Models of temperate carbonate deposition in Neogene basins in SE Spain: a synthesis

Abstract

Abstract Upper Miocene (Tortonian-Messinian) to Lower Pliocene (Zanclean) temperate bioclastic limestones occur in the Betic intermontane basins mixed with diverse proportions of siliciclastics. Components are mostly originally calcitic skeletons of invertebrates (especially bryozoans and bivalves) and coralline algae. Carbonate mud content is usually low and cementation is generally weak. These temperate carbonates formed in ramps. The depositional surface profile and local hydrodynamic conditions in each example controlled the occurrence of diverse facies at similar positions within the ramp. Shallow-water facies are well represented and formed in beaches and backshore lagoons, spits, rocky shores and submarine cliffs. Shoals developed seawards of shore deposits; the relatively quiet environments basinwards of the shaosl were the areas of maximal carbonate production (factory facies). The lack of early lithification favoured mobilization of skeletal particles. Waves and currents during storms transported carbonate grains landwards from the factory areas to shoals, spits and beaches. Skeletal grains were also transported downslope along the ramp. Re-deposited carbonates occur within basinal marls in submarine lobes and channels fed by channels cross-cutting and excavating the platform sediments. The absence of hermatypic corals and calcareous green algae in shallow-water deposits suggests cool surface water temperatures during carbonate formation. Large benthic foraminifers and oxygen stable isotope values indicate winter surface water temperatures of 16–17°C.