AAPG Bulletin

Published by American Association of Petroleum Geologists
Print ISSN: 0149-1423
Pyrolysis experiments were performed on Green River and Monterey Formation kerogens (Types I and II, respectively) with and without calcite, illite, or montmorillonite at 300 degrees C for 2 to 1,000 hours under dry and hydrous conditions. Pyrolysis products were identified and quantified, and a material balance of product and reactants resulted. Significant differences were found in the products generated by pyrolysis of kerogens with and without minerals. Both illite and montmorillonite adsorb a considerable portion (up to 80%) of the generated bitumen. The adsorbed bitumen is almost exclusively composed of polar compounds and asphaltenes that crack to yield low molecular weight compounds and insoluble pyrobitumen during prolonged heating. Montmorillonite shows the most pronounced adsorptive and catalytic effects. With calcite however, the pyrolysis products are similar to those from kerogen heated alone, and bitumen adsorption is negligible. Applying these results to maturation of organic matter in natural environments, we suggest that a given type of organic matter associated with different minerals in source rocks will yield different products. Furthermore, the different adsorption capacities of minerals exert a significant influence on the migration of polar and high molecular weight compounds generated from the breakdown of kerogen. Therefore, the overall accumulated products from carbonate source rocks are mainly heavy oils with some gas, whereas light oils and gases are the main products from source rocks that contain expandable clays with catalytic and adsorptive properties.
The tectonic evolution of the southeastern corner of the Caribbean is examined, using field data from the El Pilar fault zone of Trinidad and offshore seismic data. It is found that the dominant process in the region's tectonic evolution is strike-slip motion on at least five major fault systems in a 250-km wide east-west-trending plate-boundary zone extending from Grenada in the north to the Orinoco River in the south. The geological effects of this evolution over the past 30 m y are described.
Exploration for Carlin-type gold orebodies in the western United States typically involves sampling and analysis of jasperoid, a distinctive alteration type formed by intense silicification of marine sediments. In this study, rock suites were collected from six orebodies and four similar but barren systems. Jasperoids at all ten systems contain episodically silicified breccias, quartz vein stockworks, elevated As, Sb, Hg, Ba and Tl, and, locally, anomalous Au and Ag. Jasperoids from the four barren systems are as anomalous as jasperoids from the six orebodies in all members of an epithermal geochemical suite, including gold and silver.A database suite containing 272 samples from six of the ten systems was analyzed for 45 elements. Q-mode factor analysis shows that geochemical variance in the epithermal geochemical suite is related to geochemical variance in Li, P, Mn, Ba, Mo, Cr, Co, V, Cd, Ni, U, Zn and Pb. Metalliferous marine black shales are enriched in these elements and are spatially related to Carlin-type deposits.A test suite containing 109 samples from the four remaining systems was analyzed to determine whether a discriminant function derived from the database suite could be applied to exploration. An 8-element function correctly assigned 40 of 42 jasperoid samples collected from the surface at the Carlin and Horse Canyon gold deposits. These results indicate that elements characteristic of metalliferous marine black shales can be used to identify Carlin-type systems with associated gold ore. Gold in Carlin-type orebodies may have been leached from a source-rock sequence which contains metalliferous marine black shales.
Growth faults are considered to be major migration conduits in the Niger Delta. However, the hydrocarbon distribution often shows such seemingly erratic patterns that doubt remains about the actual migration processes. After considering the sequential aspects of hydrocarbon generation and possible contemporaneous structural deformation, some of the apparent inconsistencies in the along-fault migration theory can be explained. When we study the relationship of fault-sealing capacity with the sand and shale thickness distribution, systematic patterns of hydrocarbon distribution are clearly revealed in many fields. The occurrence of several thick, somewhat undercompacted clay layers that locally form effective seals to vertical migration is also important.Structures with a predominance of thick sands and thin shales can trap large volumes of hydrocarbons, but only if they are unfaulted. More complex growth-fault structures, cut by secondary faults, will only be prominent oil fields if the shales are sufficiently thick to cause widespread fault sealing and shale-to-shale juxtaposition along faults. In many cases the lateral distribution of hydrocarbons over a series of fault blocks can be predicted fairly accurately on the basis of these considerations.An interesting phenomenon related to the proposed migration system is the occurrence of water trapped downdip from a hydrocarbon accumulation. Differences as large as 1,000 ft can exist between the oil-water contacts on opposite flanks of a reservoir.
