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The Ohio Dillon Falls Subsurface Structure; Impact Crater or Tectonic Feature?

Mason, Greg1, Doyle R. Watts2, David Bean2, Mark T. Baranoski3, and Max Brown4
1 NGO Development Corp., Newark, OH
2 Wright State University, Dayton, OH
3 Ohio Division of Geological Survey, Columbus, OH
4 University of Toledo, Toledo, OH

The natural gas bearing Dillon Falls structure is seen on 2-D seismic reflection sections from Muskingum County, Ohio, as a bowl shaped disruption of the normally flat lying Cambrian reflectors. The feature appears to be about 2 kilometers wide on one seismic profile. The distribution of seismic lines does not allow verification of the structure’s symmetry or circular aspect. The seismic data show what appears to be a central uplift over which compaction and draping of sediments are evident at least as high as the Trenton reflector. The seismic data also show an uplifted portion near the margin of the structure that may be a ring anticline. These features are all consistent with an impact origin of the structure.

A gravity survey conducted along the course of the seismic line that best shows the feature did not reveal any anomalies. Magnetic survey data do not indicate the presence of significant intrusive activity, or a magnetic low, often associated with impacts.

The Murray # 2-1875 well drilled in the imaged uplift to a depth of 2067.8 m encountered an anomalous thickness of Rose Run Sandstone and the Conasauga Formation at 2015.3 m. No technical problems were reported in the drilling of the well with the tension log showing no change through the Cambrian section. Well cuttings from the Conasauga contain igneous and metamorphic rock fragments, some with conspicuous phlogopite. Critical to the discussion of the origin of the structure is the interpretation of geophysical well logs, on which the authors differ.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004