A high resolution climate reconstruction from annually laminated tufa deposits of the Qilian Mountains, NW China
Zusammenfassung der Projektergebnisse
A mid Holocene tufa carbonate section in the Qilian Mountains provided an annually resolved δ18O and δ13C record which is compared to Recently formed tufa carbonate. Significantly lower δ18O values for the mid Holocene tufa carbonate indicate that climatic conditions were probably wetter at the northern margin of the Tibetan Plateau about 4000 years ago compared to present-day conditions. The sampled section comprises about 360 years of annually layered white-dark carbonate couplets. δ13C values do not differ between mid Holocene and Recent tufa carbonate and show that significant differences in the catchment vegetation density and composition are unlikely. It was not possible to sample a long carbonate section which spans a relatively long part of the Holocene stretching continuously into Recent times due to the large discharge of the springs during the field survey in September 2005 and steeply overhanging slopes. The sampled tufa carbonate shows comparatively thick white-dark couplets representing the annual precipitation of carbonate. On average, 1.1 cm of relatively dense carbonate was formed per year. Therefore, the 3.90 m thick section spans about 360 years only. First results of the project were already presented during the „Lange Nacht der Wissenschaften“ („Long Night of the Sciences“) at the Freie Universitaet Berlin in June, 2007.
