1. Dating young Holocene coastal sediments in tropical regions: Use of fallout 239,240Pu as alternative chronostratigraphic marker.
- Author
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Corcho-Alvarado, J.A., Diaz-Asencio, M., Froidevaux, P., Bochud, F., Alonso-Hernández, C.M., and Sanchez-Cabeza, J.A.
- Subjects
HOLOCENE Epoch ,COASTAL sediments ,ARCHAEOLOGICAL dating ,NUCLEAR weapons testing ,RADIOISOTOPES - Abstract
We present a study on the use of
239,240 Pu as a chronostratigraphic marker to constrain210 Pb ages in young Holocene sediments from four coastal locations of Cuba (Caribbean Sea). The selected sites typify a variety of deposition environments such as a bay, a gulf, a coastal lagoon and a river estuary. The vertical distributions of210 Pb (and226 Ra),239,240 Pu and137 Cs in the sediment cores were determined in order to quantify the sedimentation processes. Mean activity ratios of 0.04 ± 0.01 for238 Pu/239,240 Pu and 0.3 ± 0.2 for241 Am/239,240 Pu indicated that atmospheric nuclear weapon tests (NWT) fallout was the main source of the anthropogenic radionuclides. Marine sites (Havana Bay and Gulf of Batabano) were characterized by low or negligible signals of137 Cs, which impeded its use as a chronostratigraphic marker. In the Sagua River Estuary and the Guanaroca Lagoon, where mixing of fresh and saline waters take place, depth profiles of137 Cs and239,240 Pu were in good agreement. A simple model that assumes a well-mixed reservoir in surface ocean waters and constant sediment accumulation was used to interpret the239,240 Pu profiles. The model corroborated the210 Pb ages, except in the case of the highly mixed sediment cores from the Gulf of Batabano. The apparent mean residence time of239,240 Pu in the well-mixed reservoir ranges from 5 to 50 years, with longer timescales for marine sites.239,240 Pu showed to be a useful time tracer in coastal sediments where the137 Cs signal is very low. [ABSTRACT FROM AUTHOR]- Published
- 2014
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