bluuebunny/crossref_metadata_2025 huggingface dataset:
Climatic changes in the Chalbi Desert, North Kenya
Authors: Nyamweru C. K. , Bowman D.
Published: February 2007

The Chalbi flat, located 60 km outside the rift to the east, forms a moist, salt‐clay encrusted playa which also functions as an inland sink for alluvial fans. Residual lacustrine beds, including freshwater carbonates and travertines, crop out along its higher periphery. Mammalian bones of lacustrine and terrestrial elements, and K/Ar dating of the capping lava suggest a lake or a swamp environment 2–2.5 million years ago. Radiocarbon dating of Melanoides tuberculata and Planorbis and a sediment assemblage composed of clotted micrite, calcareous molds, root marks and stromatolites point to an additional early Holocene Chalbi lake or swamps 11000‐9500 yr BP. The data suggest wet environmental conditions outside the rift, which is consistent with the occurrence of a wet period in the early to middle Holocene in intertropical Africa, but out of phase with the climatic conditions in Sinai and Israel and with the high‐latitude maximum lake levels and glacier advance. These relations have probably been caused by migration of climatic belts.
A provisional map of forest types for the British Isles 5000 years ago
Authors: Bennett Keith David
Published: February 2007

The distributions of seven woodland types, plus unforested areas, are mapped for the British Isles at 5000 BP. The map was compiled using data of modern soil distribution, present‐day ecological preferences of the tree taxa present, and the pollen record.
Lubbock Lake: Late Quaternary cultural and environmental change on the Southern High Plains, USA
Authors: Johnson Eileen , Holliday Vance T.
Published: February 2007

Lubbock Lake (Southern High Plains of Texas) contains a cultural, faunal, and floral record within a virtually complete geological record spanning the past 11 100+ years. More than 88 archaeological occurrences have been excavated from five major stratigraphic units. The Paleoindian record (11 500–6500yr BP) begins with Clovis‐age occupation (ca. 11 100yr BP) found within fluvial deposits (stratum 1). Subsequent Paleoindian occupations are found in lake and marsh sediments (stratum 2). Archaic occupations (8500‐2000yr BP) are contained within aeolian and marsh deposits (strata 3 and 4). Ceramic occupations (2000‐500yr BP) are found on a soil developed in stratum 4, in marsh sediments (strata 4 and 5), and in slopewash and aeolian sediments (stratum 5). The Protohistoric (500‐300yr BP) and Historic (300‐100yr BP) remains are in slopewash, aeolian, and marsh sediments (stratum 5) and associated soils. The Southern High Plains remained a grasslands throughout the last 11 500 years and neither man nor bison abandoned the region. The successive local faunas reflect changing ecosystems under pluvial to arid to more mesic to semiarid conditions. The occupation of Lubbock Lake through time appears to have been by small groups of people for both economic and short‐term residential uses. These hunter‐gatherer peoples underwent adaptive change brought about by climatic stress and alterations to food resources.
The Late Devensian glaciation along the western margin of the Cheshire‐Shroshire Iowland
Authors: Thomas Geoffrey S. P.
Published: February 2007

The glacial succession in the western part of the Cheshire‐Shropshire lowland records the advance, coalescence and subsequent uncoupling of Irish Sea and Welsh ice‐sheets during the Late Devensian stage. During advance a discontinuous sheet of basal till was emplaced across the floor of the region by subglacial lodgement. On retreat, compression of the Irish Sea ice sheet against bedrock obstruction generated a zone of supraglacial sedimentation resulting in the creation of the Wrexham‐Ellesmere‐Wem‐Whitchurch moraine system, and the formation of a wide range of sedimentary environments, including ice‐marginal sandur troughs, ice‐front alluvial fans, proglacial ribbon sandur, and subglacial, ice‐contact and proglacial lakes. The geometry of sedimentary units, and their lithologic and geomorphic characteristics, display spatially ordered patterns of sediment‐landform assemblage which show that the statigraphic succession is a response to rapidly changing depositional conditions at a retreating supraglacial ice‐margin punctuated by minor still‐stands and ice‐front oscillations.
Evidence of climatic change from oxygen and carbon isotope variations in sediments of a small arctic lake, Canada
Authors: Michel F. A. , Fritz P. , Drimmie R. J.
Published: February 2007

Radiocarbon dating of the organic‐rich sediments of Lake Illisarvik in the outer Mackenzie Delta indicates that formation of the lake occurred approximately 9500yr BP, with maximum expansion around 6000 yr BP. Sedimentation rates have remained relatively constant at an average of 0.3mm/yr.

