Search

The Balearic Promontory (Spain) is of key importance to understand the tectonic kinematics of the westernmost Mediterranean, because its continued marine sedimentation has recorded the contrasting effects expected from competing geodynamic models proposed for the region. Near the center of this promontory, between the islands of Mallorca and Ibiza, the Miocene to Pleistocene stratigraphy of the Central Mallorca Depression presents an ideal record of the tectonic deformation that has received only limited attention. We use a widespread dataset of 2D seismic reflection profiles to identify, interpret and map the main prominent reflectors and extrapolate the thickness of the pre-Messinian and Pliocene-Quaternary sedimentary units. We then quantify the timing and style of deformation related to the various fault systems. Our results reveal for the first time a series of aligned small depressions bounded by extensional and strike-slip faults and filled with Plio-Quaternary sediment, perfectly aligned with the sub-basins of the onshore Mallorca Graben. A subsidence analysis confirms this correlation. We identify non-cylindrical deformation within the Plio-Quaternary unit that is remarkably similar to that observed onshore, suggesting continuous fault zones from the Central Mallorca Depression to Mallorca Island. We interpret an intra-PQ unconformity as the marker of a transition from extensional to strike-slip tectonic regime. The strike-slip stage is represented by both transpressional and transtensional structures, interpreted as restraining/releasing bends respectively and step overs along the faults. We show that these offshore faults in the Central Mallorca Depression overlap well with seismic epicenters and suggest major active strike-slip corridors that have an onshore continuity both until eastern Mallorca and in the southwestern Ibiza margin. The role of previous tectonic inherited structures (rifting, Betic thrusts, post-orogenic collapse) on the deformation reported here is discussed and we propose a tentative sketch that integrates our results in a Miocene to Present-day evolution at regional scale. • Post-Messinian deformation affects the Central Mallorca Depression. • Strike-slip fault systems correlate onland-offshore Mallorca and Ibiza Islands. • The systems localize extensional / compressional structures into long corridors. • Small depocenters of PQ units align onland-offshore. • Recent tectonics and important structural inheritance control local subsidence. [ABSTRACT FROM AUTHOR]

In order to better constrain the chronology of the Messinian Salinity Crisis (MSC) onland and to provide new observations on the stratigraphic position of the Messinian erosional surface as well as evidence for continentalization, we have studied the Mio-Pleistocene succession of the island of Ibiza, ideally located in a strategic position between the peripheral Messinian basins of south-eastern Spain and the MSC-related gypsum of the Palma Basin (Mallorca). Five lithological units are identified and compared with those known from the island of Mallorca. The equivalent of the "reef" unit, mainly Tortonian in age, is composed of median to inner ramp facies. It is overlain by coastal alluvial fans set up under extensive tectonic control, and then by a carbonate unit rich in oolites and microbialites attributed to the Terminal Carbonate Complex (TCC) of Messinian age. The overlying red clays fossilizing paleosols express a continentalization phase at the end of the Miocene. This regressive episode is evidenced by karstification and erosion incising the pre-crisis units and shaping valleys connected to submarine canyons. The erosion surface is linked to the acme of the MSC, a major sea-level fall, and is then sealed by Pliocene coastal calcarenites or by Pleistocene eolianites. The emptying of the basin led to a global collapse, which is recorded on all the slope domains of the Mediterranean margins. We document this collapse for the first time onland by syn-MSC gravity events such as mudflows, upwelling of geothermal fluids under pressure and soft deformation of the TCC. The interweaving of these phenomena of multiple origin (baselevel decrease, climate change, geothermal activity, sediment transfer) contributes to the onland/offshore reshaping of the Mediterranean margins during the major environmental changes of the Messinian salinity crisis. • Two main regressions and transgressions control Upper Miocene sedimentation. • Extensional tectonic influence is well expressed during Tortono-Messinian interval. • The major regression with generalized emersion is recorded after TCC deposits. • The emersion is contemporaneous with gravitational instabilities and major erosion. • Major erosion is related to the MSC Margin Erosion Surface. [ABSTRACT FROM AUTHOR]