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Fracture development and diagenesis of Torridon Group Applecross Formation, near An Teallach, NW Scotland; millennia of brittle deformation resilience?

Magdalena A. Ellis, Steve E. Laubach, P. Eichhubl, J. E. Olson and P. Hargrove
Fracture development and diagenesis of Torridon Group Applecross Formation, near An Teallach, NW Scotland; millennia of brittle deformation resilience?
Journal of the Geological Society of London (May 2012) 169 (3): 297-310

Abstract

The Late Proterozoic Torridon Group Applecross Formation in the foreland of the Moine Thrust Belt, NW Scotland, contains deformation bands, three fracture sets (from oldest to youngest A, B, and L) defined by orientation, crosscutting relations, and progressively less quartz cement in younger sets, and joints. Set A crosscuts deformation bands and strikes north-south. Set B has trimodal orientation defining three linked subsets that formed concurrently. Set L strike ranges from NE-SW to ENE-WSW, in parent crack-wing crack arrays that formed progressively; these are more abundant near small-displacement, oblique-slip faults that offset the overlying Cambrian Eriboll Formation and the Moine Thrust Belt. Applecross sandstones have low fracture abundance, possibly a consequence of low elastic moduli (Young's modulus 2.3-17.0 GPa, most values <6.9 GPa) and moderate to high subcritical crack index (45-78), resulting from compacted soft lithic grains and clay-mineral cements. Low abundance contradicts models that postulate persistent incipient failure by subsurface fracture. The fracture sequence resembles that found in the overlying Cambrian Eriboll Formation quartzarenites, implying that no widespread late Proterozoic fracture sets exist in this part of the Applecross Formation, an uneventful record for a rock profoundly resistant to brittle deformation.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 169
Serial Issue: 3
Title: Fracture development and diagenesis of Torridon Group Applecross Formation, near An Teallach, NW Scotland; millennia of brittle deformation resilience?
Affiliation: University of Texas at Austin, Jackson School of Geosciences, Austin, TX, United States
Pages: 297-310
Published: 201205
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 70
Accession Number: 2012-056748
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, geol. sketch map
N57°48'24" - N57°48'24", W05°15'06" - W05°15'06"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201229
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