High-precision radiocarbon dating of dead and fossil tree trunks from the National Park Cavernas do Peruaçu for confirmation of tree-ring annual formation and past climate studies

Abstract

Greenhouse gas emission produced by human activities has raised earth's temperature, disturbing forests and interfering with the biogeochemical cycles. To understand the impact of future changes, it is necessary to look backward, for the pre-industrial climatic variability. Natural archives including the tree rings provide pre-instrumental information of environmental variability at annual resolution. Since trees only reach an average 200 years old in the tropics, the construction of long records of environmental variability requires sampling tree rings from the dead and fossil trees. However, finding long-dead trees and or fossil trees is difficult in the tropics because the conditions are not ideal for wood preservation. These conditions were found in the karstic regions from Central-Eastern Brazil, where caves arround the rivers hold a dry environment allowing the preservation of trunks from few tree species. Such trunks were, probably, removed from the surrounding vegetation by large flooding events that transported them to the caves. In this study, we will use radiocarbon dating to test tree-ring annual formation in the tree species from the fossil trunks using the bomb-peak method, as well as to accurately date these samples using the wiggle-match approach. These samples consist of rare records that will be used for the reconstruction of the climate and past extreme flooding events of the Peruaçu river during the last millennia. The strategic geographical position of the Cavernas do Peruaçu National Park at central-eastern Brazil will allow the construction of long records that may provide information about climatic variation related to the South American Monsoon hydroclimatic system. Such data will provide more realistic information to climatic models, aiding prediction of extreme events caused by the rise in atmospheric temperature and climate change. (AU)