La série saumâtre et continentale d'âge Miocène moyen et supérieur d'Eivissa (ex-Ibiza, Baléares)

Abstract

At first, it is recalled that the main tectonics of Eivissa (Ibiza) involves white marls of upper Burdigalian- lower Langhian, with abundant planktonic microorganisms. But, near the south-west promontory of the island, in a site discovered a century ago by Vidai and Molina (1888), one find directly transgressive on the Senonian, polygenic conglomerates, then a sandy marly formation with Bivalvia (Cmssos- crea gryphoides, Mytilus aquitanicus, ...) and few benthic Foraminifera, finally coaly clays with brackish or estuary Gastropods. This "Formation of Cap Jueu" has also provided Langhian-like scarce paiynological assemblages. Strata of the same sedimentary cycle, also involved in the tangential tectonics, may be pointed out at the top of the imbrication of Roques Altes (ex- Rocas Altas), South West of la Talaia of Sant Josep (ex- San José) and near ant Rafael, maybe dating from the Tortonian (?) by microflora. It is possible to group here the "top conglomerates" from the center of the island, which lie up to Tnas, but usually ravining lower Langhian marls. So, an independent sedimentary cycle, prior to paroxysmal tectonics, dated as "middle" - ? upper Miocene (Langhian to ? Tortonian), may be defined, which goes before the deposit of marine "upper" Tortonian (Limestones of Portinatx), posterior to the main compressive phase. Clayey interstratifications in these limestones have provided poor paiynological assemblages corresponding to this Tortonian age. In short, the Miocene from Eivissa shows three independent sedimentary cycles which enable to date tectonic episodes concerning this eastern extension of Betic Cordilleras.