نتایج جستجو برای: fluvial sedimentation
تعداد نتایج: 22091 فیلتر نتایج به سال:
In the Weichselian, the Lower Rhine in the Dutch-German border region has used three courses, dissecting ice-marginal topography inherited from the Saalian. In the Late Weichselian, the three courses functioned simultaneously, with the central one gaining importance and the outer ones abandoning. This study aims to reconstruct the fluvial development and forcings that culminated in abandonment ...
This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars S...
Agricultural land covers approximately 40% of Earth's land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter (DOM), which constitutes the main vector of carbon transport from soils to fluvial networks and to...
We report evidence for Milankovitch cycles discovered in Middle Permian strata of the fluvial Abrahamskraal formation, lower Beaufort Group, Karoo Basin Northern Cape Province, South Africa. Statistical analyses ranked lithologies and major element oxides have been used to obtain clusters elements that capture lithological variations reflect changes sedimentary environment through time. Spectra...
Over the past 10 years the Rosgen classification system and its associated methods of ‘‘natural channel design’’ have become synonymous to some with the term ‘‘stream restoration’’ and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely adopted by governmental agencies, particularly those funding restoration projects. The purposes of this ar...
The ecology of viruses has been studied only in a limited number of rivers and streams. In light of a recent re-appraisal of the global fluvial surface area, issues such as abundance and production, host mortality and the influence of suspended particles and biofilms are addressed. Viral life cycles, potential impacts of viruses on water biochemistry and carbon flow, and viral diversity are con...
Widespread Amazonian-aged fluvial channels have been mapped proximal to Lyot crater, a ~225 km diameter impact basin in the northern lowlands of Mars. Comparable in area to some Noachian/Hesperian fluvial systems, their morphology differs, being dominated by broad, shallow braided channels. Using new developments in the study of cratering, water inventory, and climate history, we assess eight d...
A series of cyclic direct simple shear tests are performed to investigate the liquefaction resistance sandy soils from Christchurch, New Zealand. The study focuses on combined effects soil density and fines content soils. Two sands, a non-plastic silt, their mixtures prepared at different contents tested two sets relative densities. Test specimens reconstituted using procedure for water sedimen...
The wandering reach of the lower Yellow River has undergone significant channel degradation since Xiaolangdi Reservoir operation, with a cumulative scour volume 14.1 × 108 m3 in 1999–2018, and severe resulted rapid incision this reach. annual river bed downcutting depths at section- reach-scales water stages low high flows were calculated to investigate characteristics quantitatively. results s...
[1] We present evidence that a final epoch of widespread fluvial erosion and deposition in the cratered highlands during the latest Noachian or early to mid-Hesperian was characterized by integration of flow within drainage networks as long as 4000 km and trunk valley incision of 50 to 350 m into earlier Noachian depositional basins. Locally deltaic sediments were deposited where incised valley...
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