High concentrations of greenhouse gases and polar stratospheric clouds: A possible solution to high-latitude faunal migration at the latest Paleocene thermal maximum. Robert B. Peters and Lisa Cirbus Sloan
This paper documents a climate modeling study that investigates the role of high concentrations of atmospheric methane and polar clouds in explaining the high-latitude faunal migrations that occurred approximately 55 million years ago. The model results indicate that such high-latitude migrations, which would have required year-round above-freezing conditions for many years, may have been facilitated by high atmospheric methane concentrations and the presence of polar stratospheric clouds.
Have distal impact ejecta changed through geologic time? Bruce M. Simonson and Paul Harnik
The vast majority of impact craters on the moon are over 2.5 billion years old. Craters must have been forming on Earths surface at the same time (a period known as the Archean), but almost all of them have long since been eradicated by erosion and tectonic deformation. Nevertheless, a record of impacts has been discovered among Archean sedimentary strata in the form of thin layers rich in distinctive sand-size spherules of former silicate melt. Around ten spherule-rich layers that range in age from ca. 2.5 to 3.4 billion years old have now been identified. All of them appear to be reworked ejecta from large impacts, and they have much in common with younger layers, especially the most extensive ejecta layer known, the Cretaceous-Tertiary boundary layer. However, there are also c
Contact: Ann Cairns
303-447-2020 ext 156
Geological Society of America