The stratigraphy and sedimentology of the Q3 middle terrace alluvial sequence in the lower Tagus river valley, Portugal, were studied near the village of Alpiarça, approximately 40 km upstream from the estuarine area. Two main stratigraphic units were recognized, separated by an important uncomformity. The Lower Gravels unit (LG) consists of intercalations of medium to coarse gravel deposits, mainly quartzitic, with coarse sandy matrix, organized in tabular bodies. The overlying Upper Sands unit (US) consists of tabular sandy channel deposits and overbank fines, the latter containing well-developed paleosols and backswamp deposits, showing a general aggrading trend, apparently with varying rates; available data indicate that deposition of the US took place under temperate climatic conditions. Within US deposits are several paleolithic archaeological sites, the lower ones in the alluvial stratigraphy being Middle Acheulian, whereas those embedded in overlying deposits are, from bottom to top, Upper Acheulian and Micoquian. Some of these sites have been recently excavated. The quartzite artifacts were apparently abandoned by early humans on the flood plain surface during deposition of the US unit and were subjected to limited reworking during their incorporation in the alluvium. TL/OSL dating of sandy-silty sediments, though imprecise, support archaeological evidence pointing to an age of 150,000 to 70,000 yr B.P. for the US unit.

The abundance and lithic content of ice rafted detritus in glacial North Atlantic sediment cores vary abruptly on millennial time scales that have been correlated to Dansgaard-Oeschger cycles in the Greenland ice cores. There is growing evidence that various ice sheet outlets contributed increased iceberg fluxes at multiple discrete intervals, and the relative timing of iceberg discharges from different sources is important for understanding interactions between oceans and ice sheets. We present a provenance study based on 40Ar/39Ar dates of individual hornblende grains from 20 samples taken at 600 to 700 yr spacing between 10,500 and 22,000 yr B.P., from Orphan Knoll core EW9303-GGC31. Heinrich layers are characterized by a dominant Paleoproterozoic hornblende provenance consistent with published studies. A change in provenance between Heinrich events H2 and H1 indicates contributions of iceberg calving from the Newfoundland and southern Labrador margins. Between H1 and the Younger Dryas interval, Paleoproterozoic ice rafted grains remained dominant. The dominance of Baffin Island (or Greenland?) sources to the ice rafted detritus is ascribed to the retreat of the southern Laurentide ice sheet at about the time of H1—a retreat that isolated Newfoundland and southern Labrador ice from the shelf-slope boundary.

Dinoflagellate cyst and pollen records from marine sediments off the southwestern African coast reveal three major aridification periods since the last glaciation and an environmental correlation between land and sea. Abundant pollen of desert, semi-desert, and temperate plants 21,000–17,500 cal yr B.P. show arid and cold conditions in southwestern Africa that correspond to low sea surface temperatures and enhanced upwelling shown by dinoflagellate cysts. Occurrence of Restionaceae in the pollen record suggests northward movement of the winter-rain regime that influenced the study area during the last glacial maximum. Decline of Asteroideae, Restionaceae, and Ericaceae in the pollen record shows that temperate vegetation migrated out of the study area about 17,500 cal yr B.P., probably because of warming during the last deglaciation. The warming in southwestern Africa was associated with weakened upwelling and increased sea surface temperatures, 2000–2800 years earlier than in the Northern Hemisphere. Aridification 14,300–12,600 cal yr B.P. is characterized by a prominent increase of desert and semi-desert pollen without the return of temperate vegetation. This aridification corresponds to enhanced upwelling off Namibia and cooler temperatures in Antarctica, and it might have been influenced by oceanic thermohaline circulation. Aridification 11,000–8900 cal yr B.P. is out of phase with the northern African climate. Reduction of the water vapor supply in southwestern Africa at that time may be related to northward excursions of the Intertropical Convergence Zone.

