High-resolution Palynological Record Research Articles

Long-term ecological successions of vegetation around Lake Victoria (East Africa) in response to latest Pleistocene and Early Holocene climatic changes

Reconstructions of ecosystem dynamics in tropical East Africa during the latest Pleistocene and the Holocene provide important long-term ecological insights, but so far, only a few, sometimes incomplete terrestrial records exist. In this paper, we present a new high-resolution palynological record from the Lake Victoria basin, covering the period from 16,600 to 9000 cal yr BP, when Afromontane forests and tropical rainforests gradually replaced the savanna. We discuss this dataset in the context of published palaeoclimate data, TEX86 inferred temperature and δD leaf wax inferred precipitation records, to assess long-term ecological successions and their potential causes. By ca. 16,500 cal yr BP, the movement of the Afrotropical rainbelt, not only brought an increase in temperature and moisture into the Lake Victoria basin, but also promoted the spread of arboreal taxa, such as Celtis and Podocarpus, at the expense of the savanna. At that time, fires were prominent in the sparse Afromontane vegetation. Later from ca. 15,500–15,000 cal yr BP, temperature and humidity rose and Afromontane trees such as Olea and Macaranga spread slightly, while grasses were burning in the savanna. During the period from 13,250 to 10,700 cal yr BP, Afromontane vegetation dominated by Olea became more prominent and expanded towards the lowlands where the tropical rainforest or gallery forest established; however, the savanna only marginally retreated. An initial spread of tropical rainforests occurred from ca. 11,500–11,100 cal yr BP during the onset of the Holocene, when temperatures and moisture further increased. Subsequently, between 10,700 and 10,300 cal yr BP the tropical savanna was largely replaced by the tropical rainforest, while the Afromontane forest likely spread to higher elevations, similar to the patterns observed today. Our high-resolution record demonstrates the dynamic response of African tropical ecosystems to major temperature and humidity variations from 16,600 to 9000 cal yr BP, including some of the most important landscape transformations in East Africa in the past 20,000 years.

Late Eocene to late Oligocene terrestrial climate and vegetation change in the western Tasmanian region

While many palaeoclimate studies have focussed on the Eocene-Oligocene transition (EOT), little is known about the timing and drivers of the post-EOT climate recovery. To better understand and reconstruct terrestrial climate and vegetation dynamics from the late Eocene to late Oligocene (35.5–27.46 Ma), we use a new, high-resolution palynological record and quantitative sporomorph-based climate estimates recovered from ODP Site 1168 on the western Tasmanian margin. Late Eocene (35.50–34.81 Ma) floras reveal Nothofagus-dominated temperate forests with secondary Gymnostoma and minor thermophilic plant elements growing under wet conditions, with mean annual temperatures (MATs) of ∼13 °C. This is followed by a small decrease in terrestrial temperatures across the EOT by ∼2 °C. Apart from a slight decline in abundance of Gymnostoma, increases in the Fuscospora and Lophozonia-type Nothofagus, and the disappearance of palms (Arecaceae), vegetation remained relatively stable across the EOT. However, a prolonged interval of warm-temperate conditions after 33.0 Ma, independent of fluctuations in the current pCO2 record, imply additional regional controls on local climate. Changes in surface oceanographic currents, due to sustained deepening of the Tasmanian Gateway, may have played a significant role in sustaining warm-temperate vegetation in southern Australia post-EOT. The early Oligocene (PZ 3; 30.5–27.46 Ma) vegetation record still maintains the Nothofagus-dominated forest with a recovery in Gymnostoma. Gymnosperms (especially Araucariaceae, Dacrydium, and Podocarpus) and cryptogams expanded alongside an increase in overall species diversity. Sporomorph-based MATs averaged ∼11 °C in this interval. The expansion of cool-temperate forest (sustained cool-temperate climate conditions in our terrestrial records) matches the general declining pCO2 concentrations in the early Oligocene. The synchroneity between terrestrial and marine temperatures (MATs and SSTs gradually decline) and atmospheric pCO2 highlight the importance of pCO2 in driving terrestrial climate and vegetation change in the Tasmanian region during the early Oligocene.