13C results on biogenic and inorganic carbonates and organics indicate a change from dominantly terrestrial organics (−27 to −28%0) to submerged aquatic vegetation or plankton (−18 to −23%0) upon formation of the lake (9500yr BP), and a dramatic return to dominantly terrestrial organics at 5800yr BP (δ13C = −27 to −30%0). This latter shift is accompanied by a drastic reduction in the macroflora and fauna populations. 18O results suggest that a warmer climate than today existed prior to the shift at 5800yr BP.
Late Weichselian vegetation, climate, and floral migration at Liastemmen, North Rogaland, south‐western Norway
Authors: Paus Aage
Published: February 2007

Palynological results from Liastemmen indicate a tripartite division of the Late Weichselian. In the pleniglacial period, from deglaciation ca. 14000 BP to ca. 13000 BP,Artemisia‐dominated pioneer vegetation on disturbed, mineral‐soil was strongly influenced by cold winters and katabatic winds. The Late Weichselian Interstadial (ca. 13000 BP‐ca. 11000 BP) comprises aSalix‐shrub consolidation phase, and from ca. 12700 BP a tree‐birch phase. In the last 500 years of this period July and January means are estimated to about 16°C and between −2°C and −6°C, respectively. In the Younger Dryas Stadial (ca. 11000 BP‐ca. 10200 BP)Artemisia‐dominated vegetation returns. Three brief climatic deteriorations (ca. 12 250 BP, 11 700 BP, and 11 300 BP), unfavourable to woody vegetation on humus soils, are demonstrated within the interstadial. Critical climatic factors include cool winters and strong winds, exposing vegetation and soil to frost, drought, and erosion. The oldest and strongest oscillation, probably involving local deforestation, is correlated with the ‘Older Dryas deterioration’. Boreal‐circumpolar, eurasiatic, and arctic‐alpine plants dominated the late‐glacial flora. For the majority of the late‐glacial taxa a northward migration is demonstrated. This may also apply forPapaver radicatum, Pinguicula alpina, andPrimula scandinavica, all with bicentric distributions in Norway today.
The origin of deep buried channels of Elsterian age in Northwest Germany
Authors: Ehlers Jürgen , Linke Gerhard
Published: February 2007

Buried channels cut to a depth of over 100m into the underlying substratum of North Germany are almost exclusively of Elsterian age. Evaluation of geophysical well logs in the Hamburg area for the first time allows the construction of detailed longitudinal and transverse profiles. It can be shown that an apparently chaotic infill known from borehole records in some cases is actually a regular sedimentary sequence, fining from proximal to distal. Channel formation seems to have been the result of catastrophic meltwater release in the marginal parts of the ice sheet. The channel infill reflects these episodic outbursts of meltwater. During deglaciation, the channel remnants became infilled with fine sediments. The channels ceased to exist as morphologically detectable forms at the end of the Holsteinian Stage.
Middle Pleistocene glacial stratigraphy at Baxter Rivulet, western Tasmania, Australia
Authors: Fitzsimons Sean J. , Colhoun Eric A. , Van De Geer Guus
Published: February 2007

Mapping, analysis and interpretation of glacigenic sediments in the King Valley, Tasmania has led to a revision of the Pleistocene stratigraphy of Tasmania. The sediments provide evidence of a glaciation that occurred between the Middle Pleistocene Henty Glaciation and the Early Pleistocene Linda Glaciation. TheMoore Glaciationis estimated, on the basis of weathering rinds, amino‐acid dating and palaeomagnetism to have occurred between 400000 and 550000 yrs BP. At Baxter Rivulet, sediments of the Moore Glaciation rest unconformably on highly weathered till and weathered Ordovician limestone and are overlain by outwash gravel of the Henty Glaciation. The Moore Glaciation sediments can be divided into four formations on the basis of lithology, organic content and degree of chemical weathering. The Huxley Formation (oldest) was deposited by an ice advance of the Mt. Jukes Glacier and is overlain by the Baxter Formation. The Baxter Formation consists of a bed of organic silty sand which records a cool non‐forested flora of an interstadial period. The overlying Pyramid and Moore formations are outwash gravels from the Mt. Jukes and King Valley glaciers respectively. Though deposited during the same general ice advance, these two gravels were deposited at different times and show that the glaciers of the West Coast Range had spatially differentiated responses to climatic change.
Holocene floodplain diachronism and inherited downstream variations in fluvial processes: A study of the river Perry, Shropshire, England
Authors: Brown Antony G.
Published: February 2007

This paper attempts to explain downstream variations in the rates and processes of Holocene floodplain formation in a small to medium‐sized, lowland catchment in Central England. Four macro‐reaches were identified and horizons from at least one stratigraphic cross‐section from each were radiocarbon dated. Considerable diachronism was revealed with the basal age and hence minimum residence time of the top two metres varying from 1000‐9000yrs. The trend, a decrease in minimum residence time downstream, is explained by the basin‐and‐gorge bedrock long‐profile inherited from the Devensian glaciation of the area. This is illustrated by a positive relationship between the mean floodplain accumulation rate and the SL index (slope‐stream length product). Pollen analysis of the organic sediments shows that floodplain clearance took place around 1 300 BP, but probably locally, pre‐dated and post‐dated accelerated alluviation associated with agricultural expansion in the catchment. This study concludes that (a) different macro‐reaches in this small to medium‐sized catchment have adjusted in different ways to long‐term catchment changes as part of autogenic floodplain evolution, (b) this has involved a change in the catchment's sediment conveyance characteristics during the Holocene, and (c) an important control on channel behaviour and floodplain sedimentation throughout the Holocene (as well as at present) has been the valley slopes inherited from the Quaternary glaciation of the area.
Neoglacial chronology and floristics in the Middle Teton area, central Teton Range, Western Wyoming
Authors: Mahaney William C. , Spence John R.
Published: February 2007

The relative ages of Neogfacial deposits above 2900m near Cloudveil Dome, Middle Teton, and Teepe glaciers, central Teton Range, western Wyoming, were determined using topographic position, weathering features, lichenometry, vegetation characteristics, and soils. A three‐fold deposit sequence is identified and correlated with the Gannett Peak, Audubon and Indian Basin Neoglacial advances described elsewhere in the Teton and nearby Wind River ranges. While soil profile morphology proved very useful in distinguishing deposits of different age, other age indicators such as clay mineralogy and soil chemistry, proved of only marginal value in age discrimination. This chronosequence, emplaced over the last ∼5000yr, provides an excellent setting upon which to test changes in plant species composition and its use as a relative dating method.

