The Betic Cordillera of southern Spain represents an upliftedforeland fold–thrust belt. Source rock types of the Betic Cordillerainclude metamorphic (mainly phyllite, schist, quartzite, andgneiss), sedimentary (siliciclastic and carbonate), volcanic (felsic to intermediatepyroclasts), and mantle-derived (peridotite, gabbro, serpentinite,and serpentine schist) rocks. The fluvial systems range that transectthe Betic Cordillera are the major detrital source of sedimentalong the southern Spanish coast, supplying sand to beaches and offshoredepositional systems in the Alboran Sea basin.Three key sand petrofacies derived from the Betic mountain beltreflect the main clastic contribution of known source rocks. All thesands are quartzolithic, ranging from quartz-rich to lithic-rich.Fluvial systems draining the Sierra de Los Filabres, the Sierra Nevada,the Sierra de Gador, and the Ma´laga Mountains, and their relatedbeaches constitute a metamorphic–sedimenticlastic quartzolithicsand petrofacies (Qm34610 F463 Lt6269; Lm72614 Lv264Ls26613), derived dominantly from the Nevado–Fila´bride, Alpuja´rride,and Mala´guide complexes. This quartzolithic petrofacies extendsfrom northeast of Almeria to Torremolinos (southwest of Ma´laga), andnortheast of Algeciras. Only one beach sand sample, east of Cabo deGata, is volcanolithic. Volcanic detritus (mainly having felsitic textures)is derived from Miocene (15–7 Ma) pyroclastic sequences cropping outin the southeast of the chain.This metamorphic–sedimenticlastic quartzolithic petrofacieschanges in the coastal stretch from Torremolinos to Marbella,where drainage systems cut across the Serrania de Ronda. Heresource rock types include peridotite, gabbro, and serpentinite of theRonda Peridotite Massif, and metamorphic rocks of the Ma´laguideand Alpuja´rride units. The fluvial and beach sands of this area arequartzolithic (Qm32612 F1063 Lt58611), and include abundantperidotite and serpentinite grains. The latter quartzolithic petrofacieschanges abruptly from Algeciras to Ca´diz, where the sandbecomes quartz-rich (Qm7765 F462 Lt1964). This sand petrofaciesis derived predominantly from recycling of sedimentary sequences,mainly the quartzarenite turbidite units of the GibraltarArc (the Algeciras Flysch). This petrofacies is characterized byhigher proportion of quartz grains and abundant sedimentary lithicfragments (Lm163 Lv161 Ls9863).The three onshore petrofacies plot in the recycled-orogen provenancecompositional field and the lithic to transitional to quartzoserecycled subfields of Dickinson (1985). They vary from lithic, to transitionaland quartzose depending on their source lithologies in the Beticforeland fold–thrust belt. These actualistic petrofacies best describe thenature and distribution of sand petrofacies derived from a collisionalfold–thrust belt where primary and recycled source rocks are interfingered.Deep-marine turbidites of the Alboran Basin have basinwidequartzolithic sands having close compositional relations with BeticCordillera onshore sand petrofacies. Comparison of detrital modes from mainland to deep-marine environments provides a suitablebasis for interpreting the Miocene to Pleistocene sand dispersal historyin the Alboran Basin. These modern quartzolithic petrofaciesare used to interpret analogous ancient collisional sandstone petrofaciesof the Alpine orogenic belt of the western-central Mediterraneanregion and of other collisional orogenic systems, as a broaderpoint of view.
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|Titolo:||The recycled orogenic sand provenance from an uplifted thrust belt, Betic Cordillera, southern Spain|
|Data di pubblicazione:||2003|
|Appare nelle tipologie:||1.1 Articolo in rivista|