• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1192
  • 254
  • 46
  • 46
  • 46
  • 46
  • 46
  • 46
  • 42
  • 34
  • 27
  • 15
  • 14
  • 14
  • 14
  • Tagged with
  • 1746
  • 1746
  • 178
  • 136
  • 134
  • 128
  • 121
  • 118
  • 107
  • 99
  • 98
  • 96
  • 93
  • 88
  • 88
  • 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.
111

The stratigraphy of northwestern Adams and northeastern Brown Counties, Ohio /

Kaufmann, Robert Frank, January 1964 (has links)
Thesis (M.S.)--Ohio State University, 1964. / Includes bibliographical references. Available online via OhioLINK's ETD Center
112

Sequence stratigraphy and lithofacies of the middle Eocene upper McIntosh and Cowlitz Formations, geology of the Grays River Volcanics, Castle Rock - Germany Creek area, southwest Washington /

Kleibacker, Derik W. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2002. / Includes maps in pocket. Typescript (photocopy). Includes bibliographical references (leaves 197-203). Also available via the World Wide Web.
113

Tectonic evolution of Dazhuqu and Bainang terranes, Yarlung Zangbo suture, Tibet as constrained by radiolarian biostratigraphy /

Ziabrev, Sergey. January 2002 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2002. / Map in pocket. Includes bibliographical references (leaves 306-329).
114

Late quaternary sedimentation in the Eastern Angola Basin /

Bornhold, Brian D. January 1973 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 1973. / Includes bibliographical references (p. 156-164).
115

Basement rocks in adjoining parts of Oklahoma, Kansas, Missouri, and Arkansas

Denison, Rodger E. 24 June 2011 (has links)
Samples from more than two hundred and twenty wells penetrating basement rock have been examined and described from a 61,000 square mile area in adjoining parts of Oklahoma, Kansas, Missouri, and Arkansas. Twenty-five isotopic age determinations were made on twenty samples of basement rock from wells and outcrop areas. Nine basement rock units can be defined within the study area on the basis of petrography and isotopic age. 1. "Older granite and gneiss" is a loose association of granitic rocks considered to be older than 1400 million years. The unit cannot be precisely defined within the study area. 2. The Lyon County Quartzite is a micaceous quartzite restricted to relatively small areas in the buried basement of Kansas. The age of deposition is unknown but preceded the 1400 million year age of metamorphism. 3. The Chase County Granite Group is composed largely of granite and gneissic granite. Rocks of this group underlie most of the Nemaha Uplift in Kansas and also occur considerably east and west of the Uplift. The rocks were intruded at about 1400 million years, probably as a composite batholith. At about 1200 million years, four petrographically related rock units were intruded or extruded. The age difference between these units cannot be distinguished by isotopic ages. The four units are assembled into the Northeast Oklahoma Province, a petrographic grouping of volcanic rocks and chemically equivalent hypersolvus type epizone granites. 4. The Washington County Volcanic Group is composed mostly of rhyolite but also contains andesite and metarhyolite. The majority of the rhyolites were probably extruded as welded tuffs. 5. The Spavinaw Granite Group is composed of generally micrographic granite porphyries. The intrusions are considered to be largely sills on textural evidence and by analogy with outcrop areas elsewhere. 6. The Woodson County Granite is texturally variable. Samples from drill holes in Kansas are petrographically identical to boulders found at Rose Dome in Woodson County, Kansas. 7. The Osage County Microgranite is the most uniform unit in the area. The microgranite occurs in a roughly circular area in Osage County, Oklahoma. The unit was probably intruded as a sill within rhyolite flows. Two other petrographic units are interpreted as being younger than parts of the Northeast Oklahoma Province, although in the same 1200 million years isotopic age range. 8. The Vernon County Metamorphic Group is composed mostly of low rank metamorphic rocks derived from clastic sediments. The grade of metamorphism is from incipient to middle greenschist facies. Rhyolite detritus occurs in some samples. 9. The Central Oklahoma Granite Group is composed of two feldspar mesozone type granites. The unit is not distinguishable from the Chase County Granite Group on the basis of petrography. Uplift and erosion followed the intrusion of the Central Oklahoma Granite Group. The main uplifts were along the present Nemaha Uplift and along a northeast-southwest axis from southwest Missouri to central Oklahoma. There is no evidence for any igneous or metamorphic activity between 1200 million years and the deposition of lower Paleozoic sediments. / text
116

