OFR 151.pdf - CRC LEME

6.4 Time Slice K-3. Cenomanian [97.5-91 Ma]
Zones: Appendicisporites distocarinatus Zone
Xenascus asperatus to Palaeohystrichophora infusorioides Zone
Figure 6: Cenomanian (96 Ma) palaeogeography (from Veevers et al. 1991)
6.4.1 Palaeogeography
During the latest Albian [99 Ma], Chilean-type subduction of the Pacific Plate beneath East
Gondwana changed to Mariana-type (sinistral oblique) subduction, due to the onset of seafloor
spreading between Australia and Antarctica, and back-arc spreading in the South-west
Pacific (Veevers 1991a, 1991b, 1999). Tectono-stratigraphic changes associated with this
‘swerve’ led to uplift of the Eastern Highlands and forced the (asymmetric) drainage of much
of the continent into what is now the Bight region (Figure 6). During the Early Cenomanian,
marine regression left freshwater lakes and swamps in the Eromanga Basin although a
shallow sea remained present in the Gulf of Carpentaria. Alluvial sequences accumulated in
the Eromanga Basin include the Winton Formation (Dettmann et al. 1992). Continued
subsidence along the palaeo-northwestern and western margins resulted in local marine
transgression of the Carnarvon and Perth Basins. The Indian Ocean was sufficiently wide to
have developed oceanic circulation, leading to carbonate deposition on the North West Shelf.
72