Paper No. 7
Presentation Time: 9:45 AM
COMPARING ZIRCON CRYSTALLIZATION AGES BETWEEN VOLCANIC ASH IN MAYA CERAMICS AND TIERRA BLANCA JOVEN PUMICE (ILOPANGO VOLCANO, CENTRAL AMERICAN VOLCANIC ARC)
The discovery of volcanic ash-tempered pottery in Late Classic Maya sites (CE 600-900) has prompted speculation as to the source eruption of the ash. Located in the limestone Maya lowlands, the presence of an unweathered ash is anomalous. The ash is glassy and preserves cuspate morphology, indicating an origin from a distal pyroclastic fall-out. Whereas some have proposed trade of either the raw material for temper or the pottery itself, local procurement of the ash may be more likely. Based on the volume and timing of the Tierra Blanca Joven (TBJ) eruption, Ilopango volcano (Central American Volcanic Arc) is a potential source of the Maya pottery ash. Compositional modification of the temper ash during firing has limited the applicability of chemical correlation with potential source eruptions. A novel approach is to utilize crystallization ages of zircons associated with the pottery ash as an alteration-resistant indicator of tephra provenance. Zircon crystallization ages are being determined in-situ and in grain mount by Secondary Ionization Mass Spectrometry in selected pottery sherds and TBJ pyroclastic deposits. Zircon in the pottery is euhedral, shows igneous oscillatory zonation in cathodoluminescence, and is in part mantled by glass. Zircon crystallization ages within the Late Classic Maya pottery ash are distinctly older (late Cenozoic, ~10-30 Ma) than those within the TBJ deposits, which are late Pleistocene (< 30 ka), with the exception of a crystal interior ~15 Ma in age. Because of this age discrepancy, there appears to be no association between Maya pottery ash and the studied Ilopango deposits. Analyses of additional samples of Maya pottery and ash are underway to more firmly establish the probability of Ilopango or other regional volcanoes being the source of the tempered Maya pottery ash.