Publication Name: The Sedimentary Basins of WA
Authors: A.N. Bint and N.G. Marshall
Publication Volume: 1
Date Published: July 1994
Number of Pages: 23
Reference Type: Book Section
Abstract:
Detailed palynological analysis of rich dinoflagellate assemblages from the upper Tithonian Angel Formation of the Wanaea - Cossack area has resulted in definition of a high resolution biostratigraphy. Nine dinoflagellate subzones are recognised within the Pseudoceratium iehiense Zone and upper part of the Dingodinium jurassicum Zone of Helby et al. (1987). The subzones are defined by first and last appearances of key species andare further characterised by species acmes. The total section is less than 300 m thick and is thought to span of the order of two million years. Subzone thicknesses vary from less than five metres to some 40 m and average
subzone duration is less than half a million years. The subzones enable more reliable correlation of the laterally
variable sandstone and siltstone sequences encountered, and have the potential to be more widely applicable in the sub-basin and elsewhere on the North West Shelf.
Over 150 dinoflagellate species are present in the Wanaea - Cossack reservoir sequence, more than half of which are undescribed. About thirty species possess criteria suitable for zonal subdivision. Those criteria are: 1) restricted range within the sequence together with persistent occurrence throughout their range; or 2) distinctive abundance spikes. Nine subzones have been labelled, in ascending order, the Belodinium nereidis,
Dissimulidinium sp. B, Egmontodinium sp. A, Perisseiasphaeridium inusitatum, Imbatodinium kondratjevii, Biorbifera sp. A, Dissimulidinium sp. A, Broomea simplex, and Clathroctenocystis calabaza subzones.