A record of more than 500,000 years of large-volume travertine formation in the southwestern United States and links between paleohydrology, paleoclimate, and landscape evolution

CO₂ springs and associated travertine deposits offer a unique tool to better understand Cenozoic paleohydrology and paleoclimate in the context of geomorphic and neotectonic evolution of the southwestern United States. Travertine accumulations represent places of persistent and significant mantle CO₂ degassing in high discharge spring systems that are found along faults and above magmatic systems. They complement speleothem records from the same regions in that they can provide better links to the surface geomorphic and neotectonic systems. New Mexico and Arizona host several exceptionally well-preserved, large-volume travertine deposits that extend from 10 - 60 km², with thicknesses ranging from 15 to more than 60 m. Precise U-series and stable isotope analyses are underway for large travertine platforms at Mesa del Oro, NM (~27 km²), Riley North and South Mesa, NM (~60 km²), Mesa Aparejo/Belen Quarries, NM (~13 km²), and Springerville, AZ (~30 km²). New ages for the travertine deposits at Mesa del Oro are 56 ka, 253 ka, 361 ka, and more than 500 ka. The travertine deposits at Riley North and South Mesa are older than 500 ka and 207/287 ka, respectively. At Mesa Aparejo, travertine ages are 312 ka and more than 500 ka. U/Th dates from Springerville, AZ show that major travertine accumulations occurred over several time intervals: 36-100 ka, 200-280 ka and 300-350 ka. Stable isotope analyses overlap substantially, exhibiting high δ¹³C values, +2.0% to +8.3%, and δ¹⁸O values that range from -13.5% to -4%. High δ¹³C values are interpreted to be caused by rapid CO₂ degassing while the range of δ¹⁸O values is interpreted to represent changing water temperatures and mixing trends of groundwater. U-series data show that travertine deposition at all of these localities overlapped temporally and that major aggradation and high volume deposition was not steady, but occurred episodically at 36-100, 200-280, and 300-380 ka. Times of high accumulation rates are interpreted as times of high groundwater flow and hence as a proxy for regional paleohydrology/paleoclimate controls while the locations of the travertine occurrences (along faults of the Jemez lineament and Rio Grande rift) reflect more local CO₂-discharge (tectonic) controls. These travertine occurrences are important indicators of the extent of past natural CO₂ leakage that can inform carbon sequestration models both in areas of modern CO₂ gas fields (Springerville) and at sites of potential paleo-gas fields. The travertine platforms now occupy positions high in the landscape (inverted topography) and also provide data on the scales and timing of regional landscape denudation.