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At least 91 records · Page 5Linked to original sources
USGS1956

Geology and petrology of the Lava Mountains, San Bernardino County, California

The Lava Mountains are a range of low mountains along the northern edge of the Mojave Desert, California. The pre-Tertiary rocks consist of a few swell pendants of metamorphic rocks in Atolia quartz monzonite. Overlying these are small patches of volcanic and sedimentary rocks, probably Tertiary, which project into the later formations. The major sedimentary unit is the middle Pliocene 3edrock Spring formation; it consists chiefly of arkosic sandstone and conglomerate with lesser amounts of siltstone and brecciated volcanic rocks. Overlying this formation are two late Pliocene formations, the Almond Mountain volcanic ant Klinker Mountain volcanics in the eastern and western parts of the area, respectively. Small areas of other late Pliocene(?) volcanic rocks are locally present. Overlying these are flaws of the Lava Mountains andesite of very late Pliocene age. The Pleistocene(?) Christmas Canyon formation is restricted to the eastern half of the area. A few small dikes of basalt cut this formation. Quaternary gravels, alluvium, and travertine are the youngest deposits.

California↗
USGS1982

Geohydrology of principal aquifers in the Republican River basin, Kansas

Principal aquifers in the Republican River basin in Kansas are unconsolidated alluvial deposits. One such aquifer is formed by the Ogallala Formation of Miocene age which covers most of the western part of the area. Because saturated thickness of the aquifer decrease northeastward, maximum yields to irrigation wells decrease in that direction from 2,000 to 500 gallons per minute. The Grand Island Formation of Pleistocene age occurs in an ancestral channel of the Republican River in northeast Jewell and northwest Republic counties. The maximum yield to wells from this aquifer was estimated to be 2,000 gallons per minute. Quaternary alluvium of Pleistocene and Holocene age occurs in most major stream valleys. The aquifer in the Republican River valley yields as much as 2,000 gallons per minute to irrigation wells. Water levels in the Ogallala Formation commonly declined from 5 to 40 feet during 1950-77 as a result of irrigation withdrawals. Recharge from irrigation by stream diversions have raised water levels as much as 25 feet in the Grand Island Formation and as much as 15 feet in the Quaternary alluvium of the Prairie Dog Creek valley. (USGS)

Open-File Report↗
USGS1992

Mineral and energy resources of the BLM Roswell Resource Area, east-central New Mexico

The sedimentary formations of the Roswell Resource Area have significant mineral and energy resources. Some of the pre-Pennsylvanian sequences in the Northwestern Shelf of the Permian Basin are oil and gas reservoirs, and Pennsylvanian rocks in Tucumcari basin are reservoirs of oil and gas as well as source rocks for oil and gas in Triassic rocks. Pre-Permian rocks also contain minor deposits of uranium and vanadium, limestone, and associated gases. Hydrocarbon reservoirs in Permian rocks include associated gases such as carbon dioxide, helium, and nitrogen. Permian rocks are mineralized adjacent to the Lincoln County porphyry belt, and include deposits of copper, uranium, manganese, iron, polymetallic veins, and Mississippi-valley-type (MVT) lead-zinc. Industrial minerals in Permian rocks include fluorite, barite, potash, halite, polyhalite, gypsum, anhydrite, sulfur, limestone, dolomite, brine deposits (iodine and bromine), aggregate (sand), and dimension stone. Doubly terminated quartz crystals, called "Pecos diamonds" and collected as mineral specimens, occur in Permian rocks along the Pecos River. Mesozoic sedimentary rocks are hosts for copper, uranium, and small quantities of gold-silver-tellurium veins, as well as significant deposits of oil and gas, COa, asphalt, coal, and dimension stone. Mesozoic rocks contain limited amounts of limestone, gypsum, petrified wood, dinosaur remains, and clays. Tertiary rocks host ore deposits commonly associated with intrusive rocks, including platinum group elements, iron skarns, manganese, uranium and vanadium, molybdenum, polymetallic vein deposits, gold-silver- tellurium veins, and thorium-rare earth veins. Museum-quality quartz crystals in Lincoln County were formed in association with intrusive rocks in the Lincoln County porphyry belt. Industrial minerals in Tertiary rocks include fluorite, vein- and bedded-barite, caliche, limestone, and aggregate. Tertiary and Quaternary sediments host important placer deposits of gold and titanium, and minor silver, uranium occurrences, as well as important industrial commodities, including caliche, limestone and dolomite, and aggregate (sand). Quaternary basalt contains sub-ore-grade uranium, scoria, and clay deposits.

