Geochronology of bonney drift, taylor valley, antarctica: evidence for interglacial expansions of taylor glacier

Abstract

Lacustrine algal carbonates, which form in shallow proglacial lakes, were found in most excavations into Bonney drift. Both in situ and reworked carbonate samples produced 49 new uranium/thorium (U/ Th) dates. U/Th dates of 70 to 130 ka for samples collected from excavations and natural sections, along with geomorphologic evidence reported elsewhere in this issue, confirm that the Bonney advance of Taylor Glacier, along with the concurrent expansion of local alpine glaciers, occurred during the interglaciation corresponding with marine isotope stage (MIS) 5. In addition, δ 18 O values (-35 to -43‰) of the algal carbonates confirm deposition in a proglacial lake fed by Taylor Glacier meltwater. The detailed distribution of U/Th dates shows that Bonney ice advances occurred in substages 5a, 5c, and 5e. The δ 18 O record of the Taylor Dome ice core also indicates ice thickening during these same intervals. The inclusion of older carbonates in Bonney drift affords evidence for proglacial lakes during MIS 7 (160 to 240 ka), MIS 9 (270 to 330 ka), and MIS 11 or older (>370 ka). It is probable that these proglacial lakes were also associated with interglacial expansions of Taylor Glacier. This terrestrial U/Th geochronology affords a regional constraint on the late Quaternary behavior of the peripheral sector of the EAIS drained by Taylor Glacier, consistent with expansion during global interglaciations and recession during global glaciations.

The Geochemistry of Englacial Brine From Taylor Glacier, Antarctica

“…Stuiver et al () suggested that this water was initially “trapped” in the valley when sea level was lower, and then as sea level rose, seawater intruded from below. As noted above, advances and retreats of Taylor Glacier are well documented over time, and the lacustrine carbonates associated with proglacial lakes in what is now central Taylor Valley have δ 18 O formed from Taylor Glacier‐derived melt (Higgins et al, ). These advances of Taylor Glacier and the development of more eastward Taylor Glacier proglacial lakes occurred during Marine Isotopic stages 5a, 5c, 5e, 7, 9, and 11 (Higgins et al, ).…”

Palaeoshoreline records of glacial isostatic adjustment in the Dry Valleys region, Antarctica

“…Utilizing published descriptions of the location, elevation and signature of preserved palaeoshorelines as a starting point, imagery derived from LiDAR coverages around known modern and ancient lake margins were scrutinized to visually identify preserved strandlines. In most cases, published literature provided the specific location of individual shorelines and provided evidence for a shoreline origin not easily attainable through remote-sensing techniques, including the presence of lacustrine algae and internal lithology (Clayton-Greene et al 1988;Butler 1999;Hall & Denton 1999, 2000Hendy 2000;Higgins et al 2000;Hall et al 2001Hall et al , 2004. Palaeoshorelines in the Dry Valleys region are characterized by 'step-andtread' cross-sectional profiles (Hendy 2000), distinct from the morphology of other glacial features.…”

“…Higgins et al 2000). While numerous lacustrine strandlines are preserved, identifying and correlating individual shoreline features in the LiDAR data is difficult owing to overprinting of features.…”

“…The resulting tilt direction is down to the SE towards 151.88 and the tilt magnitude is 6.2 m/km. Because this strandline is not dated directly, we rely on relative age constraints provided by radiocarbon dating of deltas that indicate Glacial Lake Washburn existed in central Taylor Valley from 23 800 to 10 000 14 C yr BP (Higgins et al 2000;Hall et al 2010a). report a peak in the number of deltas dated within Taylor Valley at 11 000-15 000 14 C. The 13 000 14 C yr BP midpoint from this range also corresponds to the midpoint for deltas at the elevation of the proposed Bonney shoreline included in our analysis (above 300 m).…”

Paleosols in the Transantarctic Mountains: indicators of environmental change

“…Previous investigations in Antarctica have examined lithified paleosols of late Paleozoic to early Triassic age (Retallack and Alonso-Zarza, 1998) and well-known exposures of semi-lithified paleosols of Miocene age (Retallack et al, 2002; Mahaney et al, 2001Mahaney et al, , 2012. Relict soils along the edge of the polar plateau throughout the TAMs have properties resulting from hyper-arid conditions, suggesting that the climate has remained cold and dry since the Miocene (Marchant et al, 1994).…”