Geology topics
Research about Texas
Source-linked reports with geographic coverage including Texas.
Techniques for estimating the magnitude and frequency of floods in the Dallas - Fort Worth metropolitan area, Texas
Equations for predicting the magnitude and frequency of floods in the Dallas-Fort Worth metropolitan area were developed from recorded data from streams with drainage areas ranging in size from 1.25 to 66.4 square miles. The U. S. Geological Survey urban rainfall-runoff model was used to generate long-term flood-discharge record for gaged streams in the area. Simulated and recorded annual-peak data were subjected independently to log Pearson III frequency analyses. The results were weighted to determine appropriate discharges for selected 2-, 5-, 10-, 25-, 50-, and 100-year recurrence intervals. These T-year values were then used as the dependent variables in a multiple regression analysis. The independent variable determined to be statistically significant and retained in the resulting equations were drainage area and an urbanization index that expresses the degree of urban development. Analysis of the results shows that a land-use change from rural to fully urbanized is accompanied by a 180% increase in discharge of a flood with a 5-year recurrence interval and about 100% increase in discharge of a flood with a 100-year recurrence interval.
Source areas of salinity and trends of salt loads in streamflow in the upper Colorado River, Texas
A series of seven studies of the quality and quantity of low flows in a 35.5-mile reach of the Colorado River upstream from Colorado City, Tex., were made from February 1975 to March 1978 to delineate areas of saline inflows. These studies showed generally that ground water contributed throughout the reach is saline but that loads of dissolved-constituents in ground-water accretions are highest in three subreaches. Yields per mile of river channel from these subreaches during the low-flow studies averaged more than 5.5 tons of dissolved solids per day, of which more than 1.8 tons were sodium and 2.9 tons were chloride. Salt-load trend studies for three long-term continuous streamflow and daily water-quality stations show that the salinity of the flow upstream from Ira, Tex., {mile 826.3) increased significantly after 1963 but decreased significantly after 1970. Part of the reach upstream from Ira is proximate to oil fields, the production and open-pit disposal of oilfield brines in the area increased significantly in the early 1960's, but a ban on open-pit disposal was enacted in 1969. No significantly downward trend in the salinity of flow at other daily water-quality stations downstream from Ira occurred after the ban on open-pit disposal of oil-field brines. The low-flow and salt-load trend studies indicate that part of the salinity in the flow of the Colorado River has resulted from the inflow of oil-field brine, but preponderant evidence indicates that the major part of the salinity is of natural origin. Neither the ban on open-pit disposal nor pumping of saline ground water has significantly reduced the salinity of flow downstream from Cuthbert, Tex. {mile 810.6). Diversion of saline low flows from the Colorado River at mile 799.3 upstream from Colorado City since January 1969 has resulted in significant improvement in the quality of water. Decreases in the discharge-weighted averages of dissolved solids and of chloride in the flow of the Colorado River at Colorado City (mile 796.3) during the 1969-78 water years were about 420 milligrams per liter and 280 milligrams per liter, respectfully.
Organophosphate insecticide poisoning of Canada geese in the Texas panhandle
Sixteen hundred waterfowl, mostly Canada Geese, died near Etter, Texas, in late January 1981 from anticholinesterase poisoning. Winter wheat in the area of the die-off had been treated with organophosphate insecticides to control greenbugs. Cholinesterase (ChE) levels in brains of a sample of geese found dead were 75% below normal, enough to account for death (Ludke et al. 1975). The gastrointestinal (G I) tracts of geese found dead were packed with winter wheat; gas chromatography techniques identified parathion and methyl parathion in the GI tract contents. Residues of both chemicals were confirmed by mass spectrometry. We recommend that less toxic materials, such as malathion, be used on grain crops when waterfowl are in the vicinity of treatment.
Compilation of hydrologic data for the Edwards Aquifer, San Antonio area, Texas, 1934-80
No abstract available.
