Subglacial bedforms reveal complex basal regime in a zone of paleo–ice stream convergence, Amundsen Sea embayment, West Antarctica

Larter, Robert D; Graham, Alastair G C; Gohl, Karsten; Kuhn, Gerhard; Hillenbrand, Claus‐Dieter; Smith, James A; Deen, T.; Livermore, Roy; Schenke, Hans-Werner

doi:10.1130/g25505a.1

Cited by 113 publications

(105 citation statements)

References 31 publications

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“…Detailed mapping of bedforms in a continuous cross-shelf trough has yielded results consistent with a previous interpretation that these form a complex palaeo-ice stream landsystem in the western ASE (Stokes and Clark, 1999;Larter et al, 2009). Larter et al (2009) summarised that the shelf downflow of the bedforms mapped in our dataset lacks significant ice marginal geomorphology (e.g.…”

Section: Reconstruction Of Palaeo-ice Stream Flowsupporting

confidence: 83%

“…TOPAS and PARASOUND profiles image the sea floor and sub-surface at a high resolution (up to about 1 m vertically), to as much as w50 m below sea floor (see supplementary material in Larter et al, 2009). Sediment coring was also undertaken to obtain detailed information about the nature of the sea-floor sediments (see Larter et al, 2007;Smith et al, 2009 and Hillenbrand et al, in press).…”

Section: Methodsmentioning

confidence: 99%

“…Wellner et al (2001) also showed that this was a common scenario for many palaeo-ice streams around West Antarctica, and inferred that substrate conditions had a major influence upon ice stream establishment, bed morphology and flow at the LGM. Recently, Larter et al (2009) presented an overview of new multibeam bathymetry data from the western ASE, showing that there was an extensive LGM ice stream characterised by a complex arrangement of subglacial bedforms along its track. While the authors suggested a strong relationship between basal conditions and substrate for this ice stream, no new constraints on substrate type and only limited detail have been presented on the landform signature to-date.…”

Section: Previous Work In the Amundsen Sea Embaymentmentioning

confidence: 99%

“…Previous work on palaeo-ice flow in the ASE using marine geophysical data showed bedform evidence for former ice stream flows toward the shelf edge at the LGM (Wellner et al, 2001;Lowe and Anderson, 2002;Evans et al, 2006;Larter et al, 2009). In the eastern ASE, Anderson (2002, 2003) distinguished a series of discrete geomorphic zones along one particular palaeoice stream track.…”

Section: Introductionmentioning

confidence: 96%

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Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

Graham

Larter

Gohl

et al. 2009

Quaternary Science Reviews

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174

173

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a b s t r a c tThe presence of a complex bedform arrangement on the sea floor of the continental shelf in the western Amundsen Sea Embayment, West Antarctica, indicates a multi-temporal record of flow related to the activity of one or more ice streams in the past. Mapping and division of the bedforms into distinct landform assemblages reveals their time-transgressive history, which implies that bedforms can neither be considered part of a single downflow continuum nor a direct proxy for palaeo-ice velocity, as suggested previously. A main control on the bedform imprint is the geology of the shelf, which is divided broadly between rough bedrock on the inner shelf, and smooth, dipping sedimentary strata on the middle to outer shelf. Inner shelf bedform variability is well preserved, revealing information about local, complex basal ice conditions, meltwater flow, and ice dynamics over time. These details, which are not apparent at the scale of regional morphological studies, indicate that past ice streams flowed across the entire shelf at times, and often had onset zones that lay within the interior of the Antarctic Ice Sheet today. In contrast, highly elongated subglacial bedforms on sedimentary strata of the middle to outer shelf represent a timeslice snapshot of the last activity of ice stream flow, and may be a truer representation of fast palaeo-ice flow in these locations. A revised model for ice streams on the shelf captures complicated multi-temporal bedform patterns associated with an Antarctic palaeo-ice stream for the first time, and confirms a strong substrate control on a major ice stream system that drained the West Antarctic Ice Sheet during the Late Quaternary.

