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Paleoceanographic information from submarine overflows in the vicinity of oceanic gateways is of major importance for resolving the role of ocean circulation in modulating Earth’s climate. Earth system models are currently the favored way to study the impact of gateways on global-scale processes, but studies on overflow-related deposits are more suitable to understand the detailed changes. Such deposits, however, had not yet been documented in outcrop. Here, we present a unique late Miocene contourite channel system from the Rifian Corridor (Morocco) related to the initiation of Mediterranean Outflow Water (MOW). Two channel branches were identified consisting of three vertically stacked channelized sandstone units encased in muddy deposits. Both branches have different channel-fill characteristics. Our findings provide strong evidence for intermittent behavior of overflow controlled by tectonic processes and regional climatic change. These fluctuations in paleo-MOW intermittently influenced global ocean circulation.

Sandstone tidal cross-strata are the predominant sedimentary feature of strait-fill stratigraphic successions. However, although widely described in numerous studies, tidal strait-fill two-dimensional and three-dimensional cross-strata have\ud rarely been reported to occur in discrete intervals which are laterally adjacent or vertically stacked, and the meaning of this stratigraphic architecture has not yet been fully investigated. Understanding of the processes responsible for changes\ud in the internal features of modern and ancient tidal bedforms is essential in order to predict lateral and vertical heterogeneities in analogous reservoir strata.\ud This facies-based study aims to interpret the three-dimensional to two-dimensional cross-strata transition observed in the lower Pleistocene mixed siliciclastic/bioclastic sandstone filling the Catanzaro Strait, in southern Italy, during a continuous phase of tectonically driven marine transgression. Tidal cross-strata\ud disappear in the uppermost interval of the studied succession, where mudstone strata prevail. This stratigraphic trend is interpreted as the evidence of an important change in the tidal strait hydrodynamics due to a phase of relative sea-level rise. At the beginning of the transgression, three-dimensional tidal dunes migrated throughout the ca 3 to 4 km wide and ca 30 km long, WNW–ESE-oriented Catanzaro Strait, due to strong tidal currents amplified through the seaway and flowing in semi-diurnal phase opposition. As the intermediate phase of transgression enlarged the seaway width, the tidal current strength decreased as tidal water exchange occurred over a larger cross-sectional area.\ud The progressive reduction of the bed shear stress modified three-dimensional tidal dunes into an extensive two-dimensional bedform field. At the end of the transgression, the further widening of the Catanzaro Strait into a ca 10 to 12 km\ud wide marine passageway changed the tidally dominated strait into a non-tidal open shelf. The results of this research suggest the presence of a ‘critical cross-sectional area’ in the narrowest strait-centre zone which controls the activation and deactivation of tidal current amplification along a marine seaway

Mixed siliciclastic-carbonate deposits consist of a suite of different types of mixing between the two components, from bed (core-plug) to stratigraphic (seismic) scales, producing a high vertical and lateral lithological variability. Mixed deposits result from the interaction of siliciclastic input and coeval carbonate production controlled by temporal and/or spatial factors. Although mixed deposits are very diffuse in the geological record, studies about these deposits are scrappy and not well encoded. Accordingly, mixed deposits represent a labyrinth for researchers who want to investigate them for the first time.In this paper, different types of mixing (compositional versus strata) controlled by different allocyclic (e.g. sea-level, climate) and/or autocyclic (e.g. depositional processes) factors that operate at different scale are documented. Mixing is recognized and described at three main scales of observation: bed/core-plug scale; lithofacies/well-log scale; and stratigraphic/seismic scale. (i) Compositional mixing reflects the contemporaneous accumulation of the two heterolithic fraction in space and time. This type of mixing is observable at lamina to bed scale, locally producing depositional structures diagnostic for particular depositional environments. (ii) Strata mixing results from the alternation of the two heterolithic fraction in time. This type of mixing is observable at lithofacies to stratigraphic scale and can be related to depositional processes, climatic variations and/or relative sea-level changes.A correct identification of these different types of mixing and the scale of their occurrence is crucial in revealing (i) physical processes that control the sedimentation, (ii) environmental factors that influence the carbonate factory related to the siliciclastic dispersal mechanisms, and (iii) internal heterogeneity of the resulting sedimentary deposit. Furthermore, the petroleum industry is interested to unravel new insights about internal properties of mixed siliciclastic-carbonate systems (e.g., porosity, permeability) and to reconstruct predictive 3D models for the related reservoirs. The correct prediction of internal heterogeneity and the recognition of lateral and vertical compartmentalization have an important impact on hydrocarbon exploration and exploitation.