Impact of pulsed Atlantic water inflow into the Alboran Basin at the time of the Zanclean flooding

Abstract

International audienceThe study of more than 500 single- and multi- channel seismic records enabled the generation of a detailed palaeo-bathymetric map of the Messinian surface over most of the Alboran Basin, Western Mediterranean. This regional surface is characterized by several erosional features (channels, terraces and canyons) and topographic highs (structural, volcanic and diapiric in origin). The most prominent feature is the incised Zanclean Channel crossing the entire basin, its entrenchment having been associated with the opening of the Strait of Gibraltar and subsequent inflow of Atlantic waters. The incision depth of the channel is variable, suggesting local variations in the erosive capacity of the Atlantic inflow, conditioned mainly by the regional basin topography and the local presence of topographic highs. Adjacent to this channel along the Spanish and Moroccan margins, and near the Strait of Gibraltar, several submarine terraces developed at different depths suggest a pulsed flooding of the Alboran Basin. There could have been two major inflow phases of Atlantic water, one shortly before and another during the Zanclean flooding, the latter accompanied by periods of relative sea-level stillstands that enabled terrace development. Alternatively, these features were all generated during the main flooding evident and subsequent pulsed infilling of the basin

Tectonic control of the oil-rich large igneous-carbonate-salt province of the South Atlantic rift

“…In the south, over the São Paulo Plateau, the entering sea eroded wide stretches of reworked carbonates, while avalanches of carbonates and Mg-rich shales were sliding down near faults from temporary islands into the deeper portions of the former lakes (de Paula, oral comm.). Similar phenomena were observed east of Gibraltar in the Mediterranean as the major drop of sea level in the Messinian was followed by re-entrance of the sea (Estrada et al, 2011;Rabineau et al, 2015). Both the thickness and width of the salt body increase southward, reaching, respectively, 1-2 km and about 700 km in the Santos Basin (Fig.…”

“…A C C E P T E D (Estrada et al, 2011;Bache et al, 2012;Rabineau et al, 2015). These canyons may have connected to either rivers outside the basin or the proto-Equatorial Atlantic, but the uplift of NE-Brazil in the Tertiary does not allow following the connections.…”

Structure of mud volcano systems and pockmarks in the region of the Ceuta Contourite Depositional System (Western Alborán Sea)

“…In the western Moroccan margin, Tesson et al (1987) firstly defined two sedimentary sequences, B (Pliocene) and A (Quaternary), bounded by a regional unconformity above the acoustic basement. Later, higher resolution regional studies Campillo et al, 1992;Ercilla et al, 1994;Hernández-Molina et al, 2002) indicated that Pliocene-Quaternary sequences are bounded by a strong, laterally continuous reflector that corresponds to the reflector M (i.e., the Messinian erosion surface, recently mapped throughout the Alborán Sea by Estrada et al, 2011). Three main key reflectors divide the Pliocene-Quaternary deposits into four seismic sequences; P1, top of the lower Pliocene; P2, top of upper Pliocene; and Q1, top of the Calabrian deposits.…”

Probing connections between deep earth and surface processes in a land-locked ocean basin transformed into a giant saline basin: The Mediterranean GOLD project#

“…Seismic stratigraphy shows a prominent flat wave-cut surface interpreted as erosional features carved during the refill, which argues for a slow initiation of the refill . However, to explain the prominent erosional trough observed in the Alboran Sea (a feature that is revealed by seismic stratigraphy as deeper than 300 m, wider than 6 km in places, and at least 200 km long; Estrada et al, 2011), the flood's 9 feedback should eventually lead to a water discharge close to 10 8 m 3 /s, vanishing the level difference across the Gibraltar threshold in no more than a few years ( (Loget et al, 2015). This will go hand-in-hand with multiscale seismic imaging of basin fill and the crustal and upper mantle structure through a combination of multichannel and wide-angle seismic profiling, and the deployment of novel seismic instrumentation (including the Mermaid system of floating seismometers (Jones, 2014) and the European Plate Observing System (EPOS)).…”