What can a sessile mollusk tell about neotectonics?

Abstract

Dendropoma petraeum are fixed vermitids (mollusk) that colonize and construct abrasion platform rims along rocky shorelines. These endemic mollusks are considered good relative sea level indicators in the eastern and the southern Mediterranean, due to their narrow habitat below the sea surface (about ±10 cm). The observed relative sea level values recorded (submerged, uplifted or at present mean sea level) reflect a superposition of eustatic, isostatic, tectonic and possibly local sedimentary instabilities. The present study examines fossil Dendropoma samples gathered along the Levant coast, from northern Israel to eastern Turkey. Conventional radiocarbon dates (from Turkey, Syria and partly in Lebanon) and 14C Accelerator Mass Spectrometer (AMS) from Lebanon and Israel yields Dendropoma ages ranging through Late Holocene. A numerical model is used for calculating the change in sea level through the Holocene as a function of glacio-hydrology and isostasy of the eastern Mediterranean. Space–time dependent subtractions of the model values are used to eliminate the eustatic component of the relative sea level, in order to obtain the tectonic component. Results show a general northward increase in tectonic uplift of the Levantine coast with different rates in different tectonic segments. This differential uplift corresponds well to the major tectonic segments comprising the Levantine continental margin since the Pleistocene, from the Carmel fault to the East Anatolian fault. Hence, these segments were still active during the last thousands years and even during the last hundreds years. The general trend of northward increase in vertical displacement is predominantly dictated by the convergence between the Sinai and Arabian plates with Anatolia and Eurasia, across the Cyprus arc and Zagros belt; and the secondarily dictated by the northward increase in convergence component across the sinistral Dead Sea Fault plate boundary.