STRONTIUM ISOTOPIC GEOCHEMISTRY OF THE DEVILS LAKE DRAINAGE SYSTEM, NORTH-DAKOTA - A PRELIMINARY-STUDY AND POTENTIAL PALEOCLIMATIC IMPLICATIONS

A series of water samples (precipitation, surface water and ground wat er) from the Devils Lake drainage basin in central North Dakota have b een analyzed for their delta(18)O and delta D and Sr-87/Sr-86. The del ta(18)O and delta D of snow and most ground water samples fall near th e meteoric water line, with the ground water being isotopically heavie r than the snow, indicating that a portion of the recharge must come f rom non-winter precipitation events. One ground water and all the surf ace water samples fall below the meteoric water line, demonstrating ex tensive evaporation. The Sr-87/Sr-86 ratio of the snow is more radioge nic than those of the ground water samples, indicating that the ground water has increased its Sr-86 content by the dissolution of mafic roc k in the aquifer. Stump Lake has a much more radiogenic Sr isotopic ra tio than the waters of Devils Lake suggesting a source of water differ ent from that of Devils Lake. The East Stump Lake water, on the other hand, appears to be either a mix of Devils Lake and Stump Lake waters, or Devils Lake water diluted with precipitation.