bluuebunny/crossref_metadata_2025 huggingface dataset:
Tephra geochemistry: a comment on Hunt and Hill
Authors: Bennett K.D.
Published: November 2007

Hunt and Hill's (1993) discussion of tephra geochemistry restates earlier INQUA recommendations, makes unrealistic sugges tions for data presentation, and includes severe criticism of the earlier results of other researchers by judging data retrospectively against a set of guidelines that are not universally agreed. Other deficiencies within the area of British and Irish tephra analysis are identified, including a lack of electron probe centres, and a poor publication record for the location and age of tephras in the British Isles and for features of tephras that enable discrimination between different layers. It is suggested that a more positive approach for tephrochro nologists would lie in remedying these deficiencies, and setting standards by example rather than by negative criticism.
Peat development, sand cones and palaeohydrogeology of a spring-fed mire in East Yorkshire, UK
Authors: Younger P.L. , McHugh M.
Published: November 2007

An archaeological dig near Beverley, East Yorkshire, UK, revealed humified peat enclosing conical and cylindrical sand bodies ('sand cones'), which contained Romano-British greyware. Such sand cones have not been previously described in the literature. Below the peat, upper and lower diamict units (previously classified as Holocene alluvium) were reclassified as late Devensian lodgement till and pre-late Devensian chalky head (gelifluction deposits) respectively. Enigmatic buried timbers, dated dendrochronologically to 5840 BP, were found partially buried within the till. Micromorphological evidence shows that the peat is autochthonous. The sand cones are remains of former spring orifices, which served as foci for groundwater discharge from the regional East Yorkshire chalk aquifer (which underlies the chalk-head deposits in hydraulic continuity). As a corollary, it is suggested that the buried timbers subsided into the till penecontemporaneously with the death of the tree, when an early period of vigorous groundwater discharge led to the temporary establishment of quicksand conditions. Peat accumulation and humification were intimately linked to variations in spring flows. Radiocarbon dates help to relate these variations to regional palaeohydrogeology, in particular to Holocene water-table fluctuations, which reflect changes in recharge rates (a function of climatic change) and sea level.
Evaluation of luminescence-dating procedures applied to late-Holocene colluvium near St Paul's Mission, Natal, South Africa
Authors: Wintle A.G. , Li S.H. , Botha G.A. , Vogel J.C.
Published: November 2007

Colluvial deposits provide an interesting challenge for luminescence-dating techniques because of the short and varied light-exposure histories of the grains prior to deposition. Results of thermoluminescence (TL) and infrared stimulated luminescence (IRSL) measurements are presented for two stacked colluvial deposits from Natal. A radiocarbon date for bulk organic matter in the A horizon of the soil formed within the surface of the lower unit provides a means of assessing the suitability of various luminescence procedures for such material. The overlying colluvium contains grains bleached to varying extents, as shown by the range of EDs for the coarse-grain feldspar separate obtained using the single-aliquot IRSL method. For this sample all age estimates (either by IRSL or TL) are too large compared with the radiocarbon age, indicating that even the IRSL signal was not zeroed in all grains before they were buried. The underlying colluvium contains grains bleached more uniformly, resulting in a smaller range in the values of single-aliquot EDs; the agreement of the IRSL age with the radiocarbon age indicates that the IRSL signals of all grains were zeroed prior to deposition. The TL results for this sample suggest that the signals were not totally zeroed, but had experienced considerably more light at deposition than the grains from the overlying unit.
Dates of Holocene Icelandic volcanic eruptions from tephra layers in Irish peats
Authors: Pilcher J.R. , Hall V.A. , McCormac F.G.
Published: November 2007

Tephra from historic and prehistoric eruptions of Oraefajøkull and Hekla, Iceland, have been found in Irish peats. Using a series of stratigraphically related high-precision radiocarbon measure ments, the date of a known-age eruption has been satisfactorily estimated. Based on the same techniques, the calendrical date of the Hekla 4 eruption has been estimated as 2310 ± 20 BC.
Evidence of the Eldgjá (Iceland) eruption in the GISP2 Greenland ice core: relationship to eruption processes and climatic conditions in the tenth century
Authors: Zielinski Gregory A. , Germani Mark S. , Larsen Gudrún , Baillie Michael G.L. , Whitlow Sallie , Twickler Mark S. , Taylor Kendrick
Published: November 2007

Glaciochemical studies and the evaluation of tephra in the GISP2 ice core provide information on the characteristics and potential environmental and climatic effects of the mid- to late AD 930s voluminous fissure eruption of Eldgjá, Iceland. The similarity in the chemical composition of basaltic glass shards found in a section of core dated at AD 938 ± 4 compared to proximal glass from the Eldgjá eruption verifies the presence of Eldgjá debris. A dacitic glass present in the same layer probably originated from Eldgjá as well, in which case Eldgjá was the primary contributor of sulphur-rich aerosols to the atmosphere in the late AD 930s. We cannot completely exclude the possibility that another explosive eruption in the AD 930s produced this dacitic glass. Estimated maximum stratospheric loading is 100 X 1012 g H 2SO4 over a 3-6 year period following the eruption, but loading could be as low as half of that value. A search of historical and proxy records for the late AD 930s to early 940s fail to show a consistent period of climatic cooling, especially considering the lack of an absolute date for the Eldgjá eruption. This inconsistent response is similar to that observed after the equally voluminous AD 1783 fissure eruption of Laki, Iceland, using the same proxy data sets. However, a marked drop in surface temperatures in the Northern Hemisphere follows the Laki eruption.
Calendar-dated, early 'Little Ice Age' glacier advance at Robson Glacier, British Columbia, Canada
Authors: Luckman B.H.
Published: November 2007

