrades across the foldaxis (Fig. 15C); and,

• Lyndon River — channel narrows and incises across the fold axisand uplift causes terrace formation (Fig.15F); channel fans outand distributes downstream of the fold axis (Fig. 15E).

The fluvial responses to folds on the Carnarvon alluvial plainindicate that the rate of fold growth is sufficient to affect the planformof the ephemeral rivers and creeks. A similar example of dryland riverresponse to active tectonics occurs in the region at Lake Wooleen onthe Roderick and Murchison Rivers (Clark, 2004; Hengesh et al., 2011;Whitney and Hengesh, 2013). Lake Wooleen is an example of a riverponding upstream of a fold, and tectonically influenced drainagesin the area exhibit a spectrum of stream responses as illustrated inFig. 15A–F.

5.2. Avulsion

Avulsion has played a major role in the fluvial geomorphic devel-opment of the Carnarvon alluvial plain. Avulsion is a response offluvial channels to growth of folds as the stream gradient lowersand deposition chokes the channel (Fisk, 1952; Allen, 1965).Repeated avulsion events can occur at nodes where aggradation inthe channel raises base level to a sill, which the river eventuallyoverflows as a new avulsion channel. Channel aggradation andconstriction upstreamof the folds on theGascoyne Riverwere sufficientto trigger avulsion events.

E

E’

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1000 2000 3000 4000 5000 6000 7000 8000 8000

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ABCD

Yandoo Creek

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Yandoo Creek

A

C

E

E’

5 km

Flow direction

Fig. 11.Annotated aerial photograph, geomorphic sketchmap, and topographic profiles along the Yandoo anticline. A) Annotated air photo of a portion of Yandoo Creek showing the locationof topographic profile E–E′ across the topographic high. B) Geomorphicmap of Yandoo Creek showing the four stream reaches (A–D) discussed in text and the location of topographic profileE–E′ across the topographic high. C) Topographic profile E–E′ across the ridge crest and adjacent slopes.


The locations of avulsions include:

• Gascoyne avulsion from Boodalia channel: upstream from the RockyPool anticline the Gascoyne River avulsed from the Boodalia channeland trends 295°.

• Young avulsion at Rocky Pool: two anabranching distributary channelsavulse from the Gascoyne River upstream of Rocky Pool and trend300°.

• Quarry channel avulsion from the Boodalia channel: at the Quarry,three anabranching channels avulse from the Boodalia channel andtrend 265°.

Avulsion by progradation (Slingerland and Smith, 2004) is thedominant avulsion style in the study region. Once the avulsion channelis diverted from the parent channel onto an adjacentfloodplain, sedimentcarrying capacity is dramatically reduced: deposition is rapid, and aconical or fan-shaped sediment wedge progrades down-gradient fromthe avulsion overflow. Ultimately, this can progress to the completeabandonment of the parent channel, as occurred at the Boodalia channel,and development of a new channel network downstream of the avulsionoverflow (e.g., the Gascoyne River avulsion at Rocky Pool).

Fig. 16 illustrates our four-phase model that describes the processof avulsion observed on the Carnarvon alluvial plain. This four-phaseprocess is described below:

Phase I channel aggradation. Phase I is initiated by an event(e.g., folding) that reduces channel gradient and triggersaggradation. As shown in Figs. 6 and 13, this occurredupstream of Rocky Pool and Quarry anticlines.

Phase II the avulsion event. A channel bank is breached, and overflowof the river is diverted onto the floodplain such as where theQuarry channel avulsed from the Boodalia channel or wherethe Gascoyne avulsed from the Boodalia channel.

Phase III incision of the avulsion sill following overflow. Incision canbe abrupt and occurs during Phase II, or can be gradual andoccurs episodicallywhere subsequent spillovers at the avulsionoverflow incrementally lower the sill elevation. An example ofthis is seen at the young avulsion overflow at Rocky Pool.

Phase IV formation of a new channel. A new channel is established down-stream of the avulsion overflow, such as the Gascoyne channelavulsion from the Boodalia channel.

Fig. 7 shows an example of the failed avulsions of Guccione et al.(1999) and Makaske (2001) at Rocky Pool where avulsion occurred,incised a new channel, and deposited sediments on the downstreamfloodplain, but the original channel was not abandoned. In this instancethe failed avulsion channel may act as a distributary channel duringfuture high discharge events, but it has not become the primary channel.This is phase III in our process model. The onset of phase IV occurs whenthe avulsion channel becomes the primary channel and the old channelbecomes the subordinate channel, such as the Gascoyne avulsion fromthe Boodalia channel.

Phase II occurs instantaneously, whereas phases I, III, and IV requireaggradation, erosion, and new channel development and old channelabandonment, respectively. In ephemeral systems, this provides acontext to establish relative age control of avulsion features wherethey are numerous and interfingered, as observed on the lowerGascoyne River. In ephemeral systems, multiple flood (or flow) eventsoften are required to work through three of these four phases of theavulsion cycle, and therefore the term failed avulsionmay bemisleading.If phase III is repeated through multiple flooding events, then eachsubsequent episode of incision brings the avulsion closer to reachingphase IV, resulting in final channel abandonment. Therefore, some failedavulsions may more accurately be considered incipient phase IIIavulsions (Fig. 16).


