Foraminiferal stratigraphy and palaeoecological implications in turbidite-like deposits from the Early Tortonian (Late Miocene) of Greece

Abstract. The Lower Tortonian Ag. Giannis section, in Gavdos Island, Greece, consists of an outer neritic to upper bathyal, marly hemipelagic sequence which is interrupted by thick turbidite-like sandy deposits. During deposition of the marly intervals, reworking was considerably reduced.

This paper contributes to knowledge concerning benthic foraminiferal response to dynamic sedimentary environments. Important palaeoecological information for benthic foraminiferal assemblages was gathered and analyzed in order to create a regionally consistent picture of the palaeoenvironment. Samples were analyzed statistically in order to identify the different palaeoenvironmental settings during turbiditic sedimentation. Undisturbed basal marls of the section are characterized by the predominance of a diversified Uvigerina striatissima assemblage typified by a broad variety of morphotypes with different inferred habitat preferences and feeding strategies, indicating rather well-oxygenated bottom waters. This environmental stability was subsequently disrupted by recurrent deposition of turbidite-like sands. A low-diversity Valvulineria complanata-Globobulimina sp. assemblage is dominant in this part of the succession, as these specialized endobenthic species could keep pace with high-energy sedimentary settings. Just above the turbidites, a “recolonization” fauna (Bolivina alata assemblage), composed entirely of infaunal elements is observed, indicating a nutrient-rich substrate. This oligotypic fauna is later replaced by a more diversified microfauna capable of occupying a wider range of ecological niches.