Facies y evolución holocena reciente en el canal mareal de Mira (Portugal)

Zusammenfassung

The Mira tidal channel, trending SSW-NNE, is situated in the Aveiro backbarrier area. It corresponds to the last evolution phase of the Aveiro and Mira estuaries, developed during the Plio-Quaternary period. The stratigraphy of the infilling deposits of the Mira channel has been studied in 47 cores, grouped throughout 15 transects. The boreholes correlation indicates the presence of two stages in this area which have been related to the last 500 years, according to the historical references. Tn this time the development of the barrier was the more important process together with a subsequent southward displacement of the estuary mouth. The barrier was completely developed during the Recent stage. The barrier shows an inlet located in Vagueira with an assymetric distribution of the ebb and flood currents and a well developed flood tidal delta. This situation is reflected by subtidal channel sands and intertidal mudstones, deposited north and southward of the inlet, while in the inlet proximity the deposits consist of tidal sand bars. During the Present stage, the Vagueira inlet is closed and a new northernmost inlet (S. Jacinto) is open, which results in the inversion of the current system and the present running of the Mira channel. The flood tidal delta and the subtidal chanel sands predominate in the head zone; the channel sands and intertidal linear bars are widespread in the intermediate zone and in the mouth zone the whole cycle appears, including the intertidal mudstones. The Present stage is thicker toward the north, indicating the depositional slope of the Mira channel.