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The Highland Boundary Fault and the Highland Border Complex

B. J. Bluck
The Highland Boundary Fault and the Highland Border Complex
Scottish Journal of Geology (2010) 46 (2): 113-124

Abstract

Stratigraphic evidence, petrography and way up criteria are presented to show that the bulk of the Highland Border Complex in Scotland gets younger to the NW, towards the largely Neoproterozoic, Dalradian block. An early ophiolite has fed younger sediments with detritus, which, in the absence of reliable fossils, has provided a control on the stratigraphical order, placing the "Margie Series" younger than the dated Dounans Limestone. Tanner & Sutherland (2007) see the complex as divided into two groups one of which overlies, and is a continuation of the Dalradian sequence, and therefore took part in its folding. This view is false. The Highland Border Complex is a sequence of rocks, disposed in phacoids, beginning with an ophiolite in the Early Ordovician followed by younger rocks which include shales, pillow lavas and sandstones. This sequence was deposited whilst the Dalradian highlands rose and shed large volumes of sediment, which have yet to be identified south of the Highland Boundary Fault. The boundary between the Dalradian and the Highland Border Complex, the Highland Boundary Fault, is therefore a major fracture bringing unrelated (but not exotic) Highland Border Complex rocks adjacent to the Dalradian Block. In terms of its structural control, the terrestrial Old Red Sandstone is a continuation of the Highland Border Complex, being progressively less deformed as time went on. It was probably laid down in transcurrent fault-generated basins which were gradually converged upon by the Dalradian Block and in so doing, uplifted some of the more northerly basins, possibly resting on Dalradian sediments, to yield sediment to the younger basins further to the south. The Highland Border Complex forms the basement to the Old Red Sandstone and, in places, forms a plane of detachment upon which the overlying basins formed. This may account for the extreme heterogeneous nature of its deformation from extensively sheared to totally unsheared rocks.


ISSN: 0036-9276
EISSN: 2041-4951
Coden: SJGEAX
Serial Title: Scottish Journal of Geology
Serial Volume: 46
Serial Issue: 2
Title: The Highland Boundary Fault and the Highland Border Complex
Author(s): Bluck, B. J.
Affiliation: University of Glasgow, Department of Geography and Earth Sciences, Glasgow, United Kingdom
Pages: 113-124
Published: 2010
Text Language: English
Publisher: Geological Society Publishing House for the Geological Societies of Edinburgh and Glasgow, Bath, United Kingdom
References: 77
Accession Number: 2011-039719
Categories: Structural geologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N55°52'60" - N55°52'60", W04°15'00" - W04°15'00"
N56°28'00" - N56°28'00", W03°00'00" - W03°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201123
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