Coralline algae (Corallinales, Rhodophyta) in western and central Mediterranean Messinian reefs

Abstract

Coralline algae are common components in Messinian reefs in the Sorbas Basin in SE Spain and in the Salento Peninsula (southern Italy). They occur encrusting coral skeletons and other bioclasts, forming rhodoliths, and as fragments in back-reef, reef-framework, and proximal-to-middle slope facies. Corallines also occur in Halimeda boundstones associated to coral reefs. In contrast, no coralline algae have been recorded in the fine-grained distal slope deposits in both areas and in lagoonal marly limestones in Salento. The relative abundance of corallines in reefs and their species richness is significantly higher in the Salento platform than in the intermontane Sorbas Basin, which was affected by terrigenous influx. Neogoniolithon brassica-florida and Spongites fruticulosus dominate the shallow-water assemblages; Lithophyllum records peak at the base of reef-core and upper-slope deposits (around 20 m palaeodepth) and Phymatolithon calcareum and species of Lithothamnion are most abundant in deeper slope facies. The main components of the Messinian Mediterranean reef coralline assemblages are extant species, common in the Mediterranean and along the north Atlantic coast from Morocco (and the Canary Islands) to the British Islands. A few, such as Spongites fruticulosus and Phymatolithon calcareum, have been living in the Mediterranean region for more than 25 Ma. Four species still live in the Indo-Pacific but disappeared from the Mediterranean during the Messinian Salinity Crisis. The typical components of present-day Indo-Pacific coral reefs do not occur in the Mediterranean Messinian reefs. The ‘Mediterranean–Atlantic’ character of the Messinian reef corallines reflects the decrease in tropical biotas in the Mediterranean throughout the Miocene, probably related to global cooling and isolation of the Mediterranean from the Indian Ocean since the Middle Miocene.