The sedimentary and environmental history of Tortonian-Messinian lakes at the east Mediterranean margins (northern Israel)

Abstract

During the late Neogene, the east Mediterranean margins of the Levant went through major morphological changes due to tectonic activity associated with the Dead Sea Transform Fault. The regional fluvial systems inverted their flow direction from westward towards the Mediterranean to eastward towards the Jordan Valley. Tectonic basins that developed at that time in northern Israel were filled by lakes with intermittent connections to the sea. The tectonic processes were accompanied by volcanism of alkali basalts. This study focuses on the evolution of sedimentary-volcanic sequences, mainly included in the Bira and Gesher Formations that were deposited in lacustrine and palustrine environments in northern Israel. The study presents a comprehensive dataset and interpretation integrating new and old lithological and paleontological records from outcrops and drill holes, together with new petrographic and mineralogical data. The Bira Formation of Tortonian age, which overlies the Lower Basalt unit, consists mainly of lacustrine littoral limestone and dolostone and basinal marl. Sporadic occurrences of marine macrofauna indicate pulses of marine ingressions that reached the Jordan Valley depocenter, where thick sequences of gypsum and salt were deposited. The overlying Gesher Formation of Messinian-early Zanclean age, which has a similar lithology to that of the Bira Formation, represents an environmental evolution from restricted shallow lakes into a larger lake, or lakes, and finally to shallow isolated water bodies. The latter stage coincides with the Messinian Salinity Crisis, when climate became more arid in the Levant. Pyroclasts and some lava flows recorded an ongoing volcanic activity during this period that intensified toward the eruption of the Cover Basalt unit, that overlies the Gesher Formation. Overall, the Bira and Gesher formations provide a detailed sedimentological, tectonic and volcanic history of the continental margins of the east Mediterranean and its connection to the tectonic evolution of basin associated with the Dead Sea Transform Fault.