bluuebunny/crossref_metadata_2025_split huggingface dataset:
CHEMICAL ALTERATION OF SMACKOVER OILS AS A FUNCTION OF MATURATION
Authors: Sweeney R.E. 
Published: October 2019

ABSTRACT
The distribution of API gravities of Smackover oils is shown to be quantitatively related to the thermal maturity of the reservoirs. In addition, by comparison to the empirical limits of Waples (1980) and the theoretical limits of Quigley and MacKenzie (1988), it is shown that these maturities are too low for the thermal cracking reactions needed to produce the API gravity distribution.
The chemical composition data for 131 oils were obtained from the DOE database and correlations were made using 31 compositional parameters and the API gravity of the whole oils. Strong correlation coefficients are shown to exist between oil gravity and the composition of the higher carbon-number molecular groups. These correlations suggest that ‘in reservoir’ oil cracking reactions do occur in Smackover reservoirs. Therefore, the rate for these reactions must be enhanced (Sassen and Moore, 1988) over those predicted by laboaratory studies and considered typical for other areas.
Sassen (1988) suggests that ‘thermochemical sulfate reduction’ is the process responsible for early crude oil destruction in Smackover reservoirs. This process has been shown to significantly alter the oil composition in Paleozoic reservoirs of the Big Horn Basin (Orr, 1974). However, early crude oil destruction (i.e., high gravity oil in low maturity reservoirs) does not occur in the Big Horn Basin reservoirs. Therefore, it is concluded that the high gravity oil in low maturity reservoirs of the Smackover formation is, generally, not due to thermochemical sulfate reduction. It is suggested that the API gravity-maturity trend for the Smackover oil family is governed by kinetic parameters related to the composition of the initial ‘type’ oil, especially the frequency factor ‘A’ of the Arrhenius kinetic equation.
ORGANIC GEOCHEMISTRY OF GASES AND CONDENSATES FROM BLOCK 511A HIGH ISLAND SOUTH ADDITION OFFSHORE TEXAS, GULF OF MEXICO
Authors: WALTERS CLIFFORD C. 
Published: October 2019

ABSTRACT
Chemical and isotopic data obtained on gases from High Island 511A indicate that the reservoirs contain hydrocarbons from multiple sources. A significant portion, 17 to 34 percent, of the produced methane is biogenic. Thermogenic gases were generated from a single source lying at depths greater than 16,000 feet, considerably deeper than the Pleistocene reservoir sands. Condensates coproduced with natural gas were also studied. Chromatographic analysis revealed that the condensates possess very unusual compound distributions, atypical of light petroleum fluids derived from phaseseparated crude oils or thermal cracking. Normal and branched alkanes are noticeably depleted, and cyclic hydrocarbons are enriched. Aromatic compounds are in exceptionally high concentrations. In the C9-C18 range, isoprenoid hydrocarbons are the dominant components. No one process appears to totally explain the atypical compositions of the High Island 511A condensates. A model was developed which is consistent with the compositional data and production history. Thermogenic natural gas-condensate from a single source charged the 511A Pleistocene reservoirs where biodegradation occurred to varying degrees. Hydrocarbons generated from terrestrial Type III kerogen in local immature sediments were extracted by the biogenic methane. As the biogenic methane accumulated in the sands, the extracted, low maturity thermal hydrocarbons were also added to the reservoir in roughly equal proportions as the high maturity thermogenic condensates. This resulted in condensates with a light hydrocarbon distribution characteristic of both immature and mature generation. Biodegradation and water washing may have further per-turbed the light hydrocarbon abundances. The geological situation which gave rise to the 511A immature condensates is common throughout the offshore Gulf of Mexico and may be responsible for many of the unusual light hydrocarbon distributions found in petroleums from this area.
A GEOCHEMICAL STUDY OF OILS FROM THE SOUTH PASS 61 FIELD, OFFSHORE LOUISIANA
Authors: Requejo A.G. , Halpern Henry I. 
Published: October 2019

