CONODONT BIOSTRATIGRAPHY AND 13C CHEMOSTRATIGRAPHY OF THE SALINA GROUP IN NORTH AMERICAN MIDWESTERN BASINS AND ARCHES REGION (WESTERN OHIO AND EASTERN INDIANA)

Salina Group strata present in quarries, along a stream, and in a core at three localities in west-central Ohio and east-central Indiana on the Findlay and Cincinnati Arches and Salina Group strata in a core drilled in northeastern Indiana on the distal margin of the Michigan Basin were sampled and processed for conodonts and δ¹³C_carb isotope values. Elements of Pseudooneotodus linguicornis were recovered from Cedarville Dolomite/Greenfield Dolomite transitional strata in the Con Ag Quarry in St. Marys, Ohio, at the same level as the onset of a positive δ¹³C_carb excursion. Pseudooneotodus linguicornis became extinct at Datum 1.5 of the Mulde Event in Gotland, near the level of the onset of the Mulde Excursion. Datum 1.5 of the Mulde Event and the Mulde Excursion both indicate a middle to late Homerian (Wenlock) age for the Greenfield. The Waldron Formation exposed in Clifty Creek at Anderson Falls, Indiana, yielded no conodonts, but did record a positive δ¹³C_carb excursion with two peaks, recognized as the Mulde Excursion. Salina Group undifferentiated strata at the Duff Quarry in Huntsville, Ohio, yielded Pa elements of species with Ozarkodina confluens affinity comparable to those of species recognized to have ranges restricted to the Ludlow or Pridoli. No δ¹³C_carb excursion is recorded in those strata; most δ¹³C_carb values are between -1.00‰ and 0.00‰. A core from Steuben County in northeastern Indiana records a dual-peaked positive δ¹³C_carb excursion through a considerable thickness of Salina Group strata. The excursion is recognized as the Mulde Excursion, because elements of O. bohemica longa and K. stauros were recovered near the level of the first peak of the excursion. The lowest occurrence of anhydrite/gypsum is also in that portion of the core, possibly indicating a level equivalent to the A carbonate of the Michigan Basin. One sample from more than 30 m above the end of the Mulde Excursion had a δ¹³C_carb value (+2.63‰) more than 2‰ higher than δ¹³C_carb values in both the subjacent (+0.32‰) and suprajacent (+0.36‰) samples, possibly representing a positive δ¹³C_carb excursion greatly truncated by erosion (Lau Excursion? of Ludfordian age). Elements of O. snajdri were recovered from a sample 31.7 m higher in the core and provide a definitive Ludfordian (Ludlow) age for that portion of the core.