bluuebunny/crossref_metadata_2025_split huggingface dataset:
DEPOSITION, POROSITY EVOLUTION, AND MODES OF SULFATE EMPLACEMENT IN THE UPPER SMACKOVER, EDGEWOOD FIELDS, VAN ZANDT COUNTY, TEXAS
Authors: WICKLAND DAVID C. , JACKA ALONZO D. 
Published: October 2019

ABSTRACT
Cores and cuttings from the upper Smackover Formation, Edgewood fields, northern Van Zandt County, East Texas, were analyzed to determine depositional facies, diagenesis, and porosity evolution. Edgewood fields lie on an anticlinal structure formed by a salt pillow in the East Texas Basin. Structural growth began during deposition of the Smackover Formation and continued until the end of deposition of the Cotton Valley Formation.
Major lithofacies in the Smackover Formation consist of oograinstone, oopisograpestone grainstone, oobiopelwackestone-packstone, anhydrite, quartzose sandstone, and sandy carbonate, with grainstone and packstone being predominant.
Secondary oomolds and intercrystalline pores constitute the major types of preserved porosity. Although large volumes of primary intergranular porosity initially existed in the lime sands, nearly all of this porosity has been occluded first by submarine cements and later by dolomite, anhydrite, and calcite cements.
Evidence indicates that most of the anhydrite in the upper Smackover Formation is of a diagenetic origin and nonevaporitic. Some thin anhydrite layers are present in the formation and may represent sabkha deposits, but they lack certain characteristics that are typical of modern sabkhas, such as pseudomorphs of gypsum crystals, enteroliths, mud crack casts, flat pebble conglomerates, stromatolites, and fenestral cavities. No example of subaqueous evaporites was noted.
Diagenetic anhydrite occurs in the following modes and morphologies: (1) sparry or felted-lath anhydrite, which was precipitated as a cement in primary and secondary voids; (2) abundant anhydrite, which was precipitated as cement subsequently replaced outwardly, invading the surrounding matrix or grains to form nodules, porphyroblasts, or intensively replaced layers; (3) felted-lath anhydrite which occurs as scattered replacement nodules, or which coalesce to form dense mosaics or massively replaced layers; and (4) replacive sparry anhydrite which was emplaced as scattered porphyroblasts and which locally coalesced to form massively replaced intervals.
Most of the anhydrite was emplaced in grainstones and packstones which had been deposited in relatively high-energy subtidal environments. Dolostones that have been replaced intensively by anhydrite contain abundant inclusions of corroded dolomite crystals and relict fabrics of the carbonate. Initially, much anhydrite nucleated in organic-rich grains, such as ooids, shells, or peloids. In some intervals, thalassinoid burrows have been replaced selectively by anhydrite.
In most carbonate intervals, dolomitization preceded anhydritization. In many intervals, emplacement of anhydrite was followed by influx of a lower salinity fluid that dissolved the anhydrite, precipitated a calcite cement, replaced the anhydrite with calcite, and/or brought about dedolomitization.
BULK DENSITY, VELOCITY, AND POROSITY RELATIONSHIPS IN TERTIARY SANDSTONES OF SOUTHWEST LOUISIANA
Authors: JANSSEN JAMES C. , NUNN JEFFREY A. 
Published: October 2019

ABSTRACT
Information from wells in Cameron and Vermilion parishes of southwest Louisiana was utilized in an empirical study of density, velocity, and porosity relationships in sandstones. Data from Oligocene to Pliocene sediments, ranging in depth from 3,000 to 17,000 feet, were compared to show the range and variability of these parameters with depth and one another. Results are compared with experimentally derived rock properties to evaluate the dominant physical and chemical factors affecting the sediments with increasing depth of burial. For comparison purposes, a smaller study of the velocity, density, and depth relationships in shales was included.
Although observations are consistent with the anticipated results of increasing density and velocity and decreasing porosity with depth, they do not follow simple linear or exponential patterns. Bulk density increases more rapidly with depth as increasing temperature and pressure weaken individual quartz grains causing greater compaction. Sonic transit time decreases (velocity increases) more slowly with depth because the rate of increase in the elastic constants of the rock becomes less as it compacts under a relatively constant rate of compression (i.e., the rate of increase in rigidity and bulk modulus decreases as the rock becomes more compact). An increase in transit time at depth observed in some sandstone units is related to a decrease in effective grain to grain pressure caused by geopressured pore fluids and possibly by increased porosity resulting from greater silicate solubility. Clean sandstone porosity decreases more rapidly with depth and shows a strong negative correlation with the bulk density-depth trend.
Relationships among density, velocity, and porosity are also complex. Although velocity is inversely proportional to density in a homogeneous solid, velocity increases with increasing bulk density in the sandstones. This phenomenon is due to the effect of increasing elastic moduli of the rock associated with porosity reduction dominating the effect of increasing bulk density. As mentioned above, clean sandstone porosity has a strong negative correlation with bulk density, indicating that the physical and chemical factors influencing them are the same.
PETROGRAPHY, RESERVOIR QUALITIES, AND DEPOSITIONAL SETTING OF THE HOWELL SAND, DEEP UPPER WILCOX, EAST SEVEN SISTERS FIELD, DUVAL COUNTY, TEXAS
Authors: D’Agostino Anthony 
Published: October 2019

