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

Abstract

Waters in Honey and Falls Creeks, Arbuckel Mountains region of Oklahoma, are supersaturated in CO/sub 2/ with respect to the overlying atmosphere and are up to 10 times saturated with respect to calcite (I/sub sat/ = 10). Loss of CO/sub 2/ from the system results in a downstream increase in saturation levels, with the highest I/sub sat/ at sites of maximum travertine deposition. High supersaturation is the result of natural kinetic processes (rapid CO/sub 2/ 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/sub 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 down-stream direction; this may be a result of higher I/sub sat/ values and corresponding higher rates of precipitation. Carbon isotopes for creek waters are highly variable, from /minus/0.6 to /minus/12.2 /per thousand/, reflecting a variety of sinks and sources for C/sup 12/. Oxygen isotopes are relatively constant, from /minus/3.7 to /minus/6.0 /per thousand/, average = /minus/5.2 /per thousand/, indicating anmore » open-water system. Based on calculations from water data, travertine should exhibit a 2 /per thousand/ difference in /delta//sup 18/O 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 /delta//sup 18/O values between laminae, confirming the seasonal origin of the laminae.« less