Geological Circulars

Permanent URI for this collectionhttps://hdl.handle.net/2152/121888

Peer-reviewed geoscience research summaries, targeted on Bureau project areas in Texas and other locations, 1965–2003.

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Depositional systems in the Sparta Formation (Eocene): Gulf coast basin of Texas
(University of Texas at Austin. Bureau of Economic Geology, 1977) Ricoy, Jose Ulises; Brown, L. F. (Leonard Franklin), 1928-
Three principal depositional systems were defined within the Sparta Formation of Texas using surface and subsurface data: high-constructive delta system in east Texas; strandplain-barrier bar system in central Texas; and high-destructive, wave-dominated delta system in south Texas. Principal facies constituents of the high-constructive delta include upper delta plain in outcrop and lower delta plain, delta front, and prodelta in subsurface. Five major deltaic lobes in the Sparta Formation are similar to various lobes of the Eocene Queen City Formation, Lower Wilcox Group, Jackson Group, and Yegua Formation of Texas. The Sparta high constructive delta system is present from Fayette and Colorado counties in Texas, eastward into Louisiana, Mississippi, and Arkansas. The Sparta strandplain-barrier bar system of central Texas is basically composed of a single multistory barrier bar unit. It was constructed with sand transported along strike by longshore currents from reworked sediments of the high-constructive delta system in east Texas. This system extends from Fayette and Colorado counties westward to Atascosa and Live Oak counties. A Halocene analog is the Texas barrier island system. Eocene analogs are the strandplain-barrier bar system of the Eocene Jackson Group, Yegua Formation, Lower Wilcox Group, and Queen City Formation. A high-destructive delta system in south Texas is composed essentially of coastal barriers and associated lagoonal facies in outcrop; and coastal barrier, lagoon, and prodelta shelf facies in the subsurface. This wave-dominated delta system is present from Atascosa and Live Oak counties southward to the Rio Grande, and it extends into northern Mexico. Eocene analogs occur in the south Texas Wilcox Group, Yegua Formation, and Queen City Formation. Oil and gas have not been found in the Sparta Formation, in part because little growth faulting was associated with the thin Sparta delta front sandstone and prodelta shale facies. Water chemistry variations are closely related to depositional systems within the Sparta Formation. A bicarbonate province is related to updip areas (major fluvial influence) of the high-constructive delta system of east Texas; a sulfate province occurs in updip areas (barrier bar/lagoon influence) associated with the high destructive delta system of south Texas and central Texas; and a chloride province is associated with downdip marine sandstone facies of barrier and deltaic origin. Flushing by fresh water has quantitatively but not qualitatively altered the initial water distribution within the various Sparta sand facies.
Evaluation of sanitary landfill sites, Texas coastal zone: geologic and engineering criteria
(University of Texas at Austin. Bureau of Economic Geology, 1972) Brown, L. F. (Leonard Franklin), 1928-; Fisher, W. L. (William Lawrence), 1932-; Malina, Joseph F., 1935-
Basic geologic, hydrologic and engineering criteria on which selection of sanitary landfill sites should be based include (1) thickness, excavation characteristics, permeability, solution-holding capacity, and reactivity of host and cover materials; (2) hydrologic properties including depth to water table, season variation in position of water table, and rate of liquid movement; and (3) nature of terrain in terms of slope, topography, and surface drainage. Evaluation of these features must be based initially on adequate mapping and inventory of surface and near-surface earth materials-both bedrock and surficial soils. Solid wastes include a broad spectrum of residues of municipal and industrial activities. These waste solids include refuse from residential areas, sludges from water and wastewater treatment, plant trash, organic and inorganic chemicals, toxic materials, manures, oils, and other materials which are not discharged into surface waters or into the atmosphere. Basic environmental mapping recently completed in an 18,000-square-mile area of the Texas Coastal Zone, an area embracing nearly one-third of the State's population and industry, shows the distribution of 130 substrate and landform map units. Map units are grouped into four main landfill suitability groups. Of these groups, only one is entirely suitable for landfill sites, two constitute very poor site areas, and one can be utilized only locally and with proper engineering design. Principal landfill suitability groups in the Texas Coastal Zone include (1) clays and muds with low permeability, high water-holding capacity, high compressibility, high to very high shrink-swell