5.3. Neotectonic deformation of the Carnarvon alluvial plain

Based on the relative positions of the paleochannel complexes andobserved processes, we suggest the following model for evolution of theCarnarvon alluvial plain. The old floodway (unit 8a of Fig. 4) is the oldestprimary paleochannel. This channel flowed in a northwest direction(310°) toward Lake MacLeod; a fundamentally different direction thanthe southwest-flowing Brown, Boodalia, and Gascoyne channels. Wesuggest that theflows in the oldfloodwaywere diverted to the southwestby growth of the north-northeast trending Rocky Pool anticline across theCarnarvon alluvial plain. An avulsion formed the Brown River and flowedsubparallel to the strike direction of the Rocky Pool anticline. Theeastward-dipping limb of the anticline and southward plunge imposeda structural control on the direction of flow and deflected the BrownRiver, similar to model (b) in Fig. 15. The avulsion event that formed theBrown paleochannel occurred 20 to 35 km upstream from the RockyPool anticline, and therefore most likely occurred at a lower stand of sealevel when the river was graded to a lower base level and the structuralrelief of the Rocky Pool anticline was more pronounced.

As sea level rose, the fluvial rate will have decreased with reductionin gradient of the Brown River. This may have caused a decrease insediment carrying capacity and channel aggradation, especially nearthe Doorawarrah homestead (Fig. 4). The river then completed anavulsion on the north side of the Brown River channel forming theBoodalia channel. The new ~125-ka Boodalia channel (Hocking et al.,1985b) extended from Doorawarrah homestead downstream 30 km toRocky Pool in a westward direction, but once encountering the RockyPool anticline again deflected southward. The new Boodalia channelturned southwest and roughly followed the axial trend of the RockyPool anticline. Channel aggradation at a higher sea level stand wouldhave attenuated the structural relief of the anticline. This is consistentwith the Brown-to-Boodalia avulsion occurring at a higher sea levelstand than the old floodway-to-Brown avulsion.

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F’

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126

122

1000 2000 3000 40000Ele

vatio

n (m

eter

s)

Distance (mete

F Ridge cre

A B

C

5 km

Fig. 12. Annotated aerial photograph, geomorphic sketchmap, and topographic profiles along thRiver showing the location of topographic profile F–F′ across the topographic high. Note the claying the three stream reaches (A–C) discussed in text and the location of topographic profile F–F′slopes.

While the Boodalia Riverwas the dominant channel on the Carnarvonalluvial plain, it developed a sinuous thalweg and delta system. Anavulsion occurred along the Boodalia channel at the Quarry site. Thisavulsion again occurred off the north side of the channel, and the avulsionchannel again began to flow to the west. The Quarry channel is lockedin phase III of the avulsion cycle since the Boodalia channel becameabandoned upstream.

The Gascoyne River formed as a result of an avulsion that occurredoff the north side of the Boodalia channel at Rocky Pool. The Boodalia–Gascoyne avulsion was successful; it is in phase IV of the avulsioncycle. The Gascoyne channel established itself with a more westwardazimuth (260°) than the southwest-directed (240°) Boodalia channel.The most recent avulsion event also occurred on the north side of theGascoyne channel at Rocky Pool. The avulsion channel trends to 285°and is directed toward Lake MacLeod. This recent avulsion is in phaseIII of the avulsion cycle.

The smaller structures such as the Yandoo and Lyndon anticlines alsohavemade an important contribution to the overall fluviomorphologicaldevelopment of the Carnarvon alluvial plain. All of the smaller channelsthat are diverted around the anticlines revert to a west or northwestdirection toward Lake MacLeod after circumventing the fold.

Fluvial responses enable recognition of anticlines affecting fluvialgeometry on the Carnarvon alluvial plain. Fold axial locations areinterpreted from multiple lines of geomorphic evidence includingtopographic ridgelines on the alluvial plain, stream gradient changes,abrupt changes in stream flow direction, systematic changes in channelplanform, and nodal avulsion. Tectonic control on geomorphic processesis demonstrated by the on-trend continuity of these phenomena acrossmultiple geomorphic settings. In isolation, the geomorphic criteriapresented here could be the result of independent in-channel or clima-tological controls such as sediment load, precipitation, and sea leveladjustments. However, continuity of geomorphic responses in myriadflow settings across a broad alluvial plain indicates a tectonic influence.

A

BD

E114 42’o

C

F

F’

5 km

?

