A STUDY OF REDEPOSITED CONODONTS FROM POLYMICT BRECCIA IN THE DECATURVILLE STRUCTURE, MISSOURI, USA

The Decaturville structure is a confirmed, 6-km-diameter, impact structure located in central Missouri between the towns of Camdenton and Lebanon. The time of structuring has not been resolved with certainty. The purpose of this study is to determine the chronostratigraphic range of conodonts that occur in polymict breccia of the ring-graben and establish a time before which structuring could not have occurred. This information would facilitate reconstruction of the post-Ordovician Ibexian lithostratigraphic column removed by erosion in the area after structuring. Towards this end, at least 30 kilograms of polymict breccia will be processed for the recovery of conodonts. The breccia will be digested in a buffered formic acid solution for at least three weeks to maximize dissolution of limestone and dolomite clasts. Shale residues from the acid digestion will be processed to recover additional conodonts. Conodonts will be identified. This study is an extension of a pilot study the Missouri Geological Survey did in 2011 that recovered conodonts tentatively identified as Silurian. It is possible that younger conodonts are present in the polymict breccia.