ABSTRACT
Detailed geochemical analyses of twenty-three crude oils from various reservoirs in South Pass 61 field, offshore Louisiana, indicate that the oils belong to a single family and are derived from the same source. The large variation in bulk and chemical properties (e.g., API gravity, hydrocarbon composition) can be attributed to post-generative processes, most importantly biodegradation and evaporative fractionation. A third alteration phenomenon, which was noted only in a single sample, is gas deasphalting.
Triterpane and sterane biomarker distributions of the oils corroborate their common source. Maturity estimates based on sterane isomerization and alkyl phenanthrene distributions also indicate that the oils were generated at a similar level of maturity. However, the degree of sterane aromatization (% triaromatic sterane parameter), exhibits a wide range, and is not related to reservoir depth or other bulk properties of the oils. Hopane/sterane ratios also vary more than would be expected for a single family of oils. Both parameters are highly correlated with the absolute concentrations of 17α (H), 21β(H)-hopane and 5α(H),14α(H),17α(H)-ethyl cholestane (20R). The process(es) resulting in these biomarker correlations are uncertain.
A Case Study of The Preservation Potential of The Coastal Lithosomes of Small Deltaic Systems: Examples From The Holocene of The Texas Continental Shelf
Authors: Bartek Louis R. , Anderson John B. , Abdulah Kenneth C. 
Published: October 2019

ABSTRACT
An investigation of the Holocene stratigraphy of the coast and inner continental shelf in the area surrounding the modem Brazos Delta indicates that overstepped wave-dominated deltas are an important element of the transgressive systems tract of high sediment yield depositional systems. It appears as though the Brazos incised valley, which was carved during the Wisconsinan eustatic lowstand, was infilled or abandoned during an interval of rapid eustatic rise and that the fluvial-deltaic system then migrated onto the adjacent interfluve. The system appears to have stabilized during the 9,000 year B.P. eustatic still stand and nucleated a delta in an area that lies approximately 15 km offshore of the modern Brazos delta. This delta was transgressed during an ensuing rapid rise and was preserved as a shelf sand body. This routine was repeated at least two more times and has resulted in the generation of three shelf sand bodies. Deltas that were transgressed during intervals when the rate of eustatic rise was high (2 cm/year) have the highest preservation potential. During the intervals of rapid eustatic rise, the deltaic deposits are rapidly overstepped and the sand body is isolated on the shelf. During this process the upper couple of meters of the delta may be reworked into a strike aligned sand body, while the lower portion (&gt;2 meters below sea level (approximately 7 meters thick)-upper and lower shoreface equivalents) of the delta is preserved in place in its original pod-like geometry. These deltaic sand bodies lie beneath a ravinement surface, may be associated with the remains of the fluvial channel that fed them, and may be 10 meters thick. During intervals of slow eustatic rise (0.2 cm/yr) a large proportion of wave dominated deltas is reworked and less than 3 meters of the original deltaic facies may be preserved under the ravinement surface.
Evolutionary Classification of Coastal Sediments
Authors: Boyd Ron , Dalrymple Robert , Zaitlin Brian 
Published: October 2019

ABSTRACT
One of the most successful ways of classifying coastal environments has been to employ the dominant coastal process variables as discriminating parameters. This approach has been previously applied to deltas and continental shelves using the three parameters of waves, tides and rivers and to tidal inlets using only waves and tides. We suggest that a three parameter triangular classification can be extended to all coastal environments and enables a division into the primary categories of deltas, estuaries, barriers and tidal flats. Although combinations of coastal processes may remain constant through time on any coast, the coast itself undergoes continuous evolution. This necessitates the inclusion of time as a fourth parameter to satisfy an evolutionary coastal classification. If we adopt a sequence stratigraphic view of coastal evolution, then we may place most coastal sediments within either the transgressive or highstand systems tracts, undergoing either progradation (regression) or flooding (transgression). If we assume that all temporal evolution between sedimentary environments within the coastal system takes place during either a regression or transgression then we can substitute regression/transgression for time as the fourth parameter. Using this approach we see that all environments may occur in the general case but that at times of (maximum) flooding, estuaries predominate and that as sediment continues to be supplied during progradation, deltas, barriers and tidal flats expand at the expense of estuaries. At any one time, each depositional environment may be further subdivided using wave, tide and river process domination.
Land Loss Rates: Louisiana Coastal Plain
Authors: Britsch Louis D. , Kemp III E. Burton 
Published: October 2019