Macrofossil analysis of a peat layer overlying shallow-water estuarine sediments allows the reconstruction of vegetation changes between 7000 and 6000 14C yr B.P. near Montmagny, Québec. About 7500–7000 14C yr B.P., the study site was brackish and intertidal. Next, a cattail marsh dominated by Typha changed into a terrestrial fire-prone environment that contained xero-mesophilous tree species (Pinus/Tsuga) and lasted a few hundred years, until about 6800 14C yr B.P. This rapid change may have resulted from land tilting associated with the northward migration of the postglacial forebulge. An abrupt change from a Pinus/Tsuga-dominated cover to shrubby vegetation was due to a fire that affected the site 6800 14C yr B.P. Fossil mosses at the site reflect local wetness likely produced by a rise in the water table starting about 6600 14C yr B.P. By 6500–6400 14C yr B.P., seawater returned and freshwater plants were replaced by semihalophilous and halophilous plants. Thinning of annual rings in fossil larch reflects this change from a terrestrial peatland to a treeless coast.

Sediment cores from Western Lake provide a 7000-yr record of coastal environmental changes and catastrophic hurricane landfalls along the Gulf Coast of the Florida Panhandle. Using Hurricane Opal as a modern analog, we infer that overwash sand layers occurring near the center of the lake were caused by catastrophic hurricanes of category 4 or 5 intensity. Few catastrophic hurricanes struck the Western Lake area during two quiescent periods 3400–5000 and 0–1000 14C yr B.P. The landfall probabilities increased dramatically to ca. 0.5% per yr during an “hyperactive” period from 1000–3400 14C yr B.P., especially in the first millennium A.D. The millennial-scale variability in catastrophic hurricane landfalls along the Gulf Coast is probably controlled by shifts in the position of the jet stream and the Bermuda High.

At a marsh on the hanging wall of the Seattle fault, fossil brackish water diatom and plant seed assemblages show that the marsh lay near sea level between ∼7500 and 1000 cal yr B.P. This marsh is uniquely situated for recording environmental changes associated with past earthquakes on the Seattle fault. Since 7500 cal yr B.P., changes in fossil diatoms and seeds record several rapid environmental changes. In the earliest of these, brackish conditions changed to freshwater ∼6900 cal yr B.P., possibly because of coseismic uplift or beach berm accretion. If coseismic uplift produced the freshening ∼6900 cal yr B.P., that uplift probably did not exceed 2 m. During another event about 1700 cal yr B.P., brackish plant and diatom assemblages changed rapidly to a tidal flat assemblage because of either tectonic subsidence or berm erosion. The site then remained a tideflat until the most recent event, when an abrupt shift from tideflat diatoms to freshwater taxa resulted from ∼7 m of uplift during an earthquake on the Seattle fault ∼1000 cal yr B.P. Regardless of the earlier events, no Seattle fault earthquake similar to the one ∼1000 cal yr B.P. occurred at any other time in the past 7500 years.

A pollen record from Lago Condorito (41°45′S, 73°07′W) shows that North Patagonian Rain Forest taxa predominated between about 13,000 and 12,200 14C yr B.P. in the lowlands of southern Chile, near the city of Puerto Montt. This was followed by the expansion and persistence of the conifer Podocarpus nubigena between 12,200 and 9900 14C yr B.P. Trees favored by disturbance expanded between 11,200 and 9900 14C yr B.P., concurrent with sharp and sustained increases of microscopic charcoal particles. Taxa of low-elevation rain forests expanded and became more diverse in pulses centered at 9900 and 9000 14C yr B.P., following the disappearance of P. nubigena. These data suggest conditions approaching modern climate between about 13,000 and 12,200 14C yr B.P. The climate cooled between 12,200 and 9900 14C yr B.P., then quickly warmed to interglacial conditions. Stand-replacing fires occurred near Lago Condorito between 11,200 and 9900 14C yr B.P., under cool-temperate, humid conditions. The proximity and reported antiquity of the Monte Verde archeological site raise the possibility that these fires were set by human activities.