Late Holocene environmental and hydro-climatic variability inferred from a shallow lake record, blowout dunes, Argentinian western Pampas, South America

The Pampas plains of southern South America were predominantly dry, eolian-shaped landscapes, besides some interposed humid phases, during most of the late Pleistocene-Middle Holocene, evolving to humid-subhumid grasslands hosting an increasingly large number of shallow lakes in the late Holocene. These lakes proved to preserve in their sediments worthy evidence to interpret past environmental-ecological conditions, offering tools to analyze climatic variability and human impacts during the last millennia. This is the case of the shallow lake Primera Laguna, located in the western and driest edge of the Pampas. Here, we present a multiproxy study from this shallow lake with the aims of contributing to reconstruct its past stages, infer the climatic scenarios that drove its evolution, evaluate the potential anthropogenic role in these changes, and correlate/analyze this record with available data from other Pampean lakes. We analyzed a high-resolution palynological record, accompanied by macroscopic charcoal accumulation rates, C/N, C and N stable isotopes, magnetic susceptibility, and sediment geochemistry, of a 41-cm long sediment core, extracted from the deepest sector of the lake. An age-depth model based on AMS chronology indicates a preserved lake history for the past ∼1400 cal yr BP. Ecological and sedimentological interpretations allowed us to propose four main periods during this time lapse. For the first period (1375–1069 cal yr BP, 575–881 CE), the integrative interpretation indicates a very low shallow lake –mostly oligotrophic, alkaline, and clear water–, dominated by the accumulation of epiclastic silty fine sand from the surrounded eolian landscape and covered by xerophytic vegetation. In the second period, between 1069 and 738 cal yr BP (881–1212 CE), we inferred a trend to rising lake levels and mesotrophic conditions, and more pollen taxa than the previous period, and with lake margins dominated by cattails and sedges. The third period (738–193 cal yr BP, 1212–1757 CE) was characterized by more variable and lower lake levels compared to previous periods and more frequent desiccation processes at the lake margins. Then, during the fourth period (last 195 cal yr, 1757–2015 CE), there was a gradual transition towards a larger and more stable shallow lake with a deeper water column, and under a turbid state probably related to eutrophication. From the comparison between Primera Laguna record and the previously studied Nassau shallow lake, located in the same eolian landscape, we found a synchronic evolution, implying common drivers of change in terms of climatic variability and human impact. Correlation with shallow lakes from the more humid belt of the Pampas suggests widespread increases of water availability in the region since ∼1500 cal yr BP, variable/lower lake levels during ∼600–200 cal yr BP, and a shift to positive hydrological balances up to the present highstands.

Role of climate and tectonism on the modernization of Patagonian floras: Evidence from the fossil record

A major reorganization of Patagonian ecosystems occurred when permanent ice sheets appeared in Antarctica and the Andean Range uplifted in southern South America. Rich plant communities dominated by Gondwanan trees and other species with tropical modern distribution vanished and those with cool and arid distributions rose to prominence. Rather than a single event, this landscape-level floristic replacement may have occurred as pulses following the paleoclimatic dynamism of the Coolhouse state (~34–4 Ma). However, the associated shifts in diversity and in climatically-key sensitive plant species have never been studied in detail so far. Here, we estimated richness using robust (non-parametric) methods and selected climatically-sensitive species to trace back past floristic trends in the high southern latitudes during the Coolhouse state. We used a high resolution palynological record from well-constrained Patagonian sediments from the Early Oligocene to the Late Miocene (~34–10 Ma), spanning most of the Coolhouse state. Our fossil data reveal the presence of five major floristic phases, closely linked with global climate states and regional orographic events. We found that diversity rises during global warming periods (↑100% at the Late Oligocene Warming Event or LOWE and ↑50% at the Miocene Climatic Optimum or MCO) and drops during glaciation periods (↓60% at Oi-1 (earliest Oligocene), ↓50% at Mi-1 (earliest Miocene) and ↓35% at Mi-3 (Middle Miocene) glaciation events) or intense tectonism (↓60% after the Andean uplift), relative to background levels. The representation of warm-demanding taxa peaked during LOWE and MCO, while arid-adapted taxa rose briefly during the MCO and took over following the major surface uplift of the southern Andes by 15–14 Ma. Humid-demanding species (e.g., tree-ferns) showed a general decreasing trend in abundance from their climax at 34 Ma to their minimum occurrence at 10 Ma. Our study reveals the potential of using robust statistical diversity methods in unraveling the relationship between past floras and climatic-orogenic forcing during the Coolhouse state.

