The Impact of Ohio's Extraterrestrial Visitor -
Geology of the Serpent Mound Disturbance
Greg Schumacher (Ohio Geological Survey, Columbus, Ohio, USA)
2009 Midwest Chapter of the Friends of Mineralogy
Symposium and Field Conference (Geology Department of Miami University, Oxford,
Ohio, USA)
5 September 2009
See
Schumacher’s Serpent Mound book (an Ohio Geological Survey book) - Baranoski et
al. (2003).
The
Serpent
Mound disturbance [see map &
info. - scroll down] was discovered in 1838 by John Locke. It is
30-35 square miles in size. Walter Bucher in 1933 published a Serpent
Mound geologic map.
August
Foerste was the first to map the Serpent Mound Structure - made a geologic map
in 1919.
There
are breccia zones along creeks in the central uplift of Serpent Mound.
Planar
deformation features (PDFs) have been found in Serpent Mound material.
Microdiamonds
have not been looked for and not identified yet at Serpent Mound - a good
research project for someone.
Serpent
Mound shattercones used to be called horsetail structures.
Serpent
Mound cores have “concrete rock” - very unlike anything else in Ohio. The
cores have mixes of shale, Upper Ordovician fossiliferous limestone, Silurian
stuff, etc. The stratigraphy has been completely disrupted.
En-echelon
normal faults are present in the core. There's also shattercones, sulfide
mineralization, and breccia zones between clasts.
Serpent
Mound Structure - a gravity low.
Fist-sized
Ohio Shale pieces occur in the Serpent Mound core - have quartz grains with
impact PDFs. This was proof that Serpent Mound is indeed an impact
structure.
Some
Serpent Mound core thin sections have pseudotachylite
melt features.
Faults
radiate out from the central uplift.
Serpent
Mound Impact age: Pennsylvanian-Permian, based on a paleomagnetics study.
The
impacting body was probably 150-200 meters in size. It would’ve
devastated Ohio, Indiana, Kentucky.
~1000-1500’
worth of rock have been removed by erosion since Serpent Mound formation.
But, not sure how much rock originally sat above what we have now.
The
Serpent Mound Structure is pretty limited in size at about 3000’ down.
A
Serpent Mound impact debris bed has not been identified yet in Ohio’s
Pennsylvanian-Permian succession.
Iowa’s
Manson Crater does have an ejecta bed 100 km away. The Manson Crater is
30-50 km in size.
The
Serpent Mound cores are still at the Ohio Geological Survey core barn.
Folks are invited to look for microdiamonds in Serpent Mound rocks.
The
Serpent Mound Crater is now gone - we’ve got the roots left.
Coesite
has not yet been found associated with Serpent Mound. To find coesite,
it's suggested that one looks in sandstone or quartz grains in Ohio
Shale.
Impact
diamonds perhaps may be found in the pseudotachylite.
