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Sources of Ground Water Salinity on Islands Using 18 O, 2 H, and 34 S
Author(s) -
Allen D.M.
Publication year - 2004
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.2004.tb02447.x
Subject(s) - meteoric water , salinity , seawater , geology , stable isotope ratio , oceanography , groundwater , groundwater recharge , hydrology (agriculture) , aquifer , physics , geotechnical engineering , quantum mechanics
Stable isotopes of 18 O and 2 H in water, and 34 S and l8 O in dissolved SO 4 are used to verify the interpretation of the chemical evolution and proposed sources of salinity for two islands that have undergone postglacial rebound. Results for δ 18 O and δ 34 S in dissolved SO 4 on the Gulf Islands, southwest British Columbia, Canada, suggest a three‐component mixing between (1) atmospheric SO 4 derived largely from recharge of meteoric origin, (2) modern marine SO 4 associated with either modern‐day salt water intrusion or Pleistocene age sea water, and (3) terrestrial SO 4 . The age of the marine SO 4 is uncertain based on the geochemistry and SO 4 isotopes alone. Two options for mixing of saline ground waters are proposed—either between current‐day marine SO 4 and atmospheric SO 4 , or between older (Pleistocene age) marine SO 4 and atmospheric SO 4 . δ 18 O and δ 2 H compositions are relatively consistent between both islands, with a few samples showing evidence of mixing with water that is a hybrid mixture of Fraser River water and ocean water. The isotopic composition of this hybrid water is ∼δ 18 O = 10 %c . δ 18 O and δ 2 H values for many saline ground waters plot close to the global meteoric water line, which is distinctly different from the local meteoric water line. This suggests a meteoric origin for ground waters that is different from the current isotopic composition of meteoric waters. It is proposed these waters may be late Pleistocene in age and were recharged when the island was submerged below sea level and prior to rebound at the end of the last glaciation.