5000 6000 7000 8000 9000

rs) 100x V:H

F’st

N ort hFo

rk

Mu

ndar

y

Flow direction

A Channel reach

Dune crests Clay panChannel (dashed where discontinuous)

Axis of ridge crest

Zone of aggradation

eMundary anticline. A) Annotated air photo of a portion ofMundary Creek and Gascoynepans along the base of the topographic ridge. B)GeomorphicmapofMundary Creek show-across the topographic high. C) Topographic profile F–F′ across the ridge crest and adjacent


Tectonic deformation on individual structures alters stream gradientsthat localize aggradation and incision. In some locations, aggradationsubsequently triggers stream avulsion due to channel constriction.Ongoing tectonic processes have led to repeated avulsions at the samestructurally controlled nodes (e.g., Rocky Pool and Quarry anticlines).In addition to geomorphological data, geological and geophysical dataindicate late Neogene to Quaternary active tectonic structures exist inthe region. Borehole logs and seismic data demonstrate the presenceof anticlinal structures at Rocky Pool and Brick House.

Development of the Carnarvon alluvial plain appears to be the resultof a complex interplay of fluvial responses to changing sea levels,or base levels, growth of tectonic structures, and aggradation anddegradation of channels across, through, and around folds. Riverchannel orientations are most likely controlled by the orientations offold axes, especially at lower sea levels when river base levels aremany tens to over a hundred meters lower than today. As sea levelsrise, channel aggradation occurs and avulsion events are more likely.As almost all avulsion events have occurred on the north sides of theriver channels and the river channels are progressively taking a morewestward to northwestward direction, the entire river system may beattempting to reestablish northwest-oriented flow (the old floodwaysystem) and connect to the Lake MacLeod depocenter.

5.4. Regional neotectonic significance

A system of neotectonic folds exists in the Cape region northwestof the Carnarvon alluvial plain (cf. Clark et al., 2012). Reactivation ofstructures preferentially oriented to a recently established neotectonicstress regime (e.g., Cathro and Karner, 2006) is occurring in the Cape

Gascoyne River

G’

G

A 5 km

45

35

25

10000

G

Distance (meter

Ele

vatio

n (m

eter

s)

C

QuarryChan

nel

BoodaliaCha

nnel

E113 57’o

S24

51’

o

Fig. 13. Annotated aerial photograph, geomorphic sketch map, and topographic profiles alonGascoyne River showing the location of topographic profile G–G′ across the topographic higGascoyne, Boodalia, and Quarry channels discussed in text. C) Topographic profile G–G′ across

region. This study documents the lateral continuation of this neotectonicdeformation in the Western Australia shear zone (WASZ). Within thisbelt of deformation, structures to the southeast are less topographicallydeveloped than structures to the northwest, indicating a decreasingstrain gradient across this zone (McPherson et al., 2013). The patternof folding above reactivated bedrock structures in the Carnarvon alluvialplain is consistent with Quaternary tectonic deformation in the broaderWASZ.

Geomorphological observations suggest fold growth along thestructural trend in the region is occurring per the segment linkagemodel for fault growth of Segall and Pollard (1980). In this model,structural growth is step-like. An array of en echelon or alignedfold segments link through time along strike as individual segmentslengthen and connect (Fig. 17). An en echelon series of normal faultsegments strike approximately north–south along the easternmargin ofthe southern Carnarvon basin (Hocking et al., 1985a,1985b; Crostella,1995). Fault segments within this system are reactivated with anoblique-reverse (transpressional) sense of motion (Keep et al., 2012).As the reactivated segments grow, the segments lengthen and connect.The younger folds of the Carnarvon alluvial plain plot in stage I ofFig. 17 and are isolated, whereas the Minilya folds plot in stage II asoverlapping structures, and the Cape region structures plot in stage IIIillustrating through-going segment linkage.

The observation that tectonomorphogenic structures have greatertopographic expression in the Cape region (northwest) comparedwith structures that cross the Carnarvon alluvial plain (southeast)means: i) reactivation commenced earlier in the northwest comparedwith structures to the southeast; ii) rates of neotectonic deformationare higher in the northwest than in the southeast; or iii), both.

Quarry Channel

BoodaliaChann

el

AChannel reach Dune crests

Channel

Axis of ridge crest5 km

Gascoyne River

Clay pan

B

ABC

D

AB

CD

E

20000

G’

s) 150x V:H

Topographic high

G’

G

Quarry

E113 57’o

S24

51’

o

g the Quarry anticline. A) Annotated air photo of a portion of the Quarry anticline andh. B) Geomorphic map of Quarry anticline showing a number of stream reaches on thethe topographic high and adjacent slopes.

E114 10’oTO

C

Lyndon River

H

H’

TOC

CCCC

Lynd

on River

40

60

50

15000 30000

H H’


Ele

vatio

n (m

eter

s) Lyndon River anticline

45000

Minilya folds

MF1

MF1

MF2

MF2

Lyndon Anticline

LyndonR

iver

AChannel reach

Dune crests

Clay pan

Channel (dashed where discontinuous)

Axis of ridge crest

5 km

E114 10’o

Midchannel fan

AB

C

Midchannel fan (older) TerraceLimestone

A B

C

B

Lyndon Anticline

H’

H

5 km

Lynd on

Rive

r

Marilla fault

E

Fig. 14.Annotated aerial photograph, geomorphic sketchmap, and topographic profiles along the Lyndon anticline. A) Annotated air photo of a portion of Lyndon River showing the locationof topographic profile H–H′ across the topographic high. B) Geomorphic map of Lyndon anticline showing the three stream reaches (A–C) discussed in text. C) Topographic profile H–H′across the anticline and adjacent slopes.


