Organic-walled microfossils from the Early Cambrian of South Australia

Microfossils which are hollow, possess a two-layered vesicle wall, and occur as single elements or, more rarely, as compound forms, have been recovered from the Early Cambrian Heatherdale Shale, on the Fleurieu Peninsula, South Australia. The microfossils, which range in size from 4 to 14.5 μm, are informally and tentatively assigned to the genus Sphaerocongregus Moorman 1974. Superficially they resemble forms assigned to Pyritosphaera Love 1958 and its probable junior synonym, Bavlinella Shepeleva 1962. Topotypes of these genera, however, have yet to be studied using SEM techniques, and their morphologic details remain uncertain. The organic composition of the present microfossils is supported by energy-dispersive X-ray analyses. Samples of the Heatherdale Shale were also analysed using pyrolysis techniques; the organic matter is, however, over-mature with respect to petroleum generation, and no geochemical assessment of original kerogen type is possible.

[1]  G. Vidal,et al.  Late Proterozoic Brioverian microfossils from France: taxonomic affinity and implications of plankton productivity , 1983, Nature.

[2]  P. Cook.  THE CAMBRIAN PALAEOGEOGRAPHY OF AUSTRALIA AND OPPORTUNITIES FOR PETROLEUM EXPLORATION , 1982 .

[3]  D. McKirdy,et al.  Comparative Analysis of Stromatolitic and Other Microbial Kerogens by Pyrolysis-Hydrogenation-Gas Chromatography (PHGC) , 1980 .

[4]  M. Walter,et al.  Early Cambrian and latest Proterozoic stratigraphy, Desert Syncline, southern Georgina Basin , 1979 .

[5]  J. Schopf,et al.  Late Precambrian microfossils from Brioverian cherts and limestones of Brittany and Normandy, France , 1978, Nature.

[6]  M. Muir.  Late Precambrian Microfossils , 1977, Geological Magazine.

[7]  J. Oehler.  Microflora of the H.Y.C. Pyritic Shale Member of the Barney Creek Formation (McArthur Group), middle Proterozoic of northern Australia , 1977 .

[8]  D. McKirdy,et al.  Metamorphic Alteration of Carbon Isotopic Composition in Ancient Sedimentary Organic Matter: New Evidence from Australia and South Africa , 1974 .

[9]  M. Moorman,et al.  Microbiota of the late Proterozoic Hector Formation, Southwestern Alberta, Canada , 1974 .

[10]  E. R. Wicander,et al.  Microorganisms from the Kalkberg Limestone (lower Devonian) of New York State , 1974 .

[11]  P. D. Fleming,et al.  A synthesis of folding and metamorphism in the Mt Lofty Ranges, South Australia , 1968 .

[12]  L. G. Love.  Mircro-organisms and the presence of syngenetic pyrite , 1957, Quarterly Journal of the Geological Society of London.