Abstract: Onondaga Pinnacle Reefs in New York State

Gerald M. Friedman

Onondaga pinnacle reefs, part of the Onondaga Formation, developed in an epeiric setting of the lowermost Middle Devonian (Eifelian). The reefs were initiated as coral-crinoidal mounds in the Edgecliff Member of the formation.

Whereas most Devonian reefs are built of stromatoporoids, the framework builders of the Onondaga reefs are composed of rugose corals. Coral is the predominant kind of fossil, followed by crinoids, brachiopods, mollusks, undifferentiated skeletal debris, and possible sponges. The initial mineralogy of the corals is inferred to have been calcite. The porosity of these reefs is almost unique among reef reservoirs. most reefs produce from secondary or diagenetic porosity; by contrast Onondaga reefs display primary intracoralline or framework porosity. Between framework builders and/or skeletal particles cryptocrystalline/microcrystalline cement fills pores. As observed in modem reefs this kind of cement resembles micrite, but probably formed as high-magnesian calcite in a high-energy sett ng. Syntaxial or rim cement common lines crinoid particles.

Some of these pinnacle reefs, formerly gas producers, are presently under development as gas-storage reservoirs.

AAPG Search and Discovery Article #90954©1995 AAPG Eastern Section, Schenectady, New York