Vascular plant species composition cannot be used to discriminate deposits of the different advances, possibly because of random colonisation and establishment combined with extensive mass wasting during the Neoglacial. However, certain vegetation features, such as total cover and species densities, appear useful as relative dating methods.
Postglacial history of alder (Alnus glutinosa (L.) Gaertn.) in the British Isles
Authors: Bennett Keith David , Birks H. John B.
Published: February 2007

Data from 92 postglacial pollen sequences are used to map the spread and increase of alder (Alnus glutinosa) across the British Isles between 9000 and 5000 years ago. The spread is found to be patchy and erratic in space and time. Consideration of the habitat requirements and reproductive ecology of alder suggest that it spread within Britain and Ireland after about 10 000 yr BP, when suitable habitat for it was scarce. Alder spread across most of Britain and Ireland early in the postglacial but only increased in abundance as (i) suitable habitat became available through changing sea levels, hydroseral successions, and floodplain development, and as (ii) rare weather events produced the necessary conditions for reproduction. Alder is unique among British and Irish trees in its requirement for a suitable habitat isolated among expanses of unsuitable habitats. Because of this, maps of its postglacial population spread and increase do not show the spatial coherence of maps for other forest tree taxa.
Radiocarbon dating the Devensian Lateglacial in Britain: New evidence from Llanilid, South Wales
Authors: Walker M. J. C. , Nerc D. D. Harkness
Published: February 2007

Radiocarbon dates are described from a section through Lateglacial and early Flandrian sediments at Llanilid, Mid‐Glamorgan, South Wales. Comparisons between age determinations on the alkali soluble (humic) and alkali insoluble (humin) organic fractions from 12 biostratigraphic horizons reveal the extent of contamination by both older and younger carbon residues. The Llanilid time‐scale suggests that for the Lateglacial, the earliest organic sediments date from around 13 200 yr BP, the early Interstadial Juniperus maximum occurred at ca. 12 400‐12 500 yr BP with a marked decline some 200 years later, the main Betula phase lasted only from ca. 11 700 to 11 400 yr BP and the end of the Interstadial occurred around 11 100 yr BP. The beginning of the Flandrian dates from ca. 10 000 yr BP, the Juniperus maximum occurred approximately 200 years later, the expansion of birch woodland began around 9600 yr BP, while the first hazel arrived in the area at ca. 9300 yr BP. These age determinations are discussed in the context of radiocarbon dates from comparable biostratigraphic horizons in western Britain and the dating of Lateglacial events in the ocean core records from the North Atlantic.
Holocene environmental change in South Georgia: Evidence from lake sediments
Authors: Birnie Jacqueline
Published: February 2007

The Holocene environmental history of South Georgia is important because of the island's location in the Southern Westerlies in an oceanic zone of the world devoid of high resolution terrestrial records. This is the first attempt to interpret a palaeoenvironmental record from lake sediments in South Georgia. It is based on a wide variety of analyses undertaken on cores from two lakes. Both are in the same, unglaciated, drainage basin, but one is at 80 m above sea‐level and near the altitudinal limit for vegetation growth, whereas the other is at 25 m and within the zone of continuous vegetation cover. Results from both lakes indicate shifts of vegetation boundaries, which, together with evidence for changing biotic productivity within the lakes themselves, are interpreted as indicating climatic changes. Radiocarbon dates on the main changes identify a climatic optimum, beginning before 5620 ± 290 14C yr BP, and ending at around 4815 ± 330 14C yr BP, when conditions in the upper part of the catchment were more conducive to plant growth than they are today. The record obtained from the lower lake was shorter, but indicates two periods of harsher climate relative to the present since 4000 yr BP. This interpretation of the lake evidence agrees with other dated evidence of environmental change from peat sections, glacial stratigraphy and geomorphology in South Georgia. Together the work allows an overall reconstruction of environmental change in the Holocene.
Autochthonous block fields in southern Norway: Implications for the geometry, thickness, and isostatic loading of the Late Weichselian Scandinavian ice sheet
Authors: Nesje Atle , Dahl Svein Olaf
Published: February 2007

The consistent geographical and altitudinal distribution of autochthonous block fields (mantle of bedrock weatheredin situ) and trimlines in southern Norway suggests a multi‐domed and asymmetric Late Weichselian ice sheet. Low‐gradient ice‐sheet profiles in the southern Baltic region, in the North Sea, and along the outer fjord areas of southern Norway, are best explained by movement of ice on a bed of deforming sediment, although water lubricated sliding or a combination of the two, may not be excluded. The ice‐thickness distribution of the Late Weichselian Scandinavian ice sheet is not in correspondence with the modern uplift pattern of Fennoscandia. Early Holocene crustal rebound was apparently determined by an exponential, glacio‐isostatic rise. Later, however, crustal movements appear to have been dominated by large‐scale tectonic uplift of the Fennoscandian Shield, centred on the Gulf of Bothnia, the region of maximum lithosphere thickness.
A palaeomagnetic and mineral magnetic study of the loess sequence at Liujiapo, Xian, China
Authors: Thistlewood Laurence , Jianzhong Sun
Published: February 2007

