Note 11 — THE CLAYS OF BUTTON BAY STATE PARK
Reading edition
The blue color is due to the presence of ferrous iron (bivalent iron) together with iron compounds in which iron has its higher chemical valence (ferric iron). This ferrous iron demands a chemically reducing environment for its formation and indicates that the clays were deposited in a shallow sea or that they remained for some time beneath a stable water-table. They contained a fair quantity of decaying organic material.