Original paper

Peperite development in a Miocene-age carbonate succession, Cabo de Gata volcanic area (Agua Amarga/Carboneras basins), SE Spain – The Bréche Rouge revisited

Biber, Jani Leyla; McCann, Tom

Abstract

The Miocene-age Agua Amarga and Carboneras basins, SE Spain, contain an unusual lithological assemblage, termed the Bréche Rouge, and comprising fractured andesitic cryptodomes, associated breccias and a fossil-rich volcaniclastic conglomerate and related calcarenite. The cryptodomes are crisscrossed by a series of fractures and veins infilled with brecciated material, the clasts of which often show well-preserved jigsaw textures, as well as evidence of fluidal and subplanar margins. Surrounding the breccia clasts were three different matrix types, namely a red floatstone/rudstone containing fossils (predominantly solitary corals), as well as pink and orange mudstones. Together, these lithologies are interpreted as resulting from in-situ peperitisation at the top of the cryptodomes and related mass flows, generated as a result of volcanic activity in a submarine setting. The evolution of the succession can be explained in terms of a two-stage model. Stage 1 (pre-Carboneras volcanic stage) comprised the deposition of calcarenites, often interbedded with volcaniclastics and possible bentonites. The volcanic products were derived from the S, SE and E, although it is possible that some of the material was also derived from areas to the N of the Carboneras region. Stage 2 (Carboneras volcanic stage) was characterised by volcanic activity forming massive andesites, and the related intrusion of the andesites into wet and/or unconsolidated carbonate sediments resulting in peperite development. In the Carboneras area mass flows were generated and flowed southwards into the Agua Amarga Basin.

Kurzfassung

Die miozänen Becken, Agua Amarga und Carboneras (SE-Spanien), zeigen eine besondere sedimentologisch-vulkanische Einheit, welche aus einem fragmentierten Andesit und damit assoziierten Brekzien, so wie aus einem fossilreichen vulkanoklastischen Konglomerat aufgebaut ist. Zusammenfassend werden diese Einheiten als In-situ-Peperit mit assoziierten Massenstromablagerungen interpretiert, welche als Folge von subvulkanischen Intrusionen entstanden. Die Entwicklung der Abfolge wird durch ein zweiphasiges Model erklärt. In Phase 1 (Prä-Carboneras) treten Sedimente hauptsächlich als Kalkarenite in Wechsellagerung mit Vulkanoklasten (S, SE und E, möglich auch aus N) und Bentoniten auf. Phase 2 (Syn-Carboneras) ist charakterisiert durch submarine vulkanische Aktivität und damit einhergehender Bildung von Peperiten und Massenströmen.

Keywords

agua amarga basinandesitecarboneras basinmass flowsvolcaniclastics