SIGNIFICANCE OF MICROBIAL BINDING IN SILURIAN FOREREEF SLOPE DEPOSITS AT PIPE CREEK JR. QUARRY, INDIANA

Silurian forereef slope deposits exposed at Pipe Creek Jr. Quarry (IN) are characterized by steeply dipping beds (35-45^°) consisting of grainstone facies with abundant syndepositional abiotic marine cement. The early stabilization of steep carbonate slope deposits has been previously attributed to this syndepositional cementation. However, recent studies propose that extensive microbial binding can be another important factor. Therefore, the aim of this study is to evaluate the significance and timing of syndepositional marine cementation, such as abiotic and microbial binding, in the early stages of stabilization and lithification of these steep forereef slope deposits.

Initial petrographic analysis reveals an abundance of syndepositional abiotic marine cements with varying morphologies as well as microfabrics indicative of early microbial binding such as asymmetric micritic crusts, trapping and binding structures and dense clotted micritic masses. Further analysis and anticipated results will 1) identify if early microbial binding precedes abiotic marine cements and serves as a sediment stabilizing agent that provides a suitable substrate for later abiotic marine cementation, 2) help to explain the early lithification and evolution of carbonate slopes, 3) provide insight into possible circulation patterns and relative water depth during deposition and if microbial binding is controlled/affected by these factors, and 4) further develop the fundamentals of sedimentology and diagenesis of Silurian (Niagaran) reefs in and around the Michigan Basin which are significant hydrocarbon producers but where exploration and development are aimed towards the cores of the reefs rather than the associated forereef slope deposits.