Dendrochronological studies at Robson and Bennington Glaciers have provided the first calendar dating of an early 'Little Ice Age' glacier advance in North America. Dates derived from in-situ stumps indicate that Robson Glacier began over-riding forest between c. AD 1142 and 1150 and continued until at least AD 1350. The highest rates of glacier advance (c. 3.8 m yr-1 ) occurred between AD 1214 and 1261 based on a series of kill dates from in-situ stumps. Between c. AD 1142-1214 and 1261-1350 rates were somewhat lower at c. 2-2.5 m yr-1. This glacier advance terminated upvalley of the 'Little Ice Age' maximum position of Robson Glacier and there is no evidence at this site for glacial events between AD 1350 and 1783. However, two smaller glaciers in the Robson area and the main tongue of Small River Glacier have outermost 'Little Ice Age' moraines that date from the first decades of the AD 1700s. All glaciers examined in the Mount Robson area have several well-developed moraines dating from the period \c. AD 1840-1900. At Small River Glacier two vegetated moraines occur 50-100 m beyond the nineteenth-century moraines. These have minimum dendrochronological ages of AD <1550 and <1600 but could be much older features. New sites at and upvalley of the present Robson Glacier snout indicate the glacier also over-rode forest areas between 3100-3300 and 3400-3700 14C years BP.
Topogenous peat development and late- Flandrian vegetation history at a site in upland South Wales
Authors: Smith A.G. , Green Carol A.
Published: November 2007

Three radiocarbon-dated pollen diagrams were made from progressively shallower depths on a transect through an upland stream-valley bog in South Wales. The peat ranges in age from approximately 4000 to 2500 cal. BP. Comparison of the pollen diagrams shows that local vegetational changes can be distinguished and different histories emerge at sites only tens of metres apart. Despite this, general trends can be distinguished. There is evidence of increased soil moisture and the growth of willows as organic material began to accumulate in the central part of the valley around 4000 cal. BP. Reduction of trees accompanied true blanket peat inception, perhaps around 3800 cal. BP. At the margin, however, tree reduction preceded the peat formation which began at least 1000 years later. The process was here accompanied by podsolization. Some woodland remained near the site until the end of the Bronze Age. There was an increase of soil moisture during, or close to the end of, Romano-British times. An increase of healthy ground cover occurred around 350-700 cal. BP but there was a reversion to more grassy conditions in relatively recent times. There is little evidence of human impacts. The vegetational and soil changes at the site appear to be attributable principally to climatic deterioration or local hydrological changes.
Holocene evolution of a lowland Scottish landscape: Kirkpatrick Fleming. Part III, fluvial history
Authors: Tipping Richard
Published: November 2007

Mapping and radiocarbon dating of fluvial terrace fragments along the greater length of the Kirtle Water resulted in the definition of five major terrace surfaces. Correlations with proxy records of climate change (Part I) and anthropogenic activity (Part II) are made to understand causal mechanisms in fluvial behaviour. The limitations of such correlations are emphasized. The highest terrace (Kirtle I) is thought to be of Devensian Lateglacial age. The remaining four are of Holocene age. An early Holocene gravel aggradation (Kirtle II) may have been sustained from c. 7250 14C years BC until close to c. 455 cal. BC. The establishment of Alnus on floodplains may have led to channel stability. Incision after c. 3250 cal. BC may have been due to greater discharges at a time of deteriorating climate. Terrace Kirtle III is undated. Prior to aggradation of Terrace Kirtle IV, beginning at around cal. AD 300, a period of lowered fluvial activity and floodplain stability is recorded from c. 850 cal. BC. Anthropogenic activity is thought to be responsible for the diachronous initiation of aggradation of Terrace Kirtle IV. Terrace Kirtle V is late historic in age, but the cause cannot be readily isolated.
Relationship of stomatal density and index of Salix cinerea to atmospheric carbon dioxide concentrations in the Holocene
Authors: McElwain J. , Mitchell F.J.G. , Jones M.B.
Published: November 2007

The impact of different concentrations of ambient CO2 on the stomatal density and index of Salix cinerea are investigated. Fossil leaves (AMS dated 9190 BP) and present-day material from the same site in south west Ireland are compared with nineteenth-century herbarium material from Ireland. Techniques for obtaining reliable counts of stomata and epidermal cells from hairy leaves with sunken stomata are reported. Stomatal density and index were both found to be inversely related to CO2 concentration. The data also demonstrate the higher intra-specific variability of stomatal density over stomatal index. Analysis of the data indicates that similar investigations should be confined to single sites.
Dinoflagellate cysts and Holocene oceanography of the northeastern Atlantic Ocean
Authors: Harland Rex , Howe John A.
Published: November 2007

