PALEOCLIMATE AND HYDROGEOLOGICAL IMPLICATIONS OF WATER SEEPING INTO JUXTLAHUACA CAVE. GUERRERO, MEXICO
Rain water, cave seepage water and spring water isotopic values follow closely the Global Meteoric Water Line, thus confirming their meteoric origin. Spring water isotopic values are lower than those of cave seepage water suggesting the former recharges at higher altitudes and more regionally. In contrast, Juxtlahuaca Cave has a local recharge consistent with its topographic location. There is an inverse relationship between the monthly weighted average δ18O and the precipitation amount of rain water. This amount effect may get transferred into the cave as the 1.5‰ decrease in the δ18O values of the seepage waters collected in October, the end of the wet season, compared to those collected in June, the beginning of the wet season. Three other controls of the seepage waters isotopic signature were tested. First, pool waters have slightly more negative values than drip waters (δ18O of -7.6 vs. -7.3 ‰, respectively). Second, water dripping faster than 1 drop/s is isotopically lighter than slower drips (δ18O of -8.1 vs. -6.8 ‰, respectively). Last, the bedrock thickness above the seepage water does not have a significative effect on the δ18O values, thus this values overlap between 1s, suggesting a homogeneous, piston-like percolation of water into the cave. Regardless, of these variations, the cave waters average δ18O is in the range measured for the rain water δ18O average confirming the speleothems utility as paleotemperature proxies.