Middle to Upper Pleistocene morphostructural evolution of the NW-coast of Sicily: thermoluminescence dating and palaeontological-stratigraphical evaluations of littoral deposits

Abstract

Abstract Infralittoral and terrigenous Middle to Upper Pleistocene deposits outcropping at the NW-coast of Sicily (Gulf of Castellammare and peninsula of Capo San Vito) were investigated in order to recognise glacio-eustatically caused sea level highstands and the interference between tectonics, eustasy and local conditions of the coast. The results, originating from a stratigraphically important area, were obtained by palaeontological-stratigraphical analyses, physical age determination with the thermoluminescence method and by detailed morphostructural studies. The marine deposits, situated at 3–40 m a.s.l., mainly provide an oligotypic molluscan fauna referable to modern SGCF-, SFHN- and SFBC-biocoenoses of the infralittoral zone which live on various substrates in water of moderate to strong energy. The Senegalese molluscan forms providing the palaeocommunity of Tyrrhenian age (oxygen isotope substage 5e) is comparable with the modern AP biocoenose which live on hard substrates in water of moderate energy. The age determinations and estimates of the terraces indicate at most four glacio-eustatic sea level highstands: one, perhaps two highstands between 800 ka and 250 ka (isotope stages 24-8), a further event between 250 ka and 190 ka (stage 7) and the youngest highstand event between 140 ka and 75 ka (stage 5). The last glaciation (stage 4-2) is represented by a terrigenous sequence which suggests rapid alternation of morphodynamically stable and unstable intervals, as well as changes in moisture and seasonality of climate. The terraces are affected by NE-SW orientated faults causing brittle deformation and uplifting in rates of approximately 0.14–0.25 m/ka with increasing intensity towards the East. The oxygen-isotope stratigraphy indicates 7 warming events during the past 800 ka. The morphostructural pattern of the NW-coast of Sicily gives evidence for the sensible interference between local coastal conditions like sediment drift, sea water currents and sediment supply on the one hand, the absolute rise of eustatic sea level and the absolute uplift rate on the other hand. It is obvious that eustatic oscillations, deduced from deep sea sediment values, does not automatically coincide with those recorded in the inner shelf area.