New Mexico Geological Society Annual Spring Meeting — Abstracts

Up to 300 m of Bloodgood Canyon Tuff fills the Gila Cliff Dwellings basin. An extensive sheet (to 30 m thick) surrounds the basin in isolated outcrops. Current research is designed to test whether the Gila Cliff Dwellings complex represents a caldera and whether the Bloodgood Canyon Tuff originated within the Gila Cliff Dwellings complex or within the neighboring Bursum cauldron. Correlation between the Bloodgood Canyon Tuff and the mineralogically similar Railroad Canyon Tuff which occurs north of the Gila Cliff Dwellings basin is unresolved.

Analyses from three traverses through the Bloodgood Canyon Tuff within the basin and numerous analyses from Bloodgood Canyon Tuff and Railroad Canyon Tuff outside of the basin indicate that: 1) essentially no trace element or major element zonation exists from the base to the top of the Bloodgood Canyon Tuff within the basin; 2) Bloodgood Canyon Tuff and Railroad Canyon Tuff outside of the Bursum-Gila Cliff Dwellings complex are generally enriched in Zr, Y, Sr, and Ba relative to Bloodgood Canyon Tuff within the basin: 3) preliminary microprobe results indicate that sanidine crystals in distal Bloodgood Canyon Tuff are enriched in Ba relative to those in basin-filling Bloodgood Canyon Tuff.

These results suggest that there may have been at least two distinct eruptions of Bloodgood Canyon Tuff, and possibly three if the Railroad Canyon Tuff is a distinct unit. In addition, the predominant geographic separation of "enriched" tuff outside of the basin and "depleted" tuff within the basin is difficult to explain with an origin of the tuff in an eruptive center other than the Gila Cliff Dwellings complex.