The Miocene sedimentary cover of the Mula-Gebas Basin: Internal-External Zone Boundary of the Betic Cordillera, South Spain

The Sierra Espu˜na and the Mula-Gebas intramontane basin, SE Spain, represent the Internal-External Zone Boundary (IEZB) of the eastern Betic Cordillera. The Miocene infill of this basin seals the IEZB and is mainly derived from the Internal Zone. This deposition is coeval with a Late Miocene volcanism. Therefore, the study of these sediments is crucial for the source-area provenance, sorting and recycling, paleoclimate, weathering, unroofing and tectonic processes, during the intramontane basins developing of the western peri-Mediterranean Chains. Sandstone detrital modes, and mineralogical and chemical compositions of mudrocks were arranged in two sedimentary cycles: (1) the middle Burdigalian-early Langhian, and (2) the middle Tortonian-early Messinian. The quartzolithic to feldspathic lithoarenites infer the erosion from a lithic-transitional recycled to transitional-quartzose recycled orogen, since low-medium grade metamorphic lithics and rare coeval volcanics with andesitic, andesitic-dacitic and rhyodacitic-rhyolitic sources are present. The mudrocks reveal a felsic (granitic-gneiss) source with a minor mafic input in the Upper Miocene. A shallow burial history and low thermal conditions (<~50 ◦C) has been also evidenced. Moreover, the paleoclimate changed from warm and/or wet during the Middle Miocene to cold/arid in the Late Miocene.