Investigating δ13C values in stalagmites from tropical South America

Multiple factors control δ¹³C values in speleothems and complicate their paleoclimatic and paleoenvironmental interpretation. Therefore, most studies avoid the presentation of δ¹³C values, and instead, focus only on δ¹⁸O. This development can be observed with regard to most recent cave studies from tropical South America, in which stalagmite δ¹⁸O were preferentially published without the consideration of δ¹³C data. Here we present a large δ¹³C dataset of 98 speleothem records covering multiple time scales from South America, of which 42 remained unpublished or were not available until now. Our main objective is concentrating on the support of existing and emerging databases, such as SISAL, and providing new data for the speleothem community and climate modelling.

As a first approach, we review the δ¹³C values for the last two millennia and evaluate the environmental influencing factors on this proxy, e.g., local hydroclimate, altitude, temperature, and abundant vegetation types. Our results indicate that the main factors controlling variations in δ¹³C values are due to changes in the local hydroclimate and, to a minor extent, in temperature. For this time period, most of the isotope records show a significant correlation between the δ¹³C and δ¹⁸O values, indicating a close relationship between local hydroclimate and large-scale atmospheric processes related to shifts of the South American Monsoon System (SAMS). Furthermore, in most of the karst systems studied here, the predominant occurrence of C3 plants growing on soils above the caves is responsible for a considerable lowering of δ¹³C values (≤6‰) in most of the speleothems.