Unravelling hinterland and offshore palaeogeography from pre-to-syn-orogenic clastic sequences of the Betic Cordillera (Sierra Espuña), Spain

The Malaguide Complex (Betic Cordillera) occurs in the Sierra Espuña area (SE Spain) providing a favorable settingto study a sedimentary successions from continental and shallow-marine to deep-marine environmentsusing structural and stratigraphic relations, and petrological and geochemical signatures. The aim of this workis to outline the sedimentary evolution of theMalaguide Complex and the El Niño Fm. This succession is arrangedinto pre-orogenic (Paleocene-Early Oligocene) and syn-orogenic (Late Oligocene-EarlyMiocene) stages. The detritalmodes of sandstones of the overall succession are heterogeneous and indicate a multi-source area, markedby exhumation till an unknown Malaguide basement and probably lower units of the Internal Betic Zone (e.g.Alpujarride Complex) in the case of the El Niño Fm. Pre-orogenic deposits are mainly carbonate with abundantskeletons of intrabasinal to extra-basinal larger foraminifera, calcareous lithic fragments and quartz grains, andmetamorphic lithic fragments. Minor metamorphic lithic fragments occur in the Eocene deposits (i.e. EspuñaFm). Calcareous lithic fragments and extra-basinal fossils (lithoclastic bioclasts) are mostly present in the EarlyOligocene pre-orogenic formations (i.e. As Fm) and were derived from the Paleocene-Eocene sedimentary successionsof the Malaguide Complex. Syn-orogenic sandstones are quartzolithic with abundant metamorphicand sedimentary lithic fragments (slate, phyllite, fine-grained schist, ooidal grainstone, mudrock and quartzrichsiltstone fragments). Sedimentary lithic fragments were derived from the Mesozoic successions of theMalaguide Complex while metamorphic detritus is related to theMalaguide basement (probably also Alpujarridefrom Burdigalian on) that was exhumed starting from the Late Oligocene.Mudrocks of the syn-orogenic clastics,record an increase of phyllosilicate, quartz and feldspars and an abrupt decrease in calcite and dolomite. Theabundance of calcite and dolomite, and traces of hematite occur dominantly in the pre-orogenic mudrocks.The geochemical signatures suggest a provenance mostly derived from felsic source rocks with a minor supplyfrom mafic metavolcanic rocks in some samples of the syn-orogenic stage. The syn-orogenic formations (i.e.Rio Pliego Fm and El Niño Fm) are characterized by higher Cr/V values than the pre-orogenic formations suggestinga mafic supply for the syn-orogenic samples. In particular, the contents of Cr (average=85 ppm) and Ni (average= 48 ppm) for the samples of the Rio Pliego and El Niño Formations are higher than those samples (Craverage = 20 ppm; Ni average = 14 ppm) of the pre-orogenic formations. Palaeoweathering indices suggestlow to moderate weathering conditions for the source area(s). The Cenozoic studied succession played a keyrole in the geodynamic evolution of the Betic Cordillera, representing the key tectonic element of the westernMesomediterranean domains.