The Portland Point Member of the Moscow Formation approximates a time plane that has been used to effect a correlation and environmental interpretation of the 100 to 150 feet of strata above and below the member. Proceeding from east to west the following environments are recognized: alluvial plain; marginal marine area comprising tidal flats, distributary channel complex, and interdistributary areas; nearshore shallow marine area; and an offshore region consisting of sandy and silty shelf. One small deltaic lobe is recognized. Strike lines drawn perpendicular to moving average paleocurrent vectors for the Middle Devonian of eastern New York show an undulatory surface, which is interpreted as being due to additional small lobate deltaic developments extending down the Catskill shoreline.

Sedimentary structures from the shelf area indicate paleocurrent directions both normal and parallel to the eastern shore as well as current reversals, all of which are thought to have been tidal in origin. The relationship between sandy and silty shelf areas is thought to have been controlled by a paleoslope to the south-southwest from the Adirondack high, and by depth changes associated with the Portland Point transgression.