Stable isotopes of speleothems from the Yucatan Peninsula, Mexico

Two stalagmites, SAN-H and TABI -I were collected from caves in the northern Yucatan Peninsula to analyze for the stable isotopes of carbon and oxygen. The delta13C value can be used to determine whether C3 or C4/CAM vegetation was dominant and the delta 18O value can theoretically be used to determine whether the climate was wet or arid. Samples were cut, polished, dated using U/Th dating, and sampled using a micromill. SAN-H was dated as Early Classic (1650-1350 B.P.) to the Middle Preclassic 2850-2250 B.P) and the delta13C and delta18O appears to reinforce the interpretations from similar studies. The range of isotope values for delta18O and delta13C were -2.3 to -5.5‰ and -4.0 to -10.3‰, respectively. Although the U/Th dates for TABI-I range from Historical to Late Classic(1350-1050 B.P.), the early Late Classic date is almost certainly invalid, and is the result of presence of clastic material in the sample. TABI-I's range of isotope values for delta18O and delta 13C were --2.1 to -4.9‰ and --4.7 to -9.6‰, respectively. TABI-I's delta18O values appear to be supportive of interpretations found in the literature based on lakecore, stalagmite and sediment studies, and delta13C values could be informative about possible vegetation and land use in the immediate vicinity. Problems with dating reversal and dating accuracy prevented more detailed interpretations of the data.