5.5. Uncertainties

Allen (1972a) alternatively considered that the geomorphology ofRock Pool could be related to exhumation of an older structure. However,he favored a recent tectonic genesis rather than exhumation for a numberof reasons, including folding of alluvium, similarities in discontinuousalluvium suggesting displacement, and river downcutting through thestructure despite the general raising of river base level since the last

A

B D

C E

Tect

onic

rat

e

Fluvial rat

ponding

diversion (supercedence)

aggradation and braidingacross fold a

ud

uplift

uplift

uplift

uplift

uplift

Fig. 15.Block diagrams illustrating channel responses to streamgradient adjustments as a functito relative tectonic uplift rate (on the y-axis) and fluvial rate (on the x-axis): (A) stream is pondand braids along uplift axis; (D) stream widens and aggrades upstream of uplift axis; (E) stredownstream of uplift; (F) stream maintains course and incises through uplift, uplifted terraces

glacial period. This relatively high base level is unlikely to coincide withincision and downcutting at Rocky Pool. Most importantly, tens ofmeters of sediment have accumulated through fluvial aggradation onthe Carnarvon alluvial plain. The thickness of sediments increases fromeast to west, indicating activity on the Rocky Pool anticline initiatedprior to alluvial deposition on the lower reaches of the Gascoyne Riverand aggradation is continuing under the current fluvial and tectonicenvironments.

Ge

F

aggradation and braidingupstream of fold

ggradation and braidingpstream and aggradation ownstream of fold

antecedenceand terraceformation

antecedence

uplift

uplift

on of localized tectonic uplift andfluvial energy. Block diagrams are illustratedwith respected upstream of the fold; (B) stream is diverted around fold; (C) streamwidens, aggrades,am aggrades upstream of uplift, narrows and incises across uplift, fans-out, and aggradesare formed; and (G) stream retains its channel characteristics unaltered by uplift.

Phase III Phase IV Phase I

Channel 1Channel 2

Pha

se II

Phase I

Agg

rada

tion

Deg

rada

tion

time

Autogenic or Allogenic event

Primary channelswitch

Fig. 16. Diagrams showing avulsion chronology. Gray horizontal bars indicate when eachchannel is active. Phase IV begins at the time in which channel 1 is no longer the dominantchannel although it might be reoccupied during subsequent high flows.


Hocking et al. (1987) tentatively correlated the Brown and Boodaliasystems to Pleistocene sea level high stands (240 and 125 ka,respectively), but the features have not been directly dated. Research onthe evolution of Lake MacLeod (Logan, 1987) indicated that considerablenearshore dune and beach development occurred between the GascoyneRiver and Lake MacLeod during the Holocene. Therefore, the Brown andBoodalia systems may prove to be younger than currently thought.This study identifies neotectonic structures and suggests a relative ageframework; future work should focus on developing a numericalchronology.

6. Conclusions

This paper presents examples of fluvial geomorphological responsesto neotectonic activity on the Carnarvon alluvial plain in west-centralWestern Australia. The response of streams to tectonic deformation isdemonstrated by channel deflections, recurrent channel avulsions atstructurally controlled nodes, as well as changes in channel form andgradient within structurally controlled reaches. The geomorphologicalcharacteristics are consistent with the observations of Pearce et al.(2004), where channel aggradation and degradation are the dominantchannel response to growing folds.

Rates of tectonic deformation on individual structures in the regionare low (e.g., b0.5 mm/y) although the rate of deformation across theextended margin is several millimeters per year (Hengesh et al., 2011;Whitney and Hengesh, 2013). In addition, rates of climatically drivenlandscape denudation within this arid land setting also are low. Thisresults in the condition where slow rates of tectonic deformation aregeomorphically preserved in the landscape as subtle folds that alterstream gradients and affect fluvial architecture at the channel scale.

Fluvial response to individual tectonic structures also helps tocharacterize the overall style of deformation occurring along the formerrifted continental margin. Variations of stream response in a number ofdifferent ephemeral drainages indicate variable rates of deformationand timing for onset of deformationof individual structures. Antecedentriver channel patterns change across fold axes, at times avulsingupstream of the folds. Where rates of uplift slightly outpace fluvialresponse, streams are unable to maintain their course and are deflected

(I)

(III)

(II)

A B

Fig. 17. Fold growth by segment linkage model: (A) map view and (B) profile view.(I) isolated folds; (II) overlapping folds; (III) through-going fold linkage redrawn fromCartwright et al., 1995, Fig. 4.

around the growing nose of folds. In numerous locations sheetwashflow is dammed and ponded upstream of fold axes. Variability of foldlimb dissection along strike indicates progressive deformation andalong strike growth of structures. Progressive deformation of olderunderlying stratigraphy coupled with fluvial-geomorphic indicatorssuggests ongoing tectonic activity. A tendency for neotectonic faults tobe blind and expressed as shallow folding in the Carnarvon basincould be related to the youthful nature of the WASZ and indicative ofan early stage of fault growth through segment linkage per Segall andPollard's (1980) model.

