نتایج جستجو برای: sedimentary geochemistry
تعداد نتایج: 16788 فیلتر نتایج به سال:
Island arc lavas, erupted above subduction zones, commonly contain a geochemical component derived from partial melting of subducted sediment. It is debated whether this sediment melt signature, with enriched trace element concentrations and isotope ratios, forms at relatively low or high temperatures. Here we compile and analyse the geochemistry of metamorphosed sedimentary rocks that have bee...
Numerous studies have been made of Recent Red Sea sediments concerning their paleontology, mineralogy, or geochemistry. In addition, over 50 reports have been published on the sedimentary environment of the hot brine area (21°N) in the central axial valley (see Degens and Ross, 1969, and contained references; Backer and Schoell, 1972). These studies generally indicate considerable climatic fluc...
Hangzhou, China, is a world-famous tourist city. With the increase of the urban population and the development of tourism, the requirement of the quantity and quality of groundwater is steadily increasing. Hangzhou region evolved from the ancient shallow sea gulf. According to the local chronicle (Compilation Commission on Hangzhou Chorography (CCHC) 2000), the subsurface water was not potable ...
Microfossils, stromatolites, preserved lipids and biologically informative isotopic ratios provide a substantial record of bacterial diversity and biogeochemical cycles in Proterozoic (2500-541 Ma) oceans that can be interpreted, at least broadly, in terms of present-day organisms and metabolic processes. Archean (more than 2500 Ma) sedimentary rocks add at least a billion years to the recorded...
In order to interpret the marine clastic record preserved in the sedimentary basins of the East Asian marginal seas, it is important to understand how sediment transport and chemical weathering affect the composition of sediment enroute to its sink. Here we present a new data set for fine-grained sediment (<63 μm) from the Yangtze River and its major tributaries, which represents a baseline for...
Seasonal oxygen depletion (hypoxia) in coastal bottom waters can lead to the release and persistence of free sulfide (euxinia), which is highly detrimental to marine life. Although coastal hypoxia is relatively common, reports of euxinia are less frequent, which suggests that certain environmental controls can delay the onset of euxinia. However, these controls and their prevalence are poorly u...
Geological records from the Antarctic margin offer direct evidence of environmental variability at high southern latitudes and provide insight regarding ice sheet sensitivity to past climate change. The early to mid-Miocene (23-14 Mya) is a compelling interval to study as global temperatures and atmospheric CO2 concentrations were similar to those projected for coming centuries. Importantly, th...
gamma-rays emitted from the ground surface relate to the primary mineralogy and geochemistryof the bedrock, and the secondary weathered materials. this information can contribute significantly to anunderstanding of the geochemical and pedogenetic history of a region. the main aim of this paper was to study the relationship between ground gamma-ray data and basement geochemistry in the lese catc...
Abstract Geological investigations of a part the crystalline basement in Baltic Sea have been performed on drill core collected from depth 1092–1093 m beneath Phanerozoic sedimentary cover offshore Latvian/Lithuanian border. The sample was analyzed for geochemistry and dated with SIMS U–Pb zircon method. Inherited cores this migmatized granodioritic orthogneiss an age 1854 ± 15 Ma. Its chemical...
Abstract. Lake Maryut (northwestern Nile Delta, Egypt) was a key feature of Alexandria's hinterland and economy during Greco-Roman times. Its shores accommodated major economic centers, the lake acted as gateway between valley Mediterranean. It is suggested that lake-level changes, connections with sea, possible high-energy events considerably shaped human occupation history Maryut. To reconstr...
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