Lateglacial Environmental Changes Research Articles

Paleoenvironmental changes in the Brazilian Pampa based on carbon and oxygen stable isotope analysis of Pleistocene camelid tooth enamel

ABSTRACTHere we present paleoenvironmental and paleoclimatic reconstructions of the Brazilian Pampa based on stable isotopes (δ13C, δ18O) in tooth enamel of the Pleistocene camelidsLama guanicoeandHemiauchenia paradoxafrom the Chuy Creek fossil assemblage, including oneH. paradoxafrom a stratigraphic level within a loess unit deposited during the Last Glacial Maximum (26.5–19 ka b2k). The δ13C results show that both species fed mostly on C3 plants, although the mixed diets ofL. guanicoeincluded ~30% C4 or CAM plants.H.paradoxahad C3 diets with <10% C4 or CAM plants. Both species exhibit higher δ18O and aridity indexes compared to other mammals from the assemblage, consistent with ingestion of18O‐enriched water from plants growing in arid/semi‐arid conditions. A comparison with δ13C of camelids from Argentina indicates the camelids from Chuy Creek fed on vegetation similar to that of Dry Pampa, Monte and Patagonic xerophytic steppes. Aridification and expansion of dry steppes in southern Brazil suggest a climate‐driven northeastwards shift of the Arid Diagonal of South America that may have contributed to local extinction of the Pleistocene megafauna. These Lateglacial environmental changes are reflected in the characteristics of the plant and mammalian assemblages of the modern Brazilian Pampa.

Lateglacial environmental change in Scotland

ABSTRACTThis paper reviews the evidence for environmental change during the Lateglacial period (c.14.7–11.7 ka), perhaps the most intensively studied episode in the Quaternary history of Scotland. It considers first the stratigraphic subdivision and nomenclature of the Lateglacial, before proceeding to a discussion of the various lines of proxy evidence that have been used to reconstruct the spatial and temporal patterns of environmental change during this time period. These include pollen and plant macrofossil data; coleopteran and chironomid records; diatom data; stable isotope and geochemical records; and evidence for human activity. The paper then considers the principal methods that have been employed to date and correlate Lateglacial events: radiocarbon dating; surface exposure dating; varve chronology; and tephrochronology. This is followed by an examination of the constraints imposed on environmental reconstructions, an account of the ways in which the evidence can be employed in the development of an event stratigraphy for the Lateglacial in Scotland, and a proposal for a provisional Lateglacial type sequence (stratotype) at Whitrig Bog in SE Scotland. Emphasis is placed throughout on the potential linkages between the Scottish records and the isotopic signal in the Greenland ice cores, which forms the stratigraphic template for the N Atlantic region. The paper concludes with a discussion of the strategies and approaches that should underpin future research programmes on Lateglacial environmental change in Scotland.

Climate and landscape in Italy during Late Epigravettian. The Late Glacial small mammal sequence of Riparo Tagliente (Stallavena di Grezzana, Verona, Italy)

The site of Riparo Tagliente (north-eastern Italy) contains one of the main Upper Pleistocene archaeological sequences of south-western Europe. It also represents a key site for the study of human adaptation to Late Glacial environmental changes in the southern Alpine area. These climatic and environmental conditions are here reconstructed based on small mammal assemblages, using the Bioclimatic model and Habitat Weighting methods. Climate proxies indicate a rise in temperature during the transition between HE1 and the Bølling-Allerød interstadial, while the landscape surrounding the shelter was still dominated by open grasslands. By comparing the data obtained from Riparo Tagliente with other coeval small mammal faunas from the Italian Peninsula and Europe we contribute to the reconstruction of the processes of faunal renewal registered during the Late Glacial across the continent and of the climatic and environmental context in which the Late Epigravettian hunter-gatherer groups lived.

