GOLDEN BRASSFIELD OF THE NORTH AMERICA MIDWESTERN BASINS AND ARCHES (NAMBA) REGION (INDIANA AND KENTUCKY): ALL IS NOT GOLDEN ACCORDING TO CONODONT BIOSTRATIGRAPHY AND δ13CCARB CHEMOSTRATIGRAPHY

Golden Brassfield is an informal designation for the golden-colored unit disconformably overlying Ordovician strata in southeastern Indiana and north-central Kentucky (NAMBA). The golden Brassfield exposed in a quarry in Batesville, Indiana, overlies a karstic surface of Ordovician strata, including scattered mounds, interpreted as sea stacks. At locations in the quarry where the formation overlies sea stacks, it is within the middle Aeronian Pranognathus tenuis Zone. At locations lacking sea stacks, the golden Brassfield is thickest (3.0+ meters), and all but the uppermost portion is within the Pr. tenuis Zone. The uppermost portion is within either the late Aeronian-early Telychian Distomodus staurognathoides Zone or early Telychian Pterospathodus eopennatus Superzone. Throughout the quarry, the golden Brassfield is unconformably overlain by thin fossiliferous limestone beds that are within the late Telychian Pt. a. amorphognathoides Zone. δ13Ccarb values in the golden Brassfield vary between +1.30‰ to +2.40‰, typically less than +1.7‰ in the lower third and greater than +1.90‰ in most of the rest of the formation. δ13Ccarb values in the uppermost 0.3 meters are typically less than +1.8‰. The thin limestone beds overlying the golden Brassfield yielded δ13Ccarb values greater than +2.20‰. Golden Brassfield exposed in outcrops in Crestwood and Mt. Washington, Kentucky, also overlies a karstic surface of Ordovician strata. The thickness at both sampled localities was approximately 0.65 meters. The entire formation at both localities is within the early Telychian Pt. eopennatus Superzone. At both localities, the beds overlying the golden Brassfield are within the late Telychian Pt. a. amorphognathoides Zone. δ13Ccarb values for the entire golden Brassfield at both localities are remarkably consistent (between +0.20‰ to +0.60‰). δ13Ccarb values in the beds overlying the golden Brassfield at both localities range from +1.20‰ to +2.1‰. The golden Brassfield of north-central Kentucky is likely correlative with the uppermost portion of the golden Brassfield of southeastern Indiana. Both also correlate with the Lee Creek Formation of Indiana and Waco Formation of Kentucky, and are stratigraphically distinct from most of the formation recognized as golden Brassfield in Indiana.