Testing the Snowball Earth Hypothesis
OCCI Funded Project: 2005
Collaborators:
Paul Hoffman (Harvard University)
Birger Schmitz (Lund University, Sweden)
Bodiselitsch et al. (2005, Science) reported concentration anomalies of
iridium, a tracer of extraterrestrial material, in basal layers of cap
dolomite formations that overlie glacial sediments deposited during the
Sturtian (~710 Ma) and Marinoan (~635 Ma) Neoproterozoic "Snowball
Earth" glaciations. They hypothesize that these Ir anomalies reflect
instantaneous deposition, during deglaciation, of cosmic dust that has
been stored for millions of years on the global ice cover. If correct,
this hypothesis lends support to the "hard" Snowball Earth hypothesis
(i.e., Earth frozen to the equator) instead of the "Slushball Earth"
hypothesis which allows for the existence of open water in the tropics.
With funding from WHOI's Ocean and Climate Change Institute we are
using a range of geochemical tracers (osmium isotopes, platinum group
element concentrations, helium isotopes and concentrations) to detect
the presence of extraterrestrial matter in Snowball Earth deposits. Our
field work in Namibia in August 2005 was aimed at recovering continuous
sections across the glacial-postglacial transition (see Fig. 1). Work
on correlative sections from Canada (Mackenzie Mountains) China and,
possibly, Brazil is planned for the coming year.
Originally published: January 1, 2005