Radiocarbon and cation-ratio ages for rock varnish on Tioga and Tahoe morainal boulders of Pine Creek, eastern Sierra Nevada, California, and their paleoclimatic implications

At Pine Creek, varnish started to form on boulders of the outermost Tioga moraine before 19 000 yr BP, and varnish originated on the innermost Tioga moraine before 13 200 yr BP. Comparisons with lake-level, paleohydrological, paleoecological, colluvial, and rock varnish micromorphological data indicate that central-eastern California and western Nevada experiences a moisture-effective period during the late Pleistocene but after the Tioga maximum. Tahoe-age morainal boulder at Pine Creek have varnish cation-ratio ages of about 143 000-156 000 yr BP, suggesting that the Tahoe glaciation shuold not be correlated with oxygen-isotope stage 4 in the early Wisconsin, but rather with stage 6. -from Authors