2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 5
Presentation Time: 9:20 AM


DEMICCO, Robert V., Department of Geological Sciences, State Univ of New York, Binghamton, NY 13902, LOWENSTEIN, Tim K., Geological Sciences and Environmental Studies, Binghamton University, PO Box 6000, Binghamton, NY 13902, HARDIE, Lawrence A., Morton K. Blaustein Department of Earth & Planetary Sciences, Johns Hopkins Univ, Baltimore, MD 21218 and SPENCER, Ron, Geology and Geophysics, Univ of Calgary, 2500 University Drive N.W, Calgary, AB T2N 1N4, Canada, demicco@binghamton.edu

Here we present an inverse model of Phanerozoic seawater composition calibrated against updated paleoseawater compositions from fluid inclusions in marine halites. The model considers step-wise alteration of seawater composition via: (1) variable input of river water; (2) variable rates of alteration of seawater through reactions at mid-ocean ridges; and (3) variable rates of alteration of seawater through reactions on ridge flanks and across the ocean floor in general. The model achieves agreement with paleoseawater fluid inclusion data for Na+, Ca2+, SO42–, and K+, particularly when variable runoff is considered. Variable rates of basalt-seawater interactions at both ridge and ridge flanks are apparently required to understand the evolution of seawater. The results for K+ show that ridge flank alteration is apparently enough to buffer the oceans to the observed, near-constant concentration of K+ through time.