The Nueces Bay-Head Delta Response To The 2.6 ka Climate Event In The Northwestern Gulf Of Mexico

Abstract

The purpose of this study is to examine how a wave-dominated estuary responded to a period of aridity that occurred around 2.6 ka. Additionally, the overall evolution of the bayhead delta is better defined through a sub-delta facies model. Twenty-eight vibracores, eight geoprobe cores, and twenty-five kilometers of high-resolution seismic profiles were collected in the Nueces Bayhead Delta on the northwest coast of the Gulf of Mexico in Texas. The sediment cores were described and used in conjunction with the seismic profile to determine lateral facies relationships. The timing of deposition and facies changes were determined by radiocarbon dating. We identified eight sedimentary facies in the sediment cores which include five distinct deltaic sub-facies. The sedimentary facies include two distinct mud facies, two distinct sand facies, an oyster facies, tan sandy silt facies, a brown fine sand facies, and a black sandy silt facies. Within the 25 kilometers of seismic data, we identified four seismic facies. The seismic facies were identified based observed reflection characteristics. Seven sand lobes were identified in the seismic profiles and sediment cores. The seven sand lobes have been interpreted as mouth-bar deposits and used to determine the approximate location of the seaward edge of the delta through time. The delta was located farther seaward than its current location prior to 3 ka. After 3 ka the delta backstepped by at least 10 kilometers before prograding to its modern position. The post-3 ka backstepping event correlates with a period of local aridity and was probably caused by a reduction in sediment supply.

AAPG Datapages/Search and Discovery Article #90215 © 2015 Pacific Section AAPG Convention, Oxnard, California, May 3-6, 2015