Geology topics
Source-linked reports with geographic coverage including Texas.
The Tessey Formation in the Frenchman Hills, northwest Glass Mountains, represent deposition in a basinal setting. The formation consists of at least two shallowing-upward sequences of carbonate and evaporite deposition marked by two episodes of subaerial exposure, meteoric water dissolution, and collapse brecciation.
Compared to the Guadalupe Mountains of Texas and New Mexico the depositional environments of the Permian strata of the Glass Mountains (and adjacent Del Norte Mountains) are less well known. In general, the Guadalupian facies in the the Glass and Del Norte mountains changes from predominantly carbonate facies in the northeast to thicker clastic facies in the southwest. Philip B. Kind (1931) originally considered this trend to reflect an uplifted clastic source to the southwest, with carbonate facies developing away from the source area. Ross (1986) interpreted the eastern portion of the Road Canyon and Word formations to consist the shelf, shelf-edge bioherm, and reef facies, and the southwest area to consist of deeper water siliceous shale, clastic limestone, and basinal sandstone facies. Probably the best known controversy in the Glass Mountains involves the depositional environment of the Skinner Ranch Formation (Leonardian according to Ross, 1986; Wolfcampian according to Cooper and Grant, 1972) at its type section on Leonard Mountain. Cooper and Grant (1964) identified in situ patch reefs at the base of the section, which were subsequently interpreted as displaced limestone blocks deposited in a slope environment (Rogers, 1972; Cys and Mazzullo, 1978; Ross, 1986). Later Flores, McMillan, and Watters (1977) interpreted the same units as subtidal and intertidal deposits. The Skinner Ranch Formation illustrates the complexities involved in interpreting the paleogeography of the Glass Mountains. If the Sinner Ranch contains displaced blocks, some eroded from older units, it explains the occurrence of Wolfcampian fossils in the Skinner Ranch (Ross, 1986).The slop facies interpretation also is used to place the shelf edge at that time between Skinner Ranch outcrops at Leonard Mountain and the lagoonal, backreef deposits of the Hess Formation to the east, although most of the actual shelf edge is not preserved (Ross, 1987:30). Similar conflicting interpretations exist in younger rocks in the western facies of the Leonardian Guadalupian to the southwest in the Del Norte Mountains. Ross (1986, 1987) considered the western facies of the Road Canyon and Word formations to be basinal shales and turbidites. Wardlaw et al. (1990) and Rohr et al. (1987) have interpreted this area to be shallow intertidal to lagoonal environments adjacent to an uplifted area to the south. The type section of the Road Canyon Formation is also a subject of disagreement and will be discusses in more detail later.
The Guadalupian rocks of the northern Del Norte Mountains were deposited in a foreland basin between land of the Marathon orogen and a carbonate shoal established on the geanticline separating the foreland basin from the Delaware basin. Deposition was alternately influenced by coarse clastic input from the orogen and carbonate shoal, which interrupted shallow basinal siltstone depletion. Relatively deeper-water deposition is characterized by carbonate input from the shoal, and relatively shallow-water deposition is characterized by sandstone input from the orogen. Deposition was in five general transgressive-regressive packages that include (1) the Road Canyon Formation and the first siltstone member and first sandstone member of the Word Formation, (2) the second siltstone member, Appel Ranch Member, and limy sandy siltstone member of the Word Formation, (3) the Vidrio Formation, (4) the lower and part of the middle members of the Altuda Formation, and (5) part of the middle and upper members of the Altuda Formation.
Spontaneous mastocytomas studied in 18 axolotls ( Ambystoma mexicanum ) and six tiger salamanders ( Ambystoma tigrinum ) were gray-white, uni- to multilobular cutaneous protrusions from 2 mm to 2 cm in diameter. Tumors were moderately cellular unencapsulated masses that usually infiltrated the dermis and hypodermis with the destruction of intervening tissues. Some tumors were invading superficial bundles of the underlying skeletal muscle. Tumors consisted of mitotically active cells derived from a single lineage but showing a range of differentiation. Immature cells had nearly smooth to lightly cleft or folded basophilic nuclei bordered by a band of cytoplasm with few cytoplasmic processes and containing a few small uniform eccentric granules. Mature cells had basophilic nuclei with deep clefts or folds and abundant eosinophilic cytoplasm with multiple long intertwining cytoplasmic extensions packed with metachromatic granules. The axolotls were old individuals from an inbred laboratory colony. The tiger salamanders were wild animals from a single polluted pond. They could have been old and inbred. Both groups were neotenic. These are the first mastocytomas discovered in cold-blooded animals.
