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At least 217 records · Page 12Linked to original sources
USGS2013

Status and understanding of groundwater quality in the San Francisco Bay groundwater basins, 2007—California GAMA Priority Basin Project

Groundwater quality in the approximately 620-square-mile (1,600-square-kilometer) San Francisco Bay study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in the Southern Coast Ranges of California, in San Francisco, San Mateo, Santa Clara, Alameda, and Contra Costa Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA San Francisco Bay study was designed to provide a spatially unbiased assessment of the quality of untreated groundwater within the primary aquifer system, as well as a statistically consistent basis for comparing water quality throughout the State. The assessment is based on water-quality and ancillary data collected by the USGS from 79 wells in 2007 and is supplemented with water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer system is defined by the depth interval of the wells listed in the CDPH database for the San Francisco Bay study unit. The quality of groundwater in shallower or deeper water-bearing zones may differ from that in the primary aquifer system; shallower groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. Water- quality data from the CDPH database also were incorporated for this assessment. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifer system of the San Francisco Bay study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California benchmarks. A relative-concentration greater than (>) 1.0 indicates a concentration greater than a benchmark, and a relative-concentration less than or equal to (≤) 1.0 indicates a concentration equal to or less than a benchmark. Relative-concentrations of organic and special-interest constituents were classified as low (relative- concentration ≤ 0.1), moderate (0.1 < relative- concentration ≤ 1.0), or high (relative-concentration > 1.0). Inorganic constituent relative- concentrations were classified as low (relative-concentration ≤ 0.5), moderate (0.5 < relative-concentration ≤ 1.0), or high (relative- concentration > 1.0). A lower threshold value of relative-concentration was used to distinguish between low and moderate values of organic constituents because organic constituents are generally less prevalent and have smaller relative-concentrations than naturally occurring inorganic constituents. Aquifer-scale proportion was used as the metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the primary aquifer system that has relative-concentration greater than 1.0 for a particular constituent or class of constituents; proportion is based on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentages of the primary aquifer system that have moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially weighted—were used to evaluate aquifer-scale proportion for individual constituents and classes of constituents. Grid-based and spatially weighted estimates were comparable in the San Francisco Bay study unit (90-percent confidence intervals). Inorganic constituents with health-based benchmarks were present at high relative-concentrations in 5.1 percent of the primary aquifer system, and at moderate relative-concentrations in 25 percent. The high aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of barium (3.0 percent) and nitrate (2.1 percent). Inorganic constituents with secondary maximum contaminant levels were present at high relative-concentrations in 14 percent of the primary aquifer system and at moderate relative-concentrations in 33 percent. The constituents present at high relative-concentrations included total dissolved solids (7.0 percent), chloride (6.1 percent), manganese (12 percent), and iron (3.0 percent). Organic constituents with health-based benchmarks were present at high relative-concentrations in 0.6 percent and at moderate relative-concentrations in 12 percent of the primary aquifer system. Of the 202 organic constituents analyzed for, 32 were detected. Three organic constituents were frequently detected (in 10 percent or more of samples): the trihalomethane chloroform, the solvent 1,1,1-trichloroethane and the refrigerant 1,1,2-trichlorotrifluoroethane. One special-interest constituent, perchlorate, was detected at moderate relative-concentrations in 42 percent of the primary aquifer system. The second component of this work, the understanding assessment, identified some of the primary natural and human factors that may affect groundwater quality by evaluating land use, physical characteristics of the wells, and geochemical conditions of the aquifer. Results from these evaluations were used to explain the occurrence and distribution of constituents in the study unit.

California↗
USGS2020

New method for correcting bottomhole temperatures acquired from wireline logging measurements and calibrated for the onshore Gulf of Mexico Basin, U.S.A.

Bottomhole temperature (BHT) measurements offer a useful way to characterize the subsurface thermal regime as long as they are corrected to represent in situ reservoir temperatures. BHT correction methods calibrated for the domestic onshore Gulf of Mexico basin were established in this study. These corrections are empirically derived and based on newly compiled databases of BHT wireline measurements and, to a lesser extent, drill stem test data. A unified BHT correction for the onshore Gulf Coast region, as well as 12 distinct BHT correction equations for each of the 12 physiographic provinces within the onshore Gulf Coast region, are provided. This study also characterizes the geothermal gradient across the onshore Gulf of Mexico basin, which ranges from 1.89 degrees Fahrenheit per 100 feet in the Sabine Uplift area to 1.39 degrees Fahrenheit per 100 feet in the Southern Louisiana Salt Basin. This report disseminates the slides presented at the 68th annual convention of the Gulf Coast Association of Geological Societies and the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists that was held September 30–October 2, 2018, in Shreveport, Louisiana.

