Messinian astrochronology of the Melilla Basin: Stepwise restriction of the Mediterranean–Atlantic connection through Morocco

The Melilla Basin (NE Morocco) formed the easternmost part of the Rifian Corridor, which was an important Mediterranean–Atlantic gateway during the Late Miocene. The sedimentary infill of the basin consists of a shallow marine, precession-related cyclic marl–diatomite succession, laterally grading into a marginal carbonate complex. Three bio-sedimentary events have been recorded within the marl succession: 1) onset of diatomite deposition, 2) major change in foraminiferal assemblages, and 3) transition to Halimeda-rich carbonates and Porites coral reef build-ups. Recent 40Ar/39Ar dating has provided a good age control for the Melilla carbonate sequences, but a high-resolution astronomical time frame is necessary to solve the climatic signature of the basin sediments.This study focuses on the shallow marine marl succession of the Melilla Basin. Integrated magneto-, cyclo- and biostratigraphy allowed a detailed correlation to the astronomical target curve, resulting in a high-resolution time frame for the Late Miocene evolution of the basin. Comparison of the Melilla data with previous results from other Moroccan and Mediterranean basins indicates that the input of Atlantic waters through the Rifian Corridor became restricted after 6.84 Ma, and was minimized by 6.58 Ma. In the final period (6.58–5.96 Ma) towards the Messinian Salinity Crisis, the Melilla Basin can be considered as a marginal basin of the Mediterranean.The astronomical time frame for the marl sequences of the Melilla Basin moreover enables a direct comparison between the independent isotopic and astrochronological dating techniques, as astronomical ages have also been assigned to intercalated volcanic tuffs for which 40Ar/39Ar ages were previously determined. We conclude that the isotopic ages are systematically younger than their astronomical equivalents.