Part Of Marine Isotope Stage Research Articles

Human occupation of the Arabian Empty Quarter during MIS 5: evidence from Mundafan Al-Buhayrah, Saudi Arabia

The Empty Quarter (or Rub' al Khali) of the Arabian Peninsula is the largest continuous sandy desert in the world. It has been known for several decades that Late Pleistocene and Holocene deposits, representing phases of wetter climate, are preserved there. These sequences have yielded palaeontological evidence in the form of a variety of vertebrate and invertebrate fossils and have been dated using various radiometric techniques. However, evidence for human presence during these wetter phases has until now been ephemeral. Here, we report on the first stratified and dated archaeology from the Empty Quarter, recovered from the site of Mundafan Al-Buhayrah (MDF-61). Human occupation at the site, represented by stone tools, has been dated to the later part of Marine Isotope Stage (MIS) 5 using multiple luminescence dating techniques (multigrain and single grain OSL, TT-OSL). The sequence consists primarily of lacustrine and palustrine sediments, from which evidence for changing local environmental conditions has been obtained through analysis of fossil assemblages (phytoliths and non-marine molluscs and ostracods). The discovery of securely-dated archaeological material at ∼100 to 80 ka in the Empty Quarter has important implications for hypotheses concerning the timing and routes of dispersal of Homo sapiens out of Africa, which have been much debated. Consequently, the data presented here fill a crucial gap in palaeoenvironmental and archaeological understanding of the southern Arabian interior. Fossils of H. sapiens in the Levant, also dated to MIS 5, together with Middle Palaeolithic archaeological sites in Arabia and India are thought to represent the earliest dispersal of our species out of Africa. We suggest that the widespread occurrence of similar lithic technologies across southern Asia, coupled with a growing body of evidence for environmental amelioration across the Saharo-Arabian belt, indicates that occupation of the Levant by H. sapiens during MIS 5 may not have been a brief, localized ‘failed dispersal’, but part of a wider demographic expansion.

Shifting frontal regimes and its influence on bioproductivity variations during the Late Quaternary in the Indian sector of Southern Ocean

Reconstruction of palaeoproductivity from Southern Ocean is crucial for understanding the functioning of the Southern Ocean biological pump in the past. High resolution records of multi-proxy parameters (calcium carbonate, opal, total organic carbon biogenic barium and planktonic carbon isotope ratios (δ13C)) were investigated in two well-dated sediment cores (SK200/22a and SK200/27) from the Indian sector of Southern Ocean situated to the north and south of Antarctic Polar front (APF), respectively. The palaeoproductivity records extending ~95ka BP (SK200/22a) and 75ka BP (SK200/27) revealed inverse relationships between the calcite and opal productivity, indicating the influence of shifting nutrient regimes. At core SK200/22a, reduced calcite productivity during marine isotope stage (MIS) 2, 4, and part of MIS 3 suggest an equatorward migration of the frontal regimes during glacial intervals. Compared to this, the region south of the APF (core SK200/27) was characterized by the near absence of calcite content during the last glacial period and increased opal productivity during MIS 1 and MIS 3, supporting a southward migration of APF during warmer intervals. Ba(bio) records exhibit good correlation with opal records in both the cores and also correlate with that of calcite record at SK200/22a, indicating that Ba is influenced by the combined opal and calcite productivity. The enhanced opal productivity during the glacial periods north of the APF is attributed to the northward shifting of oceanic fronts and associated transfer of nutrients. Diatom productivity records of SK200/22a reveal significant similarities with the dust records from the Antarctic and Southern Ocean, but showed no significant relationships with the diatom record of SK200/27. It is proposed that the dust-derived Fe input had apparently influenced the palaeoproductivity north of the modern APF, but had a minor influence on opal productivity south of the APF. Comparison with the ice core climate records from Antarctica and Greenland revealed that bioproductivity peaks in the study region are nearly synchronous with the millennial Antarctic warming events. Remarkably, the calcite and opal productivity records at SK200/22a responded differently to the Antarctic warming events, with opal productivity lagging behind the calcite productivity peaks by ~1–2ka.