Alabama, Arkansas, Louisiana, Mississippi, Texas↗
USGS1979

Makah Formation--a deep marginal basin sedimentary sequence of Late Eocene and Oligocene age in the northwestern Olympic Peninsula, Washington

The Makah Formation of the Twin River Group crops out in a north-west-trending linear belt in the northwesternmost part of the Olympic Peninsula, Wash. This marine sequence consists of 2,800 meters of predominantly thin-bedded siltstone and sandstone that encloses six distinctive members. The named members include four packets of thick-bedded amalgamated turbidite sandstone, an olistostromal shallow-water marine sandstone and conglomerate member, and a thin-bedded water-laid tuff member. A local unconformity of submarine origin occurs within the lower part of the Makah Formation except in the central part of the study area, where it forms the contact between the older Hoko River Formation and the Makah. Foraminiferal faunas indicate that the Makah Formation ranges in age from late Eocene (late Narizian Stage) to late Oligocene (Zemorrian Stage) and was deposited in a predominantly lower to middle bathyal environment. The Makah strata are part of a deep marginal basin facies that crops out in the western part of the Olympic Peninsula, in southwesternmost Washington and coastal embayments in northwestern Oregon, and along the central part of the coast of western Vancouver Island. On the basis of limited subsurface data from exploratory wells, correlative deepmarginal-basin deposits underlie the inner continental shelf of Oregon and the continental shelf (Tofino Basin) along the southwestern side of Vancouver Island. Directional structures in the Makah Formation indicate that the predominantly lithic arkosic sandstone that forms the turbidite packets was derived from the northwest. A possible source of the clastics is the dioritic, granitic, and volcanic terranes in the vicinity of the Hesquiat Peninsula on the west coast of Vancouver Island. Vertical and lateral variations of turbidite facies suggest that the four packets of sandstone were formed as depositional lobes on an outer submarine fan. The thin-bedded strata between the turbidite packets have characteristics of basin-plain and outer-fan fringe deposits.

Washington↗
USGS1994

Preliminary results of a binational research cruise in the Western Arctic Ocean

This paper is a condensed version of a report on the preliminary results of a research cruise under the direction of the U. S. Geological Survey, on board the United States Coast Guard Cutter Polar Star to Northwind Ridge and Canada Basin of the Western Arctic Ocean, during the period August 16‐September 15, 1993. Major objectives of the cruise were to: survey the geology of the North‐wind Ridge and Canada Basin; determine whether radionuclide contamination from disposal of solid and liquid nuclear wastes by the former Soviet Union in the Kara and Barents seas had penetrated the North American Arctic; acquire sediment cores in support of research on the history of glaciation in the region; and gain a better understanding of water structure and currents, sea‐ice physics, and sediment and nutrient transport.

Arctic Ocean, Canada Basin, Northwind Ridge↗
USGS2000

Estuaries of the northeastern United States: Habitat and land use signatures

Geographic signatures are physical, chemical, biotic, and human-induced characteristics or processes that help define similar or unique features of estuaries along latitudinal or geographic gradients. Geomorphologically, estuaries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of Maine shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons occur within the northeast region, but the dominant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast estuaries are generally greater when compared to estuaries of the more southern U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drainage basins, low riverine flows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water clarity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and rocky shores represent major habitat types that fringe northeast estuaries, supporting commercially-important fauna, forage nekton and benthos, and coastal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a century of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment facilities and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast, with relative importance increasing for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure function, and processes of estuaries along latitudinal gradients.

Connecticut, Maine, Massachusetts, New Hampshire, ↗
USGS1998

Environmental setting of the San Joaquin-Tulare basins, California

The National Water-Quality Assessment Program for the San Joaquin-Tulare Basins began in 1991 to study the effects of natural and anthropogenic influences on the quality of ground water, surface water, biology, and ecology. The San Joaquin-Tulare Basins study unit, which covers approximately 31,200 square miles in central California, is made up of the San Joaquin Valley, the eastern slope of the Coast Ranges to the west, and the western slope of the Sierra Nevada to the east. The sediments of the San Joaquin Valley can be divided into alluvial fans and basin deposits. The San Joaquin River receives water from tributaries draining the Sierra Nevada and Coast Ranges, and except for streams discharging directly to the Sacramento-San Joaquin Delta, is the only surface- water outlet from the study unit. The surface-water hydrology of the San Joaquin-Tulare Basins study unit has been significantly modified by development of water resources. Almost every major river entering the valley from the Sierra Nevada has one or more reservoirs. Almost every tributary and drainage into the San Joaquin River has been altered by a network of canals, drains, and wasteways. The Sierra Nevada is predominantly forested, and the Coast Ranges and the foothills of the Sierra Nevada are predominately rangeland. The San Joaquin Valley is dominated by agriculture, which utilized approximately 14.7 million acre-feet of water and 597 million pounds active ingredient of nitrogen and phosphorus fertilizers in 1990, and 88 million pounds active ingredient of pesticides in 1991. In addition, the livestock industry contributed 318 million pounds active ingredient of nitrogen and phosphorus from manure in 1987. This report provides the background information to assess the influence of these and other factors on water quality and to provide the foundation for the design and interpretation of all spatial data. These characterizations provide a basis for comparing the influences of human activities among basins and specific land use settings, as well as within and among study units at the national level.