The purpose of the reported study is to analyze Seasat SAR imagery of a heavily vegetated mountainous land surface and to determine the potential of this microwave imaging system for geologic mapping. It is found that geologic mapping using orbital Seasat SAR imagery is feasible in the Appalachian Valley and Ridge province, where the radar system is highly sensitive to change of surface slope. Image tones and textures correlate with distinctive topography, from which generalized lithologic and structural interpretations are derived. Major and minor linear topographic features are easily mapped from the SAR images. The SAR sensor suppresses subdued geomorphic lineaments that strike parallel with or near to the radar look direction. This deficiency is partly compensated by the dual directions of radar illumination obtainable from the Seasat imaging system.
Thesis (M.A.)--University of South Florida. Bibliography: leaves 47-48.
Thesis (M.A.)--University of Northern Colorado, Dept. of Earth Sciences, spring quarter, 1986. Major advisor, Kenneth D. Hopkins. Includes bibliographical references (leaves [82]-87).
Typescript (photocopy). Four plates in pocket. Thesis (M.S.)--Colorado State University, 1990. Includes bibliographical references.
Holocene shallow-water carbonate and evaporite sediments are forming in the Khor al Bazam, a saline lagoon on the coast of Abu Dhabi, southwest Persian Gulf. The sediments are composed of (1) skeletal grains, including whole and fragmented mollusks, corals, calcareous algae, bryozoans, foraminifers, and ostracods; (2) nonskeletal grains, including oolites, pellets, and pellet aggregates; (3) carbonate mud; (4) noncarbonate minerals including gypsum, anhydrite, and terrigenous quartz; and (5) organic material incorporated within mud and carbonate grains. Lithofacies are (1) coral and coralline-algae facies, (2) oolitic sand facies, (3) pellet-aggregate and pellet facies, (4) mud and pellet facies, (5) molluscan sand facies, (6) algal mat facies, and (7) evaporite facies. Nonskeletal calcium carbonate sediment types are related to wave energy; oolites form in the most turbulent environments, pellet aggregates in moderately sheltered environments, and pellets and muds in areas of low wave energy. Skeletal material is altered by blue-green algae. The grains contain algal cells and threads invested in mucilage. Respiration and photosynthesis by algae dissolve the original shell material and reprecipitate microcrystalline aragonite. Chemical changes within the investing organic material cause blackening of some of the carbonate grains.
The presence of growth faults on shelf-margin deltas complicates the sequence-stratigraphic interpretation of deltaic successions. This article describes an analog modeling study of a growth-faulted shelf-margin delta. The aim of the project was to obtain a better understanding of the depositional architecture on a systems tract scale on both sides of the growth fault and to evaluate possible hydrocarbon-trapping configurations in such successions. The analog flume experiment incorporated the combined effect of growth faulting, regional subsidence, and eustasy on hanging-wall and foot-wall blocks. Experimental variables were based on seismic and well data of the Imo River field in the Niger Delta, which was used as a prototype to calibrate the experimental results. The spatial scale of the model, in conjunction with the supply rate, result in a time scaling that models basin-fill processes that operated over more than 5 m.y. in 90 hr of experiment. Digital topography scans, required for the determination of the bulk sediment transport, were made of the landscape at preset time intervals. The resultant experimental sedimentary successions on both sides of the growth-faulted shelf margin were sliced and correlated across the fault. The results first were compared to the Imo River field prototype and subsequently to examples from the Gulf Coast and to extensional basin settings. These comparisons led to the formulation of a conceptual sequence model for growth-faulted margins that relates the systems tract distribution on each side of the fault to eustasy. The hanging-wall succession is composed of falling stage lowstand, and early transgressive deposits. The footwall succession, in contrast, is characterized by late transgressive, incised valley-fill, and highstand deposits. The conceptual sequence model provides useful analogs for common and several alternative hydrocarbon-trapping configurations in growth-faulted settings.
Thesis (Ph.D.)--Northwestern University, 1957. Includes bibliographical references.
