The timing and structure of the 8.2 ka event revealed through high-resolution speleothem records from northwestern Madagascar
Abstract
Although the 8.2 ka event is a well-known globally documented abrupt climate event, its detailed expression in tropical southeastern Africa is poorly constrained. Here we present a high resolution and precisely dated record of the regional hydroclimatic variability between 8.5-7.5 ka BP from a polymorphic speleothem (ABC-1) from northwestern Madagascar. In combination with the exclusive recurrences of calcite layers (indicative of wetter conditions), the distinctly negative excursions in the ABC-1 δ18O record manifest a wet 8.2 ka event that spanned from 8.230 to 8.053 ka BP. The event is characterized by the replacement of shorter-term (interannual to interdecadal) δ18O-δ13C coherence with the longer-term (multidecadal to centennial) coherence, suggesting a stable and well-developed forest system during the 8.2 ka event. Our data reveal a two-stage structure of the 8.2 ka event, which is superimposed with two brief pluvial episodes in each stage. The widely documented two peaks/troughs during Stage-I suggest rapid propagation of climate signal through atmospheric processes triggered initially by the freshwater forcing, whereas the divergent behaviors of the peaks/troughs in Stage-II in different climate systems may suggest a different forcing.
- Publication:
-
Quaternary Science Reviews
- Pub Date:
- September 2021
- DOI:
- 10.1016/j.quascirev.2021.107104
- Bibcode:
- 2021QSRv..26807104D
- Keywords:
-
- Speleothem;
- Madagascar;
- The 8.2 ka event;
- Two-stage structure