نتایج جستجو برای: lacustrine environment

تعداد نتایج: 519568  

Journal: :Acta Crystallographica Section A Foundations of Crystallography 1996

Journal: :Geology 2022

Abstract Resource pulses, occasional events of ephemeral resource superabundance, represent a fundamental mechanism by which energy, nutrients, and biomass are transported across ecotones. They widespread in extant ecosystems; however, little is known about their deep-time record. We report the earliest-known mayfly swarm from Early Jurassic Xiwan biota southern China. Our taphonomic sedimentol...

2007
Beth Pratt-Sitaula Michelle Garde Douglas W. Burbank Michael Oskin Arjun Heimsath Emmanuel Gabet

About 5400 cal yr BP, a large landslide formed a N400-m-tall dam in the upper Marsyandi River, central Nepal. The resulting lacustrine and deltaic deposits stretched N7 km upstream, reaching a thickness of 120 m. C dating of 7 wood fragments reveals that the aggradation and subsequent incision occurred remarkably quickly (∼500 yr). Reconstructed volumes of lacustrine (∼0.16 km) and deltaic (∼0....

2006
B. J. Szabo

As documented by radiocarbon dating and geoarchaeological investigations, the now hyperarid northwestern Sudan and southwestern Egypt experienced a period of greater effective moisture during early and middle Holocene time, about 10-5 ka. We have used the uranium-series technique to date lacustrine carbonates from Bir Tarfawi, Bir Sahara East, Wadi Hussein, Oyo Depression, and the Great Selima ...

2015
Gilad Bino Richard T. Kingsford John Porter Travis Longcore

Dryland rivers have considerable flow variability, producing complex ecosystems, processes, and communities of organisms that vary over space and time. They are also among the more vulnerable of the world's ecosystems. A key strategy for conservation of dryland rivers is identifying and maintaining key sites for biodiversity conservation, particularly protecting the quantity and quality of flow...

2013
Huichao Dai Jingqiao Mao Dingguo Jiang Lingling Wang

Three Gorges Reservoir (TGR) is one of the largest man-made lakes in the world. Since the impoundment in 2003, however, algal blooms have been often observed in the tributary embayments. To control the algal blooms, a thorough understanding of the hydrodynamics (e.g., flow regime, velocity gradient, and velocity magnitude and direction) in the tributary embayments is particularly important. Usi...

2004
Carmala N. Garzione David L. Dettman Brian K. Horton

Carbonate oxygen isotope paleoaltimetry is based on analysis of the dO value of carbonate precipitated from surface water. Deciphering the diagenetic history is important for establishing whether particular carbonates are accurate recorders of paleosurface waters, which reflect paleoelevation. This study provides examples from southern, east–central, and northeastern Tibet of approaches aimed a...

Journal: :Proceedings. Biological sciences 2006
Keonho Kim Alexey A Kotov Derek J Taylor

Cyclic parthenogens have a mixed breeding system with both meiotic and ameiotic eggs. Although investment in sexual stages is often synchronized with seasonal cycles, the degree of investment is a quantitative trait associated with habitat instability. Populations of cyclic parthenogens from stable environments, such as large lakes and oceans, generally show reduced or undetectable investment i...

2016
Baoli Wang Cong-Qiang Liu Stephen C. Maberly Fushun Wang Jens Hartmann

Carbon (C) and silicon (Si) biogeochemical cycles are important factors in the regulation of atmospheric CO2 concentrations and hence climate change. Theoretically, these elements are linked by chemical weathering and organism stoichiometry, but this coupling has not been investigated in freshwaters. Here we compiled data from global rivers and lakes in the United States of America and the Unit...

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