New Mexico↗
USGS2009

Submarine canyon and fan systems of the California Continental Borderland

Late Quaternary turbidite and related gravity-flow deposits have accumulated in basins of the California Borderland under a variety of conditions of sediment supply and sea-level stand. The northern basins (Santa Barbara, Santa Monica, and San Pedro) are closed and thus trap virtually all sediment supplied through submarine canyons and smaller gulley systems along the basin margins. The southern basins (Gulf of Santa Catalina and San Diego Trough) are open, and, under some conditions, turbidity currents flow from one basin to another. Seismic-reflection profiles at a variety of resolutions are used to determine the distribution of late Quaternary turbidites. Patterns of turbidite-dominated deposition during lowstand conditions of oxygen isotope stages 2 and 6 are similar within each of the basins. Chronology is provided by radiocarbon dating of sediment from two Ocean Drilling Program sites, the Mohole test-drill site, and large numbers of piston cores. High-resolution, seismic-stratigraphic frameworks developed for Santa Monica Basin and the open southern basins show rapid lateral shifts in sediment accumulation on scales that range from individual lobe elements to entire fan complexes. More than half of the submarine fans in the Borderland remain active at any given position of relative sea level. Where the continental shelf is narrow, canyons are able to cut headward during sea-level transgression and maintain sediment supply to the basins from rivers and longshore currents during highstands. Rivers with high bedload discharge transfer sediment to submarine fans during both highstand and lowstand conditions. ?? 2009 The Geological Society of America.

Special Paper of the Geological Society of America↗
USGS1990

Trace-element and Sr, Nd, Pb, and O isotopic composition of Pliocene and Quaternary alkali basalts of the Patagonian Plateau lavas of southernmost South America

The Pliocene and Quaternary Patagonian alkali basalts of southernmost South America can be divided into two groups. The "cratonic" basalts erupted in areas of Cenozoic plateau volcanism and continental sedimentation and show considerable variation in 87Sr/86Sr (0.70316 to 0.70512), 143Nd/144Nd (e{open}Nd) and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios (18.26 to 19.38, 15.53 to 15.68, and 38.30 to 39.23, respectively). These isotopic values are within the range of oceanic island basalts, as are the Ba/La, Ba/Nb, La/Nb, K/Rb, and Cs/Rb ratios of the "cratonic" basalts. In contrast, the "transitional" basalts, erupted along the western edge of the outcrop belt of the Pliocene and Quaternary plateau lavas in areas that were the locus of earlier Cenozoic Andean orogenic arc colcanism, have a much more restricted range of isotopic composition which can be approximated by 87Sr/86Sr=0.7039??0.0004, e{open}Nd, 206Pb/204Pb=18.60??0.08, 207Pb/204Pb=15.60??0.01, and 208Pb/204Pb=38.50??0.10. These isotopic values are similar to those of Andean orogenic are basalts and, compared to the "cratonic" basalts, are displaced to higher 87Sr/86Sr at a given 143Nd/144Nd and to higher 207Pb/204Pb at a given 208Pb/204Pb. The "transitional" basalts also have Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios higher than the "cratonic" and oceanic island basalts, although not as high as Andean orogenic are basalts. In contrast to the radiogenic isotopes, ??18O values for both groups of the Patagonian alkali basalts are indistinguishable and are more restricted than the range reported for Andean orogenic are basalts. Whole rock ??18O values calculated from mineral separates for both groups range from 5.3 to 6.5, while measured whole rock ??18O values range from 5.1 to 7.8. The trace element and isotopic data suggest that decreasing degrees of partial melting in association with lessened significance of subducted slabderived components are fundamental factors in the west to east transition from arc to back-arc volcanism in southern South America. The "cratonic" basalts do not contain the slab-derived components that impart the higher Ba/La, Ba/Nb, La/Nb, Cs/Rb, 87Sr/86Sr at a given 143Nd/144Nd, 207Pb/204Pb at a given 208Pb/204Pb, and ??18O to Andean orogenic arc basalts. Instead, these basalts are formed by relatively low degrees of partial melting of heterogeneous lower continental lithosphere and/or asthenosphere, probably due to thermal and mechanical pertubation of the mantle in response to subduction of oceanic lithosphere below the western margin of the continent. The "transitional" basalts do contain components added to their source region by either (1) active input of slab-derived components in amounts smaller than the contribution to the mantle below the arc and/or with lower Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios than below the arc due to progressive downdip dehydration of the subducted slab; or (2) subarc source region contamination processes which affected the mantle source of the "transitional" basalts earlier in the Cenozoic. ?? 1990 Springer-Verlag.

