Serra da Cangalha | |
---|---|
Impact crater/structure | |
Confidence | Confirmed |
Diameter | 12–13 km (7.5–8.1 mi) |
Age | <300 Ma |
Exposed | Yes |
Drilled | Yes |
Location | |
Location | Parnaíba Basin |
Coordinates | 8°5′S 46°52′W / 8.083°S 46.867°W |
Country | Brazil |
State | Tocantins |
Serra da Cangalha is an impact crater in the State of Tocantins, near the border of Maranhão State, in north/northeastern Brazil.[1] The crater is between 12 and 13 kilometres (7.5 and 8.1 mi) in diameter, making it the second-largest known crater in Brazil.[2] Its age is estimated to be about 220 million years (Triassic period).[3] The name means Pack-Saddle Mountains in Portuguese.
The outer perimeter is a circular inward scarp about 12 kilometres (7.5 mi) in diameter on the largely undisturbed Cretaceous and upper Silurian sediments of the Parnaíba basin,[4] breached on the west, north, and south sides by drainage valleys. Within the perimeter there is a series of concentric circular valleys and a central basin, all at roughly the same elevation, separated by ring walls. Shuttle Radar Topography Mission imagery shows a faint ring about 11 kilometres (6.8 mi) in diameter, a second ring of gentle hills about 5 to 6 kilometres (3.1 to 3.7 mi) in diameter, and an inner ring of steeper hills, about 3 kilometres (1.9 mi) in diameter and up to 420 metres (1,380 ft) high, open to the northwest, surrounding a central basin about 2.2 kilometres (1.4 mi) in diameter.[5][6][7]
The impact origin is attested by the presence of impact breccias, quartzite shatter cones and shocked quartz. The meteorite is believed to have struck the surface at a low oblique angle, 25 to 30 degrees on dry land. Radial faults are present inside the crater, and some extend up to 16 km from the center.[7] Disturbed and steeply inclined sediments from the Carboniferous and Devonian periods occur within the crater. A magnetic survey of the structure indicates that deformation within the crater extends to a depth of about 2 kilometres (1.2 mi).[3][5][6][8][9]
The identification of the structure as an impact crater was first published in 1973 by R.S. Dietz and B.M. French.[10][11] Shatter cones were reported by Beatty in 1980.[12] Impact breccias, impact melting, and shocked quartz were reported by McHone in his 1986 thesis.[13] A magnetic survey of the structure was published by A.A. Adepelumi and others in 2005.[6]