Comparison of multiple proxy records of Holocene environments in the midwestern United States

We compare four emerging approaches to reconstructing Holocene vegetation a nd climate from south of the glacial border in northeastern Iowa, United St ates. Pollen, plant macrofossils, carbon isotopic (delta(13)C) values from alluvial organic matter, and carbon isotopic values in stalagmites from a n earby cave all show similar paleovegetational and paleoclimatic trends duri ng the Holocene. Pollen and plant macrofossils show a rapid change from for est to prairie about 6000 cal. yr B.P., followed by a return of oaks to a p resumably savanna-like community about 3500 cal, yr B.P. The delta(13)C val ues in alluvial organic matter and the percentage of C-4 plants both increa se ca, 6300 cal, yr B.P., and then decrease in the last 3500 Sears. In the cave, delta(13)C values rise beginning at 6000 cal, yr B.P. to a broad peak ca. 4500 to 3000 cal, Sr B.P., and decrease thereafter. Pollen and plant m acrofossils record the composition of the vegetation that produced the isot opic signals, and verify C-3-C-4 interpretations based on the isotopic reco rds. We demonstrate that these methods are complementary, but that any sing le method will provide an accurate reconstruction of past environments.