Late Miocene biota from the Abad Member of the Carboneras-Nijar Basin (Spain, Andalusia): A bathyal fossil assemblage pre-dating the Messinian salinity crisis

Abstract

Marly sediments of the early Messinian Abad Member of the Turre Formation from the northeastern sector of the Carboneras-Nijar Basin (southern Spain) have yielded a rich fossil assemblage, of which 60 taxa are documented herein. Besides nannoflora and microfauna, this assemblage includes the first autochthonous macrofauna described from the Abad Member. Based on the calcareous nannofossil assemblage, in particular the occurrence of the zonal index taxon Amaurolithus primus, the sediments are assigned to the Mediterranean calcareous nannofossil zone CNM17, corresponding to the latest Tortonian to earliest Messinian interval. This matches the age range generally reported for the Abad Member. Palaeoecological evidence from calcareous nannofossils (20 autochthonous taxa), planktic and benthic foraminifera (12 taxa), Porifera (3 taxa), Octocorallia (Keratoisis), Serpulidae (4 taxa), Bivalvia (5 taxa), Gastropoda (2 taxa), Brachiopoda (7 taxa), Cirripedia (Faxelepas) and Vertebrata (5 taxa) indicates an upper bathyal environment with an influx of neritic elements for the Abad Member near Carboneras. Additionally, several faunal components may represent allochthonous/parautochthonous elements from adjacent habitats, which were transported into the deep marine setting by turbiditic mass flows. Although similarities exist, the fossil assemblage from the marls is compositionally significantly different from the biota previously documented from a nearby exposed olistostrome, the ‘red breccia’. Similar fossil assemblages from the Mediterranean have so far mainly been reported from the Pliocene-Pleistocene of southern Italy and Greece. The Carboneras fauna thus adds to our knowledge of the development of these habitats and their biota prior to the Messinian salinity crisis. Beyond the novel palaeoenvironmental data, the range of the dyscoliid brachiopod Ceramisia meneghiniana, previously known only from the Pliocene of Italy, is extended to the Miocene of Spain. The cirripede crustacean Pycnolepas paronai De Alessandri, 1895 is transferred to the hitherto monospecific genus Faxelepas Gale, 2015, whereby the range of the latter (previously Maastrichtian to Danian) is extended to the late Miocene.