Geomorphology 208 (2014) 200–206

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Geomorphology

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A reinterpretation of geomorphological evidence for Glacial Lake Victoria,McMurdo Dry Valleys, Antarctica

Hamish A. McGowan a,⁎, David T. Neil b, Johanna C. Speirs a,c

a Climate Research Group, School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane 4072, Australiab School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane 4072, Australiac Snowy Hydro Ltd., Sydney, New South Wales, Australia

⁎ Corresponding author. Tel.: +61 7 33566651.E-mail address: h.mcgowan@uq.edu.au (H.A. McGowa

0169-555X/$ – see front matter © 2013 Elsevier B.V. All rhttp://dx.doi.org/10.1016/j.geomorph.2013.12.005

a b s t r a c t

a r t i c l e i n f o

Article history:Received 13 September 2013Received in revised form 30 November 2013Accepted 7 December 2013Available online 14 December 2013

Keywords:Victoria ValleyAntarcticShorelinesMass movementLiDARGlacier

The largely snow and ice free McMurdo Dry Valleys of Antarctica are one of the coldest and driest locations onEarth. It has been proposed that during the Last Glacial Maximum (LGM) to the early Holocene large lakes upto 200 m deep and 100 km2 in area occupied these valleys. We present the first topographic survey of featuresreported to be shorelines from one such lake, Glacial Lake Victoria, in Victoria Valley. In combination with theanalysis of laser altimetry data obtained from the NASA Airborne Topographic Mapper system and cosmogenicdating of granite boulders we show that the features previously thought to be shorelines are not horizontallyor linearly continuous. Rather, we conclude that they are scars from ancient slope mass movement deposits.10Be cosmogenic dating indicates that their formation is on timescales of at least 160 ka before present andnot 20 ka as the LGM mega-lake hypothesis suggests. We conclude that the geomorphic features believed tobe shorelines andwhich underpin the LGMmega-lake hypothesis in Victoria Valley aremassmovement depositsand not lake shorelines. Our results support an emerging body of literature unable to find evidence to verify theMcMurdo Dry Valleys LGM mega-lake hypothesis. Accordingly we suggest caution in invoking such significantlandscape features in discussions of the environmental past of this unique region until such time as further re-search provides an unequivocal history of the region's geomorphic past.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

The McMurdo Dry Valleys (MDVs) are the largest snow and ice freeregion on the Antarctic continent, and are thought to have been thisway formost of the past 13.6 Ma (Sugden andDenton, 2004). They con-sist of three large northeast–southwest trending valleys (Victoria,Wright and Taylor Valleys) which collectively cover an area of approxi-mately 4800 km2 considered to be tectonically stable (Sugden andDenton, 2004). With annual precipitation b50 mm water equivalent(Fountain et al., 2010) and mean annual air temperatures between−14.8 °C and −30 °C (Doran et al., 2002), the MDVs are a truehyper-arid polar desert. Victoria Valley is characterised by an internaldrainage systemwhich channels seasonalmeltwaters to its topographiclow point, the 5.7 km2 Lake Vida, which occupies a glacially excavatedtrough near the mid-point in the valley system.

Hall et al. (2002) presented evidence for a palaeo mega-lake Vida,which they called Glacial Lake Victoria. They concluded that the mega-lake covered approximately 100 km2 and was at least 200 m deep,based on their visual assessment of surficial sedimentary deposits, in-cluding features they interpreted as perched deltas and shorelines. Ac-celerator Mass Spectrometry (AMS) radiocarbon dates of 87 samples

n).

ights reserved.

of algal mats were used to infer an age for Glacial Lake Victoria of atleast 20,000 yrs to 8600 yrs 14C yr B.P. (Hall et al., 2002). During thistime the lake would have been more than 1000 km from the nearestopen water (Hall et al., 2010).

