REINTERPRETATION OF THE “ANOMALOUS” C1 PORTION OF THE EDGECLIFF MEMBER OF THE ONONDAGA FORMATION AT CHERRY VALLEY, NY – AN EASTERN OUTLIER OF THE BOIS BLANC FORMATION

Oliver (1956, p. 1446) described the lowest beds (C1 facies) of the Edgecliff Member of the Onondaga Formation near Cherry Valley, NY as “markedly finer grained and somewhat darker than the typical Edgecliff.” Lindemann and Simmonds (1977, B9, p. 27) called these “phosphoritic based transitional beds” and Ver Straeten, et al. (2005, p. E45) described them as “anomalous, finer grained limestones.” All previous workers assigned these beds to the Edgecliff Member.

Oliver (1956) interpreted the C1 contact with the subjacent Carlisle Center Member of the Schoharie Formation as disconformable. The basal bed of C1 is a burrowed, glauconitic limestone with phosphatic pebbles and abundant well-rounded fine to very coarse grains of quartz sand (Springvale?). This condensed bed crops out near Cherry Valley on St. Butler Rd. (SBR) and along U.S. 20.

At SBR, 1.22 m of C1 overlie the condensed bed. C1 weathers with conspicuous recess below the much coarser crinoidal, coralline grainstones of the Edgecliff Member (Oliver’s C2). The C1 beds are composed of significantly finer skeletal grainstone dominated by echinoderm and trilobite debris, with fewer bryozoans and corals. Bioclasts in C1 coarsen upward.

The C1-C2 contact displays dm-scale erosional relief at SBR. The highest C1 bed exhibits silt filled vertical burrows and irregular cavities. Insoluble residue from this bed includes pyritized bioclasts, slightly glauconitic gastropod steinkerns, conodont fragments, and rare, well-rounded lithoclasts of siltstone, some with chertified fossils. Insoluble residue from the lowest bed of the overlying C2 Edgecliff contains abundant dacryoconarid steinkerns and rare, slightly glauconitic gastropod steinkerns, angular glauconitic grains and siltstone lithoclasts, possibly reworked from the top of C1.

Oliver (1956) interpreted C1 as a laterally and temporally equivalent facies of the coarser, more typical Edgecliff (C2). However, the C1-C2 contact is disconformable as indicated by the presence of erosional relief, exotic lithoclasts, glauconitic steinkerns and silt filled pockets and burrows. This disconformity and the lithologic and faunal differences from the typical Edgecliff strongly suggest that C1 is a separate stratigraphic unit. We interpret C1 at Cherry Valley as an eastern outlier of the Bois Blanc Formation.