BP

Key facts

Country

Libya

Diameter

3.2 km

Age

less than about 120 million years

Location

25.32° N, 24.32° E

BP, also known as Gebel Dalma, is an eroded impact structure about 3.2 km across in the Libyan Desert, in south-eastern Libya. It is named after the oil company British Petroleum, whose geologist first visited it.

Discovery. In 1967 scientists studying aerial and space photographs of the Sahara noticed two unusual ring structures, this one and the larger Oasis structure about 80 km to the south. In 1968 a geologist working for British Petroleum visited the smaller one and named it after his company.

What it hit. The impactor struck the Nubian Sandstone, a thick layer of sandstone and siltstone of early Cretaceous age that covers much of the eastern Sahara. Erosion has since removed the crater rim and fill, leaving three broken rings of ridges around a central uplift.

Proof of impact. In the early 1970s geologists found microscopic planar features in quartz from the central uplift. A later visit failed to find the most convincing shock features, but in 2010 fresh samples yielded quartz with planar deformation features, confirming an impact.

Age. No rocks suitable for dating have been found. The impact happened after the Nubian Sandstone was laid down, so it is younger than about 120 million years.

A double impact? BP and Oasis show similar amounts of erosion and may have formed at the same time, perhaps from a pair of asteroids. Both were once suggested as the source of Libyan desert glass, a natural yellow glass found in western Egypt, but chemical studies do not support this.

Visiting. The site is extremely remote desert.

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