Submarine geomorphology and sea ﬂoor processes along …Shaded multibeam bathymetry map of the study area (2m cell size grid, UTM Zone 43S projection). Hillshade illumination in

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Submarine geomorphology and sea floor processes along thecoast of Vestfold Hills, East Antarctica, from multibeam

bathymetry and video dataPHILIP E. O’BRIEN1, JODIE SMITH2, JONATHAN S. STARK3, GLENN JOHNSTONE3, MARTIN RIDDLE3 and

DENNIS FRANKLIN4

1Department of Environment and Geography, Macquaire University, 31/5 Burbury Close, Barton, ACT 2600, Australia2Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia

3Australian Antarctic Division, Channel Highway, Kingston, TAS 7050, Australia4Indago Partners, Melbourne, VIC, Australia

[email protected]

Abstract:A survey of nearshore areas in the Vestfold Hills, Antarctica, using high-resolution multibeamswath bathymetry provided both a detailed digital bathymetric model and information on sedimentacoustic backscatter. Combined with underwater video transects and sediment sampling, these data wereused to identify and map geomorphic units. Six geomorphic units identified in the survey region include:rocky outcrops, basins, pediments, valleys, scarps and embayments. In addition to geomorphic units, thedata revealed sedimentary features that provide insights into post-glacial sediment transport and erosionin the area. Ice keel pits and scours are common, and sea floor channels, scour depressions and sandribbons indicate transport and deposition by wind-driven currents and oceanographic circulation.Gullies and sediment lobes observed on steep slopes indicate mass movement of sediment. Some of theseprocesses have not been directly observed to date, but their effectiveness in shaping the modern sea flooris clearly indicated by the sea floor mapping data. The embayments preserve a mantle of boulder sandprobably deposited by cold-based glaciers which were flanked by faster-flowing ice in adjoining regions.

Received 20 November 2014, accepted 15 June 2015

Key words: marine processes, marine sediments, sea bed geomorphology, sea bed video, swathbathymetry

Introduction

The ice-free areas along the Antarctic coastline representonly 0.3% of the continent but are key habitat areas forbirds and mammals, having rich marine faunas andsupporting Antarctica’s terrestrial vegetation (Beyer &Bölter 2002). They are also important for understandingthe geological history of the Antarctic because theyprovide a wide range of sedimentary deposits andlandforms which record environmental change(Mackintosh et al. 2014). On the Antarctic continentalmargin, most multibeam bathymetry and sampling datahave been collected from the continental shelf in order tounderstand the past behaviour of major outlet glacierswhich cut large cross-shelf troughs (Ó Cofaigh 2015). Tofully reconstruct the glaciation of the Antarctic margin,there is still a need to understand the behaviour and extentof glaciers between the major ice streams where thecoastal oases lie. At present, there are data from theonshore parts of coastal Antarctica, but there is very littleavailable for the nearshore zone. In addition, these areasare the main locations for human activity with moststations situated within them. Therefore, understanding

the physical environments of coastal ice-free areas and theprocesses shaping them is important for scientific reasons,for management of human activities and for monitoringfuture change in the Antarctic environment.

Onshore areas benefit from digital elevation models,satellite imagery and aerial photography to provide anintegrated physical framework for understanding theirenvironments (Tarolli 2014), but few marine areas ofcoastal oases have equivalent datasets. The basicdata requirement for marine areas is high-resolution,continuous bathymetry which is best obtained bymultibeam echo sounders. In addition to bathymetricdata, these echo sounders record acoustic reflectancemeasurements (backscatter) providing insight into seafloor characteristics (Lucieer et al. 2013). These dataprovide the necessary framework to integrate other pointdata types, such as underwater video, still imagery and seabed sampling to better understand the marine environment(Shaw et al. 2014). In this paper, we present the results ofthe 2009/2010 summer field campaign in the coastal watersof the Vestfold Hills. This paper will concentrate on themultibeam bathymetry, backscatter and video imagery,and sediment sampling results, with detailed analysis of

Antarctic Science page 1 of 21 (2015) © Antarctic Science Ltd 2015 doi:10.1017/S0954102015000371

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Fig. 1. Location of the Vestfold Hills, East Antarctica (inset). Shaded multibeam bathymetry map of the study area (2 m cell sizegrid, UTM Zone 43S projection). Hillshade illumination in this and subsequent figures is from the north-west (azimuth= 315°,altitude= 45°) unless otherwise stated. Location of underwater video transects and sediment samples acquired during the 2010survey and historical sediment samples.

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the biological sampling to appear elsewhere. Thedifferent datasets will be used to develop a geomorphicclassification of the area. This classification aims toimprove understanding of the origin of the landforms, theprocesses that modify them and how these processes affectthe modern sea floor environment. The geomorphicclassification can also help to refine sampling strategiesfor future studies of benthic habitats.

Study area

The study area, the Vestfold Hills, is one of the largestareas of ice-free coast in East Antarctica. They cover anarea of 400 km2 and lie between 68°21'S and 68°41'S, and77°49'E and 78°35'E. The coastline comprises small rockyislands, peninsulas and fjords (Fig. 1). Islands and hills onthe mainland reach elevations of up to 60 m in the coastalzone rising to 156m inland near the edge of the ice sheet.The Vestfold Hills are an Archean basement blocksurrounded by younger Precambrian metamorphic rocksto the north and south, and the Phanerozoic Prydz BayBasin to the west (Stagg 1985, Collerson & Sheraton 1986).The eastern extent of the Vestfold Hills block is unknownbecause it is obscured by the ice sheet. This block forms anelevated plateau surrounded by deep troughs to the southand west, and probably deeper but more gently slopingbedrock to the north and east, though information onsubice topography in these areas is limited.

The Cenozoic geology and geomorphology of theVestfold Hills have been extensively studied (Pickard1982, Adamson & Pickard 1986a, 1986b, Fitzsimmons1991, 1996, Gore et al. 2003, Quilty 2006). The overallpicture is one of east–west to WSW–ENE trendingvalleys, floored with sediments and containing lakes.The area was overridden by ice advancing from the south-east during recent glaciations (Adamson & Pickard1986a). Pliocene marine sediments are preserved atMarine Plain (Quilty et al. 2000) and glacial depositsranging from possible Pliocene age to late Pleistocene arepresent (Colhoun et al. 2010), though a detailedunderstanding of the area’s glacial history has yet toemerge. Holocene post-glacial raised beaches and lakedeposits have been used to reconstruct a Holocene sealevel curve post 8000 yr BP for the region (Peterson et al.1988, Zwartz et al. 1998).

The climate is cold-polar with a mean maximumtemperature of -7.4°C and a mean minimumtemperature of -13°C (Bureau of Meteorology 2013).Snowfall is low with a mean annual precipitation of70.5 mm water equivalent. The wind regime is dominatedby strong flow from the north-east throughout the year,with occasional gentler sea breezes from the south-west insummer. The north-easterly winds blow from 067° (T)and dominate surface processes on land with ventifacts,wind scours, lee dunes, blizzard tails and snow banks all

indicating NE–SWwind flow as the main surface-shapingagent (Pickard 1982). Mean wind speeds vary from17 km hr-1 to 26 km hr-1, though maximum gusts of206 km hr-1 have been recorded (Bureau of Meteorology2013). Sea ice is present for most of the year. Freezingtakes place intermittently from late February and break-out typically takes place in December. Break-out occursprogressively from south to north in response toprevailing winds from the north-east and the geometryof the coast. Vaz & Lennon (1996) described marine watermasses and currents in the area. The Vestfold Hills coast isbathed by a water mass that has potential temperaturesbetween -1.8°C and +2.1°C and salinities of 30.6–34.2 psu,and that flows from north to south with average velocitiesin the order of 0.015m s-1. The tidal range is c. 1–2m butvelocities measured offshore from the study area were< 0.01m s-1. Primary productivity is high during spring andsummer from both sea ice and open water phytoplankton,dropping to low during winter (Tucker 1988).

