Flynn Creek
Key facts
- Country
- United States
- Diameter
- 3.8 km
- Age
- about 382 million years (Late Devonian)
- Location
- 36.28° N, 85.67° W
Low hills and a subtle hollow in the valley of Flynn Creek, Jackson County, Tennessee, with exposures of breccia and tilted limestone along the creek and roads.
Flynn Creek is a small impact crater about 3.8 km across in north-central Tennessee, in the United States. It formed in the Late Devonian, around 382 million years ago, when a shallow sea covered much of North America.
A marine impact. The impactor struck a sea floor of Ordovician limestones and dolomites. Despite its small size, the crater is a complex crater with a central uplift, where rocks were lifted several hundred metres. Soon after the impact, the sea washed broken rock back into the crater, and then a thick layer of black mud settled in it. That mud became the Chattanooga Shale, which covers a large area of the region and fixes the crater's age.
Proof and study. Flynn Creek was first described in the early twentieth century as a 'cryptovolcanic' structure. In the 1960s and 1970s the geologist David Roddy studied it intensively as a comparison for lunar craters, and a series of research boreholes was drilled through it. Shatter cones, cone-shaped fractures that form only under shock, together with quartz grains showing shock features and a central uplift with the dimensions expected for an impact crater, show that it was made by an impact.
Why it matters. Because Flynn Creek was buried quickly by marine sediments, it is unusually well preserved for its age. It is a classic example of a small complex crater formed in a shallow sea. The impactor is unknown.
Visiting. The site is mostly private farmland and woodland. Ask permission before exploring outcrops, and take care along creek banks.
Did you know?
Flynn Creek was buried by black mud that became the Chattanooga Shale.
It was studied in the 1960s and 1970s as a comparison for craters on the Moon.
Although small, it has a central uplift like much larger craters.