Provenance changes between recent and glacial-time sediments in the Amundsen Sea embayment, West Antarctica: clay mineral assemblage evidence

Abstract

Abstract:The Amundsen Sea embayment is a probable site for the initiation of a future collapse of the West Antarctic Ice Sheet. This paper contributes to a better understanding of the transport pathways of subglacial sediments into this embayment at present and during the last glacial period. It discusses the clay mineral composition of sediment samples taken from the seafloor surface and marine cores in order to decipher spatial and temporal changes in the sediment provenance. The most striking feature in the presentday clay mineral distribution is the high concentration of kaolinite, which is mainly supplied by the Thwaites Glacier system and indicates the presence of hitherto unknown kaolinite-bearing sedimentary strata in the hinterland, probably in the Byrd Subglacial Basin. The main illite input is via the Pine Island Glacier. Smectite originates from the erosion of volcanic rocks in Ellsworth Land and western Marie Byrd Land. The clay mineral assemblages in diamictons deposited during the last glacial period are distinctly different from those in corresponding surface sediments. This relationship indicates that glacial sediment sources were different from modern ones, which could reflect changes in the catchment areas of the glaciers and ice streams.

Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

“…6g). This change in clay mineral assemblage is characteristic of similar transitional sequences recording ice-sheet deglaciation on the West Antarctic shelf5960. The upper ∼2 m of the core (Unit III) is a bioturbated diatom-bearing mud interbedded with discrete 1–20 cm thick gravel layers.…”

Seismic stratigraphic record of the Amundsen Sea Embayment shelf from pre-glacial to recent times: Evidence for a dynamic West Antarctic ice sheet

“…The retreat of the ice sheet from the ASE shelf since the LGM is documented in both these swath-bathymetric records and sedimentary facies sequences recovered in cores (Lowe and Anderson, 2002;Smith et al, 2009Smith et al, , 2011Hillenbrand et al, 2010Hillenbrand et al, , 2013Ehrmann et al, 2011;Jakobsson et al, 2011;Kirshner et al, 2012;Nitsche et al, 2013). According to these studies, most of the grounded ice had retreated to the inner shelf already by the early Holocene.…”

New constraints on the timing of West Antarctic Ice Sheet retreat in the eastern Amundsen Sea since the Last Glacial Maximum

“…Individual sediment sub-samples (1 cm-thick slices) were then taken every 5-20 cm to determine contents of water, total carbon (TC), organic carbon (C org ) and total nitrogen (N tot ) and to analyse grain-size composition using techniques outlined in Smith et al (2011). The relative contents of the clay minerals smectite, illite, chlorite and kaolinite were determined on an aliquot of the <2 m fraction using standard X-ray diffraction methods described in Ehrmann et al (2011). AMS 14 C dating was carried out at the NERC Radiocarbon Laboratory (Environment) in East Kilbride (UK), and BETA Analytic Inc., Miami, Florida, U.S.A. (with prefix SUERC and BETA respectively in Table 1).…”

“…This pattern indicates differences in the flux of reworked fossil organic carbon from the catchment which is in agreement with the mapped clay mineral provenance data . Ehrmann et al (2011) showed that the highest concentrations of kaolinite occur north of Thwaites Glacier whilst the lowest values are found near the Cosgrove Ice Shelf. Kaolinite indicates the presence of preOligocene sedimentary strata in the hinterland (or sediments containing recycled preOligocene detritus) and potentially provides a proxy for the input of reworked fossil organic carbon because such sedimentary strata are often enriched in organic matter.…”