bluuebunny/crossref_metadata_2025 huggingface dataset:
Upper Quaternary vegetation dynamics and palaeoclimatology of the La Chonta bog area (Cordillera de Talamanca, Costa Rica)
Authors: Hooghiemstra H. , Cleef A. M. , Noldus C. W. , Kappelle M.
Published: February 2007

Two pollen records from La Chonta bog (2310 m altitude) and one pollen record of a soil profile (2430 m altitude) at a short distance from the bog permit the reconstruction of the vegetational history and climatic sequence of probably the last ca. 80 000 yr of the Cordillera de Talamanca, Costa Rica. The three pollen records can be correlated on the basis of three radiocarbon‐dated horizons (> 39 900 yr BP, 34 850 yr BP and 1390 yr BP) and palynostratigraphy. Pollen concentration data provide indirect time control between radiocarbon‐dated horizons of the La Chonta 2 core. During the Early Glacial successive fluctuations of the upper forest line occurred between ca. 2300 m and 2800 m altitude and the bog is alternately situated close to the subalpine rainforest belt and in the uppermontane rainforest belt. During the Pleniglacial (ca. 50 000‐13 000 yr BP) the forest line fell to ca. 2000 m altitude and paramo vegetation surrounded the La Chonta site. During the Late Glacial the forest line shifted rapidly in ca. 270 yr to 2700–2800 m altitude and the lake became surrounded by Quercus‐dominated upper montane rainforest during a period of ca. 1655 yr. A distinct climate cooling (by 2–2.5°C) followed during ca. 580 yr and the upper forest line dropped to ca. 2400 m altitude. This temperature rebound is probably equivalent to the Younger Dryas event. In the depression extensive Alnus carr and swamp vegetation developed. Finally, during the Holocene, the forest line shifted to 3300–3500 m elevation and the lower montane rainforest reached close to ca. 2300 m altitude. In the later part of the Holocene subparamo scrub with Hypericum, Puya, Compositae, Escallonia and Ericaceae largely replaced Alnus carr and the regional and local vegetation closely resembles the presentday composition. During the Last Glacial to Holocene transition a shift of the upper forest line of ca. 1400 m is inferred, corresponding to a glacial temperature depression at 2300 m altitude of ca. 8°C.
The origin of very flinty dry‐valley deposits in the Marlow area, Buckinghamshire, England
Authors: Espejo J. M. Recio , Catt J. A. , Mackney D.
Published: February 2007

Some of the soils on the floors of dry chalkland valleys north of the River Thames in the Marlow area have surface horizons of moderately to very flinty, weakly or non‐calcareous, poorly sorted loams, which were deposited in the late Holocene. These overlie typical chalkland gelifluction and periglacial fluvial deposits. Fine calcareous colluvial loams also occur but are less common than in valleys elsewhere on the English chalk. Particle size and mineralogical analyses suggest that the loamy matrix of the flinty surface horizons was derived from loess and early Tnames terrace deposits or Clay‐with‐flints occurring on interfluves between the dry‐valleys. On the evidence of their poorly sorted nature, lack of carbonate, abundance of large flints and irregularly ridged surfaces, it is suggested that they originated mainly as valley‐side debris flows.
Source of a freshwater influx at the last glacial maximum in the Indian Ocean: An alternative interpretation
Authors: Gupta S. K. , Sharma P. , Shah S. K.
Published: February 2007

Recent analysis of a sediment core in the eastern Arabian Sea revealed a negative pulse of about 1% in the δ18O value of the planktonic Foraminifera around the last glacial maximum (LGM). This pulse has been attributed to (i) increased runoff into the Bay of Bengal from the east‐flowing south Indian rivers due to enhancement of the northeast winter monsoon, and (ii) an increase in Arabian sea‐surface temperature caused by the weakening of the southwest monsoon at the LGM. We show that the speculation on which the latter hypothesis is based, is not supported by observational data and cannot fully account for the observed magnitude of the spike. With a view to assessing the validity of the first mechanism, we have modelled the mixed layer of the Bay of Bengal as a well‐mixed box. The model calculations show that to account for the pulse requires a change of about 10% in either the annual rate of river input or its isotopic composition. For the northeast monsoon to account for the pulse it would mean that the rainfall should have increased by a factor of five to ten during the LGM. No evidence for such an increase is indicated in the available palaeoclimatic data. We explain the freshwater spike by invoking increased discharge of glacial meltwater from the Tibetan plateau into the Bay of Bengal. We show that the proxy climate data from the Indo‐Tibetan region that has become available recently provides substantial evidence for the occurrence of a warming event around the LGM, which supports our mechanism.
Late Quaternary fluvial activity in the dry valleys (mekgacha) of the Middle and Southern Kalahari, southern Africa
Authors: Shaw Paul A. , Thomas David S. G. , Nash David J.
Published: February 2007

Kalahari dry ‘fossil’ valleys (mekgacha) have been little used in palaeoenvironmental reconstruction, partly because the origins and functions of the valleys are a subject of debate, and partly because they contain few datable sediments. In the Middle Kalahari the valleys are endoreic, and, following a decline in ground‐water tables owing to human interference over the past 150 years, rarely contain water. Evidence from three sites suggests that the valleys contained standing water between 15000 and 12000 yr BP, and that the main Okwa‐Mmone system flowed into palaeolake Makgadikgadi at 920 m a.s.l. during this period.

