Optically stimulated luminescence and isothermal thermoluminescence dating of high sensitivity and well bleached quartz from Brazilian sediments: from Late Holocene to beyond the Quaternary?

Author(s):Show less -

André Oliveira Sawakuchi ; Vinicius Ribau Mendes ; Fabiano do Nascimento Pupim ; Thays Desiree Mineli ; Ligia Maria Almeida Leite Ribeiro ; Andre Zular ; Carlos Conforti Ferreira Guedes ; Paulo César Fonseca Giannini ; Luciana Nogueira ; William Sallun Filho ; Mario Luis Assine

• Document type: Journal article
• Source: BRAZILIAN JOURNAL OF GEOLOGY; v. 46, p. 209-226, Jun. 2016.

Abstract

ABSTRACT: The development of optically stimulated luminescence (OSL) dating of sediments has led to considerable advance in the geochronology of the Quaternary. OSL dating is a well established technique to determine sediment burial ages from tens of years to few hundred thousand years. Recent studies have shown that Quaternary sediments of Brazil are dominated by quartz grains with high luminescence sensitivity, allowing the determination of precise and reliable OSL burial ages. In this paper, we show examples of OSL dating of quartz aliquots and single grains from different regions in Brazil, including young coastal-eolian Late Holocene (< 100 years) to Late Pleistocene (~ 150 ka) fluvial sediments. We discuss the OSL data and ages of sediments from carbonate and terrigenous (distributary and tributary systems) fluvial depositional contexts in Brazil. Most of the studied fluvial sediments show equivalent dose distributions with low to moderate dispersion, suggesting well bleached sediments. The comparison between aliquot and single grain data suggests that high overdispersion in equivalent dose distributions of some samples is more related with sediment mixture due to bioturbation than with incomplete bleaching during transport. Well bleached fluvial sediments contrast with the poor bleached pattern usually described for fluvial sediments in the literature. A large part of the fluvial sedimentary record in Brazil is older than the age limit for quartz OSL dating using blue light stimulation. Thus, isothermal thermoluminescence (ITL) dating protocols were tested for dating of fluvial sands from the Xingu River (eastern Amazonia). The studied sample can recover reliable equivalent doses up to 1600 Gy using the ITL 310oC signal. Therefore, this signal would be suitable to extend the age limit of quartz luminescence to the whole Quaternary or beyond (> 2 Ma) in the low dose rate (0.5 - 1.0 Gy/ka) environments typical for Brazilian sediments. (AU)

• FAPESP's process: 14/14433-9 - Quaternary carbonate deposits of the Serra Bodoquena and Pantanal of Miranda (MS): geochronology and paleoclimatic aspects
• Grantee: William Sallun Filho
• Support type: Regular Research Grants
• FAPESP's process: 13/21942-4 - Quaternary sedimentary record of Parnaíba river basin, Piauí, Northeastern Brazil: a multi-proxy study for climate changes research
• Grantee: Vinícius Ribau Mendes
• Support type: Scholarships in Brazil - Doctorate
• FAPESP's process: 14/06889-2 - Paleohydrological changes, chronology of events and sediment dynamics in the quaternary of the Pantanal Wetland
• Grantee: Mario Luis Assine
• Support type: Research Program on Global Climate Change - Regular Grants
• FAPESP's process: 09/53988-8 - Acquisition of a luminescence dating system and a precision microsampler for the study of environmental changes in the Quaternary period
• Grantee: Paulo César Fonseca Giannini
• Support type: Multi-user Equipment Program
• FAPESP's process: 14/23334-4 - Coupling optically stimulated luminescence (OSL) and terrestrial cosmogenic nuclides (TCN) analysis to reconstruct changes in the Amazonian fluvial system in the Late Cenozoic (<5 ma)
• Grantee: Fabiano Do Nascimento Pupim
• Support type: Scholarships in Brazil - Post-Doctorate