Decaturville
Key facts
- Country
- United States
- Diameter
- 6 km
- Age
- less than about 300 million years
- Location
- 37.90° N, 92.72° W
A shallow, roughly circular basin about 6 km across in the Ozark hills of Camden County, Missouri, with outcrops of broken and tilted rock in the centre.
Decaturville is an eroded impact structure about 6 km across in Camden County, Missouri, in the United States. Along with Crooked Creek, it is one of a cluster of round, disturbed structures in the Midwest once thought to be volcanic.
What it hit. The target was a sequence of Cambrian and Ordovician sedimentary rocks, mainly dolomites and sandstones, lying on Precambrian granite. In the centre of the structure, the rebound of the crater floor lifted rocks several hundred metres above their normal position, bringing Cambrian layers to the surface.
Proof of impact. Detailed mapping in the 1960s and 1970s by geologists of the United States Geological Survey found shatter cones, cone-shaped fractures that form only under the shock of an impact, and quartz grains showing shock features. They concluded that Decaturville was made by an impact, and their work made it a key example of how such structures form in layered rock.
Age. The youngest rocks affected are Pennsylvanian, so the impact happened less than about 300 million years ago. Its exact age is unknown.
Why it matters. Decaturville was one of the American structures studied during the Apollo era to understand craters on the Moon. The impactor is unknown.
Visiting. The structure is on private farmland and woodland. Ask permission before exploring.
Did you know?
Rock layers in the centre were lifted several hundred metres above their normal level.
Decaturville was mapped in detail during the Apollo era to help understand lunar craters.
It was once described as a cryptovolcanic structure.