The Southern Kalahari contains the exoreic Molopo network which is hydrologically more active, being prone to surface flows in response to extreme rainfall events. The spring—fed Kuruman valley has two terraces, the lower composed of a series of flood deposits of late Holocene age. The flood of February 1988 provides a useful analogue for the conditions under which these deposits were formed, and of the temporal regime of the Kuruman River. Comparison with adjacent sites suggests that evidence put forward to indicate cycles of climatic amelioration in the last 4000 yr may, in part, represents the effect of extreme precipitation events. Historical floods show a strong correlation to Southern Oscillation high‐phase (cold event) episodes, suggesting possibilities for extension of the Southern Oscillation record through palaeoflood studies.
Constraints on ice‐sheet thickness over Tibet during the last 40 000 years
Authors: Gupta S. K. , Sharma P. , Shah S. K.
Published: February 2007

The Late Quaternary glaciation of Tibet has received considerable attention in the last few decades due to its influence on the regional climate, especially the Asian summer monsoon. Recently, however, it has been argued that the Tibetan ice sheet also might have played an important role in initiating global‐scale palaeoclimatic changes. Controversy, however, exists on the nature of Late Quaternary ice cover over Tibet due largely to the subjectivity in the interpretation of the sparse and complex geomorphological evidence. We have examined this problem in the light of δ 18O data (a temperature proxy) of ice cores‐from the Dunde ice cap on the northern flank of Tibet. Considering only the gross features in the Dunde ice‐core isotopic data, we have interpreted a temperature decrease of 4°–6°C and consequent lowering of equilibrium line altitude (ELA) in the range 700–850 m during the last glacial stage (LGS). This could have caused depression of the snow line below the mean altitutde of the Tibetan plateau, resulting in an areally extensive but marginally thick ice cover. However, if one also considers the possibility that precipitation on the Tibetan plateau during LGS may have been significantly lower than at present, the ELA depression would be much less than that estimated by considering the temperature effect alone.
Post‐glacial loess deposition in a montane environment: South Thompson River valley, British Columbia, Canada
Authors: Roberts Michael C. , Cunningham Frank F.
Published: February 2007

In the late Wisconsinan, the South Thompson River valley, British Columbia, was occupied by an ice‐dammed lake. After the lake drained, the exposed lacustrine silt became the source material for a Holocene loess. The purpose of this paper is to establish the stratigraphic, depositional and geomorphic framework of loess occurring along the South Thompson River valley immediately east of Kamloops, British Columbia. This montane environment of loess deposition was characterised by active slope and fluvial processes depositing sediments contemporaneously with the accumulation of loess.

The loess reaches an average of 4 m in thickness in the central part of the valley and thins towards the valley sides. Two tephras—Mount St Helens Y (3.4 ka) and Mount Mazama (6.8 ka)— occur in the loess and are invaluable stratigraphic markers. Most of the loess was probably deposited between 8.2 ka and 3.4 ka, a period coinciding with mid‐Holocene increased summer temperatures and decreased precipitation in south‐central British Columbia. Debris flows and small streams, originating on the valley sides, flowed out on to the loess depositing sand and gravel beds. These deposits form a definite proximal—distal relation across valley with the slope‐derived sediments decreasing and the loess increasing in thickness towards the centre of the valley.

The lactustrine silt particles were mobilised by diurnal mountain and valley, gravity, and canalised winds flowing within the South Thompson valley. An analysis of contemporary wind‐flow data was undertaken to provide a possible analogue for valley wind flows in the mid‐Holocene.
A uranium‐thorium dated late Eemian or early midlandian organic deposit from near Kilfenora between Spa and Fenit, Co. Kerry, Ireland
Authors: Heijnis Henk , Ruddock Julie , Coxon Peter
Published: February 2007

This paper discusses the dating of stratigraphically important Quaternary sequences from a site near Fenit, Co. Kerry, which have been the subject of debate since they were first described by Mitchell in 1970. The overall stratigraphy of the Quaternary deposits have been investigated and detailed analyses of the organic material carried out. Pollen from biogenic sediments have been analysed and samples of peat dated using the uranium‐thorium disequilibrium method. The pollen assemblages match no others previously recorded in Ireland and appear to represent a cool temperate phase following the last interglacial. The uranium‐thorium dates of between 114000 and 123 000 yr BP indicate that the deposit dates from Oxygen Isotope Stage 5, possibly post‐dating the last temperate stage (the Eemian Stage interglacial; Oxygen Isotope Substage 5e). The dating of this deposit and the realisation that it is not penultimate temperate stage (Gortian) in age invalidates much recent speculation on the age of the Gortian interglacial.
‘Little ice age’ variations of outlet glaciers from the jostedalsbreen ice‐cap, Southern Norway: A regional lichenometric‐dating study of ice‐marginal moraine sequences and their climatic significance
Authors: Bickerton Richard W. , Matthews John A.
Published: February 2007

Complex moraine‐ridge sequences in front of seven outlet glaciers of the Jostedalsbreen ice‐cap (Austerdalsbreen, Bergsetbreen, Fåbergstølsbreen, Lodalsbreen, Stegaholbreen, Tuftebreen, Bødalsbreen) are dated using families of lichenometric dating curves established previously at an eighth outlet (Nigardsbreen). Applicability of the Nigardsbreen curves at the regional level is tested using independent historical evidence: moraines deposited during the present century are dated to an accuracy of ± 9.4 yr (16.0%), and most of them are dated to an accuracy of ± 5.5 yr (9.4%). Results from the moraine sequences are combined to form a composite ‘Jostedalsbreen’ record. Median predicted dates for moraine ridges cluster around AD 1939 ± 2 yr, 1929 ± 3, 1908 ± 3, 1886 ± 5, 1875 ± 2, 1867 ± 4, 1855 ± 3, 1842 ± 5, 1822 ± 5, 1807 ± 4 and 1785 ± 5. At least four glaciers reached their ‘Little ice age’ maxima prior to AD 1780, two (Nigardsbreen and Bødalsbreen) at ca. 1750, one (Fåbergstølsbreen) at ca. 1705. Stegaholbreen attained its maximum ca. 1863.

