Fission-track dating of apatite, zircon and sphene, and K-Ar dating of K-feldspars in samples taken from a transect across the Møre-Trøndelag Fault Zone in Trøndelag confirm the long-lived nature claimed for this complex fault zone. Apatite, zircon and sphene, which have blocking temperatures of 125° ± 25°C, 200° ± 50°C and 250° ± 50°C, respectively, together indicate a complex history of post-Caledonian tectonism. Uplift and cooling are indicated in Early Palaeozoic (Late Ordovician-Early Carboniferous) and Triassic-Jurassic times, with erosion of at least 3 km of Early and possibly Late Palaeozoic supracrustal cover since the Late Palaeozoic. Late Jurassic activity is indicated along the Verran Fault.

A. Grønlie*  & B. A. Sturt, Norges Geologiske Undersøkelse, Postboks 3006, N- 7002 Trondheim, Norway;
C. W. Naeser & N. D. Naeser, US Geological Survey, P.O. Box 25046, Denver Federal Center, Denver, CO 80225, USA;
J. G. Mitchell, Department of Physics, The University, Newcastle upon Tyne NEI 7RU, England;
P. R. lneson, Earth Sciences Unit, University of Sheffield, Sheffield SJ 7HF, England.

*Present address: Statoil Nord-Norge, Postboks 40, N-9401 Harstad, Norway.