ESCADARIAS DE TERRAÇOS MARINHOS EM PORTUGAL CENTROOCIDENTAL – RELEVÂNCIA COMO INDICADORES DE SOERGUIMENTO CRUSTAL STAIRCASES OF WAVE-CUT PLATFORMS IN WESTERN CENTRAL PORTUGAL – RELEVANCE AS INDICATORS OF CRUSTAL UPLIFT

Abstract

This study addresses the coastal terrace staircases of western central Portugal (Cape Mondego to Cape Espichel). Below the culminant marine unit that records the last episode of aggradation before the ongoing stage of incision, several terrace levels ar identified. The following methodology was used: a) production of geomorphological maps, combining analysis of detailed MDT’s and aerial photos, with field surveys calibrated with GPS; b) stratigraphic and sedimentological study of the sedimentary deposits associated with the marine platforms; c) luminescence dating. On each terrace staircase, the number of platforms and their elevations are different, indicating differential uplift. Quartz OSL provided age estimates up ca. 150 kyr and post-IR IRSL on K-feldspar up to ca. 700 kyr for the marine terraces under study. Using the culminant platform as reference and assuming that it is ca. 3.6 Ma old, uplift rates were estimated as ranging spatially from 0.071 m/ky to 0.019 m/ky. The ongoing luminescence dating will provide uplift rates estimated for the lower and middle marineterraces, clarifying if an acceleration of the crustal uplift is going on.