Conodonts from the Everton Dolomite and the St. Peter Sandstone (Loser Middle Ordovician) in a Core from Southwestern Indiana

Abstract

"Conodonts have been recovered from samples of the Everton Dolomite and of the unconformably overlying St. Peter Sandstone from the General Electric Waste Disposal No. 2 core in Posey County, southwestern Indiana. The faunules are reported here because one documents the Everton age of rocks that in Indiana had been assigned to the Knox Dolomite and the other is the first description of indigenous conodonts from the St. Peter Sandstone.

Subsurface information was not adequate in Indiana until recently for the certain recognition of the Everton Dolomite on a lithologic basis with supporting evidence from conodonts. The Everton conodonts are dominated by Paraprinoniodus costatus (Mound), and Leptochirognathus quadratus Branson & Mehl is next in abundance. Both are abundant components of the outcropping Everton fauna in Arkansas and Missouri. The St. Peter Sandstone is in facies relationship eastward in Indiana with two carbonate units, the Dutchtown Formation and the overlying Joachim Dolomite. The thin sandy dolomite lenses in the lower part of the St. Peter in Posey County contain a faunule that is fairly abundant but is low in diversity. Multioistodus subdentatus Cullison comprises more than 90 percent of the conodonts. The sampled part of the St. Peter correlates with part of the Dutchtown Formation of Missouri."