Early Pliocene molluscs from the easternmost Mediterranean region (SE Turkey): biostratigraphic, ecostratigraphic, and palaeobiogeographic implications

Abstract

The mollusc faunas from Pliocene deposits of the Hatay-İskenderun region were investigated at nine localities andcomplemented with three localities from earlier studies. The Pliocene units were deposited in three adjacent subbasins, Hatay-Samandağ(HS), Altınözü-Babatorun (AB), and İskenderun-Arsuz (İA); the first two are also known as the Hatay Graben. Basin configurationsand shape, environmental evolution, and faunal compositions were affected by differential tectonic histories since the Late Miocene.In total 162 species (94 gastropod, 61 bivalve, and 7 scaphopod) are recorded, 80 of which are recorded for the first time from theregion. The occurrence of tropical stenohaline benthic taxa (such as Persististrombus coronatus and some conid gastropod species)and a number of chronostratigraphically well-constrained mollusc species shows a Zanclean age. The base of the Early Pliocene is alsoshown by the occurrence of planktic foraminifer assemblages corresponding to MPL1 and MPL2 biozones and the nannoplanktonAmaurolithus delicatus assemblage. The Early Pliocene Hatay molluscan assemblages allow for palaeobiogeographic comparisons acrossthe Mediterranean. The Pliocene marine fossiliferous deposits are assigned to the Mediterranean Pliocene Molluscan Unit 1 (MPMU1)of the western Mediterranean and Atlantic regions. However, the eastern Mediterranean assemblages are notably poorer in species andin particular a number of thermophilic groups are lacking. This marine biodiversity gradient has been a characteristic feature of theMediterranean ever since the Pliocene.