Publications

The depth of the basin beneath Frenchman Flat is estimated using a gravity inversion method. Gamma-gamma density logs from two wells in Frenchman Flat constrained the density profiles used to create the gravity inversion model. Three initial models were considered using data from one well, then a final model is proposed based on new information from the second well. The preferred model...

This study examined thermal-infrared (TIR) image data acquired using the airborne Advanced Thematic Mapper (ATM) sensor in the afternoon of July 25th, 2000 over a portion of the Colorado River corridor to determine the capability of these 100-cm resolution data to address some biologic and cultural resource requirements for GCMRC. The requirements investigated included the mapping of...

The Permian Phosphoria Formation of the western U.S. includes one of the largest phosphate deposits in the world. Despite the economic significance of this formation, its fine-grained nature has discouraged detailed mineralogical characterization and quantitative studies. Recently, selenium and other potentially hazardous trace elements in mine wastes have drawn increased attention to...

This study, one in a series, reports bulk chemical and mineralogical compositions, as well as petrographic and outcrop descriptions of rocks collected from three measured outcrop sections of the Rex Chert member of the Phosphoria Formation in SE Idaho. The three measured sections were chosen from ten outcrops of Rex Chert that were described in the field. The Rex Chert overlies the Meade...

Reprocessing of seismic-reflection data reveals new images of upper- to middle-crustal structures beneath the Wabash Valley seismic zone, located north of the New Madrid seismic zone within the seismically active southern Illinois basin. Four intersecting deep seismic profiles (243 km total) indicate an anomalous, 5–10-km-wide zone of dipping reflections and diffractions below the...

The Western Earth Surface Processes Team (WESPT) of the U.S. Geological Survey (USGS) conducts geologic mapping and related topical earth-science studies in the Western United States. This work is focused on areas where modern geologic maps and associated earth-science data are needed to address key societal and environmental issues, such as ground-water quality, landslides and other...

This is a digital map database version of a previous printed geologic map, U.S. Geological Survey Open-File Report 92–179. The original paper map has been faithfully reproduced as a geologic map database for use in a GIS, and thus does not contain updated geologic information for the map area. This publication consists of three parts: 1. Documentation in the form of a this publication's...

Artificial neural networks are a group of mathematical methods that attempt to mimic some of the processes in the human mind. Although the foundations for these ideas were laid as early as 1943 (McCulloch and Pitts, 1943), it wasn't until 1986 (Rumelhart and McClelland, 1986; Masters, 1995) that applications to practical problems became possible. It is the acknowledged superiority of the...

An inventory of more than 1,600 world phosphate mines, deposits, and occurrences was compiled from smaller data sets collected as part of multiple research efforts by Carlotta Chernoff, University of Arizona, and Greta Orris, U.S. Geological Survey. These data have been utilized during studies of black shale depositional environments and to construct phosphate deposit models. The...

This is a digital map database version of a previous U.S. Geological Survey Open-File Report, OF92-182. It contains 3 Arc/Info formatted coverages, distributed in Arc Interchange format, a plottable map representation of the database at 1:24,000 scale in Postscript and Adobe PDF formats, and the original map explanation pamphlet in text, Postscript, and Adobe PDF formats.

Mineral deposit models are important in exploration planning and quantitative resource assessments for two reasons: (1) grades and tonnages among deposit types are significantly different, and (2) many types occur in different geologic settings that can be identified from geologic maps. Mineral deposit models are the keystone in combining the diverse geoscience information on geology...

This is a digital map database version of a previous printed geologic map, U.S. Geological Survey Open-File Report 92–183. The original paper map has been faithfully reproduced as a geologic map database for use in a GIS, and thus does not contain updated geologic information for the map area. This publication consists of three parts: 1. Documentation in the form of a this publication's...