California↗
USGS1984

Paleomagnetic constraints on the interpretation of early Cenozoic Pacific Northwest paleogeography

Widespread Cenozoic clockwise tectonic rotation in the Pacific Northwest is an established fact; however, the geologic reconstructions based on these rotations are the subject of continuing debate. Three basic mechanisms have been proposed to explain the rotations: (1) simple shear rotation of marginal terranes caught in the dextral shear couple between oceanic plates and North America; (2) rotation during oblique microplate collision and accretion to the continental margin; and (3) rotation of continental margin areas during episodes of intracontinental extension. In areas where detailed structure and stratigraphy are available, distributed shear rotations are amplv demonstrated paleomagnetically. However, rotation due to asymmetric interarc extension must be significant, especially for the Oregon Coast Range, in light of recent estimates of large Tertiary extension across the northern Basin and Range. The relative importance of shear versus extension is difficult to determine, but shear could account for nearly onehalf of the observed rotations. Oblique microplate collision has not contributed significantly to the observed Cenozoic rotations because most of the rotation post-dates collision-related deformation in the Oregon and Washington. Coast Range. The resultant continental reconstructions suggest that about 300 km of extension has occurred at 42°N. latitude (southern Oregon border) since early Eocene time. This reconstruction suggests that Cretaceous sedimentary basins east of the Klamath Mountains have undergone significant Tertiary extension (about f<0%) , but little rotation. Upper Cretaceous sedimentary rocks in the Blue Mountains of Oregon near Mitchell are probably rotated at least 15° and perhaps as much as 60°, which allows considerable latitude in the restoration of that part of the basin.

Pacific Section S.E.P.M.↗
USGS1996

Influences of environmental settings on aquatic ecosystems in the Apalachicola-Chattahoochee-Flint River basin

The watershed boundary of the Apalachicola-Chattahoochee-Flint (ACF) River basin defines an aquatic ecosystem whose water quality is the result of complex interactions of natural and human influences on land and water resources. Topics relating to the basin's environmental setting-its physical, biological, and cultural characteristics-are summarized to provide an understanding of factors that influence water quality and the health of aquatic ecosystems. The ACF River basin lies partly in southwestern Georgia, southeastern Alabama, and northwestern Florida and covers 19,800 square miles in the Blue Ridge, the Piedmont, and the Coastal Plain Provinces. The basin includes the drainages of the Chattahoochee River and the Flint River, which meet to form the Apalachicola River. The Apalachicola River flows into the Gulf of Mexico at Apalachicola Bay. Basin hydrology and water quality are influenced by 16 mainstem reservoirs, 13 of which are on the Chattahoochee River. Ground water in the basin is contained in six aquifers-the surficial aquifer system, the Floridan aquifer system, the Claiborne aquifer, the Clayton aquifer, the Providence aquifer, and the crystalline-rock aquifer. Physiography, climate, and hydrology of the ACF River basin provide natural conditions that support a rich and abundant diversity of plants and animals. Although most of the ACF River basin has been altered by human activities, the basin's environment is noteworthy for its remaining biological diversity and the role it plays in sustaining biological productivity in Apalachicola Bay. The Bay produces 90 percent of Florida's and 13 percent of the Nation's oyster harvest; and functions as a nursery for penaeid shrimp, blue crabs, and a variety of fin fish. The diversity of the basin's aquatic fauna is noteworthy because the basin is home to (1) the largest number of fish species among Gulf Coast drainages east of the Mississippi River, (2) the largest assemblage of freshwater fish in Florida, (3) the largest number of mollusc species among western Florida drainages, and (4) the highest species density of amphibians and reptiles on the continent north of Mexico. Population of the ACF River basin in 1990 was estimated at 2.6 million. Nearly 90 percent of the total population lived in Georgia, and nearly 60 percent lived in the Metropolitan Atlanta area. The 1990 basin population is projected to increase by 15 percent to 3.0 million by the year 2000, and by 30 percent to 3.4 million by 2010. The largest increases in populations are projected for the Metropolitan Atlanta area. In 1972-76, approximately 59 percent of the basin was covered by forest, 29 percent was agricultural, 5 percent was wetland, 4 percent was urban, and 3 percent was water or barren land. Most of the original land cover of the basin has been transformed by human activity. Timber is the basin's largest cash crop and most forests consist of second-growth stands or large acreages of planted pine. The dominant agricultural land use in the Piedmont Province is pasture and confined feeding for dairy, livestock, and poultry production. Row-crop agriculture, orchards, and silviculture are most common in the Coastal Plain Province. The top five crops in order from most to least acres harvested in 1990 were peanuts, corn, soybeans, wheat, and cotton. The water in the basin is used for public and industrial supply, irrigation, power generation, navigation, and recreation. Although most public-supply withdrawals in the Blue Ridge and Piedmont Provinces are from surface-water sources, with the exception of counties near or immediately below the Fall Line, all publicly supplied water in the Coastal Plain is withdrawn from ground-water sources. Ground water supplied 18 percent of the basin's population served by public supply. Total water withdrawn in the ACF River basin in 1990 was 2,098 million gallons per day (Mgal/d), of which Georgia withdrew 82 percent and Florida and Alabama each withdrew 9 percent. Power generation is the single largest water use. Sixteen of the basin's 22 power generating plants are located along the mainstem of the Chattahoochee River. The U.S. Army Corps of Engineers maintains a navigation channel from the mouth of the Apalachicola River to Columbus, Ga., on the Chattahoochee River and to Bainbridge, Ga., on the Flint River. Water quality in the basin is influenced by the operation of 137 municipal wastewater-treatment facilities. In 1990, 354 Mgal/d of municipal wastewater was discharged within the ACF River basin. Eighty-eight percent of the wastewater was discharged into the Chattahoochee River basin, 10.6 percent into the Flint River basin, and 1.4 percent into the Apalachicola River basin. Two-thirds of the 938 stream miles in the Georgia portion of the ACF River basin having water quality that does not meet or only partially meets the designated-use criteria in the Chattahoochee River basin. The Chattahoochee River is the most heavily-used water resource both in the ACF River basin and in Georgia. Urban runoff or unknown nonpoint sources are cited as the causes of water-quality regulations in 72 percent of violations. The remaining causes primarily are combined sewer overflows in the Atlanta area, and discharges from municipal or industrial treatment facilities with inadequate treatment capabilities or operational deficiencies.