The Edwards aquifer is the sole source of public water supply for more than 1 million people in the San Antonio area and supplies large quantities of water for agriculture, industry, and the military. The dissolutioned, faulted limestone aquifer is the major source of water for Bexar, Comal, Hays, Medina, and Uvalde Counties. The annual compilation of estimates of recharge to and discharge from the Edwards aquifer is part of a continuing program of the U.S. Geological Survey (USGS) in cooperation with the Edwards Aquifer Authority (EAA).
Water quality in the Trinity River basin was studied during 1992-95 as part of the USGS National Water-Quality Assessment (NAWQA) Program. Studies included chemical sampling of streams, streambed sediments, biota, and ground water; measuring distributions of biological communities in streams; and measuring physical characteristics of streams that affect biological habitat. The sampling design, in general, relates water-quality conditions to causative human and natural environmental factors. The occurrence of pesticides, for example, is related to land use. Trends are mixed, with a substantial improvement in the diversity of fish species downstream from Dallas and large decreases in regulated contaminants such as DDT; but increases in unregulated contaminants such as polychlorinated biphenyls.
In 1997, the Texas Legislature passed a comprehensive revision to the Texas Water Code. This legislation (Senate Bill 1) changed water planning in Texas from a statewide to a regional activity. By September 2001, the 16 regions created by Senate Bill 1 must produce water plans to address their water needs during drought-of-record conditions, and must identify water-management strategies for periods when streamflows, reservoir storage, and groundwater levels are 50 and 75 percent of normal.
The U.S. Geological Survey (USGS) operates a network of streamflow-gaging stations in Texas that provides discharge data used for water-management decisions and various other purposes. Operating stations at all locations where discharge data are needed is not feasible, but the statistical characteristics of the network station data can be used to estimate discharge characteristics at ungaged sites. Regionalization techniques such as regression analyses relate discharge-frequency characteristics to selected physical and climatic characteristics of drainage basins. A particular discharge-frequency characteristic that can be regionalized is the minimum 7-day, 2-year discharge1 (7Q2). In Texas, the 7Q2 is used at stream sites to analyze permit applications for water allocation, water-supply planning, aquatic maintenance (instream flow) requirements, and waste-load allocation for point and nonpoint source discharges.
Surface-water sampling protocols of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program specify samples for most properties and constituents to be collected manually in equal-width increments across a stream channel and composited for analysis. Single-point sampling with an automated sampler (autosampler) during storms was proposed in the upper part of the South-Central Texas NAWQA study unit, raising the question of whether property and constituent concentrations from automatically collected samples differ significantly from those in samples collected manually. Statistical (Wilcoxon signed-rank test) analyses of 3 to 16 paired concentrations for each of 26 properties and constituents from water samples collected using both methods at eight sites in the upper part of the study unit indicated that there were no significant differences in concentrations for dissolved constituents, other than calcium and organic carbon.
Town Lake, the last in the chain of Highland Lakes on the Colorado River, runs through the center of Austin, Texas. On any given day, grebes and coots dot the water, rowers skim alongside, and the sparkle of the sun on the water can be admired from the adjacent hike and bike path and from the windows of nearby office buildings. During the summer months, crowds gather along the shores of Town Lake to watch as many as 1 million Mexican Free-Tail bats emerge from under the Congress Avenue bridge. But below the lazily moving azure water lies a bed of sediment about 1 meter (m) thick?sediment that has been deposited gradually since the reservoir was formed in 1959 and that has been recording changes in water quality since that time. What can this sediment tell us about the history of water quality in the Colorado River? And what does it say about the effects of the rapid urbanization of Austin and the future health of our environment?
This report is one in an annual series of reports that depicts water-level altitudes and water-level changes since 1977 and compaction since 1973 in the Chicot and Evangeline aquifers in the Houston-Galveston region, Texas. The report, prepared in cooperation with the City of Houston and the Harris-Galveston Coastal Subsidence District, presents maps for the Chicot and Evangeline aquifers showing the approximate water-level altitudes in wells in 1999 and approximate water-level changes in wells from 1977 to 1999 and from 1998 to 1999, a map showing extensometer site locations, and graphs showing measured compaction of subsurface material at selected sites from 1973 to 1998. The most recent previously published water-level-altitude maps and water-level-change maps for the two aquifers in the region are by Coplin (1998). The Houston-Galveston region comprises Harris and Galveston Counties and adjacent parts of Brazoria, Fort Bend, Waller, Montgomery, Liberty, and Chambers Counties.
