Discovery of the Messinian Eratosthenes Canyon in the deep Levant Basin

Abstract

The Messinian Salinity Crisis (MSC) was a major disruptive event in Earth's history involving all Earth's systems - hydrosphere, biosphere, lithosphere, and atmosphere. Approximately six million years ago, the entire Mediterranean Sea turned into a hypersaline basin when the Gibraltar gateway to the Atlantic Ocean narrowed and evaporation exceeded fresh water input. Consequently, marine fauna died and massive deposition of salt on the seafloor had led to the formation of the world's youngest salt giant.A fundamental observation related to this enigmatic period is a remarkable erosional surface, associated with 100 s-of-m deep canyons that were incised across the Mediterranean's continental margins during the crisis. Such canyons across the Levant margins were described in the 1970s and, later, in the 2000s they were shown to be the gateway for shallow, sinuous, submarine channels that continued towards deeper parts of the basin. Though it could have been assumed that these channels end as terminal sedimentary lobes in the Levant Basin, we show here that they contributed to a much wider sedimentary system in the Eastern Mediterranean Sea: farther west, they merge into a nearly 500-m-deep and ∼ 10-km-wide canyon, which we name after the nearby Eratosthenes Seamount. This remarkable canyon was excavated at the beginning of the MSC prior to salt deposition. We suggest that incision took place during Stage 1 of the MSC, but we cannot rule out faster incision (10s of ky) at the end of Stage 1 (∼5.60 Ma), or at its very beginning (∼5.97 Ma).Regardless of its exact age, we show that the Eratosthenes Canyon was excavated subaqueously and suggest that incision was caused by gravity currents, such as sediment-laden turbidites and/or dense brines. We argue that the increased salinity at the beginning of the crisis and a possibly limited sea level fall - whose amplitude should be investigated - had triggered these gravity currents, destabilizing the continental margin and carving the seabed wherever it was steep enough.