WELLS CREEK IMPACT STRUCTURE
by: Charles O’Dale
- Type: Complex
- Age ma: 200 ± 100 a
- Diameter: ~12 km
- Location: N 36° 23’ W 87° 40’
- Shock Metamorphism: shatter cones & brecciation
a Dating Method: Geological – [see text]
Wells Creek is a confirmed meteorite impact site in Tennessee, USA. The Wells Creek structure was first noticed by railroad surveyors around 1855 and brought to the attention of J.M. Safford, Tennessee‟s State Geologist. He included an insert in the 1869 Geologic Map of Tennessee, which is the first known map to include the structure. The origin of the Wells Creek structure was controversial, and was interpreted as being either the result of volcanic steam explosion or meteorite impact. It was only in the 1960s that Wilson and Stearns were able to state that the impact hypothesis was preferred. Evidence for a Wells Creek meteorite impact includes drill core results, extreme brecciation and shatter cones, while a local lack of volcanic material is telling.
Since 325 Ma Mississippian rock is deformed at Wells Creek, the structure must have been formed after these rocks were deposited, and because the Cretaceous Tuscaloosa Formation (which dates to 75 Ma) has been found in the deformed area, the Wells Creek event must have occurred prior to the deposition of this Formation. No rock from any periods between these units have been found in any part of the structure, so on the basis of this geological evidence the age of the Wells Creek structure can only be estimated at 200 ± 100 million years.
Shatter cones found in a 610-m core drilled near the center of the Wells Creek structure were concentrated at a depth of 30 meters. A few shatter cones were found below 60 meters being not complete or well defined, except for a single exception at 377 meters depth.
J.R.H. Ford, Wayne Orchiston, Ron Clendening; THE WELLS CREEK METEORITE IMPACT SITE AND CHANGING VIEWS ON IMPACT CRATERING Journal of Astronomical History and Heritage, 15(3), 159-178 (2012).