ABSTRACT
Land loss mapping and rate curve development for 62 quadrangles in the Louisiana Coastal Plain show that land loss rates vary significantly throughout coastal Louisiana. Differences in land loss rates among individual quadrangles are a function of the geologic setting, and the factors that contribute to land loss. Of the 62 quadrangles mapped, 16 show an increase in the land loss rate, 36 show a decrease, and 10 remained approximately the same. On a regional scale, the land loss rate for the entire Louisiana Coastal Plain has decreased from an average yearly rate of 41.88 square miles for the 1956-58 to 1974 period to 30.71 square miles for the 1974 to 1983 period.
The data generated during the land loss study is being combined with engineering geology, geomorphic, and subsidence data to determine the causes for land loss in site specific areas of the Louisiana coast. It will also be used to identify areas of maximum and minimum land loss so that mitigation efforts can be planned in areas where the potential for significant reduction in land loss is greatest.
Historical Changes in Shoreline Position Along the Mississippi Sound Barrier Islands
Authors: Byrnes Mark R. , McBride Randolph A. , Penland Shea , Hiland Matteson W. , Westphal Karen A. 
Published: October 2019

ABSTRACT
A computer-based shoreline mapping methodology, within the framework of a geographic information system, was used to compile and analyze changes in historical shoreline position and island area between 1847/49 and 1986 for the Mississippi Sound barrier island system. The data base consisted of three to four cartographic shorelines and one to two air photo interpreted shorelines. The dominant direction of movement for Dauphin, Petit Bois, Horn, and Ship islands is to the west, whereas cross-shore change in shoreline position is the primary mechanism by which the beaches on Cat Island respond to incident processes. Average shoreline change for the study area was about -1.7 m/yr; however, Horn Island illustrated no net shoreline change for the period of record and the western halves of Petit Bois and Ship islands were net progradational. Although spatial variability in shoreline movement was common, associated land loss was relatively consistent, ranging from -1.6 to -2.5 ha/yr.
The magnitude of lateral island migration is generally an order of magnitude greater than cross-shore movements. East of Dog Keys Pass, the islands are moving to the west by updrift erosion and downdrift accretion at rates exceeding 30 m/yr. The eastern end of Petit Bois Island illustrates the greatest lateral movement, averaging 89.9 m/yr between 1848 and 1986. Long-term changes recorded for the ends of Ship Island are significantly smaller, mainly due to dredging at the Biloxi navigation channel and distance from sand source, limiting the quantity of sand available for natural bypassing to the west. Short-term lateral migration trends illustrate a similar response at Horn Island Pass.
Management Implications of Sediment Dynamics in Delta Marshes of Louisiana
Authors: Cahoon Donald R. 
Published: October 2019

