Fine-grained excavation and analysis of a stratigraphic column from Danger Cave, northeastern Great Basin, suggests prehistoric hunter-gatherers were collecting and using singleleaf pinyon (Pinus monophylla) near the site for at least the last 7500 yr. Human use of the cave began after the retreat of Lake Bonneville from the Gilbert level, shortly before 10,000 yr B.P. In stratum 9, culturally deposited pine nut hulls appear in the sequence by about 7900 yr B.P. and are continuously present thereafter. A hull fragment in stratum 10 is directly dated to 7410 ± 120 yr B.P. These dates are at least 2000 yr earlier than expected by extrapolation to macrofossil records from the east-central and central Great Basin, and necessitate some revision of current biogeographical models of late Quaternary pinyon migration.

The degree of analogy between fossil and contemporary pollen spectra in Europe has been investigated using the chord-distance dissimilarity measure. No-analog pollen spectra represent vegetation without a modern analog and hence, by inference, represent macroclimatic conditions different from any occurring in the region today. Such spectra have minimum chord distances that exceed a threshold value assessed using contemporary samples from the same and different vegetation u units. Contoured maps of minimum chord distance portray the changing patterns of analogous and no-analog pollen spectra, and hence vegetation units, since 13,000 yr B.P. No-analog vegetation units have been extensive in some regions for much of the Holocene, persisting as recently as 1000 years ago in many areas. The chord-distance measure has also been used to explore the patterns, extent, and rates of change in European pollen spectra since 13,000 yr B.P. Pollen spectra changed rapidly during late-glacial and early Holocene times and during the last millennium. Paleoclimatic changes have brought about the major changes in the Holocene paleovegetation of Europe. Human impact upon European vegetation has obscured neither the contemporary relationship between pollen spectra and vegetation nor the climatically determined long-term changes of vegetation across the continent since 13,000 yr B.P.

A fossil pecan, Carya illinoensis (Wang.) K. Koch, from floodplain sediments of the Mississippi River near Muscatine, Iowa, was accelerator-dated at 7280 ± 120 yr B.P. This discovery indicates that pecan was at or near its present northern limit by that time. Carya pollen profiles from the Mississippi River Trench indicate that hickory pollen percentages were much higher in the valley than at upland locations during the early Holocene. Pecan, the hickory with the most restricted riparian habitat, is the likely candidate for producing these peaks in Carya pollen percentages. Therefore, pecan may have reached its northern limit as early as 10,300 yr B.P. Its abundance in Early Archaic archaeological sites and the co-occurrence of early Holocene Carya pollen peaks with the arrival of the Dalton artifact complex in the Upper Mississippi Valley suggest that humans may have played a role in the early dispersal of pecan.

Dates of basal fen peat at 52 locations across west-central Canada indicate that peat deposition began <6000 yr B.P. in a broad zone north of the present-day grassland. The isopleth of >6000 yr B.P. basal fen peat parallels the foothills of the Rocky Mountains, and extends eastward along 54°30′ north latitude. The absence of >6000 yr B.P. peat within this zone is attributed to a warmdry early to middle Holocene climate that caused severe seasonal droughts and prevented the establishment of peat-forming fen vegetation. Wetlands west (and probably north) of this line experienced lower water tables, but supported fen vegetation. As the climate became cooler and moister, stable water tables allowed the development of fens and rapid peat accumulation ensued, reaching the modern distribution of fens between 2000 and 3500 yr B.P. Projections of climatic parameters indicate that the mean annual growing degree days were 6 to 21% higher during the early and middle Holocene, and that precipitation was reduced through most of the area, resulting in much higher (by 17 to 29%) aridity than at present.

Mean long-term rates of peat accumulation are higher in boreal and temperate peat deposits than in subarctic regions of Canada, although peatlands are extensive in the subarctic. Climatic change probably accounts for the development of southern peatlands during the middle to late Holocene and for the late Holocene decline in growth of many subarctic peat deposits. In northwestern peat deposits, peat of wet Sphagnum lawns and treed wetlands tended to accumulate more rapidly than peat of Sphagnum hummocks and sedge fens. Long-term net rates of carbon accumulation in Canadian peatlands typically range from 10 to 35 g C/m2/yr.

Magnetostratigraphic studies of Pliocene-Pleistocene continental deposits on the Plateau de Perrier and in the Le Puy-en-Velay basin (Massif Central), as well as in the Riez-Valensole basin (Alpes de Haute Provence, Mediterranean South), provide decisive reference dating of several well-known fossil-bearing Villafranchian sites. These are well distributed in the tephrostratigraphy on both sides of the Gauss/Matuyama geomagnetic boundary: the Roca-Neyra fauna falls within the Matuyama chron, while older sediments at Les Etouaires are situated just above the normal-reversed transition. The Vialette section lies below this reversal, within the Gauss chron. In the Riez-Valensole basin, the discovery of the Gauss/Matuyama boundary toward the top of the Puimoisson section leads to an excellent correlation with the Massif Central localities. Rodents of the Seynes zone occur below the reversal, while Equus appears just above. This calibration improves the Mediterranean upper Neogene biochronology and allows a direct correlation with Villafranchian vertebrate sites of the Massif Central.

