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ABSTRACT: Sequence Stratigraphy of Glacial Sediments in an Intracratonic Basin -- Grant Group, Canning Basin, Western Australia

O'BRIEN*, PHIL. E., JOEN F. LINDSAY, PETER N. SOUTHGATE, M. JIM JACKSON, JOHN M. RENNARD, and MIRE J. SEXTON, Bureau of Mineral Resources, Canberra, Australian Capital Territory, Australia

The Canning basin in northwest Australia contains one of a number of hydrocarbon-bearing Permian-Carboniferous glacial successions scattered across Gondwana. Up to 2.5 km of sediment derived from Permian ice sheets on adjacent Precambrian blocks was trapped in the Fitzroy Trough in the northeast portion of the basin. During relative sea-level lowstands, regionally extensive erosion surfaces with relief of several hundred meters developed. Lowstand and early transgressive deposits consist of sandstone and finer-grained infillings of topographic lows on these erosion surfaces. Later transgressive deposits consist of glaciomarine mudstones and diamictites, subaqueous outwash fans and deltaic deposits, composed mostly of sandstone. Highstand deposits consist of aggrading sandy fluvial bra dplain deposits if deposited during interglacial epochs. If the relative highstand was caused by isostatic loading of the basin by the ice sheet, highstand systems tracts comprise glaciomarine diamictites, mudstones and subaqueous outwash.

Potential reservoir sandstones are present in all systems tracts because englacial and proglacial lake outbursts deposited extensive sheets of massive, relatively well-sorted sandstone. Seals are provided by transgressive and highstand shales and diamictites, but these may be breached by the incision of lowstand erosion surfaces.


AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)