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

Author(s):Show less -

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]

Affiliation

^[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

• Document type: Journal article
• Source: QUATERNARY GEOCHRONOLOGY; v. 52, p. 29-36, JUN 2019.
• Web of Science Citations: 0

Abstract

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)

• FAPESP's process: 17/23687-2 - Expansion of the paleoclimate records of speleothems collected in the mid-west of Brazil
• Grantee: Valdir Felipe Novello
• Support type: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 16/15807-5 - Paleoclimate and paleoenvironmental reconstructions over the last glacial period in the mid-west Brazil
• Grantee: Valdir Felipe Novello
• Support type: Scholarships in Brazil - Post-Doctorate
• FAPESP's process: 17/50085-3 - PIRE: climate research education in the Americas using tree-ring speleothem examples (PIRE-CREATE)
• Grantee: Francisco William da Cruz Junior
• Support type: Research Projects - Thematic Grants