A CHRONOLOGY OF BIG PLEISTOCENE EVENTS FROM CREVICE CAVE, MISSOURI

The well-dated speleothem record from Crevice Cave, Missouri covers nearly 400,000 years and captures paleoclimate information through various proxies, including stable isotopes, flood laminae, growth onset and cessation, and breakage (possibly by earthquakes). There are a number of highlights in the record. Speleothem deposition was abundant during much of the last glacial period from MIS 5-2, but slowed and ceased during the late glacial, suggesting cold/dry conditions. Something also broke large numbers of speleothems during the late glacial; one possibility is earthquakes related to unloading of the Laurentide ice sheet. The speleothem record documents a large transition in climate around 55 ka, from warmer to cooler conditions and including all the millennial-scale frequency variation seen in the Greenland ice core record superimposed on the larger trends. One of the most unique periods is early MIS 4, from 74 to 72 ka, a time when global ice buildup was occurring rapidly, yet conditions at Crevice Cave were distinctly non-cold. A comparison between MIS 5e and the Holocene reveals some distinct differences between the two interglacial periods. The 5e record contains a distinct prairie period between forested intervals, while the Holocene is less distinct in its structure. Finally, the flood laminae record reveals that the Holocene is unique in the last 400,000 years in its frequency of large flood events. The most active period of flooding in the last 400,000 years was from 900 to 600 years ago.