Inverse to normal magnetic fabric transition in an upper Miocene marly sequence from Tuscany, Italy

Abstract

The magnetic susceptibility fabric of an upper Miocene marly sequence exposed along the Morra creek (Tuscany, Italy) changes from inverse (maximum susceptibility axis sub-perpendicular to bedding) to normal from the bottom to the top of the section. The change is gradual, with the presence of anomalous magnetic susceptibility fabrics at some levels. The anhysteretic remanence anisotropy is always normal throughout the sequence. The changes in the magnetic fabric seem to be controlled by sedimentological variations, with the inverse susceptibility fabric related to the abundance of iron-bearing carbonates in the lower part of the section. In the upper part of the section subtle changes in the detrital inputs in the basin, and particularly a larger contribution of clayey and ferrimagnetic particles, turned the susceptibility fabric to a normal type.