Geochemical and Petrographic Analyses of Travertine-Precipitating Waters and Travertine Deposits, Arbuckle Mountains, Oklahoma

Nancy M. Utech, Henry S. Chafetz

Waters in Honey and Falls Creeks, Arbuckle Mountains region of Oklahoma, are supersaturated in CO₂ with respect to the overlying atmosphere and are up to 10 times saturated with respect to calcite (I_sat = 10). Loss of CO₂ from the system results in a downstream increase in saturation levels, with the highest I_sat at sites of maximum travertine deposition. High supersaturation is the result of natural kinetic processes (rapid CO₂ outgassing vs. slow precipitation) rather than the effects of foreign ion inhibitors. Temporal variations in the composition of the waters indicate that, contrary to expectations, prolonged periods of heavy rainfall cause a significant increase in I_sat levels. At any sample site, no consistent chemical variation occurred between organically mediated and inorganic precipitates. However, all deposits show a significant increase in magnesium concentration in a downstream direction; this may be a result of higher I_sat values and corresponding higher rates of precipitation.

Carbon isotopes for creek waters are highly variable, from -0.6 to -12.2^pmil, reflecting a variety of sinks and sources for C¹². Oxygen isotopes are relatively constant, from -3.7 to -6.0^pmil, average = -5.2^pmil, indicating an open-water system. Based on calculations from water data, travertine should exhibit a 2^pmil difference in ^dgr¹⁸O values for precipitates formed in the summer vs. those formed in the winter. Algally laminated crusts, which have been postulated to be of seasonal origin, exhibit variation in ^dgr¹⁸O values between laminae, confirming the seasonal origin of the laminae.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.