Paleomagnetism of Upper Carboniferous limestones from the Carnic Alps

Abstract

Limestones of Stephanian age belonging to the Carboniferous-Permian sedimentary sequence of the Auernig Group at Passo Pramollo (Carnic Alps) were investigated by a paleomagnetic study. These limestones represent the late-tectonic molassic stage of the Hercynian orogeny in the Paleozoic chain of the Carnic Alps. After a preliminary sampling at twenty sites, unstable magnetization was found to affect the remanence at eight sites. Of twelve sites studied in detail (about 180 specimens), 10 sites had a mean paleomagnetic direction of D = 141.8° and I = −8.1°, and α 95 = 17.8° after cleaning and corrections for bedding attitudes tilted by subsequent, mainly Alpine tectonics. The corresponding virtual mean pole position lies at 243.3°E, 36.2°N, coincident with data of comparable age from Morocco, and is located east of the African poles of Late Carboniferous to Permian age. In addition, the pole from the Pramollo limestones is also comparable with the younger Permian poles from the Southern Alps and from most Mediterranean crustal blocks, showing that the area was also rotated counterclockwise with respect to Europe. Paleogeographically, the area of the Carnic Alps already belonged to the Southern Alpine domain by Upper Carboniferous times, and was located in the Northern Hemisphere at that time.