Moisture and vegetation variations in the extremely cold-dry area of the Tibetan Plateau during the past 5000 years

Climate change on the Tibetan Plateau (TP) and its response to the atmosphere circulation has been widely concerned. The extremely cold-dry area of the central-northern TP is vulnerable and particularly sensitive to the variations of Indian Summer Monsoon (ISM) and the Westerlies. However, records from the central-northern TP are still scarce, limiting our understanding of the natural variability of climate on the TP and its response to the atmosphere circulation. Here we present a high resolution palynological record from Buruo Co covering the last 5000 years. The palynological assemblage shows that the Artemisia-steppe predominated the Buruo Co region until it was replaced by the alternant domination of steppe and desert since 900 cal a BP. Our results show that the central-northern TP experienced relatively warm and humid conditions reflected by Artemisia-steppe before 3800 cal a BP linked with stronger ISM. And then, the vegetation variation reveals a stepwise long-term aridification on the central-northern TP, which was influenced by the gradually weakened ISM during 3800–3200 cal a BP. Subsequently, the strengthened dry Westerlies dominated this region since 3200 cal a BP. After 1000 cal a BP, the Buruo Co might slightly expanded, but the catchment still maintained relatively dry conditions, even though this region probably received small amount of external moisture supply under the low evaporation conditions. Besides, four drought intervals (4400–4100, 3850–3650, 3300–3000 and 1900–1400 cal a BP) and two relatively cold periods (3200–2800 and 400 cal a BP-Present) were detected. The climate and vegetation variations since mid-Holocene on the central-northern TP were mainly controlled by the summer insolation at 30°N and the solar activity. Also, it was associated with the position of Intertropical Convergence Zone and the climate oscillations of the North Atlantic mediated by the synergistic effect of ISM and the Westerlies.

Early Pleistocene (Olduvai Subchron) vegetation and climate change based on palynological records from the Yinchuan Basin of northwestern China

Many recent studies focus on the relatively cold and humid interval during the Early Pleistocene Olduvai Subchron (1.95–1.77 Ma), but detailed environmental records for this interval are still rare. Here we present a high-resolution pollen record from the PL02 core (38°55′26.62″N, 106°36′3.82″E) from the Yinchuan Basin of northwestern China to reconstruct vegetation and infer climatic changes. Vegetation was dominated by desert steppe from 1.95 to 1.89 Ma suggesting a cold and dry climate. High percentages of Picea and Abies pollen indicate cold and humid conditions between 1.89 and 1.87 Ma while pollen percentages of broadleaved taxa increased rapidly between 1.87 and 1.84 Ma reflecting relatively warm and humid conditions. Palynological assemblages from 1.84 to 1.82 Ma reflect a colder and drier climate with an increase in xerophytic taxa and a decrease in conifers. Further increases of xerophytic taxa suggest a relatively cold and dry climate prevailed after 1.80 Ma. The new high-resolution palynological record suggests that environmental changes in the Yinchuan Basin are synchronous with global fluctuations. The inferred climate fluctuations show 20-kyr cycles during the Olduvai Subchron, supporting the view that climate changes in the study region were mainly controlled by orbital factors.

