Evidence for an incipient early Caledonian (Cambrian) orogenic phase in southwestern Norway

• Published in: Geological Magazine
• Main Authors: Furnes, H., Austrheim, H., Amaliksen, K. G., Nordas, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1983
• Subjects: Geology; Norway; Northern Norway
• Online Access: http://dx.doi.org/10.1017/s0016756800027758; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756800027758

Summary . Quartz-keratophyres from an ensimatic island arc on Bømlo, southwest Norwegian Caledonides, resting on the Lykling ophiolite, have yielded a Rb/Sr whole rock age of 535 ± 46 Ma. This Cambrian age, which is a minimum age of formation for the ophiolite, indicates an early phase of subduction, corresponding with the orogenic activity known from northern Norway, i.e. the Finnmarkian. Before Middle Ordovician time, the ophiolite and ensimatic arc had been obducted onto continental crust and deformed, as they are unconformably overlain by a volcanic complex of subaerial rhyolites and andesites which have yielded Rb/Sr whole rock ages of 464 ± 16 and 468 ± 23 Ma respectively.