Records of eolian quartz from two continuous sediment sequences drilled in Lagaccione and Lago di Vico volcanic lakes in central Italy contribute to the knowledge of eolian deposition in the central Mediterranean during the last 100,000 years. The chronology is based on 14C and 40Ar/39Ar dating and tephra analysis. Pollen data provide the paleoenvironmental framework and enable correlation between the cores. Eolian inputs were high during the steppe phases corresponding to oxygen isotope stages 4 and 2. Low inputs correspond to the forest phases of the last interglacial and the middle Holocene. Eolian inputs have increased in the late Holocene. Patterns of eolian deposition in central Italy resemble the Antarctic dust record from the Vostok ice core. The Italian patterns may also correspond with hydrological changes registered in North Africa. The main source of dust loading over the Mediterranean now, North Africa, may have played an important role in dust supply throughout the last climatic cycle.

This paper presents a spatial reconstruction of climate in East Africa at 6000 14C yr B.P. Two different approaches using pollen data have been used, the standard “best modern analogues” method and the new “plant functional type” method, based on groups of pollen taxa. Both methods have been applied to 32 fossil pollen spectra dated at 6000 14C yr B.P. For each site, we have estimated two climatic parameters (annual precipitation and mean annual temperature), three bioclimatic parameters (ratio of actual to potential evapotranspiration, and the mean temperature of the coldest and warmest months). Results show that the temperature lapse rate was less steep at 6000 14C yr B.P. than it is today. The climate was wetter north of 3°S (precipitation anomalies >+50 mm/yr) and slightly drier farther south (precipitation anomalies ≤+50 mm/yr). The ratio of actual to potential evapotranspiration also indicates conditions similar to or wetter than today north of 3°S (anomalies >10%). The climate was warmer than today by 2°C north of the equator and was cooler southward (≤−1°C). Although both methods indicate similar climatic patterns, the plant functional type method provides more consistent results.

Pollen, foraminifer, dinocyst, and coarse lithic high-resolution analyses and δ18O measurements have been carried out for the last-glacial section of marine core MD95-2042 located near the southwestern margin of the Iberian Peninsula. The pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period, suggesting a climatic variability very similar to that of the Dansgaard-Oeschger cycles recorded by the Greenland ice cores. The detailed direct correlation of the terrestrial and marine proxy data from core MD95-2042 indicates a three-phase pattern of Heinrich events in land and ocean environments. The first and last phases of the H5 and H4 events are characterized by a mild and humid climate in southwestern Europe, probably associated with the European origin of the ice-rafted detritus. The middle phase exhibits a cold and dry climate in Iberia linked with the maximum input of ice-rafted detritus. This phase seems to correspond with the Laurentide ice-sheet surges. Between the Heinrich events, several cold and dry periods on land are correlated with stades of the Dansgaard-Oeschger cycles. The impact of the Dansgaard-Oeschger stades in southwestern Europe seems to be preferentially connected to the cold winter air masses reaching this mid-latitude region.

Phytoliths record late Quaternary vegetation at three archaeological sites in the Ituri rain forest. The oldest deposits, dated to ca. 19,000 to 10,000 14C yr B.P., contain abundant phytoliths of grasses but also enough arboreal forms to show that the landscape was forested. The late-glacial forests may have had a more open canopy than today's. Younger phytolith assemblages show that the northeast Congo basin was densely forested throughout the Holocene. Archaeological materials among the phytoliths show that people lived in this region during the Pleistocene. Therefore, Pleistocene and Holocene prehistoric foragers probably inhabited tropical forests of the northeast Congo basin many millennia before farming appeared in the region.

Stratigraphically precise AMS-radiocarbon-dated plant remains, pollen, charcoal, and microtephra analyses from the Faroe Islands were used to establish the timing and effects of the first human settlement. The first occurrence of cultivated crops from three locations dated from as early as the sixth century A.D. and was older than implied from previous archaeological and historical studies, but consistent with earlier palaeoecological investigations. The effects of settlement on the vegetation were rapid and widespread. The transformation of the flora of this fragile ecosystem was best expressed by the large assemblage of ruderal, postsettlement plants recorded as macrofossils. The earliest known introduction of domestic animals (sheep/goat) was ca. A.D. 700. Their arrival on these relatively small islands probably contributed to the widespread change in vegetation and the loss of restricted native woody cover. Settlement was the critical disturbance that transformed an ecosystem that was already stressed by climatic change, as sensed by regional marine sediments. The settlement dates conform to a pattern of older dates developing from throughout the north Atlantic region.

