First Use of Current-Bedding to Determine Orientation of Strata

Abstract

DR. ROBERT M. SHACKLETON1 has recently completed a revision of the structures of the Silurian and Devonian rocks of the Dingle Peninsula and Blasket Islands in south-west Eire. In this he has used the positions of truncated tops and asymptotic bases of current-deposited laminae in order to determine the correct order of succession, and has been able to demonstrate the probable equivalence of Anascaul Beds with Ferriter's Cove and Croaghmartin Beds (Silurian) and of Smerwick Beds with Dingle Beds (Downtonian). Axes of folding that trend from east-north-east to west-south-west have been plotted, and inverted beds are conclusively recognized on the north and south margins of the Peninsula and at Clogher Head. The final proof that the axis of an overfolded syncline runs through Ventry Harbour, Fahan Point, and between the Great Blasket and the two smaller islands of Inishnabro and Inishvickillane, vindicates the work of G. V. Du Noyer prior to 1859 in first tracing the inversion south of this important line and describing it despite opposition by J. Beete Jukes2, director of the Irish Geological Survey.