Methods

A geomorphic map of the study area was published byO’Brien et al. (2012) that used hand-digitizing polygonsbased on visual inspection of a preliminary bathymetrygrid. Here, final processed bathymetry and backscatterdata are used. Automatic definition of geomorphic polygonboundaries was attempted to find more rigorous andreproducible polygon boundaries. This paper also includesdescriptions of areas north and south of the Davis Stationwhere limited multibeam swath data was collected (Fig. 1).Data coverage in these areas is insufficient to allowmapping of closed geomorphic polygons but is sufficientto provide additional insights into sedimentary processes inthese areas.

Multibeam bathymetry and backscatter data

Multibeam bathymetric data were collected byGeoscience Australia from February to March 2010using the Australian Antarctic Division workboatHoward Burton equipped with a Kongsberg EM 3002D300 kHz dual head multibeam sonar system. Motionreferencing and navigation data were collected using anApplanix Position and Orientation system (PosMV 320),coupled with a C-Nav Differential Global PositioningSystem (2050R), providing positional accuracy of± 0.2 m. An area of 42 km2 was surveyed with coverageof the swaths between 150 and 200% in the shallow watersclosest to Davis Station (Fig. 1). Additional survey lineswere run to Long Fjord in the north and to CrookedFjord and the Sørsdal Glacier in the south.

The data were processed using Caris HIPS/SIPS v7.1software. Initial processing of the multibeam data toaccount for tides and vessel motion (pitch, roll and

SEA FLOOR GEOMORPHOLOGY, VESTFOLD HILLS 3



Fig. 2. High-resolution backscatter map of the study area (2 m cell size grid, UTM Zone 43S projection). Location of Figs 4–9 and13–17 are shown as inset boxes (indicated by corresponding figure number). Location of cross-section in Fig. 18 is shown as blackline (west–east).




heave), and to remove erroneous values and icebergs wascompleted during the survey. Final processing after thesurvey removed more complex artefacts and convertedthe data to mean sea level (MSL). Interpolatedbathymetry surfaces were exported as a 2 m resolutiongrid for mapping purposes into ESRI ArcGIS 10.0(Fig. 1). Bathymetric data are presented as plan andoblique shaded-relief images to differentiate the major seafloor landforms. Cross sections were taken through keysea floor features to show their dimensions.

In addition to the bathymetric data, backscatter datawere recorded by the multibeam sonar system. They were

processed using CMST-GA MB Process v.8.11.02.1, amultibeam backscatter toolbox co-developed byGeoscience Australia and Centre for Marine Scienceand Technology (CMST), Curtin University forTechnology. Backscatter intensity values were calculatedfollowing correction for transmission loss and area andremoval of angular dependence (see Lucieer et al. 2013 forfurther details). The final backscatter data were exportedas a 2 m resolution grid. The data were colour coded andthe resulting image is shown in Fig. 2.

The processed multibeam sonar bathymetric andbackscatter data are published as data products and

Fig. 3. Map of submarine geomorphic units.




false-colour images. All of these data productsare available for download from the GeoscienceAustralia website (http://www.ga.gov.au/metadata-gateway/metadata/record/gcat_76729).

Six geomorphic units were identified and mappedwithin the central study area (Fig. 3). Mapping wasundertaken in ArcGIS v10.0 (ESRI) using a combinationof automatic extraction and manual digitization ofpolygons (see Finkl & Makowski 2015). Automaticextraction of geomorphic units was completed usingthe Spatial Analyst toolbox in ArcGIS. The multibeamdatasets include a large number of small-scaleirregularities (a function of the high-resolution data)which tend to dominate derived attributes, makingpolygons overly complex. As the purpose of themapping was to create a broad-scale map, lowerresolution grids were created in order to remove some ofthe finer detail, thereby allowing smoother polygons tobe created. The 2m bathymetry and backscatter gridswere reduced to 10m resolution and a slope grid derivedfrom the bathymetry grid. Depth, backscatter and slopecontours were derived from at 1 m, 1 dB and 1° spacing,respectively. Raster Calculator was used to define cellsaccording to the parameters outlined in Table I. Thegeomorphic units were then converted to polygons. Theoutput from this automated process resulted in alarge number of complex polygons (Supplemental Fig. 1found at http://dx.doi.org/10.1017/S0954102015000371),including several undefined areas. The automated processhighlighted some geomorphic features well (e.g. basins);however, other areas, particularly the rocky outcrops,were less well defined. The automatically extractedpolygons were modified by hand to produce the finalpolygons to ensure that the final polygons reflectedthe surface morphology and seascape setting. Thebasins were smoothed first, mostly using the 3° slopeor -21 dB backscatter contours. Rocky outcropswere smoothed next using the spacing of the slopecontour (rather than a consistent slope contour)to define the change in slope, as well as the bedrockappearance of the sea bed in the bathymetry grid.The resulting interpreted geomorphic map (Fig. 3)contains simplified polygons that are morphologicallycoherent.

Underwater video

Underwater video data was used to ground-truth thegeomorphic units and provide detail of sea floor features.Sixteen underwater video transects were surveyed in thestudy area using Geoscience Australia’s shallow-waterRaytech towed-video system (Fig. 1). Full details of thecollection and characterization of underwater videoincluding the biota is published in Smith et al. (2015).The sea bed was characterized using the scheme ofAnderson et al. (2008) to record substrate composition(rock, boulder, cobble, pebble, sand, mud), bedforms(ripples, hummocks, iceberg scour features) and relief(smooth < 1 m, moderate 1–3 m, high > 3 m). The videowas evaluated for 10 m segments, with a 10 m intervalbetween each segment. All observations were entered into aMicrosoft Excel spreadsheet via a programmablekeyboard. The latitude and longitude of each observationwas extracted from the workboat positioning data using theUTC time stamp overlay on the imagery.

The locations of the 643 discrete video observationswere plotted in ArcGIS 10.0. Depth, backscatter intensityand slope values, as well as geomorphic unit, wereextracted for each observation from the 10 m grids andcombined with substrate, relief and bedform variablesfrom the video characterization. A multivariateordination technique was used to identify the majorsources of variation in the data. Principal componentanalysis (PCA) was carried out using CANOCO v5.03software (Ter Braak & Šmilauer 2012) using depth,backscatter, slope, relief (flat, low 0.1–1 m, moderate1–3m, high > 3 m), substrate (rock, boulder, cobble,pebble, gravel, sand, mud) and bedforms (ripples,hummocky, iceberg scour feature) as variables.

Sediment sampling

The sediment samples used come from a variety ofstudies. During the 2010 field season, 31 sediment sampleswere collected across the study area. Twenty-eightsediment samples were collected by divers from shallow-water sites close to Davis Station using a push corer (5 cmdiameter). The top 5 cm of sediment was removed fromthe cores for analysis. The cores were kept upright and

Table I. Datasets and parameters used to map the geomorphic features.

Feature Datasets used (automated; manual) Depth Backscatter Slope

Basin Bathymetry, backscatter, slope grids; 1° and 1 dB contours -10 to -70 m < -21 dB < 3°Valley Bathymetry, backscatter, slope grids; 1° contours < -70 m < -21 dB < 7°Embayment Bathymetry, slope grids; 1 m contours < -7 m < 2°Pediment Backscatter, slope grids; 1° contours -11 to -21 dB; > -11 dB < 5°; < 2°Rocky outcrop Bathymetry, backscatter, slope grids; 1° contours < -5 m > -11 dB > 2°Scarp Slope grid; 1° contours > 10°


http://www.ga.gov.au/metadata-gateway/metadata/record/gcat_76729

http://www.ga.gov.au/metadata-gateway/metadata/record/gcat_76729

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frozen at -20°C. A further three samples were collectedfrom the workboat at deeper sites using a mini-shipekgrab with a 30 cm wide mouth.

