Dissolution Behavior of Calcareous Nannoplankton and Possible Alteration of Their Assemblages

• Autores: Kyoma Takahashi-Shimase, Satoru Nakashima
• Localización: Journal of taphonomy, ISSN 1696-0815, Vol. 4, Nº. 1, 2006, págs. 17-27
• Idioma: inglés
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• Resumen

  • In order to evaluate alteration of calcareous nannoplankton assemblages during their deposition-diagenesis, a dissolution experiment of calcareous nannoplankton from a marine sediment sample was carried out. An assemblage of calcareous nannoplankton (coccoliths) found in surface sediments taken from the Caribbean Sea was put in stirred pure water with a fixed ionic strength (0.7 mol/l KCl) at 27.5°C to trace their dissolution behaviors. Temporal changes in pH and Ca concentration during the dissolution experiment indicated that the dissolution kinetics were similar to those found in the simple calcite system. By counting numbers of different species and taxonomic groups, the apparent dissolution rates were determined for each species and taxonomic group. The obtained individual dissolution rates differ among different species and taxonomic groups up to a factor of about 9. The resulted nannoplankton assemblages after dissolution were therefore very different from the original ones. This implies that the fossil assemblage can be altered during the deposition-diagenesis by carbonate dissolution processes.