Thesis (M.S.)--Michigan State College of Agriculture and Applied Science. Dept. of Geology and Geography, 1954. Includes bibliographical references (leaf 49).
View normal to paleoflow of (A) a relatively large and (B) a relatively small turbidity current confined by a lateral slope. Note the gradual increase in dip from the basin floor onto the confining slope. Larger flows are more likely to deposit sandstone onto steeper, unmodified slopes by virtue of their greater thickness and their weaker grain-size stratification compared to smaller flows. 
Interpretation of the flow regime at the Braux pinch-out section in map view, showing flow deflected to run parallel with the slope. The accurate correlations between the sections permit plan-form dispersal patterns to be determined (interpretation following that of Kneller and McCaffrey, 1999). 
Stratigraphic trapping at pinch-out margins is a key feature of many turbidite-hosted hydrocarbon reservoirs. In systems confined by lateral or oblique frontal slopes, outcrop studies show that there is a continuum between two geometries of pinch-out configuration. In type A, turbidites thin onto the confining surface—although the final sandstone pinch-out is commonly abrupt—and individual beds tend not to erode into earlier deposits. In type B, turbidite sandstones commonly thicken toward the confining slope, and beds may incise into earlier deposits. These two types may occur in combination, to give a wide spectrum of pinch-out characteristics. Our analysis suggests the principal control in determining pinch-out character is flow magnitude, with smaller flows producing type A and larger flows producing type B. In areas of poor seismic control it can be difficult to assess either pinch-out character or the proximity of wells to confining slopes. Because estimates of paleoflow magnitude can be made from core or high-quality log image data, however, it is possible to make reasonable estimates of pinch-out character even from wells such as exploration wells, which may be placed conservatively, away from the field margins. Furthermore, systematic paleoflow variations and thickness trends are commonly seen in individual turbidite sandstones as they approach confining slopes. For example, dispersal directions indicate flow deflection parallel with the strike of confining topography; beds thin toward type A onlaps and thicken toward type Bonlaps. These relationships can be exploited via analysis of vertical successions to constrain well position with respect to the slope. Similarly, the presence, location, and frequency of locally derived debrites can provide information on the presence and proximity of confining slopes.
Typescript (photocopy) Thesis (M. Sc.)--Colorado School of Mines, 1999. Bibliography: leaves 114-120. Thesis advisor: Neil F. Hurley, Dept. of Geology and Geological Engineering. 2-3 1/2 in. computer disks in pocket.
This poster was presented at the Eastern Section American Association of Petroleum Geologists (AAPG) conference in Kalamazoo, Michigan, September 25-29, 2010. This study investigates kerogen petrography, gas desorption, geochemistry, and micro- and mesoporosity of the New Albany Shale (Devonian-Mississippian) in the eastern part of the Illinois basin. Core analysis from two locations, one in Owen County, Indiana and one in Pike County, Indiana was conducted. The volumes of gas in the locations studied are primarily dependent on total organic carbon (TOC) content and the micropore volume of the shales. Gas origins were assessed using stable isotope geochemistry, whereas maturity assessments utilized both measured and modeled Ro values. Different depths of burial and formation water salinities are likely responsible for dominant origins of the gas in the two locations studied. The shallower Owen County location (415 to 433 m deep) contains significant microbial methane, whereas the Pike County location (832 to 860 m deep) is characterized exclusively by thermogenic gas. Despite differences in the gas origins, the total gas in both locations is similar, reaching up to 2.2 cm3/g (70 scf/ton). The lower thermogenic gas content at the shallower location (probably because of the lower thermal maturity and possibly higher loss of gas related to uplift and leakage via relaxed fractures) is compensated by additional generation of microbial methane most probably stimulated by influx of glacial meltwater causing both brine dilution and microbial inoculation. The characteristics of the shale of the Maquoketa Group (Ordovician) in the Pike County location indicate that the controls on the gas volumes are similar to those in the New Albany Shale.
