THE TIMOR SEA-SAHUL SHELF AREA

Abstract

Sediments of a total thickness estimated as exceeding 24,000 feet have accumulated in the Timor Sea-Sahul Shelf area. Onshore, the only sediments of significant thickness recorded from outcrops and wells have been Paleozoic; the main oil prospects, however, will be located in Mesozoic and Cenozoic sediments, which are expected to be of the Carnarvon Basin type. The Devonian and Carboniferous sediments probably occupy sub-basins which have evolved as the result of subsidence of a postulated north-eastern extension of the Kimberley Block, between fault zones associated with the "Halls Creek mobile zone".

Three geophysical horizons have been correlated respectively with the top of the Lower Permian, the Cretaceous (probably Cenomanian), and probably the Tertiary. The structural pattern is generally unchanged through the Paleozoic into the Mesozoic, differences in the pattern becoming apparent in the Cretaceous. The present-day structure of the Sahul Shelf Basin evolved early in the Tertiary.

In the Basin, faulting and subsidence only have been recognised, with no evidence of severe folding or overthrusting. Anomalous structures occur (sometimes domal in pattern) due to intrusions along fault zones.