Pollen record in the northwestern continental shelf of the South China sea in the past 82 ka: Paleoenvironmental changes in the last glacial period

The northwestern continental shelf of the South China Sea (SCS) is in a geographic location that was sensitive to the global paleoenvironmental change during the last glacial period. Here we present a high resolution palynological record of Core ZBW (100.65 m in length) from the continental shelf of the SCS in the past 82 ka. In contrast to results for the northern SCS, the core’s pollen assemblage was dominated by arboreal trees between MIS5a and MIS1, even during the glacial period. Pollen provenance analyses indicated it was mainly from the drainage basin of the Red River, the Yungui Plateau and Tibetan Plateau. Between 66 and 64 ka, the contribution of Pinus fell while that of Cyclobalanopsis and trilete spores increased, indicating a drier and cooler climate. Conversely, during MIS3, the contributions of Pinus and lowland trees were high, indicating a warm and wet climate. The sedimentary environment in core ZBW alternated between coastal marine and river alluvial or shore facies. A sedimentary hiatus between 42 and 13 ka coincided with a significant fall in sea levels. Seismic data indicate that the Hainan paleo-river Delta (HPRD) process occurred at the core site between 65 and 56 ka, with extremely high rates of sediment deposition. Pollen data indicate the HPRD process was coincided with a transition period from cooler and drier climate to warmer and wetter climate, and lower sea levels to higher sea levels.

Of birches, smoke and reindeer dung – Tracing human-environmental interactions palynologically in sediments from the Nahe palaeolake

Sediments from the Nahe palaeolake in Schleswig-Holstein provided a continuous and high-resolution palynological record in the vicinity of a Lateglacial archaeological site in northern Germany. The principal objective of the study was to investigate potential reflections of Palaeolithic human-environmental interaction, which is generally regarded as challenging. Charcoal particle frequencies in different size classes and coinciding fungal spores reveal a remarkable pattern at the transition from the Dryas 3 to the Preboreal period that corresponds to the chronological attribution of parts of the archaeological record. The applied indicators of human action render it possible to define a temporally limited phase of generally elevated large charcoal particle inputs, reflecting potentially anthropogenic activity. The interpretation of the palynological record leads to the hypothesis that the climatically driven rapid change of the vegetation at the Pleistocene-Holocene transition caused temporally increased hunting activities by Late Palaeolithic hunter-gatherers. The excellent age control of the record allowed to date this phase between 11,650 and 11,520 cal yr BP.

High-resolution palynological record for vegetation and environment change during MIS 2 in the southern South China Sea

Abstract Vegetation evolution and corresponding climate changes during Marine Isotope Stage (MIS) 2 on the exposed shelves in the southern South China Sea (SCS) region are still controversial. Palynomorph data, including percentage, concentration, and influx were used to reconstruct the history of vegetation and environment changes during MIS 2 and MIS 1. It recommends three significant changes occurred during these periods at 21.51 cal kyr B.P., 17.82 cal kyr B.P., and 12.36 cal kyr B.P. The findings indicate that during MIS 2 and the start of MIS 1, the northeastern part of exposed shelves were covered with tropical rainforests. Ferns were present in ground flora and sub-canopy of tree cover in the rainforests. In the coastal areas, mangrove forests survived up to the start of MIS 1 and then disappeared due to the rapid rise in sea level. Grassland was present to a limited extent and probably in the beach areas only. Winter monsoon was strong, although the temperature was lower than at present. From 11.70 cal kyr B.P., ferns were the dominating vegetation while herbs disappeared completely. Trees of lower and upper montane rainforests were present to some extent. The climate was warm, sea level rose, the continental shelf was submerged in the ocean, and the summer monsoon became stronger than in previous times. This study supports the previous works from the southern SCS region and suggests that a combination of pollens with other proxies give a better understanding of vegetation and climatic dynamics in the past.

When flowering plants ruled Antarctica: evidence from Cretaceous pollen grains.

