نتایج جستجو برای: trace fossils
تعداد نتایج: 80653 فیلتر نتایج به سال:
Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias that most Ediacara fossils are preser...
Well-preserved arthropod trackways are described from the laminated limestones of the Crayssac Lagerstätte (south-west France, Lower Tithonian). They occur in sediments deposited in the temporary coastal mudflats of intertidal to supratidal zones. The trackways are referred to Pterichnus isopodicus isp. nov., and are interpreted as the locomotion traces of isopods. Different trackway morphotype...
Petroleum is a mixture dominantly of hydrocarbons with varying proportions of non-hydrocarbon constituents and traces of organometallic compounds. Generally Petroleum has an average composition of 85% carbon, 13% hydrogen, and 2% of sulphur, nitrogen and oxygen. Organic geochemistry can be defined as the study of the fate and distribution of carbon compounds in contemporary environments, in Rec...
Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrix and structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace element compositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion tech...
Two energy-generating technologies in Britain which transform waste into a resource are compared. One is the (in)famous Combined Heat and Power incinerator in Sheffield, the other a forgotten biological digester in Devon utilizing anaerobic microbes. Both sites are early exemplars of experimental and biopolitical waste disposal technologies—incineration and Anaerobic Digestion—now regarded as l...
We report fossil traces of Osedax, a genus of siboglinid annelids that consume the skeletons of sunken vertebrates on the ocean floor, from early-Late Cretaceous (approx. 100 Myr) plesiosaur and sea turtle bones. Although plesiosaurs went extinct at the end-Cretaceous mass extinction (66 Myr), chelonioids survived the event and diversified, and thus provided sustenance for Osedax in the 20 Myr ...
Fossil feathers, hairs and eyes are regularly preserved as carbonized traces comprised of masses of micrometre-sized bodies that are spherical, oblate or elongate in shape. For a long time, these minute structures were regarded as the remains of biofilms of keratinophilic bacteria, but recently they have been reinterpreted as melanosomes; that is, colour-bearing organelles. Resolving this funda...
We discuss the evolution of cosmological magnetic fields from the early universe to the present. We review different scenarios for magnetogenesis in the early universe and follow the subsequent evolution of these fields as the universe recombines. We then focus on the role primordial fields play after recombination in the seeding of stellar and galactic fields and the formation of structure. Co...
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