 The bedrock of Mount Cardigan is the upper member of the Lower Devonian Littleton Formation (a light grey meta-turbidite) on its west flank (seen on lower parts of the West Ridge Trail).On the summit and to the east on the Clark Trail the bedrock is the Kinsman Granodiorite of the Early Devonian Cardigan Pluton (a foliated granitic body with large megacrysts of potassium feldspar).The Cardigan pluton has been dated by the Rb/Sr method at 411 +/- 19 MA.