Previous studies of the Carnarvon basin have been extensive. Theyhave focused on hydrocarbons, mineral exploration, and groundwaterresources and have documented the structural setting of old basin riftstructures, including the anticline at Rocky Pool. In the course of ourwork, a considerable volume of geologic and geophysical informationcollected to support these earlier investigations in the region has beenexamined. Each of these disciplines offers a perspective and data thatcollectively provide amore complete picture of the regional neotectonicsetting. This study strives to illuminate the regional significance ofneotectonics in shaping the landscape in areas considered StableContinental Regions (SCRs) (Johnston, 1994). Reverse reactivation ofMesozoic rift structures in the region has been recognized for decades,but prior to this study no investigation into the relation betweenneotectonic deformation and fluvial response has been conducted.This provides a promising approach for recognizing other neotectonicstructures in arid Western Australia where stratigraphic evidence ofrecent deformation is lacking, but where fluvial geomorphology mayprovide a window into these processes.

Acknowledgments

We gratefully acknowledge the generous financial support providedby the ChevronAustralia Business Unit (Project PDEP AES 12-P1ABU-82)for activities related to this project and the genuine interest and supportfor this research shown by Dr. Dan Gillam. We thank Dr. Karl-HeinzWyrwoll for introducing us to Rocky Pool. We thank Dr. StephenWhite and the Geological Survey of Western Australia who providedaccess to their aerial photograph collection. We thank Martha Whitney,two anonymous reviewers, and Dr. Richard Marston for thorough andthoughtful reviews of drafts of this manuscript. All of the reviews helpedto improve this manuscript.

This work forms part of the activities of the Centre for OffshoreFoundation Systems (COFS), currently supported as a node of theAustralian Research Council Centre of Excellence for GeotechnicalEngineering and as a Centre of Excellence by the Lloyd's RegisterFoundation. The Lloyd's Register Foundation invests in science,engineering, and technology for public benefit, worldwide. The leadauthor is the recipient of a SIRF scholarship from The University ofWestern Australia.

References

AGSO North West Shelf Study Group, 1994. Deep reflections on the North West Shelf:changing perceptions of basin formation. In: Purcell, P.G., Purcell, R.R. (Eds.), TheNorth West Shelf. Australia, Proceedings of the Petroleum Exploration Society ofAustralia Symposium, Perth, pp. 63–76.

Allen, J.R.L., 1965. A review of the origin and characteristics of recent alluvial sediments.Sedimentology 5, 89–191.

Allen, A., 1972a. Groundwater resources along the lower Gascoyne River—a summary.Western Australia Geological Survey Annual Report 1972,pp. 23–25.

Allen, A., 1972b. Cretaceous-Holocene stratigraphy and structure, lower Gascoyne River,Carnarvon Basin.Western Australia Geological Survey Annual Report 1972,pp. 17–22.

Audley-Charles, M.G., 2004. Ocean trench blocked and obliterated by Banda forearc collisionwith Australian proximal continental slope. Tectonophysics 389, 65–79.

Audley-Charles, M.G., 2011. Tectonic post-collision processes in Timor. Geol. Soc. Lond.,Spec. Publ. 355, 241–266.

Bagha, N., Arian, M., Ghorashi, M., Pourkermani, M., El Hamdouni, R., Solgi, A., 2014.Evaluation of relative tectonic activity in the Tehran basin, central Alborz, northernIran. Geomorphology 213, 66–87.

http://refhub.elsevier.com/S0169-555X(14)00522-4/rf0350

















Baxter, J.L., 1966. General geology of the Rocky Pool dam site. Western Australia GeologicalSurvey Annual Report 1965, pp. 29–30.

Baxter, J.L., 1967a. Hydrogeological features of the Gascoyne River west of the KennedyRange. Geol. Surv. W. Aust. 9, 24.

Baxter, J.L., 1967b. The geology of the Rocky Pool dam site. Geol. Surv. W. Aust. 16, 16.Baxter, J.L., 1967c. Hydrogeological features of the Gascoyne River, west of the Kennedy

Range. Western Australia Geological Survey Annual Report 1965, pp. 44–45.Baxter, J.L., 1968. Hydrogeology of the Gascoyne River. Geol. Surv. W. Aust. 7, 18.Boutakoff, N., 1963. Geology of the offshore areas of north-western Australia. J. Aust. Petrol.

Explor. Assoc. 3, 10–18.Brice, J.C., 1964. Channel patterns and terraces of the Loup Rivers in Nebraska. Geol. Surv.

Prof. Pap. 442-D, 41.Bull, L., Kirkby, M., 2002. Dryland river characteristics and concepts. In: Bull, L.J., Kirby, M.J.

