Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 30 of 126
Full-Text Articles in Entire DC Network
High-Resolution Facies Analysis Of Deltaic Subenvironments Of The Pennsylvanian Atoka Formation, Arkansas., Tanwi Gangopadhyay
High-Resolution Facies Analysis Of Deltaic Subenvironments Of The Pennsylvanian Atoka Formation, Arkansas., Tanwi Gangopadhyay
LSU Historical Dissertations and Theses
The present research was aimed at comparison and distinction between various deltaic subenvironments from Pennsylvanian deposits of the Arkoma Basin, Arkansas. Detailed facies analysis of deltaic deposits reveal significant variation in sedimentary characteristics between different subenvironments. A multi-pronged approach, including documentation of measured sections and gamma ray profiles in the field and subsequent laboratory analysis of samples, was undertaken. The Atoka Formation deltaic deposits have been established primarily as representing fluvially-dominated deltas. Interdistributary bay fill deposits are splintery shales with abundant siderite nodules. Crevasse splay sandstone units are ripple cross-laminated and coarsen and thicken upward to a maximum of 60cm …
Tectonics And Sedimentation: The Evolution, Tectonic Influences And Correlation Of The Tanqua And Laingsburg Subbasins, Southwest Karoo Basin, South Africa., Erik Douglas Scott
Tectonics And Sedimentation: The Evolution, Tectonic Influences And Correlation Of The Tanqua And Laingsburg Subbasins, Southwest Karoo Basin, South Africa., Erik Douglas Scott
LSU Historical Dissertations and Theses
The Tanqua and Laingsburg subbasins developed in the southwest corner of the Karoo Basin, South Africa, during the late Permian. The subbasins had near-contemporaneous formation and filling, and each contain a number of submarine fans. Five submarine fan systems in the broad, shallow Tanqua have a lateral continuity of up to 34km. With a sandstone/shale ratio of 75-90%, the arenaceous fans vary in thickness from 20 to 60m. Intervening shales range from 20 to 75m. Four fan systems in the more typical foredeep style Laingsburg subbasin are thicker and a few hundred kilometers long. The history of both subbasins was …
Characterization Of Thin-Bedded Turbidites From The Permian Tanqua Karoo Submarine Fan Deposits, South Africa., Debnath Basu
Characterization Of Thin-Bedded Turbidites From The Permian Tanqua Karoo Submarine Fan Deposits, South Africa., Debnath Basu
LSU Historical Dissertations and Theses
Thin-bedded turbidites (TBTs, 5-60 cm) constitute a common facies in fine-grained deep-water clastic environments. Proper characterization of these deposits are lacking due to the scarcity of well preserved outcrops exposing TBTs and the difficulty in resolving them by conventional subsurface logging methods. The objective of this study is to characterize TBTs developed in a variety of laterally contiguous depositional environments in a submarine fan. These deposits are well exposed in the Permian Tanqua Karoo subbasin, South Africa. The subenvironments studied include upper mid-fan channel levee-overbank, mid-fan passive channel fill, lower mid-fan channel-sheet transition, and lower-fan distal sheet deposits. Field and …
Holocene To Late Pleistocene Stratigraphy Of The Mahakam Delta, Kalimantan, Indonesia., Johan C. Sydow
Holocene To Late Pleistocene Stratigraphy Of The Mahakam Delta, Kalimantan, Indonesia., Johan C. Sydow
LSU Historical Dissertations and Theses
Late Pleistocene depositional cycles of the Mahakam shelf contain stratal geometries that indicate a progradational continuum, from falling stage in sea level through to initial rise. These findings contrast with popular sequence stratigraphic concepts which predict that large, rapid sea-level falls, typical of the Late Pleistocene, should result in sediment bypass of the entire shelf. The Mahakam shelf is a mixed siliciclastic-carbonate depositional setting. Extensive, thick carbonate buildups are produced by prolific green algal Halimeda bioherm accretion during transgression and highstand flooding of the shelf. The 60 by 200 km study area lies within 2$\sp\circ$ of the equator, in the …
Active Tectonics Of The Northeastern Mojave Desert, California., David F. Macconnell
