نتایج جستجو برای: miocene
تعداد نتایج: 6531 فیلتر نتایج به سال:
At Ocean Drilling Program (ODP) Site 1090 (lat 42 54.8 S, long 8 54.0 E) located in a water depth of 3702 m on the Agulhas Ridge in the sub-Antarctic South Atlantic, 300 m of middle Eocene to middle Miocene sediments were recovered with the advanced piston corer (APC) and the extended core barrel (XCB). U-channel samples from the 70–230 meters composite depth (mcd) interval provide a magnetic p...
The northwestern Gulf of Mexico basin has emerged as an archetype example of a robust, progradational passive margin system that induces substantial translation over underlying detachments due to gravitational loading. Despite this recognition, the difficulties in deep imaging of seismic data have continued to obscure key features of this deformation. Megaregional, 2D, long-offset PSDM data hel...
Freshwater corbulid bivalves found in Miocene deposits of western Amazonia have been considered products of an endemic radiation of a marine clade within the large lacustrine system occupying the region at that time. Our reexamination of Paleocene freshwater corbulids of the Tongue River Formation of western North Dakota and eastern Montana, however, extends the stratigraphic and geographic ran...
The mid-Miocene climatic optimum (MMCO) is an intriguing climatic period due to its above-modern temperatures in mid-to-high latitudes in the presence of closeto-modern CO2 concentrations. We use the recently released Community Earth System Model (CESM1.0) with a slab ocean to simulate this warm period, incorporating recent Miocene CO2 reconstructions of 400 ppm (parts per million). We simulate...
An expansion of C 4 grasslands occurred between 6 and 8 million years ago in the Great Plains of North America, as evidenced by a marked shift to more 13 C-enriched carbon isotope compositions from large fossil mammal tooth enamel and paleosol carbonates. Prior to this expansion, habitats were comprised of exclusively C 3 vegetation. To explore this problem I present a compilation of bulk stabl...
Institute of Animal Genetics, Edinburgh Two symposia on theoretical biology were held in 1966 and 1967 at the instigation of the International Union of Biological Sciences. The meetings were organized by Professor Waddington, and in this article he outlines some of the points discussed at the meetings. The essays arising from the first symposium have recently been published under the title Towa...
Understanding the stability of the early Antarctic ice cap in the geological past is of societal interest because present-day atmospheric CO2 concentrations have reached values comparable to those estimated for the Oligocene and the Early Miocene epochs. Here we analyze a new high-resolution deep-sea oxygen isotope (δ18O) record from the South Atlantic Ocean spanning an interval between 30.1 My...
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