A key geomorphic feature identified by Hall et al. (2002) and used toinfer the depth and, therefore, the spatial extent of Glacial Lake Victoria,was the linear features on thewall of the eastern section of Victoria Val-ley. They interpreted these features as relict shorelines and stated, “Aprominent shoreline occurs in eastern Victoria Valley on the south val-ley wall opposite Packard Glacier. Here, a flat, horizontal, laterally con-tinuous (4 km) bench occurs at 525 m elevation.” (Hall et al., 2002,pp. 701–702). In a series of papers Hall et al. presented evidence ofdeltas and elevated shorelines above the floors of the adjacent Wrightand Taylor Valleys (Hall et al., 2001, 2010), south of Victoria Valley,and proposed that theMDVswerefilled by large lakes from the Last Gla-cial Maximum to early Holocene.

Bockheim et al. (2008) analysed 190 pedons from sites above andbelow the palaeo-lake levels proposed by Hendy (2000) and Hall et al.(2001) for the Wright and Taylor Valleys. They found no evidence ofthe influence of the proposed high-water-level lakes in soil develop-ment and/or soil salinity. Neither did they find evidence of former lakesediments or high-level strandlines (except on the north valley wall ap-proximately 50 m above Lake Vanda in Wright Valley), ice shove fea-tures, or possible palaeo-shorelines (Bockheim et al., 2008) during

201H.A. McGowan et al. / Geomorphology 208 (2014) 200–206

geomorphic mapping of the soils of the MDVs, thereby challenging theexistence of the palaeo mega-lakes.

Hall et al. (2001) hypothesised that generation of the immense vol-umes of meltwater needed to fill the mega-lakes during the Last GlacialMaximum (LGM) occurred by increased exposure of glacial blue ice atthis time due to reduced snowfall resulting in increased absorption ofsolar radiation due to the lower albedo of blue ice. This was thought tohave occurred under themore prevalent snow free and clear sky condi-tions of the LGM,when analyses of an ice core record fromnearbyTaylorDome suggest that annual temperatures were up to 8 °C colder thanpresent (Steig et al., 2000).

Analysis of supra-glacial melt on Wright Lower Glacier MDVs byMacDonell and Fitzsimons (2012) demonstrated that total ablation ondebris-covered ice is nine times greater than for clean ice. Hoffmanet al. (2008) concluded that subsurface melt on Taylor Glacier MDVs isonly common where debris melts into the ice forming cryoconiteholes, thereby lowering the surface albedo and increasing the absorp-tion of solar radiation below the surrounding glacier surface. The pres-ence or absence of debris on glaciers in the MDVs may also be theprincipal control on meltwater generation during foehn winds (Aylingand McGowan, 2006; Speirs et al., 2010), when daytime air tempera-tures can rise to several degrees Celsius above zero, particularly duringsummer (Speirs et al., 2010), generating large volumes of meltwateras occurred in 2001/02 and 2008/09 (Barrett et al., 2008; Doran et al.,2008). Hydrometeorological data from the MDVs therefore show thatmeltwater generation is primarily controlled by glacier albedo with‘dirty’ ice producing much larger volumes of meltwater than clean andblue ice. Summers with a high frequency of warm foehn winds for ex-tended periods are responsible for the generation of the largest volumesof meltwater under the current climate. However, melt only accountsfor about 9% to 30% of total glacier ablation in the MDVs with sublima-tion accounting for the remaining 70% or more (Hoffman et al., 2008).

The existence of large glacial lakes in theMDVs from the LGM to theearly Holocene is far from certain and more research is required to re-solve their existence unequivocally. Here we present a reinterpretationof the geomorphic evidence for the palaeo-shorelines in the easternVictoria Valley opposite Packard Glacier used by Hall et al. (2002) toinfer the depth and spatial extent of Glacial Lake Victoria. A field topo-graphic survey of the site was conducted in November 2004 followedby analysis of LiDAR data available for the eastern Victoria Valley. Thisresearch was conducted as part of an ongoing programme of researchof the climogeomorphic history of the valley.

