Jurassic magnetic stratigraphy from Umbrian (Italian) land sections

The Umbrian Apennines were the site of pelagic sedimentation throughout most of the Jurassic. Magnetic stratigraphy from four sections spanning many of the Jurassic stages indicates that the geomagnetic field at this time was characterized by two intervals of mixed polarity, separated by an interval of predominantly normal polarity corresponding to the Jurassic “quiet-zone” in the oceanic magnetic anomaly record. Unfortunately, ammonites are poorly preserved or absent throughout most of these sections; the duration of this “quiet-interval” cannot be well defined, although it is probably restricted to the Callovian and Oxfordian stages.