MODEL OF SEAWATER COMPOSITION FOR THE PHANEROZOIC

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.