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The AAPG/Datapages Combined Publications Database

GCAGS Transactions


Gulf Coast Association of Geological Societies Transactions
Vol. 15 (1965), Pages 225-225

Abstract: Depositional Previous HitEnvironmentsNext Hit of the Mississippi River Previous HitDeltaicNext Hit Plain--Southeastern Louisiana

Charles R. Kolb, Jack R. van Lopik

Seaward progradation of the land surface by the present and former Mississippi River deltas has created the Recent Previous HitdeltaicNext Hit plain of southeastern Louisiana. Each time the Mississippi has advanced a major Previous HitdeltaicNext Hit lobe seaward, subsequent abandonment of the overly extended river course in favor of a shorter, more direct route to the Gulf has occurred. These course changes and accompanying shifts in centers of deposition have resulted in the distribution of Previous HitdeltaicNext Hit sediments along a 200-mile arc in coastal Louisiana. As soon as a depositional center or delta is abandoned, marine transgression begins. This process is aided by subsidence of the Previous HitdeltaicNext Hit plain as a result of tectonism and gradual consolidation of Previous HitdeltaicNext Hit deposits. Nevertheless, the net result of the struggle between the advancing deltas and the encroaching sea has been an over-all increase in the size of the Recent Previous HitdeltaicNext Hit plain.

The sediments of four major depositional Previous HitenvironmentsNext Hit are complexly interfingered in the Previous HitdeltaicTop plain: (1) Fluvial--natural levee, point bar, abandoned course and abandoned distributary sediments deposited in fresh to brackish water principally in inland areas within and along streams; (2) Fluvial-Marine--prodelta, intradelta and interdistributary sediments laid down near the mouths of distributary channels in brackish to marine water; (3) Paludal--marsh, swamp, tidal channel and lacustrine deposits formed primarily in situ; and (4) Marine--bay-sound, reef, beach and nearshore gulf sediments formed by erosion and deposition in marine water. Processes active within each environment and the distribution and physical properties of associated deposits or soil types are of vital interest in investigations of engineering geologists.

1. Presented at Symposium on the Geology of Deltas, arranged by the Houston Geological Society.

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