The concern of the investigation described in this thesis has been to examine certain drift deposits in southern Wiltshire and to consider their distribution in relation to the accepted interpretation of the landscape. The area examined has been discussed by Wooldridge and Linton (1955) but lies on the periphery of the tract with which they deal, and their treatment is essentially theoretical and not circumstantial. In the course of the investigations which are described, samples were collected from over two hundred sites, surface indications of the geology were examined at a substantially larger number of sites and more than thirty sections were specially excavated in particularly interesting locations. The work is based not on the application of refined geological techniques but on the ability to distinguish, in hand specimens, common and distinctive rocks. In important sections, samples of gravel of from 6 lbs to 2O lbs weight were secured and broken down into three fractions (¹⁄₁₆"-⁵⁄₃₂"; ⁵⁄₃₂"-¹⁄₂"; ¹⁄₂" upwards); for correlative purposes exact counts of the component materials were carried out for the two coarser fractions. Although some of the individual examples encountered are problematic the conclusions have invariably been based on a significant volume of unmistakable material. The use of refined correlative techniques to confirm the results has not been attempted. This omission to some extent reflects the nature of the investigation, which is best regarded as a reconnaissance of a large area, describing evidence not only in Wiltshire but on the Chalk and Eocene outcrops elsewhere in We ss ex, for the most part on ground lying to the West of the Salisbury Avon. The results of the work are described in a comparative study of landscape features using, so far as possible, the whole geographical context of the ground examined: the dissection and weathering of the surface, the drifts and soils which rest upon it, and the relation of the ground to relief both above and below it. In Part One of the thesis an attempt is made to establish the nature of the sub-Eocene unconformity. A study of the Pleistocene river gravels about Salisbury suggests that Eocene formations may have been preserved on the western part of Salisbury Plain at the beginning of the Pleistocene period. This result is inconsistent with the views adopted by Wooldridge and Linton. The composition of the gravels examined suggests that the Eocene formations in question did not resemble formations now recognised in the main Eocene outcrops adjoining Salisbury Plain. A study of the Palaeogene outlier on Salisbury Plain, at Clay Pit Hill, shows the gravels in the outlier to be closely similar in terms of petrology to the distinctive gravels in the Bagshot Beds about Dorchester in Dorset, and a correlation with these beds is suggested. A distinctive gravel from another Palaeogene outlier, at Cley Hill, near Warrninster, is described. This gravel at a height of about 800' O.D. appears to be preserved at or near the level of its original deposition, and is tentatively referred to the Oligocene period. The evidence at Cley Hill and Clay Pit Hill is taken to show that the Chalk suffered extensive erosion during the Eocene and Oligocene periods. A study of sites on the ground intervening between the Palaeogene outliers on Salisbury Plain and the Bagshot outcrop in Dorset provides new evidence on the nature of the Reading Beds, which tends to confirm the results of the investigations on Salisbury Plain. In Part Two of the thesis drifts on the mid- Tertiary surface of Wooldridge and Linton (1955) are described. Drifts on the Upper Greensand outcrop in the Vales of Wardour and Warminster are believed to be of periglacial origin and Pleistocene age. Drift on the Portland outcrop in the Vale of Wardour appears to be the debris of Lower Cretaceous formations and probably rests on an intra-Cretaceous surface. On the Chalk a contrast is discerned between ground occupied by deep very flinty drifts of residual aspect and ground occupied by shallower flint drifts, also of residual aspect. The shallow drifts are shown to be associated with the relics of gravels incorporating Upper Greensand, Lower Cretaceous and Jurassic debris. The deep very flinty drifts are believed to confirm the views of Wooldridge and Linton concerning the mid-Tertiary surface, but the shallower drifts and associated gravels are thought to rest on a separate surface, and the Cretaceous and Jurassic debris is believed to imply the competence of transverse gradients during the dissection of the mid-Tertiary surface. The evidence described in Part Two of the thesis is difficult to reconcile with the concept of marine transgression across the Wiltshire Chalk. In Part Three of the thesis drifts on the supposed marine plain are described and the marine origin of the surface is rejected. Specific evidence of a 'Pliocene' transgression in Wessex is reviewed and a study of supposed 'Pliocene' material refers the material in question to the Eocene period. Problematic aspects of Pliocene stratigraphy and the concept of superimposition from a Pliocene surface are reviewed. Pinchemel's objections (1954) to a depositional surface are accepted but his views on fluvial aggradation are rejected in a study of gravel at Alderbury, near Salisbury, referred by him to this aggradation. Difficulties inherent in the concept of marine planation are recognised and ground referred by Wooldridge and Linton to the Pliocene marine plain is shown to be essentially indistinguishable from their mid-Tertiary surface and is therefore believed to be correlative with it. This view implies post-mid-Tertiary deformation of the Chalk. In Part Four of the thesis a theory of drainage evolution is developed to replace the hypothesis based on a concept of late Tertiary marine planation. Drifts, landforms and drainage morphology in the Vale of Wardour are shown to demonstrate a deformed, subaerial planation surface, bevelling the outcrop of the Chalk and earlier formations at a level below the mid-Tertiary surface of Wooldridge and Linton. The present drainage pattern is believed to have originated during the deformation of this surface, probably in the Plio-Pleistocene interval. This subaerial surface is also identified on Salisbury Plain and the origin of the drainage pattern there and in the Alderbury syncline is described. The available evidence suggests that the subaerial surface was elaborated during the Pliocene period following the deformation of the Oligo-Miocene (mid-Tertiary) surface. The character of the late Tertiary (Pliocene) surface suggests comparisons with the surfaces described by King (1962) and termed by him pediplains, although the nature of the process involved remains doubtful. In Part Five of the thesis some aspects of Pleistocene erosion are treated. Adjustments to the drainage pattern in the basin of the Avon above Salisbury during the Pleistocene period are discussed. This account is based on analyses of gravels of the Avon and its tributaries about Salisbury. The concept of successive stages of marine planation in the Hampshire Basin daring the Pleistocene period is rejected in a study of the composition and morphology of the Pleistocene gravels. An alternative scheme of subaerial planation is suggested and some morphological evidence of this planation on the Wiltshire Chalk and on the Eocene outcrop in the Hampshire Basin is described. The problems of scarp recession and the dessication of the dry valleys are reviewed and the concept of scarp recession is abandoned.