Dinoflagellate cyst analysis of two sediment cores, taken on the continental slope off the western coast of Scotland, has revealed new detail and complexity in the oceanography of the Holocene. Changes in the dinoflagellate cyst assemblages suggest at least three fluctuations in the strength or disposition of the North Atlantic Current over the last 10 Ka together with a consequent change in the oceanographic regime of the northeastern Atlantic. These changes, based on comparison to well- constrained data from the Arctic, include the first influx of the North Atlantic Current at about 10 Ka, together with some change in oceanography at between 8 and 6 Ka and between 4 and 2 Ka. These oceanographic changes are based upon fluctuations in the numbers of dinoflagellate cysts per gram of sediment and by their relative proportions. Dinoflagellate cysts have, therefore, a significant role to play in reconstructing the complex history of Holocene environmental change.
Sedimentary records of recent environmental change in Lake Baikal, Siberia
Authors: Flower R.J. , Mackay A.W. , Rose N.L. , Boyle J.L. , Dearing J.A. , Appleby P.G. , Kuzmina A.E. , Granina L.Z.
Published: November 2007

Lake Baikal is the world's largest freshwater lake and is internationally famous for its rich and largely endemic biota. Concern about this unique ecosystem has grown since the late 1970s but whether recent biological changes result from natural fluctuations or pollution is unclear. One way of discriminating between these processes is to examine records of recent change in radiometrically dated deep-water sediment cores. Here we use high-resolution diatom analysis of one core to show that abundances have not changed significantly over recent decades. By contrast, we demonstrate that the lake is contaminated by atmospheric pollutants and has experienced a small qualitative change in soil derived magnetic minerals. Sedimentary lead concentrations show an increasing trend in the c. 150-year core sequence and spheroidal carbonaceous particles (SCPs) contaminate post-1930 sediment. Although we provide no evidence that twentieth-century pollution has affected the endemic planktonic diatoms in the central western region of southern Lake Baikal, longer trends in species abundances could be related to naturally occurring climatic cycles or to global warming.
Dating of recent lake sediments in the United Kingdom and Ireland using spheroidal carbonaceous particle (SCP) concentration profiles
Authors: Rose N.L. , Harlock S. , Appleby P.G. , Battarbee R.W.
Published: November 2007

Spheroidal carbonaceous particles (SCPs) produced from fossil-fuel combustion are found in lake sediments and provide a historical record of atmospheric pollutant deposition. The sediment record of these particles is remarkably consistent and the main features are now seen throughout Europe and beyond. Once the SCP record from a region has been established using accurately dated cores, SCP profiles can be used to determine dates at other sites in the region. This technique was developed in Sweden but until recently has had limited use in the UK and Ireland as the most useful dating feature, the subsurface peak, was not present in all cores. In recent cores this can now almost always be observed. Dating features for UK and Irish cores are found to differ slightly between regions. The potential exists for extra dates to be allocated to a profile by using characterisation of SCP surfaces to determine changes in fuel-type use. Dates could then be allocated to these changes using documentary sources to derive combustion histories. In future years, SCP dating will become increasingly valuable especially for mid- to late-nineteenth-century sediments as continual decay renders210 Pb progressively less useful for this time interval.
Vegetational response to Holocene climatic change: pollen and palaeolimnological data from the Middle Atlas, Morocco
Authors: Lamb Henry F. , van der Kaars Sander
Published: November 2007

Pollen data from a radiocarbon-dated lake-sediment core from the Middle Atlas of Morocco show that forests of evergreen and winter-deciduous oaks (Quercus rotundifolia, Q. canariensis), present from the start of the Holocene, were invaded at 6200 BP by Cedrus atlantica in low numbers. Two thousand years later, after a short period characterized by higher deciduous oak frequency, Cedrus increased to its present abundance. These changes may have been in response to increasing effective moisture as summer temperatures decreased with declining northern-hemisphere seasonality, under the influence of precessional forcing. Palaeolimnological data from the same core show that the lake level fell sharply in five 200-400 yr-long arid intervals, but the pollen data show little or no evidence of a vegetational response. This suggests that summer (growing-season) rainfall remained adequate during the dry intervals, whereas depletion of the groundwater aquifer was the result of reduced winter precipitation. Anthropogenic exploitation since c. 1300 BP has had a greater effect on the forest ecosystem than any of the Holocene arid intervals.
The Holocene development of a debris slope in subarctic Québec, Canada
Authors: Marion Joëlle , Filion Louise , Hétu Bernard
Published: November 2007

The development of a debris-covered slope in subarctic Québec was reconstructed in relation to vegetation dynamics, fire history and local permafrost evolution. The slope consisted of a low- elevation rockwall and a rockwall-derived debris veneer overlying a sandy till deposit reworked by gelifluction. The sedimentological and stratigraphical data along with radiocarbon dating and den droecological data indicated that: (1) the period around 5050 BP corresponded to the initial establishment of the forest cover probably after paraglacial rockfall activity following deglaciation; (2) it was followed by a period of stability until c. 3200-3000 BP when gelifluction occurred; (3) the period between c. 3000 BP and 900 BP was one of relative stability; until (4) a series of fires after 900 BP initiated a period of destabilization by mass movements and surficial weathering processes; (5) local permafrost formed during the last few centuries, especially under the forest fringe where Sphagnum peat developed. Results from this study indicate a strong connection between fire, slope destabilization and the intensification of geomorphological slope processes during the last millennium at the study site.
Origin, chronology and climatological significance of annual-moraine ridges at Myrdalsjökull, Iceland
Authors: Krüger Johannes
Published: November 2007