Patterns and chronology of the Lateglacial environmental development at Pamerkiai and Kašučiai, Lithuania

This paper focuses on the characteristics and chronology of Lateglacial environmental changes in Lithuania, in the context of the North Atlantic climatic events of the Last Termination. The reconstruction of environmental changes and their magnitude is based on new multiproxy data (lithology, pollen, plant macrofossils, diatoms and 14C dating) obtained from two sediment sequences from southeastern (Pamerkiai outcrop) and western (Kašučiai Lake) Lithuania. The spread of sparse open-ground vegetation with the patchy occurrence of Betula nana and Betula sect. Albae on the nutrient-poor unstable soils surrounding the oxygen-rich, alkaline water basins has been recorded pre-14,300 cal BP (correlated to the GI-1e event). The increased abundance of cold-tolerant plants ( Artemisia, Chenopodiaceae and Armeria sp.) indicates a short climatic deterioration from about 14,300 to 14,100 cal BP, tentatively correlated with the GI-1d event. The palaeobotanical record indicates a continuing climatic amelioration and forestation of the region with open Betula- Pinus forest during 13,700–12,600 cal BP (approximately correlated to the GI-1c-a event). However, from 13,300 cal BP the spread of Artemisia, Chenopodiaceae and Thalictrum implies some instability in environmental conditions. Climate cooling resulted in a significant reduction in tree cover contemporaneous with the formation of an open, herb–grass dominated landscape, and low water levels in the nutrient-limited water basins during the period 12,600–11,100 cal BP. This has been tentatively correlated to the GS-1. However, the gradual expansion of Pinus after 11,500 cal BP suggests some amelioration of the climate, which might have been more apparent in the coastal region of Lithuania than in the rest of the country. Finally, after 11,100 cal BP, and contemporaneous with these improved climatic conditions, there was a rapid expansion of Betula and eutrophication of the water basins. These registered environmental shifts coincide with those of the North Atlantic region, which have been determined as climatically driven, and indicate the broad areal extent of these changes during the Lateglacial period.

Devensian Late-glacial environmental change in the Gordano Valley, North Somerset, England: a rare archive for southwest Britain

The Late-glacial and Holocene environmental history of the Gordano Valley, North Somerset, UK has been reconstructed using pollen, sediment particle size and mineralogical analyses and radiocarbon dating. A Devensian sediment ridge across the valley confined the waters of a small lake, within which the initial sedimentation was minerogenic. Radiocarbon dating of overlying organic-rich deposits suggests that this began late in the Dimlington Stadial c. 18,000–15,000 Cal. BP. Petrographic analyses indicate the minerogenic sediments were partly wind-blown in origin. Climatic amelioration during the Windermere Interstadial c. 15,000 Cal. BP encouraged a shift from minerogenic to biogenic sedimentation. A brief return to minerogenic sedimentation between c. 10,400 and c. 9,520 Cal. BP was followed by uninterrupted fen peat accumulation throughout the Holocene. The later minerogenic horizon appears to represent the Loch Lomond Stadial. Few stratigraphic sequences preserving the complete Devensian Late-glacial–Holocene transition exist in southwest Britain, making the sedimentary archive of the Gordano Valley valuable regionally for reconstructing Late-glacial climate change.

Marine and limnic radiocarbon reservoir corrections for studies of late- and postglacial environments in Georgia Basin and Puget Lowland, British Columbia, Canada and Washington, USA

Models of late-glacial environmental change in coastal areas are commonly based on radiocarbon ages on marine shell and basal lake sediments, both of which may be compromised by reservoir effects. The magnitude of the oceanic reservoir age in the inland waters of the Georgia Basin and Puget Lowland of northwestern North America is inferred from radiocarbon ages on shell-wood pairs in Saanich Inlet and previously published estimates. The weighted mean oceanic reservoir correction in the early and mid Holocene is −720±90 yr, slightly smaller than, but not significantly different from, the modern value. The correction in late-glacial time is −950±50 yr. Valley-head sites yield higher reservoir values (−1200±130 yr) immediately after deglaciation. The magnitude of the gyttja reservoir effect is inferred from pairs of bulk gyttja and plant macrofossil ages from four lakes in the region. Incorporation of old carbon into basal gyttja yields ages from bulk samples that are initially about 600 yr too old. The reservoir age declines to less than 100 yr after the first millennium of lake development. When these corrections are accounted for, dates of deglaciation and late-glacial sea-level change in the study area are pushed forward in time by more than 500 yr.