Active Tectonics Of The Northeastern Mojave Desert, California., David F. Macconnell
LSU Historical Dissertations and Theses
This study has led to an improved understanding of the active tectonics and seismic hazards of the northeastern Mojave Desert region and has provided a means with which to assess regional strain models proposed by previous workers. Primary data sets include published and unpublished geologic maps, Landsat Thematic Mapper multi-spectral imagery, SPOT panchromatic imagery as well as hand-held ground and aerial photographs (panchromatic, color and color-infrared), color video, digital topography, gravity, seismicity and paleomagnetic data. Prior to analysis, data sets were organized into a geographic information system implemented on a UNIX workstation. This allowed for the simultaneous visualization of combinations …
Tectonic Subsidence Of The Cretaceous Western Interior Basin, United States., Ming Pang
Tectonic Subsidence Of The Cretaceous Western Interior Basin, United States., Ming Pang
LSU Historical Dissertations and Theses
The tectonic subsidence history recorded in middle Cenomanian to early Campanian (96 to 80 Ma) strata in the U.S. Cretaceous Western Interior basin was studied by applying two-dimensional flexural backstripping techniques to six regional stratigraphic sections across different segments of the basin. Results indicate that tectonic subsidence over the 16 m.y. study interval consists of two distinct components: a westward-increasing flexural subsidence confined within a few hundred kilometers of the thrust belt, and a spatially uniform "residual" subsidence that affected the entire basin. The residual subsidence does not represent signals of eustatic sea level changes but instead reflects epeirogenic movements …
Stratigraphy, Diagenesis, And Petroleum Geology Of The Smackover Formation, Southwest Alabama., William James Wade
Stratigraphy, Diagenesis, And Petroleum Geology Of The Smackover Formation, Southwest Alabama., William James Wade
LSU Historical Dissertations and Theses
The sequence stratigraphic framework of the Smackover Formation and other Jurassic strata in southwest Alabama is delineated, with the objective of eventual correlation of equivalent sequences across the northern Gulf. Additionally, geologic controls on the diagenesis of organic matter in the Smackover Formation are examined, in order to better understand organic-inorganic interaction and hydrocarbon evolution during burial. Jurassic systems tracts of southwest Alabama differ significantly from those of the north central Gulf in that they show profound influence of antecedent topography, consequent large continental clastic influx, and a subsidence history less influenced by thermal cooling. Norphlet siliciclastics constitute a continental …
Tectonic Implications Of Fission-Track Thermochronology And Amphibole Thermobarometry Studies Of The Northern Peninsular Ranges Batholith, Southern California., Peter Gillham George
Tectonic Implications Of Fission-Track Thermochronology And Amphibole Thermobarometry Studies Of The Northern Peninsular Ranges Batholith, Southern California., Peter Gillham George
LSU Historical Dissertations and Theses
Fission-track data from the San Jacinto Mountains and the Palomar Mountain-Escondido study area indicate that the Late Cretaceous history of the Peninsular Ranges batholith is marked by a series of major cooling events. Coupled with geobarometry measurements and field observations, these data allow for a greater understanding of the nature and timing of both local and regional tectonic events. In the eastern Peninsular Ranges, west-vergent thrusting along the Santa Rosa mylonite belt at $\sim$99-94 Ma was followed by major extensional faulting between $\sim$94 and 92 Ma. Amphibole geobarometry of mylonites indicate that $\sim$10-18 km of crustal thickening occurred as a …
Geologic And Physical Processes At A Gulf Of Mexico Tidal Inlet, East Pass, Florida., Andrew Morang
Geologic And Physical Processes At A Gulf Of Mexico Tidal Inlet, East Pass, Florida., Andrew Morang
LSU Historical Dissertations and Theses
