Changes

[[file:NileDelta.jpg|thumb|400px|The contrast between the lush vegetation of the Nile delta and river course and the dry sand of the Sahara can be seen spectacularly in this enhanced true colour Medium Resolution Imaging Spectrometer (MERIS) image. The grey area to the bottom of the "triangle" of the delta is Egypt's Capitol, Cairo. On the border between Israel and Jordan is the Dead Sea, at 412m below the level of the Mediterranean, the lowest point on earth. The Dead Sea also has salinity 10 times that of the Mediterranean, and due to the high evaporation rate in the area, salt accumulates, and can be extracted, as can be seen in the southern part of this large inland lake. The lighter blue/green areas are increased evaporite deposits, in this case salt. We can also see the structure of the saltpans crossed vertically by a canal. ESA, 2003 http://bit.ly/1l8WdhM]]

[[file:NileDelta.jpg|thumb|400px|The contrast between the lush vegetation of the Nile delta and river course and the dry sand of the Sahara can be seen spectacularly in this enhanced true colour Medium Resolution Imaging Spectrometer (MERIS) image. The grey area to the bottom of the "triangle" of the delta is Egypt's Capitol, Cairo. On the border between Israel and Jordan is the Dead Sea, at 412m below the level of the Mediterranean, the lowest point on earth. The Dead Sea also has salinity 10 times that of the Mediterranean, and due to the high evaporation rate in the area, salt accumulates, and can be extracted, as can be seen in the southern part of this large inland lake. The lighter blue/green areas are increased evaporite deposits, in this case salt. We can also see the structure of the saltpans crossed vertically by a canal. ESA, 2003 http://bit.ly/1l8WdhM]]

Deltaic [[depositional facies]] result from interacting dynamics processes (wave energy, tidal regime, currents, climate, etc.), which modify and disperse riverborne ([[fluvial]]) [[clastic deposits]]. The term delta was first applied by the Greek philosopher Herodotus (490 B.C.) to the triangular land surface formed by deposits from Nile River distributaries. In the broadest sense deltas can be defined as those depositional features, both subaerial and subaqueous, formed by [[fluvial sediment]]s. In many instances the deposition of fluvial sediments is strongly modified by marine forces such as waves, currents and tides, and depositional features found in deltas therefore display a high degree of variability. Depositional features include [[distributary channel]]s, [[river-mouth bar]]s, [[interdistributary bay]]s, [[tidal flat]]s, [[tidal ridge]]s, [[beaches]], [[Lithofacies_and_environmental_analysis_of_clastic_depositional_systems#Eolian_deposits|eolian dune]]s, [[swamp]]s, [[marshes]], and [[evaporite flat]]s.<ref name=Coleman_1976>Coleman, J. M., 1976, Deltas: Processes of deposition and models for exploration: Continuing Education Publication Company, Champaign, IL, 102 p.</ref>

Deltaic [[depositional facies]] result from interacting dynamics processes (wave energy, tidal regime, currents, climate, etc.), which modify and disperse riverborne ([[fluvial]]) [[clastic deposits]]. The term delta was first applied by the Greek philosopher Herodotus (490 B.C.) to the triangular land surface formed by deposits from Nile River distributaries. In the broadest sense deltas can be defined as those depositional features, both subaerial and subaqueous, formed by [[fluvial sediment]]s. In many instances the deposition of fluvial sediments is strongly modified by marine forces such as waves, currents and tides, and depositional features found in deltas therefore display a high degree of variability. Depositional features include [[distributary channel]]s, [[river-mouth bar]]s, [[interdistributary bay]]s, [[tidal flat]]s, [[tidal ridge]]s, [[beaches]], [[Lithofacies_and_environmental_analysis_of_clastic_depositional_systems#Eolian_deposits|eolian dune]]s, [[swamp]]s, [[marshes]], and [[Sabkha|evaporite flat]]s.<ref name=Coleman_1976>Coleman, J. M., 1976, Deltas: Processes of deposition and models for exploration: Continuing Education Publication Company, Champaign, IL, 102 p.</ref>

A significant deltaic accumulation necessarily requires the existence of a river system carrying substantial quantities of [[clastic sediment]] from an inland drainage basin to the coast, where the deposits form the delta plain. Modern deltas exist under a wide range of environmental processes; some deltas form along coasts experiencing negligible tides and minimal wave energy, whereas others form in areas where tide ranges are extreme and wave energy is intense. Despite the environmental contrasts, all actively prograding deltas have at least one common feature--a river supplies clastic sediment to the coast and adjacent shelf more rapidly than it can be dispersed by marine processes, and thus a regressive sedimentary deposit forms.

A significant deltaic accumulation necessarily requires the existence of a river system carrying substantial quantities of [[clastic sediment]] from an inland drainage basin to the coast, where the deposits form the delta plain. Modern deltas exist under a wide range of environmental processes; some deltas form along coasts experiencing negligible tides and minimal wave energy, whereas others form in areas where tide ranges are extreme and wave energy is intense. Despite the environmental contrasts, all actively prograding deltas have at least one common feature--a river supplies clastic sediment to the coast and adjacent shelf more rapidly than it can be dispersed by marine processes, and thus a regressive sedimentary deposit forms.