Alabama, Florida, Georgia↗
USGS1965

Structure, Quaternary history, and general geology of the Corral Canyon area, Los Angeles County, California

The Corral Canyon nuclear power plant site consists of about 305 acres near the mouth of Corral Canyon in the central Santa Monica Mountains; it is located on an east-trending segment of the Pacific Coast between Point Dume and Malibu Canyon, about 28 miles due west of Los Angeles. The Santa Monica Mountains are the southwesternmost mainland part of the Transverse Ranges province, the east-trending features of which transect the otherwise relatively uniform northwesterly trend of the geomorphic and geologic features of coastal California. The south margin of the Transverse Ranges is marked by the Santa Monica fault system, which extends eastward near the 34th parallel for at least 145 miles from near Santa Cruz Island to the San Andreas fault zone. In the central Santa Monica Mountains area the Santa Monica fault system includes the Malibu Coast fault and Malibu Coast zone of deformation on the north; from the south it includes an inferred fault--the Anacapa fault--considered to follow an east-trending topographic escarpmemt on the sea floor about 5 miles south of the Malibu Coast fault. The low-lying terrain south of the fault system, including the Los Angeles basin and the largely submerged Continental Borderland offshore, are dominated by northwest-trending structural features. The Malibu Coat zone is a wide, east-trending band of asymmetrically folded, sheared, and faulted bedrock that extends for more than 20 miles along the north margin of the Santa Monica fault system west of Santa Monica. Near the north margin of the Malibu Coast zone the north-dipping, east-trending Malibu Coast fault juxtaposes unlike, in part contemporaneous sedimentary rock sections; it is inferred to be the near-surface expression of a major crustal boundary between completely unrelated basement rocks. Comparison of contemporaneous structural features and stratigraphic sections (Late Cretaceous to middle Miocene sedimentary, rocks and middle Miocene volcanic and intrusive igneous rocks on the north; middle and upper Miocene sedimentary and middle Miocene volcanic rocks on the south) across the fault demonstrates that neither strike slip of less than 25 miles nor high-angle dip slip can account for this juxtaposition. Instead, the Malibu Coast fault is inferred to have been the locus of large-magnitude, north-south oriented, horizontal shortening (north, or upper, block thrust over south block). This movement occurred at or near the northern boundary of the Continental Borderland, the eastern boundary of which is inferred to be the northwest-trending known-active Newport-Inglewood zone of en echelon right lateral strike-slip faults in the western Los Angeles basin. Local structural features and their relation to regional features, such as those in the Malibu Coast zone, form the basis for the interpretation that the Malibu Coast fault has acted chiefly as a thrust fault. Within the Malibu Coast zone, on both sides of the Malibu Coast fault, structural features in rocks that range in age from Late Cretaceous to late Miocene are remarkably uniform in orientation. The predominant trend of bedding, axial surfaces of numerous asymmetric folds, locally pervasive shear surfaces, and faults is approximately east-west and their predominant dip is northward.. The axes of the folds plunge gently east or west. Evidence from faults and shears within the zone indicates that relative movement on most of these was north (upper) over south. Beyond the Malibu Coast zone to the north and south the rocks entirely lack the asymmetric folds, overturned beds, and the locally abundant shears that characterize the rocks within the zone; these rocks were therefore not subjected to the same deforming forces that existed near the Malibu Coast fault. Movement on the Malibu Coast fault and deformation in the Malibu Coast zone occurred chiefly during the interval between late Miocene and late Pleistocene time. The youngest-known faulting in the Malibu Coast zone is late Pl