The sediment samples were analysed to determine thegravel, sand and mud content by washing sediment througha 2mm sieve. The <2mm fraction was also analysed forlaser particle size using aMastersizer 2000 Particle Analyzer.Homogenized sub-samples were analysed for organicmatter(% OM) by loss on ignition following the procedure of Heiriet al. (2001). Carbonate content was determined using the

carbonate ‘bomb’ gas evolution method (Muller & Gastner1971), and biogenic silica was determined using the methodof Mortlock & Froelich (1989).

The sediment dataset was augmented by 37 sitescollected from the study area in 1995. Of these records,several were recorded as no sample (primarily due to hardsubstrate) or small sample size, with 23 samplescontaining sufficient sample for grain-size analysis.Grain-size analysis of these samples was conducted bysieving samples into gravel, sand and mud fractions.

Fig. 4a. Enlarged shaded bathymetry image of a bedrock outcrop south of Barratt Island. b. Cross-section of outcrop showing thelocation of north–south trending dykes. c. Photograph of dolerite dykes (in black) running for several tens of kilometres across theexposed bedrock in the adjacent Vestfold Hills.




Fig. 5a. Shaded bathymetry image of the inner basin east of Gardner Island showing elongated and broad scour depressions alongthe eastern margin. b. Enlarged shaded image showing iceberg pits and furrows. c. Enlarged shaded bathymetry image of a broadscour depression on the south-western margin of Anchorage Island. d. Enlarged shaded backscatter image of the broad scourdepression showing coarser sediments in the depression compared to the surrounding muddy basin. e. Cross-section of the innerbasin from Krat Rocks to O’Gorman Rocks, showing the relatively flat basin floor dissected by small iceberg pits and scours.f. Cross-section across the scour depression showing the steep slope separating the depression from the surrounding sea floor andbackscatter intensity values for the depression and adjacent areas.




Biogenic silica and carbonate content data was alsoavailable for 20 of these samples. Data on gravel-sand-mud content of onshore deposits collected by sieveanalysis are available in a number of published papers(Hirvas et al. 1993, Gore et al. 2003, Colhoun et al. 2010)and an unpublished soil survey by Makarucha (1984).The locations of all sediment samples used in this studyare shown in Fig. 1.

Geomorphic mapping

The multibeam bathymetry and backscatter data revealthe complexity and heterogeneity of the sea floor in theVestfold Hills nearshore marine environment that has notbeen previously apparent (Figs 1 & 2). The inshore watersalong the Vestfold Hills coast are very shallow (< 10 m)increasing to c. 60 m within 5 km of the Davis Station

coastline and to even deeper waters further offshore. Atthe mouths of Long and Crooked fjords, water depthsincrease rapidly to > 200 m.

The blue tones in Fig. 2 represent low backscatterintensities and coincide with the distribution ofacoustically non-reflective mud. Red tones indicate areasof high backscatter intensity, largely encompassing areasof exposed bedrock and large boulders. Yellow tonesrepresent areas of intermediate backscatter intensity andare typically characterized by sandy sediment.

Six geomorphic features were identified and mappedfrom the multibeam datasets (Fig. 3).

Rocky outcrop

Bedrock outcrops form rounded hills and knolls with smalland medium scale roughness. They vary from 50m to 2 km

Fig. 6a. Enlarged shaded bathymetry image of the pediment between Gardner Island and the inner basin. b. Enlarged shadedbackscatter image of the same area showing the transition from hard (red) substrate to soft (blue) substrate. c. Cross-sectionshowing the flat pediment surface and backscatter intensity values for the bedrock outcrop, pediment and basin.




across (e.g. in the north-west of the main study area).Multibeam images show geological features common tometamorphic terranes. For example, joint planes and faultsare visible, as are dolerite dykes which form linear, roundedridges standing slightly higher than the surroundinggneisses (Fig. 4a, b & c). Many bedrock outcrops havehigh backscatter (> -11 dB); however, some areas, wherebedrock features are clearly displayed present lowbackscatter intensities indicating a thin sediment veneer.

Basins

Basins are located between islands and bedrock outcrops,and are flat to slightly undulating and, as indicated bymostly low backscatter intensities (< 21 dB), covered withsediment (Fig. 5a). Three main basins were identified in thestudy area, including two shallow basins (typically < 35m)to the east and north-east of Gardner Island, and a deeper(> 35m) basin to the west of Gardner Island (Fig. 3). Abasin in the northern part of the survey area near PloughIsland was also partly mapped. Video transects andsediment samples in the basins indicate that they aretypically flooredwith olive grey to greenmuddy fine sand tosandy mud. Ice keel scours are abundant (Fig. 5b & e).

Pediments

Between bedrock outcrops and sediment-flooreddepressions are broad areas that are flat to gently slopingwhich we classify as pediments based on their resemblanceto pediments seen in many arid areas (Fig. 6a & b). Thedefinition of pediment varies widely but is most commonly

used for ‘gently sloping erosional surfaces of low relief,developed on bedrock’ (Dohrenwend & Parsons 2009).While the absence of sub-bottom profiler data means thatwe cannot confirm that the surfaces are cut on shallowbedrock, the morphology and location between or adjacentto bedrock hills are similar to many described pediments(Fig. 6a & c). Slopes are lower than the sides of rocky hillsand the surfaces may undulate, possibly reflectingunderlying near-surface bedrock. These surfaces mostlyslope away from bedrock hills towards basins andcommonly lack a clear step down to the basin level(Fig. 6c). Backscatter values are intermediate (typically-11 to -22 dB) which suggests sandy sediment. Icebergscours are present in some of these areas but others lackapparent scours, possibly because the sediments are toocoarse to retain well defined scour topography. Somepediment areas close to shore, e.g. north-east of AnchorageIsland, contain boulder fields (see below).

Fig. 7a. Enlarged shaded bathymetry image of the scarp alongthe eastern margin of the deep basin west of Gardner Island,showing the boundaries of the scarp and surroundinggeomorphic units. b. Cross-section of the scarp showing thesteep slope between two relatively flat surfaces (pedimentand basin).

Fig. 8a. Enlarged shaded bathymetry image of an elongatedvalley in the western part of the survey area. b. Cross-sectionof the valley showing the steep-sided valley walls.c. Longitudinal section of the valley showing the slopingvalley floor.




Fig. 9a. Enlarged shaded bathymetry image of airport beach embayment. b. Enlarged image showing the presence of large (> 4m)individual boulders on the sea floor. c. Photograph of a large boulder onshore from the embayment. d. Underwater photograph ofa large boulder inhabited by diverse benthic fauna in the shallow waters near Davis Station. e. Enlarged shaded backscatter imageof airport beach embayment showing the predominantly hard substrate and areas of sand accumulation. f. Cross-section of theembayment showing the shallow sill used to delineate the embayment unit. g. Enlarged shaded bathymetry image of sand ribbonsin airport beach embayment and a mound that is a possible pingo scar. h. Cross-section of the sand ribbons showing theirirregular width and height.




Scarps

Scarps occur in several areas where steep slopes separateareas of level topography, such as pediment and basinareas. Such scarps separate ‘airport beach’ (informal name)embayment and the basin south of Anchorage Island, andform the eastern margin of the deeper basin west ofGardner Island (Fig. 7a). Scarps are differentiated fromsides of bedrock hills because they represent distinctivesteps between relatively flat surfaces (Fig. 7b). Where theseareas adjoin bedrock hills, the boundary between the scarpand the bedrock hill slope was chosen as the steepest linedirectly downslope from the outermost edge of the bedrockhill to the basin or pediment below (Fig. 3).

Valleys

Valleys are present between some of the rocky hills,particularly in the deeper western part of the study area(Fig. 8a & b). They are differentiated from basins by beingelongated with steeper sloping floors (Fig. 8c). Manyvalleys in the area are orientation north–south followingthe trend of faults and joints in the basement. Theirsubstrate characteristics are relatively poorly knownbecause video imagery was not collected in these areas.

