Filters: Tags: Grain size (X)68 results (200ms)
Permeability–porosity relationships for sediments from the northern Barbados, Costa Rica, Nankai, and Peru subduction zones were examined based on sediment type, grain size distribution, and general mechanical and chemical compaction history. Greater correlation was observed between permeability and porosity in siliciclastic sediments, diatom oozes, and nannofossil chalks than in nannofossil oozes. For siliciclastic sediments, grouping of sediments by percentage of clay-sized material yields relationships that are generally consistent with results from other marine settings and suggests decreasing permeability as percentage of clay-sized material increases. Correction of measured porosities for smectite content...
Grain size distribution effects on phosphate sorption by fluvial sediment: Implications for modelling sediment-phosphate transport
Sources of stream sediments in the granulite terrain of the Walawe Ganga Basin, Sri Lanka, indicated by rare earth element geochemistry
Sediment magnetic, paleomagnetic and geochemical results have beenobtained from lacustrine sediments recovered in a 30-meter coretaken by rotary drilling methods at Grass Lake, Siskiyou County,California. The data have been analyzed and interpreted in termsof environmental change in the Grass Lake catchment over the pastca. 100,000 years.
Coupled changes in sand grain size and sand transport driven by changes in the upstream supply of sand in the Colorado River: Relative importance of changes in bed-sand grain size and bed-sand area
Sand transport in the Colorado River in Marble and Grand canyons was naturally limited by the upstream supply of sand. Prior to the 1963 closure of Glen Canyon Dam, the river exhibited the following four effects of sand supply limitation: (1) hysteresis in sediment concentration, (2) hysteresis in sediment grain size coupled to the hysteresis in sediment concentration, (3) production of inversely graded flood deposits, and (4) development or modification of a lag between the time of a flood peak and the time of either maximum or minimum (depending on reach geometry) bed elevation. Construction and operation of the dam has enhanced the degree to which the first two of these four effects are evident, and has not affected...
Regulation of sand transport in the Colorado River by changes in the surface grain size of eddy sandbars over multi-year timescales
In settings where the transport of sand is partially or fully supply limited, changes in the upstream supply of sand are coupled to changes in the grain size of sand on the bed. In this manner, the transport of sand under the supply-limited case is ‘grain-size regulated’. Since the closure of Glen Canyon Dam in 1963, the downstream reach of the Colorado River in Marble and Grand Canyons has exhibited evidence of sand-supply limitation. Sand transport in the river is now approximately equally regulated by changes in the discharge of water and changes in the grain sizes of sand on the channel bed and eddy sandbars. Previous work has shown that changes in the grain size of sand on the bed of the channel (driven by...
The drilling project at Owens Lake commenced in April,1991. This Open-File Report represents an effort to makeavailable to other researchers our preliminary datacollected during the first year of study followingcompletion of the core-drilling phase. Nineteen datacollections and preliminary interpretations are presentedin the following sections. They are the work of fifteenfirst-authors and their numerous co-authors. Broadly,their topics include a field log of the core(1 contribution), sedimentological analyses (1), clay-mineral identification (1), geochemical analyses (5),dating and age estimates of the cored sediments (4), andidentifications of fossil materials (7).
Assessing the biological and physical dynamics of intertidal sediment ecosystems. A remote sensing approach (project BIOPTIS)
Analysis of the relationship between sediment composition and benthic community structure in coastal deposits: Implications for marine aggregate dredging
Granulometric characteristics and its environmental significance of core in small lagoon of Yongshu Atoll.
Glen Canyon Dam has caused a fundamental change in the distribution of fine sediment storage in the 99-km reach of the Colorado River in Marble Canyon, Grand Canyon National Park, Arizona. The two major storage sites for fine sediment (i.e., sand and finer material) in this canyon river are lateral recirculation eddies and the main-channel bed. We use a combination of methods, including direct measurement of sediment storage change, measurements of sediment flux, and comparison of the grain size of sediment found in different storage sites relative to the supply and that in transport, in order to evaluate the change in both the volume and location of sediment storage. The analysis shows that the bed of the main...