Correlation of Marine Sediments from the Texas-Louisiana Continental Shelf

By

DUNN, DEAN A.

University of Southern Mississippi, Hattiesburg, MS,

STOKES, TRACI L.

U.S. Naval Oceanographic Office, Stennis Space Center, MS

Analysis of 212 samples taken from 23 gravity cores obtained on the Texas-Louisiana continental shelf allows delineation of the geographic distribution of sediment types and provinces based on sedimentary parameters.

In the southwestern part of the study area, closest to Corpus Christi, nearshore sediments are a mixture of sand-silt-clay and silty clay (using the ternary classification of Shepard, 1954), with clay percentages increasing farther from shore. The deeper-water clays have the lowest sound velocities (1413-1519 m/s), lowest dry densities (2.61-2.65 g/cm³), highest porosities (70-80%), and slightly higher calcium carbonate contents (0-5% to 5-10%) than nearshore sediments and samples from the northeastern part of the study area.

The sediments in the northeastern part of the study area, off east Texas and southwest Louisiana, are dominantly composed of sand-silt-clay and clayey sand, with a mean grain size of silt. The cores in this area have the highest sound velocities (1526-1704 m/s), highest dry densities (2.66-2.74 g/cm³), lowest porosities (36-67%), and generally lower calcium carbonate content (0-5%) than cores in the southwestern shelf.

A linear correlation exists between acoustic and certain physical properties: an increase in mean grain size (smaller phi numbers), decreased clay content, and lower porosity produces an increase in sound velocity. Sand content and bulk grain density increase as sound velocity increases. No correlation was found between calcium carbonate content and sound velocity.