The Tennessee meteorite impact sites and changing perspectives on impact cratering

The Tennessee meteorite impact sites and changing perspectives on impact cratering

Terrestrial impact structures offer astronomers and geologists opportunities to study the impact cratering process. Tennessee has four structures of interest. Information gained over the last century and a half concerning these sites is scattered throughout astronomical,
geological and other specialized scientific journals, books, and literature, some of which are elusive. Gathering and compiling this widely-spread information into one historical document benefits the scientific community in general.

The Wells Creek Structure is a proven impact site, and has been referred to as the ‘syntype’ cryptoexplosion structure for the United State. It was the first impact
structure in the United States in which shatter cones were identified and was probably the subject of the first detailed geological report on a cryptoexplosive
structure in the United States. The Wells Creek Structure displays bilateral symmetry, and three smaller ‘craters’ lie to the north of the main Wells Creek structure along its axis of symmetry. The question remains as to whether or not these structures have a common origin with the Wells Creek structure.

The Flynn Creek Structure, another proven impact site, was first mentioned as a site of disturbance in Safford’s 1869 report on the geology of Tennessee. It has been
noted as the terrestrial feature that bears the closest resemblance to a typical lunar crater, even though it is the probable result of a shallow marine impact. Flynn Creek
is home at least ten caves including the only cave known to have formed in the central uplift of a terrestrial complex crater.

The Dycus Structure lies only 13 km to the north-northwest of Flynn Creek and may be associated with the Flynn Creek impact event. It is not a proven impact site, but shows strong evidence of meteorite impact with features that reflect on the rock pressures attained during the deformation process. Dycus is elliptical in shape and
possesses an offset ‘central’ uplift even though it is too small to be a complex crater.

The Howell Structure was included in a 1949 list of the twelve best-known ‘cryptovolcanic’ structures. Features that may be shatter cones have been found in the Howell Structure, but they are poorly formed and indistinct. Breccias and planar fractures in quartz grains found within the circular structure are evidence of a disturbance, but whether or not this disturbance was due to an impact has yet to be determined. Howell remains a suspected impact site.