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DOI	10.1016/j.palaeo.2020.109818
	Dating kaolinite from the Neogene Içá Formation and overlying laterites; central Amazonia; Brazil: Constraints for a stratigraphic correlation
	Allard T.; Pereira L.; Mathian M.; Balan E.; Taitson Bueno G.; Falguères C.; do Nascimento N.R.
发表日期	2020
ISSN	0031-0182
卷号	554
英文摘要	The Neogene Içá Formation is a major sedimentary deposit in central Amazonia (Brazil) that is critical to the understanding and modeling of the evolution of the Amazon Basin. However, its chronostratigraphy is poorly defined, mostly because it is not fossiliferous and it does not contain volcanic ash levels. This study is the first attempt at the absolute dating of the sediments and overlying soils of the Içá Formation by electron paramagnetic resonance (EPR) of radiation-induced defects in kaolinite (RIDs). Four profiles of unconsolidated sediments overlaid by lateritic soils from the Barcelos region (Amazonia, Brazil) were studied. The concentration of RIDs was assessed from EPR spectra through a simplified procedure on a selected set of samples, excluding those showing too strong of interference from the signal of trace vanadyl complexes. It is shown that in such sedimentary material, both the microscopic distribution of thorium (together with uranium) and the origin of kaolinite, either detrital or authigenic, are critical for kaolinite dating. Considering an argued authigenic origin and two scenarios of Th distribution, it appears that most of the present chronologic data support the stratigraphic correlation with the Madre de Dios sedimentary Formation in Peru previously proposed in the literature for the Içá Formation (9.5–2.5 Ma). This study also shows a rejuvenation process of kaolinite both in the uppermost soil and at depth of the profiles. This rejuvenation occurred during paleoclimatic periods already revealed in other weathering covers from the Amazon Basin and possibly resulted from downward weathering in the topsoil and water table or lateral weathering at depth. © 2020 Elsevier B.V.
英文关键词	Artificial irradiation; Dosimetry; Electron paramagnetic resonance; Geochronology; Radiation-induced defects; Sediments
语种	英语
scopus关键词	authigenesis; chronostratigraphy; kaolinite; laterite; lithostratigraphy; soil analysis; soil depth; stratigraphic correlation; volcanic ash; Amazonia; Peru
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/150429
作者单位	IMPMC, UMR CNRS 7590, Sorbonne Université, Paris, France; CPRM, Serviço Geológico do Brasil, Brazil; UFG, Universidade Federal de Goiás, Brazil; IPH, UMR7194, 1 rue René Panhard, Paris, France; UNESP, Universidade Estadual Paulista, Rio Claro, Brazil
推荐引用方式 GB/T 7714	Allard T.,Pereira L.,Mathian M.,et al. Dating kaolinite from the Neogene Içá Formation and overlying laterites; central Amazonia; Brazil: Constraints for a stratigraphic correlation[J],2020,554.
APA	Allard T..,Pereira L..,Mathian M..,Balan E..,Taitson Bueno G..,...&do Nascimento N.R..(2020).Dating kaolinite from the Neogene Içá Formation and overlying laterites; central Amazonia; Brazil: Constraints for a stratigraphic correlation.Palaeogeography, Palaeoclimatology, Palaeoecology,554.
MLA	Allard T.,et al."Dating kaolinite from the Neogene Içá Formation and overlying laterites; central Amazonia; Brazil: Constraints for a stratigraphic correlation".Palaeogeography, Palaeoclimatology, Palaeoecology 554(2020).