2. Physical setting

The Victoria Valley is the northernmost and largest of the threeMDVs, bordered to the north by the St John's Range and to the southby the Olympus and Asgard Ranges, which separate the Victoria fromthe adjacent Wright Valley (Fig. 1). The seaward eastern outlet ofVictoria Valley is blocked by Victoria Lower Glacier and Wilson Pied-mont Glacier, a small ice cap fed by coastal snowfall, which extendsalong the Scott Coast in a north–south direction for approximately60 km.

Approximately 2.5 kmwest of Victoria Lower Glacier is the PackardSand Dunes, the largest dune field in the Antarctic, which cover an areaof ~1.5 km2 in a belt which is about 3.1 km long. From the Trans-Antarctic Mountains in the west, four main valleys converge on LakeVida. The most northern of these is the upper Victoria Valley in whichlies Victoria Upper Glacier with the termini of Victoria Upper andLower Glaciers approximately 26 km apart. In the summer, meltwaterfrom both glaciers drains into Lake Vida in the centre of the Victoria Val-ley system. The remaining valleys are the Barwick, Balham andMcKelvey Valleys (Fig. 1).

Lake Vida occupies the lowest point in the valley. The valley floor is acomplex mosaic of peri and para-glacial features including glacial er-ratics, moraines, sand sheets, seasonal melt-stream channels and sand

dunes (Speirs et al., 2008; Bourke et al., 2009). Average mean annualair temperature at Lake Vida is −27.4 °C, with average summer (NDJ)and winter (MJJ) temperatures of −4.6 °C and −40.7 °C, respectively(Speirs et al., 2008). Mean annual precipitation is b50 mmwater equiv-alent. Thewind regime of Victoria Valley is alternately dominated by ei-ther topographically channelled, thermotopographic easterly windsduring summer or west to southwesterly foehn winds which mayoccur throughout the year and result in air temperature increases ofN40 °C in only a few hours (Speirs et al., 2010). Katabatic drainagewinds are light and mostly confined to individual slopes or glaciersandflow toward the valley floor, where they contribute to the formationof stable cold air pools in which air temperatures may fall to b−60 °Cduring winter at Lake Vida.

3. Methods

In November 2004 a topographic survey was undertaken of the lin-ear features discussed by Hall et al. (2002). A total station theodolitewas installed on the floor of Victoria Valley opposite the features de-scribed as shorelines by Hall et al. (2002) and their positions were sur-veyed under the direction of the operator of the total station. Thesurveys were undertaken both along and across (downslope) the in-ferred shorelines.

High-resolution airborne LiDAR topography data collected in 2001using the NASA Airborne Topographic Mapper (ATM) laser altimetrysystemwas obtained for Victoria Valley. These data have absolute accu-racy of 0.05 ± 0.5 m (Csatho et al., 2003). The data were processed inArcGIS and high resolution three dimensional digital elevation models(DEMs) of the slope opposite Packard Glacier on which the inferredshorelines are located were developed.

Six rock samples of 2 to 3 kg each were collected from boulders in asequence of recessional moraines of the Packard drift at the base of thesurveyed slope (Bockheim andMcLeod, 2013), and from glacial erraticson the inferredpalaeo-shorelines of Hall et al. (2002). Sampleswere col-lected off boulders at heights 1 to 1.7 m above the surrounding groundsurface. Analyses of the samples for 10Be exposure ageswere carried outat the ANTARES facility of the Australian Nuclear Science and Technolo-gy Organisation in Sydney, Australia (Fink and Smith, 2007).

