July 2008 GEOLOGY and GSA Today media ...(including the early ancestors of humans....)

Date:6/20/2008

including the early ancestors of humans. The sediments exposed in the badlands of Wyoming are famous for their fossil remains of ancient mammals, such as the earliest primates and horses that inhabited the plains of North America. The sediments include spectacularly red, orange, and purple color-banded soils that extend for kilometers throughout the landscape of Wyoming. The nature of these soils, however, has always been a matter of debate. Abdul Aziz et al. study the color records of these ancient soils, and show in this paper that the color banding was caused by cyclic climate changes. These climate changes are provoked by Earth's precession cycle of 21,000 years, which influences the distribution of solar energy on Earth's surface. Similar cycles are associated with glacial-interglacial cycles. The discovery of climate cycles in the sedimentary deposits in Wyoming is essential for several lines of research. For the first time, such cycles are shown to have influenced soil formation. These regular 21,000-year cycles provide an unparalleled time control for the sediments in Wyoming, enabling paleontologists to study the rate of mammal (including primate) evolution during the PETM and the long-term greenhouse phase in Earth's history.

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Vertical motions of the fjord regions of central East Greenland: Impact of glacial erosion, deposition, and isostasy

Sergei Medvedev et al., Physics of Geological Processes, University of Oslo, P.O. Box 1048, Blindern, 0316 Oslo, Norway. Pages 539-542.

Plate tectonics has successfully attributed many uplifts around the world to tectonic collisions. However, the vertical motions of the fjord regions of East Greenland cannot be explained by this mechanism because they occur at a time of regional tectonic quietness. Why are 100 to 200 million-year-old marine sedimentary rocks now located up to 1.2 km above sea level? Medvedev et al. address this long-standing enigma by analyzing field data and
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Contact: Christa Stratton cstratton@geosociety.org 303-357-1093 Geological Society of America Source:Eurekalert

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