Richat Structure
Richat Structure
It is an eroded geological dome), 40 kilometres (25 mi) in diameter, caused by a subsurface igneous intrusion deforming the overlying sedimentary rock layers, causing the rock to be exposed as concentric rings with the oldest layers exposed at the centre of the structure. Igneous rock is exposed inside and there are rhyolites and gabbros that have undergone hydrothermal alteration, and a central megabreccia. The structure is also the location of exceptional accumulations of Acheulean Paleolithic stone tools. It was selected as one of the 100 geological heritage sites identified by the International Union of Geological Sciences (IUGS) to be of the highest scientific value.
Description
!Cross section of the structure. Magenta is the volcanic intrusion, while purple, green and grey represent sedimentary layers
Description
The Richat Structure is a deeply eroded, slightly elliptical dome) with a diameter of 40 kilometres (25 mi). The sedimentary rock exposed in this dome ranges in age from Late Proterozoic within the center of the dome to Ordovician sandstone around its edges. The sedimentary rocks composing this structure dip outward at 10–20°. Differential erosion of resistant layers of quartzite has created high-relief circular cuestas. Its center consists of a siliceous breccia covering an area that is at least 30 kilometres (19 mi) in diameter.
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