pSESYNTH project: Community mobilization for a multi-disciplinary paleo database of the Global South

How to enhance paleoscientific research, collaboration and application in the Global South? The INQUA-funded multi-year pSESYNTH project envisions the first multi-disciplinary Holocene paleo database through a collaborative vision for past human-environmental systems in the Global South, and their future sustainability

Forest stability during the early and late Holocene in the igapo floodplains of the Rio Negro, northwestern Brazil

Located at the northwestern part of the Amazon basin, Rio Negro is the largest black-water river in the world and is one of the poorest studied regions of the Amazon lowlands. In the middle-upper part of the Rio Negro were retrieved sediment cores form Lake Acarabixi, which were analyzed using pollen, spores, charcoal, and geochemistry. The aim of this study was to detect the influences from humans and river dynamics on the vegetation history in the region. Two main periods of vegetation and river dynamics were detected. From 10,840 to 8240 cal yr BP, the river had a direct influence into the lake. The lake had a regional input of charcoal particles, which reflected the effect of the dry Holocene period in the basin. Furthermore, highland taxa such as Hedyosmum and Myrsine were found at that time along with igapo forest species that are characteristic to tolerate extended flooding like Eschweilera, Macrolobium, Myrtaceae, Swartzia, and Astrocaryum. During the late Holocene (1600 to 650 cal yr BP), more lacustrine phases were observed. There were no drastic changes in vegetation but the presence of pioneer species like Vismia and Cecropia, along with the signal of fires, which pointed to human disturbances

Chronostratigraphy of a 1.5 +/- 0.1 Ma composite sedimentary record from Colonia basin (SE Brazil) : bayesian modeling based on paleomagnetic, authigenic Be-10/Be-9, radiocarbon and luminescence dating

We present a new 52 m composite record (COL17c) composed of five sedimentary sequences retrieved from the Colonia basin (Southeastern Brazil). The COL17c record is composed of two main sub-units deposited under different regimes: a peatland above similar to 14 m and lacustrine sediments below. Sedimentary description and core scanning (MSCL and XRF) are first used to align individual cores in order to produce a nearly continuous composite record. We then established an original chronological framework based on radiocarbon, paleomagnetic, optically stimulated luminescence (OSL), post-infrared infrared stimulated luminescence at elevated temperature (pIRIR(290 degrees C)) and authigenic Be-10/Be-9 dating. We describe the protocols used for each technique and discuss the positive and negative results, as well as their implications for proxy interpretation. In spite of negative results of some techniques, mainly due to the absence of adequate sample material, the multi-proxy approach used is essential to maximize the chances of obtaining a satisfactory age model for this unique continental sedimentary sequence. All valid chronological proxies, comprising three AMS C-14 ages, one pIRIR(290 degrees C) age, two paleomagnetic constraints and eight authigenic Be-10/Be-9 datum, are integrated within a Bayesian age-depth modeling to produce a 1.5 +/- 0.1 Ma chronology for the whole COL17c sequence. This age model represents the first long-term chronological estimate of sediments deposition in the Colonia basin. The record allows to refine the age of the Colonia basin formation between 5.3 and 11.2 Ma, much older than previously estimated from short sedimentary cores