Stalagmite δ18O variations in southern India reveal divergent trends of Indian Summer Monsoon and East Asian Summer Monsoon during the last interglacial

Indian monsoon variations for the period around ∼100ka have not been documented from terrestrial archives, while limited data do exist from the Indian Ocean. Some paleoceanographic studies have reported abrupt and stepwise changes in the monsoon intensity during the last deglaciation, but similar observations have not been possible for earlier periods such as the interglacial to glacial transition, mainly because of the coarse resolution (∼500 to 1000 years) provided by marine archives of that age. Here, we report a new δ18O data set from a stalagmite (3-ACN) that grew in the Belum caves, Andhra Pradesh, a semi-arid region in southern India, with a resolution of ∼85 years. Age assignment to different growth layers consistent with associated analytical errors indicates that the record could span ∼9ky during part of Marine Isotope Stage (MIS) 5d-c, from ∼108 to ∼99ka. δ18O variations in this stalagmite, if interpreted using the ‘amount effect’, i.e., 18O depletion of ∼1.5‰ per 100 mm increase in monsoon rainfall, indicate a step-like increase during the transition from the cooler stadial MIS 5d to warmer interstadial MIS 5c, signifying an abrupt reduction in monsoon rain. The new data presented highlight divergent trends between the Indian and the East Asian Summer Monsoons for a time period for which not many high-resolution comparisons are available.

Last Glacial droughts and fire regimes in the central Mexican highlands

ABSTRACTOver the last glacial cycle, climate variations in the Neotropics were related to diverse forcing mechanisms whose understanding has been limited because of the scarcity of continuous long records. Here we use high‐resolution charcoal particle accumulation, inorganic carbon precipitation and magnetic susceptibility data from Lake Chalco, located in high‐altitude tropical central Mexico, to assess the fire regimes and drought periods between ∼85 and 10.8k cal a BP. Overall, drought intervals were characterized by high carbonate deposition and were contemporary with high spring insolation. Most of the high fire activity periods were coupled with droughts, whereas some of them seem to have responded to volcanic activity in the basin. Periods of more fire activity during the latest part of Marine Isotope Stage 3 were associated with a long interval of higher spring insolation. Increase in drought frequency during 47–27k cal a BP were possibly linked to a more active Laurentide Ice Sheet influencing the oceanic and atmospheric controls of the tropical climatic system. In fact, Chalco and Cariaco records show similar millennial‐scale trends, suggesting a role of the Intertropical Convergence Zone in modulating moisture availability in the region.

Stratigraphy and Palaeopedology of the Palaeolithic Cave Site of Combe‐Saunière, Southwest France

The sequence of Combe‐Saunière (southwest France) has been studied with a large suite of methods, including micromorphology, geochemistry, magnetic susceptibility, and organic matter (OM) analysis in order to document the post‐depositional processes that occurred during the last climatic cycle at the cave entrance. This study shows that intense weathering together with the accumulation of OM and phosphates by cave animals and others vectors (including humans) occurred during the phases of low clastic sedimentation. During the latter part of Marine Isotope Stage (MIS) 3, the Aurignacian and Gravettian humus‐bearing levels, which may be classified as cryoturbated leptosols, show incomplete decalcification and are dominated by poorly evolved forms of phosphates (bone fragments, coprolites). Phosphatized cambic B‐horizons formed at the beginning of MIS 3 and the Early Glacial and may reflect longer periods of pedological modification. The molecules identified by the analysis of the OM extracted from the Châtelperronian level derive mostly from the degradation of vegetal matter, most notably from conifers and mosses, in addition to bacteria and fungi. The Last Interglacial s.l. (MIS 5) is typified by the development of a phosphatized illuviated B‐horizon. Intense weathering together with phosphate leaching and precipitation took place in this soil, forming thick apatite–CaOH crusts. Although the poor chronological resolution prevents us from drawing clear conclusions as to the respective roles of the factors involved, phosphate accumulation and weathering seem to be controlled primarily by the duration of the soil‐forming periods. This study strongly suggests that a climatic signal has been recorded in the deposits.

