نتایج جستجو برای: detrital deposit
تعداد نتایج: 19486 فیلتر نتایج به سال:
The enrichment and depletion of redox sensitive trace metals in marine sediments have been used extensively as paleoredox proxies. The trace metals in shale are comprised of both detrital (transported or particulate) and authigenic (precipitated, redox-driven) constituents, potentially complicating the use of this suite of proxies. Untangling the influence of these components is vital for the i...
the nasirabad manganese deposit is located 5 km south of nasirabad, 8 km sw of neyriz in the fars province. structurally, the area is placed in the southeastern part of zagros thrust belt. in this area, the manganese mineralization occurred as ore layers and nodules, interlayered with pichakun radiolarite chert deposits. in this study, mineralogy and geochemistry of uranium, thorium and lead is...
24 25 Chemical weathering and mechanical erosion are first order processes of long-term 26 tropical morphogenesis, which is still poorly deciphered for lack of time constraints. We 27 address this issue by laser-probe 39 Ar40 Ar dating of generations of cryptomelane [K128 2Mn8O16, nH2O] from the manganese ore deposit of Tambao in northern Burkina Faso. This 29 Mn deposit results from the superg...
The extensive Interior Alaska loess deposits record glacial advance and retreat over the past 3 Myrs. Refining our understanding of still-debated origins this will help us refine climate patterns since late Cenozoic. We present here first detrital-zircon ages from Gold Hill loess, a well-studied deposit in Fairbanks, Alaska, as well new local fluvial sediments. describe statistical approach to ...
9 We report oxygen and carbon isotope results of bulk and detrital carbonate grains 10 from the last glaciation at IODP Site U1308 (re-occupation of DSDP Site 609). Oxygen 11 isotopic values of individual detrital carbonate grains from Heinrich events average 12 -5.4‰±1.3‰, presumably reflecting values of limestone and dolomite derived from 13 lower Paleozoic basins in northern Canada and north...
The character and distribution of cooling ages in modern river sediment provide useful constraints on rates and patterns of uplift and erosion within actively deforming mountain ranges. Such sediment effectively samples all locations within the catchment area, irrespective of remoteness. We evaluate how successfully detrital cooling ages may be used to constrain hinterland erosion rates by exam...
Tošići-Dujići bauxite deposit, situated in Dalmatian inlands, Croatia, contains minor remaining reserves. The deposit lies on Lower Eocene foraminiferal limestone and is covered by Upper Promina sediments. Bauxite samples were analyzed for textural, mineralogical, geochemical features order to determine absolute REE abundances their relation mineralogy, as well devise the origin of enrichment t...
Detrital zircon studies are providing new insights on the evolution of sedimentary basins but the role of sedimentary recycling remains largely undefined. In a broad region of northwestern North America, this contribution traces the pathway of detrital zircon sand grains from Proterozoic sandstones through Phanerozoic strata and argues for multi-stage sedimentary recycling over more than a bill...
Ecosystem engineers change abiotic conditions, community assembly and ecosystem functioning. Consequently, their loss may modify thresholds of ecosystem response to disturbance and undermine ecosystem stability. This study investigates how loss of the bioturbating lugworm Arenicola marina modifies the response to macroalgal detrital enrichment of sediment biogeochemical properties, microphytobe...
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