Mid-Tertiary Volcanism in the Gulf of Mexico Coastal Plains with an Analysis of the Catahoula Formation as a Volcanic Terrane
Del Rio, Texas
Volcaniclastics of the Catahoula Formation are believed now, and in the past, to be a product of exclusive exogenic processes, principally fluvial in nature. Regardless of their Eocene to Miocene age, their origin is attributed to the Trans-Pecos and/or the Sierra Madre Occidental, both far distant volcanic provenances. Such derivation is considered by earlier workers to be irrespective of particle size, rock type, variety, geographic range, or thickness of deposition up to a 1,000 feet thick.
However, Bailey's long forgotten 1924 hypothesis that the Catahoula Formation is a consequence of local volcanism and thus constitutes a volcanic terrane rather than a sedimentary formation needs to be revisited. In 1977 a massive igneous intrusion was discovered subjacent to Catahoula volcaniclastics in Live Oak and McMullen Counties where surface remains of tuff rings have been identified, thus providing conclusive evidence of past endogenic forces in the region. The igneous intrusion may likewise be the heat source for the adjacent Wilcox geothermal corridor. Subsequent circulation of hydrothermal fluids accompanying hydrovolcanism provides a plausible explanation for the origin of the uranium deposits. The breaching of the basement rock is suggested to have been along the hinge line of variably thick transitional crust in close proximity to the Stuart City Trend and coeval in time with proposed plate movements to the west and northwest.
Rejection of a valid scientific hypothesis, as presented by Bailey, coupled with the non-recognition of the rules of parsimony (Occam's razor) customarily employed in scientific expositions, has obscured an understanding of the geology of the Gulf Coastal Plain. If the Catahoula volcaniclastics are other than local in origin one must ask--what is the geological evidence?
AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004