Datapages, Inc.Print this page

ABSTRACT: Stratigraphic and Chronologic Framework for Fluvial Deposits of the Lower Nueces River, Corpus Christi, Texas


The Nueces River is one of several rivers that drain the Texas Gulf Coastal Plain. This research documents the stratigraphic framework and geochronology of alluvial units for the Nueces River, then links alluvial deposition to eustatic and climate controls.

Mapping and documentation of stratigraphic relations shows the Nueces valley exhibits a flight of three inset "Deweyville" terraces (high, middle, and low), with underlying alluvial deposits, as well as a younger alluvial fill, all within a distinct valley incised into Pleistocene Beaumont alluvial plains. Thermoluminescence (TL) ages from the different alluvial units help establish a geochronologic framework. TL ages of 91.7 +/- 7.9 and 71.9 +/- 6.1 ky were obtained from the youngest Beaumont alluvial plain strata, demonstrating they are isotope stage 5 or older. TL ages of 52.6 +/- 5.3 ky from the highest "Deweyville" unit, 40.3 +/-3.2 and 41.3 +/- 4.1 ky from the middle unit, and 35.6 +/-2.1 and 31.4 +/- 2.2 ky for the lowest unit show the entire "Deweyville" succession was deposited during isotope stage 3. The youngest component of the post-Beaumont fill has not been dated, but is probably Holocene in age.

Comparison between eustatic sea level curves and the above geochronological framework suggest sea-level was approximately 43, 48, and 58 meters below present during deposition of the high, middle, and low "Deweyville" units, respectively. This is consistent with longitudinal profiles that grade to positions well below modern sea level. All 3 "Deweyville" units were deposited during a very complex, longer-term eustatic fall, contrary to the concept that fluvial deposition occurs only during sea-level rise. Moreover, the morphology of preserved paleochannels and sedimentary facies within the different "Deweyville" units suggests that climate was an important control in valley-fill architecture.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana