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Evidence for metamorphic remagnetisation of upper Precambrian tillite in the Dalradian Supergroup of Scotland

Published online by Cambridge University Press:  03 November 2011

M. Stupavsky ,
D. T. A. Symons  and
C. P. Gravenor
M. Stupavsky
Affiliation:
Department of Geology, University of Windsor, Windsor, Ontario, Canada N9B 3P4.
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Abstract

A conglomerate test using 36 clast cores (76 specimens) from the upper Precambrian Port Askaid Tillite of the Dalradian Supergroup in the Garvellach–Islay region of Scotland shows that the tillite was remagnetised during orogenic activity in Lower Ordovician time. After 550°C thermal demagnetisation, the clast remanence directions give a mean of 155°, 14° (α95—12°). This is similar to the mean from four tillite matrix sites of 162°, 4° (α95—9°) and the mean ‘primary component direction’ of 166°, −12° (α95—6°) previously determined from the interbedded siltstones. This indicates that the matrix and siltstones were also remagnetised. These mean directions give virtual geomagnetic poles after tilt correction that fall within the cluster of British Ordovician poles from rocks in the Caledonian orogen, and thereby indicate a prefolding Ordovician age for the remagnetisation. Thermal demagnetisation studies and observations from polished and thin sections of tillite clast and matrix specimens show that secondary hematite derived from partially to completely altered magnetite is the dominant carrier of the metamorphic remagnetisation. These results show that remanence data from the Port Askaid Tillite cannot be used to support the hypothesis that a worldwide glaciation occurred during the Late Precambrian.

Keywords

Caledonian orogenclasthematitematrixpalaeomagnetismPort Askaid Tilliteremanence dataworldwide glaciation.
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 73 , Issue 2 , 1982 , pp. 59 - 65
Copyright
Copyright © Royal Society of Edinburgh 1982