Employing an average vertical sampling interval of 20 cm, oriented samples were collected from 26 m of the loess section at Liujiapo, near Xian, China in order to refine the existing magnetostratigraphic record. Palaeomagnetic results reveal two short reversed‐polarity subzones within a profile of predominantly normally magnetised sediments, an interpretation that is at variance with previous results from this section and from other studies of Chinese loess. Investigation of sediment mineral‐magnetic properties indicates a close correspondence between down‐section variations in intensity of magnetisation, susceptibility and saturation isothermal Journal of Quaternary Science remanence (SIRM), and lithology. The ratios IRM‐100mT/SIRM and SIRM/ susceptibility appear to be particularly sensitive indicators of the degree of soil development and hence of palaeoclimate.
Distribution and provenance of the Baginton Sand and Gravel in the Wreake Valley, northern Leicestershire, England: Implications for inter‐regional correlation
Authors: Rice John
Published: February 2007

The Baginton Sand and Gravel is traced along the lower Wreake Valley as a continuous water‐laid stratum at the base of the drift succession. Its properties closely resemble those previously described from the proto‐Soar valley, namely an upward fining sequence and a composition dominated by pebbles of Triassic and Carboniferous origin. Such a provenance is consistent with the idea that the proto‐Soar once followed a route eastwards past Melton Mowbray, and that the drainage along the lower Wreake Valley has been reversed in the course of Pleistocene times. However, the slope of the sand and gravel train appears to be to the west rather than the east, and the rockhead relief is also inconsistent with an eastward‐flowing proto‐Soar. Until this enigma is resolved, it would be imprudent to use the Baginton Sand and Gravel as the basis for inter‐regional correlations. The issue is further complicated by the preservation at Brooksby of earlier interglacial or interstadial deposits whose temporal affinities remain unclear.
The Balderton Sand and Gravel: Pre‐Ipswichian cold stage fluvial deposits near Lincoln, England
Authors: Brandon Allan , Sumbler Michael G.
Published: February 2007

The Balderton Terrace marks a former course of the River Trent between Newark and the Lincoln Gap. The principal deposit, the Balderton Sand and Gravel, is interpreted as a braided river sediment. Ice wedge casts truncated by intraformational erosion surfaces at many levels indicate syndepositional permafrost. Remnant cover deposits overlying the Balderton Sand and Gravel include the partly aeolian Whisby Sand. Locally, both the upper part of the Balderton Sand and Gravel and the cover deposits exhibit features indicative of temperate climate pedogenesis. All these deposits are affected by subsequent cryoturbation. On the basis of these features and the geomorphological and topographical relationship to other terrace deposits of the area, the Balderton Sand and Gravel and Whisby Sand are regarded as post‐Hoxnian and pre‐lpswichian, i.e. Wolstonian. Electron spin resonance age determinations for fossil elephant teeth and amino acid analyses on molluscs from the Balderton Sand and Gravel suggest correlation with Oxygen Isotope Stage 6. The Balderton Sand and Gravel has yielded a cold‐climate mammalian fauna dominated by woolly mammoth and woolly rhinoceros, though rarer species suggest periods of milder climate. Silts from channels near the base of the deposit have produced pollen, mollusc, ostracod and beetle assemblages also indicating a cold climate.
A pre‐Ipswichian cold stage mammalian fauna from the Balderton Sand and Gravel, Lincolnshire, England
Authors: Lister Adrian M. , Brandon Allan
Published: February 2007

The Balderton Sand and Gravel has yielded one of very few mammalian faunas dated to the penultimate Cold Stage in Britain. The assemblage is dominated by mammoth and woolly rhinoceros, with subordinate horse, red deer, bison, straight‐tusked elephant, musk ox, reindeer, wolf, lion, brown bear and cf. narrow‐nosed rhinoceros. This fauna indicates cold stage conditions, probably including one or more interstadial episodes. The presence of straight‐tusked elephant and cf. narrow‐nosed rhinoceros supports its pre‐Devensian age, and provides corroboration for the occurrence of these taxa in the British Wolstonian. An attempt is made to analyse the fossil collection by preservation type and adhering sediment: the occurrence of individual species appears to be largely uncorrelated with lithology. The Balderton assemblage corresponds well to other British mammal faunas assigned to a cold interval between the Hoxnian and Ipswichian Interglacials.
Holocene vegetation and volcanic activity, Auckland Isthmus, New Zealand
Authors: Newnham Rewi M. , Lowe David J.
Published: February 2007

A 12 000 to 4000 yr BP pollen and tephra‐bearing profile from Auckland, New Zealand, provides insights into the vegetation history and evidence for early Holocene volcanic activity in this area centred on the Mount Wellington basaltic volcano. Possibly 500 yr separated initial scoriaceous ash deposition (ca. 9500 yr ago) and subsequent major lava flows (ca. 9000 yr ago) from Mount Wellington. The local vegelation, topography, and drainage patterns were substantially modified during this time, and damming by the lava flows resulted in the formation of Lake Waiatarua in a shallow valley head ca. 9000 yr ago. Diatom evidence indicates that this lake was initially deep (> 5 m) but was shallowing around 4000 yr ago. In contrast to the Mount Wellington eruptions, tephra deposition resulting from distant rhyolitic volcanic activity of the central North Island and Mayor Island has had little effect on the Auckland vegetation during this time interval (12 000–4000 yr ago).

