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Seasonal Influence of the Front Area on Sediment Deposition in the Northwestern Adriatic Sea

  • F. Alvisi
  • M. Frignani
  • M. Ravaioli

Abstract

In order to improve our knowledge of short time-scale variations of seasonal particle fluxes into sediments, 28 short sediment cores were collected along six transects in two areas influenced by the frontal system formed by the Po River waters moving into the Adriatic Sea. Radioisotopes 234Th and 137Cs were measured in surficial sediment sections and used as tools to evaluate the rates of sediment deposition, accumulation and mixing. Sedimentological and mineralogical parameters were also analysed.

The 137Cs distribution points out that the area south of the Po Delta, characterised by muddy sediment scarcely colonised by macrofauna, is directly influenced by the input of fine material delivered by the Po River. Here the surficial 234Th activities are lower in winter than in summer. This suggests a front influence that in the warm season couples a higher concentration of suspended matter with an enhanced capacity of interaction with particle-reactive species. The lithology of the area in front of the Marche Region is otherwise characterised by an alternance of silt and clay. Together with the presence of thanatocoenoses, this pattern reflects pulsed sedimentation with colonisation stages and sudden inputs of sediment that bury the benthic fauna. High values of 334Th activities were found at the stations close to the front, where the amount of particulate material is high. Behind the front line, thorium activities are lower, due to both the shallow environment and the kind of particles. The maximum values of 234Th activities, characteristic of the two offshore stations, reflect the high depth of the water column, the enhanced residence time of particles and the very fine grain size of the sedimentary material.

Keywords

Sediment Deposition Front Area Frontal System Seasonal Influence Marche Region 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag Italia 2001

Authors and Affiliations

  • F. Alvisi
    • 1
  • M. Frignani
    • 1
  • M. Ravaioli
    • 1
  1. 1.Istituto di Geologia MarianaCNRBolognaItaly

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