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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 64 (1980)

Issue: 9. (September)

First Page: 1560

Last Page: 1561

Title: Louisiana Chenier System--Some Preliminary Reinterpretations and Refinements: ABSTRACT

Author(s): R. T. Kaczorowski

Article Type: Meeting abstract


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The Louisiana chenier system is the product of a complex interaction of coastal, riverine, biologic, and storm processes. An important component of the chenier system, the chenier ridge, has been described as an accumulation of sand and/or shell material winnowed from existing marsh and tidal flat deposits. According to most interpretations, these ridges are correlative with changes in the flow direction of the Mississippi River from west to east. Most workers believe that the extensive mudflat and marsh sediments that separate the chenier ridges represent periods of progradation, influenced by a high sediment load from the Mississippi during periods of westerly discharge. These alternating periods of easterly and westerly flows represent the classical model that has been presented fo genesis of the chenier plain during the past 3,000 years.

While it is generally agreed that Mississippi River sedimentation has been a major factor in the development of coastal geomorphology of southwestern Louisiana, the "flip/flop" model presented above is over-simplified. Furthermore, the term, chenier ridge, has been indiscriminately applied to almost any morphologic unit within the system that shows noticeable relief as reflected in vegetative development. Therefore, little genetic significance should be ascribed to the term. Multiple beach ridges, recurved spits, overwash deposits, storm berms, strandline ridges, perched beaches, and ancient oyster reefs all quality as chenier ridges under previous guidelines.

A more serious problem that appears with the Mississippi River flip/flop model is that relict shoreline dates are not directly correlative with the Mississippi delta-lobe dates, and a growth rate curve of the chenier plain does not support this model.

If the modern southwestern Louisiana coastal zone is examined, several distinctly different environments are encountered: shelly sand beaches, exposed tidal mudflats, and eroding marsh deposits. The conceptual model that has been implied in previous studies of a strandline consisting either of chenier ridges or a marsh/tidal flat environment, depending on the Mississippi River discharge direction, appears to be unjustified on the basis of modern day conditions and C14 dating. Refinements in the model based on current field work and further dating should yield a more detailed and integrated picture of the development of the chenier system through time.

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