The first pollen and phytolith data covering the entire Pleistocene/Holocene transition from the lowlands of the Central American isthmus indicate that the forests of late-glacial Panama at an altitude of 650 m resembled those currently found at ca. 1500–1800 m. A temperature depression of ca. 5°C and reduced precipitation/evaporation ratios in the late-glacial period are suggested. Forest composition from ca. 14,000 to 10,500 yr B.P., although primarily montane in character, contained a low biomass of species today segregated in lowland forests and, hence, a floral assemblage with no modern analog. The sudden appearance of carbon and burnt, weedy plant material at ca. 11,000 yr B.P. is attributed to the earliest human impact yet recorded from tropical America and may perhaps have been associated with the first human occupation of the region.

Organic material exposed within a small swale fill in Pit 6 of the Wedron Silica Sand Co. near Wedron in LaSalle County, Illinois, includes well-preserved pollen, plant macrofossils, and insect remains. This material occurs in slackwater sediment in the lower part of the Peddicord Formation, which was deposited as existing valleys were dammed by fluvial aggradation during the initial late Wisconsinan advance of Laurentide ice into the Wedron area. Wood from the organic horizon has a radiocarbon age of 21,460 ± 470 yr B.P. (ISGS-1486). The pollen spectrum is dominated by Picea, Pinus, and Cyperaceae. Plant macrofossils comprise a mix of boreal-forest taxa, including Picea, Larix laricina, and the moss Campylium stellatum; subarctic species including Betula glandulosa, Empetrum nigrum, and Selaginella selaginoides; along with the predominantly arctic Vaccinium uliginosum var. alpinum, Dryas integrifolia, and Rhododendron lapponicum. The insect fauna contains the western montane ground beetle Opisthius richardsoni; several arctic-subarctic ground beetles including Diacheila polita, Helophorus sibiricus, and Pterostichus (Cryobius) caribou; and a diverse assemblage of insects that today inhabit the boreal forest. We interpret the biotic record to record a phase in the transition from closed boreal forest to open tundra as climatic conditions deteriorated in advance of continental glaciation.

From New Jersey to southwestern New York, Altonian colluvium and fluvial gravel have been recognized beneath Woodfordian drift, but the existence of Altonian till near or beyond the Woodfordian border has not been demonstrated. Reworking of weathered materials by Woodfordian ice has produced some drift with an “Altonian” appearance. Soil criteria, applied without regard for parent material differences, have been incorrectly used to infer an Altonian age for Illinoian deposits that have a redbed provenance. The currently mapped distribution of Altonian till and the occurrence of undisturbed Illinoian deposits within areas of inferred Altonian ice cover are incompatible with the behavior of ice sheets.

Oxygen isotope determinations on the α-cellulose of tree rings cut from two leaning Picea engelmannii revealed significant differences between results from normal and compression wood radii. Nine samples (10-year periods) from the normal wood radius (1721–1953) in one tree showed good agreement with proxy climate information and maximum differences of 1.8‰ between the “warmest” and “coolest” decades sampled. Differences of equivalent magnitude were found between samples from the same decade from normal and compression wood radii. These differences are strongly related to the amount and/or density of compression wood present and suggest that sampling for paleoclimatic work should be restricted to complacent, erect trees without compression wood rings.

Fossil insects from the late-glacial deposits at the Lamb Spring archaeological site, near Denver, Colorado, are relatively abundant and diverse, providing considerable paleoecological data for the site. The late Pleistocene insect fauna from the site comprises 72 identified taxa, principally beetles. However, the fauna presented an interpretive problem because it contained a mixture of prairie and alpine tundra species. This was initially considered to be the result of a mixing of faunal elements during the climatic transition of late-glacial times, a “no-modern-analog” fauna. Accelerator dating of insect fossil specimens from the two ecological groups helped resolve the paleoecological problem. Fossil specimens of the prairie-associated species were dated at 17,850 ± 550 yr B.P., while specimens of the tundra-associated species yielded an age of 14,500 ± 500 yr B.P. These dates reveal that what appeared to be an ecological mixing was probably a taphonomic problem, wherein full-glacial-age fossils were probably reworked into latest Wisconsin sediments. While both faunal assemblages reflect climatic conditions substantially colder than present, initial results suggest that the full-glacial fauna represents a cold, dry grassland or steppe environment, while the younger fauna suggests moister and more tundra-like conditions.

Pollen analysis of a 14,000-yr-old sediment core from Sithylemenkat Lake provides the first Holocene vegetational history for the Kanuti Flats of north-central Alaska. Basal samples contain a curious and unusual combination of tundra and boreal taxa. Pollen assemblages dating from 13,500 to 9000 yr B.P. are more typical of southern Brooks Range sites and indicate the presence of Betula shrub tundra with increased Populus ca. 10,000 to 9000 yr B.P. Picea glauca appeared ca. 9000 yr B.P. and Alnus ca. 8000 yr B.P. P. glauca populations declined between 7800 and 5000 yr B.P. with a subsequent reforestation by P. mariana and P. glauca. This pattern is seen at other sites in northeastern Alaska and suggests that the Holocene history of boreal forest is more complex than thought previously.