Abstract

The Delphi Station Member of the Hamilton Group in central New York was deposited during an interval of falling sealevel. Seventy samples were collected from a 24 metre section. Multivariate cluster and ordination analyses of lithologic and faunal content aid in defining communities. The oldest sediments consist of dark grey shales that formed in quiet water at moderate depth and were populated by the Nuculoidea community. Abundant organic detritus and micro-organisms provided food for nearly 40 percent of deposit feeders, mostly infaunal nuculoids, and collectors. Bottom dwelling filter-feeders account for roughly half of the fauna. These include small chonetids, endobyssate bivalves and pedunculate brachiopods that were adapted to soft substrates. The waters shoaled and agitation increased throughout deposition. Eventually the area was covered with siltstones and sandstones that were inhabited by the Actinopteria community. Filter-feeders, especially byssate bivalves, reclining and pedicle-attached brachiopods comprise 85 percent of the fauna. Deposit feeders were rare because of the scarcity of organic matter.