Flaxman
Key facts
- Country
- Australia
- Diameter
- 10 km
- Age
- more than about 35 million years
- Location
- 34.62° S, 139.07° E
No crater shape: farmland in the hills north-east of Adelaide, South Australia, where shatter cones occur in folded rocks.
Flaxman is a deeply eroded impact structure about 10 km across in South Australia, north-east of Adelaide, a few kilometres from the similar Crawford structure.
Discovery. Geologists working in the area found shatter cones, cone-shaped fractures produced only by shock, in outcrops of folded sedimentary rock. Microscopic shock features in quartz confirmed an impact.
What it hit. The impactor struck late Precambrian and Cambrian sedimentary rocks of the Adelaide Fold Belt, which had already been folded during an ancient period of mountain building.
Age. The age is poorly known. Flaxman is older than about 35 million years, based on younger sediments in the area, but it could be much older.
A double impact? Because Flaxman and Crawford lie so close together, some scientists have wondered whether they formed at the same time from a pair of asteroids. Their ages are too poorly known to tell.
Why it matters. Flaxman shows how shatter cones can reveal an impact long after its crater has been destroyed. The impactor is unknown.
Visiting. The area is farmland. Ask landowners' permission.
Did you know?
Flaxman and Crawford lie only a few kilometres apart.
Nobody knows whether the two formed at the same time.
Shatter cones are the main evidence for the impact.