Between ca. 12 000 and 10 000 yr ago, conifer‐angiosperm forest was the predominant vegetation cover on Auckland Isthmus, but during the early Holocene, forest dominated by Metrosideros expanded, probably on to fresh volcanic surfaces resulting from the Mount Wellington eruptions. At this time, swamp forest communities developed in Waiatarua valley basin, and included species indicative of moist, mild, relatively frost‐free climates. Some taxa show histories consistent with other records from the northern New Zealand region, including the rise of Ascarina lucida ca. 11 000 to 9000 yr ago, and its subsequent decline, and the expansion of Agathis australis (kauri) forest communities from ca. 6000 yr ago. Taken together the history of local and regional vegetation points to a mild, moist and weakly seasonal early Holocene climate, which subsequently became drier with greater seasonal temperature extremes.
Dissolution and depletion of ferromagnesian minerals from Holocene tephra layers in an acid bog, New Zealand, and implications for tephra correlation
Authors: Hodder A. P. W. , De Lange P. J. , Lowe D. J.
Published: February 2007

This study examines the depletion of ferromagnesian silicate minerals from a sequence of thin, distal, mainly rhyolitic tephra layers of Holocene age preserved in an acid peat bog (Kopouatai), North Island, New Zealand. The rate of such depletion has been fast, as indicated by the complete loss of biotite from one tephra layer (Kaharoa Tephra), in which it is normally dominant, in only ca. 770 yr. Chemical dissolution is advocated as the likely cause for the depletion, with amphiboles and other mineral grains commonly showing etch pits, microcaves, and other characteristic surface solution features. Theoretical thermodynamic and kinetic models show a marked increase in the rate of dissolution of all ferromagnesian minerals under conditions of low pH (< 4), but that where silica concentrations in solution are high the relative proportions of minerals remaining are unaffected. However, where concentrations of dissolved silica are low, as in most bog environments, the relative proportions of ferromagnesian minerals are affected as well as absolute amounts being decreased. Amphiboles are depleted relative to pyroxenes, consistent with kinetic studies.

The results show that the identification and correlation of tephras on the basis of relative abundances of ferromagnesian minerals alone may be unreliable, and emphasise the need to use multiple criteria in such studies.
An 11 000‐year record of vegetation and environment from Lago di Martignano, Latium, Italy
Authors: Kelly Martyn G. , Huntley Brian
Published: February 2007

A pollen diagram from Lago di Martignano, a maar lake in central Italy, provides an 11000‐year record of vegetation and environment change. The earliest pollen spectra are dominated by Artemisia and Gramineae, representing late glacial steppe vegetation typical of the Mediterranean region. Broad‐leaved forests were established by ca. 11 000 yr BP. Although Quercus initially dominated their canopy, a wide range of other mesophyllous trees were also present. Pollen values for sclerophyllous tree and shrub taxa characteristic of Mediterranean woodlands and scrub are initially low (<10%). After ca. 7000 yr BP, however, they begin to increase and rise to a peak of >40% of total land pollen at ca. 6700 yr BP, with Olea europaea the single most abundant taxon. Human influence upon the vegetation only becomes significant somewhat after this peak, with progressive clearance of woodland and expansion of herbaceous communities. Castanea sativa and luglans regia pollen is recorded consistently from the beginning of the rise in pollen values for taxa characteristic of Mediterranean scrub communities. Pollen values for arable crops increase progressively after ca. 5500 yr BP, following the peak pollen values for taxa characteristic of Mediterranean scrub vegetation. Late glacial and Holocene climate changes have been complex in this region, with the present character of the climate developing only during the last millennium. Rates of change of pollen spectra peak during this period.
A dated cave sediment record of Pleistocene transgressions on Berry Head, Southwest England
Authors: Proctor Christopher J. , Smart Peter L.
Published: February 2007

Berry Head, a limestone headland in Torbay, southwest England, exhibits a series of subaerial marine erosion platforms and raised beaches spanning an altitude range of 97 m. Solution caves on the headland show preferred horizontal development at elevations that are correlated with the marine erosion platforms, and developed in a marine/freshwater mixing zone whose position was controlled by high sea‐level still‐stands. Corbridge Cave in Berry Head Quarry lies below the raised beaches in Torbay, and contains evidence of three marine transgressions in the form of fine‐grained marine ponding deposits with a marine microfauna. Uranium‐series dating of intercalated speleothems indicates that a transgression during oxygen isotope stage 5e reached an elevation of 5.8 m OD, while an earlier transgression (probably during stage 7) reached at least 7.2 m OD. These findings are used to constrain possible interpretations of the aminostratigraphy of raised beaches in Southwest Britain, and a correlation of the Unnamed Stage of Bowen, Sykes, Reeves, Miller, Andrews, Brew and Hare with oxygen isotope stage 5e is proposed.
Stratigraphy and geochemistry of a sequence of Quaternary palaeosols in the Lower Teleki Valley, Mount Kenya, East Africa — Implications for interregional correlations
Authors: Mahaney W. C. , Slowpoke R. G. V. Hancock , Rutter N. , Sanmugadas K.
Published: February 2007

