GeoResources - Early Evolution of Life in the Proterozoic


	Early Evolution of Life in the Neoproterozoic
	Abstract





	Scientists Hartmut Jäger, GeoResources and University of Heidelberg Guy Spence, University of Heidelberg (now: University of Manchester) Thilo Bechstädt, GeoResources and University of Heidelberg

	Abstract Life on earth is known since the Archean, at least 3,5 billion years. Since the late 1960’s numerous studies indicated, that life developed from these oldest fossils and evolutionary lineages went on continuously throughout the Proterozoic. Diversity studies show a slow increase during the Palaeo- and Mesoproterozoic followed by a jump in diversity and evolution of microscopic but also macroscopic life in the Neoproterozoic. Detailed studies of the upper Neoproterozoic showed a strong decrease in diversity in the basal Ediacaran, linked to a widespread glaciation, but life went on continuously. This scenario was generally accepted until the theory of ‚Snowball Earth’ arose, questioning these continuous evolutionary lineages from the Proterozoic into the Cambrian. This theory proposed global glaciations in the Neoproterozoic leading to the break down of the life cycle in the oceans, followed by mass extinctions. Detailed studies of this interval (especially the ‘Marinoan’ glacial event) in recent years recorded this gap of life in the critical interval in the Neoproterozoic. Investigating mainly carbonate successions from pre- to post-glacial formations of the Ghaub glacial event in NE-Namibia (Otavi Mountain Land), we observed the first continuous record of life across the Neoproterozoic ‘Marinoan’ glacial event worldwide. The complex microbial association of benthic prokaryotes (cyanobacteria) and eukaryotes (green algae) as well as planktic eukaryotes (acritarchs, prasinophytes) essentially requires open oceans with an active hydrologic cycle, ice-free shelfs and access to the sea floor. This proves the continuous evolution of marine life during the proposed ‘Snowball Earth’ period. No mass extinction or severe crisis of marine life is observed, clearly contradicting the hypothesis of global glaciations with globally frozen oceans. To explain widely distributed low latitude glaciations coexisting with continuous life in the oceans a different scenario is needed – the Neoproterozoic Ice Patch Earth. The study of organic microbiota is currently expanded to a much longer succession from the pre-glacial Ghauss Fm to the top of the postglacial Maieberg Fm. The study of the postglacial Maieberg Fm may also enable the analysis of the recovery of life after the most widespread glaciation in earth history and the interaction of microbial and macrofossil evolution in the late Neoproterozoic.

	Presentations & Publications EUG General Assembly, Vienna, 2008 British Sedimentological Research Group, Annual Meeting, Aberdeen, 2006

	Funding Organizations German Research Fund (DFG) GeoResources, Heidelberg

GeoResources - Early Evolution of Life in the Proterozoic

Early Evolution of Life in the Neoproterozoic