Devensian Lateglacial environmental changes in Britain: a multi-proxy environmental record from Llanilid, South Wales, UK

A multi-proxy environmental record for the Devensian (Weichselian) Lateglacial and early Holocene periods, which includes pollen, plant macrofossil, coleopteran, geochemical and stable-isotope data, is described from a site at Llanilid, South Wales, UK. The geochronology of the sequence is derived from two age–depth models which show a broad measure of agreement over much of the profile. This data set provides the basis for a detailed reconstruction of changing environmental conditions in western Britain during the transition from the Last Cold Stage to the present (Holocene) interglacial (ca 15,000–10,000 cal yr BP). Two marked cooling episodes are recorded during the course of the Lateglacial Interstadial (Greenland Interstadial 1), with mean July temperatures falling by more than 5°C from a maximum of around 20°C during the early Interstadial, and by a further 4–5°C around 13,100 cal yr BP. The initial drop in temperature led to a reduction in Juniperus scrub, while the second, and more abrupt temperature decline resulted in a significant contraction in areas of Betula woodland. A relatively slight and short-lived warming during the later Interstadial enabled tree birch to expand once again. Mean July temperatures of 10–11°C characterised the Loch Lomond/Younger Dryas Stadial (Greenland Stadial 1) between ca 12,600 and 11,400 cal yr BP, during which time a scrub tundra with Betula, Salix and a range of open-habitat taxa became established locally. The onset of the Holocene Interglacial at ca 11,400 cal yr BP is marked by an abrupt temperature rise of the order of 9°C, and by the rapid expansion of Betula woodland. The Llanilid palaeoclimate record is similar to that from the Gransmoor site in northeast England, and also to the climatic sequence inferred from the GRIP ice core, particularly during the later part of the Lateglacial Interstadial (ca 14,000–12,600 cal yr BP), during the Loch Lomond/Younger Dryas Stadial and in the early Holocene. The Llanilid chronology is less secure during the early part of the Lateglacial Interstadial (pre-14,000 cal yr BP), but it is possible that warming may have begun earlier in this part of western Britain than in Greenland.

Oxygen-isotope wiggle matching as a tool for synchronising ice-core and terrestrial records over Termination 1

In NW Europe, the large number of terrestrial records that are now available from Termination 1 (15–10 kcal yr BP) form the basis for a highly detailed picture of Lateglacial environmental change. Nevertheless, the Greenland oxygen-isotope records (GRIP/GISP2) are still regarded as the best high-resolution climate proxy for the North Atlantic region. In order to evaluate spatial contrasts and leads and lags in the climate system, integration of ice-core, marine and terrestrial records is becoming increasingly important (INTIMATE objectives). However, comparisons between different environments require a common time-scale for the proxy climate records. Stable isotope analyses performed on Lateglacial lacustrine calcareous deposits in The Netherlands provide a terrestrial oxygen-isotope record, comparable to that from the Greenland ice core. These atmospherically controlled lacustrine oxygen-isotope signals not only constitute an independent palaeoclimatic proxy, but provide the basis for synchronising records from these environments as well. More over, this synchronisation reveals some remarkable aspects concerning the timing of the oxygen isotope and palynological events as recorded in The Netherlands. Above all, oxygen-isotope wiggle matching offers a means of correlating terrestrial and ice-core records.

Late-Glacial Environmental Changes South of the Wisconsinan Terminal Moraine in the Eastern United States

Palynological analyses of two sediment cores, one 2.4 m long from northern Delaware, dated about 16,300 to 14,700 14C yr B.P., and one 1.8 m long from New Jersey just south of the Wisconsinan terminal moraine and dated about 13,600 to 12,500 14C yr B.P., give the first detailed evidence of vegetation in this area during these periods. The overall assemblages are similar to each other, with Picea and Pinus dominating the arboreal pollen and Poaceae and Cyperaceae the herbaceous flora. Nonarboreal pollen contributes about 30–50% of the total, indicating a very open vegetation or a mix of forest patches and open areas. Especially in Delaware, there is a diversity of other herbaceous pollen, including members of the Asteraceae, Fabaceae, and Ranunculaceae. The assemblages do not resemble current North American tundra or boreal forest assemblages; rather, they resemble assemblages characteristic of tundra on recently exposed land surfaces north of the Wisconsinan terminal moraine. The persistence of the assemblages for 1500–2000 years in late-glacial time suggests stable and cold climate during this time of glacier retreat.