Depositional environment and climate changes during the late Pleistocene as recorded by the Netiesos section in southern Lithuania

The Netiesos section in southern Lithuania exposes a late Pleistocene sedimentary sequence at a depth of between 17 and 4 m. An interdisciplinary study of the section investigated the environmental changes that occurred in the study area during the greater part of Marine Isotope Stage (MIS) 5. Geochemical, thermoluminescence, palaeontological (plant macro-remain, diatoms, fishbones) and magnetic susceptibility analyses were performed on numerous sediment samples. Chronological control of the sequence was provided by electron spin resonance (ESR), infrared optically stimulated luminescence (IR-OSL) and conventional radiocarbon dating methods. This interdisciplinary approach enabled the subdivision of the section into stratigraphic units reflecting environmental changes. According to chronological data, the development of the Netiesos palaeolake began at the end of the Medininkai (Saalian) glaciation, which is thought to correlate with MIS 6, and continued up to the thermophilous deciduous forests phase of the subsequent last interglacial of MIS 5. Sediments of the final phase of the interglacial are missing, as are the initial and final phases of the following early Nemunas (Weichselian) cooling (MIS 4). The palaeomagnetic Blake Event was recorded in the interglacial sediments. One of the richest palaeofloras in the East Baltic region was observed representing the second half of MIS 5. The implications of the results for the regional late Pleistocene climato-chronostratigraphy are discussed.

The position and context of Middle Palaeolithic industries from the Ebbsfleet Valley, Kent, UK

The late Middle Pleistocene sites in the Ebbsfleet Valley, Kent, UK, have yielded archaeological assemblages critical to understanding the early Middle Palaeolithic of northwestern Europe. Despite a long history of research, the nature and context of these assemblages are still poorly understood. This paper clarifies the stratigraphic, environmental and archaeological records at Ebbsfleet. These reflect a cold–warm–cold sequence of climatic events, preserved within part of the Taplow/Mucking Formation of the Thames (Marine Isotope Stage (MIS) 8/7/6). Levallois artefacts are shown to be restricted to the lower part of the Ebbsfleet Channel sequence (Phases I and II) and are assigned to late MIS 8/early MIS 7. This material is associated with fauna indicative of open environments during both cool and temperate conditions. Handaxe assemblages are recorded from higher up the sequence (Phases III–V), but have been redeposited from higher terrace units nearby. No primary context archaeology is apparent during these later phases of aggradation. This may indicate that humans abandoned the site once available raw material became inaccessible, and may also reflect a decline in human presence in Britain during the latter part of MIS 7. Copyright © 2010 John Wiley & Sons, Ltd.

Varve counting reveals high resolution radiocarbon reservoir age variations in palaeolake Lisan

AbstractThe laminated lacustrine sediments deposited in the last glacial Lake Lisan represent annual deposits of primary aragonite and silty detritus that reflect the annual supply of bicarbonate‐bearing freshwater to the lake. A varve‐counting curve was constructed for the time interval of ca. 17.4–22 cal. ka BP based on aragonite U/Th, and atmospheric radiocarbon ages of organic debris recovered from the studied section. Radiocarbon in the primary (evaporitic) aragonite comprises both atmospheric and old carbon (reflecting the reservoir age). The aragonite reservoir ages were determined by comparing the aragonite radiocarbon dates to the varve counting curve, and are found to lie in the range 1900–600 a and display a continuous decline. This opens the possibility for high (annual) resolution monitoring of the reservoir age, similar in quality to tree ring counting, during the upper part of Marine Isotope Stage (MIS) 2. Our work also demonstrates that a ‘uniform’ reservoir age correction is inappropriate when determining the chronology of short‐term climate events in lacustrine environments. Copyright © 2009 John Wiley & Sons, Ltd.

A late Pleistocene record of aeolian sedimentation in Blanche Cave, Naracoorte, South Australia