Assessing mesquite-grass vegetation condition from Landsat
Landsat multispectral scanner (MSS) band values, band ratios, and vegetation index models were compared with selected rangeland vegetation parameters collected at six test sites within the honey mesquitellotebushlmixed grass association in north-central Texas. The comparisons at four dates showed that two vegetation index models, TV16 and GVI, are highly correlated (P = 0.01) with green yield, green cover, and plant moisture content. The green vegetation index (GVZ) developed by Kauth and Thomas (1976), was highly correlated and superior to other models in relationship to wet green yield, dry green yield, and cured vegetation cover. TV16, developed by Rouse et al. (1974), was more highly correlated with green vegetation cover and vegetation moisture content. Both TV16 and GVI are superior to other models in their relationship with green cover. None of the Landsat MSS parameters tested was significantly correlated with dry total yield, percent bare ground, or moisture of the soil measured at the surface or at a 20 cm depth. I t is concluded that Landsat MSS data are sensitive to seasonal changes in vegetation growth conditions and inherent ecological differences within a relatively unqorm vegetationlsoil system.
The occurrence of the Complexiopollis-Atlantopollis zone (Palynomorphs) in the Eagle Ford Group (Upper Cretaceous) of Texas
The Lower and lower Upper Cretaceous palynological zones defined in the Atlantic Coastal Plain Province and which occur in the eastern Gulf Coastal Plain Province are characterized by a paucity of marine invertebrate fossils. As a result, correlation of these zones with European and provincial stages, as well as with other microfossil and megafossil zones is tenuous. However, an examination of a complete section of the Eagle Ford Group and adjacent strata in Texas reveals that: 1) the upper part of the Woodbine Formation and the Tarrant Formation of the overlying Eagle Ford Group represent a biostratigraphic interval that is absent in the Atlantic and eastern Gulf Coastal Plain Provinces; 2) the Complexiopollis-Atlantopollis Zone (zone IV of some authors) occurs within the Britton Formation (Eagle Ford Group), and is equivalent to the upper part of the Rotalipora cushmani-greenhornensis Subzone (planktic foraminifers) and possibly to the Sciponoceras gracile Zone (ammonites); 3) the Arcadia Park Formation (Eagle Ford Group) contains a mixed assemblage of palynomorphs that includes guides to both the Complexiopollis-Atlantopollis and the overlying Complexiopollis exigua-Santalacites minor Zones, suggesting that biostratigraphic equivalents of the Arcadia Park Formation are not represented in the Atlantic and eastern Gulf Coastal Plain Provinces; and 4) in the basal part of the Austin Chalk of Texas, only one guide palynomorph to the Complexiopollis-Atlantopollis Zone was recognized, but guides to the Complexiopollis exigua-Santalacites minor Zone are present. The Tuscaloosa Group of the eastern Gulf Coastal Plain appears to be biostratigraphically equivalent to the Complexiopollis-Atlantopollis Zone, and therefore correlative with the middle to upper part of the Britton Formation of the Eagle Ford Group.
Development of the benethic nepheloid layer on the south Texas continental shelf, western Gulf of Mexico
A monitoring study of suspended sediment on the South Texas Continental Shelf indicates that a turbid benthic nepheloid layer is regionally persistent. A sequence of quasi-synoptic measurements of the water column obtained during six cruises in an 18-month period indicates substantial spatial and temporal variability in nepheloidlayer characteristics. Regionally, the thickness of the shelf nepheloid layer increases both seaward and in a convergent alongshelf direction. Greatest thicknesses occur over a muddy substrate, indicating a causal relationship; maximum observed local thickness is 35 m which occurs along the southern shelf break. Analyses of suspended particulate matter in shelf bottom waters indicate mean concentrations ranging from 49 · 10 4 to 111 · 10 4 particle counts/cc; concentrations persistently increase shoreward throughout the region. Bottom particulate matter is predominantly composed of inorganic detritus. Admixtures of organic skeletal particles, primarily diatoms, are generally present but average less than 10% of the total particulate composition. Texturally, the particulate matter in bottom waters is predominantly poorly sorted sediment composed of very fine silt (3.9–7.8 μm). The variability in nepheloid-layer characteristics indicates a highly dynamic shelf feature. The relationship of nepheloid-layer characteristics to hydrographic and substrate conditions suggests a conceptual model whereby nepheloid-layer development and maintenance are the results of the resuspension of sea-floor sediment. Bottom turbulence is attributed primarily to vertical shear and shoaling progressive internal waves generated by migrating shelf-water masses, especially oceanic frontal systems, and secondarily to shoaling surface gravity waves.