The replacement of seed-free plants and gymnosperms by flowering plants during the Cretaceous is one of the most important biotic events in the evolution of life. However, the magnitude of this global turnover remains largely unknown. Here we present sampling-standardized diversity estimates from a high resolution palynological record of the Late Cretaceous (85-66Ma) from Antarctica, in the context of the past climatic events. Our fossil evidence reveals the occurrence of a rich Campanian flora peaking at c. 80Ma, with angiosperms as the most diverse group of plants for the first time in Antarctica. This peak of diversity was followed by a period of a stepwise deterioration; 60% of ferns and 40% of gymnosperms became locally extinct from the early/mid-Campanian to the late Maastrichtian. Although angiosperms also faced several extinctions - 25% became extinct - they were far less affected than nonangiosperms. The onset of deterioration of the greenhouse conditions at the end of the Cretaceous - low CO2 and global cooling trends - would have led to our observed pattern of change. Overall, our study reveals the beginning of a profound floristic turnover in the highest southern latitudes that pre-dates the major extinction event of the end of the Cretaceous by 15Myr.

Treeline composition and biodiversity change on the southeastern Tibetan Plateau during the past millennium, inferred from a high-resolution alpine pollen record

Climate variability has been impacting the terrestrial ecosystems. However, some important processes relating to the response of vegetation to climate change in alpine regions, such as treeline composition and associated plant diversity change, have not been well understood in terms of multi-centennial scales. Here, we present a well-dated high-resolution palynological record from Basomtso, southeastern Tibetan Plateau (TP), to discuss the vegetation change and the relevant climate forcing. Our results manifest that the treeline position, composition and plant diversity around Basomtso did change greatly during the past millennium. The cold events (ca. 720-650 cal yr BP and ca. 400-50 cal yr BP) were considered crucial to force these changes. Cold temperature limited the growth of trees in the high elevations and thus led to downslope movement of treeline and conspicuous decrease of dominant tree species. Space and resource released from the upper forest triggered shrub and herb taxa expanded to lower elevations and even new species can dispersed to this area and survived, leading to changes in vegetation composition and diversity. Although the climate warming is pronounced since the 20th century, treeline distribution, vegetation composition and species diversity seem have not been recovered from the previous cold period. And the vegetation succession in the mountains of the southeastern TP will probably develop slowly in the coming decades. Our results highlight the need for long-term climate and vegetation monitoring and analysis in order to better understand the regional dynamics of treeline movement and plant diversity change during climate transition period.

Vegetation and climatic changes during the Middle Miocene in the Wushan Basin, northeastern Tibetan Plateau: Evidence from a high-resolution palynological record

There remains no detailed record of the Middle Miocene vegetation and climatic changes which occurred in central Asia and their possible driving mechanisms. This is because there is still a lack of high resolution records. Here, we present a sporopollen record from the Wushan Basin on the northeastern Tibetan Plateau, central Asia, spanning the period ∼16.1–13.6Ma. The sporopollen record shows that a dense mixed forest growing in rather warm and humid climatic conditions was affected by a general drying trend during the period ∼16.1–15Ma. It demonstrates that although the climate was generally warm and humid during the Middle Miocene Climate Optimum (MMCO), it was also a time of climatic instability. The dense forest gave way to an open forest in response to a less humid climate between ∼15 and 14.4Ma. Dense mixed forest made a return with an increasingly humid climate during ∼14.4–13.8Ma. This vegetation and climatic succession could be associated with global cooling, or more particularly, a higher temperature rebound set against the background of a long-term cooling trend. A more open forest appearing in response to drier and colder climatic conditions dominated the study area during the ∼13.8–13.6Ma period. This could be compared to the rapid global cooling event Mi-3b. This significant global cooling event exerted a major impact on terrestrial vegetation, climate and biota. Our high resolution sporopollen record demonstrates that global climate changes could have been the first order driving force for the Middle Miocene vegetation and climate changes seen in the Wushan Basin in central continental Asia, with the tectonic uplift of the Tibetan Plateau probably playing a subordinate role.

