The Middle Jurassic radiolarites and pelagic limestones of the Nieves unit(Rondaide Complex, Betic Cordillera): basin starvation in a rifted marginal slope of the western Tethys

Middle Jurassic radiolarites and associated pelagic limestones occur in the Rondaide Nieves unit of the Betic Cordillera, southern Spain. The Rondaide Mesozoic includes: (a) a thick succession of Triassic platform carbonates, comparable to the Alpine Hauptdolomit and Kossen facies; (b) Lower Jurassi c pelagic limestones comparable to the Alpine Hierlatz and Adnet facies; (c ) the Middle Jurassic Parauta Radiolarite Formation, described herein; and (d) a thin Upper Jurassic-Cretaceous condensed limestone succession. The Pa rauta Radiolarite Formation and associated limestones were studied with res pect to stratigraphy, petrography, micropalaeontology (radiolarians, calcar eous nanno- and microfossils) and facies. Radiolarite sedimentation occurre d in the Middle Bathonian in a restricted and dysoxic deep Nieves basin, pe rched in the distal zone of a continental margin fringing the Tethyan ocean . This margin was adjacent to a young narrow oceanic basin between the Sout h-Iberian margin and a continental block called Mesomediterranean Terrane. The Nieves basin was part of a marine corridor between the Proto-Atlantic a nd Piedmont-Ligurian basins of the Alpine Tethys. The regional tectonic pos ition, the stratigraphical evolution since the Triassic, the age and the na ture of the Mesozoic facies and the palaeogeographic relations to adjacent domains show striking analogies between the Betic Rondaide margin and coeva l units of the Alps.