SIRINGAN, FERNANDO P., and JOHN B. ANDERSON, Rice Univ., Department of Geology and Geophysics, Houston, TX

ABSTRACT: Occurence and Distribution of Storm Deposits on the East and Central Texas Continental Shelf

High-resolution seismic (3.5 kHz and boomer) profiles and sediment cores collected off the east Texas coast show the overall thinness of Holocene marine sediment cover on the continental shelf. Storm deposits on the lower shoreface and inner shelf are scarce, typically are very thin-bedded, and have a patchy distribution. On the inner to middle shelf, the storm deposits are amalgamated, forming sand banks with relief of as much as seven meters. They are associated with reworked coastal lithosomes. The sand banks coarsen upward, interfinger with marine mud on their landward side, and are underlain by ravinement surfaces. The abundance of cross-cutting channels on the shoreface, interpreted as storm return flow channels, is inconsistent with the scarcity of storm deposits on the modern ower shoreface and inner shelf. The channels reflect the high frequency of storms and hurricanes that have impacted the region during historical times. The paucity of storm deposits is attributed to strong along-shelf storm currents, low sediment supply, and low effective accommodation space below storm wave base.

In contrast to the east Texas shelf, the Holocene marine sediment cover of the central Texas shelf is thicker. Storm deposits on the lower shoreface and inner shelf are more abundant, thicker, and more laterally continuous. On the middle shelf, they are interbedded with mud. Thick amalgamated beds are absent. The high influx of fine-grained sediment into this region and greater effective accommodation space accounts for the higher preservation potential of storm deposits.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.