SEDIMENTOLOGICAL INVESTIGATION OF THE TRENTON LIMESTONE AND POINT PLEASANT FORMATION FROM ROCK CORE SAMPLES FROM THE KIKO-1 WELL IN STARK COUNTY, OHIO

The Trenton Limestone and Point Pleasant Formation of northeastern Ohio were deposited in marine environments in the Appalachian Basin during Late Ordovician time. Earlier studies analyzing the geophysical log signatures of the stratigraphic interval have suggested that these units were deposited along the southern margin of the Sebree Trough, a NE-SW trending zone of deeper marine water separating the Lexington Platform to the south from the Galena Shelf to the north. To affirm these assessments, we evaluated the lithologies and sedimentological features of the Trenton Limestone and Point Pleasant Formation from the rock core samples from the Kiko-1 well in Stark County, Ohio. The core contains limestone and mudstone spanning the stratigraphic contact between the two units. The core was carefully documented at centimeter-scale intervals to capture detailed stratigraphic variations. Sedimentological changes were noted, with the core primarily consisting of limestone interbedded with dark grey/black carbonate mudstone. The limestones are carbonate grainstones, composed of sand- and gravel-sized fragments of brachiopods, bryozoans, crinoids, and trilobites. Grainstone beds are structureless to horizontally stratified with bases that commonly contain mud rip-up clasts and convolute laminations. Rare hummocky cross-stratification is also present. Observable sedimentological features in these carbonates suggest periodic deposition by low-density sediment gravity flows (i.e. turbidity currents) mostly below storm wavebase. Carbonate mudstones consist of clay-sized carbonate with subordinate percentages of laminated carbonate/siliciclastic silt and siliciclastic clay. While the organic-rich black mudstones points to relatively deepwater anoxic environments, the ubiquitous presence of laminated silt-size material suggests mudstone-dominated intervals were influenced by distal turbidity-current deposition. Collectively, these characteristics observed in the core support interpretations of a depositional setting along the boundary of the Sebree Trough. Results of this investigation provide improved sedimentological constraints and local stratigraphic framework of the Trenton Limestone and Point Pleasant Formation in northeastern Ohio.