Abstract
The deep Upper Wilcox Howell Sand was cored in two wells in the East Seven Sisters Field, Duval County, Texas. Three hundred and seven feet (15,010-15,317 feet) were recovered from the ARCO Humble Fee No. 2 and one hundred and sixty-three feet (15,183-15,346 feet) from the Exxon Farmers Life G.U. 1-3. The Howell Sand is the principal reservoir among a group of deltaic sands tested in this field. It is a wedge-shaped delta-front deposit of fine-grained sand interbedded with dark gray, slightly pyritic marginal marine and inner neritic shales. The deposit is backed up by a major growth fault which produced thickening and a rollover structure. Maximum thickness is approximately 300 feet, thinning in three directions, away from the fault and along strike.
Examination of logs and cores and interpretation of sedimentary structures, trace fossils, and grain size trends has revealed three microfacies within the Howell Sand. The facies represent three stages of deposition and subsidence of the sand body in a delta-front setting.
Examination of rock samples in thin section and with a SEM/EDs system has shown that the porosity present is attributable to secondary processes in most cases. Excellent deliverability in a limited area of the reservoir is achieved through the preservation of primary intergranular pores. Primary porosity is estimated to be 25 per cent of the total porosity in the so-called “sweet spot” of the reservoir.
The trapping mechanism is a combination of structural closure and favorable diagenetic facies as porosity and permeability slowly fade out away from the “sweet spot” which is somewhat off-structure.
INNER CONTINENTAL SHELF OFF SOUTHWEST FLORIDA
Authors: DAVIS RICHARD A. , JEWELL PLINY , SUSSKO ROGER J. 
Published: October 2019

ABSTRACT
The inner continental shelf off southwest Florida is a shallow, low-energy environment that displays many of the characteristics of ancient epicontinental and pericontinental seas. The gradient is about 1:3,000, mean annual wave height is less than 0.5 m, and tides are in the lower microtidal range.
This inner shelf area contains two distinct provinces. The northern one near Cape Romano is characterized by tide-dominated quartz sand ridges, whereas the southern province contains a transition from siliciclastic to carbonate sand.
The area of WNW-trending linear sand ridges extends for about 30 km south of Cape Romano. These ridges range from a few to 10 km in length and have a relief of up to 4 m with an asymmetric profile. Sediments on the ridges are well-sorted, fine quartz sand and are covered with various types of bedforms including ripples, megaripples, and sand waves. Swales are less well-sorted with a relatively high shell content. Tidal currents in this area typically peak at 50-60 cm/sec during spring tidal cycles and about half that during neap tides. They show bidirectional patterns with little time-velocity asymmetry.
South of the linear ridge complex and north of Florida Bay is a broad, gently sloping shelf that is subjected to very low wave and tidal energies. The 10 m isobath is approximately 35 km from the coast. The transition zone from siliciclastic sediment in the north to carbonate sediment in the south is several kilometers wide and trends generally WNW.
SAND TRANSPORT KINEMATICS ON THE TEXAS CONTINENTAL SHELF DURING HURRICANE CARLA, SEPTEMBER 1961
Authors: SNEDDEN JOHN W. , NUMMEDAL DAG 
Published: October 2019

