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.
December 15, 2014
DOI/GTN-P climate and active-layer data acquired in the National Petroleum Reserve-Alaska and the Arctic National Wildlife Refuge, 1998-2013
By Frank Urban and Gary Clow. USGS Data Series 892.
This online report provides an additional two years of air temperature, wind speed, wind direction, ground temperature, soil moisture, snow depth, rainfall, up- and downwelling shortwave radiation, and atmospheric pressure data to that previously published in USGS Data Series 812. In addition to presenting data, this report also describes monitoring, data collection, and quality control methodology. The data collection is ongoing and done in close collaboration with the Bureau of Land Management and the U.S. Fish and Wildlife Service.