ABSTRACT
Sediment dynamics for the Louisiana coast are reviewed and compared to typical water management schedules for manipulated marsh impoundments to determine the potential for sediment deposition in managed marshes. The opportunity for sediment deposition and the availability of sediment for deposition along the Louisiana coast is greatest for sediment-poor regions during the passage of storms (i.e., cold fronts and tropical storms) and for areas near rivers during spring floods. Manipulated impoundments have been constructed in order to reduce the rate of water exchange between the marsh and adjoining canals as a means to combat the impacts of saltwater intrusion and increased tidal amplitude caused by the extensive network of canals in the coastal zone. The water management schedule (i.e., water flows and water levels) of these impoundments is usually based on the life cycle requirements of those plant and animal species targeted for management and does not necessarily coincide with the times of peak opportunity and availability of sediment for deposition. Hence, the achievement of management goals (e.g., the improvement of waterfowl and wildlife habitat) requires that wetland managers balance the short-term benefits of secondary production and the long-term benefits of sediment deposition in a rapidly subsiding environment. This may result in the manager consciously trading one resource for another, such as sediment and freshwater for low water levels and improved habitat for secondary producers, even in the sediment-rich environs of the Atchafalaya delta region. An evaluation of the trade-offs required by impoundment management and recommendations for maximizing sediment capture in the impoundments are presented.
Late Quaternary Deposition in the Apalachicola Embayment, Northwest Florida Coast
Authors: Donoghue Joseph F. 
Published: October 2019

ABSTRACT
The distribution and composition of the coastal and inner-shelf clastic sediments of northwest Florida have been strongly influenced by the activity of the Apalachicola River. The largest river in the northeastern Gulf of Mexico, the Apalachicola has dominated sedimentation in the region since Neogene time. High-resolution shallow seismic investigations of the inner shelf, combined with coastal borehole records, indicate that the bulk of the clastic sediment cover of the coast and inner margin is late Quaternary in age, and probably Sangamonian or younger. Late Quaternary sea level fluctuations have exerted a major influence on the timing and character of sedimentation in the Apalachicola Embayment.
VELOCITY DEPRESSION AND DEGASIFICATION SUBSIDENCE IN LOUISIANA WETLANDS
Authors: McGinnis Lyle D. , Johnson Donald O. , Zimmerman R. Eric , Isaacson H. Ronald , Penland Shea , Connor Paul E. 
Published: October 2019

ABSTRACT
Modern and ancient delta plains in Louisiana that border the northern Gulf of Mexico are undergoing unprecedented rates of land loss. Subsidence due to compaction and loss of pore water is believed to be one of the primary land loss factors, whereas subsidence due to gas emission is generally believed to play a significant role only in the upper one or two meters of a wetland. Evidence to the contrary is presented here that suggests that degasification subsidence is a more important mechanism contributing to land loss than previously thought. In addition, potential degasification subsidence can be quantified if the depression from normal compressional and shear wave velocities is known. Velocity reductions of 30 to 75% from compressional wave velocity in water and extending to depths of tens of meters have been observed in a saltwater marsh in Louisiana. An order of magnitude reduction in velocity due to the presence of free gas has been observed previously in gas-rich sediments on the adjacent continental shelf, where biogenic gas is observed to depths of 1 km or more. The ratio of normal to depressed compressional wave velocities is used to calculate potential degasification subsidence.
HUMAN IMPACTS ON COASTAL AND ESTUARINE ENVIRONMENTS IN MISSISSIPPI
Authors: Meyer-Arendt Klaus J. 
Published: October 2019

ABSTRACT
Although Mississippi’s toehold on the Gulf of Mexico extends less than 110 km from border to border as the crow flies, human modification of the coastal zone has been extensive. Two of the three major subcomponents of the state’s terrestrial coastal environment–the mainland shoreline, the estuarine embayments, and the barrier islands–have been substantially modified by human activity. Almost half of the 130 km long mainland shoreline has been altered by seawall construction and artificial beach nourishment. The wetland-fringed estuarine embayments of St. Louis Bay and Back Bay of Biloxi became popular loci of recreational development in the boom years of the 1950s and 1960s, and dredge-and-fill activity was widespread. Likewise, industrial development proceeded rapidly during that period, and not until passage of the Mississippi Wetlands Protection Law of 1973 did wetland modification become significantly reduced. Only the barrier islands have escaped extensive human alteration, although development plans have been (and still are) proposed from time to time. The erosion and destruction of the casino resort of Isle of Caprice (presently the Dog Keys shoals) in the 1930s effectively halted offshore resort development plans for several decades, and today three of Mississippi’s four barrier islands are included in the Gulf Islands National Seashore.
HOLOCENE GEOLOGIC FRAMEWORK OF THE TRINITY SHOAL REGION, LOUISIANA CONTINENTAL SHELF
Authors: Pope David L. , Penland Shea , Suter John R. , McBride Randolph A. 
Published: October 2019

