Pb mass accumulation rates in the depositional area of the Magra River (Mediterranean Sea, Italy)

I. Delbono, M. Barsanti, A. Schirone, F. Conte, R. Delfanti

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Abstract

Nine sediment cores were collected between 2009 and 2012 in the inner continental shelf (Mediterranean Sea, Italy) mainly influenced by the Magra River, at water depths ranging from 11 to 64 m. Mass Accumulation Rates (MARs) were calculated through210Pb analysed by Gamma spectrometry. Three different dating models (single and two-layer CF-CS, CRS) were applied to clay normalised210Pbxsprofiles and137Cs was used to validate the210Pb geochronology. The maximum MAR values (>2 g cm-2yr-1) were found in the region adjacent to the Magra River mouth and outside the Gulf of La Spezia (0.9±0.1 g cm-2yr-1at St. 3-C6 and 4-C4). Results from137Cs/210Pbxsratios calculated in Surface Mixed Layers (SMLs) evidenced the coastal boundaries of the Magra River depositional area, which is very limited towards south. Differently, in the north-west sector, fine sediments are generally driven by the Ligurian Current and move towards north-west: at the deepest and most distant station from the River mouth, the MAR value is the lowest one in the study area.Few major Magra River floods occurred during the sediment core sampling period. By using the short-lived radioisotope7Be as a tracer of river floods, a clear7Be signature of 2009 flood is present at St. 1-SA1C. Finally, by analyzing the clay normalised210Pbxsprofiles, a decrease of its activity dating the years 1999 and 2000 is observed in four cores, corresponding to two major Magra River floods occurring in those years.
Original languageEnglish
Pages (from-to)35 - 48
Number of pages14
JournalContinental Shelf Research
Volume124
DOIs
Publication statusPublished - 1 Aug 2016
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Oceanography
  • Aquatic Science
  • Geology

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