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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Environment of deposition of selected sandstones and conglomerates in southern part of Cahaba basin, Alabama

Unknown Date (has links)
The Pottsville formation in the Cahaba basin, Alabama, contains conglomerates, sandstones, siltstones, mudstones and coals. Primary structures, geophysical well logs, lithology of cores, thin sections and SEM samples were examined, and grain size analyses were done on friable samples to determine the environment of deposition. / Ripple mark crest orientations suggest that the shoreline was oriented northeast-southwest when the sandstone members and conglomerates were deposited. Steep-side modes of asymmetric ripple marks and primary modes of crossbedding indicate sediment transport was toward the northwest, which was probably toward deeper water at the time of deposition. / The presence of possible tidal channels, mica flakes, high angle crossbedding, herringbone crossbedding, organic matter in the troughs of the ripple marks and isolated current type ripple marks suggest that the Pottsville sediments were deposited in an environment influenced by tides. / Fetch calculations reveal that the water body in which the ripple marks formed ranged from 37 km. to 700 km. in width. The ripples induced in the latter might have formed during a storm in an ocean smaller than 700 km. width. Ripple indices suggest that water depth varied from 31 cm. to 100 cm., wave length from 3 m. to 9 m. and wave height from 8 cm. to 28 cm. These are shallow water and modest fetch values which can be met on a broad shallow shelf with well formed waves approaching from offshore. / Scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectrum (EDX) and thin section analysis show that authigenic quartz, illite and kaolinite make up the cement. These analyses also suggest that the Pottsville sandstones have undergone local decementation processes. / Source: Dissertation Abstracts International, Volume: 50-08, Section: B, page: 3359. / Major Professor: William F. Tanner. / Thesis (Ph.D.)--The Florida State University, 1989.
42

Diagenetic history of Entrada and Dakota formations in Ghost Ranch area, New Mexico

Unknown Date (has links)
The Jurassic Entrada Formation in Ghost Ranch area is eolian in origin. It is composed of quartz with minor amounts of feldspar and rock fragments. Observed cements are smectite as grain coatings, and calcite and kaolinite as pore fillings. Smectite and calcite were formed during very early to early diagenesis, whereas kaolinite formed during late diagenesis. Dust storms played an important role in the diagenesis of the Entrada Formation as a source of cements and as a controlling factor in diagenetic processes. The Entrada Formation is highly porous. These pores show many characteristics of secondary origin. Calcite and feldspar dissolution resulted in kaolinite formation. / The Cretaceous Dakota Formation has three units. The fluvial lower unit was cemented with kaolinite and silica. The middle unit was deposited in a transitional environment and was cemented with silica and calcite. The marine upper unit is cemented with silica and kaolinite. Sources of cements in Dakota Formation have been interpreted as being water of shale compaction and ground water for silica; shells and calcareous particles for calcite; and feldspar and other alumino-silicate grains for kaolinite. / Entrada and Dakota sandstones have several similar characteristics. Both have similar mineralogical composition and grain size, are tectonically undisturbed, and have not been deeply buried. However, even though the Dakota Formation is stratigraphically above the Entrada Formation, it is much more coherent than the latter. / The friable nature of the Entrada Formation is believed to be the result of very early cementation. Early smectite coatings prevented potentially available silica cementation, which would have produced a more durable sandstone. Early calcite cementation kept the formation from being extensively compacted. Early calcite cement and feldspar grains were dissolved, in part, later, resulting in a highly porous (secondary) and friable sandstone. / Well developed quartz overgrowths, generally interlocked, made the Dakota sandstones relatively coherent. / Cementation patterns are not formation-boundary dependent. Lower Morrison sandstones have the Entrada cementation pattern, whereas Upper Morrison sandstones are more like the Dakota. / Source: Dissertation Abstracts International, Volume: 50-05, Section: B, page: 1817. / Major Professor: William F. Tanner. / Thesis (Ph.D.)--The Florida State University, 1989.
43

