Correlation of Old Red Sandstone (Devonian) outliers in the Northern Highlands of Scotland

SummaryA summary has been made of the distinguishing lithological features of four sedimentary groups long recognized from the Lower and Middle Old Red Sandstone (Devonian) of the Northern Highlands of Scotland. This has led to recognition of the groups in unfossiliferous outliers to the W, permitting the correlation of these outliers with the main outcrop.