Investigating δ13C values in stalagmites from tropical South America

<p>Multiple factors control δ<sup>13</sup>C values in speleothems and complicate their paleoclimatic and paleoenvironmental interpretation. Therefore, most studies avoid the presentation of δ<sup>13</sup>C values, and instead, focus only on δ<sup>18</sup>O. This development can be observed with regard to most recent cave studies from tropical South America, in which stalagmite δ<sup>18</sup>O were preferentially published without the consideration of δ<sup>13</sup>C data. Here we present a large δ<sup>13</sup>C dataset of 98 speleothem records covering multiple time scales from South America, of which 42 remained unpublished or were not available until now.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.</p><p>As a first approach, we review the δ<sup>13</sup>C 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 δ<sup>13</sup>C 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 δ<sup>13</sup>C and δ<sup>18</sup>O 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 δ<sup>13</sup>C values (≤6‰) in most of the speleothems.</p>