Two Cenozoic Extensional Phases in Mallorca and Their Bearing on the Geodynamic Evolution of the Western Mediterranean

Abstract

We study the structure of the Llevant ranges in Mallorca with special emphasis on the Cenozoic extensional evolution of the island, which we integrate in a new geodynamic model for the Westernmost Mediterranean. Mallorca underwent two Cenozoic rifting phases in the Oligocene and Serravallian, before and after the development of its Foreland Thrust Belt (FTB). The first extensional event produced Oligocene semigrabens (≈29–23 Ma) that were inverted during the Early-Middle Miocene (19–14 Ma) WNW-directed FTB development. The second rifting event produced the extensional collapse of the Mallorca FTB during the Serravallian (≈14–11 Ma). This later rifting was polyphasic, with two orthogonal extensional systems, producing first NE-SW, and then NW-SE extension. The Oligocene extension affected a major part of the Western Mediterranean, opening the Liguro-Provençal and other basins after the collapse of the Palaeogene AlKaPeCa orogen, and Mallorca, its former hinterland. Continued plate convergence nucleated a new subduction system in the Early Miocene that initiated along the Ibiza transform, producing the Mallorca WNW-directed FTB and subduction of the South-East Iberian passive margin. This process individualized the Betic-Rif slab and initiated its westward retreat. Serravallian extension occurred at the northern edge of the subduction system coeval to the Algero- Balearic basin opening. Extension initiated toward the SW direction of slab tearing and later rotated to a NW-SE direction, probably in response to flexural and isostatic rebound. Through these processes the Alboran domain archipelago was driven toward the southwest until the Late Miocene, contributing to the present isolation of Mallorca from its Betic hinterland.