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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 56 (1972)

Issue: 9. (September)

First Page: 1899

Last Page: 1899

Title: Nannoplankton Biostratigraphy and Sedimentary Petrology of a Vertical Facies Sequence Crossing the Campanian-Maestrichtian Boundary in Central Alabama: ABSTRACT

Author(s): N. C. Hester, J. B. Risatti

Article Type: Meeting abstract


On the basis of the occurrence of calcareous nannoplankton in Upper Cretaceous sediments, exposed in a series of road cuts near Pine Level, Alabama, the sequence is placed in the uppermost Kamptnerius magnificus zone, the Tetralithus aculeus zone, and the lower Chiastozygus initialis zone (Campanian-lower Maestrichtian). The Cusseta Sand lithology, which is considered to be of Campanian age in western Georgia and eastern Alabama, is shown to be basal Ripley or Maestrichtian at this locality, based on the occurrence of Chiastozygus initialis. This age difference suggests that the clastic wedge, building southeastward from central Georgia and represented by the Cusseta Sand in east and central Alabama, is time-transgressive as the unit progrades from east to west.

Although a Demopolis Chalk lithology (calcareous clay) appears above the basal Ripley Sand (Cusseta Sand), it is not Campanian as suggested by previous workers, but is instead lower Maestrichtian.

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

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

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