Embayments

Some shallow areas < 10 m deep, close to shore, areenclosed by peninsulas, islands and shallow sills thereforedrifting ice does not scour the sea floor (e.g. Fig. 9a).These areas exhibit a relatively smooth sea floor but withabundant large boulders which are clearly visible in themultibeam grids (Fig. 9b). These boulders are < 5 m indiameter and are similar to the large boulders foundimmediately onshore (Fig. 9c & d). The boundary of the

embayment north of Davis Station was placed along ashallow ridge thought to act as a sill that extends frombetween Trigwell and Flutter islands in the north to nearDavis Station in the south (Fig. 9e). The sea floorappearance and backscatter intensity was similar inother boulder field areas immediately to the west of theembayment boundary, as well as to the north of theembayment; however, the exclusion of icebergs bysurrounding relief removes an important process ofsurface reworking from the embayment areas. In airportbeach embayment, areas of sediment ripples evident inthe underwater video, and linear sediment ridges, suggestcurrent activity (Fig. 9g & h, see below).

Heidemann Bay is also enclosed, but was not mapped bymultibeam sonar because of hazardous survey conditions.

Interpretation of sediment data

Sediment samples come from a range of sea floorenvironments, including basin, pediment and enclosedembayment locations.Most samples are muddy sand withsome gravel to sandy mud (Fig. 10). Overall, gravelcontents were low (< 15%) and the only significant gravelcontents (> 5%) were found close to the shoreline andnear the channels south of Gardner Island. There was apositive correlation between mud content, organicmatter and biogenic silica (r2= 0.75 and 0.70,respectively). Basin samples contained the highestproportion of muds, especially in the basin to the

Fig. 10. Triplot of grain-size data of marine surface sedimentsfrom 1995 and 2010 surveys, and onshore sediments from1982–83 survey. Grain-size classes from Folk (1954).

Fig. 11. Principal component analysis (PCA) ordination plotshowing the relationship between the physical variables,derived from the underwater video and multibeam data, andgeomorphic units.




north-east of Gardner Island (Supplemental Fig. 2found at http://dx.doi.org/10.1017/S0954102015000371).High mud contents were also recorded in a deep basinoutside Laternula Inlet (supplementary Fig. 2). Basinsamples contained an average of 9% organic matter andbiogenic silica content of up to 22%.

Pediment sample areas were mostly muddy sands, butsandy muds, sands and gravelly sands were also present.Pediment samples contained an average of 22%mud, 74%sand and 4% gravel. Organic matter and biogenic silicacontents were lower than in the basins (2% and 5%,respectively). Overall, the carbonate content was low(average 1% in both basins and pediments); however, thesample taken adjacent to the channel features had ahigher carbonate content (6%).

Compared to grain-size data from onshore sampling, themarine samples generally have less gravel and a higherproportion of mud (Fig. 10). The onshore datasets containa significant proportion of glacial deposits; therefore, theobserved difference in grain-size distributions can beexplained by the marine samples containing sedimenttransported and deposited since deglaciation. The onshoresamples most similar to those from offshore are thoseinterpreted by Colhoun et al. (2010) as marine deposits.

Correlation between geomorphic units and sea bedcharacter

The PCA plot (Fig. 11) shows the relationship betweenphysical sea bed variables and geomorphic units. The firsttwo PCA axes cumulatively explained 41.9% of the totalvariation in the data. PCA axis 1, which alone accountedfor 24.1% of the variation, was highly correlated withdepth and longitude. PCA axis 2, which accounted for17.8% of the variation in the data, was correlated withsubstrate (i.e. backscatter, mud and rock). Slope wascorrelated with both axes. Axis 1 represents, from left toright, gradient from shallow flat sea floor close to shore,to deeper and steeper sea floor further offshore. Axis 2represents, from top to bottom, a gradient from steeprocky substrate to flat softer substrate. Coarseunconsolidated substrate (e.g. cobbles, pebbles, gravel)and iceberg scours did not display any strong trends withthe geomorphologic units, with only short vectors in thePCA plot.

The position of the observations in the ordination spaceindicates the main similarities and differences in sea floorcharacteristics between the geomorphic units. The plotshows clear separation of basin, embayment, valley androcky outcrop units. Basins had positive scores on axis 1and negative scores on axis 2, indicating that they aredeep, with muddy substrate and occur further offshore.Embayments had negative scores on axis 1 and mostlypositive scores on axis 2, indicating that these areasare shallow, flat, hard and close to shore. Boulders,

hummocky sea bed and ripples are common features inthe embayments and also plotted in this direction.Observations from rocky outcrops dispersed widely inthe PCA plot but had mostly positive scores on axis 1and 2 indicating they have hard substrate and occuracross a wide range of depths and with varying slopes.Observations from pediment areas lie in the centre of theplot, crossing both axes, and showing overlap with otherunits, indicating that they occur across a range of depths,are gently sloping and vary from hard and rocky to softand sandy. This is consistent with them covering thetransition from rocky outcrops to basins. Valleys hadpositive scores on axis 1 and mostly negative scores onaxis 2, indicating that they occur in deeper water offshore,with relatively steep slopes and soft substrates. Insummary, Fig. 11 shows a good separation between fivegeomorphic units which indicates that depth, backscatterand slope are useful for mapping geomorphic units withdistinctive surface characteristics. Embayments do notappear separately in the PCA analysis because they aredistinguished by their context in the topography ratherthan their surface character.

Deposits and sedimentary structures

A benefit of high-resolution multibeam bathymetry datais the ability to resolve sea floor sedimentary structuresand deposits, such as bedforms, that provide insights intoprocesses operating in the environment.

Iceberg scours

Iceberg scours are common across most of the areaswhere soft sediment is the main substrate. Scour shapesform a continuum from rounded sub-circular to ellipticaldepressions up to 45 m across (pits, Barrie et al. 1992;Fig. 5b) to long linear furrows as narrow as 4 m acrossand 385 m long (Fig. 5a & b). Almost all scours are < 2 mdeep with most < 1 m deep. An inventory of scour widthsand depths found no relationship between the two. Basinareas show overlapping scours at all scales. In the basinsouth of Anchorage Island, scours are orientedpredominantly north–south with an arcuate trendconvex to the east. Scours with pits at one end all havethe pit at the northern or north-western end. A few east–west oriented scours are present.

On video transects, iceberg scours are harder to detectthan might be expected given their visibility on themultibeam data. This largely reflects the subduedscour geometry. Most areas with scours visible onmultibeam data, appear in video imagery as hummockysea floor. Where visible on video, Vestfold Hillsscours have rounded berms standing < 1m above thescour bed. Angular blocks of fractured, compactedsediment observed in berms of scours off Canada


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(Woodworth-Lynas et al. 1991, Barrie et al. 1992) andGeorge V Land shelf (Post et al. 2011) are not present.

During the survey, a small iceberg travelled slowlyNE–SW across the area north of Anchorage Island.A video transect across the iceberg track revealed a freshsea floor scour with rounded berms in light-coloured,probably sandy sediment, with a few boulders protruding.Also present within the scour were ridge-and-groove‘microtopography’ (Woodworth-Lynas et al. 1991)comprising sediment ridges c. 150 mm high and up toc. 300 mm across running parallel to the scour trough andthe general direction of iceberg drift.

Channels

Narrow channels resembling drainage features cross thepediment area south of Gardner Island, running downslope normal to the prevailing current direction (Fig. 12).They have low sinuosity, are c. 30 m wide and 0.5–1 mdeep, and their margins are modified by ice keel pits andscours.