GEOLOGY AND GEOCHEMISTRY OF THE SEDIMENTARY PHOSPHATE DEPOSITS OF NORTHERN PENINSULAR FLORIDA

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 32-12, Section: B, page: 7120. / Thesis (Ph.D.)--The Florida State University, 1971.
44

GEOLOGICAL SIGNIFICANCE OF THE POLYCHAETOUS ANNELID FAMILY SABELLARIIDAE

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 36-01, Section: B, page: 0134. / Thesis (Ph.D.)--The Florida State University, 1974.
45

THE MAURICE EWING BANK OF THE MALVINAS (FALKLAND) PLATEAU: DEPOSITIONAL AND EROSIONAL HISTORY AND ITS PALEOENVIRONMENTAL IMPLICATIONS

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 39-06, Section: B, page: 2708. / Thesis (Ph.D.)--The Florida State University, 1978.
46

Neogene stratigraphy and geologic history, Apalachicola Embayment, Florida

Unknown Date (has links)
Neogene units lie near the surface in the Florida Panhandle in a narrow band extending from twenty miles west of Tallahassee, Leon County, northwest to Oak Grove in north-central Okaloosa County. Downdip towards the Gulf of Mexico these units thicken and change in lithologic character. These contemporaneous lithologic packages, although subsurface, can be defined and mapped throughout the region using stratigraphic core tests, water well cuttings, and geophysical well logs. The Bruce Creek Limestone and Intracoastal Formation are two, predominantly subsurface, units mapped from this area. The Chipola and Jackson Bluff formations are younger downdip in the subsurface than where they are exposed updip. Pleistocene quartz sands and gravels, and massive silty clay beds are mapped in Gulf, Franklin, and southern Liberty counties. These units were deposited in brackish and fluvial environments as the Apalachicola delta system advanced south. / The Neogene and Pleistocene sequence of sediments thickens and dips around a gently plunging axis that decends gulfward through central Gulf County. This thickened sequence of sediments is called the Apalachicola Embayment. / The Apalachicola Embayment resulted from a graben in Triassic to Early Jurassic times. This graben slowly filled with sediments until it ceased to exist as an embayment at the end of the Early Cretaceous. From Early Cretaceous through Early Eocene a "low" or depression occurred eastward of the Jurassic axis. During Early through Late Eocene the axis of the "low" shifted northwest until, during the Oligocene, it was repositioned once again over the Jurassic axis. This Late Cretaceous-Tertiary feature is considered to be due to slow deposition in a current swept strait similiar to the present Florida straits. During the Early Miocene-Middle Miocene the strait apparently began to fill in as carbonates from the Florida platform on the southeast infringed into the shallow current, and clastics from the northwest spilled over onto the shallow shelf. During the Late Miocene to Pleistocene the strait completely filled in and the prograding coastal plain migrated over the area. The feature is not extant now because the Apalachicola River and its delta have prograded over the feature. / Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0674. / Major Professor: Ramil C. Wright. / Thesis (Ph.D.)--The Florida State University, 1983.
47

