Reconnaissance Survey of Upper Neogene Strata in the Bouse Formation, Hualapai Limestone, and Lower Gila River Trough, Western Arizona and Directly Adjacent Southeastern California

Neogene sediments and sedimentary rocks are exposed at the Earth's surface or buried in the subsurface over much of western Arizona. The Bouse Formation in particular is exposed over a large area of rapid population growth and contains calcareous sedimentary strata. The Bouse Formation has been considered to be marine on the basis of paleontological studies, and consequently has not been the target of uranium surveys because marine calcareous strata generally do not contain elevated concentrations of uranium. Recent strontium isotopic analyses support a non-marine origin, however (Spencer and Patchett, unpublished manuscript submitted to GSA Bulletin), and prompted are-evaluation of the Bouse Formation and related strata as potential sources of hazardous radon gas. This report presents several sets of data, as follows: (1) in situ measurements of uranium in the Bouse Formation and Hualapai Limestone (Harris), (2) oxygen and carbon isotopic analyses oftwo barnacle fragments from the Bouse Formation that were done to assess its marine versus non-marine character (Dettman), (3) strontium isotopic analyses of two subsurface samples of gypsum from water wells in the lower Gila River trough that were done to assess the marine versus non-marine character of these sediments and to assess any relation to the Bouse Formation (Patchett), and (4) logs of water wells in the lower Gila River trough that were recorded to assess the potential subsurface extent of calcareous sediments (Harris), Our general conclusion is that the Bouse Formation and Hualapai Limestone are both non-marine and both contain elevated concentrations of uranium. Limestone and marl ,like that inthe Bouse Formation and Hualapai Limestone was not, however, recognized in the subsurface in the lower Gila River trough.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu