نتایج جستجو برای: grained sediments
تعداد نتایج: 51407 فیلتر نتایج به سال:
Recent theoretical investigations suggest that the rate of river incision into bedrock depends nonlinearly on sediment supply, challenging the common assumption that incision rate is simply proportional to stream power. Our measurements from laboratory abrasion mills support the hypothesis that sediment promotes erosion at low supply rates by providing tools for abrasion, but inhibits erosion a...
We study the displacement of immiscible fluids in deformable, noncohesive granular media. Experimentally, we inject air into a thin bed of water-saturated glass beads and observe the invasion morphology. The control parameters are the injection rate, the bead size, and the confining stress. We identify three invasion regimes: capillary fingering, viscous fingering, and "capillary fracturing," w...
The present study investigates the performances of the three-dimensional multicomponent hydro-sedimentary model ROMS (Regional Ocean Modeling System) to predict near-surface suspended sediment concentrations (SSC) in the English Channel (western Europe). Predictions are assessed against satellite-retrieved observations from raw MODIS and MERIS images for the year 2008 characterized by the highe...
[1] Multiproxy data from ODP Hole 1017E (Point Conception, California) provide an excellent opportunity to examine the behavior of barium, within a well‐characterized sedimentary system. Bariumexcess is generally considered to be a productivity proxy; however, in nearshore environments, Baexcess records can be compromised by both sediment provenance and barite remobilization. For the last 60 ky...
The term "black shale" is a common expression widely used to describe any dark~olored, fine-grained sedimentary rock relatively rich in organic matter. As defined by Weissert (1981), the range of organic carbon in black shales is between 1 and 30%, but values outside this range exist. The term usually connotes at least partial lithification, yet this may not be true in young, shallow sediments....
Test borings in the western basin of Lake Erie have revealed an extensive sub-bottom deposit of sand in a triangular region bounded by Stony Point on the mainland shore of Michigan, Middle Sister Island in Ontario, and West Sister Island in Ohio. The 550 km deposit is overlain by up to 7 m of more recent lacustrine silts and clays. The sand beds have an average thickness of 2.3 m, yielding a to...
X-ray mapping is increasingly used in the geological sciences for qualitative observations of textures, mineral zoning, and element distribution among rock components [1-4]. We combine mapping with an aggressive program of image analysis in deepening our understanding of the early solar system through the analysis of chondritic meteorites [5, 6]. Chondrites are “sediments” that accreted in the ...
Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features inc...
Sediments and rocks recovered in CRP-2/2A coring operations contain relatively little organic matter (average TOC=0.28%) and very small amounts of solvent-soluble organic matter. Because Early Oligocene sediment included significant amounts of coal detritus, TOC values are higher in Early Oligocene rocks than in younger rocks. TOC values are highest in the fine-grained rocks deposited as part o...
On the upper slope of the northern Gulf of Mexico, topographic features are often associated with authigenic carbonate, which provides hard substrate for sessile benthic communities. At depths >300 m, large Lophelia pertusa colonies frequently occur on these carbonate outcroppings. Surficial sediments at these depths are dominated by fine-grained particulates, which are readily resuspended duri...
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