Clay mineralogy of the Onodaga limestone, central and western New York State.

Each of the four members of the Onondaga limestone were sampled vertically at four widely separated localities from W to E New York. They were analysed chemically and for clay minerals, after treatment to remove carbonate minerals. Dioctahedral illite and trioctahedral smectite were most abundant in the insoluble residues. Glauconite is abundant in the basal member, but rare above it. Mixed layer illite/smectite and expansible chlorite are also present. Silt- size detrital quartz and chert also occur, with the chert very abundant locally. Silicon ranges 53.22-76.79%, Al 10.91-26.19, K 3.85-8.47, Fe 3.14-8.52 and Mg 1.14-4.11. Other elements present include Ca, Na, Mn, Ti and P. The only notable vertical variation is the decrease in chlorite in some locations. No lateral variations were found.-M.I.D.