The first records of extinct Caulinia goretskyi (Dorofeev) Dorofeev (synonym Najas goretskyi Dorofeev) in western Europe and of Potamogeton occidentalis M.H. Field sp. nov. were obtained from plant macrofossil analyses of Middle Pleistocene temperate stage deposits exposed at Trez Rouz, Brittany, France. Palynological assemblages recovered suggest correlation with the Holsteinian Stage. This discovery greatly expands the western limit of the paleogeographical distribution of Caulinia goretskyi. The record of Potamogeton occidentalis indicates an affinity with the eastern Asiatic flora, as the fruits resemble those of the extant Potamogeton maackianus A. Bennett. Other extinct Pleistocene species related to P. maackianus have been described, and it is possible to follow the development of this group through the Pleistocene in the European fossil record. These new finds illustrate the importance of a complete paleobotanical approach (both plant macrofossil and palynological analyses). The plant macrofossil assemblages not only provide detailed insight into local vegetation and environment, because they are often not transported long distances (in temperate areas) and can frequently be identified to species level; they can also offer the opportunity to investigate Pleistocene evolutionary trends.

Holocene driftwood is found on postglacial raised beaches of Wollaston Peninsula, Victoria Island. The highest driftwood appears on the 12- to 13-m beach, which formed about 4000 yr B.P., and is common on beaches 12–6 m in elevation. The earliest Paleoeskimo dwelling features also occur on the 12- to 13-m beach. Wood increases on the 5- to 6-m beach, which formed about 2000 yr B.P., and is abundant below that level. Thus, zonation of wood suggests the following hypotheses: (1) that the coastal Mackenzie Current, the source of modern driftwood, did not operate before 4000 yr B.P. and lacked its present vigor or persistence until 2000 yr B.P.; and (2) that the apparent sudden influx of driftwood at 4000 yr B.P. may have provided a fuel resource and (or) may have been related to conditions that enabled first peopling. Radiocarbon ages indicate that (1) the first wood arrived about 4700 yr B.P.; (2) little wood arrived from 4700–2000 yr B.P.; and (3) influx of wood was episodic after 2000 yr B.P. Much of the wood that arrived after 1100 yr B.P. was redistributed by people and scattered on higher beaches. Explanation of the evident correlation between highest wood and highest dwelling features must await archaeological studies.

Outcrops of buried soils on lake-plains and glacial headlands along Lake Michigan's eastern shore suggest that periodic dune-building has occurred there after relatively long (≥100 yr) periods of low sand supply. We located, described, and radiocarbon dated 75 such buried soils that crop out in 32 coastal dune fields beside the lake. We assume that peaks in probability distributions of calibrated 14C ages obtained from wood, charcoal, and other organic matter from buried A horizons approximate the time of soil burial by dunes. Plotted against a late Holocene lake-level curve for Lake Michigan, these peaks are closely associated with many ∼150-yr lake highstands previously inferred from beach ridge studies. Intervening periods of lower lake levels and relative sand starvation apparently permitted forestation and soil development at the sites we studied. While late Holocene lake-level change led to development and preservation of prominent foredunes along the southern and southwestern shores of Lake Michigan, the modern dune landscape of the eastern shore is dominated by perched dunes formed during ∼150-yr lake highstands over the past 1500 yr.