Abstract
Using available wind, tide, and wave data, it has been possible to reconstruct the kinematics of sand transport during Hurricane Carla, which made landfall at Pass Cavallo, Texas in September, 1961. The analysis indicates that the peak bed shear stress occurred just prior to hurricane landfall. The quasi-steady shelf flow was driven by the wind-induced sea-level slope and consequent hydrostatic pressure gradient forces. The downwelling bottom current probably was oriented obliquely offshore and along-shelf to the southwest. Integration of hindcast wave data with the proposed bottom flow patterns allows development of a descriptive model for the combined-flow transport pathway for sand and silt. This model suggests a regional transport pattern characterized by offshore transport from shoreface sources near the point of hurricane landfall and weak onshore flow on the southern part of the Texas shelf. This kinematic reconstruction is compatible with the observed strike-trending morphology of a thin (&lt; 10 cm), regional sand bed deposited during the storm.
The shelf sand transport model developed here differs considerably from an earlier explanation for the Carla sand bed which invokes turbidity currents generated during the ebb phase of the storm surge following hurricane landfall. The combined-flow reconstruction indicates that it is unnecessary to call upon post-storm processes to explain the occurrence or areal distribution of the sand bed deposited during this storm.
ORIGIN, DEPOSITIONAL PATTERN, AND RESERVOIR CHARACTERISTICS OF MIDDLE MIOCENE SHALLOW-MARINE SANDSTONES, OFFSHORE SOUTH TEXAS
Authors: MORTON ROBERT A. , JIRIK LEE A. 
Published: October 2019

Abstract
Moderate volumes of dry gas are produced in the South Padre Island Area of offshore south Texas from a 120-m-thick aggregation of mixed shoreface and shelf sandstones that are interbedded with thin neritic shales. These shallow marine sediments aggraded on a broad stable shelf platform during the middle Miocene depositional episode when block faulting and basin filling within the Rio Grande Rift disrupted regional drainage patterns and caused an abrupt decrease in sediment supply to the Rio Grande Embayment. Because sediment influx to south Texas was significantly reduced, middle Miocene sandstones were deposited less than 10 km landward of the previous shelf edge, which was constructed during the early Miocene (pre-Amphistegina B) regressive episode.
Thick, widespread marine shales, containing the Cibicides opima and Textularia stapperi faunal assemblages, occur beneath and above the sequence of nearshore sediments. The Textularia stapperi transgressive shale serves as the primary seal for hydrocarbon accumulation that is preferentially trapped on the upthrown side of minor down-to-the-west faults. These reactivated early Miocene faults did not significantly influence middle Miocene sediment distribution or interval thickness except near the contemporaneous slope.
Individual sandstone reservoirs of the delta fringe and mid-shelf facies are 3 to 12 m thick and exhibit thin interbedded to upward-coarsening log responses. They form laterally-persistent but irregular sand sheets that pass landward into either thick coastal-plain sandstones or embayment mudstones, they merge updrift (northeastward) into fluvial-deltaic sandstones, and they grade seaward into slope mudstones. Progressive basinward and southwestward decreases in net sandstone thickness and sandstone percent indicate predominant sediment transport by shelf currents in the same directions. Repetitive cyclic depositional events are also indicated by the nearly uniform vertical spacing of sandstone beds near their southwestern pinchout.
Shallow reservoir depths (~ 1500 m, 5000 ft) and relatively young sediment age suggest that the hydrocarbons trapped in middle Miocene sediments originated in older Tertiary shales and migrated into the shelf sandstone reservoirs when early Miocene faults were reactivated. The presence of humic organic matter in Miocene sediments and high thermal gradients within the Rio Grande Embayment probably are responsible for the predominance of methane which results from cracking of previously generated hydrocarbons.
SEQUENCE STRATIGRAPHIC INTERPRETATION OF CONIACIAN STRATA IN THE SAN JUAN BASIN, NEW MEXICO
Authors: Nummedal Dag , Swift Donald J.P. , Kofron Bruce M. 
Published: October 2019