potential, low internal drainage, level to depressed surface relief, low shear strength, and high plasticity-such clays and muds provide secure landfill sites; (2) sands with high to very high permeability, low water-holding capacity, low compressibility, low shrink-swell potential, high internal drainage, high shear strength, and low plasticity-these sands are very poor landfill sites; (3) wetlands (marshes and swamps) with very low permeability, high water-holding capacity, high to very high compressibility, high shrink-swell potential, very poor internal drainage, depressed surface relief, and permanently high water table - these wetlands are poor landfill sites; and (4) clayey sands and silts with moderate to low permeability, moderate water-holding capacity, moderate compressibility, low to moderate shrink-swell potential, moderate internal drainage, and high shear strength - these sands and silts are marginal for solid-waste disposal but can be used locally with proper engineering design and control. Of the approximately 100 in-ground solid-waste disposal sites currently in operation in the Texas Coastal Zone, only 20 percent are geologically and hydrologically secure sites. Thirty percent are in substrates that are insecure, potential or active pollution areas. The remaining 50 percent of the sites occur within highly marginal areas with at least some degree of active or potential pollution. Clearly, geologic and hydrologic criteria have not been used in the selection of most existing sites. The Texas Coastal Zone is not unique; in far too few landfill areas are adequate geologic and land-suitability maps available to the planner. Within the Texas Coastal Zone and in most other areas, immediate economic considerations outweigh fundamental geologic and hydrologic suitability in site selection. For example, in the heavily populated and industrialized upper Texas Coastal Zone, the most secure and suitable substrates for solid-waste disposal also support the most valuable agricultural lands; by contrast, geologically and hydrologically insecure sites, such as wetlands and permeable sands, generally constitute less expensive land. Abandoned sand and gravel pits, for example, provide inexpensive, generally available, and ready-made sites, yet due to high substrate permeability, extensive pollution can result when these abandoned pits are used as solid-waste disposal sites. As in most other areas, the bulk of solid waste in the Texas Coastal Zone is disposed of in open dumps; only a small part of the total solid waste is incinerated or disposed of in a sanitary landfill. Under present conditions, properly managed landfills provide the most adequate manner of waste disposal and are naturally far superior to open dumps. However, unless selection of the site is based on geologic and hydrologic criteria, sanitary engineers will be severely handicapped in their efforts to prevent unacceptable environmental pollution.
Geometry and distribution of fluvial and deltaic sandstones (Pennsylvanian and Permian), North-Central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1969) Brown, L. F. (Leonard Franklin), 1928-
Upper Pensylvanian and lower Permian rocks of the Eastern Shelf in North-central Texas are composed of 10 to 15 repetitive sequences including open shelf, deltaic, fluvial, and interdeltaic depositional systems. Sediments derived from the Ouachita Mountains and associated piedmont were transported westward across a narrow coastal plain. Fluvial and deltaic sandstone fac1es define a southwest paleoslopc of about 5 feet per mile. Sandstone facies are delta front sheets, distributary mouth bars, distributary and fluvial channels, and destructional bars. Sandstones displaying distributary patterns represent distal deposition in the upslope area. Belt sandstones, typified by uncommonly thick fluvial channel deposits, prograded far downslope. Composite patterns include distributary and belt sandstones representing complex progradational history. Rocks display one-half degree northwest regional dip; negative structure residuals outline a broad area within which 70 percent of the deltaic facies were deposited. Elongate sandstones are generally arranged parallel to paleoslope in vertically offset patterns controlled by differential compaction of fluvial and deltaic sands and interdistributary muds. Multistory sandstone bodies were deposited along narrow, structurally unstable belts which were periodically overloaded and later reoccupied by prograding deltas. Initial Cisco deltas followed a paleosurface grain controlled by underlying bank limestones; this orientation was maintained during deposition of 1,200 feet of Cisco strata. Each fluvial-deltaic system inherited its geometry from previous systems and, in turn, provided control for the next deltaic episode. Stratigraphic and structural mapping utilizing mud decompaction techniques confirms the roles played by compaction and structure in controlling the geometry of sandstone bodies.