Replacement matrix dolomite (RMD) is present throughout the Leduc/Cooking Lake Formation, but is restricted to the bank margin in the Swan Hills Formation. RMD has an average crystal size of 140$ mu$m and fluoresces yellow in the Leduc/Cooking Lake Formation but has an average crystal size of 250$ mu$m and fluoresces green in the Swan Hills Formation. RMD formed before the onset of stylolitization. It has abundant inclusions, a homogeneous red cathodoluminescent response, and similar trace element concentrations in both formations. $ delta sp{18}$O values overlap for the most part, but some Swan Hills dolomites are 1 to 2$ perthous$ lighter in $ delta sp{18}$O. The Leduc/Cooking Lake dolomite has a slightly greater range in $ delta sp{13}$C, with several samples lighter than +1.5$ perthous$. Diagenetic fluids derived from seawater are supported by average $ delta sp{13}$C, $ delta sp{18}$O (1.77$ perthous$, $-$4.19$ perthous$; 2.81$ perthous$, $-$4.95$ perthous$), and $ sp{87}$Sr/$ sp{86}$Sr (.7082;.7086) values in the Leduc/Cooking Lake and Swan Hills dolomite respectively. Yellow fluorescence and pyrolysis parameters in the Leduc/Cooking Lake dolomite could be caused by the presence of mature organic compounds.
DISSERTATION (PH.D.)--THE UNIVERSITY OF MICHIGAN Dissertation Abstracts International,
Thesis--University of South Carolina, 1974. Includes bibliographical references (leaves 32-34). Photocopy.
Seismic profiles and drilling show that the Quaternary (late Pleistocene and Holocene) lagoon reefs in the south-central Belize Lagoon have grown on topographic highs constructed by fluvial, deltaic, and/or marine processes. The unique (rhomboidal and long-sinuous) reefs are derived from the underlying early Pleistocene river morphology (Victoria River) rather than from a fault-dominated karst morphology. -from Authors
Graphs on 2 folded leaves in pocket. Thesis (M.S.)--University of California, Riverside, 1988. Includes bibliographical references (leaves 43-47).
Thesis (M.S. in Geology)--S.M.U. Includes bibliographical references (leaves 158-168).
Thesis (Ph. D.)--University of Oklahoma, 1993. Includes bibliographical references. Photocopy.
A coupled study of the kinematics of thrusting and hydrocarbon maturation has been carried out in the An orthern and central sub-Andean belt of Bolivia to define the petroleum potential of the area. In addition to the classic Devonian source rock (Tomachi-Tequeje formations to the north and Iquiri-Limoncito formations in the central area), two other source rock intervals are recognized: the Retama Formation (Upper Devonian-Lower Carboniferous) and the Copacabana Formation (Upper Carboniferous-Lower Permian). These are the most prospective units in northern Bolivia and are of marine origin. The structural style varies from north to south due to variations in the sedimentary column involved in the thrusts. The erogenic front was guided by the northern boundary of a Paleozoic sedimentary wedge. In the Boomerang area, this boundary is oriented obliquely to the regional shortening and controlled the development of a prominent transfer zone. To the north, the thrusts are wider and the amount of shortening increases. The western part of the northern sub-Andean zone is characterized by a very thick Tertiary piggyback basin fill. Two phases of hydrocarbon maturation are recognized. The first began in Early Carboniferous and affected mostly Devonian strata. Formation of structural traps during this period occurred rarely. The entire basin was then deeply eroded in Permian-Jurassic time, causing any hydrocarbons that may have formed to be lost. The second phase of maturation was contemporaneous with Andean deformation and with the resulting burial under the Tertiary cover in the foreland basin and in piggyback basins on thrust structures. The hydrocarbon expelled during this period may fill the Andean anticlines. The known source rocks are not proven to be gas prone, but current discoveries indicate a high gas to oil ratio that may be due to secondary cracking in the source rock. Because the initial potential of the source rocks is low, expulsion of heavy compounds is expected to be weak.
Typescript (photocopy). Thesis (M.S.)--University of Texas at Arlington, 1984. Includes bibliographical references (leaves 196-200).
Typescript (photocopy). Thesis (M. Sc.)--Colorado School of Mines, 2000. Includes bibliographical references (leaves 149-156). Thesis advisor: Neil F. Hurley, Dept. of Geology and Geological Engineering. 1-4 3/4 in. computer laser optical disk in pocket.
