نتایج جستجو برای: microfossil
تعداد نتایج: 309 فیلتر نتایج به سال:
Abstract. River erosion affects the carbon cycle and thus climate by exporting terrigenous to seafloor sediment nourishing CO2-consuming marine life. The Yukon River–Bering Sea system preserves rare source-to-sink records of these processes across profound changes in global during past 5 million years (Ma). Here, we expand terrestrial record dating terraces along Charley River, Alaska, explore ...
Ž 9 . Microfossil finds have been firmly established at about 3.5 Ga giga annees10 years , but no rocks older than about 4.0 Ga have been demonstrated, leaving the history of the first 0.6 Ga missing. This gap has been filled by models of the solar system. The origin of the ocean, atmosphere, and much crustal material apparently lies in a heavy rain of comets, subsequent to the catastrophic Moo...
New megafossil and microfossil data indicate four episodes in the diversification of Silurian-Early Carboniferous land plants of South China, a relatively continuous regional record. Plant diversity increased throughout, but the rising curve was punctuated by three major falls. There were peaks of origination in the Ludlow-Pragian, Givetian, late Famennian and Visean and peaks of extinction in ...
Paleoenvironmental records from a southern California coastal saltmarsh reveal evidence for repeated late Holocene coseismic subsidence events. Field analysis of sediment gouge cores established discrete lithostratigraphic units extend across the wetland. Detailed sediment analyses reveal abrupt changes in lithology, percent total organic matter, grain size, and magnetic susceptibility. Microfo...
Knowing the geographic extents of species is crucial for understanding the causes of diversity distributions and modes of speciation and extinction. Species geographic ranges are often viewed as approximately constant in size in geological time, even though climate change studies have shown that historical and modern species geographic distributions are not static. Here, we use an extensive glo...
the present article is a review of a palaeobiogeographic analysis of jurassic ostracods from east africa, india and madagascar and includes also some general remarks on palaeobiogeography, biodiversity and ostracod ecology.the palaeobiogeographic study shows the high significance of this microfossil group for the reconstruction of palaeogeographic processes, particularly plate tectonic developm...
Sedimentology of the of Zayandeh-Rood River alluvial Terraces and the sediment source identification
In this research, three alluvial Terraces that are located in pathway of Zayandeh-Rood River are studied. The river starts from Bakhtiayri Zardkoh mountain and after through Esfahan city ends to Gawkhony lake. Age of alluvial terraces is younger in upstream than downstream and the height level of the terraces decrease relative to current river bed toward the downstream. The terraces were sample...
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Calcareous nanoplankton are one of the most abundant calcite unicellular planktonic organisms on the Earth. This group include coccoliths which are formed from calcite crystals. They are one of the most important microfossil groups in biostratigraphic, paleontologyl and oil exploration stu...
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