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Gravitational collapse and extension along a mid-crustal detachment: the Lough Derg Slide, northwest Ireland

Published online by Cambridge University Press:  01 May 2009

G. I. Alsop
G. I. Alsop
Affiliation:
Department of Geological Sciences, University of Durham, Durham DH1 3LE, U.K.
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Abstract

Pre-Caledonian basement is juxtaposed with an inverted Upper Dalradian cover sequence along the Lough Derg Slide, in south Donegal, northwest Ireland. Shear-sense criteria indicate that the Dalradian Succession is translated via oblique dextral thrusting over high pressure granulite facies basement in the footwall. Crustal thickening induced by large scale folding associated with this ductile thrusting resulted in mid-amphibolite facies metamorphism adjacent to the sole of the Dalradian nappe. Subsequent to peak metamorphism, the overthickened Dalradian cover sequence suffered heterogenous deformation associated with ductile extension concentrated in the strain-softened mylonites of the hangingwall. The oblique ductile thrusts initiated during crystal thickening were reactivated in a normal sense. Pre-existing fold axes rotated towards the extensional transport direction, which is marked by a secondary stretching lineation with associated S–C fabrics. Ductile extension and hangingwall collapse are considered to be related to gravitational instability induced by the earlier crustal thickening episode.

Type
Articles
Information
Geological Magazine , Volume 128 , Issue 4 , July 1991 , pp. 345 - 354
Copyright
Copyright © Cambridge University Press 1991

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References

Alsop, G. I. & Hutton, D. H. W. 1990. A review and revision of Dalradian stratigraphy in central and southern Donegal, Ireland. Irish Journal of Earth Sciences 10, 181–98.Google Scholar
Anderson, J. G. C. 1948. The occurrence of Moinian rocks in Ireland. Quarterly Journal of the Geological Society of London 103 (for 1947), 171–90.Google Scholar
Borradaile, G. J. 1974. The structure of the Moine-like rocks near Lough Derg, County Donegal, Eire. Geological Journal 9, 61–4.CrossRefGoogle Scholar
Coward, M. P. 1982. Surge zones in the Moine Thrust Zone of NW Scotland. Journal of Structural Geology 4, 247–56.CrossRefGoogle Scholar
Coward, M. P. 1988. The thrust and normal faults of the Ullapool-Strath Kanaird region and their implications for NW Highland tectonics. Scottish Journal of Geology 24, 35–50.CrossRefGoogle Scholar
Escher, A. & Watterson, J. 1974. Stretching fabrics, folds and crustal shortening. Tectonophysics 22, 223–31.Google Scholar
Glazner, A. F. & Bartley, J. M. 1985. Evolution of lithospheric strength after thrusting. Geology 13, 42–5.2.0.CO;2>CrossRefGoogle Scholar
Holdsworth, R. E. 1989. Late brittle deformation in a Caledonian ductile thrust wedge: new evidence for gravitational collapse in the Moine Thrust sheet, Sutherland, Scotland. Tectonophysics 170, 17–28.Google Scholar
Lister, C. S. & Snoke, A. 1984. S–C mylonites. Journal of Structural Geology 6, 617–38.CrossRefGoogle Scholar
McClay, K. R., Norton, M. G., Coney, P. & Davis, G. H. 1986. Collapse of the Caledonian orogen and the Old Red Sandstone. Nature (London) 323, 147–9.CrossRefGoogle Scholar
Max, M. D. & Long, C. B. 1985. Pre-Caledonian basement in Ireland and its cover relationships. Geological Journal 20, 341–6.CrossRefGoogle Scholar
Phillips, U. E. A., Taylor, W. E. G. & Sanders, I. S. 1975. An analysis of the geological history of the Ox Mountains Inlier. Scientific Proceedings of the Royal Dublin Society 56, 311–29.Google Scholar
Pitcher, W. S. & Berger, A. R. 1972. The Geology of Donegal: A Study of Granite Emplacement and Unroofing. New York, London: Wiley Interscience, p. 435.Google Scholar
Pitcher, W. S., Elwell, R. W. D., Tozer, C. F. & Cambray, F. W. 1964. The Leannan Fault. Quarterly Journal of the Geological Society of London 120, 241–73.CrossRefGoogle Scholar
Pitcher, W. S., Shackleton, R. M. & Wood, R. S. R. 1971. The Ballybofey Anticline: a solution of the general structure of parts of Donegal and Tyrone. Geological Journal 7, 321–8.CrossRefGoogle Scholar
Powell, D. 1965. Comparison of calc-silicate bands from the Moine Schists of Inverness-shire with similar bands from Moine-like rocks in Donegal. Nature (London) 206, 180.Google Scholar
Powell, D. & Glendinning, N. W. 1990. Late Caledonian extensional reactivation of a ductile thrust in NW Scotland. Journal of the Geological Society, London 147, 979–87.CrossRefGoogle Scholar
Sanders, I. S., Daly, J. S. & Davies, G. R. 1987. Late Proterozoic high-pressure granulite facies metamorphism in the north-east Ox inlier, north-west Ireland. Journal of Metamorphic Geology 5, 69–85.CrossRefGoogle Scholar
Sanderson, D. J. 1973. The development of fold axes oblique to the regional trend. Tectonophysics 16, 55–70.Google Scholar
Van Breeman, O., Halliday, A. N., Johnson, M. R. W. & Bowes, D. R. 1978. Crustal additions in late Precambrian times. In Crustal Evolution in Northwestern Britain and Adjacent Regions (eds Bowes, D. R. and Leake, B. E.), pp. 81–106. Geological Journal Special Issue No. 10.Google Scholar
Woodland, A. W. 1977. 1:250,000 map of Ireland, Sheet 1. Geological Survey of Northern Ireland.Google Scholar
Yardley, B. W. D. 1980. Metamorphism and orogeny in the Irish Dalradian. Journal of the Geological Society, London 137, 303–9.CrossRefGoogle Scholar
Yardley, B. W. D., Long, C. B. & Max, M. D. 1979. Patterns of metamorphism in the Ox Mountains and adjacent parts of western Ireland. In The Caledonides of the British Isles – Reviewed (eds Harris, A. L. and others), pp. 369–74. Geological Society of London Special Publication no. 8.Google Scholar