VERTICAL DISTRIBUTION OF TRACE FOSSILS IN A TURBIDITE SEQUENCE, UPPER DEVONIAN, NEW-YORK STATE

Detailed study of quarry exposures of Rock Stream Formation (Upper Devonian) near Ithaca, New York, reveal three associations of trace fossils with a vertically consistent shale and turbidite sand lithology of proximal slope environment. A Paleodictyon association, similar to Seilacher's Nereites assemblage, is overlain in vertical section by members of Seilacher's Skolithos assemblage and facies-breaking forms. The Pteridichnites association is ubiquitous in distribution. Study of preserved physical and biogenic aspects of the environment suggest that the vertical change in the ichnogeneric assemblage is related to food resources and oxygen availability. Other factors usually limiting the distribution of trace-making organisms such as substrate consistency, texture, and energy regimes, were essentially the same throughout the paleoenvironment represented in vertical section. Stratigraphic studies show that marine regression was occurring in the shallower water paleoenvironments that were equivalent to rocks of this study. The non-sedimentological factors that accompanied the regression affect the proximal-slope areas before, and stratigraphically below, a change in sediment type recorded the regression. Organisms adapted to these inconspiciously different conditions left notably dissimilar traces in the preserved record. © 1979.