Since the ‘Little ice age’ maximum, and despite large differences in glacier size, frontal variations of the various outlets have exhibited a high degree of synchroneity, which suggests that the moraine sequences contain a sensitive record of high‐frequency climatic variations over the last ca. 250 yr. During the early twentieth century, measured readvances of the order of 5–150 m over 1–10 yr led to moraine formation. Dendroclimatic evidence indicates that since the late eighteenth century, moraine ridges formed about 5 yr after summer temperature minima and correlate with runs of cool summers (temperature depression of 0.5–1.0°C below the AD 1700–1950 average). Almost simultaneous glacier advances appear to have been caused by reduced ablation. This near‐immediate response to climatic variation, by glacier tongues that descend to relative low altitudes, is superimposed upon the longer‐term dynamic response of the ice cap to climate.
Thermoluminescence dating of the holsteinian marine formation of Herzeele, northern France
Authors: Balescu Sanda , Lamothe Michel
Published: February 2007

Thermoluminescence dating of potassium feldspar coarse grains from the fossiliferous Holsteinian marine formation of Herzeele, at the southern limit of the North Sea Basin, yields a minimum age of 228 £ 30 ka. A tentative correction for the long‐term fading of the TL signal in potassium feldspar is proposed, assuming a lifetime (τ) of 711 ka. This correction would yield a preliminary age estimate of 271 £ 36 ka. These results support a minimum Oxygen Isotope Stage 7 age, but do not preclude, at this stage of our research, a possible correlation with late Oxygen Isotope Stage 9. These results are in agreement, within the error of the method, with independent absolute dates (U‐Th and ESR) obtained onin situmarine shells, which range from 225 ka to 348 ka. This study provides evidence of the reliability of TL age estimates on potassium feldspar coarse grains from shallow‐marine sediments older than the Last Interglacial.
OSL and TL dating of buried podsols and overlying sands in Ostrobothnia, western Finland
Authors: Hütt G. , Jungner H. , Kujansuu R. , Saarnisto M.
Published: February 2007

In Ostrobothnia, western Finland, buried fossil soils have been recognised in a number of places in the sandy sediments that occur between glaciofluvial deposits and overlying till. Samples from the soil horizons as well as below and above them were taken for optically stimulated luminescence (OSL) dating. The same sites were also sampled for thermoluminescence (TL) dating. Altogether five TL dates and seventeen OSL dates were obtained. The OSL dates can be grouped into two age classes, (i) 120‐163 ka and (ii) 76‐106 ka, whereas all TL dates are of the order 135‐155 ka. A comparison between the results obtained from the two dating methods shows that OSL dates are generally younger than the TL dates for the same sample. The discrepancy may arise partly from problems of setting a correct residual level in TL dating. If this is the case then the TL dates may indicate an upper limit for the true age. The results support the geological interpretation that the fossil soils were formed during the last interglacial, that the soil‐forming processes possibly also continued during the first Early Weichselian stadial and interstadial (Brørupsensu lato), and that in general the till‐covered glaciofluvial sequences, interpreted as eskers in Ostrobothnia, were deposited during the Saalian or Early Weichselian deglaciation.
Late quaternary chronology of the Taitao Peninsula, southern Chile
Authors: Lumley Susie H. , Switsur Roy
Published: February 2007

Six new radiocarbon ages and a pollen sequence are provided for Laguna Stibnite, a small lake on the Taitao Peninsula, Chile (latitude 46°25'S, longitude 74°24'W). The sediments record a late‐glacial to present sequence, with a basal age of 14 335 ± 145 yr BP (Q‐2840). The radiocarbon ages provide the basis for a sound chronology in a region of Chile where few palynological studies have been made and where previous radiocarbon ages are ambiguous. The chronology from Laguna Stibnite supports the acceptance of a radiocarbon chronology based on wood fragments (rather than bulk analysis) at a site near Puerto Edén further south in the Chilean Channels (49°08'S). These data from Laguna Stibnite provide evidence for an early deglaciation (before 14 000 yr BP) in this region of southern Chile. The sequence provides no evidence for a climatic reversal between 11 000 yr BP and 10 000 yr BP, the so‐called Younger Dryas chron.
Thaw modification of frost‐fissure wedges, Richards Island, Pleistocene Mackenzie Delta, Western Arctic Canada
Authors: Murton Julian B. , French Hugh M.
Published: February 2007

Thaw modification is the general process whereby frost‐fissure wedges are modified during thaw, and by which frost‐fissure pseudomorphs may develop. Specific processes of thaw modification are inferred from ice‐wedge pseudomorphs, composite‐wedge pseudomorphs and deformed sand wedges in the Pleistocene Mackenzie Delta: i.e. thermal erosion, collapse, subsidence, refreezing, loading, buoyancy, spreading, folding and shearing.