Frequency amplitude spectra derived from P-wave seismic data can be used to derive a fracture indicator. This fracture indicator can be used to delineate fracture zones in subsurface layers. Mapping fractures, that have no vertical offset, is difficult on seismic sections. Fracturing changes the rock properties and therefore the attributes of the seismic data reflecting off the fractured interface, and data passing through the fractured layers. Fractures have a scattering effect on seismic energy reflected from the fractured layer. Fractures attenuate amplitudes of higher frequencies in seismic data preferentially than lower frequencies. The amplitude spectrum of the frequencies in the seismic data shifts towards lower frequencies, when a spectrum from a time window above the fractured layer and below the fractured layer is compared with each other. This shift in amplitudes of frequency spectra can be derived from seismic data and used to indicate fracturing. A method is developed to calculate a parameter t* to measure this change in the frequency spectra for small time windows (100ms) above and below the fractured layer. The Austin Chalk in South Central Texas is a fractured layer and produces hydrocarbons from fracture zones with the layer (Sweet Spots). 2D and 3D P-wave seismic data are used from Burleson and Austin Counties in Texas to derive the t* parameter. Case studies are presented for 2D data from Burleson county and 3D data from Austin County. The t* parameter mapped on the 3D data shows a predominant fracture trend parallel to strike. The fracture zones have a good correlation with the faults interpreted on the Top of Austin Chalk reflector. Production data in Burleson County (Giddings Field) is a proxy for fracturing. Values of t* mapped on the 2D data have a good correlation with the cumulative production map presented in this study.