High-resolution palynological record of Holocene climatic and oceanographic changes in the northern South China Sea

For the first time, palynological records of terrestrial palynomorphs and dinoflagellate cysts are investigated in a sediment core from the northern South China Sea (SCS) covering the last 12,500years. Both terrestrial and marine palynomorph records show strong signals of the sea-level change during the studied interval. The highest herb pollen content was associated with extensive grasslands on the exposed shelf at the low sea-level stand during the Younger Dryas and early Holocene. The increase in fern spores and decrease in concentrations of dinoflagellate cysts and terrestrial palynomorphs was observed during the sea-level rise interval from 12,500 to ~6800 (or 6000) calyr BP. Then, the sea level became stabilized and consistently low dinoflagellate cyst abundances and high abundances of fern spores were recorded.A high abundance of Impagidinium in the period ~12,000–10,400calyr BP possibly resulted from increased input of western Philippine Sea waters into the SCS and the branching of the Kuroshio Current. A short-term decrease of Impagidinium at ~11,700–11,000calyr BP corresponding to the MWP-1B event might be associated with input of the East China Sea waters through the Taiwan Strait.The relationship between the sedimentation rates and the concentrations of terrestrial palynomorphs indicates a water-dominant transport for pollen and spore dispersal prior to ~6300calyr BP, whereas wind transport became more prominent thereafter. The timing of this change corresponds to the highest sea-level stand at ~6800–6000calyr BP, when the present oceanographic setting was formed. The mid-Holocene Optimum can be seen by the highest abundance of subtropical-tropical broad-leaved arboreal pollen and by the highest abundances of Dapsilidinium pastielsii. Three strengthened winter monsoon intervals at ~5500calyr BP, 4000calyr BP, and 2500calyr BP are reflected by increases in Pinus pollen content after the present oceanographic condition formed.

Palaeoenvironmental change in Southern Patagonia during the Lateglacial and Holocene: Implications for forest refugia and climate reconstructions

A high-resolution palynological record from Punta Yartou, Fuego-Patagonia (53°51′S; 70°08′W), supported by lithostratigraphy, radiocarbon dating and tephrochronology, was examined to reconstruct the vegetation changes during the last glacial–interglacial transition and the Holocene. Following deglaciation from the Last Glacial Maximum sometime before c. 23,070 Cal yr BP the vegetation was initially dominated by Ericaceous shrubs and following modest climate amelioration between c. 20,480 and 14,820 Cal yr BP the environment favoured the spread of Acaena. The trend to a warmer and more humid climate was interrupted between c. 14,820 and 13,560 Cal yr BP when the vegetation community was dominated by cold tolerant herbs such as Poaceae and Asteraceae (Subfamily Asteroideae), suggesting an open treeless landscape with colder climatic conditions coeval with the Antarctic Cold Reversal. After c. 13,560 Cal yr BP a gradual rise in temperature and humidity is inferred from the colonisation of Nothofagus. A further warming and increase is inferred from the establishment of the forest/steppe ecotone by c. 12,900 Cal yr BP. The early Holocene was then characterised by increasing development of Nothofagus open canopy forest. However, between c. 8080 and 5060 Cal yr BP there was a significant reduction in the forest cover and high values of charcoal which suggest an intense arid phase leading to increased availability of dry fuel. Between c. 5060 and 2170 Cal yr BP there were centennial-scale periods of increased wetter and colder climatic conditions. The Punta Yartou record demonstrates the sensitivity of Fuego-Patagonian forest to changes in the proximity and intensity of the southern westerly winds.

