A SOUTHWEST MISSOURI SPELEOTHEM ISOTOPIC RECORD, A COMPARISON OF STANDARD AND NOVEL ANALYTICAL TECHNIQUES

A stalagmite from Hensen cave, located in southwestern Missouri (MacDonald County), has been analyzed for carbon and oxygen isotopic variations. The samples were milled using a 0.5mm dental burr. The masses ranged from 4 to 9 milligrams. Spatial resolution was greater than 1mm though did not exceed 5mm. Isothermal common-acid bath off line preparation using phosphoric acid was employed. The results showed secular variations in the values in both isotope systems. These results were compared with sampling done utilizing two novel technologies, computer aided micromilling and a gas bench mass spec peripheral. Selected regions of the sampled formation were analyzed at a spatial resolution as low as 80 um and mass range of 100 to 300 ug. Forty data points were accrued using the more traditional milling and preparation technique. The micromilling and gas bench yielded more than 170 points. The results provide information on the isotopic variations in speleothems at a resolution not previously available for the western Ozark Plateaus region.