New Mexico Geological Society Annual Spring Meeting — Abstracts

New Mexico and Arizona host several large travertine deposits (>20-60 km² with thicknesses ranging from 15 to more than 60 m) that provide a record of significant natural fluxes of CO₂. Studies of these geologic natural CO₂ leakages are important for carbon sequestration studies. Active CO₂ springs provide modern analogs for water/gas compositions and fluxes while ancient travertine deposits offer a unique tool to better understand past CO₂ fluxes in the context of paleohydrology, paleoclimate, and tectonics. Volume estimates based on stratigraphic studies, drilling and GIS are used to calculate the flux of CO₂ that lead to the formation of large volume travertine deposits. Precise new U/Th dating and stable isotope analysis are underway for large travertine platforms at Mesa del Oro, NM (>20 km² ), Riley, NM (North and South Mesas, >60km² ), Mesa Aparejo (Belen Quarries), NM (>20 km² ), and Springerville, AZ (>30 km² ). At Mesa del Oro, NM, new ages for the travertine deposits are 56 ka, 253 ka, 361 ka and more than 500 ka. U/Th dates from Springerville, AZ, show that major travertine accumulations also occurred over several time intervals: 36-100 ka, 200-280 ka and 300-350 ka. At Mesa Aparejo, uppermost travertines are 350 ka, most of the occurrence is >500 ka. Stable isotope analyses from Mesa del Oro and Riley, NM, and Springerville, AZ, overlap substantially - they exhibit high δ¹³C values, +2.0‰ to +8.3‰, and δ¹⁸O values ranging from -13.5‰ to -4‰. U/Th and stable isotope data done to date, combined with field settings show that travertine deposition at all of the these localities (Mesa del Oro, Riley, Mesa Aparejo and Springerville) overlapped temporally and indicate CO₂ leakage over much of the Quaternary. The accumulation of large volumes of travertine was not steady, but rather was episodic, with largest volumes forming 50-120 ka, 200-250 ka and 300-350 ka. Preliminary conclusions are that these intervals coincide with wet times, hence the travertines may provide detailed records of climatic fluctuations. From modern analogs we know that CO₂ gas leakage is probably orders of magnitude larger than CO₂ trapped as travertine (i.e., trapping efficiencies are low). Our goal is to continue to refine flux estimates based on additional mapping/stratigraphy and geochronology.