East Pass, a tidal inlet located in the Florida Panhandle between Pensacola and Panama City, connects Choctawhatchee Bay to the Gulf of Mexico. A three-phase model has been developed which describes the behavior of East Pass inlet during the last 120 years, based on wave, current, tide, bathymetric and shoreline data, and on historical records. The first phase (pre-1928) is of spit development and breaching. This phase covers the period when the pass was oriented in a northwest-southeast direction between Choctawhatchee Bay and the Gulf. From 1928 to 1968, the second phase was characterized by a stable throat position but …
Origin Of A Coarse-Grained Shallow Marine Sandstone Complex: The Coniacian Tocito Sandstone, Northwestern New Mexico. (Volumes 1 And 2)., Gregory Wayne Riley
Origin Of A Coarse-Grained Shallow Marine Sandstone Complex: The Coniacian Tocito Sandstone, Northwestern New Mexico. (Volumes 1 And 2)., Gregory Wayne Riley
LSU Historical Dissertations and Theses
Study of the Coniacian Tocito Sandstone, one of the shale-encased, shallow marine sandstone complexes in the Cretaceous Western Interior Basin, indicates that transport of coarse sediment to distal marine locations was accomplished by an increase in the efficiency of the marine dispersal system (tidal currents). Enhanced tidal currents were a consequence of bathymetric variations formed by uplifts along the pre-existing Four Corners Lineament system. The Tocito Sandstone forms an entirely marine, progradational-transgressive sequence and overlies an unconformity localized along uplifted submarine highs. The lower progradational strata represent the marine portion of a tide-dominated delta that prograded into a tectonically-created "embayment", …
Stratigraphic Architecture Of An Extensional Orogen: The Mojave Extensional Belt, Southern California., Christopher John Travis
Stratigraphic Architecture Of An Extensional Orogen: The Mojave Extensional Belt, Southern California., Christopher John Travis
LSU Historical Dissertations and Theses
Field-based studies and quantitative models provide new insights into the stratigraphic architecture of a developing continental extensional orogen. The early Miocene age Mojave Extensional Belt of southern California (MEB) exhibits a tripartite stratigraphy, consisting of (1) pre- to early synextension volcanic deposits, unconformably overlain by (2) syntectonic basement-derived megabreccia and breccia with local finer-grained units, overlain by (3) a posttectonic fining-upward sequence of gravel, sand, shale, and limestone. On a more local scale, stratigraphy and sediment dispersal within the MEB reflect the evolution of the major tectonic elements of the belt: (1) Breakaway zone. Strata of the western Newberry Mountains …
Thermohaline And Hydrocarbon Related Diagenesis Of Lower Miocene And Upper Oligocene Sediments, West Hackberry Field, Cameron Parish, Louisiana: Implications For Mass Transport And Fluid Flow., Kathleen Mary Mcmanus
Thermohaline And Hydrocarbon Related Diagenesis Of Lower Miocene And Upper Oligocene Sediments, West Hackberry Field, Cameron Parish, Louisiana: Implications For Mass Transport And Fluid Flow., Kathleen Mary Mcmanus
LSU Historical Dissertations and Theses
The diagenesis of Lower Miocene and Upper Oligocene sediments flanking the West Hackberry salt dome are documented in order to determine the effect the presence of salt domes may have in driving diagenetic reactions in detrital siliciclastic sediments. These sediments have undergone significant chemical diagenesis during progressive burial resulting in a reduction in porosity and permeability. Precipitation of analcime, siderite, and calcite plus the alteration of detrital volcanic lithic fragments and replacement of aluminosilicate framework grains by calcite are the dominant reactions which have altered the Upper Oligocene sands. Analcime and siderite are also present in the Oligocene mudstones. The …
Analysis Of Lacustrine Deltaic Sedimentation In The Green River Formation, Southern Uinta Basin, Utah. (Volumes I And Ii)., Robert Reginald Remy
Analysis Of Lacustrine Deltaic Sedimentation In The Green River Formation, Southern Uinta Basin, Utah. (Volumes I And Ii)., Robert Reginald Remy
LSU Historical Dissertations and Theses