Minor, transverse moraine ridges have formed annually at the retreating north margin of Myrdalsjökull, 550-600 m a.s.l., in south Iceland during the period 1928-1981. They are composed of slabs of clast-paved lodgement till and their formation at the glacier edge results from subglacial freezing-on of sediment slabs during winter and the annual cycle of ice-front activity. This type of annual-moraine ridge is likely to be characteristic of retreating temperate glaciers where the glacier toe is thin and winters are cold. The speed of glacier retreat is finely balanced with changes in mean summer temperature suggesting that the short-term ice-front fluctuations are climatically induced and not a result of surge activity.
Carbon and oxygen isotope variations among lacustrine ostracods: implications for palaeoclimatic studies
Authors: Heaton T.H.E. , Holmes J.A. , Bridgwater N.D.
Published: November 2007

Large ranges of 13C/12C and 18O/ 16O ratios are found among modem ostracods from lakes in Jamaica and Mexico. If their calcite carapaces grew in isotopic equilibrium with the lake water, then the main period of carapace formation was probably in the cooler and/or wetter months. Differences in δ13C and δ18 O values between ostracods from different sites relate to spatial variations in the composition of the lake water, and differences between species at the same site probably reflect differences in organic photosynthesis or decay among the micro-habitats occupied by the species. There nevertheless remain significant variations in both δ13C and δ18O among modern valves of the same species at the same site; a consequence of the temporal and spatial variation in lake water and the fact that ostracods form their carapace over a short period. Individual valves from a 1-cm section of a sediment core show that the isotopic effects of changes in the rainfall versus evaporation status of a lake over a period of c. 102 years can be of a similar magnitude to changes recorded by bulk, fine-grained carbonate throughout the late Quaternary. These findings emphasize the need for caution when using isotopic data for single ostracod valves in palaeoclimatic studies.
Late Younger Dryas to Holocene palaeoenvironments of the southern Kattegat, Scandinavia
Authors: Conradsen Keld
Published: November 2007

Palaeoenvironmental changes since the late Younger Dryas are reconstructed in the southern Kattegat (Scandinavia) and provide a basis for correlating the whole of the North Sea-Skagerrak- Kattegat-Baltic region. The foraminiferal content of seven piston and three vibrocores were analysed. Radiocarbon dates were obtained from four of the cores. Relatively warm water masses occurred in the shallow areas of the Kattegat during the late Younger Dryas and early Preboreal, while cold, arctic/ subarctic water masses occurred in deeper parts of the Kattegat and Skagerrak. Full interglacial temperature conditions developed in the southern Kattegat at 9600 BP. A sea-level rise is recorded at 9600-8200 BP, a period during which the Skagerrak-Kattegat area experienced a gradual warming. A change in sedimentological and environmental conditions occurred in the southern Kattegat at around 8000 BP, reflecting the opening of a connection to the Baltic and corresponding hydrographic changes. The modem general circulation pattern of the area was established after this event. A further rise in sea level is recorded after 8000 BP. A mid-Holocene alteration in hydrographic and sedimentation pattern in the area is marked by the reappearance of Nonionellina labradorica in the southern Kattegat. This alteration, previously dated to 4000 BP, is redated to 5500 BP and is interpreted as reflecting the well- defined late-Atlantic cooling of the North Atlantic region resulting in changed inflow/outflow pattern of water masses in the Kattegat.
High-resolution stable isotope analysis of tree rings: implications of 'microdendroclimatology' for palaeoenvironmental research
Authors: Loader N.J. , Switsur V.R. , Field E.M.
Published: November 2007

High-resolution stable isotope analyses were carried out on a sample of oak (Quercus petraea) from Cultra, Co Down, UK. A sampling strategy of unparallelled resolution was adopted in an attempt to reconstruct short-term climatic changes during the growing season. The results display a surprising clarity of signal and suggest a significant relationship between δ 13C and relative humidity and, to a lesser extent, temperature. This preliminary study proposes possible reasons for the isotopic profile observed and highlights the perceived future value of intra-ring isotope studies ('microdendroclimatology').
Late-Holocene glacier variations in the frontal and inner ranges of the Tian Shan, central Asia
Authors: Savoskul O.S. , Solomina O.N.
Published: November 2007

Evidence for the timing and extent of late-Holocene glacial advances in the Tian Shan mountains, central Asia, is based on lichenometric and radiocarbon dating of end-moraines. Three phases of glacial advance occurred at 1700-2100 and 1100-1300 lichenometric (L) years ago, and then during the 'Little Ice Age', 150- 700 (L) years ago. Differences in the pattern of glacier variations between the northwestern frontal and inner areas of the Tian Shan are reflected in the equilibrium line altitude (ELA) depression of 23 glaciers studied at nine selected sites. The peripheral glaciers appear to have been significantly more extensive during late- Holocene advances than the glaciers of the inner areas. This difference seems to be explained by regional differences in humidification: in the northwestern periphery of the Tian Shan, the cold periods of the late Holocene were more humid than the warm period of the mid-Holocene; whereas, in the inner areas, the pattern of climate changes was the opposite (a warm and humid mid-Holocene was followed by a cold and arid late Holocene).
Reflected-light image analysis of conifer tree rings for reconstructing climate
Authors: Sheppard Paul R. , Graumlich Lisa J. , Conkey Laura E.
Published: November 2007

