Caracterization and datation of holocene mud layers from the subsoil of the urban area of Aveiro (Portugal)

Abstract

The present paper intends to be a contribution for a better understanding of some relevant geologic and geotechnic features of the urban area of the town of Aveiro. An attempt was made in order to correlate the geotechnical properties with the mineralogical and textural parameters of the terrains that in the urban area of Aveiro consist mainly of weakly consolidated sands, clays and muds of Holocene age. The analysed geotechnical parameters point out that the Holocene muds are less expansive and plastic than the Cretaceous clays and marls. The later are richer in clay particles whereas muds are richer in silt particles. The mineral assemblages express lagoonal environments, under depositional conditions characterized by an irregular detritical supply, in a confined, with low salinity, littoral area. The first geochronological results obtained from the analysis carried out by the «Instituto Tecnológico Nuclear» (Lisboa), utilising the radiocarbon method applied to bivalve shells found out in interbeded mud layers, provided ages placed in the range 1960 ± 90 and 6450 ± 140 years BP.