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Section: Reconstruction Of Palaeo-ice Stream Flowsupporting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Section: Previous Work In the Amundsen Sea Embaymentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

Graham

Larter

Gohl

et al. 2009

Quaternary Science Reviews

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174

173

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“…Shipp et al, 1999;Wellner et al, 2001Wellner et al, , 2006Lowe and Anderson, 2002;Heroy and Anderson, 2005;Ó Cofaigh et al, 2005a,b;Walker et al, 2007;Larter et al, 2009). The ice stream flowing through Belgica Trough also probably differed from other West Antarctic ice streams, because it drained an area >200,000 km 2 in the hinterland (see Fig.…”

Section: History Of Ice-sheet Retreatmentioning

confidence: 99%

The sedimentary legacy of a palaeo-ice stream on the shelf of the southern Bellingshausen Sea: Clues to West Antarctic glacial history during the Late Quaternary

Hillenbrand

Larter

Dowdeswell

et al. 2010

Quaternary Science Reviews

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a b s t r a c tA major trough ("Belgica Trough") eroded by a palaeo-ice stream crosses the continental shelf of the southern Bellingshausen Sea (West Antarctica) and is associated with a trough mouth fan ("Belgica TMF") on the adjacent continental slope. Previous marine geophysical and geological studies investigated the bathymetry and geomorphology of Belgica Trough and Belgica TMF, erosional and depositional processes associated with bedform formation, and the temporal and spatial changes in clay mineral provenance of subglacial and glaciomarine sediments.Here, we present multi-proxy data from sediment cores recovered from the shelf and uppermost slope in the southern Bellingshausen Sea and reconstruct the ice-sheet history since the last glacial maximum (LGM) in this poorly studied area of West Antarctica. We combined new data (physical properties, sedimentary structures, geochemical and grain-size data) with published data (shear strength, clay mineral assemblages) to refine a previous facies classification for the sediments. The multi-proxy approach allowed us to distinguish four main facies types and to assign them to the following depositional settings: 1) subglacial, 2) proximal grounding-line, 3) distal sub-ice shelf/sub-sea ice, and 4) seasonal open-marine. In the seasonal open-marine facies we found evidence for episodic currentinduced winnowing of near-seabed sediments on the middle to outer shelf and at the uppermost slope during the late Holocene.In addition, we obtained data on excess 210 Pb activity at three core sites and 44 AMS 14 C dates from the acid-insoluble fraction of organic matter (AIO) and calcareous (micro-) fossils, respectively, at 12 sites. These chronological data enabled us to reconstruct, for the first time, the timing of the last advance and retreat of the West Antarctic Ice Sheet (WAIS) and the Antarctic Peninsula Ice Sheet (APIS) in the southern Bellingshausen Sea. We used the down-core variability in sediment provenance inferred from clay mineral changes to identify the most reliable AIO 14 C ages for ice-sheet retreat. The palaeo-ice stream advanced through Belgica Trough after w36.0 corrected 14 C ka before present (B.P.). It retreated from the outer shelf at w25.5 ka B.P., the middle shelf at w19.8 ka B.P., the inner shelf in Eltanin Bay at w12.3 ka B.P., and the inner shelf in Ronne Entrance at w6.3 ka B.P. The retreat of the WAIS and APIS occurred slowly and stepwise, and may still be in progress. This dynamical ice-sheet behaviour has to be taken into account for the interpretation of recent and the prediction of future mass-balance changes in the study area. The glacial history of the southern Bellingshausen Sea is unique when compared to other regions in West Antarctica, but some open questions regarding its chronology need to be addressed by future work.

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Airborne radar sounding evidence for deformable sediments and outcropping bedrock beneath Thwaites Glacier, West Antarctica

Schroeder

Blankenship

Young

et al. 2014

Geophysical Research Letters

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The geologic and morphologic records of prior ice sheet configurations show evidence of rapid, back-stepping, meltwater intensive retreats. However, the potential for such a retreat in a contemporary glacier depends on the lithology of the current ice sheet bed, which lies beneath kilometers of ice, making its physical properties difficult to constrain. We use radar sounding and marine bathymetry data to compare the bed configuration of Thwaites Glacier to the bed of paleo-Pine Island Glacier. Using observed and modeled radar scattering, we show that the tributaries and upper trunk of Thwaites Glacier are underlain by ice flow-aligned bedforms consistent with deformable sediment and that the lower trunk is grounded on a region of high bed roughness consistent with outcropping bedrock. This is the same configuration as paleo-Pine Island Glacier during its retreat across the inner continental shelf.

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Subglacial bedforms reveal complex basal regime in a zone of paleo–ice stream convergence, Amundsen Sea embayment, West Antarctica

Cited by 113 publications

References 31 publications

Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

The sedimentary legacy of a palaeo-ice stream on the shelf of the southern Bellingshausen Sea: Clues to West Antarctic glacial history during the Late Quaternary

Airborne radar sounding evidence for deformable sediments and outcropping bedrock beneath Thwaites Glacier, West Antarctica

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