Cenozoic reactivation of the Great Glen Fault, Scotland; additional evidence and possible causes

• Published in: Journal of the Geological Society Vol. 170; no. 3; pp. 403 - 415
• Main Authors: Le Breton, Eline, Cobbold, P. R, Zanella, A
• Format: Journal Article
• Language: English
• Published: London, UK Geological Society of London 01.05.2013; The Geological Society of London; Geological Society Publishing House
• Subjects: Calcite; Caledonian Orogeny; Cenozoic; clastic rocks; Devonian; displacements; Earth Sciences; Eathie Scotland; Environmental Sciences; Eocene; Europe; exhumation; Faroe fracture zone; faults; folds; Fracture zones; Geological time; Geology; Global Changes; Great Britain; Great Glen Fault; Helmsdale Scotland; Jurassic; lateral faults; left-lateral faults; Mesozoic; Moray Firth; More-Trondclag Fault; Norway; Ocean floor; Oligocene; Ordovician; Organic matter; Orogeny; Paleogene; Paleozoic; rates; reactivation; Scandinavia; Sciences of the Universe; Scotland; sea-floor spreading; sedimentary rocks; shale; Shandwick Scotland; strike-slip faults; Structural geology; Studies; Tectonics; Tertiary; transpression; United Kingdom; uplifts; Western Europe; Iceland; ANE, British Isles, Scotland, Moray Firth; A, Atlantic; ANE, British Isles, Scotland; ANE, Atlantic, Faeroe Is
• ISSN: 0016-7649; 2041-479X
• DOI: 10.1144/jgs2012-067

The Great Glen Fault trends NNE-SSW across northern Scotland. According to previous studies, the Great Glen Fault developed as a left-lateral strike-slip fault during the Caledonian Orogeny (Ordovician to Early Devonian). However, it then reactivated right-laterally in the Tertiary. We discuss additional evidence for this later phase. At Eathie and Shandwick, minor folds and faults in fossiliferous Jurassic marine strata indicate post-depositional right-lateral slip. In Jurassic shale, we have found bedding-parallel calcite veins ("beef" and "cone-in-cone") that may provide evidence for overpressure development and maturation of organic matter at significant depth. Thus, the Jurassic strata at Eathie and Shandwick accumulated deeper offshore in the Moray Firth and were subject to Cenozoic exhumation during right-lateral displacement along the Great Glen Fault, as suggested by previous researchers. Differential sea-floor spreading along the NE Atlantic ridge system generated left-lateral transpressional displacements along the Faroe Fracture Zone from the Early Eocene to the Late Oligocene (c. 47-26 Ma), a period of uplift and exhumation in Scotland. We suggest that such differential spreading was responsible for reactivation of the Great Glen Fault. Indeed, left-lateral slip along the Faroe Fracture Zone is compatible with right-lateral reactivation of the Great Glen Fault.