نتایج جستجو برای: lower paleozoic
تعداد نتایج: 693427 فیلتر نتایج به سال:
Analyses of bulk petrographic data indicate that during the Late Paleozoic wildfires were more prevalent than at present. We propose that the development of fire systems through this interval was controlled predominantly by the elevated atmospheric oxygen concentration (p(O2)) that mass balance models predict prevailed. At higher levels of p(O2), increased fire activity would have rendered vege...
Basement rocks in the 17,000-square-mile region of southern Oklahoma crop out in the Wichita and Arbuckle Mountains and have been studied in subsurface samples from 175 wells. The rocks are divided into two contrasting provinces, each completely different from the other in age and petrologic character. Each province has played a different role in guiding the stratigraphic and structural evoluti...
Lower Paleozoic metabasites of south Chah Palang are located in north of the Yazd block in Central Iran with limited distribution and are associated with Doshakh metamorphites. Metabasites divided in to two portions: metavolcanics, and metagabbro, amphibolite and metadiabase masses. Metavolcanic with basaltic composition are presented by foliation and vesicles filled by calcite. Amphibole, plag...
5.14.5 References Planetary Moment of Inertia and the Spin-Axis Apparent Polar Wander (APW) = Plate motion + TPW Different Information in Different Reference Frames Type 0' TPW: Mass Redistribution at Clock to Millenial Timescales, of Inconsistent Sense Type I TPW: Slow/Prolonged TPW Type II TPW: Fast/Multiple/Oscillatory TPW: A Distinct Flavor of Inertial Interchange Hypothesized Rapid or Prol...
It has been argued that increases in predation over geological time should result in increases in defensive adaptations in prey taxa. Recent in situ and laboratory observations indicate that cidaroid sea urchins feed on live stalked crinoids, leaving distinct bite marks on their skeletal elements. Similar bite marks on fossil crinoids from Poland strongly suggest that these animals have been su...
Lower Paleozoic black shales from Estonia, Sweden, and Russia were analyzed for major trace elements to reconstruct the provenance, tectonic setting, paleoweathering conditions of these shales. The shale is highly enriched in U, V, Mo, Pb (except samples Sweden where slightly enriched), SiO2, Fe2O3, K2O, TiO2 depleted CaO, Na2O, MnO, with respect average provenance signatures (Th/Sc versus Zr/S...
Recent geophysical analyses suggest the presence of a late Paleozoic oxygen pulse beginning in the late Devonian and continuing through to the late Carboniferous. During this period, plant terrestrialization and global carbon deposition resulted in a dramatic increase in atmospheric oxygen levels, ultimately yielding concentrations potentially as high as 35% relative to the contemporary value o...
The Central Asian Orogenic Belt, or Altaids, is an amalgamation of volcanic arcs and microcontinent blocks that records a complex late Precambrian–Mesozoic accretionary history. Although microcontinents cored by Precambrian basement are proposed to play an integral role in the accretion process, a lack of isotopic data hampers volume estimates of newly produced arc-derived versus old-cratonic c...
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