Charcoal concentrations from radiocarbon-dated lake sediments in the Brazilian Pantanal

Sediment samples were extracted at a 1 cm resolution through the studied cores and their volume measured using water displacement. Clay rich sediments (LM and LC) were treated with 200 ml of 7 % sodium hexametaphosphate (Na6P6O18) and organic rich sediments (MIM) in 200 ml of 10 % potassium hydroxide (KOH). Samples were deflocculated on a hot plate for 30 minutes at 80 oC. Residues from the organic rich sediments were additionally washed in deionized water and placed in 7 % hydrogen peroxide (H2O2) for 24 hours at room temperature. The residues were sieved at 125 μm and 250 μm. Residues were counted at 125 μm and 250 μm under a low powered microscope in a bogorov tray. Raw charcoal counts were converted to a concentration (particles cm3). Sediment samples were obtained from discrete horizons from each core and sent for radiocarbon dating at commercial laboratory facilities.