Lateglacial environmental changes recorded in calcareous gyttja deposits at Gulickshof, southern Netherlands

Environmental changes were reconstructed from Lateglacial calcareous gyttja deposits at Gulickshof, southern Netherlands. Analyses of pollen, fresh‐water mollusca, stable isotopes and geo‐chemistry were performed and the combined evidence was put into a chronostratigraphic framework based on regional biostratigraphy and accelerator mass spectrometry radiocarbon dating. The pollen diagram showed vegetation development from the Bφlling interstadial into the Late Dryas stadial within 2.9 m of lacustrine deposits. Early in the Allerφd, around 11 900 BP, the composition of aquatic taxa and stable isotopes of calcium carbonate changed significantly. It appears that the final melting of relic ground‐ice and subsequent re‐establishment of the hydrological cell early in the Allerφd were responsible for these changes. Later in the Allerφd, around 11 250 BP, the disappearance of molluscs, changes in vegetation and isotope composition all point to colder climate conditions attributable to the Gerzensee oscillation. The combination of different lines of evidence in these types of deposits proves to be an excellent tool for unravelling climate and environmental signals.

Lateglacial environmental changes recorded in calcareous gyttja deposits at Gulickshof, southern Netherlands

Lateglacial environmental changes recorded in calcareous gyttja deposits at Gulickshof, southern Netherlands

Wisconsinan Late‐glacial environmental change in Newfoundland: A regional review

AbstractThe distribution of 75 lake and bog sites, from which pollen stratigraphical evidence relevant to the late Quaternary of Newfoundland has been obtained, is presented. The detailed records of lithology, pollen and diatoms, supplemented by geochemical data, are discussed for three of the sites — Southwest Brook Lake, Woody Hill Brook Pond and Leading Tickles — and interpretations made are based on vegetational history, relative climatic changes and extent of ice cover. Radiocarbon data from 14 sites are summarised. A summary chart of Late‐glacial environmental changes, including a qualitative palaeotemperature curve, is provided.

The Weichselian Late‐glacial in southwestern Europe (Iberian Peninsula, Pyrenees, Massif Central, northern Apennines)

AbstractThis paper presents a summary of Late‐glacial environmental changes in southwestern Europe (lberian Peninsula, Pyrenees, Massif Central and the northern Apennines). The emphasis is on palaeoclimatic interpretations inferred from key sites in the region from which the most detailed records are available and which have been radiocarbon dated. The earliest evidence for climatic improvement following the end of the last glacial stage is dated to ca. 15 ka BP and is found at a few sites only. By 13 ka BP, a more widespread and marked climatic improvement is evident, although it is difficult to be precise in the timing and magnitude of the event. There are significant variations in detail between the Late‐glacial records, but evidence for a significant cooling correlated with the Younger Dryas event is widespread throughout the region. Just two sites in the region provide evidence for an earlier, less emphatic phase of climatic cooling, which is tentatively equated with the ‘Older Dryas’ of continental northern Europe. Dry conditions appear to have predominated throughout the region in the later part of the Younger Dryas and the early Holocene.

Wisconsinan Late‐glacial environmental change in Nova Scotia: A regional synthesis

AbstractA synthesis of the interpreted vegetational and climatic history of Nova Scotia during the Wisconsinan Late‐glacial period (14‐9 ka BP) is presented and described in 500‐year intervals. The concomitant regional deglaciation history of the region is also described. A synthesis chart is provided which includes a qualitative curve of temperature reconstructions for the Lateglacial period.

