Paper No. 5
Presentation Time: 3:10 PM
ARE THE RECENTLY REDEFINED DAYTON FORMATION (SILURIAN, LLANDOVERY, TELYCHIAN) AND DAYTON LIMESTONE OF ORTON, THE CELEBRATED BUILDING STONE OF OHIO, THE SAME FORMATION, OR IS A LIMESTONE BELOW THE DAYTON FORMATION AT JOHN BRYAN STATE PARK THE DAYTON LIMESTONE?
Orton (1870) recognized what he called the Dayton stone as the lowest unit, typically about 5 feet thick, sometimes containing pyrite, in the Niagara formation, immediately overlying the Clinton formation (now recognized as Brassfield) in Montgomery County, Ohio. The Dayton Formation was recently redefined (Brett et al. 2012) as a unit that lies above the Brassfield Formation and below the Osgood Formation in southwestern Ohio (eastern Montgomery and Greene counties). Cemex Quarry and John Bryan State Park (JBSP) were designated to serve as the revised type localities for the Dayton Formation since Orton (1870) didn’t designate a type section for the Dayton (Brett et al. 2012). Orton (1870) described the Dayton as a nearly pure carbonate of lime, and included an analysis by Dr. Locke in 1835 on Dayton stone from quarries in Dayton that showed it was a true limestone. Orton (1870) also asserted that with the exception of the lowermost beds of the Niagara formation, in those limited areas where the Dayton occurred, the Niagara formation in Ohio was a true magnesian limestone (dolostone). The Dayton Formation was described by Brett et al. (2012) as a white, thin-bedded dolomicrite, with pyrite throughout. There is a limestone unit approximately 5 feet thick, located above the Brassfield and below the Dayton Formation at JBSP. That unit is white, thin-bedded and fine-grained, with pyrite throughout. It compares favorably lithologically with samples of Dayton formerly used as building stones in Montgomery County. Conodonts from a sample from the upper part of the unit indicate a late Aeronian to early Telychian age, younger than the underlying early to middle Aeronian Brassfield and older than the middle to late Telychian Dayton Formation. The few samples of Dayton formerly used as building stones that have been processed yielded no diagnostic conodonts. Preliminary δ13Ccarb values for the unit are slightly lower than those of the underlying Brassfield and overlying Dayton Formation, but do not record the early Telychian Valgu Excursion. Additional data from samples currently being processed, and collecting and processing more samples of Dayton formerly used as building stone in Montgomery County and more samples from the limestone unit at JBSP, are required to determine a definitive answer to the question in the abstract title.