ABSTRACT
The geologic framework and sand resources of Trinity Shoal were assessed for their suitability as construction aggregate and beach replenishment material. The study of Trinity Shoal was conducted in two phases. First, potential sand deposits on Louisiana’s continental shelf were identified from published nautical charts and bathymetric maps. A regional seismic survey was then conducted in the area, in which about 800 line-km of high-resolution seismic profiles were acquired and interpreted. The second phase of the study involved acquisition of vibracores. The vibracore locations were chosen from preliminary interpretation of the seismic data, and through analysis of historical and current coastal geomorphology.
From analysis of the seismic and core data, an isopach map, geologic cross-sections, and grain texture analyses were made. Texture, primary physical structures, and sequence associations were used to characterize sediment facies. Six depositional environments were delineated from the core and seismic data. The regressive depositional environments include: (1) prodelta; (2) delta fringe; and (3) distributary channel. The transgressive depositional environments include: (1) lagoon; (2) barrier; and (3) shoal. The shoal environment is represented by the marine sand body that caps Trinity Shoal, and is derived from reworking the underlying barrier facies. In contrast, the barrier environment is comprised of recurved spit, tidal inlet, washover, and sand sheet sub-environments.
Seismic profiles and core logs were integrated to calibrate the seismic facies with shoal and barrier environments interpreted from core analysis. The geologic cross-sections and the isopach map show the shoal and barrier sand thickness trend thinning in a general west to east direction across the study area. Shoal and barrier sand thickness exceed 8 m on the southern or seaward flank of Trinity Shoal. The shoal’s transgressive sand facies offer the best source of material for coastal erosion control projects in terms of volume and quality, with a calculated volume of about 2 billion m3.
Using High-Resolution Sequence Stratigraphic Studies Of Quaternary Strata To Develop Realistic Models For Predicting The Stratigraphic Occurrence Of Reservoirs
Authors: Banfield Laura A. , Rodriguez Antonio B. , Snow Jennifer N. , Anderson John B. , Abdulah Kenneth C. , Eckles Brenda J. , Sarzalejo Sabrina , Carney John L. 
Published: October 2019

An ongoing study utilizes outcrop-scale seismic data and lithofacies data from the Texas continental shelf to develop type sections or preliminary two dimensional depositional models that relate the distribution of sedimentary deposits to sequence stratigraphy. The approach examines the variability in the spatial and temporal distribution of systems tract deposits produced during the most recent glacial-eustatic cycle (the past 120,000 years). The current data base consists of nearly 20,000 kilometers of high-resolution seismic data (with vertical resolution of tens of centimeters to two meters) and lithologic data from hundreds of sediment cores and platform boring descriptions. Only with high resolution data can realistic depositional models be developed.
Detailed work has focused on several study areas (east Texas: Trinity/Sabine, east Texas: Brazos/Colorado, central Texas, and south Texas) that represent a range of depositional settings in terms of sediment supply, shelf gradient, climatic setting, and storm (wave) versus fluvial influence on sedimentation. On the east Texas shelf the transgressive and lowstand systems tracts contain most of the sand-prone deposits. On the central Texas shelf the sand-prone deposits are concentrated in the highstand systems tract. On the south Texas shelf the lowstand and transgressive systems tracts contain sand-prone deposits. Preliminary results suggest that observed trends in the stratigraphic occurrence of sand-prone units repeat themselves during successive glacial-eustatic cycles. This repetition is important because it indicates that these depositional patterns are predictable and therefore can be modeled.