Open-File Report↗
USGS1967

Reconnaissance of the chemical quality of surface waters of the Neches River basin, Texas

The kinds and quantities of minerals dissolved in the surface water of the Neches River basin result from such environmental factors as geology, streamflow patterns and characteristics, and industrial influences. As a result of high rainfall in the basin, much of the readily soluble material has been leached from the surface rocks and soils. Consequently, the water in the streams is usually low in concentrations of dissolved minerals and meets the U.S. Public Health Service drinking-water standards. In most streams the concentration of dissolved solids is less than 250 ppm (parts per million). The Neches River drains an area of about 10,000 square miles in eastern Texas. From its source in southeast Van Zandt County the river flows in a general southeasterly direction and empties into Sabine Lake, an arm of the Gulf of Mexico. In the basin the climate ranges from moist subhumid to humid, and the average annual rainfall ranges from 46 inches is the northwest to more than 52 inches in the southeast. Annual runoff from the basin has averaged 11 inches; however, runoff rates vary widely from year to year. The yearly mean discharge of the Neches River at Evadale has ranged from 994 to 12,720 cubic feet per second. The rocks exposed in the Neches River basin are of the Quaternary and Tertiary Systems and range in age from Eocene to Recent. Throughout most of the basin the geologic formations dip generally south and southeast toward the gulf coast. The rate of dip is greater than that of the land surface; and as a result, the older formations crop out to the north of the younger formations. Water from the outcrop areas of the Wilcox Group and from the older formations of the Claiborne Group generally has dissolved-solids concentrations ranging from 100 to 250 ppm; water from the younger formations has concentrations less than 100 ppm. The northern half of the basin has soft water, with less than 60 ppm hardness. The southern half of .the basin has very soft water, usually with less than 30 ppm hardness. The chloride concentrations are less than 20 ppm in surface water in the southern half of the basin and usually range from 20 to 100 ppm in the northern half of the basin. Concentrations greater than 100 ppm are found only where pollution is occurring. The Neches River basin has an abundance of surface water, but uneven distribution of runoff makes storage projects necessary to provide dependable water supplies. The principal existing reservoirs, with the exception of Striker Creek Reservoir, contain water of excellent quality. Chemical-quality data for the Striker Creek drainage area indicate that its streams are affected by .the disposal of brines associated with oil production. Sam Rayburn Reservoir began impounding water in 1965. The water impounded should prove of acceptable quality for most uses, but municipal and industrial wastes released into the Angelina River near Lufkin may have a degrading effect on the quality of the water, especially during extended periods of low flows. Water available for storage at the many potential reservoir sites will be of good quality; but, if the proposed salt-water barrier is to impound acceptable water, the disposal of oilfield brine into Pine Island Bayou should be discontinued.

Water Supply Paper↗
USGS1961

Origin of the Gulf of California

The probable cumulative Late Cretaceous and Cenozoic right-lateral strike-slip displacement along the San Andreas fault in central California is 350 miles. The San Andreas and the allied faults into which it branches southward trend longitudinally into the Gulf of California , and the seismicity of the region indicates that the fault system follows the length of the Gulf and enters the Pacific basin south of Baja California . Crustal structure of most of the Gulf is of oceanic type, so that an origin by structural depression of continental rocks is not possible. Tectonic styles north and south of Los Angeles differ greatly. To the north, the Coast Ranges expose thick Upper Cretaceous and Cenozoic sedimentary rocks that were deposited in local basins and deformed tightly and repeatedly. To the south, in the Peninsular Ranges and Baja California , correlative rocks are thin and show little compressive deformation. The California batholith of mid-Cretaceous age and allied crystalline rocks form the basement of Baja California , southwestern Arizona, and northwestern Sonora and probably extend along the coast of mainland Mexico; the Gulf apparently bisects the crystalline belt longitudinally. These features suggest that Baja California initially lay 300 miles to the southeast, against the continental-margin bulge of Jalisco. The Gulf of California may be a pull-apart feature caused by strike-slip displacement plus up to 100 miles of cross-strike separation of the continental plate, subcontinental materials having welled up into the rift gap. The strike-slip motion has a tensional component across the continental margin south of Los Angeles but a compressional component to the north.

