Wavelet analysis of δ18O and δ13C time-series from an Holocene speleothem record from Corchia Cave (central Italy): insights for the recurrence of dry-wet periods in the Central Mediterraneans

In this work, the continuous wavelet transform (CWT) is used to analyse stable isotope (δ 18 O and δ 13 C) time-series from a speleothem from Corchia Cave (Apuan Alps, Tuscany, central Italy). The record spans the ca. 13.3- 0.4 ka period. Both proxies are thought to represent changes in the amount of precipitation and in the hydrological recharge over the cave catchment, and to indicate alternating wetter and drier periods. The CWT shows the presence of different dominant frequency components, changing across the Middle-Holocene. This can be in- terpreted as mostly related to long term variations in summer and winter insolation, resulting from changes in orbital parameters. The lower frequencies (millennial scale) individuated may have different origin, not always obvious, and are rarely reported in others records. Instead, the short period components (multidecadal to centennial scale) could be in the range of frequencies considered as expression of the solar variability. δ 18 O and δ 13 C time-series show very coherent re- sponse to lower frequencies, but δ 18 O time-series show the presence of higher frequencies, that are not reported in the δ 13 C record. This can be related to a different response of the soil-karst system compared to variability in the δ 18 O of precipitation and their recharge of the karst. A Matlab® code has been implemented to compute the wavelet trans- form and to generate all the results presented in this work.