The relative weathering of a sequence of five palaesols formed in different parent materials, including bedrock of phonolitic composition, is described and assessed. The three lower palaeosols (units 3–5) are considered to be of interglacial origin. The saprolite (unit 5), in phonolite, formed prior to deposition of the lower Brunhes‐age till, is considered to be as old as the Brunhes Matuyama boundary (0.73 myr). The other two palaeosols in this group (units 3 and 4), derived from loess and till, respectively, formed over middle to late Brunhes time under palaeoclimates that were wetter (and presumably warmer), and of sufficient leaching power to move clay, as well as organically complexed extractable Fe and Al. The palaeosols in unit 3 are more complex than the lower ones. Their upper and lower horizons have about the same chemical composition as the lowest two palaeosols, while the middle horizons are similar to the upper two palaeosols (units 1 and 2). Radiocarbon dates for unit 3 are considered to be too young to account for the strong weathering in the upper and lower horizons. This interpretation is supported by high D/L ratios of aspartic acid. Overlying sediments, emplaced by episodic colluvial (unit 2) and slope wash (unit 1) processes, are less weathered; the lower colluvial unit in this group was emplaced during the late stade of the last glaciation. The surface sediments were emplaced more recently during the same interval and weathered mainly during the post‐glacial period. Tentative correlations with core 82PCS18 from the Canary Basin show that upper unit 3 is probably equivalent to Isotope Stage 5e, lower unit 3 to Isotope Stage 7, unit 4 to Isotope Stage 8, and unit 5 to Isotope Stage 9. Units 1 and 2 are firmly correlated with Isotope Stage 2.
Late Quaternary climatic history of the Chilean Channels based on fossil pollen and beetle analyses, with an analysis of the modern vegetation and pollen rain
Authors: Ashworth Allan C. , Markgraf Vera , Villagran Carolina
Published: February 2007

Fossil beetles and pollen were examined from an intermorainal bog at Puerto Edén, Isla Wellington, Chile (latitude 49°08'S, longitude 74°25'W). Wood from near the base of the section has an age of 12 960 ± 150 yr BP. Occurrence of flightless beetle species in the basal peat sample is evidence that some members of the biota survived the last glacial maximum in refugia. The assumption that the Chilean Channels were entirely ice‐covered is incorrect. Plants and insects that invaded the deglaciated terrain were those of an Empetrum heathland in which patches of Nothofagus forest were restricted to sheltered locations. The climate supporting the heathland is inferred to have been windier and probably drier than that of the present day. From 13 000 yr BP to 9500 yr BP Nothofagus forest expanded, possibly in response to less windiness and more available moisture. Neither the fossil beetle nor pollen data support a return to significantly colder conditions between 11 000 and 10 000 yr BP at the time of the Younger Dryas Stade. From 9500 to 5500 yr BP the climate was as wet as that of the present day, based on an increased representation of the pollen of moorland plants and of aquatic beetle species. From 5500 to 3000 yr BP the climate was drier, as indicated by the expansion of Empetrum heath and the reduction in mesic habitats. From 3000 yr BP to the present‐day mesic habitats dominated as the climate returned to a wetter mode. The alternatively wetter and drier episodes are attributed to latitudinal shifts in the position of storm tracks in the belt of Southern Westerlies.
Late glacial and holocene lake level fluctuations in Lake Biel, western Switzerland
Authors: Wohlfarth Barbara , Schneider Anne Marie
Published: February 2007

Cores and outcrops from the southern shore of Lake Biel were studied to reconstruct the nearshore environment of the lake between ca. 12000 and 5000 yr BP. Core correlations were established by lithostratigraphical and pollen analytical correlations. From the Allerød to the Preboreal time quiet hydrodynamic conditions favoured the deposition of lake marl in the littoral zone and peat on the shore. Between the Preboreal(?) and the Atlantic the littoral zone shows a higher hydrodynamic environment with allochthonous material, whereas peat and clay layers are recorded from the shore. During the Older Atlantic severe erosional episodes caused the erosion of Boreal, Preboreal and Younger Atlantic layers. The previously described long hiatus between the Allerød and the Boreal time can now be connected with these erosional episodes. From Younger Atlantic to Subboreal time the littoral zone displays quiet conditions again with sedimentation of lake marl. On the basis of these results a lake level curve for Lake Biel is proposed: high lake level stands can be traced during the Allerød, Boreal, Older Atlantic and Younger Atlantic biozones; low lake level stands are found during the Allerød, Younger Dryas, Preboreal and Older Atlantic biozones.
Holocene palaeo‐oceanography of the northern Iceland Sea, indicated by Radiolaria and sponge spicules
Authors: Molina‐Cruz Adolfo , Geomar
Published: February 2007

