Ferruginous paleosols around the Cretaceous-Paleocene boundary in central-southern Sardinia (Italy) and their potential as pedostratigraphic markers

摘要

The properties of seven ferruginous paleosols, formed in alluvial continental deposits of Upper Cretaceous-Paleocene age in central-southern Sardinia (Italy), were examined to understand their genesis. Particular attention has been addressed to their paleoenvironmental and paleogeographic significance, also in comparison with similar paleosols in southern France, and to their potential to represent good pedostratigraphic markers for a larger area. The paleosols are characterized by petroplinthic, pisoplinthic, plinthic or pisolithic horizons. Their genesis started under a warm and humid tropical climate, with distinct wet and dry seasons, of the Latest Maastrichtian-Lower Paleocene and continued, under increasingly dry conditions, during the Middle to Upper Paleocene. The major differences that occur among the paleosols can be related to differences in geomorphic position, parent material characteristics and drainage conditions. The pisolithic paleosols of central-southern Sardinia show a structure and composition comparable to those of the coeval ones in southern France, which were formed under similar climatic conditions. On the basis of the constant stratigraphic position, the large geographic extent and the supposed former lateral continuity, the studied ferruginous paleosols can be considered to be a good pedostratigraphic marker in central-southern Sardinia and in southern France and are informally named as the "Monte Maraconis geosol". This allows extensive chronostratigraphic correlations as well as regional-scale morphostratigraphic correlations and represents, with its typical pedofacies, a pedostratigraphic unit worthy of consideration in future regional geological mapping.