Boulder fields

The shallower areas in the east and north-east of the studyarea commonly show numerous boulders up to severalmeters in diameter standing above the sea floor orvariably embedded in the substrate (e.g. airport beachembayment, Fig. 9b & d). The sea floor between theboulders is commonly sandy, with intermediatebackscatter values. The multibeam data show irregularridges and terraces c. 1–2 m above adjacent depressions.Boulder fields are also present in Heidemann Bay and inthe shallow pediment area to the north of AnchorageIsland. These areas are a continuation of a typical feature

of the onshore south-western Vestfold Hills landscape(undulating valley fill of Gore et al. 2003, Fig. 9c).

Sand ribbons

In the south-eastern part of airport beach embayment,there is an area which features elongated ridges that are50–300 m long and 5–30 m wide (Fig. 9a & g). Most trendtowards 246° (T) though the most northerly pair of ridgestrend 256° (T). The main group of 11 ridges varies inorientation by only a few degrees. The ridges are0.2–0.5 m high at their highest (Fig. 9h). Theirappearance suggests that they are sediment bodiesoverlying the boulder surfaces discussed above. This isreinforced by video transects which show them tocomprise rippled sand, hence their designation as sandribbons. Ripple orientations suggest sand transportroughly parallel to the ridges.

Mound with central depression

Within airport beach embayment is a single mound 50 min diameter and 0.5 m high with a depression in thecrest (Fig. 9a & g). Backscatter values are higherthan adjacent sediments but similar to other parts of theembayment floored by boulder-rich sand. Two sandribbons seem to have formed in the lee of the mound.The mound geometry is unlike bedrock outcropsprotruding through the sediment cover in the embayment.

Scour depressions

Depressions occur in several places along the shallow(10–25m) margins of the basins, immediately seaward ofshallow rocky outcrops (Fig. 5a). Elongated depressionstrend parallel to adjacent bedrock outcrops (e.g. depressionnext to O’Gorman Rocks, Fig. 5a) and broad depressionstrend roughly perpendicular to the adjacent rocky outcrops.The elongated depressions are typically 0.5–1.0m below thesurrounding sediment, range from < 30m wide and< 250m in length and are often steep-sided.

Two larger depressions are found south-west ofAnchorage Island (Fig. 5c & d) and west of TorcklerRocks (Fig. 5a), in water depths of 20–25m and extendingc. 250m from the adjacent rocky outcrop (Fig. 5a). Thesebroad depressions are characterized by coarser grainedsediment (high backscatter intensity values c. -15 to -18 dB)than the surrounding finer grained sediment (lowbackscatter intensity < -24 dB) (Fig. 5d). They aretypically 2m below the surrounding fine-sediment seafloor and have SW–NE trending steep sides (Fig. 5f).

Within the broad depression south of Anchorage Island,a few curved, steep-sided ridges of material with lowbackscatter intensities are observed within the depressionswith high backscatter (Fig. 5d). This relationship suggests

Fig. 12. Enlarged shaded bathymetry image of channels southof Gardner Island with hillshade illumination from thenorth (azimuth= 0°, altitude= 45°).




that the ridges are eroded remnants of finer grainedmaterial overlying a coarser grained layer. Similar scourdepressions with remnant ridges are present at the mouth ofHeidemann Bay. Their appearance suggests that thesedepressions are probably areas of sediment erosion.

Areas beyond Davis Anchorage

Long Fjord

Long Fjord is a narrow inlet north of Davis Station wheresoundings from sea ice have recorded depths up to 222 m.Twomultibeam survey lines were run obliquely across thefjord axis between Zappert and Powell points (Fig. 13a).Long Fjord has typical fjord morphology, i.e. a steep-sided valley with a mostly flat sea floor (Fig. 13b).

The smooth sea floor suggests that most sedimentation isby settling from the water column but the fjord sideadjacent to Zappert Point displays a set of gullies runningdownslope (Fig. 13c). Immediately above thesegullies, but onshore, is a south-facing snow bank. Likemany recurring snow banks in the VestfoldHills, it containsenough debris, probably wind-blown material, to appearbanded and dark. The gullies extend from the snow bank.

Ellis Fjord

Ellis Fjord is one of the few places in Antarctica thatreceives stream flow from the continent with meltwaterfinding its way from the ice sheet edge via several lakes

Fig. 14a. Enlarged shaded bathymetry image of the entrance to Ellis Fjord with hillshade illumination from the north(azimuth= 0°, altitude= 45°). b. Cross-section showing the sea floor becoming shallower towards Westwood Point.c. Cross-section showing a step in the sea floor and narrow channel adjacent to the exposed bedrock.

Fig. 13a. Enlarged shaded bathymetry image of the mouth ofLong Fjord with hillshade illumination from the west(azimuth= 270°, altitude= 45°). b. Cross-section of the fjordentrance showing the steep sides of the fjord. c. Obliqueperspective image of multibeam swath bathymetrywithin Long Fjord showing a series of gullies. The image isviewed from the south, illumination is from the west(azimuth= 270°, altitude= 25°) and vertical scale is 5xexaggerated.




and narrow constrictions known as Ellis Narrows(Fig. 1). There are measured depths of > 100 m in theinner fjord but the outer part of the fjord is shallow;therefore, multibeam data were collected in an area only

3.3 km inside the entrance (Fig. 14a). The entranceto Ellis Fjord has a partial sill composed of a rockyoutcrop c. -16 to -18 m and a narrow valley with smoothfloor c. -25 m MSL (Fig. 14a). The fjord floor shoals

Fig. 15a. Enlarged shaded bathymetry image of sea floor to the east of Laternula Inlet with hillshade illumination from the west(azimuth= 270°, altitude= 45°). b. Cross-section of the fjord showing a steep-sided valley and smooth sea floor. c. Obliqueperspective image of multibeam swath bathymetry showing two sediment lobes on the fjord walls, east of Laternula Inlet. Theimage is viewed from the south, illumination is from the south-west (azimuth= 225°, altitude= 18°) and vertical scale is 8xexaggerated. d. Cross-section of the sediment lobes.

Fig. 16. Enlarged shaded bathymetry image of sea floor to the east of Crooked Fjord.




eastward to c. -15 to -12 m MSL near Redfern Island,where it shallows rapidly to only -2 mMSL (Fig. 14b & c)near Westwood Point.

Ellis Fjord has clusters of ice keel scours and largeboulders, particularly in deeper water near the westernend (Fig. 14a). The southern part of the fjordrecords intermediate backscatter intensity values< -21 dB with ice keel scours on its edge suggesting abank of unconsolidated sediment. Its north-easternmargin is a narrow channel c. 0.4 m deep separating thebank from the exposed bedrock of Westwood Point.

Laternula Inlet

Laternula Inlet is parallel to Ellis Fjord and c. 3 km to thesouth. It is > 60 m deep in places with a sinuous axisfloored by smooth sediment bordered by rocky outcrops(Fig. 15a). The inlet cross-section is steep-sided, typical offjords (Fig. 15b). Most of the inlet floor < 30 m is smooth;however, two lobate sediment bodies 0.5 m high arepresent on the northern side (Fig. 15d). These lobes havelong axes parallel to the slope and widen where the slopebecomes less steep.

Crooked Fjord

Crooked Fjord extends along the northern edge of theSørsdal Glacier (Fig. 1). Its seaward end shows rugged seafloor with water depths approaching -350 m MSL(Fig. 16) and a number of shallow banks and islands.The multibeam image shows rocky outcrops withlineaments running parallel to the fjord axis and theglacier edge, suggesting that basement structural graininfluences the position of the Sørsdal Glacier. Thelandward end of the fjord section surveyed displayssmoother sea floor with depths of 30–40 m, but still withrocky outcrops and islands. Iceberg scours are present inwater depths of c. -75 mMSL near the mouth of the fjord.