The micropalaeontological analysis of 49 samples, from three box cores collected from the northern Iceland Plateau, indicates that radiolarian and sponge remains are rare in glacial sediments but are common after deglaciation; mostly during the first half of the Holocene. The record trend of the abundance of Oxycalthrop sponge spicules is regional in character. Fluctuations in radiolarian abundance, and the first occurrence of each of the species inhabiting the Iceland Sea at present, coincide with changes in oceanographic conditions that occurred during the Holocene. At the Younger Dryas chronozone, the downcore record of Cycladophora davisiana (Ehrenberg) depicts a maximum peak, because the sea surface was colder than it has been recently; though still seasonally free of ice‐cover. During the Preboreal, Boreal and Atlantic chronozones, Amphimelissa setosa (Cleve) was highly abundant, as a consequence of the increase in mixing between the Arctic Water and the North Atlantic Water. During the Subboreal chronozone, the East Icelandic Current became better developed, and initiated the onset of the ‘Arctic Front’ in the Iceland Sea; as is suggested by the Lithomitra lineata (Ehrenberg) record. This ‘cooled’ environment also allowed an increase in the occurrence of Artobotrys borealis (Cleve). The reappearance of Stylodictya validispina (Jörgensen) in the Iceland Sea, during the Sub Atlantic chronozone, indicates a larger input of Atlantic Water, via the Norwegian Current.
Late quaternary of the middle Caquetá River area (Colombian Amazonia)
Authors: Hammen Thomas Van Der , Duivenvoorden Joost F. , Lips Johanna M. , Urrego Ligia E. , Espejo Nohora
Published: February 2007

The late Quaternary history of the middle Caquetá River area in Colombia, northwestern Amazonia is described, based on observations of river bank sections, radiocarbon dates and palynological analyses of organic layers in floodplain and low terrace sediments of the Caquetá River. It is shown that the Late Pleistocene and Holocene climatic changes that took place in the Andean Cordilleras, were related to the depositional and erosional history of the Caquetá River in the Colombian Amazonian lowlands.

The low terrace sediments consist of sandy and gravelly deposits covered by clays that sometimes contain lenses of peaty material. From these organic low terrace sediments, seven finite radiocarbon dates were obtained of Middle Pleniglacial age, between 56 000 and 30 000 yr BP. The coarse textured basal deposits of the low terrace apparently stem from the early part of the Middle Pleniglaciai period, during which the effective rainfall in the Andes was relatively high and the Andean glaciers had a considerable extension. Palynological data from silty sediments with organic remains at one site, show an interval when drier and more open types of vegetation on poor soils must have covered a larger area than today, but Amazonian forest was still the dominating type of vegetation. This interval might correspond to one of the Middle Pleniglacial savanna intervals from eastern Amazonia (Carajas).

No organic sediments from the Upper Pleniglacial period were found and hence radiocarbon dates were not obtained. In the Andes this period had a very cold climate with low effective rainfall and in the east Amazonian Carajas area it is characterised by the relative extension of open savanna vegetation. The river run‐off and sediment transport must have been much lower than in the Middle Pleniglacial and the Caquetá River cut itself down in its own sediments.

Two Late‐glacial radiocarbon datings obtained at one site (ca. 12 500 yr BP) indicate the existence of a Late‐glacial sedimentation phase, separated from the Holocene sequence by a minor erosional phase.

Organic layers in the Holocene floodplain sediments yielded 28 radiocarbon dates between 10 000 and 355 yr BP. Holocene sedimentation started with the rapid deposition of (sandy) clay possibly in a partly permanently inundated Caquetá valley. During the major part of the Holocene (silty) clays were deposited, with a dominant seasonal inundation cycle.
Late‐glacial and Holocene sedimentation and fluctuations of river water level in the Caquetá River area (Colombian Amazonia)
Authors: Hammen Thomas Van Der , Urrego Ligia E. , Espejo Nohora , Duivenvoorden Joost F. , Lips Johanna M.
Published: February 2007

The sequence of Late‐glacial and Holocene alluvial sedimentation in the middle Caquetá River Basin of Colombian Amazonia is described, based on the study of the sediments and palynology of several river bank sections and on 30 radiocarbon dates.

An early Late‐glacial sedimentation cycle is recognised, followed by a minor late Late‐glacial erosion phase.

The Holocene valley fill consists of grey clays (often present in the lower part of the sections) deposited in open water and silty clays often with faint yellow mottling, deposited under a regime of seasonal flooding. The base of the Holocene sections is formed by sands, where exposed. In two places the transition of sand to open‐water grey clay was dated around 10 000 yr BP and there is a suggestion that open water may have been more common at the beginning of the Holocene than later, when sedimentation by seasonal flooding became important. In many places much of the earlier Holocene sediments may have been removed by erosion and replaced by younger sediments, by a process of lateral aggradation. A considerable part of the present valley fill is younger than ca. 3500 yr. However, in several places older Holocene sediments are found, apparently only little affected by later erosion, lying below younger varzea silty clays.