Detailed lithofacies analysis of over 4,500 m of measured sections of most of the Eocene portion of the fluvial and lacustrine Green River Formation in the south-central Uinta Basin documents twelve lithofacies: Sa (nonsinuous trunk streams), Sb (meandering delta distributary channels), Sc (amalgamated delta mouth bars), Sd (regressive deltaic sandsheets), Se (overbank and shallow-lacustrine sandsheets), Sf (crevasse channels and splays), C (passively-filled abandoned channels), Mg (subaqueous mudflats), Mr (subaerial mudflats), L (lake-margin carbonate flats), and Ia and Ib (open-lacustrine deposits). The lower half of the study section consists of the carbonate marker unit (130 m) and the overlying Sunnyside delta …
The Geology And Stratigraphic Evolution Of The North-Central Part Of The Early Archean Barberton Greenstone Belt, South Africa., Louise Dorothy Hose
The Geology And Stratigraphic Evolution Of The North-Central Part Of The Early Archean Barberton Greenstone Belt, South Africa., Louise Dorothy Hose
LSU Historical Dissertations and Theses
The north-central part of the 3.5 to 3.2 Ga Barberton greenstone belt, southwest of the town of Barberton, contains both the northern and southern facies of the Swaziland Supergroup including, from base to top, the Onverwacht, Fig Tree, and Moodies Groups. The facies are divided by the Inyoka Fault, a major thrust fault that was reactivated by dextral shearing. The two facies of Fig Tree and Moodies strata appear to be laterally gradational. The Moodies Group, a 2800+ m sequence of predominantly lithic arenite, sublitharenite, and arkosic arenite was studied in four large, structurally isolated blocks in the north-central part …
Petrogenesis And Provenance Of Epiclastic Volcanic Cobbles From The Cretaceous Woodbine Formation, Southwest Arkansas., Christina Lee Livesey
Petrogenesis And Provenance Of Epiclastic Volcanic Cobbles From The Cretaceous Woodbine Formation, Southwest Arkansas., Christina Lee Livesey
LSU Historical Dissertations and Theses
Whole rock and mineral compositions of epiclastic volcanic cobbles have been used to reconstruct the evolution of the magmatic system that supplied this volcanic material. Using techniques that have been applied to stratified volcanic deposits, the chemical and mineralogical variation of volcanic material preserved as cobbles in sedimentary rocks has been used to identify a cogenetic suite of igneous rocks and to evaluate possible fractionation mechanisms. Volcanic rocks, preserved as rounded cobbles in the upper Cretaceous Woodbine Formation of SW Arkansas, range from mafic, pyroxene-rich phonolites to felsic, crystal-poor phonolites. Felsic lithologies contain abundant sanidine phenocrysts and lesser amounts of …
Fission Track Thermochronology: Methods And Applications In Tectonics., Steven Matthew Jones
Fission Track Thermochronology: Methods And Applications In Tectonics., Steven Matthew Jones
LSU Historical Dissertations and Theses
Time, temperature and the kinetics of reactions are the basic ingredients in this study of thermal history analysis. Unraveling the timing of geological events using absolute dating systems based on radioactive decay is not a trivial task, ages given by most radiometric dating techniques (e.g. fission track analysis) are apparent ages, related to cooling through some characteristic temperature range. Fission tracks are atomic-scale defects in a crystal caused by the passage of fragments from the fission of uranium-238. In apatite, fission tracks are destroyed by annealing at temperatures between $\sim$70$\sp\circ$C and $\sim$125$\sp\circ$C. A quantitative understanding of the kinetics of track …
Transgressions And Regressions In The Barataria Bight Region Of Coastal Louisiana. (Volumes I And Ii)., Douglas Ross Levin
Transgressions And Regressions In The Barataria Bight Region Of Coastal Louisiana. (Volumes I And Ii)., Douglas Ross Levin
LSU Historical Dissertations and Theses
At least three delta progradations have contributed to the Barataria geologic framework since 5000 ybp. The Bayou des Families lobe was first (4600 to 3600 ybp) followed by Bayou Blue (2600 and 1900 ybp) and then the Mississippi lobe (1000 ybp to the present). A flooding surface separates the (lower) Bayou des Families from the Bayou Blue progradation (above). The shoreface of the Bayou des Families transgression lies seaward of the present Barataria shoreline. This transgression lasted approximately one thousand years. A flooding surface also separates the Bayou Blue progradation from the Mississippi Delta lobe. This (Bayou Blue) transgression lasted …