Discussion

The overall distribution of geomorphic units and theirelevation across the study area suggests that the landscapeexhibits three general levels separated by abrupt ‘steps’ inthe level of basins and pediments (Fig. 17). The eastern-most step marks the boundary between land areas,shallow embayments < 10 m deep (airport beachembayment and Heidemann Bay) and shallow areasbetween islands. West of the step, depths of 18–30 m aretypical, except around the steep sides of islands and rockyhills which approach the surface. The next stepcorresponds roughly to the western side of GardnerIsland and represents a drop to > 40 m water depth forbasin and valley floors. The steps themselves are a seriesof arcuate scarps and slopes which are convex to the eastand north-east. This geometry suggests they started aswest-facing, north–south trending slopes which haveretreated east in response to slope erosion. This,combined with the common north–south oriented faultsand joints visible in bedrock outcrops (Figs 1 & 4a),would imply that north–south striking faults created theinitial steps in bathymetry. The present indentationsin the steps probably reflect changes in resistance ofthe rocks encountered. The eastern-most step in thelandscape seems to mark the western limit of the boulderfields seen in the airport beach embayment andHeidemann Bay.

The undulating boulder-rich surface observed on landand in the multibeam data have been discussed by anumber of authors. Hirvas et al. (1993) suggested that theboulders were pushed to the surface by cryoturbation ofunderlying glacial till. However, they presented pebblefabrics from the underlying diamict which resembleunmodified, primary glacial till fabrics, suggestingminimal post-depositional disturbance. Franklin (1997)suggested, based on onshore examples, that the boulder-rich ridges were beach ridges, invoking a combination of

Fig. 17. Cross-section across study area showing steps in the sea floor (location indicated in Fig. 2).




sea ice push and wave working. However, this proposedmechanism does not account for the wide distribution oflarge boulders.

The multibeam survey did not reveal any of thelandforms commonly associated with glaciated surfacessuch as flutes, megascale glacial lineations or drumlins.This accords with observation of the onshore VestfoldHills (Adamson & Pickard 1983). The NE–SW trendingridges, probably formed as moraines parallel to icemargin positions, are scattered across the Vestfold Hillsbut are mostly present south-east of Davis Station(Adamson & Pickard 1983). Gore et al. (2003) classifiedthe glacial landforms preserved onshore as large debrisridges, small debris ridges, debris drapes and undulatingvalley fills. Of these landforms, the boulder fields detectedby the multibeam survey resemble the debris drapes andundulating valley fills. The lack of streamlined bedformsand similar features probably reflects glaciation by icefrozen to its bed during the last period of glaciation of theVestfold Hills. Therefore, we interpret the boulder fieldsand associated sand as deposits of cold-based ice that isknown to produce boulder-rich sand deposits (Hambrey& Fitzsimmons 2010, Hambrey & Glasser 2012).The north-west limit of the boulder fields at the stepin the landscape described above could represent the limitof the ice mass responsible for their deposition.

The mound with a depression in its crest within airportbeach embayment is located within a boulder fieldmaking it likely that it is a glacial or periglacial feature.The shape of the mound and its central depression issimilar to scars left by relict pingos (Pickard 1983).Consequently, it could be a pingo formed soon afterdeglaciation but before marine inundation, or it mightalso have formed as a small supraglacial lake depositwhich was then lowered onto an ice core.

Iceberg scour geometry in the survey area can beunderstood in terms of factors described in studies fromother regions (e.g. Hodgson et al. 1988). The pitsdeveloped where an iceberg overturned, increased itsdraft and grounded (Hodgson et al. 1988, Woodworth-Lynas et al. 1991). The iceberg then remained stationaryfor a time, excavating a pit through small-scale movementand enhanced current velocities around the iceberg(Hodgson et al. 1988). Ablation then reduced theiceberg size, it then either floated or the keel protrudedless into the substrate, reducing resistance, so it thenmoved across the bed, producing examples where a pithas a scour attached. Around the Vestfold Hills, suchpits have the accompanying scour trending south orsouth-west indicating that most icebergs drift with thelocal ocean current and prevailing north-east winds(Vaz & Lennon 1996). The lesser numbers of east–westscours probably indicate small icebergs or sea icekeels influenced by tidal currents or the occasionalsouth-west sea breeze in summer. The arcuate trend

through the Anchorage basin also reflects localoceanographic flow.

The subdued, rounded topography of the scours, therarity of clear ridge-and-groove microtopography and theabsence of angular blocks of disturbed sediment in bermsprobably reflects the properties of the sea floor sedimentsaround Davis. Hodgson et al. (1988) surveying icebergscours on the Canadian margin found that sediment withhigh sand content and low cohesion did not produce steepberm slopes or angular blocks of sediment in the scoursurcharge. The sediments around Davis likewise have lowcohesion, and therefore, do not produce steep slopes orangular blocks.

A number of features suggest erosion and deposition bycurrent activity under conditions of low sediment supply.As there have been no current meter deployments inairport beach embayment, observations of sedimentarystructures must be used to understand the origins of thesefeatures. The orientation of most of the ribbons parallel tothe prevailing north-east (from 067° T) wind suggests thatwater is driven south-west along the embayment,entraining sand provided by the beach and snow patchrun-off at the north-east shore of the embayment.However, the ripples do not show clear asymmetry onthe video images. The video transect north-west of thesand ribbons also shows rippled sand but it also shows alarge boulder with scouring on the south-west (up-currentside) and a tail of rippled sand on the north-east (lee) sideindicating current flowing from the south-west towardsthe north-east. This suggests that significant bottomsediment transport occurs when occasional south-westwinds drive water into the embayment. This water thenflows out along the south-east side of the embayment,forming the observed sand ribbons.

Published relative sea level estimates for the areasuggest that, if the channels south of Gardener Islandformed subaerialy, they have been underwater andsubjected to iceberg modification for > 12 000 years(Zwartz et al. 1998, Nakada et al. 2000). Their persistencesuggests that they are maintained by episodic bottomcurrents flowing downslope and roughly normal to theprevailing ocean currents. Thus, both the channels andsand ribbons suggest that wind-driven coastal down-welling is a significant, though episodic, process on theVestfold Hills coast.

The gullies in Long Fjord and sediment lobes inLaternula Inlet indicate that gravity-driven processes areactive on steep slopes. The Long Fjord gullies areimmediately downslope from a perennial, sediment-ladensnow bank, suggesting that they are produced by sediment-charged meltwater from the snow bank forming turbiditycurrents capable of eroding the sea floor. The LaternulaInlet sediment lobes are probably deposits of sedimentgravity flows. They lack blocks and masses of partlydisaggregated material expected in flows of cohesive




material, rather their lobate form is more like deposits ofhighly concentrated sand-water flows (Carter 1975).

Several basin areas contain eroded areas resemblingshelf scour depressions. Proposed mechanisms for theformation of these depressions include tidal scour (Bellecet al. 2010), cross-shore currents (Cacchione et al. 1984),storm-generated down-welling (Garnaud et al. 2005), andalong-shore currents. It is likely that scouring is inducedby strong flows steered and concentrated by the bedrockoutcrops across the area (Cacchione et al. 1984). Nocurrent measurements are available on the inner shelfwithin the domain of the scour depressions; however, it isreasonable to assume that enhanced bottom stressesproduced by focusing of local currents are capable ofre-suspending and transporting the surficial fine sediment(Cacchione et al. 1984). The scour depressions atthe seaward end of Heidemann Bay may be of tidalorigin as they are sheltered from the main north–southcurrents.

