Assessing the dead carbon proportion of a modern speleothem from central Brazil

Autor(es):Mostrar menos -

Macario, K. D. ^[1] ; Strikis, N. M. ^[2] ; Cruz, F. W. ^[3] ; Hammerschlag, I ^[1] ; Alve, E. Q. ^{[1, 4]} ; Novello, V. F. ^[3] ; Edwards, L. ^[5] ; Cheng, H. ^[6] ; Andrade, F. R. D. ^[3] ; Buarque, P. F. S. M. ^[3] ; Garbelim, J. A. S. ^[3]

Afiliação do(s) autor(es)

^[1] Univ Fed Fluminense, Inst Fis, Rio De Janeiro - Brazil

^[2] Univ Fed Fluminense, Dept Geoquim, Rio De Janeiro - Brazil

^[3] Univ Sao Paulo, Inst Geociencias, Sao Paulo - Brazil

^[4] Univ Oxford, ORAU, Oxford - England

^[5] Univ Minnesota, Minneapolis, MN - USA

^[6] Xi An Jiao Tong Univ, Shaanxi Sheng - Peoples R China

• Tipo de documento: Artigo Científico
• Fonte: QUATERNARY GEOCHRONOLOGY; v. 52, p. 29-36, JUN 2019.
• Citações Web of Science: 0

Resumo

Geographic and temporal variations in atmospheric carbon isotopic ratios are recorded in environmental proxies. In temperate regions, this may assist in the construction of datasets for the calibration of radiocarbon ages. Over the tropics, the high growth rate of speleothems combined with high precision Th-230 dating provides potential records for atmospheric C-14 reconstruction. In this preliminary work, we investigate the isotopic composition (delta O-18 and delta C-13) of a speleothem from central Brazil, precisely dated by the multi-collector inductively coupled plasma mass spectrometry technique (MC-ICP-MS). Radiocarbon Accelerator Mass Spectrometry (AMS) measurements were compared to the C-14 concentration in the atmosphere during the nuclear tests period based on the Bombl3SH1-2 curve. Our results show that the speleothem dead carbon proportion is less than 20% between 1932 and 1992 AD while delta C-13 values vary between -14 and -9 parts per thousand. Given that the empirical radiocarbon calibration curves for the Southern Hemisphere were constructed based on limited records, we discuss the potential and limitations of Brazilian speleothems for the evaluation of atmospheric C-14 concentrations over the last millennia. (AU)

• Processo FAPESP: 17/23687-2 - Expansão dos registros paleoclimáticos de espeleotemas coletados no Centro Oeste do Brasil
• Beneficiário: Valdir Felipe Novello
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Pós-Doutorado
• Processo FAPESP: 16/15807-5 - Reconstituição paleoclimática e paleoambiental do último período glacial no centro-oeste brasileiro
• Beneficiário: Valdir Felipe Novello
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 17/50085-3 - PIRE: educação e pesquisa em clima das Américas usando os exemplos de anéis de árvores e espeleotemas (PIRE-CREATE)
• Beneficiário: Francisco William da Cruz Junior
• Modalidade de apoio: Auxílio à Pesquisa - Temático