The Bearreraig Sandstone Series (Middle Jurassic) of Skye and Raasay

Abstract

Synopsis The Bearreraig Sandstone Series crops out in north-east Skye, Raasay and Strathaird. In Strathaird the extremely rapid variations in thickness and lithology suggest near-shore deposition. In Raasay the northward increase in the proportion of bioclastic material suggests derivation of terrigenous material from a main source to the south. In north-east Skye, however, the dominant features of sedimentation can be traced over a wider area, suggesting that the area was less influenced by strictly local factors. There were two main basins, one in north Skye, and the other in Raasay and Strathaird, separated by an area of relatively slow subsidence in the area between Raasay and north-east Skye. In north-east Skye most of the ammonite zones have been located, but in Raasay and Strathaird, where much of the series is cross-bedded, only some zones can be identified. The base of the cross-bedded rocks is diachronous. There are three sedimentary cycles, with a sharp change to shale at the base, followed by a gradation to sandstone. The bases of the cycles coincide with changes in the ammonite faunas, and can be correlated with transgressions in other areas.