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References

8. References

Abouzakhm, A. G. & Tarling, D. H. 1975. Magnetic anisotropy and susceptibility of late Precambrian tillites from northwestern Scotland. J GEOL SOC LONDON 131, 647–52.CrossRefGoogle Scholar
Briden, J. C. & Arthur, G. R. 1981. Precision of measurement of remanent magnetisation. CAN J EARTH SCI 18, 527–36.Google Scholar
Dewey, J. F. & Pankhurst, R. J. 1970. The evolution of the Scottish Caledonides in relation to their isotopie age pattern. TRANS R SOC EDINBURGH 68, 361–89.CrossRefGoogle Scholar
Fisher, R. A. 1953. Dispersion on a sphere. PROC R SOC LONDON 217A, 295–305.Google Scholar
Graham, J. W. 1949. The stability and significance of magnetism in sedimentary rocks. J GEOPHYS RES 54, 131–67.CrossRefGoogle Scholar
Harland, W. B. & Bidgood, D. E. T. 1959. Palaeomagnetism in some Norwegian sparagmites and late Pre-Cambrian ice age. NATURE 184, 1860–2.CrossRefGoogle Scholar
Harland, W. B. 1964. Critical evidence for a great infra-Cambrian glaciation. GEOL RUNDSCH 54, 45–61.Google Scholar
Harris, A. L. & Pitcher, W. S. 1975. The Dalradian Supergroup. GEOL SOC LONDON SPEC REP 6, 52–75.Google Scholar
Harrison, C. G. A. 1980. Analysis of the magnetic vector in a single rock specimen. GEOPHYS J R ASTRON SOC 60, 489–92.CrossRefGoogle Scholar
Kröner, A., McWilliams, M. O., Germs, G. J. B., Reid, A. B. & Schalk, K. E. L. 1980. Palaeomagnetism of late Precambrian to early Paleozoic mixtite bearing formations in Namibia (Southwest Africa): The Nama group and Blaubeker Formation. AM J SCI 280, 942–68.CrossRefGoogle Scholar
Kulling, O. 1934. Scientific results of the Swedish-Norwegian Arctic Expedition in the summer of 1931, part Xl, the “Hecla Hoek Formation” around Hinlopenstredet. GEOGR ANN 16, 161–253.Google Scholar
Leggo, P. J. & Pidgeon, R. T. 1970. Geochronological investigations of Caledonian History in western Ireland. ECLOG GEOL HELV 63, 207–12.Google Scholar
Lowrie, W., Channell, J. E. T. & Heller, F. 1980. On the credibility of remanent magnetisation measurements. GEOPHYS J R ASTRON SOC 60, 493–6.CrossRefGoogle Scholar
McElhinny, M. W. & Embleton, B. J. J. 1976. Precambrian and Early Palaeozoic palaeomagnetism in Australia. PHILOS TRANS R SOC LONDON 280A, 417–31.CrossRefGoogle Scholar
McWilliams, M. O. & McElhinny, M. W. 1980. Precambrian palaeomagnetism of Australia. J GEOL 88, 1–26.CrossRefGoogle Scholar
Moorbath, S. 1975. Progress in isotope dating of British Precambrian. GEOL SOC LONDON SPEC REP 6, 108–12.Google Scholar
Morris, W. A. 1976. Transcurrent motion determined palaeomagnetically in the Northern Appalachians and Caledonides and the Acadian Orogeny. CAN J EARTH SCI 13, 1236–43.CrossRefGoogle Scholar
Morris, W. A. 1977. Paleolatitude of glaciogenic upper Precambrian Rapitan Group and the use of tillites as chronostratigraphic marker horizons. GEOLOGY 5, 85–8.2.0.CO;2>CrossRefGoogle Scholar
Pankhurst, R. J. 1970. The geochronology of the basic igneous complexes. SCOTT J GEOL 6, 83–107.CrossRefGoogle Scholar
Pankhurst, R. J. 1974. Rb-Sr whole rock chronology of Caledonian events in North-East Scotland. BULL GEOL SOC AM 85, 345–50.2.0.CO;2>CrossRefGoogle Scholar
Pidgeon, R. T. 1969. U-Pb ages from Galway granite and the Dalradian, Connemara, Ireland. SCOTT J GEOL 5, 375–92.Google Scholar
Pringle, I. R. 1972. Rb/Sr age determinations on shales associated with the Varanger Ice Age. GEOL MAG 109, 465–72.Google Scholar
Pullaiah, G., Irving, E., Buchan, K. L. & Dunlop, D. J. 1975. Magnetization changes caused by burial and uplift. EARTH PLANET SCI LETT 28, 133–43.Google Scholar
Schaub, H. P. 1950. On the Pre-Cambrian to Cambrian sedimentation in NE-Greenland. MEDD GRØNLAND 114.Google Scholar
Spencer, A. M. 1971. Late Precambrian Glaciation in Scotland. MEM GEOL SOC LONDON 6.Google Scholar
Spjeldnaes, N. 1964. The Eocambrian Glaciation in Norway. GEOL RUNDSCH 54, 24–45.Google Scholar
Tarling, D. H. 1974. A palaeomagnetic study of Eocambrian tillites in Scotland. J GEOL SOC LONDON 130, 163–77.CrossRefGoogle Scholar
Van Alstine, D. R. 1980. Analysis of the modes of directional data with particular reference to palaeomagnetism. GEOPHYS J R ASTRON SOC 61, 101–13.Google Scholar
Van der Voo, R., Briden, J. C. & Duff, B. A. 1980. Late Precambrian and Paleozoic palaeomagnetism of the Atlantic-bordering continents. In Cogné, J. & Slansky, M. (eds) Geology of Europe from Precambrian to post-Hercynian sedimentary basins, 203–12. COLLOQ 26TH INT GEOL CONGR C6.Google Scholar
Watson, G. S. 1956. A test for randomness of directions. MON NOT R ASTRON SOC, GEOPHYS SUPPL 7, 160–1.Google Scholar
Watson, J. V. 1975. The Precambrian rocks of the British Isles–a preliminary review. GEOL SOC LONDON SPEC REP 6, 1–10.Google Scholar