GSA Connects 2021 in Portland, Oregon

Paper No. 202-10
Presentation Time: 10:40 AM


RICHARDSON, Harrison, Missouri State University, 6014 Alamito St, San Angelo, TX 76904, MCKAY, Matthew, Geology Department, Missouri State University, 901 S National Ave, Springfield, MO 65897-0027, FRANK, Kelly, Department of Geology, Geography & Planning, Missouri State University, 901 S National Ave, Springfield, MO 65897 and JACKSON Jr., William, Department of Earth Sciences, University of Memphis, Memphis, TN 38152

Within the Ozark plateau there is evidence for long-lived tectonism, which could have potential to explain plate margin processes by providing evidence to resolve continental platforms. In southern Missouri, Ordovician carbonate strata host injected clastic dikes originating from interbedded sandstone units. Because of the spatial relationship to a major basement structural boundary, the planar nature of the paleoseismites, and pervasive carbonate deposit suggesting low sedimentation rates, we interpret clastic dikes as paleoseismites. Clastic dikes are exclusively located within 1 km of mapped faults that offset Mississippian strata, suggesting a spatial link between Ordovician seismicity and subsequent Mississippian or later faulting. To investigate this link, we present structural and sedimentological data, including, outcrop scale surveys, joint and clastic dike orientation data, as well as regional gravity maps to investigate paleoseismites in dominantly carbonate Ordovician strata near Mississippian or later faults. Paleoseismites are oriented orthogonally N-S and E-W, which parallels regional joint patterns. Ordovician siesmites are present near lithospheric-scale boundaries, observed in regional gravity maps, suggesting basement faults at depth. These basement faults are likely pre-Mississippian and oriented E-W parallel and orthogonal to paleoseismites and associated joint orientations. We interpret paleoseismites to reflect Ordovician basement fault displacement in response to distal tectonism from the Taconic orogeny to the east; or reactivation of these basement faults following deposition of Mississippian strata during the Ouachita orogeny would account for the presence of later normal faulting of overlying strata.