ABSTRACT

Work on a newly discovered late early Miocene vertebrate fossil site, in a paleochannel deposit in the upper Carnahan Bayou Member of the lower Fleming Formation, has revealed unexpected data on the course and nature of the Sabine River of that time. Screen washing for smaller vertebrate remains at the site, just west of the Sabine River in Newton County, central-eastern Texas, has resulted in the recovery of reworked early Permian, early Cretaceous, late Cretaceous (Maestrichtian), Paleocene/Eocene, late Eocene, and Oligocene/Miocene fossils, in addition to the main early Miocene fauna.

The evidence suggests that the Louisiana section of the present Red River pirated the Texas/Oklahoma/Arkansas boundary section of the river from the Sabine River, some time after the early Miocene.

Montmorillonite clay from altered volcanic ash may have made the river very turbid, which could have allowed coarse sand-sized fossils to be carried in the suspended load of the river, rather than in its bed load (where they would have been destroyed by the rolling chert gravel).

The Carnahan Bayou Member in Louisiana is here correlated to the Oakville Formation of Texas and the Siphonina davisi zone of the Texas/Louisiana subsurface.