No description available.

Acid fracture conductivity and the effect of key variables in the etching process during acid fracturing can be assessed at the laboratory scale. This is accomplished by using an experimental apparatus that simulates acid injection fluxes comparable to those in actual acid fracture treatments. After acid etching, fracture conductivity is measured at different closure stresses. This research work presents a systematic study to investigate the effect of temperature, rock-acid contact time and initial condition of the fracture surfaces on acid fracture conductivity in the Austin Chalk formation. While temperature and rock-acid contact are variables normally studied in fracture conductivity tests, the effect of the initial condition of the fracture surface has not been extensively investigated. The experimental results showed that there is no significant difference in acid fracture conductivity at high closure stress using smooth or rough fracture surfaces. In addition, we analyzed the mechanisms of acid etching and resulting conductivity creation in the two types of fracture surfaces studied by using surface profiles. For smooth surfaces, the mechanism of conductivity creation seems connected to uneven etching of the rock and roughness generation. For rough surfaces, acid conductivity is related to smoothing and deepening of the initial features on the sample surface than by creating more roughness. Finally, we compared the experimental results with Nirode-Kruk correlation for acid fracture conductivity.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 182-218). Also available via the Internet.

Berlin, Freie University, Diss., 2004. / Dateiformat: zip, Dateien im PDF-Format.

(Unrelated), a series of language-based works made up of chalkboard drawings, dictionary erasures and accumulations of text, highlights the inability of language to fully capture notions of modern racial identity. Rather, in (Unrelated), definitions are hidden, revealed, allowed and humored, but rarely settled. It is natural to seek delineation between oneself and all else, but it is a particularly persistent urge for those who engage in the pursuit of racial clarity. In To Be Real, an essay which heavily influenced this body of work, Danzy Senna writes: “Growing up mixed in the racial battlefield of Boston, I yearned for something just out of my reach- an ‘authentic’ identity to make me real. Everyone but me, it seemed at the time, fit into a neat cultural box, had a label to call their own.”[1] (Unrelated) quietly explodes the “neat cultural box.” [1] Senna, Danzy. "To Be Real," To Be Real: Telling The Truth and Changing the Face of Feminism, ed. Rebecca Walker (New York: Anchor, 1995) 6.

The Canadian National Memorial Site, near Vimy, Artois, France, commemorates the WWI Battle of Vimy Ridge; where all four divisions of the young Canadian Corps fought together with the British Forces to liberate the French ridge. Today, trench systems and an extensive subterranean network of tunnels underlie the gentle landscape of the park, which is visited each year by hundreds of thousands of tourists. Failure within these excavations is expressed as local subsidence and is potentially hazardous to the public. The following research identifies the geologic factors that influence instability in the excavations and how these factors vary both with depth and lateral extent. The Artois region of northern France is underlain by Upper Cretaceous chalk with a thin veneer of Paleocene sediments. Structure is dominated by the northwest-southeast trending Weald-Boulonnais anticlinorium. Three principle geological controls govern failure within the excavations at the Vimy site; lithologic variations, structural geometry and carbonate dissolution. An extensive stratigraphic study identified variable horizons such as chalk marls, nodular chalks, hardgrounds and flint seams, which affect the strength, permeability and structure of the rockmass. Structural geometry in the chalk varies with depth and clay content. Orthogonal fracture patterns are typical in pure carbonate rockmasses whereas inclined conjugate sets occur in clay-rich chalk. Three failure mechanisms were observed in the Vimy excavations that vary with structure and lithology. Beam failure via block fall-out is observed in pure chalk with subhorizontal and subvertical structures. Ravelling, the upward propagation of roof failure, is typical of closely spaced inclined jointing, and is also observed in shallow clay-rich lithologies. Finally, dissolution pipes occur at the intersection lineations of conjugate joint sets, and are also typical of clay-rich lithologies. Dissolution by meteoric groundwater is identified as the third geologic control and results in a decrease of intact strength, weakening of joint surfaces and overall loss of confinement in the rockmass, thereby initiating the failure modes described previously. These extensive geologic studies pinpoint the origins and variability of instability in the rockmass at the Vimy site. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2007-12-21 11:08:16.522

