Download or read book Edwards Formation Lower Cretaceous Texas written by James B. Zimmerman and published by . This book was released on 1968 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Edwards Formation lower Cretaceous Texas written by William Lawrence Fisher and published by . This book was released on 1969 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Edwards Formation Surface and Subsurface Central Texas written by Peter R. Rose and published by . This book was released on 1968 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the subsurface of south-central Texas the Lower Cretaceous Edwards Formation consists of about 400 to about 600 feet of porous dolomite and limestone that accumulated on the Comanche shelf as shallow marine, intertidal and supratidal deposits. The Edwards thickens southwestward to about 1000 feet near the Maverick basin and thins northeastward by facies change to zero in the North Texas-Tyler basin. In between, on the San Marcos platform, it is separated into the Kainer Member (new) below and the Person Member (new) above by a thin, widely traceable argillaceous layer called the Regional Dense Bed, the base of which is the conformable Person-Kainer boundary. The Edwards is conformable with the Glen Rose Formation below and disconformable with the Georgetown Formation above. The overlying Georgetown, Del Rio, and Buda formations consist chiefly of lime mud and represent marine open shelf deposition. To the northeast the Kainer grades into the classic Walnut/Comanche Peak/Edwards sequence of the north Texas type area, and the Person grades into the lower Duck Creek Member of the Georgetown. To the southwest the Kainer and Person members pass into the Devils River Formation. At the surface in the eastern Edwards Plateau of central Texas the Edwards Formation consists of about 400 to about 650 feet of dolomite and limestone similar to that of the subsurface Kainer and Person members; it thickens southward from the Central Texas platform and grades into rudist limestone of the Devils River Formation. The Edwards is separated into the Fort Terrett Member (new, after Lozo and Smith) below and the Segovia Member (new) above, separated by a thin, widely traceable marly layer called the Doctor Burt Bed, at the base of the Segovia. The Glen Rose-Edwards, Edwards-Del Rio, and Del Rio-Buda boundaries are disconformable, but the Fort Terrett-Segovia boundary is conformable. The Georgetown is absent, probably by erosion and non-deposition, and thin Del Rio and Buda formations consist of marine open shelf deposits. Southeastward across the Edwards Plateau the lower Doctor Burt Bed acquires miliolid and rudistid limestone at the expense of marl so that only a thin marly layer remains at the top as the Edwards goes into the subsurface; this is the Regional Dense Bed. From northeast to southwest Edwards and equivalent units form two complete carbonate facies complexes. The lower (Fredericksburg) complex reflects extremely shallow water, high salinities and low subsidence rates. The upper (Lower Washita) complex is a facies assemblage more like the standard carbonate model, with low-angle clinoforms along the subsiding basin margins and increasing dolomite toward the Central Texas platform. Upper Washita open shelf units filled in and then blanketed Lower Washita topography. Dolomite is confined chiefly to restricted shallow marine, intertidal, and supratidal deposits, which are controlled chiefly by positive tectonic elements. Collapse breccias were caused by solution and removal of gypsum shortly after deposition. Crystalline limestone is related to Cretaceous exposure, present weathering, and alteration beneath dissolving gypsum. Pulverulite is related to contemporary weathering. The subsurface Edwards is porous toward the top, related to early exposure of mobile fault blocks and to the unconformity at the top of the formation. The surface Edwards is porous throughout; cavernous porosity and permeability at the base produces a widespread, effective aquifer. Ground water probably is enhancing porosity now. Through Fredericksburg and Washita time facies tracts shrank back onto higher parts of the Central Texas platform as it was progressively inundated during deposition of three units of successively deeper-water sediments.

