Magnetic minerals in Pliocene and Pleistocene marine marls from Southern Italy : rock magnetic properties and alteration during thermal demagnetization

Abstract

The rock magnetic properties of two different Pliocene to Pleistocene marine marls from southern Italy are studied. Different conditions during sedimentation have led to two completely different magnetic mineralogies in these marls. Chapters 2, 3 and 4 examine the rock magnetic properties of the Early Pliocene marine marls of the Trubi formation sampled at Eraclea Minoa in the Caltanissetta basin on southern Sicily (photo 1). These pelagic marls are characterized by a high carbonate content (60-80%), a sedimentation rate of 4-5 cm/ky and a cyclic lithology related to the Earth's orbital cycles. Magnetite is the primary remanence carrier in the Trubi marls. In chapters 5, 6 and 7 rock magnetic results for the Late Pliocene-Early Pleistocene marine marls of the Vrica section are presented (photo 2). The Vrica section is the Pliocene-Pleistocene boundary stratotype, situated in the Crotone-Spartivento basin of northern Calabria. The marls were deposited in shallower water with a sedimentation rate between 25 and 50 cm/ky and they have a carbonate content of only 15-25%. In these marls the climatic fluctuations caused by the Earth's orbital cycles are expressed as frequently occurring sapropelitic layers. Magnetic sulphides are the main magnetic minerals in the Vrica marls.