This report summarizes in table format 32 aquatic vertebrate (primarily fish), 54 aquatic invertebrate, and 13 aquatic plant studies available for the area of the South-Central Texas study unit of the U.S. Geological Survey National Water-Quality Assessment. The studies, published mostly during 1973–97, pertain to the Guadalupe, San Antonio, and Nueces River Basins, the San Antonio-Nueces and Nueces-Rio Grande Coastal Basins, and the Edwards aquifer where it underlies the upper parts of the three river basins. The biology of the study-unit streams is determined mostly by the characteristics of the ecoregions they transect—the Edwards Plateau, Texas Blackland Prairies, East Central Texas Plains, Western Gulf Coastal Plain, and Southern Texas Plains. About 20 percent of the previous fish and invertebrate studies and about 75 percent of the aquatic plant surveys have centered on Comal Springs in Comal County and San Marcos Springs in Hays County. Although several important studies are available for the San Antonio region, documentation of aquatic biology for the remainder of the study unit is relatively sparse. The streams in the study unit, particularly in the Edwards Plateau, support three dominant biological groups—fish, aquatic invertebrates, and plants. Potential threats to these organisms include impoundments and flood-control projects, siltation from erosion, ground-water pumping, recreational activities, wastewater discharge, and introduction of non-native species. More than 30 non-native fish, invertebrate, and plant species have been introduced into the region. Of the 19 aquatic species Federally listed as endangered or threatened in Texas, 8 are associated with springs and spring runs in the study unit. All of the endangered species in the study unit are associated with springs and spring runs. A large number of endemic species in the study unit are associated with subterranean aquatic ecosystems, most likely a consequence of the unique proximity of the varied topographic and hydrologic conditions of the area and of the geological development of the Edwards aquifer. Ninety-one endemics, including 44 species found solely underground, are associated with the aquatic ecosystems (including springs) of the Edwards aquifer.
Encroachment of urban development on the outcrop of the Edwards aquifer (the recharge zone), particularly in Bexar County, has raised the issue of possible contamination of water that enters the aquifer. Increasing residential and commercial development on the recharge zone increases the potential for runoff containing toxic substances, oil spills, or leakage of hazardous materials to contaminate the regional drinking water supply. The Edwards aquifer is a dipping sequence of extensively faulted, fractured, and dissolutioned limestone and dolostone that yields large quantities of water to wells and springs. The recharge zone is essentially coincident with the area in which the aquifer crops out. Recharge to the aquifer is derived mainly from seepage from streams crossing the recharge zone and by direct infiltration of precipitation on the outcrop. In 1996, the U.S. Geological Survey, in cooperation with the Edwards Aquifer Authority and the Nature Conservancy of Texas, began a study to compare stormwater runoff from two sites in the recharge zone in watersheds of similar size and different land use. One site is located on Lorence Creek, a tributary to Salado Creek in northern Bexar County, and the other site is on an unnamed tributary of the Frio River in northern Uvalde County (fig. 1). Flow at the two sites results only from storm runoff. Both watersheds have similar climate, topography, soils, and vegetation. Land use in the Lorence Creek watershed is primarily single-family residential, commercial, and transportation. Land use in the watershed of the Frio River tributary is primarily rangeland. The drainage area of each watershed is less than 2 square miles.