Resource capability units: their utility in land-and water-use management with examples from the Texas coastal zone
(University of Texas at Austin. Bureau of Economic Geology, 1971) Brown, L. F. (Leonard Franklin), 1928-; Fisher, W. L. (William Lawrence), 1932-; Erxleben, A. W.; McGowen, J. H.
A resource capability unit is an environmental entity--land, water, area of active process, or biota--defined in terms of the nature, degree of activity, or use it can sustain without losing an acceptable level of environmental quality. Units are established by recognizing elements of first-order environmental significance, whether dominantly physical, biologic, or chemical. These include (1) physical units (geologic substrate and soil units), where physical properties are of primary importance; (2) process units, such as beaches, washover channels, floodplains, escarpments, and dunes where active physical processes are dominant factors; (3) biologic units,such as reefs, marshes, swamps, and grassflats where biologic activity and habitation assume first-order significance; and (4) man-made units such as spoil heaps, dredged channels, canals, and made land where man's activity has resulted in important environmental modification. Capability of water systems is defined by the nature and distribution of sediment substrate, overall salinity patterns, circulation, tidal influence, depth variations, turbidity, fresh-water influx, distribution of biologic communities, and water chemistry. This report outlines (1) the nature of resource capability units, (2) the basic factors and properties exhibited by the units that define the limits of their use, and (3)the application of resource capability units to environmental management. Specific examples are shown for the 20,000 square miles of the Texas Coastal Zone, where a wide variety of resource units occur in an area of diverse human activities.
Virgil and lower Wolfcamp repetitive environments and the depositional model, North-central Texas
(University of Texas at Austin. Bureau of Economic Geology, 1969) Brown, L. F. (Leonard Franklin), 1928-
Virgil and lower Wolfcamp rocks on the Eastern Shelf in North-central Texas are composed of several intergradational depositional systems comprising 1,200 to 1,500 feet of off-lapping, predominantly terrigenous sediments. At least a dozen major and numerous minor repetitive sequences consist of superposed deposittional systems, composed of more or less homotaxial component facies. Rapidly shifting fluvial-delta sites and associated interdeltaic and open shelf environments on the slowly subsiding shelf were subjected to marine destruction, mud compaction subsidence, and marine transgression. Variations of the basic sequence in time and space resulted from shifting depositional systems. Pluvial variants are downslopes, and deltaic and interdeltaic variants are concentrated in intermediate areas. These facies tracts shifted irregularly southwestward during Virgil and Wolfcamp deposition as the average strandline migrated with westward shelf progradation. Westward pointing deltas locally extended subaerial environments far downslope. Delta sequences between bases of successive delta systems are diachronous and aperiodic as deltation irregularly reoccupied former delta sites. Sequences between bases of successive transgressive limestone facies are also interpreted to be aperiodic and diachronous, but bounding limestones display regional continuity. Delta and fluvial constructional facies represent relatively brief, discrete time intervals, while destructional, interdeltaic, and transgressive facies involved greater time resulting in complex chronology within sequences. The fluvial-deltaic model for Virgil and Lower Wolfcamp rocks make it unnecessary to invoke external cyclic control to explain these North-central Texas deposits. The self-regulating model can operate under continuous sediment supply and continuous but slow shelf subsidence. The model is based on fades relationships and processes rather than absolute scale and geometrical comparison with Recent models. The diachronous nature of fades required by the model and supported by stratigraphic evidence indicates that repetitive deposition was primarily governed by sedimentary processes active within the local basin.

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