Eolian Sequence and Erg Dynamics: The Permian Corrie Sandstone, Scotland

Abstract

ABSTRACT A nearly 700-m-thick sequence of Permian erg deposits was preserved in a rapidly subsiding inland basin (Arran, Scotland). The eolian sequence is composed of more than 30 superimposed erg units separated by erg-order deflation (super bounding) surfaces. Each erg unit (6 to 72 m in thickness; mean = 22 m) is initiated by flat-bedded eolian sandstones (0.5 to 7.0 m in thickness; mean = 2.9 m) of amalgamated interdraa or interdune origin and is topped by cross-bedded draa or dune sandstones (3 to 70 m in thickness; mean = 18 m). The eolian sequence represents alternating episodes of erg accumulation and erg deflation. These alternating constructional and destructional phases are related to climatic oscillations determining sand supply to the erg system. In the vertical dimension the erg units define six complete megacycles (62 to 184 m in thickness; mean = 110 m), each of which is composed of four to six erg units (basic cycles). The origin of this composite cyclicity is viewed in the light of Permian orbital climatic forcing and glacial cycles. Finally, the dynamics of the Corrie erg is compared to two Permian coastal erg systems in North America.