Triassic redbeds in the Malaguide Complex (Betic Cordillera - Spain): petrography, geochemistry and geodynamic implications

Sandstone petrography and mudstone mineralogy and geochemistry of Triassic mudstones and sandstones from continental redbeds of the Malaguide Complex (Betic Cordillera, southern Spain) provide useful information on provenance, palaeoclimate and geodynamics during the early stages of the Pangea break-up, and on their diagenetic evolution. The sandstones are quartzarenites to sublitharenites, with minor lithic fragments and rare feldspars. The mudstone samples show a uniform elemental distribution relatively to the Post-Archean Australian Shale. The samples likely record recycling processes from their metasedimentary basement rocks that significantly affected the weathering indices, and monitors cumulative effects, including a first cycle of weathering at the source rocks. Sandstone composition, and chemical-mineralogical mudstone features testify a provenance from continental block and recycled orogen weathered under warm and episodically wet climate. Source areas were located towards the east of the present-day Malaguide outcrops, and were formed by fairly silicic rock types, made up mainly of Palaezoic metasedimentary rocks, similar to those of the Paleozoic underlying serie, with subordinate contribution from magmatic-metamorphic sources, and rare supply from mafic metavolcanic rocks. Clay-mineral distribution of mudstones is dominated by illite and illite/smectite mixed-layer and results of both provenance and weathering plus differences in burial/temperature history. Illite crystallinity values, illitization of kaolinite, occurrence of typical authigenic minerals and apatite fission-track studies, coupled with a subsidence analysis of the whole Malaguide succession suggest burial depths of at least 4-6 km with temperatures of 140-160°C, typical of the late diagenetic stage, and confirm the middle Miocene exhumation of the Betic Internal Domain tectonic stack topped by the Malaguide Complex.