45257-AC8
Cambrian Life on Land?
This proposal investigated possible evidence for life on land in the middle Cambrian fossils soils (paleosols) of the Moodlatana Formation near Wirrealpa in the Flinders Ranges of South Australia. One season of fieldwork was completed with graduate student Christine Metzger in July 2006, then another field season alone in June 2007 to tidy up details. Rock specimens were sent home by sea-mail for laboratory analysis, and all have now arrived safely in Eugene. Graduate students Lisa Emerson and Kathryn Watts were employed by the grant for laboratory analyses of samples during fall term 2007, and Christine Metzger during Spring 2008. Undergraduate Cole Smith was employed under work-study agreement for the academic year 2007-2008. Petrographic thin sections, major element chemical analyses, carbon and oxygen isotopic analyses and x-ray diffraction traces are the principal methods used for their study. One long paper on the paleosols has been published by the Australian Journal of Earth Sciences, others have been submitted to Palaeontology, Nature, Science, and Geology. The most surprising aspect of these very ancient soils was the drab surfaces of the profiles like those of geologically younger paleosols. Drab-mottles in the upper part of middle Cambrian paleosols from the Moodlatana Formation in Ten Mile Creek, near Wirrealpa, South Australia, have a distinctive correlation with a central filament diameter like that of drab-haloed root traces in geologically younger paleosols. Similarly the drab mottles may have formed by early burial gleization of remnant organic matter. The Cambrian mottles are smaller than drab-haloed root traces and interpreted as remains of biological soil crusts. Varied morphologies observed may represent the earliest known terrestrial lichens, truffles and lichens. This discovery of substantial biomass in formerly well drained soils has implications for understanding Cambrian carbon cycle and paleobiology.
