Regional Structures of the Fitzroy Trough and Lennard Shelf

Abstract The oldest sediments on the Lennard Shelf were deposited during the Ordovician and are interpreted to have been deposited in an intra-cratonic depression (Brown et al., 1984). Unconformably overlying these rocks are Upper Devonian carbonate sequences which form rugged narrow ranges, and extend for approximately 350km in a northwest to southeasterly direction. The deposition of the Upper Devonian sedimentary rocks on the Lennard Shelf coincided with contemporaneous rifting in the Fitzroy Trough, which was the main centre of deposition and subsidence (Craig etal., 1984; Brown etal., 1984; Begg, 1987). Deposition declined on the Lennard Shelf during the middle Carboniferous, and strong uplift and erosion occurred during the middle to late Carboniferous. Terrestrial sediments of late Carboniferous to early Permian age were subsequently - deposited unconformably on the Devonian carbonate rocks.