Rock 366 : Day 107 : Base Old Red Sandstone

Day 107: The is the transition between the esturine marine Gray Sandstone Group and the terrestrial Milford Haven Group (Old Red Sandstone Supergroup) at Marloes Sands, Pembrokeshire, Wales. The transtion here is actually all Upper Silurian but bottom right can be seen the arrow carved by the BGS to mark the base of the Devonian in the old days whilst litho- and chronostratigraphy were still being confused.