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At least 595 records · Page 33Linked to original sources
USGS1976

Preliminary description and interpretation of cores and radiographs from Clear Lake, Lake County, California: Core 3

Clear Lake, California is located in the California Coast Ranges about 120 km north of San Francisco and is the largest freshwater lake wholly within California. The lake basin is tectonically controlled (Anderson, 1936; Brice, 1953; Sims and Rymer, 1974) and the area seismically active (Coffman and von Hake, 1973). Interest in this lake was stimulated by hypotheses developed from a study of sediments in Van Norman Reservoir after the 1971 San Fernando earthquake (Sims, 1973). During this study three zones of deformational structures were found in the 1 m-thick sequence of sediments exposed over about 2 km2 of the reservoir bottom. These zones were correlated with moderate earthquakes that shook the San Fernando area in 1930, 1952, and 1971. Results of this study, coupled with the experimental formation of deformational structures similar to those from Van Norman Reservoir, led to a search for similar structures in Pleistocene and Holocene lakes and lake sediments in other seismically active areas. Clear Lake, California was chosen specifically because of its location near the San Andreas fault and the San Francisco-Oakland urban complex, and the probability of obtaining an uninterrupted sediment record from the present into Pleistocene time. Eight 12 to 15 cm diameter continuous cores were taken from the lake sediments (fig. 1) as part of a study of earthquake induced structures in sediments and the tectonic framework of the Clear Lake basin. The eight cores range in length from 13.87 m to 115.21 m (Table 1).

California↗
USGS1976

Progress report on geology of the Edwards aquifer, San Antonio area, Texas, and preliminary interpretation of borehole geophysical and laboratory data on carbonate rocks

This report describes the geology and porosity of the rocks of the Edwards aquifer, with particular attention to the eastern half of the San Antonio area. The data were obtained from geologic and geophysical studies of nine cored test holes, from laboratory analyses of samples of the aquifer materials, and from recent stratigraphic studies by other investigators. The Georgetown Formation and the Edwards Group or their equivalent stratigraphic units are extensively exposed in central Texas and they occur in the subsurface throughout southern Texas. They consist of a complex sequence of carbonate rocks deposited during Early Cretaceous time under different depositional conditions. Within the study area, the thickness of the carbonate rocks ranges from less than 400 feet (122 m) in the eastern part of the area to more than 600 feet (183 m) in the southwestern part. The depositional environments significantly affected the texture and the composition of the sediments. The Maverick Basin in the southwestern part of the study area was a euxinic basin surrounded by a barrier rudistid reef. Fine-grained carbonates and some associated evaporites occur within this basin. The San Marcos Platform in the eastern part of the study area was intermittently submerged by a transgressing continental sea. Much of the sediments are extensively reworked and burrowed by marine organisms. Several thick sequences of dolomites, evaporites, and associated collapsed deposits occur on the San Marcos Platform. The carbonates of the San Marcos Platform are extensively dissolved within the fresh-water zone. Much of the dissolution is selective of beds containing evaporites or porous dolomites. The dominant structural feature of the study area is a broad homocline that extends from nearly flat-lying beds on the Edwards Plateau to steeply dipping beds of the deep subsurface of the Gulf Coastal Plain. The homocline is interrupted by the Balcones Fault Zone, which is a zone of normal faults that extend across the study area. The intensity and complexity of faulting increases eastward as part of a progression from gentle flexures in the southwestern part of the study area to a complex pattern of tilted fault blocks on the San Marcos Platform.

Texas↗
USGS1976

Hydrologic interpretation of geophysical data from the southeastern Hueco Bolson, El Paso, and Hudspeth Counties, Texas

Airborne-electromagnetic and earth-resistivity surveys were used to explore for fresh ground water in the Hueco Bolson southeast of El Paso, Texas. Aerial surveys were made along about 500 miles (800 km) of flight line, and 67 resistivity soundings were made along 110 miles (180 km) of profile. The surveys did not indicate the presence of any large bodies of fresh ground water, but several areas may be underlain by small to moderate amounts of fresh to slightly saline water. The material underlying the flood plain of the Rio Grande is predominantly clay or sand of low resistivity. Along a band on the mesa next to and parallel to the flood plain, more resistive material composed partly of deposits of an ancient river channel extends to depths of about 400 to 1,700 feet (120 to 520 m). Locally, the lower part of this more resistive material is saturated with fresh to slightly saline water. The largest body of fresh to slightly saline ground water detected in this study is between Fabens and Tornillo, Texas, mostly in the sandhill area between the flood plain and the mesa. Under assumed conditions, the total amount of water in storage may be as much as 400,000 to 800,000 acre-feet (500 million to 1 billion m ). The resistivity data indicate that the deep artesian zone southwest of Fabens extends from a depth of about 1,200 feet (365 m) to about 2,800 feet (855 m).

Open-File Report↗
USGS1976

Interpretation of Landsat imagery of the Tanacross quadrangle, Alaska

In this study of Landsat imagery for the Tanacross quadrangle, Alaska, two fundamentally different types of images were used: (1) a black and white, single band, Landsat mosaic of Alaska, constructed with images that are not computer-enhanced; and (2) various types of computer-enhanced Landsat images.

Alaska↗
USGS1977

Interpretation of Landsat images: Qatar (preliminary report)

The Emirate of Qatar is shown on this mosaic of two Landsat images. Before mosaicking, false-color composites of each of the two images were printed on Cibachrome material. Some of the surficial and bedrock units, as well as some cultural features, are easily detected on land.

Open-File Report↗
USGS1977

Interpretation of Landsat images: Oman

The part of northern Oman shown on this mosaic of two Landsat images extends from Ras al Hadd in the east to the village of Wudam Alwa on the coast of the Gulf of Oman. The mosaic consists of two Landsat images printed in false color on Cibachrome material. The three major physiographic provinces of northern Oman are readily distingui shed on the mosaic, through their peculiar tonal and textural characteristics: The coastal plain, known as the Batinah Coast , along t he Gulf of .Oman west-northwest of Muscat; the Oman Mountains; and the foothills in the southwestern part of the interior.

Open-File Report↗
USGS1977

Interpretation of Landsat images: Kuwait (preliminary report)

Two Landsat Images, 1153-06514 and 1153-06521, show all of Kuwait except the extreme western part. They were taken on December 23, 1972, only two days after the winter solstice. Sun elevation at that time is 30° which approaches the minimum value for Kuwait's latitude, a condition that enhances shadows and maximizes contrasts in a land of low relief and high desert reflectance. False-color composites of both images have been printed on Cibachrome material.

Open-File Report↗
USGS1977

Geologic interpretation of a radioactivity anomaly near the west fork of the Buckland River, western Alaska

A large part of western Alaska has been included in a uranium- thorium metallogenic province (Clark and others, 1974; Miller and Bunker, 1976; Miller, 1976) chiefly because of the occurrence of uraniferous plutonic rocks with local concentrations of uranium minerals. Recently, however, anomalous amounts of uranium and thorium have been found by the Geological Survey in volcanic and volcaniclastic rocks near the headwaters of the West Fork of the Buckland River in the central Candle quadrangle (fig. 1). This occurrence is apparently in a different geologic environment than previously noted uranium occurrences in western Alaska. An increase in radioactivity was noted in this general area and three airborne gamma-ray survey traverses, done as part of an ERDA-sponsored reconnaissance survey of western Alaska, cross the area (figs. 1, 2) and confirm the existence of a radioactivity anomaly (U.S. Energy Research and Development Administration, 1975, report GJO-1653).

Alaska↗