Recognizing maximum flooding surfaces in shallow-water deposits: An integrated sedimentological and micropaleontological approach (Crotone Basin, southern Italy)

Abstract

The Pliocene and Pleistocene intervals of the Neogene to Quaternary succession of the Crotone Basin, southern Italy, offer good examples of shallow-marine high-frequency sequences (fourth-order or lower rank stratigraphic frameworks) composing higher-rank units. The analysis of some representative sections from this succession has allowed performing an integrated sedimentological and micropaleontological study aimed at defining new criteria to recognize high-frequency maximum flooding surfaces. In particular, field data have been compared with some parameters derived from the micropaleontological analysis, such as the abundance, diversity and % fragmentation of benthic foraminifera, as well as the ratio between distal and proximal benthic foraminifera species and the plankton/benthos ratio. This integrated study allows to define an uncertainty interval in the high-frequency sequences, in which the maximum flooding surface should lie. This uncertainty interval is usually characterized by lower values of the % fragmentation and higher values of the abundance, diversity and distal/proximal ratio, whereas the peak of the plankton/benthos ratio allows to define a surface of maximum water depth, placed above the maximum flooding surface. Usually, the greater the magnitude of the transgression, the thinner the uncertainty interval. These results highlight the cryptic nature of the maximum flooding surface within condensed sections, even in high-resolution outcrop studies, and allow to refine the criteria based on which the position of such surface can be approximated in the field and in sediment cores.