Geochronology and Stable Isotope Geochemistry of Quaternary Travertine Deposits on the Colorado Plateau, USA, and Implications for CO2 Sequestration

Alexandra Priewisch, Laura Crossey, and Karl Karlstrom
University of New Mexico, Department of Earth and Planetary Sciences
Albuquerque, New Mexico, United States of America
[email protected]

Large-volume travertine deposits of New Mexico and Arizona are important indicators of the extent of ancient CO2 reservoirs and past natural CO2 leakage. Travertines are natural analogues for CO2 leakage over geologic time scales and the behavior of these natural systems can be extended by analogy to understand the potential patterns of leakage in engineered systems, e.g. storage sites where CO2 is injected into the subsurface. Analysis of the geochemical and isotopic composition of U-series dated travertine deposits allows evaluation of the flow paths of CO2-charged waters and determination of the CO2 flux in order to estimate how much CO2 escaped to the surface while the travertine system was active. Travertine deposition in New Mexico and Arizona occurred episodically at 700-500 ka, 350-200 ka, and 100-40 ka and these episodes of high accumulation rates are interpreted as times of high groundwater flow and hence as a proxy for regional paleohydrology and paleoclimate controls. Stable isotope analyses of travertine deposits in New Mexico and Arizona overlap substantially between deposits and cluster around -10‰ to -6‰ for δ¹⁸O and around 3.5‰ to 6.5‰ for δ¹³C. Stable isotope and trace element geochemistry of the travertines reflects paleohydrologic conditions at the time when the deposits where formed and allows for determining discharge rates, water temperatures and groundwater sources of travertine-depositing springs. Initial results from New Mexico and Arizona travertine deposits overlap in concentrations of elements such as Al, As, B, Ba, K, and Si, but show characteristic rare earth element (REE) signatures for individual travertine deposits.

AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects