STABLE ISOTOPIC EVIDENCE FOR NEOPROTEROZOIC LIFE ON LAND

Stable isotopic composition of nodules in calcareous paleosols and of marine limestones altered below paleokarst preserves photosynthetic and paleoclimatic signals well back into the Precambrian. Here we present new data on stable isotopic composition of Cambrian and Ediacaran paleosol and paleokarst carbonate from the Flinders Ranges, South Australia, along with a global compilation of geologically younger and older carbonate isotope data. Oxygen isotopic composition of paleosols and paleokarst reveal paleoclimatic fluctuations: particularly paleotemperature. Carbon isotopic composition of paleosols and paleokarst are evidence of at least two isotopically distinct communities of life on land during the Cambrian and Neoproterozoic (back at least 850 Ma). Both communities were biological soil crusts of limited stature and biomass, because isotopic differentiation observed falls short of that seen in paleosols and paleokarst after the advent of Ordovician liverworts, Silurian vascular plants, and Devonian woodlands.