ABSTRACT
Detailed measured sections, subsurface data and regional observations along the southern and western margins of New Mexico’s San Juan Basin provide a precise data base for testing proposed sequence stratigraphic models which describe the architecture of depositional sequences. It is concluded that Coniacian strata in this basin represent lithosomes deposited during relative sea level lowstand and subsequent transgressions. The base of the Torrivio Member of the Gallup Sandstone records the landward, unconformable Coniacian sequence boundary. The uppermost tongues (C-A) of the Gallup Sandstone and the associated upper member of the Lower Mancos Shale represent the lowstand wedge. The base of this wedge is the seaward, mostly conformable, continuation of the basal Torrivio sequence boundary. In distal shelf settings, beyond the influence of the Gallup highstand deposits (highstand systems tract), the sequence boundary merges with the condensed section of the next underlying sequence—the Juana Lopez Member of the Mancos Shale.
The Tocito Sandstone represents a set of linear shelf sand ridges which formed during transgressions associated with parasequence boundaries within this regressive lowstand wedge. Ridge-building also continued into the overlying transgressive systems tract. Dominant ridge-building currents were along-shelf tidal flows, partly modified by geostrophic storm flows.
As articulated in sequence stratigraphy, analysis of the genetic linkage between contemporaneous depositional systems and the associated relative sea level stage is a powerful tool in stratigraphic and sedimentological analysis. The many conflicting interpretations already published on the Gallup-Tocito stratigraphy partly owe their origin to a lack of appreciation for the direct connection between styles of sedimentation and patterns of relative change in sea level.
MODELING OF HYDROCARBON-RELATED CARBON ISOTOPIC ANOMALIES IN SUBSURFACE EXPLORATION WELLS OF THE NORTHERN GULF OF MEXICO
Authors: WILLIAMS DOUGLAS F. , LERCHE IAN , SPERO HOWARD J. , TRAINOR DWIGHT M. , FALLS W. FRED , GUILDERSON THOMAS , KIRSCHENMANN KYLE 
Published: October 2019

ABSTRACT
Fine-grained (&lt;63 μm) carbonate from Plio-Pleistocene exploration wells, offshore Louisiana and Trinidad, has δ13CPDB signatures of about -50 to -10 ‰. In this paper we explore two hypotheses that appear to account for these negative δ13C anomalies. The first hypothesis is that the negative δ13C signatures observed in Green Canyon block, offshore Louisiana, are due to authigenic subsurface precipitation of fine-grained carbonate as a record of past migration pathways of hydrocarbons through subsurface Plio-Pleistocene sands. The second hypothesis is that the authigenic δ13C signatures record precipitation at or near the sediment-water interface and thus record the past locations of hydrocarbon seeps on the northcentral margin of the Gulf of Mexico. Preliminary geochemical and petrographic evidence is presented to examine these hypotheses. Within the limitations of not knowing past pore fluid chemistries, we also attempt to use the δ18O signatures of the &lt;63 μm carbonate to estimate the paleotemperatures, and perhaps paleodepths and timing, of emplacement of the negative δ13C signatures.
The potential that this isotopically negative carbonate acts as a geochemical recorder or tracer of hydrocarbon movement makes documentation of this phenomenon important to offshore exploration efforts.
Development and Stratigraphy of Three Rooker Bar; A Recently Emergent Barrier Island, Pinellas County, Florida
Authors: Gibbs Ann E. , Davis Richard A. 
Published: October 2019

ABSTRACT
The emergence of Three Rooker Bar over the past 22 years has presented a unique opportunity to document, through a combination of aerial photography and field observations, the depositional processes and morphologic changes associated with the formation of the island. Three Rooker Bar is situated within the only major gap in the otherwise continuous barrier island coast of Pinellas County Florida, between Honeymoon Island and Anclote Key. The island is bounded to the west by the eastern Gulf of Mexico and by the relatively shallow St. Joseph Sound to the east. The island first became emergent in 1969, although much of its growth has occurred within the last few years. It is essentially pristine and undeveloped, approximately 2 km long and nearly 20 m at its widest spot. The island has a stable, vegetated back beach and dune complex, extensive shoals off the southern end and well developed algal covered tidal flats which overly back barrier washover deposits.
Twenty two vibracores, taken throughout the area, are the basis for three Holocene lithofacies which represent six depositional environments including barrier island, back barrier washover, nearshore bar, coastal bay, and mangrove/salt marsh. Lithofacies are defined based on mud content, shell content and taxonomy, organic content, sedimentary structures and similarity to modem surface sediment deposits. Excellent aerial photo coverage allows direct correlation of these lithofacies with the physical processes which led to their deposition. Absolute interpretation of the depositional environments of these facies is therefore possible.
Results of this method of correlation have led to the interpretation of in-place, upward shoaling of linear sand bars as the primary mode of island formation. Continued growth as well as periodic breaching of topographically lower areas, can be expected for this island in the future.
TIME-SERIES ANALYSIS OF BEACH MORPHOLOGY, PINELLAS COUNTY, FLORIDA
Authors: McKenna Kimberly K. , Davis Richard A. 
Published: October 2019

