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Research about Mexico, United States

Source-linked reports with geographic coverage including Mexico, United States.

251 records · Page 14Linked to original sources
USGS1985

Organochlorine concentrations, whole body weights, and lipid content of black skimmers wintering in Mexico and in south Texas, 1983

Since 1978, a large proportion of the black skimmers (Rynchops niger) nesting along the Texas coast have had high concentrations of DDE in their eggs. Of 284 eggs collected from 5 sites during 1978-81, 99.5% contained detectable (> 0.i0 ppm) w levels of DDE, ranging up to 86 ppm wet-weight; 36% of the eggs contained > i0 ppm DDE (White et al., 1984). During the 4-year period, geometric mean concentrations of DDE remained strikingly similar, with no significant decline in egg contaminant levels. The sources of DDE contamination in skimmers are unknown. Recoveries of juvenile skimmers banded in Texas, Louisiana, and Mississippi indicate that a large proportion of the birds (60%) spend the winter on the east and west coasts of Mexico. Therefore, it is possible that the DDE exposure to Texas skimmers occurs in Mexico during the winter, although some birds remain along the Gulf Coast year-round.\ This study was conducted to determine the degree of DDE and other organochlorine contamination in black skimmers and their food items from sites in Mexico and Texas, and to statistically compare residue concentrations and body condition in individuals from the 2 areas.

Texas, Veracruz↗
USGS1985

Geohydrology and water resources of the Papago Farms-Great Plain area, Papago Indian Reservation, Arizona, and the upper Rio Sonoyta area, Sonora, Mexico

The Papago Farms-Great Plain and upper Rio Sonoyta study area includes about 490 square miles in south-central Arizona and north-central Sonora, Mexico. The area is characterized by a broad, deep, sediment-filled basin bounded by low, jagged fault-block mountains. The climate is arid to semiarid. The climate and abundant ground water provide favorable conditions for irrigated agriculture. Annual precipitation averages 5 to 8 inches per year on the desert floor. Runoff, which occurs as intermittent streamflow and sheetflow, is too short lived and too laden with suspended sediment to be a reliable source for irrigation or public supply. Nearly all the water used to irrigate more than 5,000 cultivated acres in the study area is withdrawn from the unconsolidated to partly consolidated basin fill. The ground water occurs in the deposits under unconfined (water-table) conditions with a saturated thickness that ranges from zero along the mountain fronts to more than 8,000 feet in the center of the basin. The amount of recoverable ground water in storage to a depth of 400 feet below the 1978-80 water table is estimated to be about 10 million acre-feet. Depths to water range from about 500 feet near the southern boundary of the study area to about 150 feet in the center of the study area. Ground water enters the area principally as underflow beneath the San Simon and Chukut Kuk Washes and as recharge along the mountain fronts. On the basis of model results, annual inflow to the ground-water system is estimated to be about 4,390 acre-feet. Ground water moves through the study area along paths that encircle a virtually impermeable unit in the basin center, termed 'the lakebed-clay deposits,' and moves westward to an outflow point beneath the Rio Sonoyta south of Cerro La Nariz. Rates of water movement range from less than I foot per year in clays to about 160 feet per year in well-sorted, coarse stream-channel deposits. Transmissivities along the basin margins range from 10,000 to 40,000 feet squared per day, whereas transmissivities in the basin-center lakebed-clay deposits are estimated to be less than 100 feet squared per day. Most Wells that are located along the basin margin and tap more than 300 feet of saturated basin fill in the upper1,000 feet of the aquifer should yield from 500 to 3,000 gallons per minute to properly constructed and developed wells. Specific capacities should range from 10 to 50 gallons per minute per foot of drawdown. The water in the aquifer is moderate to poor in chemical quality for irrigation and public-supply use. The ground water is mainly a sodium bicarbonate type with dissolved-solids concentrations that range from about 250 to 5,000 milligrams per liter and average about 530 milligrams per liter. The poorest quality water is associated with the basin-center lakebed-clay deposits. In most of the basin, the water contains fluoride concentrations that exceed the maximum contaminant levels acceptable for drinking water. Waters from the basin-center lakebed-clay deposits are also anomalously high in dissolved arsenic and unacceptable for public supply. High concentrations of sodium and bicarbonate in the ground water of the study area present potential hazards to most crops, and the use of this type of water requires careful farm-management practices. In 1981 outflow resulting from withdrawals of water from the aquifer was about 23,2'00 acre-feet. Storage is being depleted at a rate of about 19,000 acre-feet per year. On the basis of a mathematical simulation of the groundwater system and withdrawal rates in 1981, storage depletion and drawdown of the water table were projected to 1991. Water-level declines in 199t were estimated to be as much as 20 feet at Papago Farms and more than 40 feet in the area south of the basin-center lakebed-clay deposits. The estimated amount of depletion in 1991 of ground water stored in the upper 400 feet of the aquifer is less than 3.0 percent of the total amou

