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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 37 records · Page 2Linked to original sources
USGS1976

Diamond drilling at the Ma'milah Mine, Kingdom of Saudi Arabia

The Ma'millah gold mine is about 90 km southeast of At Ta'if at lat 21°03'N., long 41°18'E., in southwestern Saudi Arabia. The deposit, which was worked extensively by ancient miners, consists of several veins and massive lenses of quartz along a regional fault. The extensive ancient mine workings, large size of some quartz outcrops, and significant gold content of several samples indicated that subsurface exploration was warranted. Accordingly, two holes were drilled into the deposit during the interval December 1972 to February 1973. The drill findings were disappointing; the grade of vein material was found to be too low to be of economic interest and the quartz bodies were found to pinch out both along strike and downdip. The drilling program therefore was terminated. The deposit is not worth further exploration

Ma'milah Mine↗
USGS1976

Water resources of Dinosaur National Monument, Colorado and Utah

Dinosaur National Monument, partly in the Rocky Mountain System and partly in the Colorado Plateaus physiographic province, covers an area of 322 square miles (834 square kilometres) in northwestern Colorado and northeastern Utah. The climate is generally cool and pleasant in May, early June, September, and October; winters are cold. Normal annual precipitation ranges from less than 8 to more than 16 inches (203 to 406 millimetres). Geologic formations in the monument range in age from upper Precambrian to Holocene, but not all ages are represented. The monument is on the south limb of the east-trending regional fold representing the Uinta Mountains. Faults and subsidary folds on the south slope of the Uinta Mountains complicate the geology and hydrology of the area. None of the surface streams in the monument are diverted for public supply, but the Green and Yampa Rivers are a recreational resource for boaters. The flow of the Green River is regulated by Flaming Gorge Reservoir; however, flood potentials are estimated for the Yampa River and three smaller streams. Facilities in the monument are not endangered by probable mean annual floods, but may sustain some damage to facilities by the 25- or 50-year floods. Major aquifers in the monument are sandstone and limestone formations, but these formations are drained in the higher areas. Alluvium along the major stream channels yields small amounts of water to wells, but some of the water is not of suitable chemical quality for public supply. All public water supplies in 1971 were obtained from wells, and the use of water during 1970 was estimated to be 15 million gallons (46 acre-feet or 0.057 cubic hectometres). Most of the ground water obtained from sandstone and limestone is of suitable chemical quality for public supply.

Colorado, Utah↗
USGS1978

Erosion, sediment discharge, and channel morphology in the Upper Chattahoochee River basin, Georgia

Average annual rates of sheet erosion and sediment discharge were computed for several watersheds in the Upper Chattahoochee River basin in Georgia. Erosion yields ranged from about 900 to 6,000 tons per year per square mile in nine watersheds and were greatest where land use is largely agricultural or transitional. Suspended sediment yields from the same watershed ranged from about 300 to 800 tons per year per square mile and were greatest from urban areas and least from mostly forested watersheds. The impact of suspended sediment on stream quality was evaluated for 14 watersheds. In general, 60 percent or more of the total annual discharge of trace metals and phosphorus was contributed by suspended sediment. Yields of trace metals and nutrients in suspension were consistently greater in urban watersheds. Turbidity in basin streams increased geometrically with increasing concentrations of suspended sediment. (Woodard-USGS)

Georgia↗
USGS1978

Ages of flow units in the far eastern lunar maria based on crater density

The distribution of major geologic units of uniform relative age exposed in the far eastern maria (i.e., Mare Marginis, Mare Smythii, and Mare Crisium) and Mare Humorum was compiled in map form on the basis of a crater density mapping technique. Correlation of crater densities and radiometric ages of Apollo landing sites provide estimates of the absolute age for the units. Results indicate that the far eastern maria were emplaced over a period of approximately 1.25 b.y., from about 3.75 b.y. to 2.5 b.y. before present. Extensive young mare units (~ 2.5 ± 0.5 b.y.) occur in all three large far eastern maria. Major old units (~ 3.65 ± 0.05 b.y.) occur in central Mare Crisium and eastern Mare Marginis. Correlation of the age data and remote sensing data suggests that: (1) both young and old units have relatively high Mg/A1 ratios and are relatively rich in Fe and Ti, whereas intermediate age units have lower Mg/Al ratios and less Fe and Ti. A similar relationship previously noted for other maria suggests that this applied throughout the lunar maria; (2) older units generally have higher remnant magnetism than younger units - a relationship also previously noted for other lunar maria and attributed to a steady decline of a primodial lunar magnetic field, and (3) all age units in the eastern maria have relatively low natural radioactivity or abundances of Th, K, and U compared to the western maria (particularly in the Mare Imbrium area). The presence of young lava flows in both the eastern and western maria suggests that the relative abundance of these radioactive elements has played only a minor role in controlling the duration and location of mare volcanism. The crater-density relative age data presented here correlate in a linear fashion with crater-morphology relative age data. A combination of these data provides a nearly complete map of the distribution of units of uniform relative age of the lunar maria and shows that, as previously suggested, the older units (> 3.5 b.y. old) are generally located along the basin edges and the younger units (< 3.5 b.y. old) are generally in the basin centers. However, this map also shows that the vents for the flows of the young units must be located on the edges of the basins. These observations support tectonic models of basin subsidence caused by isostatic adjustment to the weight of the lava and to subsurface evacuation and subsequent collapse as the lavas were erupted.

Open-File Report↗
USGS1979

Preliminary results of the Sabkhah Hazawza gravity project, Wadi as Sirhan area, Kingdom of Saudi Arabia

One hundred thirty seven new gravity stations at an average station density of one station per 17.5 km2 have been established in a 40 x 60 km area centered on Sabkhah Hazawza in the northwestern part of the Kingdom of Saudi Arabia. A successful tie to existing Arabian American Oil Co. (ARAMCO) gravity data was made and a simple Bouguer gravity anomaly map was compiled during the survey. The map shows a distinct gravity low of about -8 mgal associated with the sabkhah, its minimum displaced to the northeast of the longitudinal axis of the sabkhah. However, the continuation of the gravity anomaly under the basalt field to the northeast suggests that the gravity anomaly is due to an older basin-like structure. If the sabkhah deposits are due to damming of ancient Wadi as Sirhan by basalt flows, then the deposits are probably thin. Preliminary estimates give a maximum thickness of about 270 m for the sedimentary fill causing the gravity anomaly.

Wadi as Sirhan area↗