STABLE ISOTOPE RECORD OF A METRO CAVE SPELEOTHEM FOR THE ANALYSIS OF PLEISTOCENE AND HOLOCENE CLIMATE CHANGE IN WESTLAND, NEW ZEALAND

New Zealand paleoclimate records are crucial for understanding the regional effects of rapid North Atlantic deglacial events in the mid–latitudes of the Southern Hemisphere. A new stable isotopic record from a stalagmite in Metro Cave on the West Coast of New Zealand presents a potential climate stratigraphy that correlates with other proximal speleothem and regional terrestrial proxies. Changes in texture from translucent and finely laminated to opaque and feathery along the approximately 1 m speleothem indicate a middle region where kinetic fractionation dominated (Hendy test, r²=0.83), which suggests a drier and potentially colder climate that may correspond to a large deglacial reversal, such as the Younger Dryas or Antarctic Cold Reversal. Samples drilled at 2.5 mm resolution along the length of the speleothem were analyzed for δ¹⁸O and δ¹³C. Temperature reconstructions show an unlikely shift of 9 degrees C from this middle region to the end of the stalagmite, which implies the influences of hydrological variation on the isotope record and has potentially important implications for Westerly paleointensity. Radiocarbon dates from 13 points along the speleothem show a maximum age of 20.3 ka; however, likely distortion due to diagenesis in the middle section indicates U-Th dating (underway) will be necessary to create an improved age model. With the addition of U-Th dates, correlation of this record to other New Zealand speleothem and terrestrial climate proxies will help to illuminate the temperature and hydrology that is recorded in Metro Cave stalagmites, the paleointensity of Westerly flow on New Zealand’s West Coast, and global teleconnections between the hemispheres during major climatic events.