Multicomponent magnetizations in the Foyers Old Red Sandstone (northern Scotland) and their bearing on lateral displacements along the Great Glen Fault

Abstract

SUMMARY The Foyers Sandstone, a constituent of the Old Red Sandstone of northern Scotland, located on the eastern flank of the Great Glen Fault, has yielded a multicomponent palaeomagnetic structure. The principal magnetization (called the B component), with in situ mean direction D, I = 185, +8; ag5 = 2.7, post-dates the local 'mid'-Devonian (Acadian) tectonic event, but this direction corresponds well with characteristic directions displayed by Devonian and Lower Carboniferous rocks of Scotland. The most significant overprinted component, the A2 magnetization, with in situ mean direction D, I = 194, -27; ag5 = 4. lo, has a more patchy occurrence than the B remanence, the strongest development of A2 being observed at sites that are situated close to the Great Glen Fault zone. The A2 direction is consistent with a Hercynian age. A third magnetization, the A1 component, of suggested Lower Tertiary age, has been found at one of the sites close to the fault zone. The A2 and B remanences support previously proposed declination discordances in corresponding magnetizations across the Great Glen Fault. It is concluded that the Foyers Sandstone developed its multicomponent magnetization through repeated tectonic events on the Great Glen Fault in Acadian, Hercynian and Alpine times respectively.