نتایج جستجو برای: diagenetic origin
تعداد نتایج: 200395 فیلتر نتایج به سال:
The Valley of Lakes is approximately a 500-km elongate depression in Central Mongolia, where Eocene to Miocene continental sediments are long known for their outstanding fossil richness. The palaeontological record of this region is an exceptional witness for the evolution of mammalian communities during the Cenozoic global cooling and regional aridification. In order to precisely elucidate the...
Lead poisoning has been suggested as being partially responsible for the ‘demise’ of the British military in the West Indies during the colonial era. Lead was pervasive in the colonial environment, being employed in items such as eating and cooking utensils, water catchments and alcohol distillation equipment. This preliminary study represents the first attempt to determine whether this suggest...
Here we describe variations in osteocytes derived from each of the three bone layers that comprise the turtle shell. We examine osteocytes in bone from four extant turtle species to form a morphological 'baseline', and then compare these with morphologies of osteocytes preserved in Cenozoic and Mesozoic fossils. Two different morphotypes of osteocytes are recognized: flattened-oblate osteocytes...
mauddud member with the age of late albian to cenomanian is equivalent to the lower sarvak formation in the southern persian gulf and adjacent area. in this work, microfacies, depositional environment, and diagenetic processes affected the mauddud member in a field in the persian gulf are investigated. based on the studies of available cores and thin sections of 3 wells, five types of microfaci...
Biological markers are organic compounds in geological samples with an unambiguous link to specific precursor molecules in living organisms. They provide information on the origin and depositional environment of fossil organic matter as well as about its thermal maturation caused by geothermal heat flow during burial. Petroleum and its refinery products carry this biomarker information into the...
Oxygen, carbon, and strontium isotope variations in vein-filling calcite and quartz cements and their host rocks are used to elucidate the origin, spatial and temporal evolution, and migration pathways of fluids in the detachment Nuncios fold complex, northeastern Mexico. The folded Mesozoic sedimentary sequence contains two regional paleohydrostratigraphic units separated by a unit of low perm...
The enigmatic Paleozoic fossil Prototaxites Dawson 1859 consists of tree-like trunks as long as 8 m constructed of interwoven tubes <50 mm in diameter. Prototaxites specimens from fi ve localities differ from contemporaneous vascular plants by exhibiting a carbon isotopic range, within and between localities, of as much as 13‰ δ13C. Pyrolysis–gas chromatography–mass spectrometry highlights comp...
Hydrogen cyanide is an excellent organic reagent and is central to most of the reaction pathways leading to abiotic formation of simple organic compounds containing nitrogen, such as amino acids, purines and pyrimidines. Reduced carbon and nitrogen precursor compounds for the synthesis of HCN may be formed under off-axis hydrothermal conditions in oceanic lithosphere in the presence of native F...
A subterranean, stone-built, sediment-filled culvert discovered during excavations at the Agora (Athens, Greece) was dated to the Roman period on the basis of its characteristic construction and associated finds, including coins. The location of the culvert relative to other adjacent watercourses and an ancient river bed suggested that the structure was a sewer. This was confirmed through a mul...
-The chemical and the mineralogical composition of a group of pumiceous tufts associated with recent salic volcanic episodes from Tenerife (Canary Islands) have been studied. The investigation focused on the two main types of pyroclastic deposits of the zone: ash-flows and ash-falls. The samples can be classified chemically as trachytic and phonolitic rocks with an intermediate silica content a...
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