Formation
The massif is composed of crystalline basement (metamorphic and igneous rocks) with Proterozoic to early Paleozoic ages. It was deformed and metamorphosed during the Cadomian orogeny (Ediacaran, about 600 million years ago ago) and Caledonian orogeny (Silurian, about 420 million years ago). This basement is almost everywhere overlain by younger sedimentary rocks, except for some places in the southwest of England and in Wales.
The continent Avalonia was until the Ordovician (465 million years ago) part of the large southern continent Gondwana, but then began drifting independently to lower latitudes. As it passed through the dry latitudes represented today by the Namib Desert1, it was eroded and the soils became laterite represented by the Old Red Sandstone which shows its presence in the red soils of Devonshire. The strata, particularly of the Precambrian are complex. Their continuity is also poorly understood because they are beyond the reach of most boreholes.
Read more about this topic: London-Brabant Massif
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