Palaeomagnetic Studies in the British Caledonides-III Igneous Rocks of the Northern Lake District, England

Palaeomagnetic results are reported from the ‘northern’ Borrowdale Volcanics and from the Carrock Fell intrusive complex. The mean stable remanence direction in the volcanics is D = 0°, I = −46° (α95 = 6°) from 27 sites after allowing for tectonic dip. This result is supported by a decisive fold test in which precision improves by at least a factor of 3. The Carrock Fell Gabbro complex carries magnetization which is best interpreted as originating in Ordovician times when the complex was intruded as a dyke-sheet which has been subsequently only slightly warped. On this basis D = 350°, I = −22°, k = 11.7 from 11 sites. A corollary of this interpretation is that the ‘northern’ Borrowdale Volcanics were folded before the emplacement of the Carrock Fell Complex. All these data are based on partial AF demagnetization. All sites have the same polarity. The corresponding palaeomagnetic pole positions are Lat. = 7° N, Long. = 177° E, dψ = 5°, dχ = 8° and Lat. = 22° N, Long. = 188° E, D = 8°, dχ = 15° respectively. These are in good agreement with other British Ordovician data.