Thaw modification is believed to result in selective preservation of pseudomorphs and wedges. Sand wedges are more likely to be preserved than are ice‐wedge pseudomorphs or compositewedge pseudomorphs, because only those sand wedges that penetrate massive ice or icy sediments are prone to thaw modification. Furthermore, whereas ice wedges preferentially develop in ice‐rich, fine‐grained sediments (thaw‐sensitive), their pseudomorphs appear to be selectively preserved in ice‐poor, coarse‐grained sediments (thaw‐stable).
The impact of the Laacher See Tephra on terrestrial and aquatic ecosystems in the Black Forest, southern germany
Authors: Lotter A. F. , Birks H. J. B.
Published: February 2007

Late‐glacial lake sediments containing the Laacher See Tephra (LST, 11000 yr BP) have been analysed for pollen and diatoms at two sites (Hirschenmoor, Rotmeer) in the montane belt of the Black Forest (southern Germany) in order to detect the possible impact of this major volcanic eruption on terrestrial and aquatic biota.

The pollen assemblages at both sites show a minor increase in grasses and sedges following the tephra deposition, whereas the pollen of aquatic macrophytes do not show any consistent pattern. Partial redundancy analysis and Monte Carlo permutation tests suggest, however, that the LST had no statistically significant effect either on the terrestrial or aquatic pollen assemblages at either site when the effects of time and climatic change are allowed for statistically.

The diatom assemblages at both sites changed after the deposition of the LST and diatominferred pH estimates suggest a short but non‐significant excursion towards lower values. Multivariate analyses of the diatom data indicate a statistically significant impact of the deposition of the LST and associated changes in sediment lithology on the diatom assemblages when the effects of climatic change and time are allowed for statistically. However, owing to the interaction between tephra and lithology it is not possible to conclude if the diatom changes were caused by the deposition of the LST or by lithological changes.
Glacial Lake development and marine inundation, Deer Lake area, Newfoundland, Canada: Topographically controlled deglaciation of an interior Basin
Authors: Batterson Martin J. , Liverman David G. E. , Kirby Gary E.
Published: February 2007

A large interior basin in west‐central Newfoundland (covering the area of modern Deer Lake, Grand Lake, Sandy Lake and Birchy Lake) is connected to the sea by a narrow breach of a coastal mountain range. During retreat of Late Wisconsinan glaciers, this basin was occupied by a short‐lived glacial lake impounded by remnant ice in coastal fjords, and drained by a spillway at the western end of the lake. Evidence for this lake is fragmentary, and consists of strandline features that fall on a plane of elevation consistent with the post‐glacial isostatic tilt. Following collapse of the ice dams and subsequent lake drainage at some time prior to 12 220 yr BP, the Deer Lake basin was inundated by the sea to an elevation of about 45 m a.s.l. Deltas were formed at the basin edges, and thick successions of fine‐grained rhythmites blanketed the basin floor. Isostatic rebound resulted in falling relative sea levels, and, following a stillstand marked by a period of deltaic deposition at 33 m a.s.l., isolation of the Deer Lake basin from marine influence in the early Holocene.

This style of deglaciation differs from previously accepted models for this part of eastern Canada, which showed progressive retreat from the coast to remnant centres on topographic highs. In the model proposed here, a large, low‐elevation basin was deglaciated early, at a similar time to ice retreat to coastal positions from offshore. This pattern of deglaciation may be found in other areas with similar topographic settings.
Gibbsitic soils on former nunataks: implications for ice sheet reconstruction
Authors: Ballantyne Colin K.
Published: February 2007

X‐ray diffraction analyses of soils above and below a periglacial trimline developed across the basalts of the Trotternish Escarpment (Isle of Skye, Scotland) demonstrate that gibbsite is restricted to soils above the trimline. This suggests that the gibbsite is a relict of pre‐Late Devensian weathering, and that the trimline did not develop after the last ice sheet achieved its maximum thickness. The sharpness of the boundary between frost‐weathered regolith and gibbsitic soils upslope and ice‐scoured bedrock associated with gibbsite‐free soils downslope suggests that the trimline represents the altitude of the last ice sheet at its maximum thickness rather than a former boundary between passive cold‐based ice and erosive warm‐based ice. These findings illustrate how identification of high‐level periglacial trimlines and associated contrasts in clay mineralogy provide a means for constraining reconstructions of the form of the last ice sheets.
The last glaciation of Germania Land and adjacent areas, northeast Greenland
Authors: Landvik Jon Y.
Published: February 2007

A profile across the unglaciated coast of northeast Greenland at 77°N was studied with regard to the Quaternary stratigraphy and glacial history. The Germania Land peninsula is characterised by till‐covered lower ground which contrasts sharply with the blockfields and extensive gelifluction deposits of its higher altitudes. Two glaciations are distinguished. The older one extended over the entire area and had its margin on the continental shelf. The younger one, of Late Weichselian age, reached the present coastline and several mountains and high plateaus on western Germania Land formed nunataks.

