ABSTRACT

Beyond yielding signals of extinction or stressed ecological conditions, modern and ancient foraminiferal assemblages reflect specific marine depositional environments and depths. Foraminiferal predominance facies and benthic foraminiferal depth zonation has been successfully used to identify specific marine environments dating back to the Carboniferous. Using insights from modern equivalents, correlative assemblages allow for paleoecological analysis and insights. Middle to Late Devonian (Frasnian) black and gray shale beds of western New York contain hundreds of diminutive calcareous and agglutinated foraminifera. The genera within these beds are reminiscent of shallow modern predominance facies. These foraminiferal assemblages and their associated predominance facies correlate well with prior lithologic and geochemical investigations that establish this portion of the Appalachian Basin as a deltaic setting but suggest it is likely inner neritic zone. Dominant genera include several species of Ammobaculites and Saccammina which suggest that paleodepths did not exceed 50 m throughout the Frasnian. Opportunistic genera reflect a muted crisis associated with the punctata isotopic event (Rhinestreet Event) and Lower Kellwasser (Pipe Creek) events. While there are definite shifts in the diversity of assemblages between gray and black shale, the foraminiferal type and feeding mode, indicative of depth and oxygen availability respectively, there is little variation between the distinct shale units. No significance was found between total organic carbon and foraminiferal type of feeding mode. Identification at the species level is problematic but assemblages at the genus-level suggest that the depositional environment was stressed. However, the effects of these marine crisis events were not significant for these foraminifera in comparison to those frequently reported; we found no local extinction for foraminifera at least through the lower Hanover Shale, just prior to the Hangenberg marine crisis event, within this deltaic complex of the Appalachian Basin in western New York.

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