Large amounts of organic carbon were de­ posited and preserved in marine sediments of late Bar- remian through middle Albian and late Cenomanian- earty Turonian age owing to the development of poorly oxygenated oceanic water masses and expanded oxy- § en minimum zones during "oceanic anoxic events." ediments rich in organic carbon which were depos­ ited during such events are thick sequences of basinal black shale or mudstone, thin black beds in shelf chalks, and thin beds and lenses in rudist reef and associated limestones. Analysis of the stratigraphic distribution of both known oil and giant oil-field reser­ voirs by many workers has indicated that a large part of the world's oil is of Mesozoic age and that most giant reservoirs are in rocks of Mesozoic age. We pro­ pose that the relative abundance of Mesozoic oil in the world oil picture is in part the result of maturation of organic carbon deposited during Cretaceous oceanic anoxic events. Many giant fields of Cretaceous age have reservoirs of shallow-water carbonate complexes such as rudist reef and associated fades buildups. We propose that the oil in such reservoirs originated as follows: (1) dur­ ing middle Cretaceous marine transgressions, equable world cHmate with high sea-surface temperatures pre­ vailed and led to carbonate reef buildups on shallow shelves and marginal platforms; (2) at the same time marine oxygen-nilnlmum zones expanded and deeper basinal oxygen deficits were Intensified owing to the lack of strong ocaanic mixing because of stable densi­ ty stratificatio n and possible low oceanic thermal gra­ dients; (3) these oxygen deficits enhanced the preser­ vation of organic carbon in basin, slope, and some shelf fades; (4) later Cretaceous transgression result­ ed in the drowning of the carbonate buildups which were then sealed under a cap of fine-grained hemipe- iagic sediment; interim regressions resulted In en­ hancement of porosity of reef fades and may have al­ lowed deposition of interbedded sand bodies in some sections; (6) many of these carbonate complexes and source beds were buried to suitable depths by Late Cretaceous and Tertiary clastic wedges and, depend­ ing on local geothermal gradients, hydrocarbon matu­ ration in the black stiale basinal fades occurred. These hydrocartions niigrated to shelf-edge reservoirs, such as platform cart)onate rocks, through intermediate fa­ des. This scenario with its combination of oceano- graphic and geokigic events led to development of fields such as those in the Golden Lane in Mexico. Thus, prime exploration targets are deeply buried ru­ dist buMuBs that are stratigraphically linked to basinal black shaw source tieds. Such buildups should be found on subsided passive margins of low to middle latitude regions; the source beds formed where nearly contemporaneous low-oxygen conditions obtained in adjacent basins.
Thesis (M.S.)--University of Wisconsin, Milwaukee, 1984. Includes bibliographical references (leaves 96-99). Photocopy.
Thesis (M.S.)--University of Southwestern Louisiana, 1996. Fifteen folded leaves of plates in pocket. Includes bibliographical references (leaves 50-52).
Thesis (M.S.)--University of Houston, 1988. Degree granted by Dept. of Geosciences. Includes bibliographical references (leaves 268-278).
Photocopy of typescript. Ann Arbor, Mich. : University Microfilms, 1978. Thesis--University of Oklahoma.
Thesis (M.S.)--University of Houston Central Campus, 1981. Degree granted by Dept. of Geology. Includes bibliographical references (leaves 170-190).
Printout. Thesis (M.S.)--University of Illinois at Urbana-Champaign, 1972. Includes bibliographical references (leaves 38-40).
Porosity reduction during mechanical compaction of a sediment generally has been assumed to be controlled by the increase in vertical effective stress, which is convenient because vertical stress profiles may be readily calculated from density logs. Poroelasticity theory shows, however, that mean effective stress controls porosity reduction. According to published data, horizontal stresses increase with overpressure, as well as with depth, so mean stress and vertical stress profiles are poorly correlated in overpressured sections. We have used wireline logs to compare the pore pressures estimated in mudrocks by relating porosity to mean effective stress and to vertical effective stress for overpressured Tertiary sections in southeast Asia. Wells from three different basins were studied. Mudrock porosities were estimated from the sonic log response and sorted by lithology according to the natural gamma-log response. Two sets of normal compaction curves, relating porosity to mean effective stress and to vertical effective stress, were determined empirically by fitting data points where the pore pressure was thought to be hydrostatic. These curves were then used to estimate the minimum pore pressure corresponding to mudrock porosity values in the overpressured sections. The pore pressures inferred using the mean effective stress are consistent with direct measurements of pore pressure in the adjacent sands. In contrast, pore pressures inferred in mudrocks using the vertical effective stress are significantly lower for the overpressured sections, implying discontinuities in the pore pressure profiles at lithological boundaries, which cannot readily be explained. We conclude that the pore pressures estimated using the vertical effective stress are wrong and that empirical relationships between porosity and vertical effective stress should not be used for estimating pore pressures: porosity should be empirically related to mean effective stress instead.
