Cwm Twrch

Cwm Twrch is a Site of Special Scientific Interest in Carmarthenshire, Wales.

SSSI

Cwm Twrch SSSI is located on and around the Afon Twrch approximately north-east of Ystradowen, and covers.
The site is notable for its geology, where river erosion provides the best exposes the Amman Marine Band, a sedimentary layer showing a diverse fauna, which marks the Westphalian A – Westphalian B boundary in this Carboniferous rock strata.