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At least 577 records · Page 32Linked to original sources
USGS1968

Infrared survey of the Pisgah Crater area, San Bernardino County, California - a geologic interpretation

The infrared survey of the Pisgah Crater Area, San Bernardino County, California was primarily undertaken to establish parameters by which rock types, structures, and textures peculiar to this locale could be recognized or differentiated. A secondary purpose was to provide an adequate evaluation and calibration of airborne and ground-based instruments used in the survey. Pisgah Crater and its vicinity was chosen as one of the fundamental test sites for the NASA remote sensing program because of its relatively fresh basaltic flows and pyroclastics. Its typical exposure of basalt also made it a possible lunar analogue. A fundamental test site for the purpose of the program is defined as a readily accessible area for which the topography, geology, hydrology, soils, vegetation and other features are relatively well known. All remote sensor instrument teams, i.e. infrared, radar, microwave, and photography, were obligated to use the fundamental test sites for instrument evaluation and to establish terrain identification procedures. Pisgah Crater, nearby Sunshine Cone, and their associated lava flows are in the southern Mojave Desert about 40 miles east-southeast of Barstow, California. (See fig. 1.) U. S. Highway 66 skirts .the northern part of the area and provides access via asphalt-paved and dirt roads to the Crater and to the perimeters of the flows. Pisgah Crater, which is a pumiceous cone, is owned and occasionally quarried by the Atchison, Topeka and Santa Fe Railroad. The remaining part of the area to the south is within the boundary of the Marine Corps Base, Twentynine Palms, California and is currently being used as a gunnery, and bombing range. The proximate area to east, west, and north of Pisgah Crater is public domain. Originally, an area totaling 10 square miles was outlined for detailed study. (See plate 1.) This included an 8 mile long strip extending south- east from and including Pisgah Crater to Lavic Dry Lake, and a 2 mile strip aligned to include a portion of the Sunshine lava flow and the dry lake. Additional aerial infrared imagery of the Sunshine and Pisgah flows along the Pisgah fault proved so interesting and informative that this area is included in the discussion. Infrared surveys were flown February ii through 13, 1965 and August 5 and 9, 1966. The initial survey was flown by the NASA personnel aboard the NASA 926 Convair 240 aircraft. Because of technical problems with the infrared scanners (4.5-5.5 and 8-14 micron bands) and with certain ground instruments, most of the imagery and ground temperature data obtained during the initial survey period was of little value. However, excellent infrared imagery in the 8-14 micron (?) region of the spectrum was acquired by the Geological Survey during the August 1966 survey. The scanner was mounted in a Beech D-18 aircraft provided by the Survey's Water Resources Division. Likewise, more reliable ground data was obtained at this time owing to improved instrumentation and technique. Ground data were taken by Geological Survey personnel including W. A. Fischer, J. D. Friedman, W. R. Hemphill, D. L. Daniels, G. R. Boynton, Po W. Philbin and the author. C. R. Fross operated the infrared scanner during the August, 1966 survey and R. M. Turner was-responsible for photo processing of the infrared imagery. Their assistance is gratefully acknowledged.

Open-File Report↗
USGS1969

Preliminary geologic interpretation of aeromagnetic data in the Yakutat district, Alaska

An aeromagnetic survey covering portions of the Yakutat Feveland region in south-central Alaska was made to delineate concentrations of magnetic minerals possibly associated with heavy mineral placers in beach sands and raised beach ridges. However, the larger magnetic anomalies do not correlate with the beach placers in the surveyed area. The dominant magnetic feature, a strong linear positive anomaly almost parallel to the coastline, is thought to reflect a bedrock feature, probably a mafic igneous body enclosed within nonmagnetic rocks of the Yakutat group.

Open-File Report↗
USGS1969

Preliminary geologic interpretation of aeromagnetic data in the Nixon Fork district, Alaska

An aeromagnetic map covering 480 square miles was compiled for the Nixon Fork district, which is located approximately 35 miles northeast of McGrath, Alaska. The survey was flown in search of concealed intrusive rocks which may have produced contact metamorphic deposits in limestone similar to the known lode deposits which have been the principal source of gold in the district. The exposed quartz monzonite stocks with which the lode deposits are associated produce negative magnetic anomalies. Slight to moderately strong positive anomalies correlate with granitic intrusives in contact with Upper Cretaceous rocks in the Iditarod-Nixon Fork fault zone. No significant mineral deposits have been found in conjunction with these granitic bodies. Positive anomalies, delineating buried intrusives, occur near the east and west boundaries of the mapped area. The nature of the westernmost intrusive is unknown. An area of possible economic interest lies between Limestone Mountain and Whirlwind-Canyon Creeks in the eastern sector of the mapped area. An elliptical positive anomaly is superimposed on an elongate, slightly negative anomaly. This negative anomaly may represent an intrusive similar to the quartz monzonite with which the lode deposits are affiliated. The positive anomaly may be a near-vertical mafic dike intruded to within 50 feet of the surface of a limestone ridge. Limestone in the vicinity of the dike may be a favorable area for prospecting for lode deposits similar to the known gold-producing deposits of the district.

Alaska↗
USGS1973

Interpretation; Apollo 9 photography of parts of southern Arizona and southern New Mexico

Examination of small-scale (approximately 1:650,000) multispectral photographs obtained on the Apollo 9 mission in March 1969 revealed that in semiarid, regions features due to differences in soils or quantity of vegetation could most easily be discriminated on the color infrared photographs. Where there is sufficient ground truth, it is possible to delineate regional wildland plant communities on the basis of tone, however, the precision of the method may be improved by using photographs obtained two or more times during the year. Sites where vegetation-improvement practices have been completed are not always discernible. For example, where waterspreaders have been constructed, there was sufficient change in the density of vegetation to be readily detected on the photographs; however, pinyon-juniper to grass, conversions or contour furrowing did not always produce a sufficient change in the vegetation to be detected on the photographs.

Open-File Report↗
USGS1975

Preliminary description and interpretation of cores and radiographs from Clear Lake, Lake County, California: Core 7

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 km 2 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 .:s 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 133.09 m (Table 1).

California↗