General remarks on the pre-Selma Cretaceous strata of western Alabama

Abstract

The Vick formation, previously known in only one small outcrop area, has now been identified in the shallow subsurface. Evidence in this series of papers points to a nonmarine environment for the Vick and mainly a shallow and commonly brackish-water marine environment for the overlying Tuscaloosa group and the McShan and Eutaw formations. The distribution of gravel in several formations suggests that the Tennessee and Sequatchie Rivers flowed into the Cahaba and Warrior Rivers during Cretaceous time. EXTENT AND THICKNESS OF THE VICK FORMATION The preceding papers have supplied many facts regarding the thickness, petrology, paleontology, and conditions of accumulation of the pre-Selma Cretaceous strata of western Alabama; they have confirmed some theories that evolved during the surface mapping from 1944 to 1948; and they have supplied new information. Here an attempt is made to synthesize some of the newly acquired subsurface information with knowledge previously obtained, some of it not heretofore published. The Vick formation has been entirely unknown beyond its !-squaremile outcrop area (fig. 1; Conant, 1946), and its suggested Early Cretaceous age has never been satisfactorily established. The presence in the Webb hole of at least 104 feet of beds that seem to be of the same unit indicates that the Vick is present at least 15 miles downdip, or southwest, from the outcrop area. This supports the original concept that the few outcrops of the Vick formation represent a subsurface unit that is almost completely overlapped by the beds of the Tuscaloosa group. The exact age of the Vick, however, is still not established, though Monroe reports fossil leaves of probable Cretaceous age, and also points out the similarity between some of the core samples and the Lower Cretaceous beds of the deeper subsurface. It is only fair to note, however, that some geologists who have studied