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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 64 (1980)

Issue: 9. (September)

First Page: 1553

Last Page: 1553

Title: Preliminary Observations of Modern Point Bar Facies, Amite River, Louisiana: ABSTRACT

Author(s): Whitney J. Autin, Chris M. Fontana

Article Type: Meeting abstract


The modern Amite River, an incised, flashy discharge stream, represents a coarse sand and gravel bed-load system typical of the Florida Parishes of southeastern Louisiana. Preliminary investigation provides general descriptions of channel morphology and sedimentology which permit the recognition of distinct point bar facies.

Bed-form and stratification types are used to differentiate lower bar, upper bar, and chute bar facies. The lower bar facies contain transverse bars, scour pits, dunes, and ripples. A vertical sequence reveals poorly defined tabular and trough cross-stratifications and horizontal stratifications. The upper bar facies appear similar to a longitudinal bar with superimposed ripples. A vertical sequence shows small scale (< 5 cm thick) or medium scale (5 to 15 cm thick) trough and tabular cross-stratifications, horizontal laminations, ripple-drift cross-laminations, and clay drapes. The chute bar facies is characterized by coalescing lobate bars with superimposed ripples. A vertical sequence displays large scale (> 15 cm thick) tabular cross-stratifications, small or medium-scale tr ugh cross-stratifications, ripple-drift cross-laminations, and clay drapes.

Evaluation of observed facies characteristics indicates that the distribution of bar facies and the development of vertical sedimentary profiles appear to be related to the degree of meander curvature. Further research is being initiated to construct a semiquantitative geomorphic and sedimentologic facies model useful to investigators of both modern and ancient fluvial systems.

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