The Late Weichselian glaciation was more extensive and occurred later on the Germania Land peninsula than on the coast further south. Radiocarbon dates suggest that the glacier margin rested to the east of the present coastline until ca. 10 000 yr BP. This correlates with the Late Weichselian Milne Land Stage, which is found as a late glacial readvance along the coast of East Greenland. A series of recessional moraines formed during the deglaciation were probably caused by glacier dynamics, as opposed to being of climatic origin.
The objectives of the North Atlantic Seaboard Programme (NASP), a constituent subproject of IGCP‐253
Authors: Lowe J. John , Lowe J. John
Published: February 2007

The North Atlantic Seaboard Programme (NASP) is one of the main sub‐projects of IGCP‐253 (‘Termination of the Pleistocene’) and is concerned with the history of environmental changes in areas adjacent to the North Atlantic during the last glacial‐interglacial transition. The organisation and aims of IGCP‐253 are briefly outlined, to provide the wider context of the NASP. The specific aims of the NASP are introduced, with reference to the importance of the North Atlantic region in late Quaternary research. Some methodological problems are outlined as is the strategy adopted in regional summaries and an overall North Atlantic synthesis, which are presented separately in the issue of Journal of Quaternary Science of which this introductory paper forms a part.
The Devensian/Weichselian Late‐glacial in northwest Europe (Ireland, Britain, north Belgium, The Netherlands, northwest Germany)
Authors: Walker M. J. C. , Bohncke S. J. P. , Coope G. R. , O'Connell M. , Usinger H. , Verbruggen C.
Published: February 2007

A synthesis of environmental changes during the Devensian (Weichselian) Lateglacial period (14‐9 ka BP) is presented for an area extending from Ireland in the west to northwest Germany in the east. Following a brief reference to the problems of chronology, the principal changes in geomorphology and soils, vegetation history and climate experienced in the region during the Late‐glacial are described. Reconstructions of thermal variations during the Late‐glacial period are attempted independently for Ireland, England and Wales, Scotland (Highlands and Islanads), north Belgium, The Netherlands and northwest Germany. The collective palaeotemperature data, based mainly uppoln pollen data but also in Britain and The Netherlands on coleopteran data using the ‘mutual climatic range’ approach, provide an overview of regional differences along an east‐west transect in northwest Europe.
Late Weichselian environmental change in southern Sweden and Denmark
Authors: Berglund Björn E. , Björck Svante , Lemdahl Geoffrey , Bergsten Helene , Nordberg Kjell , Kolstrup Else
Published: February 2007

A synthesis is presented of the envronmental and climatic variations that are inferred to have occurred in southern Sweden (up to latitude 59°N) and Denmark during the Weichselian Late‐glacial (14‐9 ka BP). The chronology and characteristics of the main phases of deglaciation, sea‐level change, periglacial activity, soil development, vegetation cover and climate change are summarised. A curve representing the main changes in temperature, including quantitative estimates based upon beetle data and using the ‘mutual climatic range’ method, is presented.
Late Weichselian environmental change in Norway, including Svalbard
Authors: Birks Hilary H. , Paus Aage , Svenndse J. I. , Alm Torbjørn , Mangerud J. , Landvik J. Y.
Published: February 2007

A synthesis of the principal environmental changes that are inferred to have occurred in Norway and Svalbard (Fig. 1) during the Late‐glacial period (14‐9 ka BP) is presented. The paper has three sections dealing separately with (I) western Norway, (II) northern Norway and (III) Spitsbergen, Svalbard. The main conditions described include glacial events, sea‐level changes, vegetation history and climatic variations. A summary chart of environmental reconstructions is presented for each of the three areas, each including a curve of temperature reconstructions for the Late‐glacial period. These indicate some significant regional variations in contemporaneous thermal conditions during the Late‐glacial.
A review of the environmental history of Iceland, 13 000‐9000 yr BP
Authors: Ingólfsson Ólafur , Norddahl Hreggvidur
Published: February 2007

A synthesis of the main environmental changes that are interpreted to have occurred in Iceland during the period 13‐9 ka BP is presented. Most of the evidence available relates to variations in the position of ice margins, although some limited information on vegetation history and soil stability is also referred to. Only qualitative and limited climatic inferences can be made for this period because of the lack of detailed evidence. A summary curve of the relative extent of ice cover is presented.
Wisconsinan Late‐glacial environmental chage in New Brunswick: A regional synthesis
Authors: Cwynar Les C. , Levesque André J. , Mayle Francis E. , Walker Ian
Published: February 2007

A synthesis is presented of the history of deglaciation, vegetation cover and climate in New Brunswick, Canada, during that part of the Wisconsinan Late‐glacial period (12‐9 ka BP) for which detailed records exist. Curves of inferred temperature variations in the region during this period are presented based upon qualitative interpretations of plant records and quantitative estimates based upon fossil chironomid assemblages.
Wisconsinan Late‐glacial environmental chage in Québec: A regional synthesis
Authors: Richard P. J. H.
Published: February 2007

A synthesis is presented of the evidence for regional deglaciation, lake sediment stratigraphy, vegetation history and climatic variations in Québec during that part of the Wisconsinan Late‐glacial (12.5‐9 ka BP) for which detailed records exist. Lake sediment data for all or part of this period are available from more than 125 lakes or bogs in the region. The information available indicates strong regional differentiation in climatic conditions, probably due to local effects close to the edge of the retreating Late Wisconsinan ice sheet. The Younger Dryas cooling is not evident in the data from Québec, but there appears to have been a strong climatic reversal during the early Holocene. Summary charts are presented of deglaciation and vegetation patterns in the region, but only qualitative assessments can be made of temperature variations.
Wisconsinan Late‐glacial environmental change on the southeast Baffin shelf, southeast Baffin Island and northern Labrador
Authors: Andrews J. T.
Published: February 2007

