Fossil protists (Algae and testate protozoans) in the marine phanerozoic of western australia: A review through latitudinal change, climate extremes, and breakup of a supercontinent

Algae and testate protozoans in Western Australian Cambrian–Neogene marine deposits are reviewed in terms of their broad occurrence. Known groups include: organic-walled unicellular phytoplankton, mostly algae (acritarchs and dinoflagellates); calcareous unicellular algal phytoplankton (calcareous nannoplankton and calcareous dinoflagellate cysts); benthic calcareous macroalgae as well as the enigmatic Tubiphytes; testate protozoans, including Foraminifera and Radiolaria; and groups of uncertain affinity including calcareous tests of Calcitarcha, tuberitinids, Draffania, and possible Charophyta. A record of calpionellids from the uppermost Jurassic of the Canning Basin is discounted. In addition to the groups listed above, stromatolites and calcareous and organic-walled cyanobacteria are considered and chitinozoans are included in this discussion although their biological group affinities are uncertain. The stratigraphic and geographic distribution of these fossil groups depended mainly on: (1) major evolutionary events; (2) latitudinal position from warm low latitudes in the Northern Hemisphere during the Early Paleozoic, to cold high latitudes in the Southern Hemisphere during the Pennsylvanian and earliest Permian, and later to warmer mid southern latitudes; and (3) the nature of the sedimentary basins and the seas that inundated these regions during phases of breakup of the Gondwana supercontinent. The basins developed within the interior of East Gondwana during the Paleozoic to middle Mesozoic and then along a continental margin newly formed by the progressive north–south opening of the Indian Ocean from the Middle Jurassic to Early Cretaceous. These changes in ocean configuration led to a significant diversification of dinoflagellates, calcareous nannoplankton, and Foraminifera: all of which are important stratigraphic guide fossils in the Jurassic to Cretaceous strata.