Highland Boundary Fault
The Highland Boundary Fault is a major geological fault line that traverses Scotland from Arran (Buteshire) and Helensburgh (Dunbartonshire) on the west coast to Stonehaven (Kincardineshire) in the east.[1] It separates two distinctly different physiographic and geological terrains: the Highlands from the Lowlands, and in most places it is recognisable as a change in topography. Where rivers cross the fault, they often pass through gorges, and the associated waterfalls can be a barrier to salmon migration.[2]
The fault is believed to have formed in conjunction with the Strathmore syncline to the south-east during the Acadian orogeny in a transpressive regime that caused the uplift of the Grampian block and a small sinistral movement on the Highland Boundary Fault.[3][4]
Discovery
One of the earliest and most prominent references to the Highland Boundary Fault was by the geologist George Barrow in 1912, I his paper ʻOn the Geology of Lower Dee-side and the Southern Highland Borderʼ, which highlights the nature of the rocks accompanying the Highland Border and describes the outlining mineral zones associated with metamorphism.[5] In the same publication, Barrow also outlines the ʻHighland Faultʼ and the areas where he believes there are planes of overthrust. Barrow's description of the structural nature of the rocks along the Highland Border suggests that rocks along both ends of the fault plane are indistinguishable from one another, with no brecciation.
Extent of fault
Aligned south-west to north-east from Lochranza on Arran, the Highland Boundary Fault bisects Bute and crosses the south-eastern parts of the Cowal and Rosneath Peninsulas, as it passes up the Firth of Clyde. It comes ashore near Helensburgh in Dunbartonshire, then continues through Loch Lomond, which lies within the long depression of the fault. The loch islands of Inchmurrin, Creinch, Torrinch, and Inchcailloch all form part of the Highland Boundary Fault.[6]
From Loch Lomond the Highland Boundary Fault continues through Perthshire to Aberfoyle, then Callander, Comrie and Crieff. It then forms the northern boundary of Strathmore and reaches the North Sea in Kincardineshire, immediately north of Stonehaven near the ruined Chapel of St Mary and St Nathalan.[4][7]
Aeromagnetic maps show that the Highland Boundary Fault can be traced from Ireland to the region of Greenock. The Highland Boundary Fault in these areas are seen to be dividing a northerly low area from a southerly high area.[8]
In 1970, Hall and Dagley identified the Highland Boundary Fault as coincident with a regional magnetic feature dividing a string of negative anomalies in the north from positive ones in the south.[8] On discovering this, Hall and Dagley concluded that the observed trend, which followed the length of the Dalradian trough transition from positive to negative anomalies. This linear feature of magnetic anomalies has since been referred to as the Fair Head–Clew Bay line.[9]
References
- ↑ Tanner, G. (2008). "Tectonic significance of the Highland Boundary Fault, Scotland". Journal of the Geological Society 165: 915. doi:10.1144/0016-76492008-012.
- ↑ "Natural obstructions: How nature makes salmon leap for their lives". Atlantic Salmon Trust Journal: 44–46. 2011. Archived from the original on 2013-10-04. https://web.archive.org/web/20131004215727/http://www.atlanticsalmontrust.org/library/library5.pdf. Retrieved 2013-10-02.
- ↑ "Loch Lomond: Highland Boundary Fault". 2008. http://www.scottishgeology.com/outandabout/classic_sites/locations/loch_lomond_fault.html.
- ↑ 4.0 4.1 "Highland Boundary Fault". 2011. http://www.scottish-places.info/features/featurefirst7728.html. Retrieved 2006-12-13.
- ↑ Barrow, G.: 'On the Geology of Lower Dee-side and the Southern Highland Border': Proceedings of the Geologists' Association, 1912; Vol 23, issue 5; pages 268–273
- ↑ Worsley, H.: 'Loch Lomond: The Loch, the Lairds and the Legends' Lindsay Publications, 1988) ISBN 978-1-898169-34-5
- ↑ Strang, George: 'Highland Fault Line at Stonehaven' (Curator notes, Volume 2; Tolbooth Museum and Stonehaven History Museum)
- ↑ 8.0 8.1 Max, M. D.; Riddihough, R. P.: 'Continuation of the Highland Boundary Fault in Ireland' (Geology, 1975; Vol 3, page 206)
- ↑ Harper, D.A.T.: 'Stratigraphical correlations adjacent to the Highland Boundary Fault in the west of Ireland' (Geological Society of London, 1988; Vol 146, page 381)
- Trewin, N. H.: 'Excursion Guide to the Geology of the Aberdeen Area' (Scottish Academic Press, 1987) ISBN 978-0-7073-0496-0