Gulf of California↗
USGS2016

A spatially explicit suspended-sediment load model for western Oregon

We calibrated the watershed model SPARROW (Spatially Referenced Regressions on Watershed attributes) to give estimates of suspended-sediment loads for western Oregon and parts of northwestern California. Estimates of suspended-sediment loads were derived from a nonlinear least squares regression that related explanatory variables representing landscape and transport conditions to measured suspended-sediment loads at 68 measurement stations. The model gives estimates of model coefficients and their uncertainty within a spatial framework defined by the National Hydrography Dataset Plus hydrologic network. The resulting model explained 64 percent of the variability in suspended-sediment yield and had a root mean squared error value of 0.737. The predictor variables selected for the final model were (1) generalized lithologic province, (2) mean annual precipitation, and (3) burned area (by recent wildfire). Other landscape characteristics also were considered, but they were not significant predictors of sediment transport, were strongly correlated with another predictor variable, or were not as significant as the predictors selected for the final model. The northern Oregon coastal drainages had the highest predicted suspended sediment yields (median yield 475 kilograms per hectare per year) and the Klamath River Basin had the lowest (median yield 53 kilograms per hectare per year). Quaternary deposits were, on average, the largest contributor to incremental suspended-sediment yield even though this lithologic province only makes up 17 percent of the modeling domain. Coast Range sedimentary rocks and Coast Range volcanic rocks had high suspended-sediment yields whereas, in addition to the Klamath terrane, the Western Cascade and High Cascade lithologic provinces had low suspended-sediment yields. Precipitation and the area affected by recent wildfire both positively correlated with suspended-sediment load. Suspended-sediment transport rates predicted by this SPARROW model are less than historical (1956&ndash;73) and long‑term (thousands of years) geological rates. This difference likely results, in part, from biases in the data underlying the SPARROW model, probably resulting in predicted suspended-sediment estimates that underestimate actual transport rates. However, the differences also likely owe to natural and human-caused variation in suspended-sediment yields as they respond to changes in climate, vegetation, fire frequency, and land use. In particular, decreases in mean annual suspended-sediment yields within the Umpqua River Basin since 1956&ndash;73 may owe to less intense forest harvest, passage of the Oregon Forest Practices Act of 1971, and increased emphasis in habitat protection in recent decades. Such sensitivity may have implications for the spatial and temporal distributions of aquatic and riparian habitats. Knowledge of the regionally important patterns and factors in suspended-sediment sources and transport could support broad-scale, water-quality management objectives and priorities. Because of biases and limitations of this model, however, these results are most applicable for general comparisons and for broad areas such as large watersheds. For example, despite having similar area, precipitation, and land-use, the Umpqua River Basin generates 68 percent more suspended sediment than the Rogue River Basin, chiefly because of the large area of Coast Range sedimentary province in the Umpqua River Basin. By contrast, the Rogue River Basin contains a much larger area of Klamath terrane rocks, which produce significantly less suspended load, although recent fire disturbance (in 2002) has apparently elevated suspended sediment yields in the tributary Illinois River watershed. Fine-scaled analysis, however, will require more intensive, locally focused measurements.

Scientific Investigations Report↗
USGS1972

Geohydrologic summary of the Pearl River basin, Mississippi and Louisiana

Fresh water in abundance is contained in large artesian reservoirs in sand and gravel deposits of Tertiary and Quaternary ages in the Pearl River basin, a watershed of 8,760 square miles. Shallow, water-table reservoirs occur in Quarternary deposits (Pleistocene and Holocene) that blanket most of the uplands in .the southern half of the basin and that are present in smaller upland areas and along streams elsewhere. The shallow reservoirs contribute substantially to dry-weather flow of the Strong River and Bogue Chitto and of Holiday, Lower Little, Silver, and Whitesand Creeks, among others. About 3 billion acre-feet of ground water is in storage in the fresh-water section, which extends from the surface to depths ranging from about sea level in the extreme northern part of the basin to more than 3,000 feet below sea level in the southern part of the basin. Variations in low flow for different parts of the river basin are closely related to geologic terrane and occurrence of ground water. The upland terrace belt that crosses the south-central part of the basin is underlain by permeable sand and gravel deposits and yields more than 0.20 cubic feet per second per square mile of drainage area to streamflow, whereas the northern part of the basin, underlain by clay, marl, and fine to medium sand, yields less than 0.05 cubic feet per second per square mile of drainage area (based on 7-day Q2 minimum flow computed from records). Overall, the potential surface-water supplies are large. Because water is available at shallow depths, most of the deeper aquifers have not been developed anywhere in the basin. At many places in the south, seven or more aquifers could be developed either by tapping one sand in each well or by screening two or more sands in a single well. Well fields each capable, of producing several million gallons of water a day are feasible nearly anywhere in the Pearl River basin. Water in nearly all the aquifers is of good to excellent quality and requires little or no treatment for most uses. The water is a soft, sodium bicarbonate type and therefore has a low to moderate dissolved-solids content. Mineral content increases generally downdip in an aquifer. Excessive iron, common in shallow aquifers, is objectionable for some water uses. Water from the streams, except in salty tidal reaches, is less mineralized than ground water; in 10 sites the median dissolved-solids content in streamflow was 50 milligrams per liter or less. Moderately intensive ground-water development has been made in the Bogalusa area, Louisiana; at the Mississippi Test Facility, Hancock County, Miss. ; and in the Jackson area, Mississippi. Wells with pumping rates of 500 to 1,000 gallons per minute each are common throughout the Pearl River basin, and some deep wells flow more than 3,000 gallons per minute in the coastal lowland areas. Probably 20 million gallons per day of artesian water flows uncontrolled from wells in the southern part of the basin. Ground-water levels, except in the higher altitudes, are within 60 feet of the surface, and flowing wells are common in the valleys and in the coastal Pine Meadows. Decline of water level is a problem in only a few small areas. Saline water as a resource is available for development from aquifers and streams near the coast and from aquifers at considerable depth in most of the Pearl River basin. Pollution is a problem in oil fields and in reaches of some streams below sewage and other waste-disposal points. The basin estuary contains water of variable quality but has potential for certain water-use developments that will require special planning and management.

