Cwm Twrch

Site of Special Scientific Interest · 51.7998, -3.8047

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Dyfed CountyPowys County

Geology & landscape

Geological Period: Carboniferous

Landscape processes: Glacial

Description

Description The best exposure in South Wales of the interval of Carboniferous rock strata straddling the Westphalian A – Westphalian B boundary. The Amman Marine Band, which indicates the position of the boundary, is well seen here and contains a relatively diverse fauna. This site is of considerable importance because it fills in the gap in the Cwm Gwrelych – Nant Llyn Fach section, completing a continuous sequence of strata from the base of the Westphalian A to the upper Westphalian C.