Abstract

Synsedimentary ball-and-pillow beds, breccias, and faults in late Middle to Late Ordovician foreland basin rocks of Kentucky, southwest Ohio, and Virginia indicate broad zones of seismicity near the Cincinnati arch and Taconic orogenic front during deposition. Earthquake-induced liquefaction formed seismites, that include ball-and-pillow beds and rare sedimentary breccias that are correlative over large areas (hundreds to thousands of square kilometers). Comparison of these features with liquefaction structures in Holocene sediments indicates that the Ordovician ball-and-pillow beds were probably generated by large earthquakes (magnitudes >6). The Ordovician seismites also provide information about epicenter location and the recurrence interval of large earthquakes in the Ordovician foreland basin. Some were produced by faulting in the foreland and accretionary prism. However, horizons of resedimented lithoclastic breccias in the Jeptha knob cryptoexplosive structure appear to correlate with several ball-and-pillow beds on Jessamine dome, along the Cincinnati arch, suggesting that some of the seismites may be genetically related to this enigmatic structure.

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