Chemical correlation of volcanic ash deposits in the Salt Lake Group, Utah, Idaho and Nevada Available to Purchase

Widely scattered outcrops of the Salt Lake Group, a sequence of mid to late Tertiary non-marine sediments in the Bonneville Basin, have been correlated on the basis of trace element variation in glass from volcanic ashes. A series of statistical procedures demonstrate that the majority of the ashes can be placed into one of six groups which are chemically distinct. Several ash units occur which bear no chemical affinity to any other ash. A composite stratigraphy of the volcanic ash sequence of the Salt Lake Group has been constructed based upon the sequence of chemical groups of ashes and the chemical correlation of individual ashes common to several distant exposures.