The Nueces Incised Valley Revisited: A Reinterpretation of the Sedimentology and Depositional Sequence Stratigraphy of Preserved Pleistocene and Holocene Valley-Fill Sediments
James R. Garrison, Jr., and Bobby McCoy
Texas A&M University – Corpus Christi, 6300 Ocean Dr., Corpus Christi, Texas 78412
Re-evaluation of seismic, core, well-log, and outcrop data from Corpus Christi and Nueces bays and surrounding area reveals sediments recording over 120,000 years of geologic history. Based on these data, progressive filling of the Nueces Incised Valley can be documented. The approximately 165 ft (50 m) thick valley-fill succession records the development of a simple tri-partite incised-valley stratigraphy. This incised valley serves as a modern analog for lowstand and transgressive systems tract deposits found within ancient incised valleys along micro-tidal shorelines.
The geometry and depositional fill of the incised valley records the sequence stratigraphic signature of the last glacial-interglacial cycle that represents events from the initial valley incision at about 24,000 years BP to the deposition of earliest high-gradient, lowstand, braided stream sediments to lower-gradient, late-lowstand, meandering fluvial sediments, followed by sediments recording the earliest transgression into the valley at the position of the present day shoreline, at about 10,000 years BP. This transgression eventually resulted in the formation of Corpus Christi and Nueces bays. The initial transgression was followed by deposition of retrogradational bayhead deltas, as the Nueces River mouth retreated. Early-transgressive systems tract estuarine deposits were subsequently overlain by central bay sediments, which are interlayered with scattered oyster reefs.
About 5600 years BP, a barrier system developed across the estuary separating the open Gulf of Mexico from the estuary’s interior. This barrier system, preserved at Indian Point and North Beach, separates Corpus Christi and Nueces bays. Except for a few passes, the estuary’s mouth was closed off from the open Gulf, at about 2500-2000 years BP, by the formation of Mustang Island.
AAPG Search and Discover Article #90069©2007 GCAGS 57th Annual Convention, Corpus Christi, Texas