We provide geochemical analyses and grain size data for a clearly layered, 80 cm thick sedimentary deposit close to a roof collapse in Blanche Cave near Naracoorte in SE South Australia. This deposit contains aeolian material deposited between ∼40 ka and 14 ka cal BP and which yields airborne sediments spanning the Last Glacial Maximum, a period of time with little information for the Australian continent. The deposit also contains abundant vertebrate fossil material derived from owl pellets, accumulation and pitfall entrapment. Below the studied profile, large vertebrate remains are found but are not discussed here. No Holocene sedimentation occurred at the site examined in the cave, and the top of the sequence is capped with a layer that has been anthropologically disturbed and contains exotic Pinus pollen. Chronologies of the deposit were obtained using two dating techniques: single stage accelerator mass spectrometer (SSAMS) 14C analysis of 23 charcoal samples and optically stimulated luminescence (OSL) dating of quartz from 6 sediment samples. The 14C chronology is preferred to describe the history of the deposits since the OSL chronology, which consistently overestimates the associated radiocarbon dates, may be inaccurate due to complexities in calculating dose rates, and may in addition represent the timing of sediment deposition through the cave opening rather than sediment transport to the deposit site. Morphological analysis of single quartz grains and grain size analysis indicate different provenance that is confirmed through the geochemical analyses of bulk sediment. Major elements were measured by X-ray Fluorescence (XRF), trace and rare earth elements by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP-MS), and Neodymium isotopic ratios were obtained using a Thermal Ionisation Mass Spectrometer (TIMS). Our results indicate that the aeolian material deposited in Blanche Cave over the 40–14 ka cal BP period originated from different sources across South Australia, although Nd isotopes clearly indicate a close association with sediments of the Kanmantoo Group outcropping along the eastern portion of the Mount Lofty Ranges and the Padthaway Ridge further south, both being located to the NW and NNW of the cave. During the latter part of Marine Isotope Stage 3, conditions were wetter and windblown sediment came from the coastal region just north and south of the Coorong Lagoon, with winds originating from the north-northwest. At that time, woody taxa appear to have vegetated the landscape. During the drier phases, especially the Last Glacial Maximum, sediment came from further inland, thus suggesting a different predominant wind direction, more from the northwest. The deglaciation saw material originating from a more northerly direction.

Biochronology and paleoceanography of late Pleistocene and Holocene calcareous nannofossil abundances across the Arctic Basin

Late Pleistocene and Holocene stratigraphic distributions of calcareous nannofossils have been investigated in seven short cores raised from four major ridges in the Arctic Basin and in one core from the Norwegian Sea. Observed assemblages in the Arctic Ocean cores mostly represent the influence of Atlantic shallow waters. On the Gakkel and Lomonosov Ridges, a distinct cross-over in abundance occurs between Emiliania huxleyi and Gephyrocapsa spp. in the upper part of Marine Isotope Stage (MIS) 3. The lowest abundances of indigenous calcareous nannofossils occur in the southern Mendeleev Ridge core and in the two Alpha Ridge cores. These areas show a minor production of calcareous nannoplankton, probably because of the progressively diminishing influence of shallow Atlantic waters with the increasing distance from the Fram Strait gateway, the key conduit of shallow water inflow to the Arctic Ocean. It remains unknown whether or not the observed abundance patterns have been modified by glacial–interglacial scale changes in preservation. Obvious reworking becomes intensified around MIS boundaries.

Early MIS 3 glacial lake evolution, ice-marginal retreat pattern and climate at Sokli (northeastern Fennoscandia)

Lake development at Sokli, northern Finland, is traced through the analysis of diatoms and other siliceous micro-fossils in a 2-meter thick minerogenic, laminated clay-silt deposit dated to the early part of Marine Isotope Stage (MIS) 3. Fluctuating water levels and changes in lake extent depicted by the siliceous micro-fossil record, together with lithology, suggest that an important part of the sediment sequence was deposited in a glacial lake. The proxy-based glacial lake evolution is tested using a Digital Elevation Model and geomorphologic evidence including eskers dated to the early MIS 3 Tulppio Interstadial at Sokli. Despite the apparent ice-dammed nature of the lake, the sediment is relatively rich in fossils and there are limited signs of re-deposition of older fossil material. The siliceous micro-fossil record together with data from other proxies previously analysed in the same sediment samples provides a coherent picture of past environmental changes around the Sokli site. This is most probably due to the sheltered position of the coring-site in a lake embayment. Quantitative climate reconstructions based on the diatom record show mean July air temperatures as high as present-day values at Sokli, and the temperature ranges indicated by the diatom record are in agreement with temperature reconstructions based on chironomids. The position of Sokli in the northeastern portion of the central area of the Scandinavian glaciations and the northern retreat pattern implies that an important part of eastern Fennoscandia was deglaciated during the early MIS 3 warming event.

