Chlorine-36 tracing of salinity sources in the Dry Valleys of Victoria Land, Antarctica

Abstract

Chlorine-36 was used to trace the origins of salts in six saline lakes in the Dry Valleys of Southern Victoria Land, Antarctica. Characteristic 36Cl signatures were estimated for the various potential chloride sources, which include atmospheric deposition, rock weathering, seawater, and deep ground water. 36Cl Cl ratios were measured in natural waters and salts from the Dry Valleys. Dilute lake waters (Cl − < 100 mg/l) were found to have 36Cl Cl ratios in the range 100 × 10 −15 to 1,700 × 10 −15, whereas saline waters (Cl − > 1000 mg/l) had ratios in the range 9 × 10 −15 to 40 × 10 −15. Simple mixing models were employed to quantify the relative contributions of the various chloride sources to Lake Vanda and Don Juan Pond. These results show that Lake Vanda has received its chloride from both deep ground water and the Onyx River. Don Juan Pond has received nearly all its chloride from deep ground water, probably ultimately from rock-water interaction. Deep ground water is the principal source of chloride to the lakes of Wright Valley. However, preliminary data suggest that marine-derived salts or relict sea water may be a significant source of chloride to the lakes of Taylor Valley, implying a possible recent marine invasion that did not affect Wright Valley.