James E. King

A Holocene vegetation record from the Mississippi River Valley, southeastern Missouri

Abstract Pollen preserved in a peat deposit from a large swamp, the Old Field in the Mississippi River Valley near Advance, Missouri, records radiocarbon-dated vegetation changes between 9000 and about 3000 years ago. The principal feature of both the percentage and influx pollen diagrams is the replacement of arboreal pollen, primarily Quercus, Fraxinus , and Cephalanthus , with Gramineae and NAP between 8700 and 5000 years BP. This vegetation shift is interpreted as reflecting a decrease in the extent of the Old Field swamp and its associated bottomland forest species along with the expansion of a grass-dominated herb community, as a result of a reduction in available ground water. The desiccation of the swamp during this period indicates a reduction in precipitation within the ground-water source area and a shift to a drier climate in the southern Midwest. The pollen suggests that the lowest water levels and driest climate in southeastern Missouri lasted from 8700 to 6500 years BP, at which time there is a partial reappearance of swamp species. Relatively dry conditions, however, continued until at least 5000 years BP. Although pollen influx data are lacking from the upper part of the profile, the relative pollen frequencies suggest an increase in trees after 5000 BP. The replacement of the arboreal vegetation by grasses and herbs between 8700 and 5000 years BP reflects the period of maximum expansion of the Prairie Peninsula in southeastern Missouri. The Old Field swamp provides the first pollen evidence that the vegetational changes along the southern border of the Prairie Peninsula were chronologically similar to those on the northern and northeastern margins.

Pollen analysis of fossil packrat middens from the Sonoran Desert

Abstract Pollen contained in 22 fossil packrat middens from the Sonoran Desert provides a complementary, but differing, view of the paleoenvironment from that derived by analysis of the associated plant macrofossils. The regional component of the pollen data is in sharp contrast to the locally oriented macrofossils. A total of 84 macrofossil taxa and 47 pollen taxa were identified; only 18 taxa were common to both. The low Index of Similarity, 0.4, indicates that the two sources of fossil information are providing different sets of paleobotanical data. When combined with plant macrofossils and good radiocarbon dating control, the pollen spectra derived from fossil middens are compatable with other paleoenvironmental sequences.

Pollen of the North American quaternary: The top twenty

Abstract Based on sixty Holocene sections, the most important North American pollen types are: Pinus, Picea, Ephedra, Tsuga canadensis‐heterophylla, Pseudotsuga‐Larix, Juniperus‐Taxodium, Cyperaceae, Gramineae, Betula, Carya, Alnus, Ulmus, Chenopodiineae, Li‐quidambar, Acer, Quercus, Nyssa, Fagus, Artemisia, and Ambrosia. The distribution of these taxa is employed to describe six floristic provinces—the Boreal, Lakes, Southeast, Pacific, Plains, and Mountain provinces. These provinces are present during earlier Pleistocene interglacial times, but they are not apparent in glacial‐age pollen assemblages, which are dominated by conifers and herbs.

Geochelone in Illinois and the Illinoian-Sangamonian vegetation of the type region

Abstract An investigation of Illinoian- and Sangamonian-age deposits in the type region for both Pleistocene stages in central Illinois has yielded a palynological record spanning the Illinoian-Sangamonian boundary associated with an interglacial fauna containing Geochelone crassiscutata. The pollen indicates a shift from high Picea and Pinus to deciduous trees, followed by grass and herbaceous taxa, and finally, a return of deciduous trees. This sequence appears to correlate with marine isotopic stages 6 through 5d. Faunal remains are abundant throughout but megafauna are present only in the interglacial section where Geochelone occurs. The presence of Geochelone suggests above-freezing temperatures in central Ilinois throughout the year during at least the portion of the Sangamonian represented.

New evidence on the history of the St. Francis Sunk Lands, northeastern Arkansas

A radiocarbon-dated pollen diagram from Big Lake, a complex of relict braided channels on the Little River and part of the St. Francis Sunk Lands in northeastern Arkansas, indicates that the basal lake sediments are less than 180 yr old. This date approximates the time of the New Madrid earthquake of 1811–1812. The formation of the St. Francis Sunk Lands has been attributed to mid-Holocene alluvial drowning, and effects of the New Madrid earthquake upon the Sunk Lands have recently been considered minimal. However, this new evidence suggests that Big Lake was either altered or formed in recent times, possibly by this seismic event.

Modern pollen in the Grand Canyon, Arizona

Abstract Two surface pollen transects were collected from the Grand Canyon, Arizona. One transect consisted of 22 samples collected at river level through the inner gorge, a river distance of 362 km; the other went from the South Rim to the North Rim across the canyon and comprised 25 samples. Both transects show close agreement between local vegetation and modern pollen rain despite large quantities of arboreal pollen drifting into the canyon from upper elevation and rim communities. Pinus pollen averaged 19.3 percent at river level, all of it drifting in from the canyon rims; Quercus pollen, also drifting in, was 5.7 percent. Juniperus, which does occur occasionally at river level, averaged 17.7 percent. The major vegetation communities have different pollen spectra, comprised mostly of local pollen types. The distribution of several plants, particularly Ephedra torreyana, E. nevadensis and Franseria, is clearly recognized in the pollen counts. Chenopodiaceae‐Amaranthus pollen types vary with the amount...