Climate‐driven changes in lake conditions during late MIS 3 and MIS 2: a high‐resolution geochemical record from Les Echets, France

A new set of geochemical data obtained from a long sediment sequence from the Les Echets basin provides a new record of palaeoenvironmental change for western Europe. The sequence covers the late part of Marine Isotope Stage (MIS) 3 and MIS 2 (c. 46.1–15.0 cal. kyr BP) and extends over 30 m of sediment, allowing for high sampling resolution. Distinct cyclic fluctuations in aquatic productivity proxies suggest a tempo of environmental change at Les Echets that resembles the one established for Dansgaard‐Oeschger cycles and Heinrich events. Increases in organic carbon are paralleled by high hydrogenous contents and enriched δ13Corg and Corg/Ntot ratios, implying a mixture of aquatic and land‐derived constituents. The stable isotope values are directly linked to primary aquatic productivity and the input of terrestrial organic matter, enriched during warm, productive, periods, and drastically depleted during cold periods, particularly Heinrich events. Phases of relatively high productivity correlate with Dansgaard‐Oeschger interstadials 8–2, while Heinrich events 3 and 2 are also clearly delineated by distinct lithological horizons with very low organic contents, high dry densities and enhanced organic matter oxidation. A large hiatus occurring about the time of Heinrich event 4 suggests that the cold and dry climate reconstructed for this event in the North Atlantic region also greatly affected Les Echets and its catchment.

Micromammals from the 1995 Mammoth Excavation at West Runton, Norfolk, UK: Morphometric data, biostratigraphy and taxonomic reappraisal

In this paper, the small mammals recovered from sediments associated with the West Runton Elephant have been analysed and compared with sites in other parts of Europe. Major taxonomical problems are indicated and we suggest ways of utilising such morphological complexity to refine biostratigraphical and chronostratigraphic attributions.The micromammal assemblage from the West Runton Elephant Site so far totals 16 species from the West Runton Freshwater Bed (WRFB). There are strong similarities with the arvicolid spectrum of basal layer H8 in the Koněprusy C 718 profile (Czech Republic), which accumulated under cooler conditions preceding the thermal maximum of an early Middle Pleistocene interglacial. Rare steppic indicators (e.g. Cricetus) at West Runton also imply a somewhat cooler and more continental climate than the present day, but overall the fauna is fully temperate in character. West Runton shares several stratigraphically significant small mammal taxa with Voigtstedt (Central Germany) and morphometric comparisons suggest that Voigtstedt may be slightly younger than West Runton. The presence of Mimomys savini, with a latest occurrence in the early part of Marine Isotope Stage (MIS) 15, together with the palaeomagnetic evidence suggests the WRFB may have been emplaced during the early part of MIS 17. However, given the complexity of the marine isotope curve during the early part of the Brunhes Chron and differences between global and regional climatic evolution, it is difficult to assign the normally magnetised WRFB to a particular Marine Isotope Stage (MIS).

A new stage 3 millennial climatic variability record from a SW France speleothem

We present a new high resolution speleothem stable isotope record from the Villars Cave (SW-France) that covers part of marine isotope stage (MIS) 3. The Vil14 stalagmite grew between ~ 52 and 29 ka. The δ 13C profile is used as a palaeoclimate proxy and clearly shows the interstadial substages 13, 12 and 11. The new results complement and corroborate previously published stalagmite records Vil9 and Vil27 from the same site. The Vil14 stalagmite chronology is based on 12 Th-U dating by MC-ICP-MS and 3 by TIMS. A correction for detrital contamination was done using the 230Th/ 232Th activity ratio measured on clay collected in Villars Cave. The Vil14 results reveal that the onset of Dansgaard–Oeschger (DO) events 13 and 12 occurred at ~ 49.8 ka and ~ 47.8 ka, respectively. Within uncertainties, this is coherent with the latest NorthGRIP time scale (GICC05-60 ka) and with speleothem records from Central Alps. Our data show an abrupt δ 13C increase at the end of DO events 14 to 12 which coincides with a petrographical discontinuity probably due to a rapid cooling. As observed for Vil9 and Vil27, Vil14 growth significantly slowed down after ~ 42 ka and finally stopped ~ 29 ka ago where the δ 13C increase suggests a strong climate deterioration that coincides with both North Atlantic sea level and sea surface temperature drop.

