Coseismic vs. climatic factors in the record of relative sea level changes: an example from the Last Interglacials in SE Spain

Abstract

Trying to decipher how paleoseismic activity has influenced the altitudinal disposition of interglacial deposits is one of the main challenges to be confronted before quantifying relative sea-level changes between consecutive highstands. At the same time, identifying paleoseismic features in an area with low instrumental seismic activity can complement the seismic record, thereby contributing to better seismic hazard knowledge. In this regard, Cope Basin (SE Spain) meets all the requirements necessary for these kinds of analysis, firstly on account of its excellent outcrop conditions and secondly, because its sea level record is undoubtedly conditioned by both factors: climatically driven changes and local and regional seismotectonics.The morpho-sedimentary sequence presented in this paper provides evidence from three different highstands: two littoral sedimentary units separated by terrestrial deposits and affected by liquefaction (paleoseismic activity), and a younger paleo-cliff and its associated wave-cut platform carved into those sedimentary units. This wave-cut platform now tilted and folded, reaches heights ranging from 0 to +8 m, which has been interpreted as a consequence of cosesimic effect. The age of this wave-cut platform (Last Interglacial or Holocene) supports uplift rate estimations of from 0.016 to 0.15 mm/yr since the Last Interglacial/Holocene. Active deformation observed on Pleistocene–Holocene sea-level geomarkers can not only furnish useful information about seismic activity within the major structure of the Aguilas Arc, but also offer new insight into the Cope Basin's geodynamic model.