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

Abstract

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 Abstract 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 Kössen facies; (b) Lower Jurassic 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 Parauta Radiolarite Formation and associated limestones were studied with respect to stratigraphy, petrography, micropalaeontology (radiolarians, calcareous nanno-and microfossils) and facies. Radiolarite sedimentation occurred in the Middle Bathonian in a restricted and dysoxic deep Nieves basin, perched in the distal zone of a continental margin fringing the Tethyan ocean. This margin was adjacent to a young narrow oceanic basin between the South-Iberian margin and a continental block called Mesomediterranean Terrane. The Nieves basin was part of a marine corridor between the Proto-Atlantic and Piedmont-Ligurian basins of the Alpine Tethys. The regional tectonic position, the stratigraphical evolution since the Triassic, the age and the nature of the Mesozoic facies and the palaeogeographic relations to adjacent domains show striking analogies between the Betic Rondaide margin and coeval units of the Alps.

Exhumation of the Ronda Peridotite During Hyper‐Extension: New Structural and Thermal Constraints From the Nieves Unit (Western Betic Cordillera, Spain)

“…The Nieves Unit (Dürr, 1967) is composed of Tethyan carbonate platform deposits, including limestones, dolostones, marls and condensed pelagic successions of Norian to Cretaceous ages, completed by the Nava Breccia unconformably deposited on top of the sedimentary sequence (Blumenthal, 1933; Dürr, 1963, 1967; Martín‐Algarra, 1987; Martín‐Algarra et al., 1998; Martín‐Algarra & Estévez, 1984; O’Dogherty et al., 2001). The Nieves Unit has been traditionally linked to the evolution of the Internal Zones, as suggested by paleomagnetic data (Berndt et al., 2015; Crespo‐Blanc et al., 2016; Feinberg et al., 1996; Osete et al., 1988; Platzman et al., 1993; Platzman & Lowrie, 1992; Villasante‐Marcos et al., 2003; ) as the probable detached sedimentary cover from more internal units (Didon et al., 1973; Chalouan et al., 2008).…”

Structural record of Lower Miocene westward motion of the Alboran Domain in the Western Betics, Spain

“…Note that the subdivision in two units of the Alboran Domain is not relevant for Central and Eastern Betics where HP/LT units (e.g. Nevado-Filabride) with no equivalent in the Western Betics crop out below the Alpujarride(Platt et al, 2006) and where the Alpujarride does not contain mantle slivers.The Lower Western Alboran Unit is composed mainly by "Blanca" rocks that consist mainly of a gneissic basement locally migmatitic(Acosta-Vigil et al, 2014; Sánchez- Rodriguez, 1998) covered by Triassic marbles(Sanz de Galdeano and Andreo, 1995).Locally, tectonic slivers made of Triassic (dolomitic-) and Jurassic (cherty-) limestones(O'Dogherty et al, 2001), called Dorsale Units(Martín-Algarra et al, 2004a), underline the footwall of the Ronda Peridotites Thrust and the hanging-wall of the Gibraltar Thrust. At regional scale, these Dorsale Units underline the Gibraltar Thrust in both Betics and Rif…”