During the Holocene more organic sediments were formed in periods with reduced river discharge, related to drier climates in the Andes and possibly in Amazonia. These dry periods, deduced from data in the Caquetá River area, correspond well with dry phases in other parts of northwestern South America (e.g. between approximately 2700‐1900 yr BP and approximately 3200‐3800 yr BP). Rates of average net sedimentation, calculated from dated sections that apparently lack major hiatuses caused by erosion, were high in the lower Holocene, low during the middle Holocene and increase again in the upper Holocene. Levee deposits became coarser and the high river level of the Caquetá increased during the late Holocene. These phenomena may be explained by the increasing influence of man on the vegetation cover in the Andean headwater areas and possibly also in the Amazonian catchment area of the Caquetá River.
Late Quaternary glaciation of the Cordillera Real, Bolivia
Authors: Seltzer Geoffrey O.
Published: February 2007

Glacial geological studies in tropical mountain areas of the Southern Hemisphere can be used to address two issues of late Pleistocene climate change: the global synchroneity of deglaciation and the magnitude of temperature reduction in the tropics. Radiocarbon dates from the Cordillera Real and from other areas in Perú and Bolivia suggest that late Pleistocene glaciation culminated between 14 000 and 12 000 yr BP, followed by rapid deglaciation. Because deglaciation was apparently synchronous with that in Northern Hemisphere regions, insolation change at high latitudes may not have been the only factor that produced global deglaciation at this time. Late Pleistocene glaciation in the Cordillera Real culminated when precipitation was 200 mm yr−1 higher and temperatures were 3.5° ±1.6°C lower than today; this produced an equilibrium‐line altitude depression of about 300 ± 100 m on the western side of the cordillera. Prior to this, conditions were drier and probably at least as cold. However, the lack of moraines in the Cordillera Real dated to the Last Glacial Maximum (ca. 18000 yr BP) precludes using the equilibrium‐line altitude method to quantitatively evaluate the discrepancy between warm sea‐surface temperatures and cold terrestrial conditions reconstructed with other proxies for this time period.
Thermoluminescence dating and geochemistry of loessic deposits in southeast England
Authors: Parks David A. , Rendell Helen M.
Published: February 2007

The results of a thermoluminescence (TL) dating and geochemical survey of loessic deposits in southeast England, involving sampling at 26 localities, demonstrate that the loessic deposits appear to be the product of at least three depositional phases of aeolian silt during the Late Pleistocene, namely 10‐25 ka BP, 50–125 ka BP and > 170 ka BP. The majority of localities sampled date to the Late Devensian, but isolated pockets of older material were found throughout the area. The majority of the samples analysed were of decalcified material. The results of geochemical analyses of major oxide and trace element concentrations indicate the uniformity of material and suggest a common provenance.
Influence of glacier hydrology on the dynamics of a large Quaternary ice sheet
Authors: Arnold Neil , Sharp Martin
Published: February 2007

The influence of glacier hydrology on the time‐dependent morphology and flow behaviour of the late Weichselian Scandinavian ice sheet is explored using a simple one‐dimensional ice sheet model. The model is driven by orbitally induced radiation variations, ice‐albedo feedback and eustatic sea‐level change. The influence of hydrology is most marked during deglaciation and on the southern side of the ice sheet, where a marginal zone of rapid sliding, thin ice and low surface slopes develops. Such a zone is absent when hydrology is omitted from the model, and its formation results in earlier and more rapid deglaciation than occurs in the no‐hydrology model. The final advance to the glacial maximum position results from an increase in the rate of basal sliding as climate warms after 23000 yr BP. Channelised subglacial drainage develops only episodically, and is associated with relatively low meltwater discharges and high hydraulic gradients. The predominance of iceberg calving as an ablation mechanism on the northern side of the ice sheet restricts the occurrence of surface melting. Lack of meltwater penetration to the glacier bed in this area means that ice flow is predominantly by internal deformation and the ice sheet adopts a classical parabolic surface profile.
Danish pollen records radiocarbon‐dated to between 50000 and 57000 yr BP
Authors: Kolstrup Else
Published: February 2007

Radiocarbon‐dated pollen diagrams from four Danish sequences are presented in their sedimentological context. The pollen diagrams indicate the former presence of stands of Betula and Pinus and of Ericales, Poaceae, Cyperaceae and other herbs. From a straightforward comparison with other diagrams, one of the present series is tentatively correlated with part of the Early Weichselian Brørup Interstadial and two with parts of the Odderade Interstadial, which has not been demonstrated previously in Denmark. One diagram and part of another do not seem to match previously published records in northwest Europe. Yet, the possibility that the sediments date to hitherto unrecorded periods with environmental conditions similar to those reflected in known Weichselian deposits is not excluded. In two of the sequences high percentages of charcoal particles suggest the former occurrence of fires, which influenced the palaeovegetation and soil surface stability. It is suggested that counting of charcoal particles is included in future investigations in order to establish whether periods with fires can be identified in the sedimentary sequences.
Geochemical stability of fine‐grained silicic Holocene tephra in Iceland and Scotland
Authors: Dugmore Andrew J. , Newton Anthony J. , Sugden David E. , Larsen Gudrun
Published: February 2007

This paper tests two assumptions fundamental to the use of fine‐grained silicic tephras from Iceland for creating chronological frameworks in northwest Europe. It is shown firstly, that glass shards can retain their overall chemical integrity on at least a four millennial time‐scale in contrasting depositional environments in Iceland and Scotland, and secondly, that an acid digestion process, the most practical method for extracting tephra from peat, does not significantly bias the results of major element analysis by electron microprobe. The implication is that there is great potential and an appropriate method for developing both the resolution and the spatial coverage of chronologies based on silicic Icelandic tephras in northwest Europe.