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Strontium Isotopes and Major Elements As Tracers of Ground Water Evolution: Example from the Upper Castle Hayne Aquifer of North Carolina
Author(s) -
Woods Terri L.,
Fullagar Paul D.,
Spruill Richard K.,
Sutton Lynn C.
Publication year - 2000
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.1745-6584.2000.tb02712.x
Subject(s) - aquifer , geology , strontium , groundwater , groundwater recharge , isotopes of strontium , geochemistry , sedimentary rock , artesian aquifer , coastal plain , hydrology (agriculture) , paleontology , chemistry , geotechnical engineering , organic chemistry
The Eocene‐Oligocene Upper Castle Hayne Aquifer (UCH), a well‐indurated limestone with a very high percentage of secondary moldic porosity, is one of the most productive and extensively developed aquifers in the North Carolina Coastal Plain. Ground water from western wells in the UCH is Ca‐ and HCO 3 ‐rich and ground water from easternmost wells is alkali‐ and Cl‐rich. In general, from west to east across the study area, Sr concentrations [Sr] and isotopic ratios of ground water from the UCH and other aquifers evolve toward those of the host aquifer. At the same well site, water from older aquifers usually has a lower 87 Sr/ 86 Sr ratio than water from younger aquifers, due to interaction between ground water and sedimentary material in the host aquifers. Comparison of 87 Sr/ 86 Sr ratios and [Sr] suggests that most UCH water represents mixing of strontium‐poor recharge water from the Surficial Aquifer with varying amounts of strontium from the aquifer rock. For samples that deviate from the calculated mixing line, strontium ratios can often be used to indicate the source of strontium that did not come from UCH rock. Surface waters are characterized by high 87 Sr/ 86 Sr ratios and variable [Sr] that depend on the proportion of intermixed sea water. Water from the overlying Yorktown and Pungo River aquifers can be recognized by higher 87 Sr/ 86 Sr ratios than those of the UCH and water from the underlying LCH, Beaufort, and Peedee aquifers can be recognized by lower 87 Sr/ 86 Sr ratios and higher [Sr].