RE-EVALUATING PLEISTOCENE SEA LEVEL HISTORY AND SPELEOGENESIS IN THE YUCATAN PENINSULA: U-TH DATING OF POS FROM QUINTANA ROO, MEXICO
Extensive shallow caves in Quintana Roo provide access to modern water table transects perpendicular to the coastline. POS above and below modern water table have been dated by U-Th methods to further constrain sea levels and cave ages. Preliminary U-Th ages from a stalactite in Jaguar Claw Cave yields an age of ~252 ka BP, and POS (~+7.2 amsl) of ~49 ka BP. Current sea level proxies suggest the latter was a sea level low stand (-40m). Folia from two samples ~1.4m amsl suggest a high stand at ~251 ka BP. Interior stalactite ages yielded ages of ~340 ka BP. Another sample from the same cave at ~1m amsl is 646 ka BP, with overgrowth of 404 ka BP. Additional samples from Solstice cave about 1.5m amsl yield dates of 110 ka BP for the overgrowth and 212.5 ka BP for the interior stalactite.
These results suggest that the caves above modern sea level were considerably larger and subaerial earlier than has been assumed, and suggests that CO2-driven dissolution at the water table may be important to speleogenesis, rather than exclusively salt-freshwater mixing. Extensive speleogenesis above modern sea level, and older than MIS5 high stand, suggests sea level records may be incomplete and challenges the assumption of regional tectonic stability.