We use reflected-light image analysis to measure brightness of conifer rings, and we use brightness as an alternative to density for reconstructing climate. Using densitometry and image analysis, we measured cores from red spruce ( Picea rubens Sarg.) growing at Elephant Mountain, Maine, and then compared statistical characteristics of density and brightness and climate-tree growth models using density or brightness. Auto- correlational and cross-correlational statistics of density and brightness do not differ substantially, and late wood density and brightness both correlate with April-May average temperature, which both tree-ring variables reconstruct equally well. April-May temperature was highly variable during most of the nineteenth century and was below average during the AD 1830s, 1870s and late 1880s. When done carefully, reflected-light image analysis can substitute for X-ray densitometry for measuring tree rings to reconstruct climate of the latest Holo cene.
Lake-level and groundwater-level changes in the Lake Gosciąż area, Poland: palaeoclimatic implications
Authors: Starkel Leszek , Pazdur Anna , Pazdur Mieczysław F. , Wicik Bogumil , Wieckowski Kazimierz
Published: November 2007

Lake Gosciąz is located in the zone of the maximum extent of the last ice sheet. Distinct lake terraces and deposits related to the lateglacial transgression do not exist. Detailed examination of annually laminated sediments and landforms revealed three phases of higher water level and storage, represented by shore features, by littoral, deltaic and bog deposits, and by higher rates of lacustrine deposition in the pelagic zone. Holocene lake transgressions at c. 8.4-7.7 ka, 2.5-2.3 ka, and less distinct at 5-4 ka BP coincide with phases of higher flood frequency in Poland and glacial advances in the Alps. Because of sedimentation, isolation from groundwaters, encroachment by peatland and drainage of the lake, lake volume during the last 12 ka diminished by as much as 70%, and current water-level fluctuations of about 1-2 m can change water storage by 20-25%.
Estimates of low frequency natural variabilit in near-surface air temperature
Authors: Barnett T.P. , Santer B.D. , Jones P.D. , Bradley R.S. , Briffa K.R.
Published: November 2007

Estimates of the spectrum of natural variability are critical to the problem of detecting an anthropo genic signal in global climate observations. Without such information it is impossible to say that current climate change is different or unique from changes that have happened in the past and, therefore, potentially due to man-induced causes. We have estimated the spectrum of natural variability from a globally distributed set of palaeo-temperature proxies and compared it with comparable estimates from two long control integrations of coupled general circulation models - the type used to predict anthropogenic change due to greenhouse gases. None of the three estimates of the natural variability spectrum agree with each other on the low-frequency, near-global time/space scales. Until this dichotomy is resolved, it will be hard to say, with confidence, that an anthropogenic climate signal has or has not been detected.
Farming and forest dynamics in an agriculturally marginal area of southern Sweden, 5000 BC to present: a palynological study of Lake Avegöl in the Småland Uplands
Authors: Lageras Per
Published: November 2007

The study focuses on the environmental history of the higher parts of the Småland Uplands, southern Sweden. Pollen analysis was conducted on gyttja from the small lake Avegöl, and an absolute chronology established based on AMS dates of terrestrial plant macrofossils. The area has been used for grazing from 3900 cal. BC to present, but cultivation of cereals was not introduced until c. 300 cal. BC. There have been two major periods of open landscape, cal. AD 0-500 and cal. AD 1300- c. 1900. The first period was characterized by pastures and shifting cultivation in both till and sand areas. The second period was characterized by pastures, meadows, permanent arable fields and slash-and-burn cultivation, and it was mainly restricted to till areas. Cal. AD 500-1000 was a period of regression and reforestation, when extensive wood pasturage was the only agrarian land-use practised in the area. All dramatic environmental changes, except for the spruce invasion AD 900-1100, are assigned to agricultural land-use, while some slow and gradual changes are explained as the combined effect of land-use and natural processes. The classical Ulmus decline at c. 4000 cal. BC is not detected in the pollen diagram, but there is a significant decline in Ulmus dated to 2800-2600 cal. BC.
Explanations for palaeoecological changes on the northern plains of Guadalcanal, Solomon Islands: the last 3200 years
Authors: Haberle Simon
Published: November 2007

