Glacial sequence stratigraphy of ANDRILL‐1B core reveals a dynamic subpolar Antarctic Ice Sheet in Ross Sea during the late Miocene

Abstract

The Upper Miocene interval of the AND‐1B sediment core is a muddy ca 300 m thick succession of glacimarine strata that was recovered from the McMurdo sector of the Ross Ice Shelf, Antarctica. This succession comprises lithofacies consistent with those formed in modern polythermal glacial systems with large volumes of subglacial meltwater. In particular, meltwater‐associated facies and iceberg‐rafted debris suggest that these late Miocene glacial systems were similar to subpolar glaciers like those in Svalbard today. Modern subpolar systems in Svalbard accumulate sediments at rates of ca 50 to 100 mm a−1 within ca 1 km of their grounded tidewater cliffs in waters up to hundreds of metres deep. Here, the rifted tectonic setting and glacio‐isostatic load of the Antarctic Ice Sheet enhanced accommodation for this succession. Based on these interpretations, the glacial sequence stratigraphic model of Powell & Cooper (2002) is applied to the study interval in an effort to better understand ice dynamics during this time. Base level is defined as the grounding line (where the ice sheet is grounded on the sea floor) and the surface that projects basinward (a correlative conformity). Glacial sequence stratigraphic description of the sediment core reveals 10 glacial sequences bounded by glacial erosion surfaces and two lower‐ranked glacial sequences bounded by correlative conformities. These glacial sequences occur in regular fining‐upward stratigraphic patterns and consist of two distinct styles of glacial retreat: packages with grounding‐line fan deposits and those without them. Lastly, in an effort to fill the gap between the middle Miocene and Plio‐Pleistocene climate histories of Antarctica, comparison of the AND‐1B Upper Miocene interval with the obliquity curve reveals one glacial–interglacial cycle and identifies erosion surfaces along which significant time may be missing.

From glacial erosion to basin overfill: a 240 m-thick overdeepening–fill sequence in Bern, Switzerland

“…The description followed a modified template of Krüger and Kjaer (1999) for deposits in glacial environments. We then followed state-ofthe-art approaches to characterize and interpret the sedimentological observations (e.g., Rose and Menzies, 2002;Buechi et al, 2017;Rosenblume and Powell, 2019;Sutherland et al, 2019). Accordingly, each sediment bed was first assigned to a lithofacies based on upper and lower bed contacts, the bed thickness, the grain size, the clast shape, and the sedimentary structures.…”

“…On the global scale, it was recognized that the peri-M. A. Schwenk et al: Successful drilling into the Quaternary sediment infill of the overdeepened Aare Valley odicity of glacial cycles increased from 41 to 100 ka, probably due to an increased eccentricity forcing (e.g., Ruddiman et al, 1986;Lisiecki, 2010) during the Middle Pleistocene climatic Transition (MPT, 1250-700 ka; Clark et al, 2006). Studies of the topographic evolution in the Central Swiss Alps suggest that glacial valley erosion started to increase during the MPT (Haeuselmann et al, 2007b;Valla et al, 2011).…”

Chronology and Sedimentary Processes in the Western Ross Sea, Antarctica since the Last Glacial Period

“…Climatic changes in the Southern Ocean and Antarctica are critical in Earth's climate evolution [1][2][3][4][5][6] due to their unique geographical location, environmental processes, and climate characteristics [7][8][9]. The Ross Sea is the second largest bay in the Southern Ocean (72-77 • S, 160 • E-160 • W), and studies on sediments in this key region have attracted great attention in the past [10][11][12][13][14], such as sedimentary processes, ice-shelf dynamics, sea-ice variation, and oceanic currents [15][16][17][18][19][20][21]. For instance, integrating geophysical surveys and multiple cores in the Ross [35].…”