Contributions to Mineralogy and Petrology↗
USGS1981

Tabulation of the ostracode assemblages and associated organisms from selected bottom grab samples taken in the northeast Gulf of Alaska, F.R.S. Townsend Cromwell Cruise IGAL-75-KC, 1975

The U.S. Geological Survey is conducting studies of the Alaskan continental shelf, identifying areas and processes of geological hazard that may affect resource development offshore. These hazards include areas of rapid accumulation of unconsolidated sediment, areas of intense erosional activity, and regions of submarine sliding and slumping; shallow faults are also being identified and classified. The region of concern in this report is the continental shelf of the Northeast Gulf of Alaska, between Montague Island (longitude 148° W.) and Icy Bay (longitude 141° W.), figs. 2 and 3. During 1975, nearly 350 bottom grab samples were collected from this region by the Fisheries Research Ship Townsend Cromwell. These samples formed the basis for the initial characterization of the surface deposits. Four major sedimentary units were defined on the basis of the bottom grab samples and seismic data (fig. 1) (Carlson and Molnia, 1977; Molnia and Carlson, 1978). These units are (1) Holocene glacial—marine sediments (normal marine deposition), (2) Holocene morainal deposits, (3) Quaternary glacial—marine sediments, and (4) Pleistocene and older lithified sediments. Each of these sedimentary units is in turn composed of various facies defined by lithological, structural, and biological parameters (Molnia and Carlson, 1980). As part of the Northeast Gulf of Alaska project, I am examining the ostracode assemblages occurring in the Cromwell bottom grab samples. This report provides a tabulation of the fauna and flora contained in 102 selected bottom grab samples (figs. 2 and 3). A baseline datum is being established of the environmental factors that significantly control or contribute to the distributional patterns of modern ostracode species occurring in the Gulf of Alaska. The ostracode biofacies defined by characteristic assemblages of species, together with information on the sedimentary facies, provides a model of the environments presently occurring in the Gulf of Alaska, (Brouwers, 1981). This model forms a vital basis for the interpretation of Neogene and Quaternary glaciomarine environments in the Gulf of Alaska Tertiary Province.

Alaska↗
USGS2022

Diverse responses of vegetation and fire after Pleistocene megaherbivore extinction across the eastern US

Megaherbivores are keystone species whose removal from landscapes can cause cascading ecosystem changes, yet the consequences of Late Quaternary megaherbivore extinctions remain uncertain. This paper tests the Megaherbivory Release Hypothesis (MRH), which posits that the decline and extinction of megaherbivores (body size >1000 kg) during the last deglaciation in eastern North America contributed to the expansion of more palatable hardwood tree taxa, the development of vegetation assemblages with no modern analogue, and increased fuel load and fire activity. Coprophilous fungal spores in lake sediment records are used as proxies for megaherbivore abundance and are essential to testing the MRH through analyses of lead/lag relationships among vegetation composition, megaherbivore abundance, fire, and climate. Although some prior analyses of coprophilous fungal spores from individual sites have supported the MRH, these interpretations have been complicated by 1) discrepancies in the timing of coprophilous spore declines versus megaherbivore extinction timing based on dated vertebrate remains, 2) reliance on a single fungal taxon ( Sporormiella ) rather than a full suite of coprophilous fungi taxa, and 3) uncertainties in the taphonomic processes that influence fungal spore abundances. To examine the spatiotemporal relationships among megaherbivory, vegetation, and fire, we developed five new multi-taxon coprophilous fungal spore records for comparison with existing pollen, spore, and charcoal records from 14 sites across eastern North America. The MRH was well supported in the northeast and central US, with most sites showing a coprophilous spore decline by ∼14.6 ka followed by a rise of hardwood taxa (∼14.4 ka). However, changes in fire regime varied widely among northeast and central US sites and may have preceded spore declines. The MRH was not well supported in the southeastern US, where a smaller rise in hardwood taxa (∼16.1–13.1 ka) generally preceded the decline in coprophilous spores at individual sites (∼15.8–12.7 ka). These site-level and regional differences suggest spatial variations in the strength of couplings among late-Quaternary megaherbivore extinctions, vegetation composition and structure, and fire regime. Possible explanations for the differences between the northern and southeastern US include (1) differences in landscape heterogeneity of canopy openness and palatability, (2) net primary productivity and sensitivity to top-down trophic effects, (3) megaherbivore density, and (4) climate trends and seasonality at orbital to millennial timescales.

eastern United States↗