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The AAPG/Datapages Combined Publications Database

Houston Geological Society

Abstract


Deltas in Their Geologic Framework, 1966
Pages 1-15

The Geological Importance of Deltas

E. H. Rainwater

Abstract

Most of the terrigenous clastic sediment which is preserved in the geologic column was deposited in marginal marine and shallow marine, nearshore Previous HitenvironmentsNext Hit. Much of these transitional sediments of sand, silt, and clay was transported by large streams from land masses to the coastal areas and deposited in deltas. In the Previous HitdeltaicNext Hit environment there was prolific organic production and rapid sedimentation to cover and preserve the organic material which was converted, soon after burial, to oil and gas. The hydrocarbons moved into porous, lenticular sands which were deposited at the fringes of the deltas and in distributary and tidal channels. In some basins faulting was contemporaneous with deposition, and upward growth of salt or shale diapirs resulted from the rapid Previous HitdeltaicNext Hit deposition. These local uplifts created structural traps in which the hydrocarbons could be concentrated. Thus, the Previous HitdeltaicNext Hit environment with abundant source beds, plentiful porous reservoirs, and numerous stratigraphic and structural traps was a favorable habitat for oil and gas.

It has been established that much of the oil and gas occurs in Previous HitdeltaicTop deposits; therefore, buried ancient deltas are very important. This fact was recognized more than twenty years ago by Houston geologists who promoted studies of modern deltas as an aid in finding ancient deltas. The results of investigations of Recent sediments and faunas were successfully applied in petroleum exploration in the Gulf Coast and other basins.


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