(Eds.), Dryland Rivers: Hydrology and Geomorphology of Semi-arid Channels. Wileyand Sons, Ltd, West Sussex, pp. 3–15.

Cartwright, J.A., Trudgill, B.D., Mansfield, C.S., 1995. Fault growth by segment linkage: anexplanation for scatter in maximum displacement and trace length data from theCanyonlands Graben of SE Utah. J. Struct. Geol. 17, 1319–1326.

Cathro, D.L., Karner, G.D., 2006. Cretaceous-Cenozoic inversion history of the DampierSub-basin, northwest Australia: Insights from quantitative basin modeling. Mar. Pet.Geol. 23, 503–526.

Clarke, E., de, C., 1938. Middle and west Australia regionale geologie der erde (Andree,Brouwer u. Bucher), (Die alten Kerne), (Abschnitt VII 1:62).

Clark, D., 2004. Reconnaissance of Recent Fault Scarps in the Mt Narryer Region. GeoscienceAustralia unpublished report, Western Australia (31 pp.).

Clark, D., McPherson, A., Van Dissen, R., 2012. Long-term behaviour of Australian stablecontinental region (SCR) faults. Tectonophysics 566–567, 1–30.

Condon, M.A., Johnstone, D., Perry, W.J., 1955. The Cape Range structure WesternAustralia. Commonwealth of Australia. Department of National Development, Bureauof Mineral Resources, Geology and GeophysicsBulletin 107.

Condon, M.A., Johnstone, D., Prichard, C.E., Johnstone, M.H., 1956. The Giralia and Marrillaanticlines north west division Western Australia. Bur. Miner. Resour. Geol. Geophys.25, 96.

Crone, A.J., Machette, M.N., Bowman, J.R., 1997. Episodic nature of earthquake activity instable continental regions revealed by palaeoseismicity studies of Australian andNorth American Quaternary faults. Aust. J. Earth Sci. 44, 203–214.

Crostella, A., 1995. Structural evolution and hydrocarbon potential of the Merlinleigh andByro sub-basins, Carnarvon Basin. Geol. Surv. W. Aust. 45, 41.

Denman, P.D., van de Graaff, W.J.E., 1977. Emergent Quaternary marine deposits in theLake MacLeod area, WA. Western Australia Geological Survey Annual Report 1976,pp. 32–37.

Densley, M.R., Hillis, R.R., Redfearn, J.E.P., 2000. Quantification of uplift in the CarnarvonBasin based on internal velocities. Aust. J. Earth Sci. 47, 111–122.

Dodson, W.J., 2009. Groundwater recharge from the Gascoyne River, Western Australia.Department of Water, Report No HG. 32, p. 240.

El Hamdouni, R., Irigaray, C., Fernández, T., Chacón, J., Keller, E., 2008. Assessment of rel-ative active tectonics, southwest border of the Sierra Nevada (southern Spain). Geo-morphology 96, 150–173.

Fisk, H.N., 1952. Geological investigation of the Atchafalaya Basin and the problem of theMississippi River diversion. Waterways Experiment Station, Vicksburg, Mississippi,p. 145.

Friend, P.F., Sinha, R., 1997. Braiding and meandering parameters. In: Best, J.L., Bristow,C.S. (Eds.), Braided Rivers 75. Geological Society Special Publication, pp. 105–111.

Gordon, F.R., 1964. Kennedy Range dam site, Gascoyne River. A preliminary appraisal.Geological Survey of Western Australia, Record 1964. 24, p. 20.

Guccione, M.J., Burford, M.F., Kendall, J.D., 1999. Pemiscot Bayo, a large distributary of theMississippi River and a possible failed avulsion. In: Smith, N.D., Rogers, J. (Eds.), FluvialSedimentology VI. Special Publication of the International Association of Sedimentolo-gists 28. Blackwell, Oxford, pp. 211–220.

Hancock, P.M., 1969a. Regional geologic implications, Rocky Pool dam site investigation,Carnarvon Basin. Geological Survey of Western Australia, Annual Report for theyear 1968, pp. 42–45.

Hancock, P.M., 1969a. Geological investigations at Rocky Pool dam site, Gascoyne River:Western Australia Geological Survey, Survey, Record 1968/12, 4 pp. (unpublished).

Hengesh, J.V., Wyrwoll, K.H., Whitney, B.B., 2011. Neotectonic deformation of northwest-ern Australia and implications for oil and gas development. In: Gourvenec, S., White,D. (Eds.), Proc. 2nd International Symposium on Frontiers in Offshore Geotechnics.Taylor and Francis, Perth, Western Australia, pp. 203–208.

Hillis, R.R., Reynolds, S.D., 2000. The Australian Stress Map. J. Geol. Soc. 157, 915–921.Hillis, R.R., Reynolds, S.D., 2003. In situ stress field of Australia. In: Hillis, R.R., Muller, R.D.

(Eds.), Evolution and Dynamics of the Australian Plate, 49–58 372. Geological Societyof Australia Special Publication 22 and Geological Society of America Special Paper,pp. 49–58.

