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

• Published in: Sedimentology
• Main Authors: Rosenblume, Justin A., Powell, Ross D.
• Other Authors: Eyles, Nick, GSA Graduate Student Research, Northern Illinois University Goldich Fund
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Antarctic; Ross Ice Shelf; Ross Sea; Svalbard; The Antarctic; Antarc*; Antarctica; Ice Sheet; Ice Shelf; Iceberg*
• Online Access: http://dx.doi.org/10.1111/sed.12592; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fsed.12592; https://onlinelibrary.wiley.com/doi/pdf/10.1111/sed.12592; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/sed.12592

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.