The airport beach embayment sand ribbons andchannels on the pediment south of Gardener Island areprobably the result of wind-driven down-welling currents.The scour depression between islands and bedrock hills aremore probably formed by constriction of oceanographiccurrents by topography. Published accounts of modernsediment transport in the Vestfold Hills have emphasizedwind erosion and transport (Pickard 1982, Adamson &Pickard 1986b), fluvial transport derived from snow and icemargin melt (Fitzsimmons 1991), subaerial massmovement (Fitzsimmons 1996) and wave reworking ofshoreline deposits (Peterson et al. 1988). Our multibeamdata show that wind-driven and oceanographic currentsalso play a role in transporting sediment. Ice keel scouringmust also enhance sediment mobility by dislodging finematerial and making it more susceptible to geostrophic ortidal currents. The data from steep fjords shows evidenceof mass transport processes redistributing sedimentfrom the shoreline into deep water in the form of turbiditycurrent gullies and lobate mass transport deposits. Theoverall impression of the area is that it is a landscapecovered by slow-moving glacial ice which has beenmodified by marine processes after deglaciation. Thiscontrasts with Prydz Bay to the west where fast-flowingice streams have been a feature through the Cenozoic(O’Brien et al. 2007). This adds to a picture of glaciationof the Antarctic coast involving fast-flowing outletglaciers in deep troughs and slow-moving cold ice oreven unglaciated areas in areas of higher elevation(Mackintosh et al. 2014).

Conclusions

Multibeam sonar, underwater video and sedimentsampling allow the mapping of geomorphic units andprovide insights into sea floor processes and environments

in the nearshore areas of the Vestfold Hills. Mapped unitsinclude rocky outcrops, sediment-floored basins,pediments, valleys, scarps and embayments protectedfrom scouring by floating ice. Iceberg scours are plentiful,and sand ribbons and sea floor channels indicatesignificant sediment movement by marine currents.Steep-sided valleys show features formed by sedimentgravity flows. Features formed by subglacial depositionare not common with undulating, boulder-rich sand unitsrepresenting deposition by cold-based ice. Thegeomorphic map presents an integrated view of the seafloor that can be used to understand the distribution ofbenthic habitats, the action of sea floor sedimentaryprocesses and provides pointers to the past history of thearea. Identification of features produced by sedimenterosion and deposition point to processes that shape thebenthic environment but which have not been observeddirectly to date.

Acknowledgements

We thank Ian Atkinson (GA), Ross Bowden, Dean Forrest,Jade Paddison and Steven Swanson (RAN) for surveyassistance, Michele Spinoccia, Olivia Wilson andDr Justy Siwabessy (GA) for processing the multibeamdata, andDrAlix Post (GA) for assistingwith interpretationand analysis of the underwater video data. This researchwaspart of Australian Antarctic Science (AAS) Project 2201 –

Natural Variability and Human Induced Change onAntarctic Nearshore Marine Benthic Communities (CI:Martin Riddle). The bathymetry data collection was part ofAustralian Antarctic Division non-science Project 3259 –

Hydrographic Charting of Antarctic Waters. Dr ScottNichol, Dr Kim Picard, Prof Mike Hambrey and ananonymous reviewer are thanked for their review of thismanuscript. This paper is published with the permission ofthe Chief Executive Officer, Geoscience Australia.

© Commonwealth of Australia (GeoscienceAustralia) 2015.

Author contribution

Philip E. O’Brien: survey design, multibeam surveyoperation, video data collection, data processing,geomorphic mapping and interpretation, text andpaper preparation. Jodie Smith: backscatter andautomated geomorphic mapping and interpretation,PCA analysis, text and figure preparation. JonathanStark: sediment and video sampling, sample analysisand interpretation. Glenn Johnston: sediment andvideo sampling, sample analysis and interpretation.Martin Riddle: survey design and interpretation.Denis Franklin: sediment sampling, analysis andinterpretation.




Supplemental material

Two supplemental figures will be found at http://dx.doi.org/10.1017/S0954102015000371.

References

ADAMSON, D.A. & PICKARD, J. 1983. Late Quaternary ice movementacross the VestfoldHills, East Antarctica. InOLIVER, R.L., JAMES P.R.& JAGO, J.B., eds. Antarctic earth sciences. Canberra: AustralianAcademy Press, 465–469.

ADAMSON, D.A. & PICKARD, J. 1986a. Cainozoic history of the VestfoldHills. In PICKARD, J.D., ed. Antarctic oasis: terrestrial environmentsand history of the Vestfold Hills. Sydney: Academic Press, 63–97.

ADAMSON, D.A. & PICKARD, J. 1986b. Physiography andgeomorphology of the Vestfold Hills. In PICKARD, J.D., ed. Antarcticoasis: terrestrial environments and history of the Vestfold Hills. Sydney:Academic Press, 99–139.

ANDERSON, T.J., COCHRANE, G.R., ROBERTS, D.A., CHEZAR, H. &HATCHER, G. 2008. A rapid method to characterize seabed habitatsand associated macro-organisms. In TODD, B.J. & GREEN, H.G., eds.Mapping the sea floor for habitat characterization. GeologicalAssociation of Canada Special Paper, No. 47, 71–79.

BARRIE, J.V., LEWIS, C.F.M., PARROTT, D.R. & COLLINS, W.T. 1992.Submersible observations of an iceberg pit and scour on the GrandBanks of Newfoundland. Geo-Marine Letters, 12, 10.1007/BF02092101.

BELLEC, V.K., BØE, R., RISE, L., SLAGSTAD, D., LONGVA, O. & DOLAN,M.F.J. 2010. Rippled scour depressions on continental shelf bankslopes off Nordland and Troms, Northern Norway. Continental ShelfResearch, 30, 1056–1069.

BEYER, L. &BÖLTER,M., eds. 2002.Geoecology of Antarctic ice-free coastallandscapes. Ecological studies, Vol. 154. Berlin: Springer, 429 pp.

BUREAU OF METEOROLOGY, AUSTRALIA. 2013. Climate statistics forAustralian locations, Davis. Available at: http://www.bom.gov.au/climate/averages/tables/cw_300000.shtml.

CACCHIONE, D.A., DRAKE, D.E., GRANT, W.D. & TATE, G.B. 1984.Rippled scour depressions on the inner continental shelf off centralCalifornia. Journal of Sedimentary Petrology, 54, 1280–1291.

CARTER, R.M. 1975. Mass-emplaced sand-fingers at a Mararoaconstruction site, southernNewZealand. Sedimentology, 22, 275–288.

COLLERSON, K.D. & SHERATON, J.W. 1986. Bedrock geology and crustalevolution of the Vestfold Hills. In PICKARD, J.D., ed. Antarctic oasis:terrestrial environments and history of the Vestfold Hills. Sydney:Academic Press, 21–62.

COLHOUN, E.A., KIERNAN, K.W., MCCONNELL, A., QUILTY, P.G.,FINK, D., MURRAY-WALLACE, C.V. & WHITEHEAD, J. 2010. LatePliocene age of glacial deposits at Heidemann Valley, East Antarctica:evidence for the last major glaciation in the Vestfold Hills. AntarcticScience, 22, 53–64.

DOHRENWEND, J.C. & PARSONS, A.J. 2009. Pediments in aridenvironments. In PARSONS, A.J. & ABRAHAMS, A.D., eds.Geomorphology of desert environments. Berlin: Springer, 377–411.

FINKL, C.W. & MAKOWSKI, C. 2015. Autoclassification versus cognitiveinterpretation of digital bathymetric data in terms ofgeomorphological features in sea floor characterization. Journal ofCoastal Research, 31, 1–16.

FITZSIMMONS, S.J. 1991. Supraglacial eskers in Antarctica.Geomorphology, 4, 293–299.

FITZSIMMONS, S.J. 1996. Paraglacial redistribution of glacial sediments inthe Vestfold Hills, East Antarctica. Geomorphology, 15, 93–108.

FOLK, R.L. 1954. The distinction between grain size and mineralcomposition in sedimentary rock nomenclature. Journal of Geology,62, 344–359.

FRANKLIN, D. 1997. The sedimentology of Holocene Prydz Bay:sedimentary patterns and processes. PhD thesis, Antarctic CRC andInstitute of Antarctic and Southern Ocean Studies, University ofTasmania, Hobart, 216 pp. [Unpublished].