Water Supply Paper↗
USGS1998

Hydrogeology, water quality, water budgets, and simulated responses to hydrologic changes in Santa Rosa and San Simeon Creek ground-water basins, San Luis Obispo County, California

Santa Rosa and San Simeon Creeks are underlain by thin, narrow ground-water basins that supply nearly all water used for local agricultural and municipal purposes. The creeks discharge to the Pacific Ocean near the northwestern corner of San Luis Obispo County, California. The basins contain heterogeneous, unconsolidated alluvial deposits and are underlain by relatively impermeable bedrock. Both creeks usually stop flowing during the summer dry season, and most of the pumpage during that time is derived from ground-water storage. Annual pumpage increased substantially during 1956?88 and is now a large fraction of basin storage capacity. Consequently, dry-season water levels are lower and the water supply is more vulnerable to drought. The creeks are the largest source of ground-water recharge, and complete basin recharge can occur within the first few weeks of winter streamflow. Agricultural and municipal pumpages are the largest outflows and cause dry-season water-level declines throughout the San Simeon Basin. Pumping effects are more localized in the Santa Rosa Basin because of subsurface flow obstructions. Even without pumpage, a large quantity of water naturally drains out of storage at the upper ends of the basins during the dry season. Ground water is more saline in areas close to the coast than in inland areas. Although seawater intrusion has occurred in the past, it probably was not the cause of high salinity in 1988?89. Ground water is very hard, and concentrations of dissolved solids, chloride, iron, and manganese exceed drinking-water standards in some locations. Probability distributions of streamflow were estimated indirectly from a 120-year rainfall record because the periods of record for local stream-gaging stations were wetter than average. Dry-season durations with recurrence intervals between 5 and 43 years are likely to dry up some wells but not cause seawater intrusion. A winter with no streamflow is likely to occur about every 32 years and to result in numerous dry wells, seawater intrusion, and subsidence. Digital ground-water-flow models were used to estimate several items in the ground-water budgets and to investigate the effects of pumpage and drought. The models also were used to investigate the hydrologic effects of selected water-resources management alternatives. Selection of alternatives was not constrained by issues related to water rights, which were under dispute during the study. Increases in the area and intensity of irrigation could increase agricultural water demand by 26 to 35 percent, an increase that would lower water levels by as much as 10 feet and possibly cause subsidence in the lower Santa Rosa Basin. An additional municipal well in the lower Santa Rosa Basin could withdraw 100 acre-feet per year without causing seawater intrusion, but subsidence might occur. Transferring 270 acre-feet per year of treated wastewater from a percolation area near the coast to an area about 0.5 mile upstream of the municipal well field in the San Simeon Basin could raise upstream water levels by as much as 12 feet without causing significant water-table mounding or seawater intrusion. Decreases in agricultural pumping after a winter without streamflow could prevent seawater intrusion while allowing municipal pumping to continue at normal rates.

Water-Resources Investigations Report↗
USGS2018

Methodology for correcting bottomhole temperatures acquired from wireline logging measurements in the onshore U.S. Gulf of Mexico Basin to characterize the thermal regime of total petroleum systems

