8.2 K EVENT IN VENEZUELEAN SPELEOTHEMS

The 8.2 k Event was first noticed clearly in Greenland ice cores. It is believed that a marked cooling occurred at this time which has been attributed to the last stages of the deglaciation of the Laurentide and Scandinavian ice sheets. Originally the effect was thought to be only regional but recent evidence shows that the 8.2 k Event may be a global event.

We have evidence from a spleleothem collected in Venezuela that the 8.2 k event was associated with higher than normal monsoonal precipitation in northern South America. U-Th-ages of a 25 cm long stalagmite from Venezuela reveal a rapid increase in the growth rate contemporaneously with the 8.2 k Event. Preliminary dating of growth layers and speleothem age modeling using the StalAge program show that the increased growth started about 8.70 ± 0.11 kyr B.P. and continued for about 800 years. The growth rate increased from as low as 2.3 E-3 mm/a before the 8.2 k Event up to 4.3 E-1 mm/a during the event. The fast growing section is defined by 5 dating points and makes up about 50 % of the analyzed stalagmite.

It is thought the large increase in glacial melt water changed the rate of Meridional Overturning Circulation, which in turn, affected the North Atlantic basin and the position of the Intertropical Convergence Zone, resulting in the observed low-latitude monsoonal precipitation patterns.