December 22, 2014
The Snowmastodon Project
Quaternary Research special volume, edited by Jeff Pigati (GECSC) and Ian Miller.
The discovery of the Ziegler Reservoir fossil site near Snowmass Village, Colorado in October 2010 led to the recovery of bones belonging to an array of extinct Pleistocene animals, including mastodons, mammoths, deer, sloths, bison, horses, camels, salamanders and rodents. The world-class paleontological site also featured geologic evidence of climate conditions during the Last Interglacial Period. A special volume of Quaternary Research includes 14 articles about the site by scientists from the USGS, Denver Museum of Nature and Science, and academic institutions around the world. USGS scientists contributing to this volume include Tom Ager, Bruce Bryant, Paul Carrara, Harrison Gray, Jeff Honke, Shannon Mahan, Dan Muhs, Jim Paces, Jeff Pigati, Gary Skipp, Laura Strickland, and Bob Thompson.
December 17, 2014
Radiocarbon dating loess deposits in the Mississippi Valley using terrestrial gastropod shells (Polygyridae, Helicinidae, Discidae)
By Jeff Pigati (GECSC), Jack McGeehin, Dan Muhs (GECSC), David Grimley, and Jeff Nekola. Published in Aeolian Research.
Gastropod shells (mostly Succineidae) have been used to successfully date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are rarely found in loess deposits in the Mississippi Valley. This study was conducted to determine whether shells of gastropod taxa that are common to the Mississippi Valley could also provide reliable carbon-14 ages. The results show that, for most of the taxa studied, shell ages were accurate to within a few hundred years, which is acceptable for certain types of scientific research. The study also found that shells of the genus Mesodon gave ages that were up to several thousand years too old and should be avoided for dating whenever possible.
December 16, 2014
Quaternary geologic map of the north-central part of the Salinas River Valley and Arroyo Seco, Monterey County, California
By Emily Taylor and Don Sweetkind. USGS Scientific Investigations Map 3260.
The 1:24,000 and 1:50,000 scale maps presented in this report summarize the geology of the Arroyo Seco, a perennial drainage in the central Coast Range of California. The geology of the Arroyo Seco records a sequence of strath terraces which preserve an erosional and depositional history, controlled by both climate change and regional tectonics. Along with the two map sheets and pamphlet, this publication includes downloadable GIS files.