Shallow or Deep? A reinterpretation of the Rifian Corridor's unique sandy contourites.

his study proposes that sandstone layers exposed in the Fez-Meknes region of Northern Morocco (Ben Allou (Sidi Chaded) and El Adergha localities), have been misinterpreted as unique examples of geostrophically-driven, deep marine (150-400 m water depth) sandy contourites. Instead, our independent paleontological, sedimentological, and stratigraphic analyses showthat these sandstones representmore common,shallow marine(0-30 m water depth) tide-dominated deltas.Our findings imply that at leastsevenexisting studies have based their interpretations on erroneous paleo water depth reconstructions. Thesehave beenderived from foraminiferal assemblages from siltstone and claystone layers that interbed the sandstones. Our foraminiferal data were obtaineddirectly from all facies. These more complete datashowthat,while the siltstone and claystone layers can be considereddeep marine, the sandstones are shallow marine, and previous studies did notaccount for major sea level fluctuations that occurred here during the late Miocene. Ourreinterpretation has a defining impact on a wide scope of topics that have been covered by the existingbody of work, which involves: the origin of global paleoclimate changes, sandy contourite facies models, conditions of bottomcurrent controlled ecosystems and habitats, ichnofacies interpretations, changes in paleogeography, tectonics and reorganizations of global ocean currents and Mediterranean Outflow Water, and finally, geographic changes leading uptothe disappearance of the Rifian Corridor and the associated Messinian salinity crisis. Using biostratigraphy and measurements of stratal thickness,we also establishthat the successions here were responding to ± 70-80 m amplitude, 100 kyr period glacioeustatic fluctuations. These values represent hitherto unprecedented constraints on the natureof late Miocene climate fluctuationsthat were similar in period and intensity as Pleistocene glacial/interglacial cycles.Finally, we showthat abundant authigenic sediment generation atthe shallow marine fringes of the Rifian Corridor exacerbated its closure. Thislikelyhassignificant, previously unrecognized implications to the onset of Mediterranean isolation and the associated Messinian salinity crisis.