Intensity, gradients and reversals in late glacial environmental change in east-central north America

Radiocarbon-dated pollen sites from the Allegheny Plateau (east) and the Till Plains (west) document significant vegetational and climatic change between 15,000 and 9000 14C BP south of the Great Lakes. Although limited by the problems of no-analog vegetation, pollen transfer functions (TF) and response surfaces (RS) quantify the climatic changes, including a cold oscillation chronologically equivalent to the European Younger Dryas. Phase I: before ca. 13,000 14C BP, conditions across the region were similar, (January −20 to −16°C; July 12°C (RS) or 19°C (TF); mean annual precipitation, 80 to 90 cm year −1). Phase IIa: between ca. 13,000 and 11,000 14C BP, N-S and E-W climate gradients were initiated. Till Plains temperatures increased by ca. 8°C in January and by 8°C (RS) or 2–3°C (TF) in July. Plateau increases for January were 3–6°C and for July were 8°C (RS) or 1–2°C (TF). Precipitation generally increased somewhat. Phase IIb: ca. 11,000 to 10,000 14C BP, gradients became less pronounced. The western sites show a climate reversal (January drop of ca. −5 to −2°C; July drop to ca. 1–2°C), becoming more like the Plateau sites which show a brief, small fluctuation. This is followed by an abrupt 10 to 20 cm year −1 reduction in precipitation, January warming of ca. 3°C and continued cooler Julys. Phase III: After 10,000 14C BP, gradients similar to those of today developed. The changes in Phases IIb and III are probably linked to the drainage history of the Great Lakes and via that history to the changes on the European continent.

Lateglacial environmental changes in the Netherlands: Spatial and temporal patterns: A contribution to the ‘North Atlantic seaboard programme’ of IGCP-253, ‘Termination of the Pleistocene’

The history of vegetational changes during the Weichselian Lateglacial in the Netherlands is based primarily on pollen records derived from lacustrine sediments. They provide a fairly consistent picture of progressive, followed by retrogressive, vegetation succession through time. Problems arise, however, when we try to match pollen records obtained from terrestrial peat sequences with those obtained from lacustrine deposits. This is especially the case at around about 12,000 BP: conditions seem to have varied significantly depending on the geomorphological position of individual site. Terrestrial sites are more prone to hiatuses in response to episodes of pronounced reductions in effective precipitation. The spread of Pinus from ca. 11,300 BP, which has been interpreted traditionally as a successive phase in vegetational development, coincides with changes in the local vegetation that indicate more intense freeze-thaw conditions. More continental conditions are assumed, implying more severe winters by comparison with the preceding time-interval. At ca. 10,850 BP, both vegetation and coleopteran evidence indicate a distinct drop in the average July temperature, from 18-15°C to 11-10°C. Consequently, the mean annual temperature was also lowered (estimated to between −2 and −5°C) and conditions approximated those of permafrost environments. Simultaneously, effective precipitation increased considerably resulting in a pronounced rise in lake-levels and large-scale floodings of rivers. Soon after, at ca. 10,500 BP, summer temperatures appear to have risen while effective precipitation declined considerably resulting in a fall in lake-levels and periodic exposure of river beds, which provided sources for the accumulation of large inland dunes.

Late Glacial environmental changes indicated by a coleopteran succession from North Wales

This investigation was designed to compare the environmental inferences that can be made from fossil Coleoptera with those that can be made from palynological data. In the Glanllynnau kettle hole, sedimentation began at 14,000 BP and continued until about 10,000 BP. The Coleoptera from these deposits show that during this period there was only one climatic oscillation and that this differed in both timing and intensity from oscillations inferred from palynological evidence. Thus, at about 13,000 BP, an intensely cold continental climate suddenly gave place to a period with summer temperatures at least as warm as those at the present day, but during this episode the landscape was entirely without trees. From 12,000 BP to about 10,000 BP there was a progressive deterioration in the temperature, and the period of Betula forest, broadly equivalent to the Allerød, is shown to have a less thermophilous fauna than that of the previous pollen Zone I. An attempt is made to explain this anomaly in terms of the differential rate of response of the plants and animals to rapid climatic changes.