Stratigraphy and micropalaeontology of the upper cretaceous of Western Australia
The distribution, relationships, and stratigraphical significance of the microfaunas (mainly foraminifera) in the Upper Cretaceous deposits of Western Australia are discussed, and palaeogeography and palaeoecology considered.Formations deposited during the Cenomanian-Turonian are the Gearle Siltstone and Alinga Greensand and perhaps the Molecap Greensand. Among the foraminifera recorded are the stratigraphically restricted planktonic formsGlobotruncana (Praeglobotruncana)stephani subspp. andG. helvetica.The Gingin Chalk and the lower part of the Toolonga Calcilutite were deposited during the Santonian. These formations contain the crinoid generaMarsupites andUintacrinus, several species ofGlobotruncana andNeoflabellina, andBolivinoides strigillata. Santonian beds are known in sub-surface sections as far north as the area of the Warroora Anticline.The Toolonga Calcilutite extends up into the lower Campanian, andGlobotruncana arca appears in the fauna. The occurrence of Campanian beds in the Perth Basin cannot be proved; most of the Poison Hill Greensand may be of this age. On foraminiferal evidence, deposition of the Korojon Calcarenite began during the Campanian. Important species identified areGlobotruncana arca,Cibicides voltziana andBolivina incrassata.The upper beds of the Korojon Calcarenite and the Miria Marl are of Maestrichtian age. The Miria Marl contains the speciesGlobotruncana stuarti,G. citae andG. contusa. The upper beds of the Poison Hill Greensand may range into the Maestrichtian.