Incision and aggradation phases of the Amazon River in central-eastern Amazonia during the late Neogene and Quaternary

Extended-Range Luminescence Dating of Central and Eastern Amazonia Sandy Terrains

“…Although the possibility of the TT-OSL ages indicating only the minimum age cannot be ruled out, considering the low thermal stability of TT-OSL signals (Li and Li, 2006;Chapot et al, 2016;Faershtein et al, 2018). Our TT-OSL ages ranging from almost 2 Ma matches other fluvial terraces of the Amazon River with TT-OSL depositional ages ranging from 556 to 1,063 ka (Bezerra et al, 2022). The much younger OSL ages at the top of the Autazes core, from 1 to 25 ka, might represent the accumulation of fluvial sediments during major flooding events during the Late Pleistocene and Holocene (Pupim et al, 2019).…”

“…OSL and TT-OSL ages constrain the formation of open and closed vegetation sandy substrates in lowland Amazonia, in both shallower and deeper profiles, extending the dated ages based on luminescence dating methods. The terraces dated previously using TT-OSL (Pupim et al, 2016;Bezerra et al, 2022) and the Autazes drill core (Kiefer et al, 2019) have both surface features and sedimentary structures that suggest fluvial deposition. However, many sandy terrains covered by savanna-like vegetation in lowland Amazonia lack surface depositional features or sedimentary structures, and correspond to massive, weathered sands covering Cretaceous-Paleogene and Miocene-Pliocene fluvial sandstones (Gautheron et al, 2022).…”

“…The suitability of both OSL and TT-OSL SAR protocols for estimation of D e under laboratory conditions was evaluated by dose recovery tests (data summary of dose recovery tests on Supplementary Tables S1, S2). The dose recovery tests performed by Bezerra et al (2022) on samples from the same study area were also used for evaluation of the suitability of the TT-OSL protocol. OSL average calculated-to-given dose ratio is 0.96, and TT-OSL average calculated-to-given dose ratio is 1.5 (Supplementary Table S2).…”

“…Therefore, extendedrange chronologies of sedimentary substrates supporting upland vegetation in Amazonia are crucial to understand the evolution of the landscape during the Quaternary and Neogene and its relation to the current biodiversity and biogeographical patterns of the biome. The Pliocene and Quaternary lowland fluvial record in Central Amazonia is composed of heavily weathered siliciclastic and non-fossiliferous deposits, suitable for the application of quartz-based dating techniques (e.g., Soares et al, 2010;Pupim et al, 2019;Bezerra et al, 2022), as feldspar is frequently lacking due to heavy weathering. Most of the reliable ages that constrain sedimentation in these sequences are based on optically stimulated luminescence (OSL) dating of quartz (e.g., Rossetti et al, 2015;Cremon et al, 2016;Pupim et al, 2019) and are restricted to the last 300 ka.…”

“…Despite the routine use of TT-OSL dating in recent years, only few studies use this technique in geological settings of South America (e.g., Pupim et al, 2016;Bezerra et al, 2022). In addition to the understating of the evolution of the Amazonian landscape in the Pliocene and Quaternary, TT-OSL dating protocols still need to be tested in different geological contexts, including South America, as quartz OSL properties are not uniform and also vary at a grain-tograin level (Preusser et al, 2009), and the same might be valid for the TT-OSL signal.…”