Based on calibrated radiocarbon ages of terrestrial gastropod shells (Succineidae, Discus, Stenotrema, Webbhelix), the chronology of Peoria Silt (loess) deposition in the Central Lowlands is updated. These taxa provide reliable ages (within ~0.2 ka), based on historical shell dating, shell-organic age comparisons, and stratigraphic consistency. A compilation of 53 new and 36 published Peoria Silt shell ages (calibrated), from 12 localities, date from 30.0 to 17.4 ka. Proximal (fossiliferous) loess from 10 sections had mean loess accumulation rates of 0.6–2.2 mm/yr. Study sites along the upper Mississippi, Illinois, to mid-Mississippi, and Ohio-Wabash Valleys suggest Peoria loess accumulated from ~27 to 15 ka, ~29 to 18 ka, and ~30 to 18 ka, respectively. The cessation age for Peoria Silt, based on surface extrapolations, is ~1–6 ka earlier than some prior Illinois estimates, even assuming slower loess accumulation in the modern solum. Younger loess in northwestern Illinois likely reflects, in part, Superior and Des Moines Lobe glacial-meltwater sediment, and Iowan Erosion Surface inputs to the upper Mississippi Valley, after the Lake Michigan Lobe receded. Furthermore, stronger winds, drier conditions, and reduced vegetation cover in valley deflation areas may have favored higher accumulation rates and later loess deposition in northwestern relative to southeastern areas.

Weathering has etched and deeply-denticulated the constituent orthopyroxenes, and chlorite has been transformed to vermiculite in the upper 3 m of an aeolian, periglacial sand dune formed in northeastern Indiana about 13,000 b.p. Pyroxene weathering begins with the development of cleavage-parallel etch pits on {010} and {100} surfaces. These pits coalesce and eventually crop out on basal surfaces as denticulations. The mean denticulation size increases logarithmically toward the surface, and the denticulation size of the orthopyroxenes is a quantifiable feature of the weathering process. Ferruginous pendants, microboxworks of iron oxides, and other indications of iron redeposition within the ortho-pyroxene microenvironments were not observed.

Chlorite in the dune has been weathered to vermiculite. The parent chlorite is a high-Fe variety, and the transformation to vermiculate does not involve the development of a chlorite/vermiculite intermediary phase. Fe2+ is oxidized as part of the transformation process and this iron is retained in the sediment as discrete goethite and as crystalline and noncrystalline coatings on the dune grains. The vermiculite from depths shallower than 64 cm is only partly expandable and is completely collapsed by K-saturation or heat treatment. This is a hydroxy-Al vermiculite and its formation is typical of intense weathering under the acid conditions prevalent at the dune surface.

Callery pear (Pyrus calleryana Decne.) was introduced to North America as an ornamental tree in the early 1900s. Due to widespread planting, P. calleryana has become common throughout the eastern United States and has invaded natural areas, especially disturbed areas. Prescribed fire is a common management technique in prairie ecosystems to mimic natural disturbances. We tested the effectiveness of prescribed fire as a control technique for P. calleryana in a managed prairie system. Fire top-killed all established P. calleryana individuals. However, these individuals responded to fire with 3 to 4 epicormic sprouts each. Similar sprouting behavior occurred in 2-yr-old seedlings. Exposed seeds, fruits, and 1-yr-old seedlings were killed by fire. Established P. calleryana were single-stemmed individuals before exposure to fire. After the prescribed fire, they all were multistemmed, which increased the potential flower-bearing stems within the prairie. We conclude that fire alone is not a suitable technique for managing P. calleryana invasion. Cut and herbicide application methods are labor-intensive. However, combining cut and spray methods with prescribed fire may be effective. Fire removes standing grass and forb biomass, leaving exposed P. calleryana stems, which would make locating individuals and directly applying herbicides easier.

The end of the Pleistocene in North America was marked by a wave of extinctions of large mammals, with the last known appearances of many species falling between ca. 11,000–10,000 14C yr BP. Temporally, this period overlaps with the Clovis Paleoindian cultural complex (11,190–10,530 14C yr BP) and with sudden climatic changes that define the beginning of the Younger Dryas chronozone (ca. 11,000–10,000 14C yr BP), both of which have been considered as potential proximal causes of this extinction event. Radiocarbon dating of enamel and filtered bone collagen from an extinct American Mastodon (Mammut americanum) from northern Indiana, USA, by accelerator mass spectrometer yielded direct dates of 10,055 ± 40 14C yr BP and 10,032 ± 40 14C yr BP, indicating that the animal survived beyond the Clovis time period and into the late Younger Dryas. Although the late survival of this species in mid-continental North America does not remove either humans or climatic change as contributing causes for the late Pleistocene extinctions, neither Clovis hunters nor the climatic perturbations initiating the Younger Dryas chronozone were immediately responsible for driving mastodons to extinction.

Many paleoclimate and landscape change studies in the American Midwest have focused on the Late Glacial and early Holocene time periods (~ 16–11 ka), but little work has addressed landscape change in this area between the Last Glacial Maximum and the Late Glacial (~ 22–16 ka). Sediment cores were collected from 29 new lake and bog sites in Ohio and Indiana to address this gap. The basal radiocarbon dates from these cores show that initial ice retreat from the maximal last-glacial ice extent occurred by 22 ka, and numerous sites that are ~ 100 km inside this limit were exposed by 18.9 ka. Post-glacial environmental changes were identified as stratigraphic or biologic changes in select cores. The strongest signal occurs between 18.5 and 14.6 ka. These Midwestern events correspond with evidence to the northeast, suggesting that initial deglaciation of the ice sheet, and ensuing environmental changes, were episodic and rapid. Significantly, these changes predate the onset of the Bølling postglacial warming (14.8 ka) as recorded by the Greenland ice cores. Thus, deglaciation and landscape change around the southern margins of the Laurentide Ice Sheet happened ~ 7 ka before postglacial changes were felt in central Greenland.