The first records of wetland development and vegetation change from the northern grassland plains of Guadalcanal, Solomon Islands, are presented. Changes in sedimentation and vegetation over the last 3200 years, inferred from pollen and sediment analysis from two inland swamp sites, suggest human activity may have played a role in changing vegetation patterns on the northern plains of Guadalcanal. Catastrophic events, such as tectonic activity, cyclones and volcanic eruptions, have also contributed to disturbance of the forest communities and to erosion. Both sites show evidence for increases in carbonized particles coincident with greater representation of second-growth forest taxa, beginning some time between 3200 and 2100 BP. The change is believed to be associated with early agricultural activity in the inland regions of Guadalcanal, a finding that is in close accordance with the archaeological record. The role of interannual climatic variability in vegetation change is also considered.
A 930-year ring-width chronology from moisture-sensitive white spruce (Picea glauca Moench) in northwestern Canada
Authors: Szeicz Julian M. , MacDonald Glen M.
Published: November 2007

A 930-year tree-ring chronology was constructed from living and subfossil white spruce ( Picea glauca Moench) from the Campbell Dolomite Upland, Northwest Territories, Canada. Response function analy sis using climate data from nearby Inuvik indicates that 69% of the variation in ring widths can be explained by monthly precipitation and temperature. Ring width is most strongly correlated with high precipitation between February and May. There is also a significant negative relationship between ring widths and tempera tures during the previous growing season. Periods of slow radial growth at AD 1820-1855, 1700-1710, 1585- 1610, 1395-1405, 1260-1300 and 1125-1170 are assumed to be associated with times of increased moisture stress. Periods of rapid growth at AD 1925-1940, 1770-1780, 1725-1740, 1510-1560, 1215-1260 and 1185- 1205 likely reflect higher precipitation and/or decreased moisture stress. This chronology is the oldest yet published from northwestern Canada and the first that provides a dendrohydrological record.
On solar forcing of Holocene climate: evidence from Scandinavia
Authors: Karlén Wibjörn , Kuylenstierna Johan
Published: November 2007

The focus of this study is the possible correlation between changes in the climate of Scandinavian and changes in solar irradiation. Reliable information about Holocene climatic change in Sweden and Norway is currently available from two main sources: the 14C dating of pine wood retrieved from above the present pine-tree limit and studies of glacier variations based on proglacial lacustrine sediments and on moraines. The reconstructed alpine tree-limit reveals that summer temperature in general was warmer during the early Holo cene than it was during the late Holocene. Superimposed on this general trend are several fluctuations of a few hundred years' duration. Relatively cold periods with a duration of the order of 300-600 years occurred frequently during the Holocene. In this paper, dates of the major climatic events are compared with an index of solar activity, the so-called δ14C anomalies. For most of the last 9000 years a good correspondence is demonstrated between the timing of cold events in Scandinavia and the timing of major δ14 C anomalies (low solar irradiation). The general Holocene cooling trend is believed to be partly a result of land uplift following deglaciation and partly a result of orbitally forced changes in irradiation. Large fluctuations in Scandinavian summer temperature can be reconciled with the pattern of climatic change presented in several recent studies in the North Atlantic region. A link between these areas could be provided by changes in the production of North Atlantic Deep Water.
Forest disturbance in the central North Island, New Zealand, following the 1850 BP Taupo eruption
Authors: Wilmshurst Janet M. , McGlone Matt S.
Published: November 2007

The 1850 BP Taupo eruption covered c. 30 000 km2 of the central North Island with airfall deposits and c. 20 000 km2 with ignimbrite. This paper reviews pollen and charcoal analyses of lake and peat sediment cores from sites at various distances and directions from the Taupo vent to establish the effects of this eruption on the surrounding forests. Forests within range of the ignimbrite were destroyed, and forests located up to 170 km east of the vent suffered variable degrees of damage from ashfall. Stands of Pteridium esculentum and other seral taxa flourished immediately after the eruption. Fires occurred during the eruption and continued for several decades after. The degree and nature of vegetation disturbance above the Taupo Tephra varied according to the thickness of ashfall, local topographical features and probably the vigour of the forest. Revegetation was complete within 200 years of the eruption, even at sites overwhelmed by the Taupo Ignimbrite. Post-eruption forests were similar to those existing before the Taupo eruption.
Diatoms as an aid in identifying late-Holocene tsunami deposits
Authors: Hemphill-Haley Eileen
Published: November 2007

Diatoms (Bacillariophyta) help identify the onshore deposits of tsunamis from earthquakes on the Cascadia subduction zone along the Pacific coast of Oregon, Washington, and British Columbia, and on faults high in the North American plate in the Puget Sound area of Washington. At the Copalis River, Washington, diatom analyses suggest that a tsunami deposit about 300 calendric years old (300 yr BP) originated from sandy shoals of the lower estuary rather than nearby beaches or coastal dunes. At Cultus Bay and West Point, Washington, well-preserved benthic estuarine diatoms in sand sheets overlying tidal-marsh peat indicate that the deposits came from intertidal or nearshore areas of Puget Sound. On an abruptly uplifted mudflat at the landward end of Hood Canal at Lynch Cove, Washington, tidal-flat diatoms refute the possibility of a terrestrial source for the sand. Diatoms in 300-yr-BP tsunami deposits on the Niawiakum River, Washington, confirm that the sand in these deposits had a marine source, and help to identify the landward extent of tsunami inundation. Diatom assemblages in deposits of the 300 yr BP and AD 1964 tsunamis at Port Alberni, British Columbia, consist of different dominant taxa, but both indicate that the sand units originated from Alberni Inlet. Diatoms add to stratigraphic evidence that tsunamis flooded Bradley Lake, a freshwater lake on the south-central Oregon coast, three times during the past 1700 years. Planktonic marine diatoms only found above 1-70-cm-thick sand layers in otherwise clayey lacustrine sediment imply tsunami inundation.
Fire and climate dynamics in the boreal forest of northern Alberta, Canada, from AD 1850 to 1989
Authors: Larsen C.P.S.
Published: November 2007

