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Showing 1 to 20 of 136 for “"Oligocene"”.
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Paleoceanographic and Paleoclimatic Changes Associated With the Eocene-Oligocene Transition
<p>The Eocene-Oligocene transition (EOT) is one of the largest global paleoclimatic events of the past 50 myr. Surface and deep water temperature histories and variations in global ice volume were reconstructed using paired measurements of δ<super>18</super>O and Mg/Ca on benthic and …
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Late Paleogene (Eocene to Oligocene) paleoceanography of the northern North Atlantic
… occurred in the latest Eocene to earliest Oligocene. In the northern North Atlantic, the widely-distributed reflector R4 correlates with an unconformity that can be traced to its correlative conformity near the top of the Eocene. This horizon reflects a change from weakly circulating …
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Late Paleogene (Eocene to Oligocene) paleoceanography of the northern North Atlantic
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1983.
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Stratigraphy and sedimentary history of middle Cenozoic (Oligocene and Miocene) deposits in North Dakota
<p>Middle Cenozoic (Oligocene and Miocene) continental deposits of North America have been most studied in southwestern South Dakota and western Nebraska where the White River Group constitutes a fairly complete Oligocene record, and the Arikaree Group of early Miocene age is commonly the sole …
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The Occurrence of the Greta Sandstone, Frio Formation (Late Oligocene), Texas Gulf Coastal Plain
… unit of the upper Frio Formation (Oligocene) that occurs across the Texas Gulf Coastal Plain. The Greta sandstone has been known to geologists since it was first drilled in the 1930’s, yet there has been very little research into this un-depleted and overlooked reservoir. This study …
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Origin and Diagenesis of Lacustrine Sediments of the Late Oligocene Creede Formation, Southwestern Colorado
Vertically-zoned sequences of authigenic silicates in tuffs reflect alteration of silicic-intermediate vitric tuff within an elevated geothermal gradient (90$\sp\circ$-150$\sp\circ$C/km). The abundance of clinoptilolite - Al-smectite in drillcore CCM-2 is consistent with diagenetic waters having …
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ANTARCTIC GLACIAL CHRONOLOGY REFLECTED IN THE OLIGOCENE THROUGH PLIOCENE SEDIMENTARY SECTION IN THE ROSS SEA
… of sediments underlying the Ross Sea. The Oligocene through Pliocene portion of this glacial marine section is studied using depositional models derived from the abundant piston core data in the region. The sedimentologic evidence from the Ross Sea glacial section is combined with evidence …
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Characteristics of Tight Reservoirs in the Oligocene Huagang Formation, Xihu Sag, East China Sea Basin
… diagenetic and petrophysical properties of the Oligocene Huagang Formation were studied in terms of the structural belts. The Huagang Formation is characterized by the depositional facies of delta and lacustrine facies. The main rock types are feldspathic litharenite and lithic subarkose with …
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The Oligocene of southern Australia : ecostratigraphy and taxic overturn in neritic foraminifera / Graham David Moss.
This study investigates a late Eocene to Miocene succession of diverse mid-latitude assemblages of foraminifera from carbonates and calcareous muds and sands on the southern Australian margin. It contrasts foraminiferal profiles from the restricted St. Vincent and Murray Basins with the Otway Basin …
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The Titus Canyon Formation : evidence for Early Oligocene extension in the Death Valley Area, CA
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.
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A multi-technique provenance study of the Oligocene : recent Nile cone sediments and River Nile hinterland
… of the modern Nile catchment, together with Oligocene-Recent sediments of the offshore Nile cone, and demonstrates for the first time that the palaeodrainage of the Nile has remained relatively stable over the last 30 Ma. Detrital mineral and bulk-rock analyses of modern river, wadi and …
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Cyclostratigraphy and sequence stratigraphy of the Solent Group (Eocene-Oligocene) of the Isle of Wight, UK
A stratigraphic reinterpretation of the Eocene-Oligocene Solent Group is presented here, based on the Whitecliff Bay section of the Isle of Wight, Hampshire Basin, UK. High resolution palaeontological, sedimentologica and mineralogical analyses allow the establishment of facies groups, which are …
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Petrogenesis of Eocene-Oligocene magmatism of the Sulphur Springs Range, central Nevada: The role of magma mixing
… Au-producing Carlin Trend). Some of the Eocene-Oligocene intrusions and cogenetic volcanic rocks in the range exhibit evidence of magma mixing and invite comparisons with other mineralized, Eocene mixed magma systems like the Bingham porphyry Cu deposit 300 km farther to the east. The Sulphur …
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Stratigraphic Analysis and Reservoir Characterization of the Late Oligocene-Early Miocene, Upper Yenimuhacir Group, Thrace Basin, Turkey
… turbiditic sandstones and reefal limestones, and Oligocene deltaic sandstones are the major reservoir targets in the basin today. The focus of this research is the Upper Oligocene deltaic sandstones, namely the Danismen and Osmancik formations, which contain potential hydrocarbon reservoirs. The …
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Buffalo Canyon: An Oligocene Greisen-Like Intrusion-Related Gold Deposit in the Union Mining District, Nye County, Nevada
… events in the Jurassic, Cretaceous, and Oligocene. Metaluminous, biotite-pyroxene diorite stocks to porphyritic granodiorite dikes have been dated at 162.03 + 0.91 Ma and 158.72 + 0.94 Ma, respectively. Peraluminous, ilmenite-bearing leucogranite plugs and dikes have been dated at 81.96 + …
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The rise of modern mammalian faunas: tempo and mode of faunal turnover in western Montana during the Oligocene
The ongoing biodiversity crisis affects almost one in four mammal species. The main threat affecting them is the loss of their habitat with changes in their environment. Paleontological data allow an exploration of the patterns and processes that regulate such faunal turnovers linked to …
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The effects of mass extinction on escalation of the naticid gastropod predator-prey system at the Eocene-Oligocene
… hypothesis was tested at the Eocene Oligocene extinction boundary in central Mississippi. The levels of escalation of specimens from the Moodys Branch Formation, which lies below the extinction boundary, and the Red Bluff Formation, which lies above the extinction boundary, were …
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Sequence Stratigraphy and Depositional Controls on Oligocene-Miocene Caribbean Carbonate-Dominated Systems, Puerto Rico and the Dominican Republic
… on 87Sr/86Sr-derived mean ages for selected Oligocene-Miocene carbonate and siliciclastic units in Puerto Rico and the Dominican Republic. Results indicate ages of middle-late Oligocene to late Miocene (ca. 29.78–5.88 Ma) and show some significant modifications to previous chronostratigraphic …
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Five new genera and species of Darwin wasps (Hymenoptera: ichneumonidae) from the lower oligocene renova formation of Montana
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-03-28 without embargo terms
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Local variability in early Oligocene paleosols as a result of ancient soil catenary processes, Brule Formation, Toadstool Park, Nebraska
… along a paleovalley sequence in the Early Oligocene Orella Member of the Brule Formation in the White River G
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