Neogene Basin Evolution In The Southwestern Dominican Republic: A Foraminiferal Study., Peter Paul Mclaughlin Jr
Neogene Basin Evolution In The Southwestern Dominican Republic: A Foraminiferal Study., Peter Paul Mclaughlin Jr
LSU Historical Dissertations and Theses
The Azua Basin sequence is a 2500 m thick Miocene Pliocene regressive interval. Limestones and marls of the Sombrerito Formation, the lowermost unit, ranges from lower Miocene to lowermost upper Miocene. The turbidite sequence of the Trinchera Formation spans an interval from uppermost middle Miocene to lower Pliocene. Blue-green, neritic lower Pliocene siltstones of the Quita Coraza Formation overlie the Trinchera in the seaward part of the basin. Shallow-marine strata in the lower part of the Arroyo Blanco Formation range from uppermost Miocene to middle Pliocene. Principal Components Analysis of rich benthic foraminiferal faunas aided in the recognition of species …
Stratigraphy And Sedimentology Of Holocene Overbank Deposits Of The Mississippi River, False River Region, Louisiana., Kathleen Marie Farrell
Stratigraphy And Sedimentology Of Holocene Overbank Deposits Of The Mississippi River, False River Region, Louisiana., Kathleen Marie Farrell
LSU Historical Dissertations and Theses
The Holocene flood basin along a meander belt margin of the Mississippi River includes two principal geomorphic features: a flat featureless natural levee, and a system of anastomozed, entrenched crevasses with intervening splay lobes. Levee and splay lobe deposits are identical and consist of thinly (cm) to minutely (mm) rhythmically layered sand, silt and clay which are pervasively disrupted by unlined meniscate burrows of the trace fossil, Muensteria. Pelletal fabrics develop where overlapping backfilled burrows completely obliterate primary stratification so that only traces of small ripple laminations and parallel laminations are preserved. Pelletal silt is the most extensive lithology present. …
Geomorphic And Stratigraphic Evolution Of The Middle Amite River Valley, Southeastern Louisiana., Whitney Joseph Autin
Geomorphic And Stratigraphic Evolution Of The Middle Amite River Valley, Southeastern Louisiana., Whitney Joseph Autin
LSU Historical Dissertations and Theses
Many streams of the northern Gulf of Mexico coastal plain have similar geomorphic and stratigraphic character and comparable influences on their drainage basin evolution. Potential geomorphic influences on floodplain morphology vary temporally and spatially in their effect and include inherent geomorphic processes, eustatic sea level rise, evolution of a stream's receiving basin, adjustment to active tectonics, and local climate fluctuation. A 14.3-km segment of meander belt in the middle Amite River valley in southeastern Louisiana was selected to test the relative effect of geomorphic factors on Holocene floodplain evolution. Floodplain evolution in this valley responded to sea level rise and …
Carbonaceous Cherts Of The Swaziland Supergroup, Barberton Mountain Land, Southern Africa., Maud Maureen Walsh
Carbonaceous Cherts Of The Swaziland Supergroup, Barberton Mountain Land, Southern Africa., Maud Maureen Walsh
LSU Historical Dissertations and Theses
The well-preserved carbonaceous cherts of the early Archean (3,200 to 3,500 Ma) Swaziland Supergroup of the Barberton Greenstone Belt, South Africa contain fossils that are among the Earth's oldest. Fossils are rare in the carbonaceous cherts, however. Petrographic and geochemical analyses of the carbonaceous cherts yield information useful to the study of early life and to the general question of the nature of silicification of early Archean rocks. The filamentous microfossils whose morphologies, as well as the texture of the encompassing laminations, suggest an affinity to modern microbial mat-dwelling cyanobacteria or bacteria, are the most probable biological structures identified during …