4. Results

Topographic transects surveyed along the inferred palaeo-shorelines of Hall et al. (2002) are shown with a photograph of theslope onwhich they are located in Fig. 2. Results of the topographic sur-vey show that the bench-like features are inclined laterally downslopeon both their eastern and western margins with gradients rangingfrom 1:9 to 1:100. By comparison these gradients are, for example,one to two orders of magnitude greater than the lateral shorelineslope reported for former high stands of North American glacial Lake Al-gonquin of 1:1000 (Harrison, 1972), while Fabel et al. (2010) presenteddigital elevation models for the ‘Parallel Roads’ glacial lake shorelines ofGlen Roy, Scotland highlighting their essentially horizontal form. Shore-lines formed by high stands of Northeast Lake on Mount Lowry in thePatuxent Range, Pensacola Mountains, Antarctica are horizontal and in-tersect obliquelywith lateralmoraines (Hodgson and Bentley, 2013). Bycontrast, our topographic and field survey confirms for the first timethat the bench like features believed to be former shorelines of GlacialLake Victoria are not horizontal, are not associated with dykes or sillsand other geologic structures that could form shoreline type features,have slopes varying by an order of magnitude and are not linearlycontinuous.

To gain further insight into the geomorphic history of the slope andits bench-like features a digital elevation model (DEM) was createdfrom the high-resolution airborne LiDAR topography data. The DEM(Fig. 3) shows that the bench-like features are located within a largescallop we identify as a mass movement scar. A steep rear scarp rises

Fieldsite

78°00

77°00

Fig. 1. Location of the Victoria Valley, Antarctica, showing the site of the bench-like features in the eastern Victoria Valley.

202 H.A. McGowan et al. / Geomorphology 208 (2014) 200–206

above the uppermost bench, while debris from the mass movementevent has been removed from the toe of the slope, possibly by VictoriaLower Glacier during past advance/retreat sequences. The DEM indi-cates that the bench like features closely resemble heavily weatheredheads of at least two slope failures, probably induced by the removalof the toe slope by glacial action with the base of the slope now adjoin-ing a series of recessional moraines.

Exposure ages (10Be) for rock samples collected from granite boul-ders on the Packard drift moraines and the benches on the slope arepresented in Fig. 4 and Table 1. Results show a sequential decrease inage of the three samples from the moraines of the Packard drift upvalley (eastwards) toward the terminus of Victoria Lower Glacier aswould be expected with retreat of the glacier. Exposure ages were163 ± 11.2 ka, 112 ± 8.4 ka and 63 ± 4.4 ka in a west to east (glacialretreat) direction. The dates from granite glacial erratics located onand adjacent to the bench-like features interpreted by Hall et al.(2002) as shorelines give ages of 316.1 ± 23.2 ka (655 masl) and293.8 ± 21.9 ka (641 masl), while the date obtained from a graniteboulder at 514 masl (≈110 m above the valley floor) was 138.5 ±9.8 ka. We acknowledge the significant limitations of such cosmogenicdating including uncertainty of reset times and shielding effects by themountain slope on which the granite boulders are located, as well as

the limited number of dates presented here. However, the consistentage sequences in the two data sets (moraine and valley sidewall) andthe similar patterns of valley shading for the two datasets providesome confidence in the age determinations. The dates we have obtainedprovide a chronological sequence consistent with a gradual up-valley(eastward) decrease in age of moraines (recession of Victoria LowerGlacier) and an upslope increase of age of glacial erratics.

The dates from the glacial erratics GLE_1 at 655 masl and GLE_2 at641 masl of 316.1 ± 23.2 ka and 293.8 ± 21.9 ka respectively areinterpreted as being associated with the Vida drift of Victoria Valleyand corresponding Taylor III drift of Taylor Valley in southern VictoriaLand (Brook et al., 1993; Bockheim and McLoed, 2013). Oberholzeret al. (2003) presented cosmogenic dates from glacial erratics in theDeep Freeze Range, northern Victoria Land coeval with these glacial ad-vances indicating a regional glacial event in theRoss Sea area duringMIS8. Importantly, the dates we present for the glacial erratics of316.1 ± 23.2 ka; 293.8 ± 21.9 ka and 138.5 ± 9.8 ka indicate thatthe bench-like features on which they rest were not formed duringMa-rine isotope stages (MIS) 2 and 3 when Glacial Lake Victoria is believedto have existed by Hall et al. (2002). Formation of the shorelines and as-sociated overturning of sediments including the glacial erratics wouldhave likely resulted in resetting of the surface exposure ages of the

