A STRATIGRAPHIC RECORD OF TROPICAL CYCLONE LANDFALL IN A STALAGMITE FROM A LOW-LYING CAVE IN YUCATáN, MEXICO

Paleotempestology, the study of ancient storms, is beginning to impact our understanding of the role that tropical cyclones play in the climate system. Paleotempestology is also growing thanks to new techniques for identifying large storm events in various climatic records. This research aims to develop an inexpensive approach to developing first order storm frequency chronologies using clastic sedimentary deposits within calcite stalagmites from low-lying karst regions. The caves in the Yucatán Peninsula are interconnected and many are partially submerged when the water table is at its normal height. These caves flood when hurricanes move over the area, washing in soil debris and resuspending cave mud. Mud is deposited on the cave walls, floor, and free-standing speleothems as the water table subsides. As calcite deposition resumes for the actively-growing stalagmites, the record of the storm is preserved as a mud layer. Stormwater infiltration is delayed by percolation time between the surface and the cave. Thus, we expect the low stable oxygen isotope isotope ratio (δ¹⁸O value) signature of the tropical cyclone rainwater to depress δ¹⁸O values of stalagmite calcite after the mud layer is deposited.

Stalagmite CH-1 was collected from the cave Chaltun-Ha outside the village of Huhí in the Mexican state of Yucatán in July, 2007. Sectioning reveals mud interbedded within a laminated calcite speleothem. Here we present a test of the depositional model outlined abovefor a stratigraphic tropical cyclone record. We have developed an age model using both radiometric and layer-counting approaches. The assumption of annual layers in CH-1 is tested by growth rate comparisons with ²¹⁰Pb, and ¹³⁷Cs dating techniques. Following methods of Frappier et al. (2007), we use stable isotope analysis to test for tropical cyclone-generated rainfall influences on the CH-1 record. Finally, we test the stalagmite record of modern hurricane events in the region by correlating the mud layer chronology to recent climate and local hurricane history.