| Title: |
Dating kaolinite from the Neogene Içá Formation and overlying laterites, central Amazonia, Brazil: Constraints for a stratigraphic correlation |
| Authors: |
Allard, Thierry; Pereira, Luciana; Mathian, Maximilien; Balan, E.; Taitson Bueno, Guilherme; Falguères, Christophe; Do Nascimento, Nadia Regina |
| Contributors: |
Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC); Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement IRD : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS); Companhia de Pesquisa de Recursos Minerais (CPRM); Serviço Geológico do Brasil (SGB); Universidade Federal de Goiás Goiânia (UFG); Histoire naturelle de l'Homme préhistorique (HNHP); Muséum national d'Histoire naturelle (MNHN)-Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS); Instituto de Geociencias e Ciencias Exatas (DEPLAN/IGCE/UNESP); Instituto de Geociências e Ciências Exatas; CAPES COFECUB (Te76012) and PICS/CNRS french-brazilian programs |
| Source: |
ISSN: 0031-0182. |
| Publisher Information: |
CCSD; Elsevier |
| Publication Year: |
2020 |
| Collection: |
Université de Perpignan: HAL |
| Subject Terms: |
sediments; radiation-induced defects; artificial irradiation; dosimetry; electron paramagnetic resonance; geochronology; [SDU]Sciences of the Universe [physics]; [SDE]Environmental Sciences |
| Description: |
International audience ; 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. |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| DOI: |
10.1016/j.palaeo.2020.109818 |
| Availability: |
https://hal.science/hal-03047224; https://hal.science/hal-03047224v1/document; https://hal.science/hal-03047224v1/file/Allard_2020_PalPalPal.pdf; https://doi.org/10.1016/j.palaeo.2020.109818 |
| Rights: |
https://about.hal.science/hal-authorisation-v1/ ; info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.31F8B9BC |
| Database: |
BASE |