I solve boundary-value problems for an idealized thrust block moving over a detachment surface and ramp, and produce theoretical bed-duplication folds in the thrust block that closely resemble the Powell Valley anticline in the southern Appalachian Mountains. The anticline is narrow and rounded if the translation is small, and broad and flat-topped if the translation is large. The limbs of the anticline are symmetric if drag is zero. Drag along the ramp part of the detachment surface can explain the asymmetry of dips of the two limbs of the Powell Valley anticline, particularly if drag between relatively competent rocks in opposition at the ramp causes an initial anticline to form as the thrust block begins to move, and then drag reduces markedly as relatively soft shales at the base of the block were thrust over competent rocks in the ramp.
Roots of white ash have a better configuration than roots of sugar maple for anchoring shallow colluvium against landsliding on hillslopes along the Ohio River and its tributaries in southwestern Ohio. The landslides are in a shallow layer of colluvium, about one meter thick, overlying shale and limestone bedrock. The sliding hillsides range in slope angle from 16 to 36 degrees and the roots which penetrate shear surfaces are anchored in the weathered bedrock and help to hold landmasses in place. The hillsides are covered by a mesophytic forest, locally known as a ravine community, dominated by white ash, sugar maple and sweet buckeye. Sugar maple is the most common species on the landslides; its roots do not penetrate the soil as deeply as the roots of the white ash.
The Aspen Grove landslide, central Utah, occurred in older landslide debris. The debris is about 6-15 meters thick, and consists of medium- to high-plasticity clays and silty clays. Persistent landslide structures, including toes, hollows, and flank ridges, outline dimly preserved landslide masses in the older debris.
Stylolites in twelve stratigraphic sections of the Salem Limestone, distributed throughout the Illinois Basin, provide clues to their origin and development. Chemical and X-ray diffraction analyses reveal that stylolite seam material contains organic matter and clay minerals too sparse or absent in the host limestone to be considered solely as insoluble residue. Stylolite distribution in various lithofacies suggests that stylolites develop along thin sedimentary layers rich in organic matter and clay minerals. Stylolite density (vertical distribution) mimics the distribution of organic-rich sedimentary layers: sparse but thick in grainstone, and abundant but thin in packstone and wackestone. Many stylolites grade laterally into organic-rich layers, or hummocky seams. Thicknesses of stylolite caps and hummocky seams are approximately equal in the same host rock, but hummocky seams tend to be more laterally continuous. Stylolite density in packstone increases with burial depth, whereas hummocky seam density decreases. Hummocky seam thickness does not change with depth. Stylolite column height in grainstone, which is sparse in hummocky seams, increases with depth, whereas stylolite density does not increase. This list of observations supports the hypothesis that stylolites develop along pre-existing, organic-rich layers, or hummocky seams, rather than nucleating in pure host rock and creating organic-rich seams as accumulations of insoluble residue. Volumetric calculations indicate that the contribution of stylolites to pore-filling cement is 5 to 25 percent throughout the Illinois Basin.
Cambrian sedimentation of the Rome trough in eastern Kentucky was studied using 85 wells supplemented by available cuttings and cores. Most conclusions are based on cross sections, isopach and structure maps, and the environmental interpretation of geophysical logs. Thin section petrology played a supplementary role.
Organic carbon (C) and sulfide sulfur (S) contents of host rocks and ore bodies selected from four manganese carbonate deposits were tested and plots of carbon against sulfur of the type proposed by Berner were used to distinguish depositional environments.
Detailed mineralogic and chemical analyses of well cuttings of Tertiary sediments from two wells, Uruan-1 and Uda-1, on the eastern flank of the Niger delta, have been made in an attempt to investigate clay mineral burial diagenesis.
Stratigraphic, sedimentologic and petrographic studies of the Lower and Upper Cretaceous in northwest Sonora show that deposition of the Bisbee Group occurred at the northern margin of a back-arc marine basin, and of the El Chanate Group and El Charro volcanic complex in a closed continental foreland basin. This study also finds that the Proterozoic-Paleozoic formations in northwest Sonora (Caborca terrane) were not part of the Cretaceous landscape, thus raising doubts about the existence of the Mojave-Sonora megashear.
The depositional style, biostratigraphy and burial history of the Late Early Pliocene, Moruga Group were studied in outcrop and the subsurface, along the south coast of Trinidad to determine its depositional environments, sediment sources, geologic age, and diagenetic history.
Slaty cleavage exposed in the fine-grained metasediments of western Ocoee Gorge, Tennessee is characterized by zones enriched in cleavage-parrallel white mica (P domains), alternating with zones enriched in quartz and feldspar and in which phyllosilicates are bedding-parallel (Q domains). This domainal fabric appears to develop by growth of new mica from mica components carried in a moving fluid. Solid state recrystallization of clays and mica may also have contributed to the development of the fabric, but little, if any, mechanical rotation or passive concentration of mica grains occurred. Both P domain morphology and mineralogical differences between P and Q domain phyllosilicate populations suggest that nucleation and growth of P domains may involve the expulsion of fluids, during diagenesis and low-grade metamorphism.
In this dissertation I present a tectonic, geochemical, and thermal history for the Witwatersrand basin, located on the Archean Kaapvaal craton, South Africa. The foreland basin tectonic setting of the Central Rand Group controls both the chemical and the thermal evolution of the basin, and unifies the basin evolution model presented here.