Delineating geostratigraphy by cluster analysis of piezocone data

Hegazy, Yasser Ali 08 1900 (has links)
No description available.
117

Chemostratigraphy of Middle Devonian lacustrine sediments in the Orcadian Basin, north-east Scotland

Craigie, Neil William January 1998 (has links)
During Middle Devonian times, lacustrine deposition dominated much of NE Scotland including Caithness, Orkney, Shetland and the Inner Moray Firth. Donovan classified such deposits into five distinct facies associations:- the deep water facies association A and the progressively shallower water facies associations B, C, D and sandstones. Such facies associations occur in climatically induced cycles. Facies A sediments (known as "fish beds") are organic rich, comprising triplets of carbonate, clastic and organic laminae (each triplet is c. 1.5mm thick). In the present study the fish beds have been categorised on sedimentological grounds into four subtypes:- types I, II (a and b subtypes), III and IV fish beds. The former, which were deposited under the most reducing, deep water, quiescent conditions, comprise 1.3m+ thick laterally continuous beds containing abundant and well preserved, fully articulated fossil fish. Type II(a), and II(b) and III fish beds are less than 1.3 thick and deposited under increasingly more shallow water and more oxidising conditions. Type II(a) fish beds contain both articulated and dissarticulated fish carcass material while type II(b) fish beds, of similar thickness, contain scattered fish fragments. Type III fish beds occur in close vertical and lateral proximity to fluvial sandstones. Type IV fish beds are carbonate rich and are confined to the south Moray Firth coast. Type I fish beds have the greater source rock potential. It is possible to categorise the Middle Devonian facies, including the fish bed facies, on geochemical grounds. As far as major element geochemistry is concerned, SiO<sub>2</sub> is concentrated principally in detrital quartz, and for this reason is highest within sandstones, while K<sub>2</sub>O, Al<sub>2</sub>O<sub>3</sub> and Fe<sub>2</sub>O<sub>3</sub> are highest within the clay rich facies C and D. MnO is most concentrated within facies AIII and B, deposited closest to the thermocline. Trace elements were also analysed and are also useful in discriminating facies. Some elements, such as Zr and Nb are highly immobile, being concentrated in the dereital fraction of sandstones. By contrast, Rb, Ba and V are principally concentrated within clay and feldspars and, for this reason, are highly concentrated within the most clay rich deposits (facies D). The distributions of Mo, Cu, Ni, V and Cr are partly controlled by paleoredox and, consequently, may be used to discriminate relatively reducing from oxidising facies. U and Th are most highly concentrated within fish bone/scale material and it is possible to use the U/Th ratio to categorise the fish beds. This ratio is highest within the most reducing fish beds (type I) and in fish beds located close to fluvial sandstones (type III). Type II and IV fish beds have generally lower U/Th ratios. This ratio may be measured where spectral gamma ray logs have been run (e.g. Dounreay boreholes).
118

Stratigraphy, sedimentation and oil potential of the Lower Jurassic to Kimmeridgian of the United Arab Emirates : outcrop and subsurface compared

