Polarity Zones and Apparent Polar Wander at the Jurassic /Cretaceous Boundary in the Southern Alps, Italy

The magnetic and nannofossil stratigraphies of several sections spanning the Jurassic/Cretaceous (J/K) boundary have been studied in the Lombardian Basin (Torre de Busi, Colle di Sogno) and Trento Plateau (Colme di Vignole, Foza). The magnetic stratigraphies span the CM16R (late Berriasian) to the CM22 (Kimmeridgian/Tithonian boundary) interval corresponding to the 138-150 Ma interval spanning the J/K boundary (142 Ma). In Lombardy, the facies transition from "Rosso ad Aptici" (siliceous limestone) to Maiolica (pelagic limestone) occurs in the latest Tithonian (CM19N-CM20N), just prior to the J/K boundary, closely synchronous with the transition from Rosso Ammonitico to Maiolica on the Trento Plateau. The identification of polarity zones is based on polarity-zone pattern fit, and the previously established correlations of polarity chrons to nannofossil events/zones. The apparent polar wander path (APWP) for each section is calibrated based on the magnetic stratigraphy and lies close to an estimated African APWP of the same age, implying very little rotation of the Lombardian and Trento plateau regions of the Southern Alps relative to Africa since latest Jurassic time. Our objective is to produce a calibrated APWP (polar wander by polarity chron), and thereby improve the definition of the Adria APWP in this interval of relatively rapid apparent polar wander.