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A Seismic - Sequence Stratigraphic And Paleo-Environmental Study Of The Windalia Radiolarite In The Basrrow Sub-Basin, North West Shelf.

Gardner, Justin GA

Honours Degree, 1991

University of Adelaide

Abstract

The Windalia Radiolarite is an Aptian - Earliest Albian facies that was deposited as two sequences and forms the basal part of the Gearle Siltstone in the Barrow-Dampier Sub-Basin. The first sequence, which is Early to Middle Aptian, consists of radiolarian-poor siltstones and claystones. The second sequence, deposited between the Middle Aptian and the Latest Aptian/Earliest Albian, contains radiolarian-rich claystones, argillaceous siltstones and sandstones, calcilutites and limestones.

The base of the Windalia Radiolarite is a Type-1 sequence boundary, known as the `KA' Unconformity, which generates a strong continuous trough on seismic sections. The top is defined by a semicontinuous/continuous trough that varies throughout the basin depending on the bounding lithologies.

The paleoenvironment varied markedly between the 2 sequences. The first sequence was deposited within a restricted marine setting with little oceanic circulation and less silica-rich waters, giving rise to few radiolarian blooms. Subsidence of the first sequence occurred across the continental shelf and to a lesser extent across the Barrow Trough. The second sequence was deposited in a more open marine setting, with an oceanic circulation that produced a silica-rich environment which permitted an increased incidence in radiolarian blooms. Subsidence was most active across the continental margin and on the down thrown side of the activated, listric Flinders Fault Zone.

Australian School of Petroleum
THE UNIVERSITY OF ADELAIDE

SA 5005 AUSTRALIA

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