Cwm Twrch

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

SSSI
Cwm Twrch SSSI is located on and around the Afon Twrch approximately 0.9 mi north-east of Ystradowen, and covers 2.4 ha.

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, and which marks the Westphalian A – Westphalian B boundary in this Carboniferous rock strata.