Paleolimnological response to millennial and centennial scale climate variability during MIS 3 and 2 as suggested by the diatom record in Les Echets, France

A 27 m long sediment sequence retrieved from the central part of the Les Echets basin in France has been analysed in sub-centennial resolution for biogenic silica and fossil diatom remains. The sequence corresponds to the later part of Marine Isotope Stage (MIS) 3 and to most of MIS 2. Distinct changes in diatom productivity, diversity and taxonomic composition between 36.2 and 31.7 kyr BP appear to relate to Dansgaard–Oeschger (DO) climate variability. Intervals characterized by low diversity, productivity and small-sized benthic diatom taxa are most likely a response to colder conditions in relation to DO stadials. In contrast, higher diversity, productivity and a high abundance of planktonic taxa indicate a response to warmer temperatures during DO interstadials. The time interval between 30.3 and 15.7 kyr BP is characterized by continuous low diatom productivity and a benthic dominated community with intermediate species richness, suggesting a transition to more stable conditions. Three time intervals with extremely low concentrations of diatom valves (46.1–36.2, 31.7–30.3 and 26.3–23.6 kyr BP) overlap with ages reported for Heinrich (H) events 4, 3, and 2. We speculate that the lake at Les Echets suffered from severe ecological stress as a response to H events. This is the first detailed study exemplifying the response of a lake, based on diatoms, to climate variability during late part of MIS 3 and most of MIS 2 in Europe.

An 85-ka record of climate change in lowland Central America

Drill cores obtained from Lake Petén Itzá, Petén, Guatemala, contain a ∼85-kyr record of terrestrial climate from lowland Central America that was used to reconstruct hydrologic changes in the northern Neotropics during the last glaciation. Sediments are composed of alternating clay and gypsum reflecting relatively wet and dry climate conditions, respectively. From ∼85 to 48 ka, sediments were dominated by carbonate clay indicating moist conditions during Marine Isotope Stages (MIS) 5a, 4, and early 3. The first gypsum layer was deposited at ∼48 ka, signifying a shift toward drier hydrologic conditions and the onset of wet–dry oscillations. During the latter part of MIS 3, Petén climate varied between wetter conditions during interstadials and drier states during stadials. The pattern of clay–gypsum (wet–dry) oscillations during the latter part of MIS 3 (∼48–23 ka) closely resembles the temperature records from Greenland ice cores and North Atlantic marine sediment cores and precipitation proxies from the Cariaco Basin. The most arid periods coincided with Heinrich Events when cold sea surface temperatures prevailed in the North Atlantic, meridional overturning circulation was reduced, and the Intertropical Convergence Zone (ITCZ) was displaced southward. A thick clay unit was deposited from 23 to 18 ka suggesting deposition in a deep lake, and pollen accumulated during the same period indicates vegetation consisted of a temperate pine-oak forest. This finding contradicts previous inferences that climate was arid during the Last Glacial Maximum (LGM) chronozone (21±2 ka). At ∼18 ka, Petén climate switched from moist to arid conditions and remained dry from 18 to 14.7 ka during the early deglaciation. Moister conditions prevailed during the warmer Bolling–Allerod (14.7–12.8 ka) with the exception of a brief return to dry conditions at ∼13.8 ka that coincides with the Older Dryas and meltwater pulse 1A. The onset of the Younger Dryas at 12.8 ka marked the return of gypsum and hence dry conditions. The lake continued to precipitate gypsum until ∼10.3 ka when rainfall increased markedly in the early Holocene.

The Last (Koy-Yukon) Interglaciation in the Northern Yukon: Evidence from Unit 4 at Ch’ijee’s Bluff, Bluefish Basin

The effects of predicted anthropogenic warming can be assessed in part by documenting responses to past warming events. One of the most pronounced warmings was the last interglaciation - stage 5 of the marine isotope record. A large multinational and multidisciplinary project (CELIA) was launched recently in order to gain detailed knowledge of the climate during stage 5. Several key exposures were identified by CELIA; one of them is Ch'ijee's Bluff on the Porcupine River, northern Yukon. Pollen, plant and insect macrofossils and stratigraphie evidence from Ch'ijee's Bluff show that the part of Ch'ijee's Unit 4 that is above and younger than Old Crow tephra (OCt) was deposited during an interval of climate warmer than present. When OCt was dated at 85 ka BP, the subsequent warming interval was presumed to be correlative with the early part of marine isotope stage 3. New dates on OCt show it to be 140-150 ka BP, and this means that the warm interval discussed here is more likely of stage 5 than stage 3 age. We apply the informal epithet, "Koy-Yukon interglaciation", to it and compare the Ch'ijee's Bluff Unit 4 sequence with other east Beringian sites that contain both Old Crow tephra and putative interglacial deposits.