3 folded, col. plates in pocket. Vita. Thesis (M.A.)--University of Texas of the Permian Basin, 2000. Includes bibliographical references (p. 141-145).
New regional (two-dimensional) seismic reflection data, published Deep-Sea Drilling Project-Ocean Drilling Program reports and, unpublished shallow-offshore well information characterize the Mesozoic-Cenozoic evolution of the western Iberian continental slope north of 38 degrees 45'N. Two distinct sectors bounded by first-order transfer faults exist between the Galicia Bank and the Nazare fault. The northernmost sector I is filled by Triassic-Aptian (pre-breakup) sequences, reaching more than 3.5 s two-way traveltime (TWTT) in thickness in distinct half grabens. Salt pillows, salt ridges, minibasins, and salt-detached overburden faults were generated during the Mesozoic and reactivated in the Cenozoic. Sector 2 shows Triassic-Jurassic units more than 2.0 s TWTT thick under, lying cast-tilting half grabens of Early Cretaceous age. Salt structures in this sector evolved into mature salt diapirs. Postbreakup units are up to 2.0 s TWTT thick in both sectors. The evolution of the study area replicates evolutionary settings that have previously been proposed for nonvolcanic passive margins. However, some distinct features are noted: (1) widespread Triassic-Berriasian units deposited over rotated tilt blocks represent the early rifting stage; (2) Early Cretaceous subbasins showing rift-climax units, most likely formed during the advanced rifting stage, are spatially constrained to an approximately 100-km (62-mi)-wide region stretched along the continental slope; and (3) listric blocks and their associated low-angle (deep) detachment faults, formed on the distal margin during the advanced rifting and transition to sea-floor spreading stages, show no developed rift-climax units above them. From the early rifting stage onward, Mesozoic faults and halokinetic structures induced local differences in the thickness and character of seismic facies. Cenozoic (Alpine) tectonism promoted the reactivation of older Mesozoic structures.
The authors discuss the structural, sedimentologic and faunal characteristics of the shallow-subsurface deposits of the northern Florida Atlantic inner shelf. The northern Florida continental shelf is a submerged coastal-plain surface ranging in width from 15 mi (25 km) off Cape Canaveral to 68 mi (110 km) near Georgia. Study of more than 1,134 n. mi. (2,100 km) of high-resolution seismic-reflection profiles, nearly 200 vibratory cores, and four borings, from the inner shelf provides some insight into the Neogene evolution of this sector of the Atlantic shelf. Seismic-reflection profiles of the shallow subbottom to 500 ft (152 m) below the sea floor show six distinct reflection units and five prominent reflectors of regional significance. 41 refs.
Thesis (M.S.)--Texas A & M University, 2001. Includes bibliographical references (leaves 55-56). Vita. "Major subject: Geology."
Thesis (Ph. D.)--McMaster University, 1977. Includes bibliographical references (leaves 292-314). Microfiche (negative). s
A study of deposition in the swash-backwash zone along a sand beach indicates that fluctuations in sea level relative to beach water table level, resulting from semidiurnal tide cycles, produce appreciable effects on sediment distribution. In the swash-backwash zone, sediment distribution is dependent on the interaction of swash deposition, swash erosion, backwash deposition and backwash erosion. When the tide level is high and the beach water table is low, swash deposition and swash erosion predominate; this results in the formation of a thick sediment lens on the shoreward side of the swash-backwash zone and a scoured area on the surf side of the zone. In contrast, a relatively high water table results in maximum backwash erosion and backwash deposition; thick sediment lenses form near the surf boundary. Therefore, as sea level fluctuates above and below the general water table level with the tide, the zone of deposition correspondingly shifts its position within the swash-backwash zone and either increases or decreases the gradient of the beach slope. As the tide rises, sediments deposited by previous swashes are redistributed by the encroaching surf. Above the limit of surf encroachment and in the highest swash-mark area, a berm forms, which displays an onlap-offlap series of laminae; also, portions of it are cross-laminated. This berm and its internal structure are a result of sedimentation during the flood-to-ebb tide period.