GARNAUD, S., LESUEUR, P. & GARLAN, T. 2005. Origin of rippled scourdepressions associated with cohesive sediments in a shoreface setting(eastern Bay of Seine, France). Geo-Marine Letters, 25, 34–42.

GORE, D.B., SNAPE, I. & LEISHMAN, M.R. 2003. Glacial sedimentprovenance, dispersal and deposition, Vestfold Hills, East Antarctica.Antarctic Science, 15, 259–269.

HAMBREY, M.J. & FITZSIMMONS, S.J. 2010. Development of sediment-landform associations at cold glacier margins, Dry Valleys,Antarctica. Sedimentology, 57, 857–882.

HAMBREY, M.J. & GLASSER, N.F. 2012. Discriminating glacier thermalregimes in the sedimentary record. Sedimentary Geology, 251, 1–33.

HEIRI, O., LOTTER, A.F. & LEMCKE, G. 2001. Loss on ignition as amethod for estimating organic and carbonate content in sediments:reproducibility and comparability of results. Journal ofPaleolimnology, 25, 101–110.

HIRVAS, H., NENONEN, K. & QUILTY, P. 1993. Till stratigraphy andglacial history of the Vestfold Hills area, East Antarctica. QuaternaryInternational, 18, 81–95.

HODGSON, G.J., LEVER, J.H., WOODWORTH-LYNAS, C.M.T & LEWIS, C.F.M. 1988. The Dynamics of Iceberg Grounding and Scouring (DIGS)experiment and repetitive mapping of the eastern Canadian continentalshelf. Environmental Studies Research Funds Report 094, 315 pp.

LUCIEER, V., HILL, N.A., BARRETT, N.S. & NICHOL, S. 2013. Do marinesubstrates ‘look’ and ‘sound’ the same? Supervised classification ofmultibeam acoustic data using autonomous underwatervehicle images. Estuarine Coastal and Shelf Science, 117, 94–106.

MACKINTOSH, A.N., VERLEYEN, E., O’BRIEN, P.E., WHITE, D.A., JONES,R.S., MCKAY, R., DUNBAR, R., GORE, D.B., FINK, D., POST, A.L.,MIURA, H., LEVENTER, A., GOODWIN, I., HODGSON, D.A., LILLY, K.,CROSTA, X., GOLLEDGE, N.R., WAGNER, B., BERG, S., VAN OMMEN, T.,ZWARTZ, D., ROBERTS, S.J., VYVERMAN,W.&MASSE, G. 2014. Retreathistory of the East Antarctic Ice Sheet since the Last GlacialMaximum. Quaternary Science Reviews, 100, 10–30.

MAKARUCHA, L. 1984.Davis airstrip Antarctica site investigation summer82/83. Department of Housing and Construction, CentralInvestigation and Research Laboratory, major report no. 250.

MORTLOCK, R.A. & FROELICH, P.N. 1989. A simple method for the rapiddetermination of biogenic opal in pelagic marine sediments.Deep-SeaResearch I - Oceanographic Research Papers, 36, 1415–1426.

MULLER, G. & GASTNER, M. 1971. The “karbonate bombe” a simpledevice for the determination of the carbonate content in sediments,soils and other materials. Neues Jahrbuch Fur Mineralogie-Monatshefte, 10, 466–469.

NAKADA, M., KIMURA, R., OKUNO, J., MORIWAKI, K., MIURA, H. &MAEMOKU, H. 2000. Late Pleistocene and Holocene melting history ofthe Antarctic ice sheet derived from sea-level variations. MarineGeology, 167, 85–103.

O’BRIEN, P.E., GOODWIN, I., FORSBERG, C.F., COOPER, A.K. &WHITEHEAD, J. 2007. Late Neogene ice drainage changes in PrydzBay, East Antarctica and the interaction of Antarctic ice sheetevolution and climate. Palaeogeography, Palaeoclimatology,Palaeoecology, 245, 390–410.

O’BRIEN, P.E., STARK, J.S., JOHNSTONE, G., SMITH, J. & RIDDLE, M.J.2012. Seabed character and habitats of a rocky Antarctic coastline:Vestfold Hills, East Antarctica. In HARRIS, P.T. & BAKER, E.K., eds.Sea floor geomorphology as benthic habitat: GeoHAB atlas of sea floorgeomorphic features and benthic habitats. Amsterdam: Elsevier,329–337.

Ó COFAIGH, C. 2015. Ice sheets viewed from the ocean: the contributionof marine science to understanding modern and past ice sheets.Philosophical Transactions of the Royal Society, A370, 5512–5539.


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PETERSON, J.A., FINLAYSON, B.L. & ZHANG, Q.S. 1988. Changingdistribution of Late Quaternary terrestrial lacustrine and littoralenvironments in the Vestfold Hills, Antarctica. Hydrobiologia, 165,221–226.

PICKARD, J. 1982. Holocene winds of the Vestfold Hills, Antarctica.New Zealand Journal of Geology and Geophysics, 25, 353–358.

PICKARD, J. 1983. Pingos in Antarctica. Quaternary Research, 20,105–109.

POST, A.L., BEAMAN, R.J., O’BRIEN, P.E., ELÉAUME, M. & RIDDLE, M.J.2011. Community structure and benthic habitats across theGeorge V Shelf, East Antarctica: trends through space andtime. Deep-Sea Research II - Topical Studies in Oceanography, 58,105–118.

QUILTY, P.G. 2006. Landform evolution in the Marine Plain region,Vestfold Hills, East Antarctica. Antarctic Science, 18, 239–259.

QUILTY, P.G., LIRIO, J.M. & JILLETT, D. 2000. Stratigraphy of thePliocene Sørsdal Formation, Marine Plain, Vestfold Hills, EastAntarctica. Antarctic Science, 12, 205–216.

SHAW, J., TODD, B.J. & LI,M.Z. 2014. Geologic insights frommultibeambathymetry and seascape maps of the Bay of Fundy, Canada.Continental Shelf Research, 83, 53–63.

SMITH, J., O’BRIEN, P.E., STARK, J.S., JOHNSTONE, G.J. & RIDDLE, M.J.2015. Integrating multibeam sonar and underwater video data to map

benthic habitats in an East Antarctic nearshore environment.Estuarine, Coastal and Shelf Science, 10.1016/j.ecss.2015.07.036.

STAGG, H.M.J. 1985. The structure and origin of Prydz Bay and Mac.Robertson shelf, East Antarctica. Tectonophysics, 114, 315–340.

TAROLLI, P. 2014. High-resolution topography for understanding Earthsurface processes: opportunities and challenges. Geomorphology, 216,295–312.

TER BRAAK, C.J.F. & ŠMILAUER, P. 2012. CANOCO reference manualand user’s guide: software for ordination, version 5.0. Ithaca, NY:Microcomputer Power, 496 pp.

TUCKER, M.J. 1988. Temporal distribution and brooding behavior ofselected benthic species from the shallow marine waters off theVestfold Hills, Antarctica. Hydrobiologia, 165, 151–159.

VAZ, R.A.N. & LENNON, G.W. 1996. Physical oceanography of thePrydz Bay region of Antarctic waters. Deep-Sea Research I -Oceanographic Research Papers, 43, 603–641.

WOODWORTH-LYNAS, C.M.T., JOSENHANS, H.W., BARRIE, J.V.,LEWIS, C.F.M. & PARROTT, D.R. 1991. The physical processes ofseabed disturbance during iceberg grounding and scouring.Continental Shelf Research, 11, 939–961.

ZWARTZ, D., BIRD, M., STONE, J. & LAMBECK, K. 1998. Holocenesea-level change and ice-sheet history in the Vestfold Hills, Antarctica.Earth and Planetary Science Letters, 155, 131–145.



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Submarine geomorphology and sea ﬂoor processes along …Shaded multibeam bathymetry map of the study area (2m cell size grid, UTM Zone 43S projection). Hillshade illumination in