Radiometric and stimulated luminescent characterization of Amazonian sediments from the Middle Rio Negro, Western Amazon

The sediments were collected from paleodunes, river terraces, islands, and sand bars at Mariu & PRIME;a Archipelago, Rio Negro, Brazil. XRD analysis revealed that quartz is the predominant mineral along with a trace quantity of kaolinite. Neutron activation analysis of the sediments revealed the assembly of rare-earth elements, metals and semi-metals. The values of U and Th were found to be 3-5 ppm in paleodunes and 9-16 ppm in terraces, and K-40 concentration is below detectable limit. The OSL of quartz (dune) is composed of three components with decay times of 0.2, 11.0 and 350 s, respectively. This OSL emission is related to the TL peaks below 380 & DEG;C. Also, phototransferred TL is observed in the temperature range of 190-250 & DEG;C for a blue stimulation of 500 s. TL peaks kinetic parameters were calculated and discussed. The lifetimes of TL peaks at 272 and 355 & DEG;C are approximately 4.0x104 and 1.5x109 years, respectively. Using the conventional SAR protocol, 11 samples were dated, including two old paleodunes with ages of 124.4 and 169.7 ka, increasing the age interval of the site, the other samples were younger sediments, with ages between 0.39 and 53.9 ka.

Automated summary

The sediments collected from different locations in the Mariu Archipelago, Rio Negro, Brazil were analyzed. Quartz was found to be the predominant mineral in the sediments, along with a trace quantity of kaolinite. The sediments were also found to contain rare-earth elements, metals, and semi-metals. The characteristics and lifetimes of the quartz's thermoluminescence peaks were determined, and the samples were dated using the conventional SAR protocol.