Stratigraphic Framework And Sedimentary Facies Of A Clastic Shelf-Margin: Wilcox Group (Paleocene-Eocene), Central Louisiana., Philip Lowry
Stratigraphic Framework And Sedimentary Facies Of A Clastic Shelf-Margin: Wilcox Group (Paleocene-Eocene), Central Louisiana., Philip Lowry
LSU Historical Dissertations and Theses
A strike-oriented trend of Wilcox oil and gas production in central Louisiana marks the location of an early Tertiary clastic shelf-margin. The shelf-margin contained a central unstable region flanked by two stable regions. The stable regions occurred where there was no significant progradation beyond the location of the underlying shelf-margins. Conversely, the unstable region occurred where progradation extended basinward of the underlying shelf-margins. Seven depositional sequences can be recognized within the shelf-margin. The vertical arrangement of these sequences shows that migration of the margin was negligible throughout Wilcox deposition, thereby suggesting a balance between subsidence and deposition. Through numerical simulation, …
Parameters Of Peat Formation In The Mississippi Delta (Holocene)., Elisabeth Catharina Kosters
Parameters Of Peat Formation In The Mississippi Delta (Holocene)., Elisabeth Catharina Kosters
LSU Historical Dissertations and Theses
The Mississippi Delta consists of six major Holocene deltaic complexes, that each had a life-span of about 1500 years. Emphasis of this study is on autochthonous peats of Barataria Basin, a large-scale interdistributary basin, between levees of the LaFourche and St. Bernard/Plaquemine deltas. A 6 m. thick set of lithostratigraphic units constitutes the aggradational basin-fill. Organic-rich beds occur in three phases, each representing an accumulating period that was interrupted by subsidence and the influx of detrital clastics from renewed nearby fluvio-deltaic sedimentation. Peats accumulated in eutrophic, non-domed environments in fresh water swamps and (often floating) marshes and average 81.7% organic …
Late Quaternary Facies And Sea Level History, Southwest Louisiana Continental Shelf., John Robert Suter
Late Quaternary Facies And Sea Level History, Southwest Louisiana Continental Shelf., John Robert Suter
LSU Historical Dissertations and Theses
Abstract Not Available.
Mud Deposition At The Shoreface: Wave And Sediment Dynamics On The Chenier Plain Of Louisiana., George Paul Kemp
Mud Deposition At The Shoreface: Wave And Sediment Dynamics On The Chenier Plain Of Louisiana., George Paul Kemp
LSU Historical Dissertations and Theses
Sedimentological data, and high-resolution current velocity time-series were acquired nearshore along the muddy coast of Louisiana's chenier plain. Results suggest that the 2 to 10 cm thick, laminated and graded silt/shell + mud beds which characterize shoreface mudflat sedimentation form through intermittent dumping of fluid mud suspensions. Cohesive and non-cohesive sediments are first separated and concentrated by shear within a wave boundary layer (WBL). Rapid sedimentation, or "freezing", of the mud fraction occurs when the yield strength of the fluid mud suspension equals that of the WBL shear stress. Incident waves were well described by shallow water linear wave theory, …
Sedimentology And Stratigraphy Of The Fig Tree Group, West Limb Of The Onverwacht Anticline, Barberton Greenstone Belt, South Africa., Bruce William Nocita
Sedimentology And Stratigraphy Of The Fig Tree Group, West Limb Of The Onverwacht Anticline, Barberton Greenstone Belt, South Africa., Bruce William Nocita
LSU Historical Dissertations and Theses
Sedimentary rocks of the 3.2-3.2 Ga old Fig Tree Group in the southwest part of the Barberton Greenstone Belt in South Africa can be divided into three informal formations. The lowest unit, Formation A, is composed mostly of silicified pyroclastic debris and carbonaceous cherts. Formation B has four lithofacies--siltstone; sandstone; jaspilite; and bedded barite. Two coarse-grained lithofacies make up Formation C. In the western portion of the study area there is chert-clast conglomerate and in the eastern part of the study area is volcanic-clast conglomerate, breccia, and sandstone. In the western portion of the study area Formations B and C …
