An Upper Devonian Limestone Slide Block near Marbella (Betic Cordillera, Southern Spain) and the Palaeogeographic Relations between Malaguides and Menorca

Abstract

Allochthonous Devonian limestone slide blocks are common in the Visléan to probably basal Namurian Retamares Member (lower Almogia Formation) of the Malaguides. The only slide block known from the coastal Palaeozoic between Fuengirola and Estepona is described from the Arroyo de la Cruz W of Marbella. This block is approximately 50 m in diameter and 11 m thick. Four stages of interna1 deformation prove its allochthonous nature. Deformation features and tectonic setting indicate a S to SE derivation. The block is of late Frasnian to early Famennian age. In terms of conodont zonation, it represents the Upper gigas Zone and the Middle Palmatolepis triangularis to Lower rhomboidea Zones, with the Uppermost gigas and Lower Pa. triangularis Zones missing. Pelagic mudstones predominate in rocks of the Upper gigas Zone, whereas fine-grained limestone turbidites, derived from lower slope environments or from intrabasinal rises, piredominate above the hiatus. Carbonate microfacies as well as conodont biofacies point to a deep-water deposition of all limestones. Concurrence of microfacies and biostratigraphy between the slide block and limestones pebbles from conglomerates of the Retamarerj Member prove a common source area. Microfacies and biostratigraphy of carbonate components known from Upper Devonian and post-lower- most Namurian conglomerates of Menorca show striking similarities to those of the Malaguides. Therefore, both limestone blocks and pebbles of the two realms are interpreted to have been reworked from different sectors of a single primary sedimentary basin. This interpretation points to closer palaeogeographic relations between the Malaguides and Menorca.