The Role of Eustasy in the Development of a Regional Shallowing Event in a Tectonically Active Basin: Fossil Bluff Group (Jurassic—Cretaceous), Alexander Island, Antarctica

  1. David I. M. Macdonald
  1. P. J. Butterworth

Published Online: 14 APR 2009

DOI: 10.1002/9781444303896.ch18

Sedimentation, Tectonics and Eustasy: Sea-Level Changes at Active Margins

Sedimentation, Tectonics and Eustasy: Sea-Level Changes at Active Margins

How to Cite

Butterworth, P. J. (1991) The Role of Eustasy in the Development of a Regional Shallowing Event in a Tectonically Active Basin: Fossil Bluff Group (Jurassic—Cretaceous), Alexander Island, Antarctica, in Sedimentation, Tectonics and Eustasy: Sea-Level Changes at Active Margins (ed D. I. M. Macdonald), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303896.ch18

Editor Information

  1. British Antarctic Survey, Cambridge, UK

Author Information

  1. British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 OET, UK

  1. The Robertson Group plc, Llandudno, Gwynedd, LL30 1SA, UK

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 13 JUN 1991

ISBN Information

Print ISBN: 9780632030170

Online ISBN: 9781444303896

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Keywords:

  • role of eustasy in development of regional shallowing event in tectonically active basin - fossil Bluff Group (Jurassic—Cretaceous), Alexander Island, Antarctica;
  • Fossil Bluff Group (FBG) of eastern Alexander Island;
  • basin evolution - FBG basin-fill sequence as series of time slices;
  • submarine-fan-shelf transition;
  • Valanginian—Albian - Jupiter Glacier Member - overlain by Valanginian—Aptian;
  • dramatic facies shift - storm dominated shelf sandstones (Jupiter Glacier Member) overlying submarine fan conglomerates of late Berriasian age

Summary

A 7 km thick, Kimmeridgian–Albian fore-arc basin succession, unconformably overlying an accretionary complex, is exposed on the east coast of Alexander Island adjacent to the Antarctic Peninsula. The basin fill represents a single regressive megasequence, strongly controlled by active faulting along the arc-basin margin. This regressive megasequence comprises a large-scale (minimum 440 m thick) slope-collapse deposit overlain by a 2.2 km thick Tithonian–Berriasian sequence of proximal submarine fan deposits that record three tectonic pulses of coarse clastic sediment input. Intra-basinal synsedimentary tectonism was the primary control on the development of the overlying, 1 km thick, slope mudstone sequence (Valanginian – Aptian). The basin fill is capped by an Aptian – Albian shallow-marine and terrestrial sandstone sequence, 3.5 km thick, which is probably diachronous across the basin. A clearly defined petrographic arc-unroofing trend is documented by a shift in conglomerate clast composition and sandstone petrofacies, and indicates a substantial episode of arc uplift and dissection during Tithonian and Berriasian times.

This overall, 7 km thick, regressive megasequence is punctuated during the late Berriasian by a well-exposed, abrupt facies from inner fan channel, deep marine conglomerates to a 70–90 m thick, shallow marine, storm-dominated shelf sandstone unit. This synchronous, basin-wide event is interpreted as reflecting a sedimentary response, at least in part, to a short-term eustatically controlled sea-level fall. This event correlates with a third-order short-term sea-level fall from the Exxon coastal onlap cycle chart.