Late Cenozoic (13-0 Myr) Glacimarine Sedimentology, Facies Analysis, and Sequence Stratigraphy from the Western Ross Embayment, Antarctica: Implications for the Variability of the Antarctic Ice Sheets

• Main Author: McKay, Robert Murray
• Other Authors: Naish, Timothy, Barrett, Peter
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Victoria University of Wellington 2008
• Subjects: Sedimentology; Sedimentary model; Facies (Geology); Sequence stratigraphy; Antarctic geologic analysis; Antarctic; McMurdo Ice Shelf; McMurdo Sound; Ross Ice Shelf; Ross Island; Ross Sea; The Antarctic; Antarc*; Antarctica; Ice Sheet; Ice Shelf
• Online Access: http://researcharchive.vuw.ac.nz/handle/10063/493

Sedimentary processes related to oscillations of the marine-based sector of Antarctic Ice Sheet (AIS) in the Ross Embayment over the past 13 Myr are examined at various timescales from stratigraphic records of glacial advance and retreat obtained from the McMurdo Sound region. An initial sedimentary model was developed from short (<2 m) sediment cores collected from beneath the present-day McMurdo Ice Shelf and seasonally open water in the Ross Island region. These cores document sedimentary processes associated with subglacial, ice shelf and open marine environments since the Last Glacial Maximum (LGM) in the Ross Sea Embayment. A radiocarbon chronology from these short cores implies that lift-off of grounded ice in the 900 m-deep marine basins surrounding Ross Island occurred by ~10,100 14C yr BP. Following lift-off, the ice shelf calving line retreated toward its present position. By ~8,900 14C yr BP, seasonally open marine conditions extended as far south as Ross Island. Glacial retreat was rapid and preceded the timing of Meltwater Pulse 1B. Since 8,900 14C yr BP, the calving line of the Ross Ice Shelf has remained pinned to Ross Island despite warmer-than-present temperatures during the mid-Holocene. Depositional models developed for the LGM to recent sediments were then applied to the interpretation of the 1284-m-long ANDRILL McMurdo Ice Shelf core (AND-1B) to documenting oscillations of the AIS in the Ross Embayment over the past 13 Myr. A sequence stratigraphic framework for grounding-line fluctuations of under a variety of glacial regimes, with three distinct types of glacimarine cycle (sequence motif) identified. Motif 1 (Pleistocene and Mid to early Late Miocene) is dominated by thick sub-glacial diamictite, deposited during glacial advance, with occasional thin interbeds of sparsely- to non-fossiliferous mudstone that marks an ice shelf setting during interglacial maxima. Motif 2 (Pliocene) comprises subglacial to glacimarine diamictite overlain by thin, proglacial deposits and capped with ...