School of GeoSciences

School of GeoSciences

Palaeomagnetism at the University of Edinburgh



www.palaeomag.com


This research group is funded by the EC Marie Curie Excellence Team action (Framework 6). Research aims are to investigate the question of low latitude glaciations in the Neoproterozoic.

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Members of the group:

Dr Jenny Tait
Dr Sergei Pisarevsky
Dr Graeme Nicoll
Dr Chris Rowan
Gijs Straathof

Past member:
Dr Clare Peters

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Snowball Earth: Equatorial Glaciations in the Neoproterozoic

Evidence from the Neoproterozoic geological record shows that at least three times in the Earths history marine glaciers reached equatorial latitudes, the latest of which in the Ediacaran may have provided the trigger for the Cambrian explosion of multicellular life forms. The most popular model to explain this climatic phenomenon is the Snowball Earth hypothesis which necessitates dramatic and catastrophic changes in global climatic, hydological and biological systems. Counter models involve either major changes in the Earths orbital axis, the High Obliquity Model which would require a gigantic meteorite impact in order to change the Earths obliquity to its present day value, or refutation that the sedimentary sequences are truly glaciomarine or that they were deposited at the equator - the Zipper-Rift model.

Pivotal to all models and to all climate models is the position of the continents prior to and during glaciation. Thus palaeomagnetism, being the most reliable technique available for positioning Neoproterozoic continents, is crucial to our understanding of the processes involved. Unfortunately, only very few reliable data are available and the position of most continents remains unconstrained for the time in question.

Geochemistry is also a vital part of this research. The age constraints for many of the glacial/carbonate sequences identified in the different cratons are extremely poor. Provenance studies are also important in understanding palaeogeographic relationships given the absence of palaeobiogeographic indicators. Also, a characteristic chemostratigraphic signal has been identified in many of the carbonate sections studied so far, implying quite particular oceanic conditions. Critical to our understanding of the Neoproterozoic and apparent low latitude glaciations, therefore, is the age and timing of these glacial/carbonate sequences, establishing the global isotopic charactersitics of the oceans at the time of deposition as well as understanding the Carbon cycle.

In a multidisciplinary approach, the aims of this project are to use palaeomagnetism in conjunction with geochemistry and geology to determine Neoproterozoic palaeogeography, the sedimentological and chemostratigraphic characteristics of the sequences deposited during these controversial periods, and provide time constraints for the sequences identified on a number of different cratons.