[1] The rock of the formation is made up of interleaved beds of silty mudstones and siltstones with some sandstones and tuffs also present in small amounts.

The formation runs diagonally across Mid Wales from close by Bala Lake to Cardigan Bay near Tywyn.

[2] The formation is exposed in a number of locations in Mid Wales where glacial valleys cut across it.

Harnagian-Soudleyan trilobites have been found in the rocks of the Ceiswyn Formation near Dinas Mawddwy.

This article about a specific stratigraphic formation in the United Kingdom is a stub.