نتایج جستجو برای: trace fossil
تعداد نتایج: 91986 فیلتر نتایج به سال:
Judgemental positions are presented on research priorities in regard to the health effects from stationary sources of fossil fuel combustion products. Hopefully, they can provide guidance for efforts to ensure that national energy needs are met with minimum environmental and economic burdens on the public. The major areas include epidemiological studies, controlled biological studies, mutagenes...
The vast majority of the world's fossil fuel trace gas emission sources can be detected and mapped using nighttime low light imaging data from the U.S. Air Force Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). This includes human settlements, industrial and commercial facilities, and gas flares. Nocturnal lighting could be regarded as one of the defining featu...
Asymmetry is a fundamental aspect of the biology of all organisms, and has a deep evolutionary history. The fossil record contains evidence of both morphological and behavioural asymmetries. Morphological asymmetry is most commonly expressed as conspicuous, directional asymmetry (either lateral asymmetry or spiral asymmetry) in body fossils. Few examples of fluctuating asymmetry, a form of subt...
Insects were the first animals to evolve powered flight and did so perhaps 90 million years before the first flight among vertebrates. However, the earliest fossil record of flying insect lineages (Pterygota) is poor, with scant indirect evidence from the Devonian and a nearly complete dearth of material from the Early Carboniferous. By the Late Carboniferous a diversity of flying lineages is k...
The Kashkan Formation (Paleocene to Middle Eocene), consists of conglomerate, sandstone, and siltstone in the Zagros Folded zone, southwest Iran. Type of the sedimentary facies, architectural elements and trace fossils show that Kashkan deposits were formed in a low sinuosity braided stream system, with north to south flow direction. The formation displays coarsening-upward succession reflects ...
The up to 304 m thick, turbiditic, siliciclastic Ashin Formation (Upper Ladinian to Lower Carnian?) crops out widely in the Nakhlak area of central Iran. The rocks consist mainly of turbiditic volcaniclastic sandstones and shales that were deposited in distal parts of submarine fans of the continental slope to abyssal plain. Trace fossils occur commonly in the lower parts of the turbiditic volc...
Trace element analysis of fossil bone and enamel constitutes a useful tool to characterize the paleoecological behavior of mammals. Up to now, most trace element studies have focused on Plio-Pleistocene fossils. Here, we show that paleodietary inferences based on trace element analyses can be also obtained from ~14Ma old Miocene mammals, in a period of time when important paleoclimatic changes ...
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