Mixed-layer illite-smectite and kaolinite are the most abundant clay minerals in five drill cores of Holocene and Pleistocene sediments from Mustang Island, Corpus Christi Bay area, Texas. The cores were bored from as deep as 60 m (197 ft) below sea level, and penetrated three depositional

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environments interpreted as being fluvial-deltaic (Pleistocene), estuary and lagoon, and a barrier island complex (both Holocene). The clay-mineral assemblages of the Corpus Christi Bay cores were compared to those from similar environments in Aransas Bay, adjacent to the north, and were found to be different.

In the Corpus Christi Bay area, the uniform distribution of clay-mineral species in the cores studied strongly suggests a more or less constant detrital source from the Nueces River over a period of approximately the last 35,000 yr. Available data on the clay mineralogy of sediments in the Nueces River drainage system, which flows into Corpus Christi Bay, indicate that kaolinite is the dominant clay mineral of lower Eocene sediments, and that montmorillonite is found in upper Eocene through Pleistocene sediments. We conclude that the clay-mineral assemblage found in cores in the Corpus Christi Bay is detrital, and that diagenetic clays are of minor significance.

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