--> ABSTRACT: Distribution and Textural Character of Surficial Sediments, Isles Dernieres to Ship Shoal Region, Louisiana, by Jeffress S. Williams, Shea Penland, and Ronald Circe; #91029 (2010)

Datapages, Inc.Print this page

Distribution and Textural Character of Surficial Sediments, Isles Dernieres to Ship Shoal Region, Louisiana

Jeffress S. Williams, Shea Penland, Ronald Circe

Since 1986, the U.S. Geological Survey and the Louisiana Geological Survey have undertaken field studies of the physical processes responsible for the widespread and extremely rapid coastal erosion of Louisiana's barriers along the Mississippi River delta plain coast. The study area encompasses the coastal and inner shelf region from Raccoon Point to Sandy Point and includes a database of 12-m long vibracores, surface grab samples, sidescan sonar, high resolution seismic reflection profiles, and precision hydrographic profiles.

This paper presents results in the coastal-shelf sector that includes the Isles Dernieres barrier island chain seaward almost 30 km to Ship Shoal. The surface and near-surface sediments of the region reflect fluvial and nearshore marine origin with pervasive evidence of winnowing and reworking by marine processes associated with frequent tropical storms and the passage of winter cold fronts. Beach sediments are remarkably uniform in grain size (fine quartz sand), except for the often abundant presence of carbonate shell debris, and are generally well to very well sorted. The shoreface and inner shelf are mantled with muddy sands and sandy muds, whereas, Ship Shoal is almost wholly fine quartz sand, similar in many sedimentologic respects to the Isles Dernieres. The results are consist nt with the model of coastal evolution, presented in 1988, in which Ship Shoal is the prototypical example of a drowned coastal barrier undergoing submarine reworking and landward migration in pace with the rapid rates of sea level rise and subsidence.

AAPG Search and Discovery Article #91029©1989 AAPG GCAGS and GC Section of SEPM Meeting, October 25-27, 1989, Corpus Christi, Texas.