JURASSIC AND CRETACEOUS PALEOMAGNETIC DATA FROM THE SOUTHERN ALPS (ITALY)

Jurassic and Cretaceous paleomagnetic data from 46 sites in the Venetian Alps, Trento Plateau and SE Lombardian Basin have been compiled. Nine of these site mean directions have been previously published. The sites can be divided into four age groups (Senonian, Hauterivian/Barremian, Kimmeridgian/Tithonian, and Callovian/Oxfordian). For three of the age groups, positive regional fold tests indicate (at the 99% confidence level) that the characteristic magnetization components predate the deformation. Structural mapping in the Venetian Alps allowed us to assign sites to individual thrust sheets, and we observe no significant relative rotation of thrust sheets in the nappe pile. Indeed, we observe remarkable consistency in mean direction throughout the entire sampling area for each of the four age groups. The Senonian and Hauterivian/Barremian pole positions lie close to coeval poles on African apparent polar wander paths (APWPs). This result is consistent with previous analyses of middle and Late Cretaceous data from the Venetian Alps. The new Jurassic poles deviate significantly from recently published African APWPs, reflecting either the poor definition of the African APWP in the Late Jurassic or about 200 anticlockwise rotation of the Southern Alps relative to Africa during Early Cretaceous time. The former of the two possibilities is favored by a new Late Jurassic/Early Cretaceous pole from North America, and by Early Permian paleomagnetic data from the Southern Alps which are consistent with coeval African data, implying that the movement of the Southern Alps was similar to that of Africa since Early Permian.