Isotopic analysis on the origin of water in the marimbus wetland, chapada diamantina, brazil

The Marimbus wetland is located in a lowered valley and made up of alluvial sediment, resembling flooded sinkholes where we find a backswamp in drylands that remains permanently-to-seasonally flooded in the Chapada Diamantina. To determine the origin of the Marimbus wetland waters, isotopic analyses were performed at several points. The samples presented values of δ18O and δ2H ranging from -21.1 ‰ to 9.0 ‰ and from -3.13 ‰ to 3.31 ‰, respectively. Most of the samples presented data coinciding with the global meteorological curve. The sinkhole’s morphological features do not prove that the waters of the Marimbus wetland area are of karstic origin since the isotopic signature is within the global meteoric curve, indicating that its source was rainfall and that it is undergoing intense evaporation. They are rounded-shaped ponds typically found in alluvial fans and floodplains.