The role of topography and erosion in the development and architecture ofshallow-water coral bioherms (Tortonian–Messinian, Cabo de Gata, SE Spain)

During the Miocene, Mediterranean shallow-water carbonates were rich in scleractinian corals, which thrivein various depositional settings. A Tortonian–Messinian bioherm belt developing in a heterozoan-dominatedramp was investigated along a 1.2 km continuous transect located in the Cabo de Gata region. The intervalstudied displays four depositional environments from mid-to-inner ramp, dominated by swell waves andstorm energy, deposited as a single, large-scale depositional sequence during a 3rd to 4th ordertransgressive–regressive cycle. The bioherms grew in three phases, and were essentially composed of inplaceprimary frameworks. Three coral genera were the main framebuilders (Porites, Tarbellastrea and rareSiderastrea), associated with melobesioid and mastophoroid red algae and bryozoans as secondaryframebuilders. The corals display five morphotypes, from a fast-growing branched type to slow-growingdomal to plate morphologies, with an uncommon form of mesh Porites as the dominant morphotype.Changes in coral morphotype and composition of micro-encrusters communities reveal changes inhydrodynamics, detrital influx and perhaps nutrient levels. Bioherms architecture was driven by sea level,palaeotopography and erosion. The coral framework was affected during its development by erosion surfacesmetres to tens of metres deep and hundreds of metres wide. Unexpectedly, these surfaces are betterdeveloped on the inner edges of the bioherms. This could indicate the circulation of strong bottom currentsbetween the volcanic palaeohighs and the synoptic relief created by the buildups. Finally, a major sub-aerialerosional episode associated with increasing detrital influxes, ended bioherm development, thus allowingthe colonization of the dead coral substratum by red algae.