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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 7 (1957), Pages 153-164

A Quaternary Molluscan Assemblage from Orleans Parish, Louisiana

Charles L. Rowett (1)

ABSTRACT

The construction of a new highway along the southeastern margin of Lake Pontchartrain revealed the presence of a normal marine faunal assemblage in the sand being dredged for the roadbed fill. A detailed study was undertaken to determine: (1) the environmental conditions prevailing at the time of deposition of the sediments containing the fauna, (2) the geologic age of the fauna, and (3) the paleogeography of the area at that time.

Ninety-one representative species were collected and identified. Comparisons then were made with species listed for the seven assemblages and corresponding environments recorded by Robert H. Parker in his recent paper (1956), "Macro-Invertebrate Assemblages as Indicators of Sedimentary Environments in East Mississippi Delta Region." These seven divisions were established by Parker on the bases of the distribution of macro-organisms collected in the Breton Sound Area at more than 280 stations over a period of almost three years, the published records of similar occurrences of macro-organisms, and the several environmental complexes affecting animal distribution. They are: (I) the delta marshes, (II) the delta front and lower distributaries, (III) the lower sound and prodelta slope, (IV) the upper sound, (V) the inlets or passes, (VI) the shallow continental shelf, and (VII) the deep continental shelf.

The molluscan fauna under study is shown conclusively to be representative of the shallow continental shelf assemblage listed by Parker. The assignment of this fauna to a specific environmental assemblage gives access to many of the physical aspects of the biotope. The relationship of this ancient environment to adjacent landmasses is determined more precisely by analysis of various factors influencing the distribution of certain significant species. The fauna is interpreted as having lived on the gulf side of a barrier island similar to those now existing off the Mississippi Sound. It is believed to be of late Pleistocene or early Post-Pleistocene age.


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