The importance of the Baffin‐Labrador region is explained in terms of the channelling through this area of the mass flux of meltwater from the Laurentide Ice Sheet and the probable effects of this on the thermohaline circulation of the North Atlantic. The chronology of glaciation and deglaciation in the region is summarised. Reference is made to recent marine records from the Baffin Shelf. Isotopic changes recorded in foraminiferal assemblages obtained from marine sediments in the Baffin Shelf‐Labrador Sea area indicate the timing and possible magnitude of meltwater fluxes during the period 14.0‐11.0 ka BP.
Climatic changes in areas adjacent to the North Atlantic during the last glacial‐interglacial transition (14‐9 ka BP): A contribution to IGCP‐253
Authors: Lowe J. John , Ammann B. , Birks H. H. , Björck S. , Coope G. R. , Cwynar L. , de Beaulieu J.‐L. , Mott R. J. , Peteet D. M. , Walker M. J. C.
Published: February 2007

This paper presents a summary of the evidence for climatic changes during the last glacial‐interglacial transition (14‐9 ka BP) in land areas adjacent to the North Atlantic. It is a synthesis of the results of the 12 regional summaries compiled by contributors to the North Atlantic Seaboard Programme of IGCP‐253 that are published separately in this issue of Journal of Quaternary Science. Eighteen palaeotemperature curves are compared and arranged in three transects, one from southern Europe to Spitsbergen, a second from Ireland to Poland, and the third from southern New England to the Labrador‐Baffin Shelf area. Ten maps are presented that summarise the synoptic climatic conditions of the region in 500‐year time periods. The purpose of the exercise is to examine the extent to which any emerging patterns support the Ruddiman and Mclntyre model of large‐scale shifts in the position of the oceanice Polar Front during the last glacial‐interglacial transition. Some broad agreement emerges, although the influence of oceanic changes is diminished in areas that lay in close proximity to the Laurentide and Fennoscandian ice sheets. Attention is drawn to limitations in the compilations and to the potential for improved models in the future.
Plio‐Pleistocene palaeoceanography of the tropical Indian Ocean (ODP Hole 709C): Radiolarian and CaCO3 evidence
Authors: Haslett Simon K. , Funnell Brian M. , Dunn Claire L. , Bloxham Kathryn S.
Published: February 2007

Sediments spanning the Olduvai subchron (1.79–1.95 Ma) of ODP Hole 709C in the tropical Indian Ocean were sampled at 5‐cm intervals. High‐resolution quantitative radiolarian and CaCO3% data have been used as proxies in interpreting palaeoceanographical conditions, an a comparison made with previously obtained oxygen isotope data. Radiolarian data were subjected to principal components analysis, resulting in four varimax factors. Factor 1 accounted for the greatest variation and comprised well‐know warm‐water and cold‐water taxa, with high +ve and ‐ ve scores respectively, which were used in the construction of a temperature index. Results indicate a tripartite temporal division of Olduvai palaeoceanography. In the early Olduvai, prior to 1.895 Ma, and the late Olduvai, approximating the Plio‐Pleistocene boundary at 1.81 Ma, divergence‐driven equatorial upwelling and high‐productivity coincide with isotope‐defined ‘interglacials’, and with generally low CaCO3%. However, during the mid‐Olduvai, upwelling, productivity and sedimentation rates were all reduced. These changes in palaeoceanography are thought to be linked directly to eccentricity modulated variations in the precession of the Earth's orbit. The early and late Olduvai coincide with periods of minimum eccentricity, when precessional reinforcemnet of the southwest monsoon is weakest, coastal upwelling along the Oman margin is reduced, and zonal wind‐driven equatorial divergence upwelling is increased. The mid‐Olduvai, however, corresponds with an eccentricity maximum, during which monsoonal activity is stronger and equatorial divergence upwelling weak.
Sedimentation and Iithostratigraphy of the North Sea Drift and Lowestoft Till Formations in the Coastal cliffs of northeast Norfolk, England
Authors: Lunkka Juha Pekka
Published: February 2007

The most complete terrestrial sequence of Anglian (Elsterian) glacial sediments in western Europe was investigated in northeast Norfolk, England in order to reconstruct the evolution of the contemporary palaeoenvironments. Lithostratigraphically the glacial sediments in the northeast Norfolk coastal cliffs can be divided into the Northn Sea Drift and Lowestoft Till Formations. Three of the diamicton members of the North Sea Drift Formation (Happisburgh, Walcott and Cromer Diamictons) were deposited as lodgement and/or subglacial deformation till by grounded ice, but one, the Mundesley Diamicton, is waterlain and was deposited in an extensive glacial lake. Sands and fine sediments interbedded between the diamictons represent deltaic sands and glaciolacustrine sediments derived not solely from the melting ice in the north but also from extra‐marginal rivers in the south. The Lowestoft Till Formation is not well preserved in the cliffs but includes lodgement till (Marly Drift till) and, most probably, associated meltwater deposits. Extensive glaciotectonism in the northern part of the area is shown to relate to oscillating ice that deposited the Cromer Diamicton and also partially to the ice sheet that deposited the Marly Drift till. It is suggested that during the Anglian Stage the present day northeast Norfolk coast was situated on the northwestern margin of an extensive glaciolacustrine basin. This basin was dammed by the Scandinavian ice sheet in the north and northeast. Because the grounding line of this ice sheet oscillated in space and time, part of the North Sea Drift diamictons were deposited directly by this ice. However, during ice retreat phases glaciolacustrine deposition comprised waterlain diamicton, sands and fines. When the Scandinavian ice sheet was situated in northernmost Norfolk, the British ice sheet (responsible for depositing the Marly Drift facies) entered the area from the west. This ice sheet partially deformed the North Sea Drift Formation sediments in the northern part of the area but not in the south, where the British ice sheet apparently terminated in water. The interplay of these two ice sheets on the northern and western margins of the glacial lake is thought to be the major determining factor for the accumulation of thick glacial deposits in this area during the Anglian glaciation.
Glacial dynamics and transport of debris during the final phases of the Weichselian Glaciation, southwest Skåne, Sweden
Authors: Persson Kärstin Malmberg , Lagerlund Erik
Published: February 2007

