Browsing by Subject "Stratigraphic -- Silurian"
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Item A Study of the Silurian System and a Silurian Reef in West Texas and Southern New Mexico(Texas Tech University, 1971-05) Cronin, Thomas C.Not Available.Item Integrated stratigraphy and petrology of the Silurian Wink formation (Wenlock-Ludlow) Howard County, Texas(Texas Tech University, 2004-05) Kohl, Michael LThe Cobra-Frazier #1 well in Howard County penetrated the Silurian Wristen Group and Fusselman Formation, and a core with sixty feet of strata was recovered, the majority of which belongs to the Wink Formation of the Wristen Group. Petrologic, petrographic, and geochemical studies allow interpretation of the depositional and diagenetic history of the Wink Formation in the eastern margin of the Permian Basin region. The Wink of the Cobra-Frazier #1 consists of argillaceous skeletal wackestones and mudstones that are dominated by a deep water fauna dominated by arthropods. Conodont faunas indicate that the age of the Wink ranges from the early Sheinwoodian (Wenlock), into the Gorstian (Ludlow) and perhaps as young as the early Ludfordian. The Wink Formation was deposited when the exposed Fusselman platform was flooded in the early Sheinwoodian. Deposition continued in a carbonate ramp setting until differential subsidence produced the platform and basin fades of the Fasken and Frame formations. During the hiatus that separated the Thirtyone Formation from the Woodford Formation, the Wink was karsted, evidenced by the presence of crackle, mosaic, and chaotic breccia fabrics related to paleocave formation and collapse. The karst-related porosity was subsequently filled by fine-grained argillaceous carbonate sediments. After the karsting event, the Wink strata underwent to three dolomitization events, two diagenetic, and one epithermal event related to the Ouachita Orogeny. The two diagenetic dolomitization events did not affect the entire Wink equally, with increased dolomitization in the lower portion of the core. In the lower Wink, this created a dolostone with intercrystalline, vuggy, and fracture porosity. Subsequent precipitation of baroque dolomite, from the epithermal event, and calcite cements destroyed much of the porosity throughout the core. Analysis of carbon and oxygen stable isotopes produced curves that were used to test models of oceanic and environmental cyclicity. When compared to oceanic and environmental models, the data was inconclusive, neither clearly supporting nor refuting any of the models. Two positive excursions associated with the Mulde Event and near the Wenlock-Ludlow Boundary are present in both the carbon and oxygen curves. These excursions have carbon §-values increased by slightly more than l%o, and the oxygen 5-values increases of more than 2%o. The excursions allow correlations between the Wink and strata in Oklahoma, Nevada, and across many parts of Europe, particularly the Baltic region.Item Lithostratigraphy of the subsurface Silurian rocks in western Kentucky(Texas Tech University, 1987-05) Rahman, Ata UrSyndepositional tectonic movements and geometry of the Illinois Basin had a profound influence on thickness, lithofacies distribution and dolomitization in the Silurian rocks in western Kentucky. The northern portion of the Illinois Basin {in Indiana and Illinois) was the site of extensive development of reef trends and numerous isolated reefs with associated petroleum entrapment. However, no reefal trends have been reported from the southern portion of the Illinois Basin in western Kentucky. The Kentucky portion of the Illinois Basin consists predominantly of the Moorman Syncline and its shelves, which are separated from the northern part of the minois Basin by the Rough Creek Fault Zone. Syndepositional Tectonic movements not only controlled the basinal geometry, but also influenced the depositional environments in the Moorman Syncline. The basinal geometry of the Moorman Syncline accounted for a unique geologic setting and a possible reefal trend, altogether different from that of the northern portion of the Illinois Basin. Silurian rocks in the study area consist of more than 600 feet of predominantly clastic-free carbonates with a few thin shaly intervals. Percentages of grainstone/packstone facies and dolomite generally increase toward margins of the basin, whereas percentages of wackestone/packstone facies and calcite increase toward the center of the basin. Syndepositional subsidence of the basinal block, along a segment of the Rough Creek Fault Zone in Grayson County, created a local steep shelf-margin within an otherwise gently sloping carbonate platform. This, in turn, influenced the thickness of the sedimentary-fill, facies distribution and dolomitization pattern. Thickness of the reef-bearing interval (the St. Clair and Moccasin Springs formations) increases locally on the basinal side of the syndepositional fault in Grayson County. Percentages of grainstone/packstone facies and dolomite also increase anomalously in this area. Four different but interdependent criteria: basinal geometry, geometry of sedimentary-fill, lithology and distribution of dolomite support the existence of a probable reef trend in Grayson County. This inferred reef trend in Grayson County is the most promising site for exploration of hydrocarbons entraped within the Silurian reefs or in draped structures in the overlying rocks.Item Stable isotope stratigraphy across the Silurian-Devonian boundary in southern Oklahoma and subsurface west Texas(Texas Tech University, 2004-12) Jacobi., David JosephStable isotopic ( 13C - ä 18O) analysis of carbonates from the Upper Silurian Henryhouse and Lower Devonian Haragan Formations in southern Oklahoma, and the Frame Formation (Upper Silurian-Lower Devonian) in southern Andrews County, Texas was conducted to determine if an excursion in ä 13C coincides with the shift in conodont faunal diversity that characterizes the Klonk event in Southwest Laurentia. Results show a gradual steady increase in ä13C (+ 1.0 %o) across the Henryhouse-Haragan boundary that reaches a peak value (~ + 3.0%o) in the early Lochkovian Icrodiuspostwoschmidti zone. The 5'^C signature of the Frame Formation also shows a steady increase in 5'^C (~ + 3.0 %o) from the late Pridoli that reaches a peak value (~+ 5.0 %o) in the early Lochkovian Icrodius postwoschmidti zone. The ä 13C chemostratigraphic curves do not exhibit an excursion at the level where conodont faunal diversity shifts at the Klonk event in the Henryhouse-Haragan or Frame formations. Intercontinental correlation of the data with other chemostratigraphic studies of Southern Gondwanan successions including the Global Stratotype Section and Point at Klonk in the Czech Republic, reveals no relationship between ä 13C and conodont faunal diversity as proposed by Jeppsson's (1990,1997,1998) model of Silurian Ocean cyclicity.Item Wenlockian (Silurian) agglutinated Foraminifera from the Wayne Formation, Tennessee(Texas Tech University, 1986-08) Zuravel, David LeeNot available