Pittsburg Basin, in south-central Illinois, contains a sediment record extending from the present back to the end of the late Illinoian glaciation, when central Illinois was covered with Picea/Pinus forest. During the last interglaciation, a temperate deciduous forest more diverse than Holocene Quercus/Carya forest replaced the Illinoian late-glacial boreal forest. Prairie pollen types and the charcoal/pollen ratio, indicating fire frequency, temporarily increased. Then forest, with high Juniperus percentages, became dominant once more, as the charcoal/pollen ratio dropped. After the last interglaciation, the charcoal/pollen ratio increased again and prairie and wetland surrounded Pittsburg Basin through the entire Wisconsinan glacial age. The area was still prairie in late Wisconsinan time, but with some Picea and Pinus. During the Holocene, the region has been a mixture of prairie and Quercus/Carya forest. During the last interglaciation, Pittsburg Basin was surrounded by vegetation different from that surrounding it during the present interglaciation. Rather than indicating substantial differences in climate between analogous phases of different glacial/interglacial cycles, this variation may be due to changes in fire frequency, which could be caused by small changes in climate, human activity, or differences in soil.

A Holocene record of pollen deposition was obtained from an ice core drilled through the Agassiz Ice Cap. The pollen records long-range atmospheric transport to the ice cap. Pollen concentrations were highest in the early Holocene (∼15 grains/L), decreased in the mid-Holocene (∼6 grains/L), and increased in the late Holocene (∼9 grains/L). In the early Holocene, the higher concentration of tree pollen at a time when large parts of Canada were still ice-covered, and when forest was generally farther away, implies that atmospheric circulation was stronger than at present. Following deglaciation, as vegetation migrated north in central and eastern Canada, sources of pollen were closer to the Agassiz Ice Cap. However, the concentration of tree pollen decreased on the ice cap. This was followed by several relatively rapid changes after 3500 yr ago. Until ca. 3500 yr ago, the pollen concentration curves resembled the ice core δ18O and summer melt layer curves, both regarded as temperature proxies.

Fossiliferous middle Pleistocene sediments of the Tarija basin of southern Bolivia contain a classic Ensenadan land-mammal fauna. New carbon isotopic data reported here for 50 specimens of the grazing mammals Equus (horse) and Cuvieronius (mastodon), documented from eight stratigraphic levels at Tarija, vary significantly in the δ13C values of their teeth. The pattern of variation appears to reflect the proportion of C3 and C4 grasses eaten during colder (more C3) and warmer (more C4) times. Within age limits set by associated magnetostratigraphy, the cold periods can be correlated with particular even-numbered stages in the marine oxygen-isotope record, and the warm periods can be correlated with odd-numbered stages. The oldest fossil teeth analyzed from the Tarija section can thereby be assigned to stage 29, and the youngest to stages 17 or 15, that is; the teeth range in age from about 1.1 myr to as young as 0.7 myr. Based on correlation of the upper part of the Tarija beds to the isotopic stages, the upper limit of the Ensenadan land-mammal age is between 0.7 and 0.6 myr, which is younger than stated in most previous studies.

Pollen data from Lake Maliq, the first from Albania, contribute new information to the discussion of the vegetational, hydrological, and climatological history of the Balkans since 12,000 yr B.P. During late-glacial time, a perennial lake expanded at Maliq. It was surrounded by a complex vegetation association composed of steppe and mixed forest elements. The highly diverse forest flora suggest that late-glacial forest refugia were more developed here at middle altitude, rather than at higher altitude as previously suggested. The forest developed after 9800 yr B.P., while the water level remained high in the Korçë basin until 5000 yr B.P. Different environmental conditions, characterized by lower available moisture and warmer winters, progressively took place after this date. Human activity in the Korçë basin ca. 4500 yr B.P. was coeval with conditions characterized by an increase in winter temperatures and a decrease in summer moisture.

Modern pollen samples collected from 80 locations and representing a wide array of mature habitats in Panama and Costa Rica provide analogs to assist in the interpretation of fossil pollen records. Pollen spectra accurately reflect changes in actual forest types. Upslope transport of pollen of anemophilous species is evident in the sparsely vegetated montane samples. However, the corresponding downslope transport of these prolific pollen producers is masked by local pollen production. Mean pollen representation across gradients of mean annual temperature (MAT; 4°C increments) and mean annual precipitation (MAP; 500 mm increments) for 17 pollen types are presented as response matrices. Although preliminary in nature, these response matrices present a clearer image of pollen representation than can be obtained by considering gradients of MAT or MAP alone.