During the Early Ordovician, detritus eroded from the anscestral Adirondack Mountains was deposited in eastern New York on a shallow shelf as a broad complex of strandline sand bars, shoal-flat channels, and sand-mud flats. Sedimentological studies of this sequence (Winchell Creek Member of Great Meadows Fm.--Lower Ordovician) suggest sediment accumulation in the intertidal zone, and thus offers evidence of tidal sedimentation along the eastern margin of the epicontinental sea, adjacent to the shelf edge in New York. Analysis of paleocurrent data from these rocks indicates that the dominant flood and ebb tidal currents active in this area were from the east and west, respectively, and support the interpretation of a major shelf-to-basin transition (paleoslope) to the east into a proto-Atlantic ocean. This shelf region appears to have been part of the postulated contiguous shelf, peripheral to the proto-Atlantic, that existed from the Late Precambrian to Early Paleozoic. Similarity of sedimentary sequences and depositional events is recognized along the length of this shelf in diverse localities in the North Atlantic.