174176178180182184186188190

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(m)

Horizontal Distance (m)

186187188189190191192193194

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(m)

Horizontal Distance (m)

114

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126

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134

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(m)

Horizontal Distance (m)

126

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136

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pla

cem

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(m)

Horizontal Distance (m)

5 x 02EV x VE

30x VE

20x VE

0 20 40 60 80 100 120 0 20 40 60 80 100 120 140 160

0 40 80 120 160 2000 100 200 300 400 500 600

Fig. 2. Photograph of the bench-like features believed by Hall et al. (2002) to be shorelines with topographic survey profiles of along feature transects shown. Vertical exaggerations (VE)are indicated.

203H.A. McGowan et al. / Geomorphology 208 (2014) 200–206

boulders we sampled to ages corresponding more closely with MIS 2and MIS 3.

5. Discussion

The existence of a large glacial lake in Victoria Valley from the LGMto early Holocene was first postulated by Hall et al. (2002) and Kelly

Fig. 3.Digital elevationmodel (DEM) of the slope onwhich the bench-like features are lo-cated in the eastern Victoria Valley with the boundary of the slope failure zone indicatedby the red dashed line. The yellow arrows highlight the features believed by Hall et al.(2002) to be shorelines caused by Glacial Lake Victoria whichwe interpret here as a seriesof heavily weathered heads of rotational slope failures. The black arrows indicate reces-sionalmoraines of the Packard drift. Similar recessionalmoraines are located on the oppo-site side of the valley and are discussed by Atkins and Dickinson (2007).

et al. (2002). Hall et al. (2002) proposed that Glacial Lake Victoria hada depth of up to 200 m and surface area of approximately 100 km2.The postulated attributes were based on field observations of bench-like features at an elevation of approximately 525 m on the mountainslope opposite the Packard sand dunes in the eastern section ofVictoria Valley. The reference datum used to determine the elevationof these features was not given but is assumed here to have beenmean sea level. The age control for this mega-lake was interpolatedfrom the AMS radiocarbon dating of algal mats collected from sedi-ments in Victoria Valley. These gave spatially disordered dates of be-tween ca. 20,000 to 8600 yrs 14C yrs B.P. Recently, a series of studiesof soils in theMDVs has challenged themega-lake hypothesis includingthe existence of Glacial Lake Victoria in Victoria Valley (Bockheim et al.,2008; Bockheim and McLeod, 2013). These studies have found no evi-dence of the effect of large bodies of water on soil properties of theMDVs including those in Victoria Valley.

Hall et al. (2002) hypothesised that the huge volumes of meltwaterrequired to fill the mega-lakes of the MDVs during the LGM originatedfrom the accelerated melt of blue ice areas that were more expansiveduring the LGM due to reduced snowfall. This hypothesis was basedon the work of Hendy (2000) who proposed that increased exposureof blue ice during the LGMwould result in a decrease in surface albedo.Field observations support this with the albedo of blue ice ranging from0.56 to 0.69 compared to 0.8 to 0.85 for snow (Bintanja, 1999). The cor-responding increase in absorption of solar radiation by blue ice was be-lieved by Hendy (2000) to cause sufficient ice melt, even under thecolder LGM climate to generate the immense volume of water to createGlacial Lake Victoria.

Measurements of Antarctic blue ice temperatures confirm that theyare typically warmer than surrounding snow covered ice. However, the

400m

1000m

525m

GLE_1 316.1 ± 23.2ka (655 m)GLE_2 293.8 ± 21.9 ka (641 m)

GLE_3 138.5 ± 9.8ka (515 m)

RM_2 112.0 ± 8.4ka (396 m)RM_1 63.0 ± 4.4 ka (396 m) RM_3 163.2 ± 11.2 ka (400m)

Fig. 4. Photograph showing approximate location of rock samples collected for 10Be dating and their corresponding dates.

