High-resolution reconstruction of 8.2 ka event recorded in Belgian Holocene speleothems

• Main Authors: Allan, Mohammed, verhyden, sophie, Fagel, Nathalie
• Format: Lecture
• Language: English
• Published: 2017
• Subjects: Physical; chemical; mathematical & earth Sciences; Earth sciences & physical geography; Physique; chimie; mathématiques & sciences de la terre; Sciences de la terre & géographie physique; North Atlantic
• Online Access: https://orbi.uliege.be/handle/2268/213615

Two abrupt shifts in d18O and trace element contents of a stalagmite from the northwestern European continent (southern Belgium) suggest that two cold anomalies occurred beginning at 8.4±0.04 and ending at 8.15±0.03, possibly reflecting climatic effects associated with the 8.2 ka event. The younger of the two anomalies lasted about 30 years, from 8.18 to 8.15±0.03 ka, with a maximum d18O amplitude of 1.4‰. Trace element (Sr, Ba and Mg) peaks coincide with this second drop of d18O. The anomaly initiation is marked by Sr, Ba and Mg concentration peaks suggesting drier conditions during the coldest years, consistent with previous research in the North Atlantic. The earlier anomaly in trace element, d18O records is associated with generally cold but wet conditions at 8.4 ka, lasted 50 years, and ended abruptly. The interval from 8.4 ka to 8.15 ka was less favorable for speleothem deposition, with denser speleothem calcite deposition and lower growth rate, consistent with a cold, dry climate. The clear recovery in both temperature and rainfall between after both anomalies (8.2 and 8.4 ka), suggests that these anomalies are distinct, and may represent two episodes of AMOC weaking related to the drainage of proglacial lakes Agassiz and Ojibway.