OSL Dating Applied to Quaternary Deposits of the Mariuá Archipelago, Negro River, Amazon

Abstract

In the Amazonian region, where quartzose sand sediments are abundant, OSL dating provides a direct method for establishing the depositional timing of sediments, thereby aiding in understanding the Quaternary River dynamics of the area. This is particularly valuable in reconstructing past environmental changes, such as shifts in river courses, sedimentation patterns, and climate variations. The present study was conducted in the Mariuá Archipelago in the middle course of the Negro River (Western Amazon), a vital area for biodiversity preservation, focused on analyzing sediment samples collected on the river terraces and bars of the archipelago. These samples underwent analysis using optically stimulated luminescence (OSL) techniques specifically applied to quartz crystals found within the sediments. This allowed researchers to determine the ages of the sediments. The SAR OSL dating protocol, combined with a Central Age Model, was employed in the analysis, resulting in promising outcomes. The estimated average equivalent dose obtained from the analysis led to the determination of ages for various terraces and bars within the range of 0.41 to 135.1 ka. These age determinations provide valuable insights into the geological history and environmental changes that have occurred in the Mariuá Archipelago over millennia, contributing to the understanding of sedimentation, ecological evolution, and biodiversity dynamics.