204 H.A. McGowan et al. / Geomorphology 208 (2014) 200–206

majority of ablation from blue ice is via sublimation (Bintanja, 1999;Favier et al., 2011). Meltwater generation is not significant and onlycommon from dirty ice and/or during warm temperature anomalieswhen ambient air temperature rises above 0 °C. This can occur underthe current climate during the advection of warm maritime air massesonto the Antarctic continent by cyclonic storms or during foehn windswhen significant meltwater generation occurs in the MDVs includingVictoria Valley (Fig. 5) (Welch et al., 2003; Doran et al., 2008; Favieret al., 2011; Speirs et al., 2012). However, ice core data from TaylorDome adjacent to the MDVs indicates that temperatures were likely tohave been up to 8 °C colder than present during the LGM when GlacialLake Victoria is thought to have existed (Steig et al., 2000). Significantmeltwater generation at this time is therefore unlikely to have occurredduring such extreme cold.

Our topographic survey of the bench-like feature inferred by Hallet al. (2002) to be a former shoreline confirms for the first time that itis one of several such features that are not horizontal or linearly contin-uous and vary markedly in slope (Figs. 2 to 4). Analysis of LiDAR datashows that they closely resemble at least two relict scars likely to havebeen created by rotational slides, with the boundary of the slope failureclearly distinguishable on the DEM of the mountain slope (Fig. 3). Re-sults from the 10Be dating of granite glacial erratics sitting on and adja-cent to the scars confirm that these features predate MIS 2 and 3 whichis when theywould have been formed if caused by Glacial Lake Victoria.Similarly, ages for granite boulders on moraines of the valley floor areconsistent with glacial advance/retreat on a 160 ka timescale ratherthan a possible glacio-lacustrine ice rafting origin on a 20 ka timescale

Table 1Details of locations where granite rock samples were collected, sample sizes used for 10Bedating, and corresponding minimum 10Be ages with associated uncertainties.

SampleID

Location(DatumWGS 84)

Elevation(m) abovesea level

Samplesize (g)

10Be(atomsg−1) 106

10Be error(atomsg−1) 106

Minimum10Be exposureage (ka)

RM_1 S77 22.633E16215.880

396 59 0.651 0.021 63 ± 4.4

RM_2 S77 22.910E16211.907

396 70.3 1.144 0.046 112 ± 8.4

RM_3 S77 22.976E16211.375

400 63.6 1.647 0.042 163.2 ± 11.2

GLE_1 S77 23.041E16215.999

655 56 3.083 0.094 316 ± 23.2

GLE_2 S77 23.190E16214.088

641 60.8 2.881 0.097 293.8 ± 21.9

GLE_3 S77 23.097E16212.964

515 64.4 1.406 0.045 138 ± 9.8

as suggested byHall et al. (2002). Accordingly, based on the geomorphicevidence presented with 10Be dates, we conclude that the featureswhich were used by Hall et al. (2002) to infer the depth of GlacialLake Victoria and its spatial extent are not shorelines.

It is important to highlight that we are not questioning the extensiveradiocarbon dating of algal mats or mapping of the delta like depositsidentified by Hall et al. (2002). However, these alone should not betaken as evidence of a former Glacial Lake Victoria. During field workfor this study we observed at numerous sites extensive algal bloomsin meltwater streams, deposition of algal mats over sediments on thefalling limbs of meltwater streams and, the formation of deltas anddelta-like sedimentary structures caused by glacio-fluvial and niveo-aeolian processes (Fig. 6). These deposits can, for example, form alongice marginal areas of polythermal glaciers in association with lateralmeltwater channels, potentially leaving downslope evidence of a chro-nological sequence of deposits as ice retreats and ablates. Atkins andDickinson (2007) investigated ice marginal melt channels below thePackard Glacier in the eastern section of Victoria Valley in the vicinityof where Hall et al. (2002) obtained nine AMS 14C dates ranging from8.9 to 13.8 kyr for algal laminae believed to be from deltaic sediments.They concluded that the algal samples dated by Hall et al. (2002) andtheir disordered nature were more likely from multiple deposits ofmeltwater channels of Packard Glacier rather than from deltas formedalong the edge of a Glacial Lake Victoria.

