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RAVN, ROBERT L., AEon Biostratigraphic Services, Anchorage, AK, JULIE A. D'ABLAING, BP Exploration, Houston, TX

ABSTRACT: The Use of Nonmarine Palynomorphs as Correlation Tools in Rapidly Deposited Upper Tertiary Sediments of the Gulf of Mexico

Rapidly deposited upper Tertiary sediments can pose significant correlation problems for the biostratigrapher using foraminifera or calcareous nannoplankton, because the abundance of marine organisms commonly is greatly diluted. In contrast, such sediments often contain abundant pollen and spores. This palynological population was collected by the proto-Mississippi and perhaps other rivers from a huge hinterland source area probably comparable to that of the Mississippi drainage today. The sediment therefore reflects a general floral population over a large region, and may be expected to record important fluctuations in constituent elements of the flora due to climatic changes over time. A secondary overprint of physical sorting also may influence the relative distributions of certain forms.

Although not strongly useful as an age-dating tool (the vast majority of forms occurring in Miocene or younger strata represent parent plant types that still exist today), these palynomorph populations do show strong potential as tools for correlation based on quantitative analyses. Palynological "logs" can be produced using inexpensive standard spreadsheet software and various mathematical evaluation techniques. An example from the Pliocene of offshore Louisiana demonstrates that numerous potential correlation horizons can be defined in a relatively brief time interval in a section in which standard marine microfossils are of little use owing to their scarcity.

AAPG Search and Discovery Article #90989©1993 GCAGS and Gulf Coast SEPM 43rd Annual Meeting, Shreveport, Louisiana, October 20-22, 1993.