This dissertation is a contribution toward low pressure geochemistry and petrology of alkaline rocks. In order to analyze the phase equilibria in multiply saturated potassic alkaline systems, experiments were performed at one atmosphere pressure and under the $\rm f\sb{O2}\sim QFM$ buffer. Range of temperature covered in this study is 1060-1250$\sp\circ$C. In addition, temperature and composition dependency of low pressure mineral-melt equilibria involving olivine, pyroxenes, plagioclase, nepheline, and leucite were modeled using empirical equations.
Various geochemical parameters including type and abundance of organic matter (TOC), sulfide-sulfur quantities, fluctuations in bottom-water anoxicity (DOP), metal content differences, and sulfur isotope variations have been assessed in order to characterize Midcontinent Pennsylvanian black shales. Based on these geochemical parameters, the deposits can be grouped into three types: Mecca-type, Heebner-type, and Shanghai-type.
"The Molango manganese deposit is the only known large Mn deposit in North America. Mineralization involves Mn-carbonate exclusively in a finely laminated bed about 10 meters thick with a strike length $>$50 kilometers. The ore bed is the basal unit of the Chipoco facies (Taman Fm., Kimmeridgian) and underlain by laminated black shales of the Santiago formation (Oxfordian)."
The Coalinga, California region contains massive amounts of diapirically emplaced deposits of serpentinite. The largest deposit, the New Idria Formation, forms the core of the Joaquin Ridge Anticline and outcrops over an elliptically-shaped 48-square mile area in a mountainous area 17 miles northwest of Coalinga and 15 miles west of the California Aqueduct constructed along the western margin of the San Joaquin Valley. The serpentinite deposit is in faulted diapiric contact with Cretaceous-aged sandstones and shales and became emergent approximately 17 to 20 million years ago in the Miocene era. Eroded asbestos-bearing sediment from this ultramafic deposit has been incorporated in late-Miocene and younger sedimentary formations in the central San Joaquin Valley region.
Mapping of the Wayaro quadrangle (680 sq kms; scale 1:50,000) revealed that the Bela Ophiolites were thrust upon a sedimentary melange (Kanar Melange) which was deposited in the Paleocene on the Sembar Formation of Cretaceous age.
The Dalton quadrangle (Ga. - Tenn.), located in northwest Georgia within the Ridge and Valley province, is a fifteen-minute quadrangle with topographic base by the U.S. Geological Survey. Because of the excellence of the base map and the location of the quadrangle in an area of lower Paleozoic rocks, it was selected as a beginning point for a re-investigation of the geology of northwest Georgia.
The Allegheny Mountains of east-central West Virginia were imperfectly peneplained in pre-Schooley time. There is no evidence that any external base level has affected this region since uplift of the pre-Schooley surface, i.e., no peneplains controlled by a base level outside the area have developed since pre-Schooley time. The region has been lowered by differential mass-wasting ever since this uplift.
The principal objective of this study was to develop a battery of methodologies for the analysis of texture, grain packing and pore geometry in sands and sandstones. The methodologies developed include: (1) the 'roller micrometer', a machine which sizes grains by their smallest dimension, S; (2) plots of the joint I:S size and S/I form distributions (I is the intermediate grain dimension determined by sieving); (3) a sorting comparator for the visual estimation of sorting in thin sections; (4) 'packing efficiency', the ratio of minimum compactional to depositional porosity; (5) 'floating index', the proportion of grains lacking intergranular contacts; (6) correction of measurement errors in standard thin section packing analyses; (7) transformation, via digitization, of plain sections of samples into matrices of binary (rock vs pore) numbers; and (8) computer processing of the rock-pore matrices using the Fortran IV program PORESTAT which measures numerous parameters including porosity, specific pore surface area, pore size distribution, pore tortuosity, pore orientation, and periodic repetitions in the pore pattern.
Little is known about the hydraulic fracturing of soil, although the technique holds potential for several environmental engineering applications. The dissertation research consists of laboratory experiments, where hydraulic fractures were created by injecting dyed glycerin into colluvium contained in a triaxial pressure cell, and a field test, where hydraulic fractures were created by injecting guar gum gel at shallow depths in glacial drift. The laboratory tests showed that hydraulic fractures are readily created in clayey-silt colluvium. Furthermore, hydraulic fractures created in soil with positive pore pressure were filled with two fluids: one injected to create the fracture, and pore fluid that infiltrates into the fracture tip. The length of the infiltrated tip increases with increasing fracture length.
The hydrology of a thin colluvium hillside at the Delhi Pike landslide complex, approximately 15 km west of downtown Cincinnati, is controlled by infiltration and evapotranspiration. Pore water pressures approach $-$10 m H$\sb2$O during summer and autumn, but rise to $-$1 m H$\sb2$O or higher after several days of steady winter rains. This state of near saturation is maintained until large trees leaf out and pore pressures fall dramatically in late spring.
The nature of taphonomic overprint affecting the fossil records of the regular echinoid Families Cidaridae, Diadematidae, Toxopneustidae and Echinometridae is investigated using a synthesis of actualistic and literature-derived data. The actualistic portion of this study focuses on the following extant members of the four families: Eucidaris tribuloides, Diadema antillarum, Tripneustes ventricosus and Echinometra lucunter. Population censuses of these animals in tropical reef and near-reef environments demonstrate that the distribution of macro- and microscopic skeletal material does not reflect the distribution of the living fauna. Field experiments with freshly-killed carcasses of Eucidaris, Diadema and Echinometra indicate that loss of all organic tissue occurs within six days after death, reducing these echinoids to essentially bleached carcasses.