Coralline algae as depth indicators in the Miocene carbonates of the Eratosthenes Seamount (ODP Leg 160, Hole 966F)

Abstract

The abundance of the major coralline algal groups has been investigated and quantified in the coralline-rich facies of the Miocene shallow-water carbonates of the Eratosthenes Seamount (eastern Mediterranean, off-shore Cyprus). The analysis is based on the quantification of the most easily-recognizable groups of coralline algae in order to provide a user-friendly approach for palaeobathymetric reconstructions. Coralline algal distribution through the core suggests water depth estimates generally similar to those based on the composition of the skeletal assemblage and the benthic foraminiferal association in particular. The only noticeable difference occurs in the rhodolith and coral facies, where algal distribution suggests deeper waters than those indicated by benthic foraminifera. The distribution pattern of the major groups suggests that the ratio between Hapalidiales and Corallinales is the most reliable indicator of water-depth. The comparison with other models available in literature highlights a general zonation useful for the study of tropical, middle to late Miocene oligotrophic carbonates. Very shallow settings (0–20m) are overwhelmingly dominated by Corallinales; in slightly deeper settings (20–40m) Hapalidiales are more abundant, especially if the sea-floor is shaded (for example by a macrophyte canopy). Between 40 and 60m, Hapalidiales dominate but Corallinales are still common, while below 60m Corallinales are very rare. In non-oligotrophic environments this zonation is not reliable and, due to the reduced water clarity related to the high primary productivity, Hapalidiales clearly dominate even in very shallow settings.