Late Pleistocene palynological sequence from Ohalo II, Sea of Galilee, Israel

A new high-resolution palynological record from the Sea of Galilee (Israel), roughly spanning the Last Glacial Maximum (LGM) obtained from a trench dug in the vicinity of the well-dated prehistoric site of Ohalo II (23–24 ka cal. BP) — combined with detailed litho-stratigraphic and magnetic susceptibility analyses — provides evidence of vegetation, lake levels and climate change in the northern Jordan Valley. The sequence begins with laminated marls of the last Lake Lisan high stand and ends with the near-shore deposits containing the prehistoric site. Palynologically, the early phase of the high stand (pollen zone 1) is characterised by high-AP (mainly Quercus ithaburensis), reflecting a relatively humid climate. During its later part (zone 2), the increase in Artemisia indicates a regional drying. Several fluctuations in lake levels and humidity are recorded (pollen zones 3–4) prior to human occupation at the prehistoric camp, during a renewed humid climate (pollen zone 5); in its early phase Quercus calliprinos spread again in the mountainous areas around the lake, while the maquis of the later phase was typified by the deciduous Q. ithaburensis. The fact that a variety of data sets were retrieved from the very same section renders their correlation and combined environmental interpretation reliable and unique for this time period in the southern Levant. The reconstructed palaeoenvironmental picture indicates a rather mild LGM in the northern Jordan Rift. Although there are 17 14C and U-Th dates from the studied section, dating inconsistencies prevent direct correlations between the observed regional fluctuations and global events.

Changes in Holocene climate and the intensity of Southern Hemisphere Westerly Winds based on a high-resolution palynological record from sub-Antarctic South Georgia

Sub-Antarctic South Georgia is a key region for studying climate variability in the Southern Hemisphere, because of its position at the core of the Southern Hemisphere Westerly Wind belt and between the Antarctic Circumpolar Current and the Polar Frontal Zone. Here, we present a 5.8-m long high-resolution pollen record from Fan Lake on Annenkov Island dominated by local sub-polar vegetation, with Acaena and Poaceae being present throughout the last 7000 years. Palynological and sedimentological analyses revealed a warm late Holocene ‘climate optimum’ between 3790 and 2750 cal. yr BP, which was followed by a gradual transition to cool and wet conditions. This cooling was interrupted by slightly warmer environmental conditions between 1670 and 710 cal. yr BP that partly overlap with the Northern Hemisphere ‘Medieval Climate Anomaly’. Increases in non-native and long-distance pollen grains transported from South America (e.g. Nothofagus, Podocarpus) indicate that stronger Southern Hemisphere Westerly Winds over South Georgia possibly occurred during some ‘colder’ phases of the late Holocene, most notably between c. 2210 and 1670 cal. yr BP and after 710 cal. yr BP.

Palynological evidence for the latest Oligocene−early Miocene paleoelevation estimate in the Lunpola Basin, central Tibet

Uplift of the Tibetan Plateau is ultimately driven by the Cenozoic collision between the Indian and Eurasian plates and their continued convergence. One approach for studying the Tibetan Plateau uplift is to verify the paleoelevation changes from collision to present day. This is important for understanding both the tectonics and the climatic effects. The new high resolution palynological record of the uppermost Oligocene to the lowest Miocene strata from the Lunpola Basin indicates that the vegetation types during the latest Oligocene–earliest Miocene were dominated by mixed coniferous–broadleaved forests being different from the modern steppe vegetation. By using the Coexistence Approach to the fossil pollen records, after calibration the effects of temperature difference and the lapse rate, a maximum paleoelevation of 3190±100m asl was estimated in the Lunpola Basin in the latest Oligocene–earliest Miocene, being 1500 to 2000m lower compared with the previous oxygen isotope paleoelevation in the same region.

Millennial-scale variability in Southern Hemisphere westerly wind activity over the last 5000 years in SW Patagonia

Here we report results from a high-resolution palynological record and stratigraphic/geochronologic data related to a Neoglacial event in Torres del Paine National Park, southern Chile (51°S, 71°W), to investigate climatic variations in Southwest Patagonia during the last 5000 years. The record reveals a stepwise expansion of Nothofagus-dominated woodlands and forests with discrete pulses at 4400, 2900, 1300, and 570 cal yr BP. Superimposed upon this trend we identify a relative opening of the woodlands between 4100–2900 and 2300–1300 cal yr BP. Closed-canopy forests dominated the landscape between 570–60 cal yr BP, followed by a rapid decline at the end of the 19th century that coincided with intense fire activity and the appearance of Rumex cf. acetocella, an exotic species introduced by European settlers. We interpret these changes as variations in the intensity and/or position of the southern margin of the westerly winds, which culminated with a net eastward shift of the forest–steppe ecotone during the Little Ice Age. We propose that millennial-scale changes in either the latitudinal position and/or the overall strength of the southern westerlies may be responsible for vegetation changes, fire occurrence, and the dynamic behavior of Patagonian glaciers during the last 5000 years. Because the modern maximum in near-surface wind velocities and precipitation is located between 48° and 50°S, we suggest that the core of the southern westerlies may have achieved this modern position ∼570 years ago.

