Aragonite Fraction Dating of Vermetids in the Context of Paleo Sea-Level Curves Reconstruction
| Autor: | Renato B. Guimarães, Katerina Douka, Perla Baptista de Jesus, Kita Macario, Fábio Ferreira Dias, Vinicius N. Moreira, Julia Caon Araujo |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Calcite
010506 paleontology Archeology Recrystallization (geology) Aragonite 010401 analytical chemistry Mineralogy Context (language use) engineering.material 01 natural sciences 0104 chemical sciences law.invention chemistry.chemical_compound chemistry law engineering General Earth and Planetary Sciences Carbonate Sodium polytungstate Radiocarbon dating Geology 0105 earth and related environmental sciences Accelerator mass spectrometry |
| Zdroj: | Radiocarbon. 62:335-348 |
| ISSN: | 1945-5755 0033-8222 |
| Popis: | Identifying and tackling recrystallization is a critical factor in the reliable radiocarbon (14C) dating of carbonates, since exogenous carbon can be incorporated and thus mask the real age of the samples. Vermetids are among the most important bioindicators used for paleo sea-level reconstruction, and the accuracy of their chronology can significantly impact sea-level curves. Age differences larger than 1 14C kyr before and after acid etching, combined with X-ray diffraction (XRD) analysis that indicates a significant amount of calcite still remains in the shell, led us to apply the previously developed carbonate density separation protocol (CarDS). Using a solution of sodium polytungstate, with density of 2.80 g/cm3, we successfully separated different carbonate fractions for a set of 10 vermetid samples from the coast of Rio de Janeiro, southeast of Brazil. Each separation was verified by XRD analysis and the 14C concentrations of different fractions were compared. The results show that the calcite fraction in the studied vermetid samples varied from 12 to 63% and aragonite fraction ages are up to 2 14C kyr older than the raw samples, thus confirming the efficacy of CarDS in removing young carbonates and the importance of density separation to vermetids prior to accelerator mass spectrometry (AMS) dating. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|