Late Weichselian glacial sediments were studied in three sections west of Lund, southwest Sweden. The lowermost sedimentary unit is a lodgement till containing rock fragments derived from the northeast‐east. Fabric analyses indicate successive ice flow directions: from the northeast, east‐northeast, south‐southeast and then east. The last active ice movement in the area was from the east. Above the lodgement till are deglaciation sediments consisting of meltout till, flow till and glaciofluvial sand and gravel deposited in a subaerial stagnant‐ice environment. The uppermost unit consists of glaciolacustrine clay and silt, containing abundant ice‐rafted debris, deposited during a short‐lived transgression phase when stagnant ice was still present in the area. At the westernmost site investigated, the petrographical composition of the deglaciation deposits displays a gradual change, with upwards increasing components of Cretaceous chalky limestone. The presence of this rock type requires a period of glacial transport from the south. This stratigraphy cannot be explained with traditional glaciodynamic models. A possible scenario can, however, be constructed using a previously published model (Lagerlund, 1987) where marginal ice domes in the southwestern Baltic area interact with the main Scandinavian Ice Sheet.
Amino acid diagenesis in the marine bivalve Arctica islandica Linné from northwest European sites: Only time and temperature?
Authors: Sejrup Hans Petter , Haugen John‐Erik
Published: February 2007

Collections of the molluscan species Arctica islandica from seven sites in Norway, Scotland and the North Sea, ranging in age from recent to Early Pleistocene, have been sampled for amino acid analyses. The shells were sampled in profiles through the valves at different distances from the umbo. In the fossil material a general trend of increasing degree of isoleucine (lle) epimerisation and decreasing amino acid concentrations were found going from the inner part of the valve to the outer. Although less pronounced, there is a similar trend from the central part of the valve to the margin. As the concentration of alloisoleucine (alle) remains nearly constant, the observed changes in alle/lle ratios are a result of variations in the amount of isoleucine. The amino acid composition is fairly uniform in recent shells and the observed gradients are established in mid‐Holocene samples. Therefore, it is suggested that the gradients are established during rapid early degradation of the protein, possibly due to microbiological activity. Differences in alle/lle ratios observed in molluscs from sites of the same age and same thermal history could be explained by differences in the exposure to amino‐acid‐consuming microorganisms during the very early stage of diagenesis.
Palaeontology and taphonomy of Late Quaternary fossil assemblages at Somersham, Cambridgeshire, England, and the problem of reworking
Authors: West Richard G. , Knudsen Karen L. , Penney David N. , Preece Richard. C. , Robinson J. Eric
Published: February 2007

Assemblages of foraminifers, ostracods and molluscs from temperate Ipswichian Stage (last temperate stage) sediments and overlying cold Devensian Stage (last cold stage) sediments at Somersham in the southern Fenland of Cambridgeshire have been analysed. The Ipswichian sediments contain faunas consistent with temperate brackish water conditions under tidal influence. The Devensian assemblages were recovered from a series of sands and gravels laterally accreting in a channel cutting into Ipswichian sediments. In contrast to the Ipswichian faunas, the faunas of particular Devensian samples show a complex mixture of temperate freshwater, brackish and marine taxa. The molluscs are mainly freshwater, with few land snails; they occur together with foraminifers and ostracods. Freshwater, brackish water and marine ostracods are present with foraminifers. A sample of Devensian fine laminated sediment in the channel was analysed for pollen; only abundant pre‐Quaternary spores were present, with abundant foraminifers in the same sample. The taphonomy of the assemblages and the difficulties of their interpretation in environmental terms are discussed. The importance of taphonomy in assessing environments, climate, range of taxa and dating is stressed.
Late Quaternary environmental change and human impact around Lake Bolac, western Victoria, Australia
Authors: Crowley Gabriel M. , Kershaw A. Peter
Published: February 2007

The late Quaternary history of the Lake Bolac region is reconstructed from sedimentary and pollen analysis of lake and swamp sequences and is supported by archaeological remains from lunette sediments. Freshwater deposits recovered from lake Turangmoroke appear to date from the last glacial period, when the vegetation was composed of herbfield and grassland. Subsequent dry conditions at the end of the Pleistocene caused the deflation of some accumulated sediments. On refilling, the lake had become saline. As moisture availability increased, casuarina woodland, dominated by Allocasuarina verticillata, became the regional vegetation cover. Domination by casuarina ended ca. 8000–7000 yr BP, probably as a result of rising saline ground‐water tables. Casuarinas were replaced to some degree by eucalypts, augmented by the development of a riverine Eucalyptus camaldulensis woodland. Swamp deposition commenced in the channel of neighbouring Fiery Creek at ca. 4000 yr BP, most likely as the result of a reduction in stream flow with decreased precipitation. Despite suggestions of significant impact on the vegetation by Aboriginal people from other sites in southeastern Australia, there is no evidence of any alteration here from periods of occupation dated to around 13000 yr BP and after 3500 yr BP. The period of European occupation, though, is marked by significant changes in fire patterns, reduced tree cover, loss of floristic diversity, increased erosion rates and salinity levels, and decreased water levels.
Drumlin formation in Southern Anglesey and Arvon, Northwest Wales
Authors: Hart Jane K.
Published: February 2007

