SPHERICAL MICROFOSSILS FROM THE TULLY FORMATION (GIVETIAN), LOCK HAVEN, PENNSYLVANIA

Pyritized spherical microfossils collected from the Middle Devonian (Givetian) Tully Formation in Lock Haven, Pennsylvania represent acritarchs, embryophyte spores, and possible invertebrate eggs. Specimens were obtained via an acid treatment process performed on samples of calcareous shale collected from the basal Tully Formation about 30 meters above its contact with the underlying Mahantango Formation. The spherical microfossils range in size from 200 µm to 250 µm and display a variety of characteristics. The objects we interpret as acritarchs possess regularly distributed, spine-like surface processes and a polar opening. The embryophyte spores are primarily trilete in form. The possible invertebrate eggs have four groupings of physical characteristics: 1) a simple, smooth surface; 2) a smooth surface with one or more collapse structures, i.e., surface infoldings; 3) a "tiled" surface consisting of adjoining, roughly hexagonal plates; and 4) a smooth outer layer with a textured inner region, which in at least some specimens is composed of a mosaic of pyrite rhombs. In addition, microscopic gastropods, pelecypods, cephalopods, ostracods, dacryoconarids, bryozoans, occasional conodonts, and burrows have been found in association with the spherical microfossils.