Depositional structures from Jurassic boulder beds, East Sutherland

Kimmeridgian boulder beds with interbedded sandstone and shale near Helmsdale, Scotland, have yielded seventy-six observations of eleven different types of sedimentary structures that give information on the direction of emplacement. The data confirm the interpretation of Bailey and Weir (1932) that the blocks were shed from a scarp along the Brora-Helmsdale fault to the north-west. Debris apparently slid downslope from scree, here and there cutting channels and forming folds within the breccia layers and just beneath as it scraped across mud and sand. Locally tabular and elongate blocks were oriented. The sandstone was also derived from the north-west and contains numerous examples of two kinds of lineations, a few ripplemarks, and rare small-scale cross stratification.