Shane, Linda C. K. 1987 03 01: Late-glacial vegetational and climatic history of the Allegheny Plateau and the Till Plains of Ohio and Indiana, U.S.A. Boreas, Vol. 16, pp. 1–20. Oslo. ISSN 0300–9483.
Pollen evidence from the Allegheny Plateau and the Till Plains south of the Great Lakes shows marked post-glacial vegetation gradients. C. 15,500–11,000 B.P.: On the Plateau, spruce forest was rapidly established, persisted for 2,000 years, then began a gradual change to deciduous-conifer forest. On the Till Plains, open spruce forest tundra closed slowly over 1,000 years, declined rapidly c. 13,500 B.P., and a deciduous open woodland developed. C. 11,000–10,300 B.P.: On the Till Plains, a brief cooling is recorded by increases in the abundance of spruce and fir, contemporaneous with the European Younger Dryas. No clear change is seen on the Plateau. 10,300–4,000 B.P.: Warming and/or drying occurred in both areas, as hemlock and jack/red pine trees immigrated, followed by white pine. Conifers disappeared from the Till Plains by 9,800 B.P., but pine and hemlock trees may have persisted on the Plateau. After 10,000 B.P. mixed deciduous forest was established across the entire region. Between 8,000 and 4,000 B.P., further warming/drying is indicated on the Till Plains with development of open oak forest and lake shallowing, and on the Plateau by a minor increase in herbs, lake shallowing, and reduction in pine.