Discovery of an earliest Pliocene relic tropical fish fauna in a newly detected cliff section (Sabratah Basin, NW Libya)
A marine tropical fauna, which survived the Messinian salinity crisis in the Mediterranean Sea, was reported from several places in post-Messinian sediments in the northern Mediterranean area (e.g.Spain, Italy, Greece, and Cyprus). In North Africa knowledge about the marine post-Messinian is very limited. Here we present a unique diverse fish fauna, which was discovered along a steep cliff at the Mediterranean Sea between the cities of Tripoli and Al Khums. The fossil fish teeth and bones found together with other vertebrate remains are concentrated in a transgressive lag on top of an erosional unconformity, which is regarded to represent the Messinian event. The majority of fossils belong to teeth of selachians (24 species) and some large actinopterygians (at least 4 species). Less common are teeth and bones of reptiles and mammals. This fish fauna allows detailed evidences relating to stratigraphy, depositional environment as well as composition and evolution of the Late Neogene fish fauna. Furthermore, the composition of the fauna gives indication about the palaeoclimate of the early Pliocene and questions the complete extension of the marine fauna during the Mediterranean salinity crisis. In particular, the association of Carcharodon and Megaselachus is clearly indicative of early Pliocene age and proves for the first time the existence of early Pliocene (post-Messinian) deposits onshore western Libya. The presence of Hemipristis, Negaprion, Rhynchobatus and Aetobatus, known elsewhere in the late Miocene, but never clearly observed in Pliocene or younger deposits along the Mediterranean coasts, suggests that the fossiliferous bed is dated into the earliest Pliocene. The faunal assemblage is in favour of a high-energy nearshore depositional environment in a tropical to equatorial climate. The presence of numerous Indo-Pacific sharks and rays during the Zanclean indicates that numerous tropical selachians, inherited from the Palaeogene Tethyan Realm, may have survived in the Mediterranean a long time after the closure of communications with the Indian Ocean.
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Document Type: Research Article
Publication date: 2012-11-01
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