6. Conclusion

TheMDVs are a hyper-arid polar desert where under the present cli-mate numerous small lakes such as Lake Vida remain frozen, some totheir base and freeze completely solid in winter, while during summerinflows of meltwater may create a ‘moat’ around their edges and/oran unfrozen lens of water on their surface. Based on a visual analysisof bench-like features on the valley wall in the eastern Victoria Valleybelieved to bepalaeo-shorelines, delta like sedimentary deposits and ra-diocarbon dates, Hall et al. (2002) proposed that Lake Vida was greatlyexpanded during the LGM to a depth of 200 m and covering more than100 km2. Analysis of topographic survey and LiDAR data of the featuresbelieved to be shorelines by Hall et al. (2002) has shown these aremorelikely scarps left by at least two rotational slumps, that is, they are a re-sult of sub-aerial hillslope/mass movement processes rather thanglacio-lacustrine processes. Cosmogenic dating of samples from graniteboulders sitting on the scarps and moraines at the toe of the slope indi-cates that they significantly predate MIS 2 and 3 and are not thereforepalaeo-shorelines formed by a Glacial Lake Victoria during the LGM.

Our results support an increasing body of literature (i.e. Atkins andDickinson, 2007; Bockheim et al., 2008; Konfirst et al., 2011; Bockheimand McLeod, 2013; Toner et al., 2013) questioning the existence oflarge glacial lakes in theMDVs during theMIS 2 and 3. Furthermore, ob-servational studies of the surface energy balance over Antarctic snow

Fig. 5. Photograph showing extensive melt-water streams in the eastern Victoria Valley during a foehn wind event (3 December 2004).

205H.A. McGowan et al. / Geomorphology 208 (2014) 200–206

and ice including blue ice clearly demonstrate that a mechanism re-quired to generate the huge volumes of meltwater to produce suchlakes is also highly equivocal, especially under a climate regime muchcolder than present.We therefore conclude that the key geomorphic ev-idence presented by Hall et al. (2002) to define the depth and very con-siderable spatial extent Glacial Lake Victoria owes its origin to massmovement processes operating on a c. 300 ka timescale and notglacio-lacustrine processes operating on a c. 20 ka timescale. Combinedwith other published research from Victoria Valley we cannot find evi-dence of a large mega-Lake Vida (Glacial Lake Victoria), and suggestcaution in invoking such a significant landscape feature in discussingthe palaeo-environment of this unique region until further researchprovides an unequivocal geomorphological history of the MDVs.

Acknowledgements

The authors thank John Orwin for his assistance in the field; GerdDowideit for his analysis of the LiDAR and topographic survey data,and David Fink and the Australian Nuclear Science and Technology Or-ganisation (ANSTO) for expert assistance and the financial support forthe 10Be dating of rock samples via project AINGRA06121. Financial

((a)

Fig. 6. Photographs of (a) an algae bloom in the eastern VictoriaValley (4December 2004) and ((8 December 2004).

support for field research in Victoria Valley was provided by theAustralian Antarctic Division and logistical support was supplied byAntarctica New Zealand. We also thank the School of Geography, Plan-ning and Environmental Management at the University of Queensland,Australia for their continued support of our research. The constructivereviews of our manuscript byWarren Dickinson and an anonymous re-viewer are greatly appreciated.

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