Seismic reflection profiles from the Straits of Florida, Northwest Providence Channel, Tongue of the Ocean, and Exuma Sound reveal a seismic stratigraphy characterized by a series of prograding Upper Cretaceous and Tertiary seismic sequences with seismic velocities generally less than 4 km/sec overlying a Lower Cretaceous section of low-amplitude reflections which are more nearly horizontal than the overlying prograding clinoforms and have seismic velocities greater than 5 km/sec. The prograding units are detrital shallow-water carbonates shed from nearby carbonate banks into deep intrabank basins that were established in the Late Cretaceous. The Lower Cretaceous units are probably shallow-water carbonate banks that were drowned in the middle Cretaceous but which, during the Early Cretaceous, extended from Florida throughout the Bahamas region. The seismic reflection profiles reveal a sharp angular unconformity at 5-sec two-way traveltime in northwest Tongue of the Ocean, suggesting a rift-drift unconformity and deposition on thinned continental crust. No such unconformity is seen in central and southeast Tongue of the Ocean or in Exuma Sound, suggesting that these areas are built on oceanic crust.
Thesis (M.S.)--San Diego State University. Includes bibliographical references (leaves [76]-81).
Specific objectives of this study were to ascertain the nature of the transition from deep sea to continent and to define more clearly the physiography, boundaries, lithology, structure, and tectonic style of the Baja California borderland. Seismic-reflection profiling data reveal that the California borderland south of about 31 degree 30 prime N is dominated by a ridge-trough-ridge-trough-shelf pattern. Lithology of the Baja California borderland is varied. Rocks are similar to those on the California borderland and mainland of southern California. Lithology, structures, and timing and style of deformation suggest that accepted plate-tectonic models for the region are incomplete.
Thesis (M.S.)--University of Kansas, Geology, 1968. Includes bibliographical references.
An ooid sand barrier bar of Pleistocene age was deposited along the seaward side of an ooid shoal complex southwest of Miami, Florida. The bar is 35 km long, about 0.8 km wide, elongate parallel with the trend of the ooid shoal complex and perpendicular to channels between individual shoals. A depression 1.6 km wide, interpreted as a back-barrier channel, isolates the bar from the ooid shoals. During sea-level fall and subaerial exposure of the bar, the ooid sand was cemented in place, preventing migration of the barrier. No Holocene analogue of this sand body is recognized, perhaps because of the relative youthfulness of Holocene ooid shoals. This Pleistocene ooid shoal complex, with its reservoir-size barrier bar, may serve as a refined model for exploration in ancient oid sand belts.
Along the south Texas margin, a vast carbonate-shelf complex with an extensive barrier-reef system and abundant shallow-lagoon and skeletal-shoal deposits existed during the Aptian to Albian. The Sligo Formation represents more than 609.6 m (2000 ft) of deposition along this margin. Facies types along the shelf edge were quantitatively delineated by cluster analysis of detailed point-count data from 90 thin sections of whole cores from five wells. In addition, studies of 42.6 m (140 ft) of core slabs and thin sections of well cuttings from four other wells were used to establish a regional depositional model. Along the Sligo shelf edge, three major facies occur: reef or reef rubble (two subfacies), back reef (three subfacies), and lagoonal (two subfacies). Reef facies are dominated by caprinids and also contain solenoporid algae, stromatoporoids, and an assortment of corals. Behind the reef, a spectrum of extensive back-reef deposits interfinger with shallow (< 5 m), lagoonal sediments. Farther behind the shelf-margin reef complex, along the outer shelf, benthic foraminifera, peloids, and ooids were deposited in high-energy shoals, and are interbedded with low-energy lagoonal sediments. The two types of buildups probably existed along the Sligo shelf margin and the equivalent Cupido shelf margin to the south: (1) wave-resistant coral-caprinid-stromatoporid barrier reefs (adjacent to restricted lagoonal facies), and (2) low-lying rudist banks (adjacent to diverse, washed lagoonal facies).
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