Hillis, R.R., Sandiford, M., Reynolds, S.D., Quigley, M.C., 2008. Present-day stresses, seis-micity and Neogene-to-Recent tectonics of Australia's ‘passive’ margins: intraplatedeformation controlled by plate boundary forces. In: Johnson, H., Doré, A.G., Gatliff,R.W., Holdsworth, R., Lundin, E.R., Ritchie, J.D. (Eds.), The Nature and Origin of Com-pression in Passive Margins 306. Geological Society of London Special Publication,pp. 71–90.

Hocking, R.M., 1988. Regional geology of the northern Carnarvon Basin. In: Purcell, P.G.,Purcell, R.R. (Eds.), Proceedings of the North West Shelf symposium, 10–12 August1988. Perth. Petroleum Exploration Society of Australia, Perth, pp. 97–114.

Hocking, R.M., 1990. Field guide for the Carnarvon Basin. Geol. Surv. W. Aust. 11, 82.Hocking, R. M., Williams, S. J., Lavering, I. H., Moore, P. S., 1985a. Winning Pool-Minilya, W.A.

Geological Survey ofWestern Australia, 1:250 000. Geological Series Explanatory Notes,pp. 11

Hocking, R. M., Williams, S. J., Moore, P. S., Denman, P. D., Lavering, I. H., van de Graaff, W.J. E., 1985b. Kennedy Range, W.A. Geological Survey of Western Australia, 1:250 000.Geological Series Explanatory Notes, pp. 31.

Hocking, R.M., Moors, H.T., van de Graaff, W.J.E., 1987. Geology of the Carnarvon Basin.Bull. Geol. Surv. W. Aust. 133.

Holbrook, J., Schumm, S.A., 1999. Geomorphic and sedimentary response of rivers totectonic deformation: a brief review and critique of a tool for recognizing subtleepeirogenic deformation in modern and ancient landscapes. Tectonophysics 305,287–306.

Iasky, R.P., Mory, A.J., 1999. Geology and petroleum potential of the Gascoyne platformsouthern Carnarvon basin Western Australia. Geol. Surv. W. Aust. 69, 51.

Johnston, A.C., 1994. Seismotectonic interpretations and conclusions from the stablecontinental region seismicity database. In: Johnston, A.C., Coppersmith, K.J., Kanter,L.R., Cornell, C.A. (Eds.), Assessment of Large Earthquake Potential, Electric PowerResearch Institute. vol. 1.

Kaiko, A.R., Tait, A.M., 2001. Post-rift tectonic subsidence and palaeo-water depths in thenorthern Carnarvon Basin, Western Australia. J. Aust. Petrol. Explor. Assoc. 41,367–379.

Keep, M., Harrowfield, M., Crowe, W., 2007. The Neogene tectonic history of the NorthWest Shelf, Australia. Explor. Geophys. 38, 151–174.

Keep, M., Hengesh, J., Whitney, B., 2012. Natural seismicity and tectonic geomorphologyreveal regional transpressive strain in northwestern Australia. Aust. J. Earth Sci. 59,341–354.

Kendrick, G.W., Wyrwoll, K.-H., Szabo, B.J., 1991. Pliocene-Pleistocene coastal events andhistory along the western margin of Australia. Quat. Sci. Rev. 10, 419–439.

King, R.C., Neubauer, M., Hillis, R.R., Reynolds, S., 2010. Variation of vertical stress in theCarnarvon Basin, NW Shelf, Australia. Tectonophysics 482, 73–81.

Leopold, L.B., Wolman, M.G., 1957. River channel patterns braided, meandering, andstraight. U. S. Geol. Surv. Prof. Pap. 282-B, 85.

Logan, B.W., 1987. The MacLeod evaporate basin, Western Australia. AAPG Mem. 44, 140.Logan, B.W., Read, J.F., Davies, G.R., 1970. History of carbonate sedimentation, Quaternary

Epoch, Shark Bay, Western Australia. AAPG Mem. 13, 38–84.Makaske, B., 2001. Anastomosing rivers: a review of their classification, origin and

sedimentary products. Earth-Sci. Rev. 53, 149–196.McPherson, A., Clark, D., Whitney, B., 2013. Neotectonic evidence for a crustal strain

gradient on the central-west Western Australian margin. Western Australia BasinSymposium, Perth, Australia (16 pp).

McWhae, J.R.H., Playford, P.E., Lindner, A.W., Glenister, B.F., Balme, B.E., 1956. Thestratigraphy of Western Australia. J. Geol. Soc. Aust. 4, 1–153.

Müller, R.D., Dyksterhuis, S., Rey, P., 2012. Australian paleo-stress fields and tectonicreactivation over the past 100 Ma. Aust. J. Earth Sci. 59, 13–28.

Nanson, G., Knighton, A., 1996. Anabranching rivers: their cause, character and classification.Earth Surf. Process. Landf. 21, 217–239.

