Middle and Upper Silurian carbonates in western Ohio and southeastern Michigan contain an extensive array of soft sediment deformation structures: concordant and discordant breccias, folds and faults, homogenized zones, sediment intrusions, and fault-graded beds formed by hydroplastic deformation, liquefaction, and fluidization. The variety of behaviors indicated by the range of deformational styles is a consequence of the varying degrees of cementation at the time of deformation. The unlithified nature of the sediments at the time of deformation, the type and large areal distribution of structures, and similarity to structures related to modern earthquakes indicate that the deformation is seismically induced. The source of the seismicity is believed to be nearby faults associated with the Grenville front which are known to have been active during deposition of Silurian strata.on April 4, 2015 specialpapers.gsapubs.org Downloaded from