Investigating δ13C values in stalagmites from tropical South America for the last two millennia

Environmental variability at the margin of the South American Monsoon System recorded by a high-resolution sediment record from Lagoa Dourada (South Brazil)

“…Due to the well-dated and highresolution record, also centennial climatic events of the Holocene have been detected: the 8.2 ka event and the LIA for the time interval AD 1400-1850 (Bernal et al, 2016) -both characterized by a wetter hydroclimate. A wet LIA (AD 1600-1850) with stronger SAMS is also documented by a compilation of speleothem δ 13 C data from 25 caves in tropical and subtropical South America (Novello et al, 2021). All speleothem data about the regional hydroclimate are in line with our interpretation of the high-resolution record from Lagoa Dourada, underline the environmental changes observed and provide the best possible precipitation signal, which solidifies the reconstructed surface processes that lead to the formation of the studied sediment sequence.…”

“…Based on this chronology, XRF core-scanning data together with geochemical and sedimentological studies provide high-resolution insights into responses of lacustrine and geomorphological systems to climatic variability and anthropogenic impacts. Altogether, this allows investigating a detailed regional hydroclimatic history and provides unequivocal linkages to other regional and high-resolution studies, namely the speleothem records from Caverna Botuverá (Bernal et al, 2016;Novello et al, 2021).…”

“…Thus, the isotopic record from Caverna Botuverá is linked to variability in precipitation caused by insolation-controlled fluctuations of the SAMS and provides one of the most robust climate reconstructions for South America. While the early studies of Caverna Botuverá focus on orbital to millennial timescales (Cruz et al, 2005;Wang et al, 2007), follow-up investigations obtained a much higher temporal resolution for the Holocene detecting decadal to centennial climatic variability (Bernal et al, 2016;Novello et al, 2021), data which also were used for inter-hemispheric correlation of climate modes (Deininger et al, 2020). The high-resolution δ 18 O data are supported by even higher resolving trace-element data (Mg, Ca, Sr, Ba).…”

“…However, assuming the LIA as the reason for LZ F, causative processes would not be supported by the sediment record of Lagoa Dourada. The impact of the LIA on climatic conditions that can be expected for S Brazil is increased precipitation (Bernal et al, 2016;Novello et al, 2021) leading to denser vegetation with less soil erosion. This is a process actually described for the centuries immediately prior to LZ F. Thus, we refuse the option of considering the LIA as responsible for an increase in minerogenic deposition during LZ F and find further support for a modification of the chronology (Fig.…”

Climate and environmental changes in southwestern Amazon Basin over the last 3000 years based on speleothem isotope records, Brazil

“…residence time of the water in the soil and rock) factors (Scholz, Mühlinghaus, & Mangini, 2009). Initially, the source of carbon that will ultimately precipitate as speleothems is the CO2 from both plant root respiration and decomposition of organic matter by biological activity in the soil (leading o high 𝑃 in the soil), which is then dissolved into the rainfall infiltration water (unsaturated in CO2) that continues to percolate through the cave host-rock and eventually reaches the cave (Dreybrodt, 2008;Novello et al, 2021). The acid solution acts dissolving the cave host-rock (Reactions 1-4), an interaction that usually occurs in an intermediate condition between an open and closed system, meaning the solution is in a state where it is in a partial equilibrium with CO2 reservoir from the soil (open system) and the CO2 present in the solution is continuously being consumed as it dissolves the host-rock until it is in Ca 2+ equilibrium (close system) (Fairchild & Baker, 2012;Fohlmeister et al, 2020;Novello et al, 2021).…”