About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 11 (1961), Pages 121-137

Point-Bar Deposits, Old River Locksite, Louisiana

D. E. Frazier, A. Osanik (1)

ABSTRACT

A large excavation for a navigation lock, dug in a now-abandoned and partly filled meander loop of the Mississippi River along Old River, exposed around its base a 40-foot vertical section of point-bar sands that had been deposited below mean low-water stage. Data from U. S. Army Corps of Engineers borings made it possible to determine limits of this bar sand and its relationship to enclosing alluvial deposits. The exposed bar deposit is a lithic arenite and is composed of well-sorted medium to fine-grained sands incorporating thin layers of pebbles, macerated plant debris, and sparse heavy-mineral concentrations. Armored mudballs are present in the upper portion of the exposed section; wood fragments are common throughout. The entire exposed section is characterized by festoon crossbedding--the only type of bedding present. The festoon crossbeds formed in response to penecontemporaneous scour-and-fill processes accompanying downstream migration of sand Previous HitwavesTop during bar deposition. History of river development in this area is well known; it was therefore possible to relate measured directional properties of the sand deposits to current directions of the river at the time of deposition; the average dip direction for the crossbeds was S. 40° E., in close agreement with local channel alignment--S. 45° E. Preferred grain orientation was S. 26° E.


Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24