Characterization of the subsurface thermal regime is critical for understanding many facets of the petroleum system, from thermal maturation of organic-rich source rocks to thermal preservation and non-degradation of hydrocarbon accumulations. On a broad scale, paleo-heatflow has been mapped for the North American continent (Blackwell and Richards, 2004) as well as the contiguous United States (Blackwell et al., 2011). However, in situ reservoir temperature is a fundamental property (Cooper and Jones, 1959) that is difficult to accurately measure in the subsurface (Deming, 1989). Previous work has described the thermal regime of the offshore U.S. Gulf of Mexico Basin (Waples et al., 2004; Forrest et al., 2005; Nagihara and Jones, 2005; Husson et al., 2008); however, due to the lack of an applicable bottomhole temperature (BHT) correction method, virgin rock temperatures of the onshore portion of the basin remains largely uncharacterized in a regional or subregional context. The abundance of BHT measurements offers a useful way to characterize the subsurface thermal environment, provided that they are corrected to reflect the reservoir temperature. This study develops BHT correction methods that are specifically calibrated for the onshore U.S. Gulf of Mexico Basin. These BHT corrections are empirically derived and are based on a newly compiled database of temperatures obtained from BHT wireline measurements and, to a lesser extent, from drill stem test (DST) data. The results of this investigation provide a unified BHT correction methodology for the onshore U.S. Gulf of Mexico Basin as well as provide 12 distinct BHT correction equations for each of the 12 physiographic provinces within the onshore Gulf Coast region. This study also characterizes the geothermal gradient regime across the onshore U.S. Gulf Coast, which ranges from 1.89ºF/100 ft in Sabine Uplift area to 1.39ºF/100 ft in the Southern Louisiana Salt Basin.

Gulf of Mexico Basin↗
USGS2022

A late Cenozoic kinematic model for fault motion within greater Cascadia

Widely accepted tectonic reconstructions indicate at least 100 km of coast-parallel northwestward translation of the Sierra Nevada block of California and 15–20° clockwise rotation of most of Oregon since the current phase of Basin and Range extension began ∼17 Ma. These reconstructions require at least 100 km of convergence between the central Coast Range of Oregon and rigid North America in mainland British Columbia, yet there is little discussion of how such convergence might be distributed. This study offers a kinematic model of the distribution of such deformation, constrained by geodesy, paleomagnetism, and fault offsets in Nevada, California and Oregon. The model includes differential rotation across the thrust faults of the Yakima fold and thrust belt (YFTB), compressive right-lateral faulting in the Washington Cascade Range, substantial thrust faulting within the Puget Lowland, and oroclinal bending and doming in the Olympic Mountains. Shortening across YTFB along 120°W longitude is modeled as 47 km, across Puget Lowland at 123°W (Olympia-Bellingham) is 94 km, and total shortening between the central Oregon Coast Range and northern Washington (Corvallis-Bellingham) is 125 km. Current motion of the coastal regions above the Cascadia subduction zone results from both permanent deformation of the continent and elastic coupling to the subducting plate. Permanent deformation in the model is based on extrapolating geodesy from east of 120°W or south of 40°N, indicating a very uniform convergence velocity with the Juan de Fuca plate for northernmost California and Oregon near 31 mm/yr at N61°E.

California, Idaho, Montana, Nevada, Oregon, Washin↗
USGS2014

Thrust faults and related structures in eastern Cuba

Detailed areal mapping in central Camagüey Province and reconnaissance mapping in northern and eastern Oriente Province, Cuba, have revealed two major structural zones: (1) A zone of intense deformation, including thrust faulting, which lies north of the geographic axis of the island; and (2) a belt of domical mountains bounded on the north by Nipe Bay and the coast, and on the south by the Cauto trough and Guantilnamo basin. In Camagüey, extensive masses of serpentine and overlying tuffs have been complexly folded and overridden from the north by a block, at least 25 miles long, of limestones that form the Sierra de Cubitas and Sierra de Camaján. The overthrust carried a northern fades of Cretaceous and Eocene limestones over a southern fades of tuffaceous rocks of similar age, and had a displacement of at least six miles. In places serpentine was thrust over younger formations, and most of the shearing in the serpentine is attributed to diastrophism. A thrust zone exposed in Loma La Vigía, 15 miles north of Holguín, suggests a similar tectonic history for northern Oriente Province. Chaotic giant breccias that include waterlaid debris indicate that the overthrusts moved across the ancient land surface in both Camagüey and Oriente districts. The folding apparently began in the Cretaceous and culminated in overthrusting during early middle Eocene time. Post‐Eocene deformation appears to be limited to warping or doming to maximum angles of about 20 degrees. The zone of domical mountains is somewhat more than 100 miles long from east to west by 25 to 30 miles wide, and comprises three main units: (1) the Sierra de Nipe and (2) Sierra del Cristal domes, principally of serpentine; and (3) the Cuchillas uplift, which includes the Cuchillas de Toar and Sierra de Purlal, composed of serpentine and pre‐serpentine rocks. These uplifts are overlapped progressively on all sides by sediments ranging in age from Upper Cretaceous to Oligocene and Miocene, the older beds in places being highly folded. The mountains owe their present relief of 2000 to 4000 feet to the doming of an extensive erosion surface in the late Pliocene or early Pleistocene. The north and east flanks of the Cuchillas uplift extend below sea level, and drowned streams and elevated coral reefs show regional instability since the last major doming. ©1947. American Geophysical Union. All Rights Reserved.

Eos, Transactions, American Geophysical Union↗