Late Wisconsin and Early Holocene Glacial History, Inner Ross Embayment, Antarctica

Abstract

Lateral drift sheets of outlet glaciers that pass through the Transantarctic Mountains constrain past changes of the huge Ross ice drainage system of the Antarctic Ice Sheet. Drift stratigraphy suggests correlation of Reedy III (Reedy Glacier), Beardmore (Beardmore Glacier), Britannia (Hatherton/Darwin Glaciers), Ross Sea (McMurdo Sound), and “younger” (Terra Nova Bay) drifts; radiocarbon dates place the outer limits of Ross Sea drift in late Wisconsin time at 24,000–13,000 yr B.P. Outlet-glacier profiles from these drifts constrain late Wisconsin ice-sheet surface elevations. Within these constraints, we give two extreme late Wisconsin reconstructions of the Ross ice drainage system. Both show little elevation change of the polar plateau coincident with extensive ice-shelf grounding along the inner Ross Embayment. However, in the central Ross Embayment one reconstruction shows floating shelf ice, whereas the other shows a grounded ice sheet. Massive late Wisconsin/Holocene recession of grounded ice from the western Ross Embayment, which was underway at 13,040 yr B.P. and completed by 6600-6020 yr B.P., was accompanied by little change in plateau ice levels inland of the Transantarctic Mountains. Sea level and basal melting probably controlled the extent of grounded ice in the Ross Embayment. The interplay between the precipitation (low late Wisconsin and high Holocene values) and the influence of grounding on outlet glaciers (late Wisconsin thickening and late Wisconsin/Holocene thinning, with effects dying out inland) probably controlled minor elevation changes of the polar plateau.

Surface exposure geochronology using cosmogenic nuclides : applications in Antarctic glacial geology

“…Most of the samples discussed here are quartz sandstones collected from a well-exposed sequence of moraines in Arena Valley, the "Taylor II-IVb" moraines and drifts in the informal nomenclature of Denton et al (1989). The sandstones are derived from rocks of the Beacon Supergroup, which make up much of the cliffs surrounding the valley .…”

“…ton et al, 1989;. Rock weathering, soil development, and stratigraphic relationships indicate that the relative ages of these deposits increase from Taylor II to Taylor IVb (Bockheim, 1982;Denton et al, 1989;. There is little absolute chronological 0033-5894/93 $5.00…”

“…control for these deposits in Arena Valley, but U-Th dating of lake carbonates in lower Taylor Valley , suggests that Taylor Glacier and the East Antarctic Ice Sheet advance during global interglacial periods, when moisture supply to interior east Antarctica increases. Denton et al (1989) and correlated the Taylor II and Taylor III moraines in Arena Valley with isotope stage 5 and 7 moraines in lower Taylor Valley on the basis of soil development and weathering characteristics. Apart from these correlations and the 'oBe and 26 A1 data of (discussed below), there are no prior age constraints for these deposits.…”

“…Taylor 11 as summarized by Denton et al (1989). SSCW87-4-1 and SCW87-5 ommitted from calculations for Taylor II and 111, respectively.…”

Chapter 5 Cenozoic Climate History from Seismic Reflection and Drilling Studies on the Antarctic Continental Margin

“…The last glacial maximum (LGM) in the Ross Sea has been studied using seafloor cores, subbottom and swath bathymetry data (Thomas and Bentley, 1978;Kellogg et al, 1979;Denton et al, 1989;Leventer et al, 1993;Brambati et al, 1994;Hilfinger et al, 1995;Kellogg et al, 1996; Cenozoic Climate History from Seismic Reflection and Drilling Studies 125 1996;Cunningham et al, 1999;Domack et al, 1999;Licht et al, 1999;Shipp et al, 1999;Alley and Bindschadler, 2001). Radiocarbon dates from diamictons and sediment composition, indicate that ice-free conditions existed on the inner shelf at times during the period from 60 to 10 ka, and that the ice sheet was present between 26.5 and 19.5 ka.…”