Mesozoic diabase dikes of North Carolina

Unknown Date (has links)
Mesozoic diabase (dolerite) dikes and sills occur throughout the circum-Atlantic margin. This study investigates those dikes occurring in North Carolina (USA). Approximately half of the study area is typified by north-trending quartz-normative tholeiitic dikes. The remaining areas, or "domains" are dominated by northwest-trending olivine diabase. The olivine diabase is resolved into four distinct varieties based on petrography, trace elements and abundances of silica, iron, alumina, and calcium. / High FeO olivine (HFO) diabase has greater than 10.59 percent FeO* and consists of at least three subgroups that arose from a common HFO parental melt. One subgroup (FeHFO diabase) has FeO* abundances of more than 12 percent, is a likely parent for alkaline olivine diabase, and resulted from extraction of orthopyroxene, clinopyroxene, (and plagioclase?). / Most HFO analyses do not exceed 12 percent FeO* and may be resolved into two distinct petrogenetic groups--one is dominantly primary, the other is dominantly sub-primary. Though ternary extraction (olivine, clinopyroxene, spinel) cannot be ruled out, primary HFO, most likely represents olivine extraction and orthopyroxene assimilation (i.e. incongruent melting). Sub-primary HFO diabase represents clinopyroxene, olivine and spinel extraction. Crustal fractionation of sub-primary HFO yielded the (north-trending) high FeO* quartz diabase (HFQ). The fourth olivine diabase group is uniformly low in FeO* (less than 10.15 weight percent) and exhibits continuous variation from primary tholeiitic to sub-primary calc-alkaline (high-alumina) compositions. This low FeO olivine (LFO) diabase resulted from slightly smaller amounts of mantle melting than HFO magma (17.5 vs. 20 percent, respectively). / The apparent discrepancy between mantle settings of fractionation and the absence of high pressure phases (e.g. orthopyroxene) in the phenocryst assemblage is due to the premise of isobaric fractionation. The mechanism of fractionation proposed for all olivine diabase (except the FeHFO group) is incremental polybaric fractionation (IPF). This variation of polybaric fractionation incorporates the compressibility of basaltic magmas and relates the original idea (developed on a premise of ascending diapirs within ductilely deformable aesthenosphere) to transport and fractionation of magmas through lithospheric regimes of brittle deformation. / Source: Dissertation Abstracts International, Volume: 49-06, Section: B, page: 2095. / Major Professor: Paul C. Ragland. / Thesis (Ph.D.)--The Florida State University, 1988.
48

Structural Evolution of Ad Damm Shear Zone, Western Saudi Arabian Margin and Its Relation to Red Sea Rift System

Unknown Date (has links)
This project seeks to determine how the opening of the Red Sea rift was influenced by pre-existing tectonic features and to place constraints on the structural evolution of the western Saudi Arabia margin. In detail, we investigate whether or not the Ad Damm Shear Zone (ADSZ) was solely a Neoproterozoic structure or if it has been reactivated during the Cenozoic. The Ad Damm shear zone is a major mylonitic right-lateral structure that bounds the Jeddah terrane to the north from the Asir terrane to the south. South of the ADSZ, the Red Sea rift exhibits well-developed linear magnetic anomalies, but north of it, they are not present. On land, the ADSZ bounds a large topographic escarpment perpendicular to the rift margin, with higher elevations to the south. In addition, recent studies show active seismicity within the Jeddah terrane bounded by the ADSZ. These observations collectively suggest some type of tectonic reactivation. Four techniques were used to test this hypothesis: field mapping, satellite image processing (ASTER, SPOT-5), microstructural studies, and whole rock geochemistry. Field observations show various meta-plutonic and volcanic rocks that range in age from 800-540 Ma. North of the ADSZ, Jeddah terrane is characterized by heterogeneous magmatism with extensive meta-basalt intruded by silicic plutons of varying size. South of the ADSZ, Asir terrane is characterized by larger-scale granitic batholiths. In addition, a large synform, likely a km-scale drag fold, is present along the northern edge of the ADSZ. Felsic dikes intrude a package of metabasalt and are folded in the synform. A younger generation of Eocene to Miocene basaltic dikes cut the mylonitic shear zone at a high angle. Petrographic analyses of mylonitic rocks indicate dynamic recrystallization and grain size reduction suggesting high-temperature recrystallization. Field observations also found a lack of low temperature fault zone rocks (e.g. gouge) except for isolated brittle slickensides. Spider diagram of Jeddah, Asir terranes, and ADSZ rocks are characterized by arc-related signature, which related to the amalgamation of Jeddah and asir terranes and defined ADSZ as Neoproterozoic structure. In contrast, Eocen-Miocene Basaltic dikes and southern basaltic flow are represented by rift-related signature, which is associated with development of Red Sea rift system. However, differences in the crustal characteristics of Asir and Jeddah terranes still influence the ongoing tectonic evolution of the Red Sea rift. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the in partial fulfillment of the Master of Science. / Fall Semester 2015. / November 12, 2015. / Ad Damm Shear Zone, Neotectonics, Red Sea, Rift System / Includes bibliographical references. / David W. Farris, Professor Directing Thesis; James F. Tull, Committee Member; Leroy A. Odom, Committee Member.
49

