Geological Magazine

Original Article

Variscan sourcing of Westphalian (Pennsylvanian) sandstones in the Canonbie Coalfield, UK

ANDREW MORTONa1a2 c1, MARK FANNINGa3 and NEIL JONESa4 p1

a1 HM Research Associates, 2 Clive Road, Balsall Common, West Midlands CV7 7DW, UK

a2 CASP, Department of Earth Sciences, University of Cambridge, 181a Huntingdon Road, Cambridge CB3 0DH, UK

a3 Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia

a4 British Geological Survey, Keyworth, Nottingham NG12 5GG, UK

Abstract

The zircon age spectrum in a sample from the Canonbie Bridge Sandstone Formation (Asturian) of southern Scotland contains two main peaks. One is Early Carboniferous in age (348–318 Ma), and corresponds to the age of igneous activity during the Variscan Orogeny. The other is of late Neoproterozoic to early Cambrian age (693–523 Ma), corresponding to the Cadomian. Together, these two groups comprise 70 % of the zircon population. The presence of these two peaks shows unequivocally that a significant proportion of the sediment was derived from the Variscides of western or central Europe. The zircon population also contains a range of older Proterozoic zircons and a small Devonian component. These could have been derived from the Variscides, but it is possible that some were locally derived through recycling of northerly derived sandstones of Devonian–Carboniferous age. The zircon age data confirm previous suggestions of Variscide sourcing to the Canonbie area, made on the basis of petrographical, heavy mineral and palaeocurrent evidence, and extend the known northward distribution of Variscan-derived Westphalian sediment in the UK.

(Received April 10 2009)

(Accepted December 02 2009)

(Online publication February 12 2010)

Keywords:

  • zircon;
  • provenance;
  • Asturian;
  • southern Scotland;
  • Variscides

Correspondence:

c1 Author for correspondence: a.c.morton@heavyminerals.fsnet.co.uk

p1 Present address: Saudi Aramco, P.O. Box 2001, Dhahran 31311, Saudi Arabia

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