The Buchan anticline of the Banff nappe of Dalradian rocks in North-East Scotland

Publisher Website
Google Scholar
Abstract
Summary: The Dalradian rocks involved in the Buchan anticline in Aberdeenshire belong to four groups: (1) the Ellon Gneisses, in part migmatitic, equated with the Ben Lui-Ben Lawers groups of the standard Lower Dalradian of Perthshire, (2) the Mormond Hill Quartzite, placed in the Upper Dalradian, and conformably followed eastwards by (3) the Collieston Beds of greywacke facies, and lastly, (4) the Fraserburgh Beds of similar facies occurring west of the Mormond Hill Quartzite, from which they are separated by a dislocation. The Buchan anticline is a structure imposed on the great recumbent fold of the Banff nappe, this being made of a migmatitic core of the Lower Dalradian Ellon Gneisses, separated from the Upper Dalradian by a dislocation, the Boyne lag. The anticline is considered to result from the eastward and upward movement of the migmatized core of the great fold. As a consequence, the Collieston Beds are piled up to the east in front of the brow in a gigantic stack of small recumbent folds. West of the tectonic aggregation of Mormond Hill Quartzite which caps the Ellon Gneiss anticline, the Fraseburgh Beds have slid down a gentler tectonic slope into the Turriff syncline—they are characterized by broad, gentle, synclinal portions and narrow, steeply overtuned, anticlinal portions. These cover movements are considered to be activated by a bulging upwards deep down in the migmatitic core of the Banff nappe; the Collieston and Fraserburgh Beds are shed off on the two sides of the maximum rise. As the movements ended, an essentially thermal metamorphism, effected by heat-conduction from the migmatite core and characterized by regional andalusite and cordierite, was overprinted on the folded cover. The metamorphic zones form a metamorphic "anticline" two miles west of the tectonic anticline. In the centre of this metamorphic "anticline", the migmatite front has risen highest into the cover folds.

This publication has 7 references indexed in Scilit: