2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 28-33
Presentation Time: 9:00 AM-5:30 PM


ZHANG, Chunfu, Dept. of Geosciences, Fort Hays State University, 600 Park St., Hays, KS 67601, c_zhang35@fhsu.edu

Seventy water samples, collected along the routes through Colorado and Utah, USA in 2014 and 2015, have been analyzed for stable H and O isotopes. Linear regressions of the data acquired, relating elevation to such variables as δD, δ18O, latitude, or longitude, revealed some interesting and perhaps unsettling results: (1) the relationships between elevation and δD or δ18O were weak or nonexistent, with r2 less than 0.1; comparatively, there are better relationships between elevation and latitude or longitude, with r2 about 0.2; (2) there are very little (if any) relationships between δD and latitude or longitude, perhaps due to the much larger error in δD analyses than in δ18O analyses; and (3) compared to the very weak or nonexistent relationship between δ18O and latitude, the relationship between δ18O and longitude is much better (with r2 = ~0.12), perhaps because longitude is related more to the moisture source distance than latitude is in the study area. The weak or nonexistent relationships between elevation and δD or δ18O place serious doubts on (paleo)altimetry in the central Rockies through Colorado and Utah, perhaps because of the many factors that could affect the δD and δ18O values, including but are not limited to the distance to moisture source, evaporation, temperature, humidity, and raining amounts, etc. That is, (paleo)altimetry may not be applicable in the study area.

Other interesting observations include: (1) flowing water is generally more enriched than snow or ice in the same area due to melting and evaporation enrichment; (2) water puddles next to each other in the desert or the same puddle some time later may have very different δD and δ18O values, with the smaller puddle being more enriched and more easily affected due to higher percentages of evaporation; (3) standing water usually has more enriched values than running water; (4) wetter year (e.g., 2015) generally yields more depleted δD and δ18O values than drier years (e.g., 2014); and (5) lower reaches of a river may have higher δD and δ18O values than the upper reaches, perhaps due to evaporation.