Pliocene to Recent shallow-water contourite deposits on the shelf and shelf edge off south-western Mallorca, Spain

Abstract

This paper presents evidence for the presence of shallow-water contourite drifts on the south-western shelf and shelf edge off Mallorca in water depths between 150 and 275 m. These are called the Mallorca contourite depositional system (CDS). The elongate-mounded shallow-water CDS in this area is ascribed to an offshoot of the Balearic Current, which flows north to south through the Mallorca Channel as part of the overall thermohaline circulation in the Mediterranean Sea. Drift geometry suggests that the north–south current is deflected into an east–west flow pattern by interaction with a marked seafloor bathymetry, associated with major fault displacement. Four seismic units separated by three prominent discontinuities can be identified. The three internal discontinuities are correlated to large-scale basin-wide events: the lower Pliocene revolution (4.2 Ma), the upper Pliocene revolution (2.4 Ma) and the mid-Pleistocene revolution (0.9 Ma). The Plio-Quaternary succession has been deposited on top of a Miocene reef, which serves as an acoustic basement and is affected by a large fault, offsetting the basement on average by 150 m. Marked erosional features throughout and further incision of the Sant Jordi Channel along the basement fault in the Pleistocene deposits indicate stronger currents in this period. The Pleistocene deposits also show a pronounced cyclicity, which is tentatively ascribed to climatic variations and the effects of eustatic sea-level fluctuation over the south-western Mallorca shelf at that time.