• Desert environments - River environments preserve evidence of channelized sediment transport. Sand and gravel fill concave-up channels that often scour into previously deposited floodplain fines. Fine sand, silt, and clay are deposited on nearby floodplains. • River environments - Lake environments result from large ponded bodies of freshwater. Gravels and sands are trapped near shore. Well-sorted muds are deposited in deeper water. They are often capped with wetland muds. Deep lake muds may show varves, thin stripes of alternating finer and coarser sediment reflecting seasonal changes in sedimentation. • Lake environments - Gravel collects in nearly horizontal topset beds downstream.Gravel and sand collect in sloping foreset beds where theres standing water. Further down finer sediment collects in horizontal bottomset beds. • Delta environments - Deepwater sediments being buried by shallower • Marine Delta Environments - find more resources at oneclass.com find more resources at oneclass.com
Deepwater sediments being buried by shallower water sediments • In a marine-delta environment, sediment accumulates where river velocity drops upon entering the sea. Deltas grow over time, building out into the basin. Many subenvironments are present. • Shallow-marine clastic deposits are composed of fine sands and silts that accumulate in quieter waters offshore. The sea floor in these settings supports active biotic communities. • Shallow marine clastic environment - Shallow-water carbonate environments develop in tropical, warm, clear, shallow, normal salinity, marine water. Protected lagoons accumulate mud. Wave-tossed reefs are made of coral and reef debris. • • Shallow water carbonate environments - Deep-marine deposits accumulate fines that settle out far from land. The skeletons of planktonic organisms make chalk or chert; fine silt and clay lithifies into shale. • Deep marine environments - Sedimentary basins are special places that Sedimentary Basins - Plate tectonics - find more resources at oneclass.com find more resources at oneclass.com
Sedimentary basins are special places that accumulate sediment. Sediments vary in thickness across Earth’s surface, from zero to 20+ km in sedimentary basins. Foreland basins form on the craton side of collisional mountain belt. The lithosphere on the craton flexes because of the loading from thrust sheets and fold thickening. Flexure of the crust from loading creates a downwarp, which fills with the erosional debris shed off of the mountains. Rift basins form at divergent (pull-apart) plate boundaries. The crust thins by stretching and rotational normal faulting, and the thinned crust subsides. Sediment fills in the down-dropped basins as they continue to subside. Intracontinental basins form in the interior of the craton, far from continental margins or tectonic- plate boundaries. These basins are thought to result from differential thermal subsidence and may be linked to instabilities in the craton from former tectonism, such as failed crustal rifts, etc.
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- Plate Tectonics, Mid-Atlantic Ridge, § Island