High resolution Holocene palynological record from the Scotian Shelf

Because of their location at the confluence of polar and subtropical airmasses and near a transition zone between the cold Labrador Current and the Gulf Stream, the Atlantic Provinces experience some of the most dynamic climate conditions in Canada. Major climate changes occurred during the Holocene, as shown by pollen records from lakes, but previous paleoceanographic studies, based on low-resolution proxy-data records do not show major changes during the past 8000 years. Therefore, the Holocene history of Canada's Atlantic region was examined using a high-resolution palynological record from the Scotian Shelf (La Have Basin). Sea surface conditions were reconstructed using proxy-data from dinoflagellate cysts and paleobioclimatic transfer functions. Ocean–atmosphere interactions are determined by onshore–offshore correlation of marine and pollen records from Nova Scotia. Results show a succession of major paleoceanographic events. Sea surface temperatures (SST) (February and August) up to 5°C higher than today's average and slightly higher salinity are reconstructed between 10.5 and 8.5 ka. The last pulse of meltwater from the residual ice sheet affected the shelf waters between 8.5 and 6.5 ka by lowering the SST (in February) and the salinity. Most previous studies failed to record this event. Since 6.5 ka, August temperature generally remained around today's value, while February temperature was generally 2°C above it, except for recurring colder and lower salinity intervals. These cold intervals have a recurrence of about 1000 years. A slight cooling of summer SST is recorded in the last 500 years. Comparison with climatic reconstructions from Nova Scotia pollen records shows a difference in timing between ocean and atmosphere. The onset of the climatic optimum (hypsithermal) in Nova Scotia lags by about 2000 years (until 8 ka) relative to the ocean but it lasted longer. The Neoglacial cooling in Atlantic Canada however, started earlier (2 ka) than the late Holocene ocean cooling. La Have Basin's Holocene paleoceanography presents some differences from most other studies from the region: (1) the hypsithermal started earlier; (2) the last pulse of meltwater is recorded; (3) the last 6500 years are punctuated by colder intervals. Increased productivity and blooms of toxic algae in the early Holocene are probably due to a combination of factors: increased nutrients and a greater stability of the water column because of meltwaters, higher SST and increased upwelling or storm activity.

Direct land/sea correlation of the Eemian, and its comparison with the Holocene: a high-resolution palynological record off the Iberian margin

Abstract High-resolution pollen, dinocyst and isotopie profiles covering the marine isotope stage 5 (MIS 5) are presented from core MD952042 (Tagus abyssal plain, 37°47'N, 10°09'W). Both marine and terrestrial proxies indicate the occurrence of a Bølling-Allerød-Younger Dryas-like event at the beginning of MI substage 5e. The terrestrial Eemian stage coincides with both the lightest oxygen isotope values of substage 5e and the heavier ones approaching the 5e/5d transition. Accordingly, the Eemian is not equivalent to MI substage 5e, as the Holocene is not equivalent to MIS 1. Remarkably, both pollen and dinocyst data reflect the same climatic pattern on land and ocean, and they evidence a succession of climatic events that the isotope signal does not identify. The Eemian began with a Mediterranean vegetation that was gradually replaced by Eurosiberian formations indicating a change from Mediterranean to oceanic climates. In the middle of the Eemian, warming conditions were interrupted by an event corresponding to a slight cooling resulting from an increase in precipitation over land and ocean. Finally, a warming trend characterised the last phase of the Eemian. The occurrence of small climatic changes during this interglacial is inconsistent with the dramatic variability suggested by the GRIP ice-core record.