Vladimir I. Davydov¹
(1) Permian Research Institute, Boise State University & VSEGEI, Boise, ID

Abstract: Testing the Sequence Stratigraphic Model: Response of Fusulinacean Fauna to Sea Level Fluctuations (Examples from Pennsylvanian and Cisuralian of Pricaspian-southern Urals [PU] Region)

The PU region is paleogeographically situated between the Boreal and Tethyan provinces and includes comprises taxa of both affinities. Both sedimentologic analyses and Graphic Correlation (GC) technique were employed to clarify the Pennsylvanian-Cisuralian sequence stratigraphic framework in the PU. Fusulinacean zones were utilized for the region based on a well established evolutionary framework. Benthic fusulinaceans lived near shore, within the photic zone, and were a sensitive indicator of paleoenvironmental changes. Species occurrence in any given section or region may reflect local/regional environmental factors. However, the origination and extinction of fusulinacean species are generally influenced to a greater degree by global rather than by local forces (global climatic vs local tectonic or/and enviromental changes). The study of phylogenetic successions combined with GC were used to distinguish between locally controlled initial occurrences and true speciation. The PU fusulinid zonation is based on phylogenies, it thus reflects true speciation and extinction events. In PU region some sequence boundaries coincide with the bases of fusulinid zones. We can suggest that these sequences are eustatic. Sequence boundaries located within fusulinid zones, perhaps reflect local tectonism or local climatic changes. However, the base of some fusulinid zones coincide with highstands, therefore fusulinid speciation appears to be associated with both highstands and lowstands. Sea level lowstands have been very stressful for global fusulinid assemblages and may have been a catalyst for both speciation and extinction. Highstands also may have created environmental opportunities and appear to be more closely associated with fusulinid speciation than extinction.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana