Results from this study by M. Elrick and colleagues suggest that 10 million years before the well-documented Latest Ordovician glaciation and mass extinction event, there were significant continental glaciers growing and melting and causing global sea levels to rise and fall on 104-105 year time scales. These high-frequency, climatically controlled sea-level changes resulted in the development of widespread subtropical sedimentary cycles and changes in the oxygen isotope values of marine apatite occurring within the cycles. These high-frequency climate and sea-level oscillations support the interpretation of a dynamic and prolonged Ordovician greenhouse to icehouse transition.
A high-resolution nonmarine record of an early Danian hyperthermal event, Boltysh crater, Ukraine
Iain Gilmour et al., Planetary and Space Sciences, Dept. of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK. Posted online ahead of print 16 May 2013; http://dx.doi.org/10.1130/G34292.1.
Lake sediments from the Boltysh meteorite impact crater in Ukraine record geochemical and pollen evidence for a brief period of global warming a short time after the boundary that marks the extinction of the dinosaurs. The 24-km-diameter Boltysh crater, which formed a few thousand years before its much larger and more famous cousin at Chicxulub, which is thought to be responsible for the mass extinction at the end of the Cretaceous, quickly filled with lake sediments. These sediments provide the first record on land of a brief period of warming and major perturbation of the carbon cycle previously found only in marine sediments. This indicates a global change in the Earth's climate. Plant pollens record a change in the flora around the crater that shows an increasingly warm and dry cli
|Contact: Christa Stratton|
Geological Society of America