A paleomagnetic investigation of Permo-Tiiassic red beds and andesites from the Spanish Pyrenees

Abstract

Fourteen samples of Permo-Triassic andesites and eight samples of Permo-Triassic red beds were collected in the upper Aragon Subordan valley (province of Huesca, Spanish Pyrenees). The measurements were done with an astatic magnetometer, and ac demagnetization was applied to test for stability. The sediments acquired a strong, stable magnetization in post-Alpine times; the original direction of magnetization could not be detected. The magnetic directions of the andesites, on the other hand, probably are caused by thermoremanent magnetism. The pole position is 133°W, 51°N, which differs by about 60° from the mean value of Permian poles determined in northern and central Europe. The best explanation for the difference in the location of the Pyrenean pole and north European pole positions seems to be that there was a northwesterly drift of the western Pyrenees in post-Permian time. Similar results from the Spanish Pyrenees and the Italian Alps suggest that the part of the crust involved in this drifting extended from at least the western Pyrenees to the Italian Alps.