Publication Name: The North West Shelf Australia
Authors: A.N. Bint and R. Helby
Date Published: July 1988
Number of Pages: 19
Reference Type: Book Section
Abstract:
The Upper Triassic sequence penetrated on the Rankin Trend consists of the upper part of the Mungaroo Formation and the Brigadier Formation. Palynological and lithofacies subdivision of the sequence have provided a framework for recognition of seven palynofacies which are defined by a distinctive spore, pollen, and icroplankton assemblage, in association with the lithology. They are named the swamp, swamp margin, channel, floodplain, oxidised floodplain, marginal marine, and marine palynofacies, referring to the depositional environment each is interpreted to represent. These palynofacies occur through a delta plain to shallow marine sequence, elucidating aspects of the depositional history. The rock record exhibits prolific delta progradation over an initially nearshore marine environment, followed by a terminal transgressive phase back to shallow marine sedimentation. Superimposed upon this, are pulses of increased coarse sediment supply, producing analternation of predominantly sandstone versus mainly claystone packages. The palynofacies tracts are laterally
extensive, attesting to regional stability and uniform development within this portion of a large delta system.