Sandy contourite drift in the late Miocene Rifian Corridor (Morocco): Reconstruction of depositional environments in a foreland-basin seaway

Abstract

The Rifian Corridor was a seaway between the Atlantic Ocean and the Mediterranean Sea during the late Miocene. The seaway progressively closed, leading to the Messinian Salinity Crisis in the Mediterranean Sea. Despite the key palaeogeographic importance of the Rifian Corridor, patterns of sediment transport within the seaway have not been thoroughly studied. In this study, we investigated the upper Miocene sedimentation and bottom current pathways in the South Rifian Corridor. The planktic and benthic foraminifera of the upper Tortonian and lower Messinian successions allow us to constrain the age and palaeo-environment of deposition. Encased in silty marls deposited at 150-300 m depth, there are (i) 5 to 50 m thick, mainly clastic 2 sandstone bodies with unidirectional cross-bedding; and (ii) 50 cm thick, mainly clastic, tabular sandstone beds with bioturbation, mottled silt, lack of clear base or top, and bi-gradational sequences. Furthermore, seismic facies representing elongated mounded drifts and associated moat are present at the western mouth of the seaway. We interpret these facies as contourites: the products of a westward sedimentary drift in the South Rifian Corridor. The contourites are found only on the northern margin of the seaway, thus suggesting a geostrophic current flowing westward along slope and then northward. This geostrophic current may have been modulated by tides. By comparing these fossil examples with the modern Gulf of Cadiz, we interpret these current-dominated deposits as evidence of late Miocene Mediterranean overflow into the Atlantic Ocean, through the Rifian Corridor. This overflow may have affected late Miocene ocean circulation and climate, and the overflow deposits may represent one of the first examples of mainly clastic contourites exposed on land.

The Gibraltar Corridor: Watergate of the Messinian Salinity Crisis

“…We conclude that all gateways through southern Spain and northern Morocco reflect an uplift trend starting as early as the late Tortonian and show no evidence for a marine MSC connection to the Atlantic (Capella et al, 2017b(Capella et al, , 2018Tulbure et al, 2017;Van der Schee et al, 2018). We thus corroborate the alternative hypothesis of a Messinian connection through the Gibraltar region and present a computational reconstruction on how the dimensions of this "Gibraltar Corridor" may have evolved throughout the Messinian.…”

“…Palaeogeographic reconstructions of depositional environments in the late Miocene sedimentary basins of Northern Morocco, based on surface-subsurface correlations, helped to elucidate the temporal and spatial evolution of the Rifian Corridor (Capella et al, 2017a;. The restriction of the southern branch had already started in the late Tortonian-early Messinian (Krijgsman et al, 1999b;Ivanovic et al, 2013) and was driven by a phase of enhanced uplift along high angle faults (Capella et al, 2017b(Capella et al, , 2018. Improved biostratigraphic dating of the continuous transition from marine to continental-lacustrine deposition shows that the South Rifian Corridor closed at 7.1-6.9 Ma (Capella et al, 2017a;.…”

“…During the early Messinian, all the Betic connections and the North Rifian Corridor were closed by Africa-Iberia convergence processes (e.g., Spakman et al, 2018). The South Rifian Corridor was still open during the earliest Messinian, but a marked transition to continental and lacustrine deposits dates its closure at <6.9 Ma (Capella et al, 2017b). A gap of one million year separates the last field evidence of marine connection and the onset of the MSC in the Mediterranean.…”

New age constraints on the western Betic intramontane basins: A late Tortonian closure of the Guadalhorce Corridor?

“…Our results imply that the Mediterranean Outflow (MO) through the Guadalhorce Corrdior (Martín et al., ) occurred in the late Tortonian. Coeval MO is recorded in the Rifian Corridor (Capella, Hernández‐Molina, et al., ). Models show that the relative gateway depths of the two straits determine whether they both have two‐way exchange, or in‐ and outflow only (De la Vara, Topper, Meijer, & Kouwenhoven, ).…”

Deep‐water dunes on drowned isolated carbonate terraces (Mozambique Channel, south‐west Indian Ocean)

“…Most of the observed deep‐water sand dunes published in the literature correspond to barchan or barchanoid dunes. Good examples have been reported from the Carnegie Ridge in the eastern equatorial Pacific (Lonsdale & Malfait, ), the Faroe‐Shetland Channel (Wynn et al ., ), the Gulf of Cadiz (Hanquiez et al ., ) and the Gulf of Mexico (Kenyon et al ., ), and from the ancient record of continental slopes in Brazil (Mutti et al ., ), Uruguay (Hernández‐Molina et al ., ), eastern Canada (Campbell & Mosher, ) and Morocco (Capella et al ., ). Fields of transverse dunes have also been identified on both the Carnegie Ridge (Lonsdale & Malfait, ) and the Maldives carbonate platform (Betzler et al ., ; Lüdmann et al ., ), as well as on continental slopes associated with geostrophic currents, for example in the Barents Sea (King et al ., ; Bøe et al ., ), on the south‐eastern Brazilian margin (Viana, ) and in the Gulf of Cadiz (Hanquiez et al ., ; Hernández‐Molina et al ., ).…”