نتایج جستجو برای: core sediments
تعداد نتایج: 242236 فیلتر نتایج به سال:
In deep-sea geothermal rift zones, the dispersal of hydrothermal fluids of moderately-high temperatures typically forms subseafloor mounds. Major mineral components of the crust covering the mound are barite and metal sulfides. As a result of the continental rifting along the Red Sea, metalliferous sediments accumulate on the seafloor of the Atlantis II Deep. In the present study, a barite crus...
Fish farming has seriously influenced the aquatic environment in Sancha reservoir in SW China since 1985 and has been strongly restricted since 2005. Thus, phosphorus speciation in a sediment core dated between 1945 and 2010 at cm-resolution and in surface sediments from Sancha reservoir may allow us track how fish farming impacts phosphorus dynamics in lake sediments. Fish farming shifts the m...
Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20 degrees latitude, showed great variability with respect to Pb concentr...
Despite regulations controlling anthropogenic mercury sources in North America, high levels of mercury in coastal fish and shellfish are an ongoing problem in Maritime Canada and the Northeastern United States. This study presents sediment core data from a macrotidal estuary located at the mouth of the Bay of Fundy showing stratigraphic profiles of total and methylmercury concentrations and pot...
High-resolution magnetic measurements were performed on sediments recovered from Sites 966, 967, and 969 during Leg 160 of the Ocean Drilling Program to the eastern Mediterranean Sea. Measurements of u-channel samples were made at 1-cm intervals from nearly complete composite stratigraphic sequences at each site. The measurements are integrated over stratigraphic intervals of 4.5 cm, which allo...
The cryosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences underlying the modern McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line position and main icestream flow directi...
The Pass Peak Formation is a Tertiary basin-flank deposit exposed throughout much of the Hoback Basin; a depression physiographically distinct from, but structurally continuous with, the northern Green River Basin. Two lithofacies of the Pass Peak Formation are identified. A northern quartzite conglomeratesandstone facies, possibly as thick as 3200 ft, intertongues southward with a sandstone-si...
In sediments that contain iron monosulfide, cadmium, nickel, lead, zinc, and silver(I) form insoluble metal sulfides that lower the metal ion activity in the sediment-pore water system, thereby reducing toxicity. However, metal sulfides are susceptible to oxidation by molecular oxygen resulting in metal solubilization. To better understand the sources and sinks of metal sulfides in sediments, i...
Global databases of calcium carbonate concentrations and mass accumulation rates in Holocene and last glacial maximum sediments were used to estimate the deep-sea sedimentary calcium carbonate burial rate during these two time intervals. Sparse calcite mass accumulation rate data were extrapolated across regions of varying calcium carbonate concentration using a gridded map of calcium carbonate...
Influence of benthic macroinvertebrates on mixing of profundal sediments in southeastern Lake Huron1
Vertical distributions of size classed benthic macroinvertebrates were investigated in centimeter-thick sections of twelve cores from each of two stations in southern Lake Huron. Stations were selected on the basis of radioactivity profiles indicating surf&e sediment mixing to 3 and 6 cm. The corresponding occurrence of major taxonomic groups (amphipods and oligochaetes) to 2 cm at the first st...
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