STRATIGRAPHIC INVESTIGATIONS INTO LATE GLACIAL AND HOLOCENE EVENTS, OAK OPENINGS REGION, NW OHIO

The Oak Openings Ridge (OOR) is a glacial lake strandline complex in the Erie Basin of northwest Ohio and southeast Michigan. Little is known about the depositional environments of the OOR or the stratigraphy at Blue Creek Metropark, located 1 to 1˝ miles southeast and lakeward of the OOR. Ground penetrating radar transects, vibracores, and hand auger samples were analyzed to begin understanding the stratigraphy and sequence of events in the OOR.

Sequentially above the Silurian limestone is till, a thin lag of coarse sand and fine gravel (<10 cm thick), laminated silty-clay with fine sands (rhythmites), and silty sand. Unconformably overlying the rhythmites in the middle of the valley is a fossiliferous mud overlain by laminated silt and sand, and grey organic-rich mud. Cores within these latter sediments recovered paleosols. The lag deposit over till is interpreted as a ravinement surface recording transgression of a glacial lake. The rhythmites were deposited from a moderately high lake level (possibly glacial Lake Warren and/or Wayne). Lowering of the glacial lake left nearshore sediments of silty sand and sand, some of which has been reworked by eolian processes. Wood within the fossiliferous mud was radiocarbon dated at 8820±40 (Beta-210382) indicating that incision of the Blue Creek valley had occurred by then. The shells, laminated silt and sand, buried paleosols, and organic-rich mud record more recent floodplain aggradation.