Ron Boyd¹, Jennifer Wadsworth¹, Jason Roberts¹, Peter Roy²

(1) University of Newcastle, Newcastle, NSW, Australia
(2) University of Sydney, Sydney, Australia

ABSTRACT: Shelf Sand Bodies From SE Australia: High Resolution Quaternary Analogs For Reservoir Models

The Quaternary southeast margin of Australia developed under low accommodation and high wave energy conditions. A high resolution data set acquired in this region has enabled us to develop a detailed understanding of shelf and shoreline sand body development. From four field sites spread over 1000 km along the NSW margin we have acquired over 2000 line km of high resolution boomer seismic reflection data to basement, combined with over 100 vibracores up to 6m in length. The cores have been extensively dated using radiocarbon, thermoluminescence and amino acid techniques and illustrate a complex geometry of amalgamated units with different ages, and containing numerous internal reservoir baffles and barriers.

The modern coastline and inner shelf consist of a 30km wide, laterally stacked composite of barrier and shoreface deposits, up to 15 m thick, and accumulated over at least the last five interglacial highstands. On the shelf, transgressions produced deep reworking of former highstand shorelines by wave ravinement processes, tidal inlet excavation and tidal delta infilling. On steeper shelf gradients off shoreline promontories, detached progradational shelf sand bodies accumulated during transgression. Our detailed chronostratigraphic control indicates that most sand accumulations in this low accommodation setting are composite features containing both transgressive and regressive components. Valleys provide a further level of complexity, as they preferentially incise and fill highstand shoreface deposits. Modern river valleys do not connect seaward with submarine canyons and do not appear to have supplied sediments to lowstand deltas, canyons or fans.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado