Palaeomagnetism of the Rogaland precambrian (southwestern Norway)

Abstract

Palaeomagnetic investigations were made on Precambrian rocks from Rogaland (southwestern Norway). Samples from anorthosite masses, a noritic layered intrusion and high grade metamorphic migmatites, together called the basement, revealed a similar “reversed” magnetization. This is explained by a simultaneous magnetization during uplift after the Sveco-Norwegian regeneration. The pole position calculated for the basement rocks is located at 36° S and 133° W. The age that can be assignated to this pole is 850–950 × 106 y. This is concluded from U/Pb determinations on zircons, K/Ar determinations on biotite and Rb/Sr determinations on biotite, microline and total rock. Dolerite dikes belonging to the Hunnedalen system revealed a “reversed” magnetization and a pole position at 34° S and 152° W, while dolerite dikes belonging to the Egersund system revealed a “normal” magnetization and a pole position at 22° S and 129° W. A correlation is made with other Precambrian poles from the Baltic Shield and Great Britain.