Geologic and hydrologic data for the Municipal Solid Waste Landfill Facility on the U.S. Army Air Defense Artillery Center and Fort Bliss in El Paso County, Texas, were collected by the U.S. Geological Survey in cooperation with the U.S. Department of the Army. The 106.03-acre landfill has been in operation since January 1974. The landfill contains household refuse, Post solid wastes, bulky items, grass and tree trimmings from family housing, refuse from litter cans, construction debris, classified waste (dry), dead animals, asbestos, and empty oil cans. The depth of the filled areas is about 30 feet and the cover, consisting of locally derived material, is 2 to 3 feet thick. Geologic and hydrologic data were collected at or adjacent to the landfill during (1) drilling of 10 30- to 31-foot boreholes that were completed with gas-monitoring probes, (2) drilling of a 59-foot borehole, (3) drilling of a 355-foot borehole that was completed as a ground-water monitoring well, and (4) in situ measurements made on the landfill cover. After completion, the gas- monitoring probes were monitored on a quarterly basis (1 year total) for gases generated by the landfill. Water samples were collected from the ground-water monitoring well for chemical analysis. Data collection is divided into two elements: geologic data and hydrologic data. Geologic data include lithologic descriptions of cores and cuttings, geophysical logs, soil- gas and ambient-air analyses, and chemical analyses of soil. Hydrologic data include physical properties, total organic carbon, and pH of soil and sediment samples; soil-water chloride and soil-moisture analyses; physical properties of the landfill cover; measurements of depth to ground water; and ground-water chemical analyses. Interpretation of data is not included in this report.
The coal-bearing Gulf of Mexico Coastal Plain of North America contains a variety of depositional settings and coal types. The coal-bearing region extends westward from Alabama and Mississippi, across Louisiana to the northern part of the Mississippi Embayment, and then southward to eastern Arkansas, Texas and northern Mexico (fig. 1). Most of the coal currently mined in Texas is lignite from the upper part of the Wilcox Group (Paleocene-Eocene) and, in Louisiana, lignite is mined from the lower part of the Wilcox (fig. 2). Gulf Coast coal is used primarily as fuel for mine-mouth electric plants. On this field trip we will visit the only two non-Wilcox coal mining intervals in the Texas-Louisiana Coastal Plain; these include the San Pedro - Santo Tomas bituminous cannel-like coal zone of the Eocene Claiborne Group, and the San Miguel lignite coal zone of the Eocene Jackson Group (fig. 2). Other coal-mining areas in northern Mexico are currently producing bituminous coal from the Cretaceous Olmos Formation of the Navaro Group (fig. 2).
The lower unit of the Chicot aquifer is a major source of freshwater for Orange County, Texas. In 1989, the average rate of ground-water withdrawal from the lower unit of the Chicot aquifer in Orange County for municipal and industrial use was 13.8 million gallons per day, a substantial decrease from the historical high of 23.1 million gallons per day in 1972. The average withdrawal for industrial use decreased substantially from 14.4 million gallons per day during 1963-84 to 6.9 million gallons per day during 1985-89. The average withdrawal for municipal use during 1985?89 was 6.8 million gallons per day, similar to the average withdrawal of 5.8 million gallons per day during 1963-84. Water levels in wells in most of the study area rose during 1985?90. The largest rise in water levels was more than 10 feet in parts of Orange and Pinehurst, north of site B (one of three areas of ground-water withdrawal for industrial use), while the largest decline in water levels was a localized decline of more than 60 feet at site C in south-central Orange County (also an area of withdrawal for industrial use). Chemical analyses of ground-water samples from the lower Chicot aquifer during 1985-90 indicate that the aquifer contained mostly freshwater (dissolved solids concentrations less than 1,000 milligrams per liter). Dissolved chloride concentrations remained relatively constant in most wells during 1985-90 but could vary greatly between wells within short distances. Saline-water encroachment continued to occur during 1985?89 but at a slower rate than in the 1970s and early 1980s. On the basis of chemical data collected during 1985?89, a relation was determined between specific conductance and dissolved chloride concentration that can be used to estimate dissolved chloride by multiplying the specific conductance by different factors for low or high conductances.
As of September 30, 1998, the surface-water data-collection network of Texas (table 1) included 313 continuous-recording streamflow stations (D), 22 gage-height record only stations (G), 23 crest-stage partial-record stations (C), 39 flood-hydrograph partial-record stations (H), 25 low-flow partial-record stations (L), 1 continuous-recording temperature station (M1), 25 continuous-recording temperature and conductivity stations (M2), 3 continuous-recording temperature, conductivity, and dissolved oxygen stations (M3), 13 continuous-recording temperature, conductivity, dissolved oxygen, and pH stations (M4), 5 daily chemical-quality stations (Qd), 133 periodic chemical-quality stations (Qp), 16 reservoir/lake surveys for water quality (Qs), and 70 continuous or daily reservoir-content stations (R). Plate 1 identifies the major river basins in Texas and shows the location of the stations listed in table 1.