Single events and century-scale evolution of the northern margin of the Tagus River before the Boavista landfill: a multidisciplinary approach to a natural and anthropic sediment record
In this work we present preliminary results of the study of one sediment core (EDP1), collected near Cais do Sodré, Lisbon downtown, close to the present day Tagus riverfront. The results allowed differentiation of 4 major sediment units that present a signature of increasing anthropic influence over time. The lowermost unit (Unit 1) corresponds to a subtidal flat accreting in low energy and brackish conditions. This sedimentation pattern is interrupted by high-energy deposition of Unit 2, characterized by higher density and diversity of the foraminiferal content and high content of other bioclasts remains (Sub-unit 2A) and by the incorporation of several anthropic elements, such as 17th-18th century ceramics (Sub-unit 2B). Given the radiocarbon chronological framework and type and dates of the anthropic materials included in both sub-units of Unit 2, they are tentatively related with either the 1724 extreme storm and/or the 1755 tsunami. The abrupt drop in coccolith densities in this unit is compatible with an increase in sedimentation rate. Later sedimentation (Units 3 and 4) mirrors increasing energy in comparison with Unit 1, reflecting the shallowing of the study area and shift towards upper subtidal conditions, the natural sedimentation having been interrupted in the middle 19th century by the placement of an artificial infill that reclaimed the estuarine margin.The interpretation presented here was developed in the framework of the Lisbon Stories project, which addresses the relationships between the Tagus, the city of Lisbon and its people throughout the last few centuries.
Copyright (c) 2016 Estudos do Quaternário / Quaternary Studies
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