Download or read book Geology of the Edwards Plateau and the Rio Grande Plain Adjacent to Austin and San Antonio Texas written by Robert Thomas Hill and published by . This book was released on 1898 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comanchean Lower Cretaceous Stratigraphy and Paleontology of Texas written by Society of Economic Paleontologists and Mineralogists. Permian Basin Section and published by . This book was released on 1967 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Time rock correlations and biofacies of the lower Cretaceous Edwards limestone South Central Texas written by Paul Odom Harvard and published by . This book was released on 1962 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Diagenesis of the lower cretaceous Edwards group in the Balcones Fault Zone Area South Central Texas written by Patricia Mench Ellis and published by . This book was released on 1985 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Geologic Framework and Hydrogeologic Characteristics of the Edwards Aquifer Uvalde County Texas written by Allan K. Clark and published by . This book was released on 2003 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sedimentology and Cyclivity of the Lower Cretaceous Edwards Group West central Texas written by Francisco Javier Cardona-Sánchez and published by . This book was released on 2003 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Bibliography of the Edwards Aquifer Texas Through 1993 written by and published by . This book was released on 1995 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Stratigraphic Studies of the Lower Cretaceous Rocks of Brewster County Texas written by Ervin Samuel Becker and published by . This book was released on 1956 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development and diagenesis of a Lower Cretaceous bank complex Edwards Limestone north Central Texas written by Ralph Spaulding Kerr and published by . This book was released on 1976 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Petrographic Study of the Edwards and Associated Limestones lower Cretaceous of Real County Texas written by Sam Park and published by . This book was released on 1959 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Nature of the Cretaceous Precretaceous Contact Central Texas written by and published by . This book was released on 1979 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Population Studies of the Brachiopod Kingena Wacoensis Occurring in the Lower Cretaceous Georgetown Formation of Central Texas written by James William Dixon and published by . This book was released on 1955 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Field Guide to Lower Cretaceous Carbonate Strata in the Moffatt Mound Area Near Lake Belton Bell County Texas written by David L. Amsbury and published by . This book was released on 1984 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Hydrogeology of the Lower Cretaceous Edwards and Trinity Group Formations Near Junction Kimble County Texas written by Stephen Robert Allen and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study describes ground-water flow in the Lower Cretaceous formations near Junction (Kimble County), Texas. Rock exposures were examined throughout the 150-mile study area to determine the nature and distribution of permeable features. Dominant features include nearly vertical fractures and horizontal bedding planes in carbonate rocks of the Edwards Group formations (Edwards), and coarse-grained fluvial channel deposits in the underlying Hensel Sand Formation (Hensei). Static water levels were measured in over one hundred wells and contoured to reveal the existence of two separate potentiometric surfaces, one overlying the other. Preliminary, but useful estimates of transmissivity, hydraulic conductivity, and ground-water velocity were derived using specific capacities from eighty-three wells completed in both the upper (Edwards) and lower (Hensel) aquifers. At the edge of the Edwards Plateau where the contact between the Edwards and the Hensel is exposed on the face of the erosional escarpment, ground water discharges from the Edwards aquifer through numerous low volume springs and seeps. An even greater proportion of ground-water discharge leaks from the Edwards aquifer to the underlying Hensel aquifer across a thin low permeability bed at the base of the Edwards which consists of marly, unfractured, nodular limestone. The sum of these two components of discharge is approximately equal to precipitation recharge to the Edwards. To gain additional insight into cross-formational flow an analysis of major and minor ions, redox potential, and dissolved oxygen was conducted for twenty-one water wells which were located along three north-south (inferred flow direction) transects. The Edwards waters were found to be a Ca-Mg-HC03 facies; the Hensel waters, a mixed facies. This difference in hydrochemical facies was initially thought to be caused by ion evolution along flowpaths, but it more likely reflects the existence of a regional aquifer below a locally constrained aquifer. High values of dissolved oxygen and redox potential in the Edwards aquifer indicate that recharge is predominant; lower values of these parameters in the Hensel aquifer indicate that this water occurs in an intermediate or discharge zone. To test the conceptual model of steady-state ground-water flow, a numerical model was constructed using the MODFLOW finite-difference computer code. Over one hundred trial and error simulations were executed to calculate leakage through the confining bed, discharge from springs, and discharge to the Llano River. In addition, the distribution and magnitude of focused recharge to the Edwards aquifer was calculated, estimates were made for unknown hydrogeologic parameters, and the Edwards aquifer was demonstrated to be fully perched above the Hensel aquifer. The increased understanding of the ground-water flow regime resulting from this study will support range management activities and improve the success rate of water well drilling.