Two radiocarbon ages provide a stratigraphic framework for some events in the Susquehanna Valley. A 13,320 ± 200 yrs B.P. date on a mastodon pelvic fragment from outwash gravels aids in refining the Valley Heads substage in central New York. A 1,690 ± 100 yrs B.P. date on wood provides an age for the first preserved flood-plain deposits.