Salem Limestone (Valmeyeran, Mississippian)—A high-energy carbonate shoal model

ABSTRACT The Salem Limestone (Valmeyeran, Mississippian) is a preeminent dimensional limestone quarried in a two-county area of south-central Indiana for nearly 200 years. Advances in quarry technology in the past 30 years produce nearly smooth-sawn quarry walls that show the exquisite depositional details of the Salem carbonate shoal. The Salem shoal is part of a large-scale shoaling sequence that produced a carbonate platform during the middle Mississippian that began at the end of Borden Group (Mississippian) delta deposition and culminated with the deposition of the Ste. Genevieve Limestone (Mississippian). The Salem was deposited as a high-energy, but subtidal shoal above fair-weather wave base. Four environments are recognizable within the shoal: active shoal, open lagoon, intrashoal channel, and intershoal channel. A shoal crest environment may also be present as a fifth environment. A hierarchy of bounding surfaces can be defined using the sawed quarry exposures. First-order surfaces are foreset laminae and appear as inclined or horizontal stratification. Second-order surfaces are the contacts between similar bedforms, and third-order surfaces truncate first- and second-order surfaces, representing breaks in sedimentation. Combined they define mesoforms within the shoal complex. Fourth-order surfaces, similar to third-order surfaces, represent a change from a shoal to lagoonal setting. Evidence of hard-ground development occurs along third-order surfaces, associated with encrusting bryozoan holdfasts, corals, and columnar subtidal stromatolites. Tracing surfaces on the quarry walls is vital to reconstructing the internal architecture of the shoal and the processes that operated within it. We will examine this shoal architecture by visiting quarries and an outcrop, and we will visit a mill where quarried stone blocks are fabricated into panels and shapes for buildings.