INTEGRATED HIGH-RESOLUTION CONODONT BIOSTRATIGRAPHY AND CARBON ISOTOPE PAIRED WITH MAGNETIC SUSCEPTIBILITY OF THE MISSISSIPPIAN KINDERHOOKIAN-OSAGEAN BOUNDARY FROM JANE, MISSOURI, USA

The early Mississippian is a time of measurable dynamic chemical, eustatic, and biotic change. The North American Kinderhookian-Osagean boundary (KOB) has been correlated to one of the largest positive isotope excursions in the Paleozoic (Kinderhook-Osage boundary isotope excursion), a eustatic lowering due to increased glaciation across the D-C boundary, and significant biotic marine turnover including but not limited to Gnathodus and Siphonodella conodont species. The stratigraphic relationship of the position of the KOB in the Tournaisian has not yet been established. The KOB is reported as a global sequence boundary; however, near the stratigraphic type locality (central Missouri) a large unconformity is present with both G. punctatus and S. isosticha missing. Outcrops near Jane, MO, where stratigraphy becomes more continuous, serve as the master section for the integration of high-resolution conodont occurrences including FAD and LAD positions and carbon isotopic analysis. These are paired with magnetic susceptibility (MS) that serve as a proxy to eustatic sea level and as an additional new global correlative tie. This integrated study provides insight to zones or levels of conodont biotic events that align with the onset, peak, or return to normal in the isotopic curve, and shifts in sea level trends derived from the MS thus mark the maximal correlation for the KOB in the Midcontinent to apply to global correlation.

Additionally, this study expands on geometric morphometric analyses that assess proposed 'advanced' vs 'primitive' morphotypes of G. punctatus from NM, OK, and MO. The FAD of the ‘advanced’ morphotype is proposed to correlate to the base of the Osage. Both ‘primitive’ and ‘advanced’ forms occur in the G. punctatus biologic type area in OK with a dominance shift of ‘primitive’ in the older Pre-Welden to ‘advanced’ in the younger Welden Lm. Preliminarily this shift is seen within populations from NM and MO. Expanding the dataset of 234 adult specimens containing Pre-Welden (10 total) and Welden Limestone, OK (167 total), NM (40 total), and MO (17 total) to include larger and balanced populations reduces the current sample bias and will validate our preliminary observations, thus identification of a new regional biostratigraphically significant zone that could align with other chemical or eustatic trends to best correlate the KOB regionally and globally.