نتایج جستجو برای: holocene
تعداد نتایج: 8437 فیلتر نتایج به سال:
Radiocarbon ages of vascular plant wax-derived n-alkanes preserved in well-dated Holocene sediments in an anoxic fjord (Saanich Inlet, Canada) were found to be not only substantially older than the depositional age but increasingly so during the Holocene. Assuming that n-alkanes serve as a proxy for recalcitrant terrigenous organic matter, this indicates that the accumulation of refractory orga...
We present new Holocene and glacial dO data measured on planktonic foraminifera Neogloboquadrina pachyderma and benthic foraminifera Cibicidoides species from the Atlantic and Pacific sectors of the Southern Ocean in order to better understand its glacial hydrography. Combined with previously published data, the latitudinal dO distributions of these foraminifera show no appreciable difference d...
1. introduction the zagros mountains present a great potential for paleo-environmental studies for the reconstruction climates of the late-pleistocene and holocene. iranian zagros mountains form the northeastern boundary of the fertile crescent and separating the mesopotamian lowlands from the iranian plateau. it is postulated that near east was a place for the domestication of plants and anima...
We summarize information concerning Recent and Pleistocene-Holocene Uruguayan sand dollars (Mellitidae), as well as Miocene taxa (Monophorasteridae). Recent and Pleistocene-Holocene species (Encope emarginata, Mellita quinquiesperforata, and Leodia sexisperforata) are at their southernmost limits of distribution, with only E. emarginata recorded further south than Uruguay. Lower temperatures to...
High-resolution analyses of lake sediment from southwestern Alaska reveal cyclic variations in climate and ecosystems during the Holocene. These variations occurred with periodicities similar to those of solar activity and appear to be coherent with time series of the cosmogenic nuclides 14C and 10Be as well as North Atlantic drift ice. Our results imply that small variations in solar irradianc...
Abstract Sediments provide a continuous, sensitive record of changing conditions of environment and processes within plain and in the surrounding plain, thus they contain significant archives of past environmental change on the continents. Valuable informations on regional and global scale patterns of past climate variability in the Azarbayjan region have been documented by numerous paleocli...
■ Abstract Although human-induced changes to the global environment and natural biotic resources, collectively labeled “global change” and the “biodiversity crisis,” have accelerated with industrialization over the past 300 years, such changes have a much longer history. Particularly since the rise of agriculturally based societies and associated population expansion during the early Holocene, ...
In the Weichselian, the Lower Rhine in the Dutch-German border region has used three courses, dissecting ice-marginal topography inherited from the Saalian. In the Late Weichselian, the three courses functioned simultaneously, with the central one gaining importance and the outer ones abandoning. This study aims to reconstruct the fluvial development and forcings that culminated in abandonment ...
Woolly mammoths inhabited Eurasia and North America from late Middle Pleistocene (300 ky BP [300,000 years before present]), surviving through different climatic cycles until they vanished in the Holocene (3.6 ky BP). The debate about why the Late Quaternary extinctions occurred has centred upon environmental and human-induced effects, or a combination of both. However, testing these two hypoth...
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