Figure F20. Alkalinity, Ti/Zr, Zr, and Ba abundance vs. depth. Alkalinity is a measure of the deviation of the sample from the alkalic-tholeiitic dividing line in Figure F18; tholeiitic lavas have negative values. From ~40 to 250 mbsf, alkalinity decreases, the abundance of Zr and Ba decreases, and Ti/Zr increases, with the tholeiitic basalt in Subunits 18b and 19b defining the extreme values. Below Subunit 19b all flow units are composed of alkali basalt.