Archaeology Lecture Series “Serpent Mound Impact Structure”
with Mark T. Baranoski, retired geologist
The Serpent Mound Impact Structure is located west of the Appalachian escarpment in southern Ohio near the intersection of Adams, Highland and Pike Counties. It is roughly an 8 km (5 mile) diameter circular geologic feature when viewed with satellite imagery. On the ground it is one of the more complex folded/faulted geologic structures in the region, consisting of a central uplifted peak, surrounded by a transition zone and an outer ring graben. The deformed Paleozoic Era rocks at the surface range in age from Ordovician to Mississippian Systems. The structure has been studied since first discovered in the 1830s by John Locke, who called the area “Sunken Mountain”. Walter Bucher renamed it the Serpent Mound cryptovolcanic structure in the 1920s after the serpentine effigy mound located within the transitional zone. Steve Reidel renamed the feature the Serpent Mound disturbance in 1982. The origin of the structure remained controversial between two groups for many years: either formed by deep seated endogenic “cryptovolcanic” forces, or an impact from a meteorite or comet. An impact crater origin was confirmed in the 1990s when Richard Carlton and others discovered planar deformation features (PDFs) in quartz grains from diamond-drilled rock core in the deep central uplift.
A traverse from outcropping, undeformed, flat lying rocks outside the crater toward the central peak uplift illustrates the complexity of the structure. The central uplift formation rock units are up to 275 m (900 ft) structurally higher and folded, faulted and brecciated than time-equivalent rock units outside the crater. Transitional zone rocks are less folded and faulted than the central peak rocks. And the outer faulted ring graben has down dropped up to 250 m (820 ft) from rocks outside the crater, hence John Locke’s name “Sunken Mountain”. Zones of brecciated rocks are associated with faulting throughout the crater.
B.Sc. & M.Sc. 1982 Geology, University of Toledo
Gulf Oil Corporation, consulting, ODNR Division of Geological Survey
Began career in oil and gas exploration of the Rocky Mountain region followed by Michigan Basin exploration. Continued work in the Ohio region utilizing geophysical, core, and sample analysis for studies of Precambrian, Cambrian, Ordovician, Silurian, and Devonian for oil and gas and deep saline reservoirs. Areas of interest include: Cambrian, Ordovician, and Silurian basin analysis, Precambrian basement tectonics and impact sites. Have been involved in numerous multi-state projects, published and unpublished reports and professional talks. Currently retired and working on regional subsurface geology and field mapping in the Appalachian thrust belt.
Credit ODNR Geological Survey