Channel Morphology, Streamflow Patterns, and Sediment Transport of Two Intermittent Rivers along the Balcones Escarpment

Dorn, Taylor C. 11 April 2019 (has links)
<p>Despite a recent increase in intermittent river research focusing on the mechanisms driving flow intermittence and the role they play in the biological community, first order controls, such as the geology, land cover, and climate of the watershed, are not well understood. The rise of intermittent river research coincides with them becoming increasingly more prevalent on Earth due to climate change and water abstraction. While these problems are observed more clearly in arid regions, little research is focused in areas with greater rainfall amounts, such as in central Texas, where there are currently no known studies focusing on intermittent rivers. Here, we collected data over the course of nine months (April 2017 ? January 2018) within Schulle Canyon and Spring Lake Preserve, to determine how their morphology changed over time, their capacity to transport sediment, and the drivers of their intermittency. To answer these questions, three methods were used: 1. Ten cross-sectional surveying points were taken in each river to show how each river?s morphology changes over time, 2. Passive Integrated Transponders were inserted into 60 grains varying in size to track, via GPS, how far those grains traveled after a rainfall event, and 3. 30 Stream, Temperature, Intermittency, and Conductivity sensors were longitudinally deployed down each river to determine where and when water is present. From these collected field data, we found that Schulle Canyon?s morphology did not change over nine months, while Spring Lake saw a change in five of its cross sections, most notably cross sections 6, 9, and 10. Water levels were estimated to depths of 30 cm mostly between August 26 - 28, 2017, which coincided with Hurricane Harvey. In each intermittent river, little to no sediment transport was recorded, with all grain sizes staying within 12 m of their starting point. This study provides much-needed data on sediment transport in intermittent rivers.
50

Mechanical Analysis of a Detachment Shear Zone, Picacho Mountains Metamorphic Core Complex (AZ)

Yun, Samuel 11 April 2019 (has links)
<p>On I-10 between Tuscon, AZ, and Phoenix, AZ, is the Picacho Mountains Metamorphic Core Complex (MCC). The Picacho Mountains MCC represents the northwest of the Greater Catalina MCC which includes Tortolita, Santa Catalina, and Rincon Mountains. To the immediate south of I-10 is Picacho Peak, an early Miocene andesitic volcanic center, and opposite of Picacho Peak are the granitic Picacho Mountains. The detachment shear zone (DSZ) is well exposed at Hill 2437. The mylonitic DSZ is separated into an upper, middle, and lower plate by two detachment faults. The DSZ is estimated to have undergone deformation at ~500?C based on recrystallized quartz microstructures and a previous thermochronologic study by previous graduate student Maxwell Schaper. We obtained an average flow stress of 43 ? 9 MPa using a quartz paleopiezometer by Stipp and Tullis (2003). Using a flow law by Hirth et al. (2001), we found strain rate values between 10-13 and 10-12 s-1. Grain size analysis indicates that quartz recrystallized grains have relatively moderate aspect ratio (1.55 < Rf < 1.87) which correlates to small amount of finite strain (1.13 < Rs < 1.33). Results from vorticity analysis based on the recrystallized quartz grain shape foliation method reveals that quartz was deformed under ~60% pure shear and ~40% simple shear (0.48 < Wm < 0.70, assuming plane strain), and the DSZ experienced ~18% of shortening perpendicular to mylonitic foliation, and up to ~22% of stretching parallel to the flow plane up. We found that despite high strain rate values and evidence of high strain rate (e.g. undulose extinction in quartz, chessboard structures, cataclasites, and possible pseudotachylytes), this is not reflected in the amount of finite strain recorded by the mylonitic DSZ.

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