Coastal uplift in continental collision plate boundaries: Data from the Last Interglacial marine terraces of the Gibraltar Strait area (south Spain)

Abstract

The spatial-height analyses of deposits belonging to isotopic substages 5e and 5c indicate the occurrence of differential uplift in the Gibraltar Strait area. Maximum mean uplift rates do not reach values of 0.2 mm/year displaying a gentle deceleration from 0.15 to 0.10 mm/year for the last 128 ka. Maximum estimated rates are recorded in the central sector of the Gibraltar Strait. The combined analysis of the accumulated vertical movements before and after ISS 5c indicates that differential uplift is accommodated along NE-SW sinistral and NW-SE dextral (mostly inherited) strike-slip fault systems separating coastal segments of contrasting uplifting/subsiding behaviour. The occurrence of inversions in the relative vertical offsets along some of these faults arises when this combined analysis is performed. A model of 'asymmetric' pure shear, defined by these two fault systems, generated in response to the roughly N-S convergence between the African and Eurasian plates, can explain the recorded uplift patterns. In this transpressive setting generated by the Africa-Eurasia continental collision the recent convergence (4 mm/year) is mostly released by shear processes and subsidiary E-W horizontal extension, whilst the recorded coastal uplift only represents a low percentage of the recent convergence rates.