Guild structure and aggradation pattern of Messinian Porites patch reefs: ecological succession and external environmental control (San Miguel de Salinas Basin, SE Spain)

Abstract

Small and isolated Messinian patch reefs showing a typical internal succession and an oligospecific reef-building community are described from the western margin of the San Miguel de Salinas Basin (SE Spain). These thrived in a mixed carbonate -siliciclastic environment and are known from two different stratigraphic levels. The reef growth is characterized by a shallowing-upward sequence and can be subdivided into four divisions: reef debris zone; coralline algal zone; branching coral zone; and reef crest zone. This ecological succession. of Messinian reefs reflects an increasing water turbulence and the accommodation of the reef-building organisms to shallower-water settings, which is conditioned by its own upward growth. The start of reef growth is controlled by a reduced influx of terrigenous deposits, which derived from fan sediments reworked by waves. The reefs were killed by smothering with quartzose calcarenites. The low diversity of the reef-building community indicates an arrested ecological succession without climax stages, controlled by sedimentation rate and siliciclastic supply. A salinity increase can be excluded, because the reef-associated fauna indicates normal-marine conditions during reef growth. There is no evidence for subaerial exposure of the reefs during the formation of evaporites at the end of the Messinian.