New Mexico Geological Society Annual Spring Meeting — Abstracts

Sixty travertine mounds are clustered along the Little Colorado River in the Springerville volcanic field in Arizona near Lyman Lake and along two trends 5-10 km to the west and east of the river. Travertine vents align with previously mapped northwest-trending Quaternary faults and folds that reflect contemporaneous strain at the southern boundary of the Colorado Plateau - Basin and Range transition zone just to the south of the site. Travertine mounds with central vents resemble shield volcanoes and cinder cones in both morphology and mode of accumulation. These travertine deposits provide a natural laboratory for studying the interaction of magmatism, deeply sourced fluids, CO₂ migration and flux, neotectonics, and the evolution of drainages.

Local springs and groundwater show appreciable variability in chemistry. The travertinedepositing springs are warmer (18.1° C), lower pH (6.8), and have higher TDS (1835 ppm) and trace metal concentrations than waters from nearby groundwater wells. Gas composition data from the springs show very high CO₂, active CO₂ degassing, and high ³He/⁴He (R_a of 0.58), indicating input of endogenic fluids from below the aquifer.

Studies of the travertines themselves will address several hypotheses. U-Series dating and detailed field studies of relative timing relationships will evaluate the timing of travertine deposition, and whether travertine deposition episodes coincided with either volcanic episodes and/or wet times in the paleoclimate record. Dates on travertine-cemented river gravels offer the potential to date the incision of the river and changes through time of the locus of travertine mound spring deposition and the river.

The Springerville volcanic field is a major center of recent (3.0 – 0.3 Ma) magmatism at the intersection of the southeastern margin of the Colorado Plateau and the Jemez lineament. Existing data suggests spatial and temporal interconnections between Quaternary volcanism and travertine deposition. A swarm of nearly identical upper crustal microearthquakes ranging in magnitude from ~2.0 to ~4.0 occurred directly south of the area in December 2004, indicating active tectonism in the region. The Springerville "chemical volcanoes" may provide a record of continued neotectonic activity.