This is a study of Late Devensian drumlins formed in southern Anglesey and Arvon, northwest Wales. This area was affected by ice sheet coalescence when the Welsh ice sheet met with the lrish Sea ice sheet, and drumlins were formed once the two had coalesced. It is suggested that the drumlins were the result of net subglacial soft‐bed erosion, and that they represent more resistant cores within the subglacial deforming layer. The drumlins have either gravel or till cores, and where the core was deformable, large‐scale compressive glaciotectonic structures were seen (e.g. Dinas Dinlle) with local subglacial compression of –59%. Where the cores were more resistant (e.g. Lleiniog) these were not deformed but remained as more competent masses within the deforming layer. It is suggested that the less competent material flowed around the cores, some remaining as a thin carapace, but most of the material being removed down glacier, leaving the drumlins as erosional remnants.

In northwest Wales there is a multi‐till sequence that traditionally has been interpreted as having been deposited as the result of separate ice‐sheet advances and retreats. However, in this study, it is suggested that the different tills were deposited as the result of ice‐sheet coalescence, and that sites such as Dinas Dinlle do not show evidence of a major readvance in the retreat of the Devensian ice, but are indicative of continuously changing conditions within the subglacial deforming bed.
Holocene landscape change at Carn Dubh, near Pitlochry, Perthshire, Scotland
Authors: Tipping Richard
Published: February 2007

Detailed palynological analyses, including pollen preservation and charcoal counts, and sedimentological analyses (loss‐on‐ignition, percentage dry weight, dry bulk density and humification), supported by 15 14C dates, were applied to a small upland (350 m OD) peat basin near Pitlochry, east‐central Grampians, Scotland. Stratigraphical analyses and radiocarbon dating were also undertaken on the valley peat surrounding the basin.

Organic sediment began to accumulate in the basin and on the valley floor at ca. 9800 yr BP. ‘Recurrence surfaces’ within the valley floor peat correlate with the end of a trend to increased aridity in the deep basin, from 8900 to 8500 yr BP. Pine may have colonised the hills, with birch, before the migration of hazel at 9150 yr BP. From around 8000 yr BP elm grew on the base‐rich soils. Alder may have been present by 7000 yr BP but it did not expand until immediately after the first major anthropogenic disturbance, at 4800 yr BP.

Above 8000 yr BP silt was commonly deposited in the basin by streams, but several phases of exceptionally intense inwashing are identified, and at least two of these correlate with periods of increased precipitation.

Grazing pressure during the elm decline marks the beginning of a long history of generally low intensity pastoralism, interspersed with periods of heightened anthropogenic activity.
Marine evidence for climatic instability during the last interglacial in shelf records from northwest Europe
Authors: Seidenkrantz Marit‐Solveig , Kristensen Peter , Knudsen Karen Luise
Published: February 2007

Data from the Greenland ice sheet and continental records from Europe have indicated climatic fluctuations during the last interglacial (Eemian: Oxygen Isotope Substage 5e). Similar fluctuations have not, however, been documented previously from marine environments. Here, we show the existence of two cold events during substage 5e in two marine, benthic foraminiferal, shelf records from northwest Europe and suggest that these cooling events are a result of fluctuations in the strength of the North Atlantic surface‐water circulation.
Pollen analyses off Senegal: Evolution of the coastal palaeoenvironment during the last deglaciation
Authors: Lezine Anne‐Marie , Turon Jean‐Louis , Buchet Guillaume
Published: February 2007

Pollen and dinoflagellate cysts from marine sediments in core A180‐48 (15°19′N, 18°06′W; 2450 m water depth; 530 cm length) are used to reconstruct palaeoenvironmental conditions of nearshore tropical west Africa during the last deglaciation. High concentrations and influxes of pollen and dinoflagellate cysts between 11 000 and 10 000 yr BP are interpreted as reflecting an increase in continental trade‐wind circulation and related coastal upwelling at 15°N latitude. The sea‐surface temperature difference between glacial and interglacial times was not as strong as previously suggested. Together with local (fresh) ground‐water input, this smaller temperature difference may explain the persistence of the Rhizophora mangrove and Guinean gallery forests near the shore until their massive extension during the early Holocene humid maximum around 9500 yr BP. Pollen data from the core are compared with data from Rosilda N110‐Z, from the continental shelf at the same latitude.
Palaeoecology of two lake basins from Disko, West Greenland
Authors: Bennike Ole
Published: February 2007

The macrofossils, lithology and chronology of two lake basins on Disko in central West Greenland have been investigated. Both lakes were isolated from the sea in the mid‐Holocene as a result of relative land uplift. A marine‐brackish‐limnic sequence was recovered from the Qivittut Lake. The marine fauna is unusually diverse, whereas the brackish water fauna consists only of few species. Immediately after isolation the lake passed through a short‐lived eutrophic phase, after which stable, mesotrophic conditions were established. From the second lake basin, the Fortunebay Lake, only limnic sediments were recovered. This lake record demonstrates that rather stable conditions have persisted since mid‐Holocene times. Both lakes show anomalously high accumulation rates.