Large-scale boudinage of late Miocene platform series triggered by margin collapse during the messinian salinity crisis (Ibiza island, Spain)

• Published in: Marine and petroleum geology 2019-11, Vol.109, p.852-867
• Main Authors: Odonne, F., Maillard, A., Lézin, C., Chanier, F., Gaullier, V., Guillaume, D.
• Format: Article
• Language: English
• Subjects: Boudinage; Ibiza; Late Miocene; Messinian salinity crisis; Sciences of the Universe; Soft-sediment deformation
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2019.06.058

In Ibiza Island, we show for the first time that the post-tectonic late Miocene deposits are locally deformed in synsedimentary large scale boudinage structures. The late Miocene series is composed of a carbonate rich Unit 1 that is overlaid by a clastic Unit 2 and a Unit 3 in which a basal oolite-rich deposit is distinguished from an upper stromatolite-rich part. The oolite-rich and competent layers of Unit 3 are dissected into large rectangular to barrel-shape boudins that indicate a multidirectional extension. The separation of the blocks develops significantly northward revealing a stretching increase in a seaward direction that could have been favored by sliding of the distal part of the underlying marly unit over the clays. Along and in between the boudins, the laminated layers form soft-sediment syncline folds. The progressive bending of these laminated layers created spaces that were filled with calcite crystal wedges, providing evidence for large fluid circulation during deformation. Microthermometry on fluid inclusions in these calcite crystals revealed growth-temperatures ranging from 190 to 260 °C. This high recrystallization rate is an indication of important fluid circulation during deformation processes. Besides, the progressive infill of paleosols over some of the synsedimentary synclines indicates that deformation was a slow process during the emersion of the series. And the subaerial Messinian channels location in the topographic depressions formed by the boudinage of the late Miocene series confirms that the deformation and sliding occurred during the relative emersion associated with the Messinian Salinity Crisis. We thus interpret the boudinage as resulting from the destabilization of a still soft carbonate platform whose sliding has been helped substantially by the injection of relatively hot fluids. This work provides an onland evidence for extensional collapse during the Messinian sea-level drawdown. •We show synsedimentary large scale boudinage in the Late Miocene of NE Ibiza Island.•The badly organized chocolate tablet structure reveals a multidirectional extension.•The soft sediment deformation developed during slow translational sliding of boudins.•This sliding is due to margin collapse during the Messinian sea-level drawdown.