Bryan Tapp

Relationships of rock cleavage fabrics to incremental and accumulated strain in the conococheague formation, U.S.A.

Abstract Pressure solution coupled with twin gliding, and recrystallization acted to form two geometrically distinct cleavages in the Conococheague Formation, northwest Virginia and West Virginia. Limestone layers contain a penetrative cleavage ( S p ) formed by pervasive pressure solution (Coble creep), with twin gliding in more highly deformed zones. Dolomite layers contain a spaced solution cleavage ( S s ) formed by pressure solution, also with twin gliding in highly deformed zones. Recrystallization textures occur in highly deformed zones of limestones and dolomites. Incremental strain shows that layering was initially inclined as much as 30° to shortening, and that the deformation was locally non-coaxial, as viewed by the deforming material on the fold limbs. Spaced cleavage zones are curved, and closely match the initial and final orientations of incremental elongation. Penetrative cleavage parallels the elongation axis of accumulated strain (measured using deformed ooids). Pressure solution surfaces in dolomites concentrate insoluble materials. Deformation, together with twin gliding, and recrystallization are greatest in the hinge zones of folds and least on shallowly dipping limbs of asymmetric folds. The deformation mechanism path of calcite and dolomite are similar; changing from pressure solution to twin gliding with recrystallization as strain rate (strain energy density) increases.

Pressure solution zone propagation in naturally deformed carbonate rocks

Three independent lines of evidence in samples from the Conococheague Formation, northwestern Virginia, show that solution cleavage zones are best explained by the propagation (anticrack) model of solution zone formation. (1) Anticrack model predictions of the plastic deformation associated with propagating solution zones compare favorably to plastic deformation in rocks measured along the trace of solution cleavage zones by using an X-ray pole figure texture goniometer; (2) volume strain, measured with an electron microprobe along cleavage zones, diminishes from the center of solution cleavage zones to the tip; and (3) curvature of solution cleavage zones in three samples from different locations on folds follows incremental strain elongation. These three lines of evidence, taken together, are consistent with the anticrack origin of pressure solution for the surfaces studied.

Raman and FTIR studies of complex formation in aluminum trichloride-alkali thiocyanate ambient-temperature molten salt solutions

Abstract Raman and FTIR spectra of xAlCL 3 -(1 − x ) MSCN ( M = Li , Na , or K ) ambient-temperature molten salt solutions were recorded over the composition range, 0.35 x 3 -MSCN pseudo binaries are similar to those of the AlCl 3 -MCl binaries. The internal modes associated with the SCN and AlCl 3 groups indicate that large complex anions such as AlCl 3 SCN − and Al 2 C1 6 SCN − are formed in these melts. Also, complexes in which more than one SCN ligand may substitute for Cl are possible. Therefore, [ Al n ( SCN ) m Cl 3 n − m + 1 ] − can be considered as a general formula for complex anions, in which m and n may assume certain integer values that depend on the melt composition. These large complex anions result in a large reduction in the melting point or liquidus temperature. The relative ease of glass formation in the AlCl 3 -MSCN pseudo binaries may also be related to the presence of such large complex anion species in the liquid state, with the SCN − anions either terminal or bridging bonded. These complex anions allow for systems with large cation conductivities due to a high degree of decoupling of the M + alkali cations from the anion matrix.

Rational Rock Physics for Improved Velocity Prediction and Reservoir Properties Estimation for Granite Wash (Tight Sands) in Anadarko Basin, Texas

Due to the complex nature, deriving elastic properties from seismic data for the prolific Granite Wash reservoir (Pennsylvanian age) in the western Anadarko Basin Wheeler County (Texas) is quite a challenge. In this paper, we used rock physics tool to describe the diagenesis and accurate estimation of seismic velocities of P and S waves in Granite Wash reservoir. Hertz-Mindlin and Cementation (Dvorkin’s) theories are applied to analyze the nature of the reservoir rocks (uncemented and cemented). In the implementation of rock physics diagnostics, three classical rock physics (empirical relations, Kuster-Toksoz, and Berryman) models are comparatively analyzed for velocity prediction taking into account the pore shape geometry. An empirical (-) relationship is also generated calibrated with core data for shear wave velocity prediction. Finally, we discussed the advantages of each rock physics model in detail. In addition, cross-plots of unconventional attributes help us in the clear separation of anomalous zone and lithologic properties of sand and shale facies over conventional attributes.

Imaging of Fault and Fracture Controls in the Arbuckle-Simpson Aquifer, Southern Oklahoma, USA, through Electrical Resistivity Sounding and Tomography Methods

Arbuckle-Simpson aquifer in southern Oklahoma, USA, is a major source of water for industrial and municipal use. It is also a major source for spring-fed streams in the area. As part of an ongoing study to map and characterize the Arbuckle-Simpson aquifer, an electrical resistivity tomography (ERT) study and electrical resistivity sounding studies were conducted in Johnston County, Oklahoma, USA, to map the subsurface of a small area of the carbonate aquifer. The main aim of the study was to obtain constraints on the location of near surface faults and fractures and how they control groundwater flow in the study area. The interpreted resistivity section along an N-S profile indicates that the water table in the region is deepening to the south and probably bounded in the north by a south dipping fault. Inverse modeling of 2D electrical resistivity tomography (ERT) data acquired at two adjacent locations within the study area indicate shallow, fractured Arbuckle group rocks saturated with water adjacent to dry rocks. From electrical resistivity mapping results, it is inferred that the Mill Creek block in the Arbuckle-Simpson aquifer is an isolated system, interacting with the northern segment of a silicate-based aquifer through dissolution faults and fractures.

Characterizing the Arbuckle-Simpson aquifer through electrical methods

Summary The Arbuckle-Simpson aquifer lies beneath a surface area of about 500 square miles in south-central Oklahoma, USA and is a major source of water for local use. It is also the source for spring fed streams in the area. Although current withdrawal rates from the aquifer are low, rapid growth of the metropolitan area around the aquifer has focused attention on the aquifer as a source of water for a larger geographical area in the future. As part of an ongoing study to map and charac terize the Arbuckle-Simpson aquifer, an electrical resistivity sounding study was conducted in Johnston County, Oklahoma, USA, to map the subsurface of a small area of the carbonate aquifer. The main aim is to obtain constraints on the location of faults, and to understand how they influence groundwater hydrology in the region. Data from electrical resistivity soundings were interpreted using a combination of resistivity curve fitting and inversion analysis to estimate resistivity of the shallow subsurface and depth to the groundwater table. The interpreted resistivity section along the N-S line indicates that the water table in the region is deepening to the south and probably bounded by a south dipping fault. This interpretation is independently corroborated by groundwater well data from the study area and supports the interpretation that a southward-dipping fault may confine the aquifer at depth. Inverse modeling of Electrical Re sistivity Tomography (ERT) data acquired at two other locations within the study area indicate shallow, fractured Arbuckle group rocks saturated with water adjacent to dry rocks. Additional work is being conducted for detailed imaging of the faults and fracture systems in the area and to characterize the aquifer.