A high‐resolution record of vegetation and climate through the last glacial cycle from Caledonia Fen, southeastern highlands of Australia

AbstractA blocked tributary has provided a rare site of long‐term sediment accumulation in montane southeastern Australia. This site has yielded a continuous, detailed pollen record through the last ca. 140 000 years and revealed marked vegetation and environmental changes at orbital to sub‐millennial scales. Radiocarbon and optically stimulated luminescence (OSL, or optical) ages provide some chronological control for the last ca. 70 000 years. Most of the sediment is inorganic but with well preserved pollen that accumulated under unproductive and probably largely ice‐covered lake conditions. The lake was surrounded by low‐growing plants with an alpine character. Exceptions include three discrete periods of high organic sedimentation in the basin and forest development in the surrounding catchment. The two major periods of forest expansion are related to the last interglacial and the Holocene, with the third, shorter period considered to represent an interstadial in the early part of Marine Isotope Stage (MIS) 3. The latter part of the last glacial period is characterised by abrupt sub‐millennial, amelioration events that may relate to documented global oscillations emanating from the North Atlantic. There are systematic changes through the record that can be partly attributed to basin infilling but the progressive reduction and regional extinction of some plant taxa is attributed to a long‐term trend towards climatic drying. Copyright © 2007 John Wiley & Sons, Ltd.

The Pleistocene glaciations of eastern Yorkshire: a review

SUMMARY The Pleistocene deposits of eastern Yorkshire and adjacent areas have been studied intensively for about 150 years, but numerous problems of dating and correlation remain. Holderness provides the British type site for deposits of the Last Glacial Maximum (the Dimlington Stadial, part of Marine Isotope Stage 2) here dated to between 18,500 and 13,000 radiocarbon years ( c. 23,000–15,000 calendar years) BP, but older glacial deposits are still very difficult to date precisely. An earlier Devensian glaciation of east Lincolnshire and south-west Yorkshire has been suggested, but remains uncertain. The most extensive pre-Devensian glacial deposit is the Basement Till of Holderness and other eastern coastal areas. This is overlain by the raised beach of the Ipswichian Stage (MIS 5e; 128,000–117,000 years ago) at Sewerby, by the pre-Ipswichian Calcethorpe Till at Welton-le-Wold, Lincolnshire, and by boulders weathered in interglacial conditions at Warren House Gill, Durham, so it was deposited during MIS 6 or an earlier cold stage. Late Devensian (MIS 2) amino-acid dates for marine shells from the Basement Till at Dimlington may be explained by intrusion during subglacial disturbance of the till’s upper layers by the Late Devensian glacier. In coastal areas of east Yorkshire, the Skipsea and Withernsea tills and their equivalents between Flamborough Head and the Tees Estuary are attributed to the Dimlington Stadial, and there is considerable evidence that they were deposited by a single surge of a two-tiered ice sheet. The lower (Skipsea) tier originated in south-east Scotland and north-east England, and the upper (Withernsea) tier from Lake District ice that crossed the Pennines via the Stainmore Gap and overrode the Skipsea Till glacier in the Lower Tees Valley area. Stainmore ice was also diverted southwards into the Vale of York. The patchy 'Older Drift' in the Vale of York (mainly grey till with Permian, Carboniferous and Lake District erratics) was also deposited by Stainmore ice flowing southwards, probably in MIS 12.

Boulders of MIS 5 age deposited by a tsunami on the coast of Otago, New Zealand

A series of elevated imbricated boulders were investigated on the Otago coastline, southeast New Zealand, through field surveying and optical luminescence dating. By using established hydrodynamic relationships of sediment transport the energy required to move the clasts was calculated and compared to the historic record of marine inundations of that coast. The boulders are platy in shape and are over 2 m long in some cases, and are sourced from a locally outcropping conglomerate unit which appears to be the only lithology on this section of coast that erodes to produce clasts of this size. It is estimated that the boulders were deposited by a tsunami between 2 and 3 m high during the latter part of Marine Isotope Stage 5. They therefore represent the first pre-Holocene tsunami deposit and one composed of large boulders described on the New Zealand coastline.