Laser fluorometric analysis of plants for uranium exploration
A preliminary test of biogeochemical exploration for locating uranium occurrences in the Marfa Basin, Texas, was conducted in 1978. Only 6 of 74 plant samples (mostly catclaw mimosa, Mimosa biuncifera ) contained uranium in amounts above the detection limit (0.4 ppm in the ash) of the conventional fluorometric method. The samples were then analyzed using a Scintrex UA-3 uranium analyzer ∗ - an instrument designed for direct analysis of uranium in water, and which can be conveniently used in a mobile field laboratory. The detection limit for uranium in plant ash (0.05 ppm) by this method is almost an order of magnitude lower than with the fluorometric conventional method. Only 1 of the 74 samples contained uranium below the detection limit of the new method. Accuracy and precision were determined to be satisfactory. Samples of plants growing on mineralized soils and nonmineralized soils show a 15-fold difference in uranium content; whereas the soils themselves (analyzed by delayed neutron activation analysis) show only a 4-fold difference. The method involves acid digestion of ashed tissue, extraction of uranium into ethyl acetate, destruction of the ethyl acetate, dissolution of the residue in 0.005% nitric acid, and measurement.
Evaluation of Landsat Multispectral Scanner data for mapping vegetated soil landscapes
Landsat multispectral scanner data for Brazos County, Texas, were evaluated in terms of effectiveness for classifying soils on vegetated landscapes at three times during the year: a time of normally adequate soil water, a time of expected soil water deficit, and a time when soil water is normally being replenished. Six test sites were used to evaluate LARSYS supervised and unsupervised classification of vegetated soil landscapes. Open grassland soils were best separated in the fall during a period when soil moisture was being replenished after the summer period of soil water deficit. Woodland soils were separated by Landsat data in late spring when adequate moisture was available. However, a high degree of accuracy was not achieved using Landsat for separating soil map units. Accurate separation of soil mapping units on vegetated landscapes was not possible during late summer when soil water was deficient. Selected soil properties important to plant growth were separable on the test sites using June and October Landsat data. Particle size and soil moisture regime were separated at both dates. Soils with argillic horizons were separated from soils without argillic horizons.
Naturally occurring and experimentally induced castor bean (Ricinus communis) poisoning in ducks
Castor bean ( Ricinus communis ) poisoning accounted for the death of several thousand ducks in the Texas panhandle in the fall and winter months of 1969-1971. Signs of intoxication resembled those of botulism, except for mucoid, blood-tinged excreta. The most common lesions were severe fatty change in the liver, widely distributed internal petechial hemorrhages or ecchymoses, and catarrhal enteritis. Nearly intact castor beans were found in the stomach of one duck during field necropsy. Fragments of seed coat resembling castor bean were found in the stomachs of 10 of 14 ducks examined in the laboratory. Clinical signs and postmortem lesions observed in wild ducks were induced experimentally in mallards ( Anas platyrhynchos ) by force-feeding intact castor beans. Toxicity titrations were erratic, but the LD50 appeared to be between three and four seeds. The mouse toxicity test, used to detect Clostridium botulinum toxin in the blood serum of intoxicated ducks, was negative in every case. Hemagglutination and precipitin tests generally failed to detect castor bean in extracts of excreta or intestinal contents of experimentally intoxicated ducks.
Weather conditions associated with beginning of northward migration departures of snow geese
No abstract available.