Recognition of Buried Silurian Reefs in Southwestern Indiana: Application to the Terre Haute Bank

In Indiana the buried Terre Haute Bank extends from the west-central part of the state to the south-central part. It consists of Silurian carbonate rocks several hundreds of feet thick that are dominated by dolomitized reef-derived sediments. More than 100 discrete reef bodies are recognized along what was a broad structural hinge line peripheral to the proto-Illinois Basin. At least two reef generations arose during Middle and Middle-to-Late Silurian time. The reefs, therefore, collectively have Silurian and Devonian (Lower or Middle) covers. Because deep drilling is sparse and limited seismic surveys in the bank area are confidential, mostly indirect evidence must be used for reel interpretation, consisting especially of structural deformation (broad sense) of the rocks encasing the reefs and composing the reef flanks. This deformation was a long-term process that affected even the youngest Paleozoic rocks preserved in this area, and it possibly continued to the present. Diagenesis, including differenti...