Paleomagnetism of some Late Paleozoic and Triassic rocks from the eastern Lombardic Alps, Italy

Abstract

The directions of magnetization of five volcanic units of the Late Paleozoic rock sequence from the Eastern Lombardic Alps, each sampled at one site, display small within unit dispersion and rather large between-unit dispersion. They yield a mean direction of D = 135°, I = -21° (α95 = 20°), which is as divergent from the Late Paleozoic paleomagnetic field in the Alpine Foreland as the directions of contemporaneous rocks in other places in the Southern Alps. The characteristic magnetization direction of the Middle Triassic porphyrite of Valle di Scalve is D=161°, I=-21°. It is remarkably similar to the Late Paleozoic results and rather different from other Triassic paleomagnetic directions from the Southern AIps. Both the Late Paleozoic and the Triassic paleomagnetic directions indicate a counterclockwise rotation of the Southern AIps with respect to the Alpine Foreland (about 50°). There is no clear paleomagnetic evidence of large translational megatectonic movements between the Southern Alps and the Alpine Foreland.