Abstract: Non-Marine Sequence Stratigraphy in the Sydney Basin, Australia

Ron Boyd, Claus Diessel, Murray Little

Unconformity bounded sequences may be generated by a number of mechanisms inducing eustatic cycles, tectonic processes, and climate change. All of these mechanisms may occur in non-marine lithosomes. Tectonic and climatic cycles affect the entire drainage basin, but eustatic effects diminish inland from the coast. By concentrating on situations experiencing only eustatic changes, a predictive framework can be developed for non-marine sequence stratigraphy. Falling sea levels produce incised valleys which are filled during the subsequent sea level rise, highstand and possibly following sea level cycles. The incised valley fill is divisible into three segments, dominated respectively by marine, estuarine, and non-marine processes. How do we subdivide and recognize the non-marine units?< P>

The Permian Newcastle-Tomago Coal Measures in the Sydney Basin, Eastern Australia can be subdivided using abundant volcanic ash intervals. Depositional environments and their proximity and relationship to marine strata here can be determined from coal properties such as reflectance, fluorescence, coal composition indices, sulphur and boron content. Interseam intervals can be categorised in terms of fluvial stacking patterns, depth of channel incision, bioturbated intervals, and lacustrine strata to determine relative accommodation space during deposition. Finally, conglomerate composition and paleocurrent patterns provide information on provenance and dispersal patterns, distinguishing between local (highstand) sources and a more regional trunk drainage (lowstand).

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994