ABSTRACT
Monthly beach surveys were conducted for three and one half years (1985-1989) at eleven stations along the Pinellas County, Florida shoreline from northern Clearwater Beach Island to southern Long Key. The coast is microtidal, mixed wave- and tide-energy, with a mean annual wave height of 30 centimeters and a mean wave period of four seconds. Tropical storms and low-pressure systems produce high-energy wave conditions and are prime components in eroding the beaches. Time-distance maps of beach profiles show morphologic changes of the shoreline in response to storms and “normal” wind and wave conditions. Wave refraction analyses, incorporating digitized Pinellas offshore bathymetry and common wave conditions, suggest that even low relief offshore features generate wave patterns that erode or maintain a particular beach.
The area contains a nearly continuous seawall from North Clearwater Beach to Pass-a-Grille. Armored beaches, where seawalls are located within the spring tidal range, have shown sizeable sediment loss of the subaerial beach but limited nearshore profile changes. The performance of unstabilized beaches, where the seawalls are situated above spring high tide or behind protective dunes, ranged from substantial volumetric gain at the North Clearwater Beach location to considerable loss at northern Long Key despite nourishment. Seasonal fluctuations in shoreline movement were limited due to low energy conditions. Beaches with similar shoreline orientation and nearshore gradients displayed similar morphologic trends.
MINERAL AND ORGANIC MATTER ACCUMULATION RATES IN DELTAIC COASTAL MARSHES AND THEIR IMPORTANCE TO LANDSCAPE STABILITY
Authors: Nyman John A. , DeLaune Ronald D. 
Published: October 2019

ABSTRACT
Marsh deposits may occupy little of a profile, but the environments they represent may be long lived. Marsh longevity depends partly on the deposition of mineral and organic matter to counter relative sea level rise, or submergence. Understanding soil formation in Louisiana’s rapidly subsiding coastal marshes may provide insights relevant to other coastal marshes if global sea-level rise increases as expected.
Mineral and organic matter accumulation rates required to prevent flooding stress on marsh vegetation in a submerging environment are partially dependent on whether the marsh is fresh, brackish, or saline. Estimates of the rates of mineral matter accumulation required for a marsh surface submerging at 1 cm yr-1 range from 424 gr m-2 yr-1 in fresh, to 1,798 gr m-2 yr-1 in saline marsh. Mineral requirements likely vary in response to the availability of SO4-2, which reduces to a plant toxin, but which is buffered by soil iron. Estimates of the rates of organic matter accumulation required range from 1,969 gr m-2 yr-1 in fresh to 1,136 gr m-2 yr-1 in brackish marsh. Organic requirements vary because of differences in the decomposition rates of plants in the different marsh types.
Another aspect of increasing rates of global sea-level rise is increased marine influences in tidal fresh and brackish marshes, i.e., increased tidal flushing and availability of sea salts such as NaCl and SO4-2, which cause shifts in plant communities. This is important because mineral matter accumulation must almost double for Spartina alterniflora to occupy brackish marsh areas experiencing increased marine influences. Thus even though vertical accretion may initially keep pace with submergence, we hypothesize that if increasing marine influences accompanies submergence, brackish marsh may be more likely to convert to open water than to saline marsh. This may be a factor in the rapid conversion of Louisiana’s brackish marsh to open water. If the rate of global sea-level rise increases, other brackish marshes with low soil bulk density may be similarly threatened.
Rapid Erosion of A Cohesive Shoreline, Sargent Beach, Texas
Authors: Stauble Donald K. , Burke Cheryl E. , Levin Douglas R. 
Published: October 2019

ABSTRACT
One of the areas of highest coastal erosion along the Texas coast is located in the deltaic headland coastal segment of the Brazos River in the vicinity of Sargent Beach. Because of this erosion, a section of the Gulf Intracoastal Waterway (GIWW) from Cedar Lakes to East Matagorda Bay is in danger of intrusion from breaching of the narrow (less than 300 m wide) shorefront. Owing to its deltaic origin, the beach is composed of cohesive fine grained clay and silt material, overlain by a narrow layer of coastal peat and topped by a thin veneer of fine grained quartz beach sand with a high percentage of shell fragments. The northeastern half of the study area has an average erosion rate of 6.7 m/yr and has a thin sandy flat sloping beach over the clay deposit. The southwestern section has up to a meter high clay bluffs outcropping into the surf zone and has an average 11 m/yr erosion rate. It is speculated that this high erosion rate is a result of intermittent wave cutting of large chunks of the clay bluff material. The overall erosion rate along this coast is due to a general lack of sand.