Nanson, G., Tooth, S., Knighton, D., 2002. A global perspective on dryland rivers: perceptions,misconceptions and distinctions. In: Bull, L.J., Kirby, M.J. (Eds.), Dryland Rivers:Hydrology and Geomorphology of Semi-arid Channels. Wiley and Sons, Ltd, WestSussex, pp. 17–54.

Ouchi, S., 1985. Response of alluvial rivers to slow active tectonic movement. Geol. Soc.Am. Bull. 96, 504–515.

Özkaymak, C., Sözbilir, H., 2012. Tectonic geomorphology of the Spildağı High Ranges,western Anatolia. Geomorphology 173–174, 128–140.

Passmore, J.R., 1968. Lower Gascoyne River: Possible flow losses downstream fromKennedy Range Dam site. Geol. Surv. W. Aust. 11, 39.

Pearce, S.A., Pazzaglia, F.J., Eppes, M.C., 2004. Ephemeral stream response to growingfolds. Geol. Soc. Am. Bull. 116, 1223–1239.

Petrovski, J., Timár, G., 2010. Channel sinuosity of the Körös River system, Hungary/Romania,as possible indicator of neotectonic activity. Geomorphology 122, 223–230.

Playford, P.E., Johnstone, M.H., 1959. Oil exploration in Australia. Bull. Am. Assoc. Pet.Geol. 43, 397–433.

Raggatt, H.G., 1936. Geology of the north-west basin, Western Australia, with particularreference to the stratigraphy of the Permo-Carboniferous. Roy. Soc. NSW 100–174.

Raitt, J., Turpie., A., 1965. Southern Carnarvon Basin seismic survey (Traverse D. PelicanHill bore). Bull. Geol. Surv. W. Aust. 40, 23.

Raynor, J.M., Condon, M.A., 1964. Summary of data and results, Carnarvon Basin, WesternAustralia, Exmouth Gulf marine seismic survey Whaleback seismic survey. 49. WestAustralian Petroleum Pty. Publication, p. 23.

Revets, S.A., Keep, M., Kennett, B.L.N., 2009. NWAustralian intraplate seismicity and stressregime. J. Geophys. Res. 114. http://dx.doi.org/10.1029/2008JB006152.

Schumm, S.A., Dumont, J.F., Holbrook, J.M., 2000. Active Tectonics and Alluvial Rivers.Cambridge University Press, Cambridge (276 pp.).

Segall, P., Pollard, D.D., 1980. Mechanics of discontinuous faults. J. Geophys. Res. 85,4337–4350.

Slingerland, R., Smith, N.D., 2004. River avulsions and their deposits. Annual Review EarthPlanetary Science. 32, pp. 257–285. http://dx.doi.org/10.1146/annurev.earth.32.101802.120201.

Sykes, L.R., 1978. Intraplate seismicity, reactivation of preexisting zones of weakness,alkaline magmatism, and other tectonism postdating continental fragmentation.Rev. Geophys. Space Phys. 16, 621–688.

Teichert, C., 1948. Younger tectonics and erosion in Western Australia. Geol. Mag. 85,243–246.

Timár, G., 2003. Controls on channel sinuosity changes: a case study of the Tisza River, theGreat Hungarian Plain. Quat. Sci. Rev. 22, 2199–2207.

Timár, G., Sümegi, P., Horváth, F., 2005. Late Quaternary dynamics of the Tisza River:evidence of climatic and tectonic controls. Tectonophysics 410, 97–110.

Veeh, H.H., Schwebel, D., van de Graaff, W.J.E., Denman, P.D., 1979. Uranium-series ages ofcoralline terrace deposits in Western Australia. J. Geol. Soc. Aust. 26, 285–292.

















































































































































http://dx.doi.org/10.1029/2008JB006152





http://dx.doi.org/10.1146/annurev.earth.32.101802.120201

http://dx.doi.org/10.1146/annurev.earth.32.101802.120201













Whitney, B.B., Hengesh, J.V., 2013. Geological constraints on Mmax values from WesternAustralia: implications for seismic hazard assessments. Aust. Geomech. J. 48, 15–26.

Willemin, J.H., Knuepfer, P.L.K., 1994. Kinematics of arc-continent collision in the easternCentral Range of Taiwan inferred from geomorphic analysis. J. Geophys. Res. 99,20267–20280.

Wyatt, J.D., 1967. Geological investigations of the Kennedy Range dam site. Geol. Surv. W.Aust. 14, 34.

Wyrwoll, K.-H., Stoneman, T., Elliott, G., Sandercock, P., 2000. Geoecological setting of theCarnarvon Basin, Western Australia: geology, geomorphology and soils of selectedsites. Records of the Western Australian Museum Supplement. 61, pp. 29–75.

Zámolyi, A., Székely, B., Draganits, E., Timár, G., 2010. Neotectonic control on river sinuosityat the western margin of the Little Hungarian Plain. Geomorphology 122, 231–243.













Geomorphological evidence of neotectonic deformation in the … · 2017-02-14 · Fluvial...

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