Late glacial aster prairie at the Aubrey Clovis site, North Texas, USA.

Pollen analysis of pond and spring deposits at the Aubrey Clovis site in North Texas provides a 1300-year record of late glacial grassland vegetation from 17,200 to 15,900 cal years BP. Forty-six pollen taxa are identified in the well-preserved assemblages. The late glacial pollen record at the Aubrey site represents three environments: upland, riparian, and lacustrine-wetland. The pond-related sediments are dominated by 80% Poaceae pollen, an unusually high amount in pollen records; the spring tufa sediments are dominated by Cyperaceae. Cattail (Typha latifolia) and other wetland plants, including green algae Botryococcus, Pediastrum , and Chara were present. The riparian habitat of the wide late glacial alluvial valley had alder (Alnus), willow (Salix), cottonwood (Populus), and water elm (Planera aquatica). The upland vegetation was a treeless grassland with comparatively high amounts of Asteraceae-type pollen; it is therefore called the aster prairie. Quercus, Juniperus , Carya , Ulmus , Ambrosia , and Chenopodiaceae pollen are much less abundant than found in modern grassland pollen records. Small amounts of Artemisia , Pinus , and Picea pollen are present, a consequence of long-distance transport. Regional late glacial cool-wet climate produced moist prairie soils. The Cross Timbers oak forest that occurs near the site today had not yet formed. Dissimilarity analysis of the pollen data shows that the late glacial aster prairie has no analog with modern shortgrass, mixed-grass, or tallgrass prairies. In contrast, a favorable analog exists with fossil pollen data from a lower zone at Patschke Bog, central Texas, and Muscotah Marsh, northeastern Kansas, indicating that a grassland characterized by high amounts of Asteraceae pollen formed a unique late glacial vegetation type in the region, earlier in Texas and later in Kansas. Because of its chronology and location in the eastern Great Plains, the late glacial aster prairie may be ancestral to the modern tallgrass prairie. • The late glacial aster prairie has no analog with modern tallgrass, mixed-grass, or short grass prairies. • The treeless condition of the aster prairie is supported by the absence of bark beetles and other tree-dwelling insects. • The late glacial climate was cooler than today, based on associated insects and mollusks. [ABSTRACT FROM AUTHOR]