The Last Glacial Maximum Balearic Abyssal Plain megabed revisited

Abstract

Megabeds are thick sedimentary layers extending over thousands square kilometres in deep sea basins and are thought to result from large slope failures triggered by major external events. Such deposits have been found in at least three areas of the Mediterranean Sea. Although their discovery dates back to the early 1980s, many questions remain, concerning their initiation, source area, extent, and the nature of their emplacement. One of the largest previously documented megabeds was emplaced during the Last Glacial Maximum across the Balearic Abyssal Plain with a thickness of 8-10 m in water depths of up to 2800 m. New 3.5 kHz sub-bottom profiles and sediment cores provide greater constraint on the lateral variability of the megabed and allow to map it beyond previous estimates, with a revised areal extent up to 90,000-100,000 km 2. Megabed terminations show gradual pinch-out to the West and an abrupt eastward termination against the Sardinia steep margin. The megabed presents both in seismic profiles and in sediment cores a tripartite subdivision likely corresponding to changes in flow regimes across the basin with a central area of sandy facies and erosional base oriented NNE-SSW allowing renewed discussions about sources and trigger of the megabed.

Salt morphologies and crustal segmentation relationship: New insights from the Western Mediterranean Sea

“…As mentioned above (Fig. 2a), the listric faults activated after the deposition of the Upper Unit and were mainly active in the Pliocene but they can reach the seafloor (Badhani et al, 2020).…”

“…(ii) the Hannibal High could have undergone a magmatic reworking during the second phase of basin opening (Aidi et al, 2018); (iii) in the WAB the presence of some mantle serpentinization is possible (Aidi et al, 2018). New heat flow data suggests different formation ages (Poort et al, 2020), confirming the contrasting geodynamic sub-basin history.…”

“…In the Gulf of Lion, the Quaternary Rhône Fan represents a large turbidite system which consists of a 1500 m-thick accumulation of turbidites and mass-transport deposits (e.g. Leroux et al, 2017;Droz et al, 2020;Cattaneo et al, 2020;Badhani et al, 2020). The marked salt deformation in the deep Gulf of Lion basin occurred in the Quaternary and is often related to this sedimentary fan, which would have pushed and squeezed the salt towards the distal basin, forming salt stocks and walls (Large Diapirs domain, Fig.…”

“…This equally means higher temperatures at the top of basement crust that will be transferred to the salt deposits. Moreover, regional hydrothermal circulations are known to occur in margins and can redistribute heat in specific margin segments (Lucazeau et al, 2010;Poort et al, 2020).…”