Arizona, Sonora↗
USGS1981

Silicoflagellate stratigraphy of offshore California and Baja California, Deep Sea Drilling Project, Leg 63.

Quantitative study of middle and upper Miocene silicoflagellate assemblages from Pacific Coast Sites 467 and 469 to 472 has permitted identification of warm- and temperate-water biostratigraphic zones and the formulation of a model for relative paleotemperature values (Ts) on the basis of warm- and temperate-genera abundances. Geographic and temporal trends in Ts for Pacific Coast assemblages are indicated. Three new taxa are described: Dictyocha subclinata Bukry n. sp., Mesocena diodon borderlandensis Bukry n. subsp., and M. hexalitha Bukry, n. sp. The ranges in space and time for several species, such as Dictyocha neonautica var. cocosensis and Distephanus mesophthalmus, are increased. Regionally, barred forms of Distephanus stauracanthus become predominant over ringed forms in the upper part of the middle Miocene Distephanus stauracanthus Subzone.

California↗
USGS1979

Monitoring crustal strain, Cerro Prieto geothermal field, Baja California, Mexico

Significant ground deformation may be occurring in the Cerro Prieto geothermal area, Mexicali Valley, Mexico, as a direct result of extensive withdrawals of geothermal fluid and of continuing tectonism. In order to measure the magnitude and rate of this deformation, three networks of precise geodetic control were established in 1977-78, as part of an international agreement between Mexico and the United States. This report gives the background data for one of these survey nets--a local network of precise horizontal control designed to monitor the horizontal component of ground movement in the area of geothermal production. It represents the first year's effort of a 3-year investigation by the U.S. Geological Survey. It is anticipated that the network of horizontal control will become part of the monitoring program of the Mexican Comision Federal de Electricidad (C.F.E.) for periodic surveys. Fifty-nine lines of precise horizontal control comprising the Cerro Prieto horizontal-control net were established and measured for the first time during January-March 1978. The net encompasses the area of geothermal interest, and spans many of the active local and regional faults. By repeated measurement of the lines in the network, magnitudes and rates of relative ground movement can be calculated. Surveyed control lines of the net tie stations in the geothermal area to bedrock reference stations on Cerro Prieto volcano and four peaks of the Cucapas Mountains. Thus, measured ground movement in the geothermal area can eventually be correlated with regional changes in western Mexicali Valley. To measure accurately the deformation caused by geothermal production and to differentiate this deformation from changes due to other causes are among the challenges of this research program.

Baja California↗
USGS1972

Crust and mantle of the Gulf of Mexico

A SEEMING paradox has puzzled investigators of the crustal structure of the Gulf of Mexico since Ewing et al. 1 calculated that a unit area of the rather thick crust in the gulf contains less mass than does a combination of the crust and enough of the upper mantle to make a comparable thickness in the Atlantic Ocean. They also noted that the free-air gravity of the gulf is essentially normal and fails by a large factor to be low enough to reflect the mass difference that they calculated. We propose a solution to this problem.

