The upper Santonian and lower Campanian succession in central Texas is described, and the upper part of the Austin Chalk is correlated along the outcrop between Austin and Waxahachie (250 km) using benthonic crinoids, oysters, ammonites and inoceramid bivalves. The contact between the Austin and the clays of the overlying Ozan Formation is a disconformity marked by an erosional surface and a thin phosphatic conglomerate. The lower Campanian Ozan clays have yielded ammonites which provide a correlation to the Western Interior Basin and the east coast Atlantic seaboard. An extensive and exceptionally preserved microcrinoid fauna from the lower Ozan is similar to that described from the chalk of southern England and includes a new species, Costatocrinus jeffcoatorum Gale, sp. nov. This microcrinoid fauna belongs to zone CaR6, indicating that the hiatus at the base of Campanian in central Texas is equivalent to the entire Offaster pilula and lower Gonioteuthis quadrata Zones of the UK succession, and probably represents over 2 million years. This disconformity is locally marked in Texas by the Waco Channel, a NNW-SSE trending, 70 km wide, and up to 200 m deep erosional structure extending from the Cretaceous shelf edge northwards to the Niobrara Seaway. The Lower Campanian displays significant hiatuses on a global scale, in the Atlantic, Southern Ocean and in northwest Europe.
- Santonian-Campanian correlation