Publications

The papers in this volume describe petrologic, structural, and geochemical studies related to geographic areas adjacent to and including the Salmon River suture zone. We therefore start this volume by defining and giving a general description of that suture zone. The western margin of the North American continent was the setting for complex terrane accretion and large-scale terrane...

The 2007 field trip of the Pacific Cell, Friends of the Pleistocene, visited features of the Quaternary geology and geomorphology of the Lake Manix basin in the Mojave Desert. This report is the guidebook for this trip and includes some discussion of relations observable along the road and at various field trip stops. The Mojave River originates in the San Bernardino Mountains and in...

Understanding ground-water flow in a karst aquifer benefits from a detailed conception of the three-dimensional (3D) geologic framework. Traditional two-dimensional products, such as geologic maps, cross-sections, and structure contour maps, convey a mental picture of the area but a stronger conceptualization can be achieved by constructing a digital 3D representation of the...

This five-year USGS project, funded by the National Cooperative Geologic Mapping Program, is using multidisciplinary approaches to reveal the surface and subsurface geologic architecture of two important Texas aquifers: (1) the Edwards aquifer that extends from south of Austin to west of San Antonio and (2) the southern part of the Trinity aquifer in the Texas Hill Country west and south...

This geologic map is based entirely on new mapping by Thompson and Machette, whereas the geophysical data and interpretations were supplied by Drenth. The map area includes most of San Pedro Mesa, a basalt covered mesa that is uplifted as a horst between the Southern Sangre de Cristo fault zone (on the west) and the San Luis fault zone on the east. The map also includes most of the...

This report presents data and describes the methodology for magnetic, geochemical, and textural measurements of sediment and bedrock samples collected along a transect across the Southwestern United States (fig. 1). The results presented here support a study that examines compositional variations of mineral dust deposited during the past few centuries in isolated natural traps spanning a...

Preface: This report was presented as an invited paper at the Fish & Wildlife Service Climate Forum held in Anchorage, Alaska on February 21-23, 2007. The purpose of the talk was to provide some examples of past climate changes that appear to have caused significant responses in Alaskan vegetation. These examples are based on interpretations of dated fossil assemblages (pollen, spores...

A 3-dimensional computer model of the Quaternary sequence stratigraphy in the Dominguez gap region of Long Beach, California has been developed to provide a robust chronostratigraphic framework for hydrologic and tectonic studies. The model consists of 13 layers within a 16.5 by 16.1 km (10.25 by 10 mile) square area and extends downward to an altitude of -900 meters (-2952.76 feet). Ten...

Mesas and buttes of the central Colorado Piedmont are composed of at least two distinct rock types, which differ in their cohesiveness and resistance to erosion. The lower parts of the exposed stratigraphic section are poorly cemented, Upper Cretaceous to Middle Eocene sandstones of the Dawson Formation. The caprocks are composed of one or more resistant formations of Late Eocene age...

Surface-exposure (10Be) ages have been obtained on boulders from three post-Pinedale end-moraine complexes in the Front Range, Colorado. Boulder rounding appears related to the cirque-to-moraine transport distance at each site with subrounded boulders being typical of the 2-km-long Chicago Lakes Glacier, subangular boulders being typical of the 1-km-long Butler Gulch Glacier, and angular...

No abstract available.

Many sediment records from the margins of the Californias (Alta and Baja) collected in water depths between 60 and 1200 m contain anoxic intervals (laminated sediments) that can be correlated with interstadial intervals as defined by the oxygen-isotope composition of Greenland ice (Dansgaard–Oeschger, D–O, cycles). These intervals include all or parts of Oxygen Isotope Stage 3 (OIS3; 60...