Lower Cretaceous magnetic stratigraphy in Umbrian pelagic limestone sections

The magnetic stratigraphy of the Lower Cretaceous, pelagic Maiolica limestone has been investigated in three partially correlative sections at Gorgo a Cerbara, Presale and Frontale in the northern Umbrian Apennines of central Italy. The white, well-bedded limestone has a magnetic mineralogy dominated by magnetite. Stable magnetic directions isolated by thermal demagnetization define alternating polarity zones in each section. The magnetozone patterns are distinctive and can be correlated with the geomagnetic reversal history derived from the M-sequence marine magnetic anomalies. The three new sections confirm the polarity sequence for anomalies M0 to M10N. Although the Maiolica is inadequately dated, the correlated anomalies, together with the results of other investigations, allow tentative associations of anomalies M0–M19 with individual stages in the Lower Cretaceous and Upper Tithonian.The investigations also demonstrate the usefulness of magnetic stratigraphy in basin analysis. They yield mean sedimentation rates, confirm that there is a hiatus between the base of the Presale section and the underlying Jurassic formations, and show that a large part of the Frontale section has been cut out by faulting.