Petroleum reservoirs located in the Norwegian sector of the North Sea have undergone unexpected subsidence of great magnitude (> 10 m) during more than 30 years of petroleum recovery operations. Historical laboratory investigations have shown that the subsidence is due to the mechanical behavior and mechanical properties of chalk. Chalk behavior is characterized by elastoplasticity, including pore collapse, shear failure, and tensile failure mechanisms; rate-dependence; and pore fluid dependence. The research described in this dissertation was performed with the objectives to formulate a constitutive model which describes all aspects of chalk and soft rock mechanical behavior, develop and/or implement methods to integrate the equations which form the constitutive model, and to apply the model to finite element simulations of engineering problems encountered in chalk and soft rock. A new rate-dependent constitutive model is developed based on a three-dimensional extension of a volumetric time-lines model, similar to that of Bjerrum (1967). Shear and tensile failure surfaces are also included to reflect these failure mechanisms observed in chalk. Twelve model parameters are required to fully describe chalk behavior. Procedures to determine values for each of these parameters from laboratory test results are described. Correlations of model parameter values with index parameters are given for North Sea chalks, to allow reasonable values to be obtained in the absence of an extensive laboratory testing program. Comparisons between observed behavior and model simulations indicate that the new model is able to reproduce and predict the behavior of chalk quite well. A new integration method for critical state cap plasticity models is presented. This new method may be used for rate-independent or rate-dependent constitutive models which are formulated with elliptical cap yield surfaces, including the chalk model. The new method gives results that compare favorably to integration methods used currently, in terms of accuracy and computational effort. The effects of pore fluid composition on chalk behavior are included in the constitutive model. It is shown that the variability in constitutive behavior with pore fluid composition is due to dependence of model parameter values on pore fluid composition. This variability in model parameters with pore fluid composition has been quantified and implemented into the model for the complete spectrum of oil-water mixtures in chalk. Finite element simulations are presented to demonstrate performance of the model in analyzing problems at several different scales, including laboratory, borehole, and full-field scales. A new algorithm called "equivalent uniform water saturation" has been developed to determine the average mechanical properties of finite chalk masses with non-uniform pore fluid compositions, which are frequently encountered during finite element simulations. Results of the laboratory-scale simulations indicate that the constitutive model can reproduce the inhomogeneous deformation patterns which occur in chalk during waterflooding tests, and that use of the new algorithm utilizing "equivalent uniform water saturation" produces consistent results for chalk masses with inhomogeneous pore fluid distributions when used with different finite element mesh discretizations. Results of the larger-scale simulations indicate that changes in pore fluid composition and pore fluid pressure have different effects on macro-scale chalk mechanical behavior, and that both must be considered during analysis. / Ph. D.

Marine organic-walled microplankton biostratigraphy of the Maastrichian Prairie Bluff Chalk is documented. A total of 69 dinoflagellate species were identified in the Prairie Bluff Chalk. Samples were studied from three sites in central and western Alabama (Tombigbee River, Millers Ferry, and Braggs). Also included were several samples of the overlying Clayton Formation, and the underlying Ripley Formation. The species and their stratigraphic ranges were compared with other coeval sections in the U. S. and Europe. Dinoflagellate Zones Va and Vb of Wilson (1974) are recognized in the Prairie Bluff Chalk. This suggests the age of the Prairie Bluff Chalk is restricted to late Maastrichtian. The Prairie Bluff Chalk correlates to the upper Providence Formation of Georgia (Firth 1984); the lower Providence being early Maastrichtian. The basal Clayton Formation may be latest Maastrichtian in age / Master of Science