The Gibraltar Corridor: Watergate of the Messinian Salinity Crisis

Abstract

We search for the Mediterranean-Atlantic gateway that delivered the marine salt during the Messinian Salinity Crisis  All previously proposed late Miocene gateways through southern Spain and northern Morocco are shown to have closed during the latest Tortonian-earliest Messinian  The Gibraltar Corridor is considered to sole candidate gateway and was most likely open during most of the Messinian Salinity Crisis  The dimensions of the Gibraltar Corridor during the MSC are estimated based on Mediterranean salinity fluctuations using geophysical models  A revised palaeogeographic evolution of the Gibraltar region is presented for the late Tortonian to early Zanclean.

Mantle resistance against Gibraltar slab dragging as a key cause of the Messinian Salinity Crisis

“…Recent (up to Holocene) deformational events are mostly related to E‐ to ENE‐orientated strike‐slip faults (Luján et al, ). The Camarinal Sill—which remains the most plausible late Messinian gateway (Krijgsman et al, )—is bounded by N‐S‐ to NNW‐SSE‐orientated scarps, which could be faults inherited from the Flysch imbricates that reactivated with a normal component (Luján et al, ).…”

“…(a) ArcGlobe (ESRI™) topography of the Gibraltar region with projection of the paleogeography of the Mediterranean‐Atlantic gateways after (Krijgsman et al, ). The three insets illustrate the timing and mechanisms of vertical motion that led to the temporary isolation (~5.33–7 Ma) of the Mediterranean, and refer to the corresponding geodynamic forces.…”

“…Field evidence suggests that by 7 Ma, the Betic and Rifian gateways were shut and uplifted (Capella et al, ; van der Schee et al, ). After 7 Ma, an embryonic Strait of Gibraltar took over the connectivity in an area that was either always submerged or barely emergent on top of the Flysch units (Krijgsman et al, ). Morphological evidence of ENE‐ to E‐orientated faults at the Camarinal Sill (Luján et al, ) suggests that strike–slip structures may have controlled connections at a time of little or no vertical motion.…”

“…An important phase of paleogeographic re‐organization occurred between 8–6 million years ago (Ma), when the Atlantic‐Mediterranean portal changed its configuration from a foreland‐basin system of gateways (the Betic and Rifian corridors; Figure ) to a single channel (the proto‐Strait of Gibraltar; Krijgsman et al, ). First‐order consequences of this re‐organization were marked changes in fauna, sedimentation and hydrology of the Mediterranean Sea, which witnessed first an increase in stress‐tolerant benthic foraminifera and the occurrence of sapropels interbedded with marlstone between 8–6 Ma (Flecker et al, ; Kouwenhoven, Hilgen, & Zwaan, ), and later the deposition of giant evaporite beds during the peak of the Messinian Salinity Crisis (Roveri et al, ).…”

“…Since eustatic sea‐level changes are estimated at only 10–20 m during the latest Miocene (Miller, Mountain, Wright, & Browning, ), the causes of final closure of the Betic, Rifian and proto‐Gibraltar gateways (Krijgsman et al, ), as well as the opening of the Strait of Gibraltar that ended the Messinian Salinity Crisis, are commonly sought in tectonic processes (Duggen, Hoernle, Bogaard, Rüpke, & Phipps Morgan, ; Jolivet, Augier, Robin, Suc, & Rouchy, ). Tectonic processes in the gateway region are associated with the formation of the Gibraltar orogenic system (Figure ) that occurred during both relatively slow Africa‐Iberia convergence (Jolivet et al, ; Platt et al, ) and, up to the late Miocene, relatively rapid westward retreat of the east‐dipping Gibraltar slab (Duggen et al, ; Lonergan & White, ).…”