--> ABSTRACT: Reconstruction of Paleoenvironment in Abandoned Mississippi Delta, Louisiana, by Hi-Il Ye; #91030 (2010)

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Reconstruction of Paleoenvironment in Abandoned Mississippi Delta, Louisiana

Hi-Il Ye

Eight stages of depositional history in the interdistributary basin during the last 4,200 years were recognized based on radiocarbon dates and the corelation of the sedimentary sequences. Fresh/brackish bay and fresh lake/pond deposits were predominant during stage one (3,500-4,200 years B.P.). Crevasse/overbank deposits occurred widely during stage two (2,700-3,500 years B.P.), indicating the distributaries were active. Floating marsh and detrital organic flat deposits were first developed during stage three (2,000-3,000 years B.P.). During stage four (1,500-2,000 years B.P.), crevasse/overbank and fresh/brackish bay deposits were predominant. Detrital organic flat and floating marsh deposits still remained but were restricted in the central portion of the St. Bernard ba in. Crevasse/overbank deposits in this stage were the second major sediment influx since stage two.

More floating marsh was developed during stage five (1,500-2,000 years B.P.). Firmland marsh began developing during stage six (500-1,000 years B.P.) and expanding during stage seven (250-500 years B.P.). Therefore, the distribution of floating marsh area was diminished during these two stages. Finally, firmland marsh occupied the entire study area during stage eight (250 years B.P. to present). This study area is now continuously subsiding, and the deterioration of firmland marsh is causing the enlargement of the present brackish lake/pond and brackish/saline bay environment.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.