Lithofacies And Paleoenvironments Of The Becraft Formation (Lower Devonian) Of New York State

Abstract

The Becraft Formation from the Lower Devonian of eastern New York is a crinoid-brachiopod calcarenite which represents a combination of regressive and transgressive lithologies. Three lithofacies are recognized within the Becraft: Facies 1, a shale and biomicrite interbedded with biosparite, deposited in a tran­sitional environment between an offshore zone of mud deposition and an above wave base shoal environment; Facies 2, a massive biosparrudite and biosparite, the prograding shoal, deposited at or above wave base; and Facies 3, a massive fine-grained biosparite, interpreted as reworked shoal sediment deposited during renewed transgression in late Becraft time. The Becraft shoal formed in the strait connecting the Helderberg and New England seas which first opened late in the Gedinnian. A new time-stratigraphy is developed for the Becraft. The turning point from a regressive to a transgressive sedimentary sequence interpreted from the distribution of gypidulids and changes in sedimentary texture is used as a time-datum for defining the new time-stratigraphic relationships.