Gulf of Mexico↗
USGS1971

A geochemical hypothesis for dolomitization by ground water

Most modern disordered dolomite has been found in dynamic environments. However, solutions associated with modern dolomite formation do not have a common Mg/Ca ratio; the ratio ranges from about 3 to 100. Ground-water circulation may have a significant role in formation of regional dolomites; one of the primary requirements for regional dolomite formation is a large supply of magnesium ions. An X-ray study of well cuttings from the Tertiary limestone aquifer of central Florida indicates that it is composed primarily of calcite and dolomite with minor amounts of quartz and apatite. The magnesium content of the calcite is slightly lower (0-2 percent MgC03) in the recharge areas than in the deeper confined parts of the aquifer system (2-4 percent MgC03). Our data support other recent work and indicate an equilibrium constant for dolomite of 2 X 10-17. Inasmuch as this value is exactly the square of the calcite equilibrium constant (10~8-35), the Mg/Ca ratio must be unity for the three-phase equilibrium, calcite-dolomite-water. The Mg/Ca ratio in water from the aquifer is as low as 0.05 in the recharge area where the water is also undersaturated with respect to both calcite and dolomite. With time and length of travel path in the system, the water increases systematically in Mg/Ca ratio, which approaches unity; saturation with respect to the two carbonates also increases downgradient until the solution apparently becomes over-saturated with respect to both carbonates. In Tertiary limestones of the Yucatan Peninsula, the Mg/Ca range in water is similar to that for Florida. The small amount of magnesium available from the solution of magnesium calcites and dolomite in the potable zone of active circulation is insufficient to provide the amount required for extensive dolomitization unless enormous quantities of rock are available for dissolution. However, dolomite may be forming in the zones of brackish water that underlie the Florida and Yucatan Peninsulas. The required magnesium may be derived from the readily available ocean water or reflux brines as the hydrologic regimen is changed because of relative fluctuations of sea level.

Florida↗
USGS1970

Comparison of chemical hydrogeology of the carbonate peninsulas of Florida and Yucatan

Aquifers of the peninsulas of Florida and northern Yucatan are Tertiary marine carbonate formations showing many lithologic and faunal similarities. In addition, the tropical to subtropical climates of the two areas are similar, each having annual rainfall of about 1000 to 1500 mm. Despite similarities in these fundamental controls, contrasts in the hydrologic and geochemical systems are numerous and striking. For example, Florida has many rivers; Yucatan has none. Maximum thickness of fresh ground water in Florida is about 700 meters; in the Yucatan it is less than 70 meters. In Florida the gradient of the potentiometric surface averages about 1 meter per kilometer; in the Yucatan it is exceedingly low, averaging about 0.02 meter per kilometer. In Florida the chemical character of water changes systematically downgradient, owing to solution of minerals of the aquifer and corresponding increases in total dissolved solids, sulfate, calcium, and Mg-Ca ratio; in the Yucatan no downgradient change exists, and dominant processes controlling the chemical character of the water are solution of minerals and simple mixing of the fresh water and the body of salt water that underlies the peninsula at shallow depth. Hydrologic and chemical differences are caused in part by the lower altitude of the Yucatan plain. More important, however, these differences are due to the lack of an upper confining bed in Yucatan that is hydrologically equivalent to the Hawthorn Formation of Florida. The Hawthorn cover prevents recharge and confines the artesian water except where it is punctured by sinkholes, but sands and other unconsolidated sediments fill sinkholes and cavities and impede circulation. In the Yucatan the permeability of the entire section is so enormous that rainfall immediately infiltrates to the water table and then moves laterally to discharge areas along the coasts.

Florida Peninsula, Yucatan Peninsula↗
USGS1967

Historic surface faulting in continental United States and adjacent parts of Mexico

This report summarizes geometric aspects of approximately 35 instances of historic faulting of the ground surface in the continental United States and adjacent parts of Mexico. This information is of immediate importance in the selection and evaluation of sites for vital structures such as nuclear power plants. The data are presented in a table and graphs which show the quantitative relations between various aspects of the faulting. Certain items in the table that are uncertain, poorly known, or not in the published literature are briefly described in the text.

Open-File Report↗
USGS1963

Effects of drought in the Rio Grande basin: Chapter D in Drought in the Southwest, 1942-56

In headwater areas of the Rio Grande and its principal tributaries, variations in streamflow and in ground-water storage and discharge depend upon fluctuations in precipitation, with modifications by geologic factors and by the pattern of water development and use. In downstream areas the surfaceand ground-water resources are replenished not only by local precipitation but also by outflow from the headwaters areas; thus the effects of drought upon those water resources are complex and may be vague and indeterminate.

Colorado, New Mexico, Texas↗