Stratigraphy, Sedimentology, And Sedimentary Petrology Of The Early Archean Coongan Formation, Warrawoona Group, Eastern Pilbara Block, Western Australia (Sandstones, Precambrian)., Michael J. Dimarco
Stratigraphy, Sedimentology, And Sedimentary Petrology Of The Early Archean Coongan Formation, Warrawoona Group, Eastern Pilbara Block, Western Australia (Sandstones, Precambrian)., Michael J. Dimarco
LSU Historical Dissertations and Theses
The Coongan Formation, defined and described here, is an approximately 3.5 Ga-old unit of felsic volcanic and volcaniclastic rocks, representing a major episode of early Archean felsic volcanism, in the predominantly basaltic Warrawoona Group, eastern Pilbara Block, Western Australia. The Coongan Formation is divided into three members: the Duffer and Panorama Members and the Strelley Pool Chert. The oldest and volumetrically greatest part of the Coongan Formation is the Duffer Member, which consists largely of volcaniclastic breccia, conglomerate, tuff, and felsic lava. Vertical sequences, up to 5 km thick, indicate that the Duffer Member represents coarse-grained, shoaling-upward debris-aprons that flanked …
Origin And Sedimentary Characteristics Of Discrete Sand Beds In Modern Sediments Of The Central Texas Continental Shelf (Storm, Hurricane, Geostrophic, Waves, Turbidities)., John William Snedden
Origin And Sedimentary Characteristics Of Discrete Sand Beds In Modern Sediments Of The Central Texas Continental Shelf (Storm, Hurricane, Geostrophic, Waves, Turbidities)., John William Snedden
LSU Historical Dissertations and Theses
Thin (1-9 cm) discrete beds of sand and silt are present in the clayey modern sediments of the Texas shelf. Observation of seaward size-grading within the beds indicates that the source of the clastics is the adjacent coastal zone. Consideration of the nature of wave and current processes during storms and the dimensions of possible coastal sub-environment sources suggests that the shoreface supplied the sand found in the discrete sand beds. The seaward grading and along-shelf continuity of a correlative horizon dated as having been deposited during the passage of Hurricane Carla in 1961 imply that transport was along-shelf but …
Diagenesis Of Cenozoic Limestones On Enewetak Atoll (Dolomite, Neomorphism, Radiaxial)., Arthur Henry Saller
Diagenesis Of Cenozoic Limestones On Enewetak Atoll (Dolomite, Neomorphism, Radiaxial)., Arthur Henry Saller
LSU Historical Dissertations and Theses
Cores from Enewetak Atoll afford an excellent opportunity to study diagenetic alteration in carbonates from the modern sediment-water interface to burial depths of over 1,300 m. Intensity of diagenetic alteration in Cenozoic carbonates on Enewetak is largely a function of time which strata have been in diagenetic environments with active water circulation. In Pleistocene strata deposited in back-reef environments, diagenesis is dominated by meteoric processes including dissolution of aragonite, calcite cementation, and alteration of aragonite and high-magnesian calcite (HMC) to low-magnesian calcite (LMC). Petrographic and stable isotope data suggest that aragonite neomorphism occurred by a process of partial delicate intrafabric …
Stratigraphy, Sedimentology, And Geologic Evolution Of Eastern Terraba Trough, Southwestern Costa Rica (Tectonics, Forearc Basin)., Peter B. Yuan
Stratigraphy, Sedimentology, And Geologic Evolution Of Eastern Terraba Trough, Southwestern Costa Rica (Tectonics, Forearc Basin)., Peter B. Yuan
LSU Historical Dissertations and Theses
Sedimentary rocks of eastern Terraba Trough, southwestern Costa Rica, were deposited in a fore-arc basin developed at an ocean-ocean convergent boundary. The basin developed in Middle to Late Eocene when the Farallon Plate began its subduction beneath the Caribbean Plate. Shallow-water carbonates of the Brito Formation were deposited on shoals of basement blocks. These were surrounded by deeper-marine areas in which volcaniclastics and carbonate debris accumulated. The Brito Formation consists of algal-foraminiferal packstone to grainstone, rudstone, and rare wackestone formed in force-slope, carbonate buildup, and open platform environments in a warm, tropical sea. The environmental conditions remained unchanged during the …