PALEOMAGNETIC DATA FROM UMBRIA (ITALY) - IMPLICATIONS FOR THE ROTATION OF ADRIA AND MESOZOIC APPARENT POLAR WANDER PATHS

Sixteen new Jurassic and Cretaceous paleomagnetic sampling sites are located in northern Umbria along three river valleys (Bosso, Burano, Sentino). The Late Jurassic and Early Cretaceous data are consistent in declination, but not inclination, with previously published data from these valleys. Early Jurassic data from eight sites give site mean declinations which are significantly different from the two site mean declinations of this age which were previously available. Comparison of the data with Cretaceous and Jurassic mean directions from the Southern Alps indicate 20-degrees anticlockwise rotation, relative to the Southern Alps, of this part of northern Umbria during Neogene deformation of the Umbrian fold and thrust belt. If the Umbrian mean directions are rotated to compensate for the tectonic rotation, the Early Jurassic and Cretaceous Umbrian and Southern Alpine pole positions coincide closely with a recently derived African apparent polar path (APWP), implying that Adria moved with Africa since at least Early Jurassic times. The Late Jurassic Umbrian and Southern Alpine poles, however, are not consistent with current APWPs and imply rapid apparent polar wander (in both African and North American coordinates) from high latitude to lower latitude between Bathonian and Oxfordian times.