The reconstruction of climatically induced changes in the occurrence of forest fires has typically been limited to the period of historical records or to areas where long fire-scar records are available. In this study historical fire records and dendrochronological forest stand-age data are analyzed using life-table methods to reconstruct annual (AD 1950-1989) and semi-decadal (AD 1850-1989) variations in area burned in the 44 870 km2 area of boreal forest in Wood Buffalo National Park (WBNP). Annual area burned between 1950 and 1989 was negatively correlated with mean fire-season precipitation and five annual tree-ring width indices from WBNP, and positively correlated with the fire-season means of temperature and the Seasonal Severity Rating, a Canadian Forest Fire Weather Index. Life-table estimates of semidecadal variations in mean annual per cent area burned were significantly positively correlated with historical records of annual area burned in WBNP between 1950 and 1989 and significantly negatively correlated with five tree-ring width indices from WBNP between 1850 and 1989. Peaks in semidecadal estimates of mean annual per cent area burned appear to be quasi-periodic, with an average interval of 30 to 40 years. Potential causes of these decadal scale variations in fire and climate are discussed. The results of this study indicate that forest age-structure data collected at the landscape scale can be used to infer prehistoric, decadal scale variations in the amount of area burned by forest fires.
Assessing AMS 14C ages of detrital organics from Holocene and late-Pleistocene moraines, east-central Sierra Nevada, California, USA
Authors: Pohl Molly M. , Hajdas Irena , Bonani Georges
Published: November 2007

Obtaining age estimates of moraines which have insufficient carbon for conventional 14C dating may be possible by AMS 14C dating of detrital organic material in the till matrix. Sufficient detrital carbon was available in the till matrix of Holocene and late-Pleistocene moraines of upper Laurel Creek Canyon, east-central Sierra Nevada, California, for AMS 14C measurements. Radiocarbon analysis of till matrix organics from the moraine closest to the headwall, M1, reveals an age of 2875 ± 60 BP (ETH 13550). The next oldest moraine, M2, yields 4450 ± 60 BP (ETH 12810). M3, the oldest moraine in the Bloody Mountain Cirque, yielded organics with a radiocarbon age of 13 600 ± 120 BP (ETH 12812). While results are preliminary, these ages are among the first on till matrix in the Sierra Nevada and are consistent with geomorphic context, other palaeoecologic records in the Sierra Nevada, and palaeolake records in the western United States.
Holocene glacial and climatic variations on Spitsbergen, Svalbard
Authors: Svendsen John Inge , Mangerud Jan
Published: November 2007

Holocene glacial and climatic variations have been inferred from investigations of sediment cores from the proglacial lake Linnévatnet, western Spitsbergen. A low content of glacially derived coal, absence of regular laminations and a slow sedimentation rate in the lower part of the lacustrine sediments indicate that the former glaciers that existed within the catchment area during the last ice age melted quickly away as a result of the Younger Dryas-Holocene warming, and during the next 6000 years there were no glaciers in the valley. Increasing coal content, incipient laminations and rising sedimentation rates indicate that the glacier Linnébreen started to form 4000-5000 years ago, probably as a response to the late-Holocene cooling. The Holocene maximum extent of the glacier occurred during the 'Little Ice Age', starting with a pronounced ice advance in the thirteenth or fourteenth century. A well-dated core from Billefjorden, which is assumed to reflect glacial fluctuations in the inner part of the Isfjorden area, indicates a similar development to that in the valley Linnédalen. No glacial signal was recorded during the early and mid-Holocene. The present tide water glaciers started to form 3000-4000 years ago, with glacial maxima around 500 cal. BC (2400-2500 BP) and during the 'Little Ice Age'.
Investigation of the environmental impact of remote volcanic activity on north Mayo, Ireland, during the mid-Holocene
Authors: Dwyer Rosaleen B. , Mitchell Fraser J.G.
Published: November 2007

Seven layers of microscopic tephra have been detected in ombrotrophic peat from western Ireland. A radiocarbon chronology suggests that two of the tephra layers were deposited around 4000 BP. Pollen, fungal spores and testate amoebae have been analyzed from the peat immediately above and below the tephra layers. These analyses provide information of changes in the landscape surrounding the bog and as well as conditions on the bog surface. Analysis of rates of change in these data has been employed to investigate the relative magnitude of environmental changes at the time of tephra deposition. Tephra deposition occurred at least 100 years after a major decline in Pinus pollen and coincides with fairly stable conditions in the terrestrial environ ment. More significant changes on the bog surface, indicative of wetter conditions, are associated with the timing of tephra deposition.
Roman impact on the environment at Hadrian's Wall: precisely dated pollen analysis from Vindolanda, northern England
Authors: Manning Adrian , Birley Robin , Tipping Richard
Published: November 2007

