RECOGNITION OF THE MULDE EVENT AND MULDE POSITIVE CARBON ISOTOPE (δ13Ccarb) EXCURSION (LATE WENLOCK; SILURIAN) IN THE NORTH AMERICAN MIDCONTINENT BASINS AND ARCHES REGION OF SOUTHERN LAURENTIA (INDIANA, OHIO, ONTARIO)

Conodont biostratigraphy and stable isotope chemostratigraphy make it possible to recognize the Mulde positive carbon isotope (δ ¹³C_carb) excursion in stratigraphic sections in the North American Midcontinent Basins and Arches region of southern Laurentia in Indiana, Ohio, and Ontario. The Mulde Excursion is recorded in the Waldron Formation in Indiana, the Greenfield Formation in Ohio, and the Guelph Formation in Ontario. None of the seven sections that are a part of this study contain a complete record of the dual-peaked excursion. The most complete record of the Mulde Excursion in the seven studied sections is in the outcrop section at Anderson Falls, Indiana, in which the ascending limb and both peaks are represented in the Waldron, with only the descending limb absent due to an unconformity at the top of the Waldron. The Mulde Excursion is less complete in the Guelph core from Ontario, with the ascending limb and possibly part of the first peak absent due to the lower limit of the core. The Mulde Excursion is preserved as either an incomplete peak or descending limb in all of the Ohio sections. None of the seven studied sections preserves a faunal record of the Mulde Event comparable to its type area in Gotland, in which three conodont datum levels are recognized. In fact, it is not possible to definitively recognize the Mulde Event in any of the seven sections, as there are no conodont species present below the level of the onset of the Mulde Excursion that are not also present within or above the level of the Mulde Excursion in those sections. Previous studies in other areas of southern Laurentia (Oklahoma, Texas, Tennessee) were able to recognize the Mulde Event in some sections, where it was confined to a single horizon. Neither Ozarkodina sagitta sagitta, nor Pseudooneotodus linguicornis, conodonts with last appearances considered to indicate the beginning of the Mulde Event, were recovered in any of the sections studied in Indiana, Ohio, and Ontario. Ozarkodina bohemica longa first appears in the Greenfield in beds recording the descending limb of the Mulde Excursion in two quarries in Ohio, the same level at which it was reported to first appear in other areas of southern Laurentia in previous studies.