Field and petrologic study of the upper Helderberg Group has elucidated facies relationships. A "tongue" of the Kalkberg formation, recognized locally by Rickard (1962), at the top of the lower Helderberg cycle, extends southeastward to Catskill Creek where it thickens slightly, changes lithologic character, and passes laterally into the basal Becraft formation of the upper cycle. The Becraft represents a progradational phase within the general Lower Devonian transgression, and is seen as correlative with parts of both cycles. Thus, sedimentation was continuous between the two transgressive cycles. These revisions only slightly alter lower-cycle stratigraphy and preserve the integrity of Rickard's time lines.

The Becraft formation is divisible into three units. (1) (Base) High-angle, cross-stratified, crinoidal grainstones interbedded with shale, cross-laminated, silty, peloidal grainstones, and packstones. (2) Trough cross-stratified, gypidulid-bearing, crinoidal grainstones with rare channels. (3) (Top) Finer grained, bioturbated to vaguely laminated grainstones containing gypidulids, and in-situ, rootlike crinoid holdfasts, but less crinoidal debris. Units 1 and 2 represent progradation of a tidally influenced, skeletal-sand shoal over shoal-margin and deeper subtidal environments. Unit 3 is transitional to the superjacent Alsen formation.

The Alsen formation consists of irregularly bedded, bioturbated, skeletal, and peloidal grainstones. Bryozoans, brachiopods, and

End_Page 1167------------------------------

micritized skeletal debris are the dominant particles. Peloids are abundant in the middle of the formation. The Alsen represents slightly deeper water and less current activity than the equivalent upper Becraft.

Port Ewen lithologies include irregular and nodular, silty, skeletal wackestones and packstones, silty, peloidal packstones, and interbedded shale. Ostracodes, bryozoans, brachiopods, and micritized skeletal grains represent the sparse fauna. Bioturbation is ubiquitous; Chondrites, Planolites, and Zoophycos lebensspuren are common. The Port Ewen formation records the deepest, least-oxygenated environment in the Helderberg Group.

End_of_Article - Last_Page 1168------------