The results of pollen analyses from two ditch fills of early Roman age from the fort at Vindolanda, close to Hadrian's Wall, are presented. The ditch fills can be closely dated to the periods c. AD 85-92 and c. AD 160-180, and this chronological precision provides insights into the timing of human impacts on the vegetation around this part of Hadrian's Wall which are unobtainable from more conventional radiocarbon dated stratigraphies. The analyses show that anthropogenic woodland clearance occurred before c. AD 85 around Vindolanda. Deforestation may have been by native farmers rather than by Roman troops. Clearance occurred prior to the construction of Hadrian's Wall in the second century AD, and was probably intended to allow an expansion of agricultural land, and in particular pasture for grazing animals. Cereal cultivation was possibly established at Vindolanda in the early to mid-second century AD.
The preparation of testate amoebae (Protozoa: Rhizopoda) samples from peat
Authors: Hendon Dawn , Charman Daniel J.
Published: November 2007

The analysis of testate amoebae (Protozoa: Rhizopoda) in peat is proving to be a useful new quantitat ive technique for assessing hydrological change on peatlands. Preparation experiments were carried out on peat extracted from Coom Rigg Moss, Northumberland, England, in order to assess the impact of different procedures on the concentration and species composition of the faunas. Five replicates of each of six samples were treated by different techniques and the testate amoebae counted together with 200 Lycopodium spores. All preparation procedures suitable for pollen extraction reduce the number of tests recorded by up to 80% and the number of taxa recorded by 60%. KOH digestion did not destroy tests but damaged them, making identification difficult, although it enabled extraction of a higher number of tests. A simple water-based prep aration, with sieving to remove coarse and fine detritus, appears to give the best results and is an improvement on earlier techniques in removing more extraneous material from the samples. Testate amoebae counts from samples prepared for pollen analysis must be viewed with extreme caution and are unrepresentative of the faunal content of the peat in both absolute and relative terms.
The water content of lake sediments and its relationship to other physical parameters: an alpine case study
Authors: Menounos Brian
Published: November 2007

The water content of lake-sediment cores provides informative data for environmental reconstruction. In addition to its usefulness for between-core correlation, significant, nonlinear relationships between water content, organic matter and dry density measurements suggest that high resolution records of organic matter and bulk density in alpine lake sediments can be estimated indirectly. Using water content as a surrogate for bulk density and organic matter, data can be collected at much higher temporal scales than possible with current density samplers. These results lend further credence to empirical relationships between bulk density, water content and organic matter presented elsewhere.
Carbon-isotope variation in Sphagnum from hummock-hollow complexes: implications for Holocene climate reconstruction
Authors: Price Gregory D. , McKenzie Jane E. , Pilcher Jon R. , Hoper Stephen T.
Published: November 2007

The interpretation of isotopic variation in Sphagnum from Holocene peat profiles rests upon several assumptions concerning physiological processes such as variation in CO2 uptake and differences in the isotopic ratio of the source CO2. To examine such variability Sphagnum from hummock-hollow complexes from two raised bogs (Florencecourt and Clara) in Ireland was sampled for carbon isotope analysis. Samples were taken from relatively dry hummock tops, margins and submerged hollows. Carbon isotope measurements on cellulose obtained from the Sphagnum revealed a variation of ∼6‰ across the bog surface. The mean values for Florence court and Clara Bog are -25.6‰ and -26.5‰ (PDB) respectively, which is consistent with the sphagna utilizing C3 photosynthesis to take up atmospheric CO2. The hummock-top species from both sites yielded lighter isotopic values than the hummock-margin species which is consistent with the hummock-top species photosyn thesizing under a lower water content and hence lower external diffusion resistance. A large range of ∂13 C values was recorded for the hollow samples. The heaviest isotopic values result from high external resistance to CO2. In some situations, however, the carbon source contains a proportion of recycled CO2, depleted in 13C, which produces relatively light isotopic values. Such large isotopic variation within the wet hollows may lead to erroneous climatic interpretation.
The International Tree-Ring Data Bank: an enhanced global database serving the global scientific community
Authors: Grissino-Mayer Henri D. , Fritts Harold C.
Published: November 2007

The International Tree-Ring Data Bank (ITRDB) was established in 1974 to serve as a permanent repository for basic tree-ring data (measurements, chronologies, and derived reconstructions) developed and contributed by scientists from around the world. Housed at the World Data Center-A (WDC-A) for Paleoclima tology at the National Geophysical Data Center in Boulder, Colorado, USA, the ITRDB currently contains 3275 tree-ring chronologies and 2804 tree-ring measurement data sets from over 1500 sites, contributed by 139 researchers worldwide. These data sets represent information from over 100 tree and shrub species. As part of the WDC system, the ITRDB makes its holdings freely available to all scientists. The ITRDB is administered by an international Advisory Committee consisting of eight dendrochronologists representing different subdisciplines in the tree-ring sciences. The ITRDB also provides two additional important services: the creation and management of the ITRDB Dendrochronology Forum on the Internet, and development and distribution of a collection of computer programs for tree-ring analyses known as the ITRDB Program Library. Future efforts of the ITRDB will focus on increasing the worldwide coverage of its database holdings, and to make the ITRDB a more visible component in the scientific community.