Matos, José Esteves de January 1997 (has links)
The Jurassic litho-biostratigraphy is reviewed and Jurassic depositional models are defined in order to clarify some regional stratigraphic uncertainties and to evaluate the hydrocarbon potential of the Jurassic of the United Arab Emirates (UAE). A thick succession of Triassic-Cretaceous shallow-marine carbonates is exposed in Wadi Naqab, southeast of Ras Al Khaimah in the UAE, Musandam Peninsula. The Jurassic, 1310 m thick, is examined using biostratigraphy, sedimentology and sequence stratigraphy and compared with the Abu Dhabi subsurface. Direct composition of the Jurassic foraminiferal biozones and algal assemblages can be made between Wadi Naqab and the South-Tethyan realm. Palynological data from the subsurface demonstrate that much of the Liassic, which is well represented in the Musandam Peninsula, is missing over most of the Emirates. A ca. 50 Ma time gap was defined within the Abu Dhabi clastic Minjur Formation (previously assigned to the Triassic). The age of the palynoflora of the upper Minjur is Bajocian, while the lower Minjur yielded Late Carnian palynomorphs. The Upper Toarcian and most of the Aalenian is also probably missing in the Musandam Peninsula, as in the subsurface of the Emirates and Saudi Arabia. A new Bajocian foraminifera <I>Pseudodictyopsella jurassica</I>, n. gen., n. sp., was recognised, and the inception of some stromatoporoids was earlier than previously thought. The Liassic of Wadi Naqab is dominantly a metre-scale 5<sup>th</sup>-order Milankovitch-driven succession composed of peritidal cycles. Cycle tops are commonly marked by corrosion zones and/or karsts. Stacked paleokarsts are found particularly in the Sinemurian and Lower Pliensbachian. In Wadi Naqab, the Middle and Upper Jurassic seem to comprise one shallowing-upward 3<sup>rd</sup>-order cycle built of abundant 5<sup>th</sup>-order cycles. As a result of comparisons in this study, the Bajocian Izhara Formation is redefined and a new type-section proposed. Most of the Kimmeridgian and Tithonian are absent in Wadi Naqab, and eastern onshore and offshore Abu Dhabi, as the result of uplift and erosion before deposition of the Lower Cretaceous. Possible major Jurassic (Liassic-Early Kimmeridgian) hydrocarbon plays of Abu Dhabi are: the Marrat lowstand wedge of eastern onshore, the Jurassic onlap of Triassic high blocks in offshore areas, the Minjur lowstand clastics, the offshore Uweinat and Upper Araej and the Upper Jurassic Hadriya and Hanifa reservoirs.
119

Stromatolites and the biostratigraphy of the Australian Precambrian, with appendices on pseudo fossils from Australian Precambrian iron-formation and greywacke

Walter, Malcolm Ross January 1970 (has links)
2 v. : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Mineralogy, 1971
120

The biostratigraphy and palaeoecology of South Australian Precambrian stromatolites

Preiss, Wolfgang Victor January 1971 (has links)
Precambrian stromatolites in South Australia are almost entirely restricted to the folded rock sequence of the Adelaide Geosyncline, a large, deeply subsiding basin with predominantly shallow - water sediments. The history of research into the age and fossils of the Precambrian rocks is reviewed, and a possible time - framework is suggested on the basis of available radiometric data. Stromatolites, laminated structures formed by trapping of detritus and precipitation of chemical sediment by algae and bacteria, have been studied by other workers from at least two points of views : most Western authors regard stromatolite morphology to be purely environmentally determined, while one Russian school maintains that it is largely controlled by the algae present, and that stromatolites evolve as a consequence of the evolution of the algae forming them. They concluded this from an empirical study of widespread stromatolites of different ages, which made possible the biostratigraphic subdivision and correlation of many Late Precambrian sections. The Russian methods of study and taxonomy have now been applied to South Australian stromatolites for the first time. Of the eighteen forms of columnar stromatolites described, five are identical or nearly identical to Russian forms. Nine forms are new, but sufficiently similar to Russia forms to allow inclusion in the same groups as these. Groups and forms must be defined on the basis of numerous characters, which may be given different relative weighting for different taxa. The taxa so defined have restricted ranges in geological time. Stromatolite correlation with the Russian sequence suggests that the Early Adelaidean ( i.e. pre - tillite ) beds are middle Riphean ; the Skillogalee Dolomite is youngest middle Riphean, i.e. older than the Late Riphean Bitter Springs Formation of Central Australia. The Late Adelaidean Umberatana Group assemblage, correlated with the youngest Late Riphean, has seven groups in common with the Bitter Springs Formation, but unlike the latter, it overlies the lower tillite. A comparison with available radiometric data shouts good agreement for the Umberatana Group, but some conflict with one recent age determination exists for the Early Adelaidean. A study of the environments of growth of South Australian stromatolites shows that at least three forms, of widespread distribution, grew under a variety of conditions of energy, oxidation, type of sediment influx, and possibly salinity. The taxa defined are stable under these varying conditions, but there are minor modifications due to differences in environmental energy. Skillogalee Dolomite stromatolites grew under varying energy conditions on a very extensive and level carbonate depositing platform, frequently under hypersaline conditions. Umberatana Group stromatolites inhabited a marine environment, either in marginal littoral zones in the south - western and north - eastern Flinders Ranges, or on off - shore carbonate banks interpreted to be related to rising diapirs. In both cases, stromatolites formed during episodes of shallowing water depth. / Thesis (Ph.D.)--Department of Geology and Mineralogy, 1971.

Page generated in 0.0808 seconds