ABSTRACT

On the basis of the occurrence of calcareous nannoplankton, an Upper Cretaceous sequence exposed in a series of road cuts near Pine Level, Alabama, is placed in the Tetralithus aculeus Zone and the Chiastozygus initialis Zone (Campanian-lower part of Maestrichtian). The Cusseta Sand, which is considered to be Campanian in age in western Georgia and eastern Alabama, is shown to be Ripley or Maestrichtian in age at this locality on the basis of the occurrence of Chiastozygus initialis (Gorka). This difference in age suggests that the clastic wedge building southwestward from central Georgia and represented by the Cusseta Sand in east and central Alabama transgressed time as this unit prograded from east to west.

Although Demopolis Chalk (calcareous clay) appears above the basal Cusseta Sand, it is not Campanian in age as suggested by previous workers but belongs instead to the lower part of the Maestrichtian.

Through the use of planktonic-benthonic foraminiferal ratios, textural analyses, clay mineral ratios, and stratigraphic and biogenic structures, the following five sedimentary enviornments, from bottom to top in vertical sequence, were recognized: 1) "delta front silts and sands" (regressive), (2) "offshore clays" (transgressive), (3) "marginal shelf sands" (regressive), (4) "offshore clays" (transgressive), and (5) "barrier bar-shoal sand complex" (regressive).

The gradational boundaries between the various facies produced by a fluctuating strand demonstrate that there is no major break in the sedimentary record at the Campanian-Maestrichtian boundary.