Pollen Zones Research Articles

Палинологическое обоснование стратиграфического расчленения и корреляции отложений беловежского горизонта плейстоцена Беларуси

The Belovezhian stage is a part of the Middle Pleistocene of Belarus. It is located between the Narevian and Berezinian glacial stages and consists of three substages: Borkovian, Nizhninian and Mogilevian. Belovezhian stage corresponds to the Muchkapian one in the stratigraphic scheme of the Pleistocene of the European part of Russia, which is also subdivided into the Glazovian, Podrudnyanian and Konakhovian substages and located between the Donian and Okian glacial stages. Generalization and analysis of the results of accumulated palynological and geological studies indicate that the Borkovian, Nizhninian and Mogilevian substages can be assigned a higher status — stages. Arguments in favor of such a division are presented in this paper. This point of view was repeatedly expressed earlier, but was not accepted in the modern stratigraphic scheme of the Pleistocene of Belarus. Another topical issue of the stratigraphy of this part of Pleistocene, considered within this article, is the validity of the Korchevian substage within the Narevian glacial stage. According to the available palynological data, the deposits of the Korchevian substage are characterized by a similar sequence and features of pollen zones as the Mogilevian accumulations within the Belovezhian stage, and therefore their age should be determined as Mogilevian. To substantiate the conclusions, a detailed interregional correlation of the studied deposits with the corresponding deposits of other regions of Europe by pollen zones was carried out and presented in this article.

Miocene evolution of vegetation, climate, and elevation in the Wulan Basin of northeast Tibetan Plateau based on a CRACLE analysis of palynological assemblages

The uplift of the Tibetan Plateau (TP) during the Cenozoic has played a pivotal role in shaping global climate and vegetation evolution, however, understanding the uplift history of its various tectonic blocks remains complex. In this paper, we analyze palynological samples from the Miocene Xiayoushashan and Shangyoushashan formations in the Wulan Basin to explore the relationship between climate change and TP uplift. The analysis identified four distinct pollen zones: Zone I (18–15.3 Ma) characterized by Artemisia-Lycopodium-Aster-Polygonaceae; Zone II (15.3–12.7 Ma) dominated by Pinus-Picea-Aster-Artemisia; Zone III (12.7–11.7 Ma) featuring Lycopodium-Picea-Pinus-Polygonaceae; Zone IV (11.7–8.7 Ma) characterized by Picea-Chenopodiaceae-Lycopodium-Artemisia. Results indicate that the whole study interval was dominated by shrubs and grasses, interspersed with conifers and broad-leaved trees, exhibiting an altitudinally zonal pattern. Using the Coexistence Likelihood Estimation (CRACLE) method, we estimate a mean annual temperature (MAT) ranging from 6.0 to 14.7 °C and a mean annual precipitation (MAP) between 919.1 and 1612.4 mm during Miocene times. While minor climatic fluctuations occurred, the region experienced a cool-temperate and sub-humid climate significantly warmer and more humid conditions compared to the present. Based on MAT differences, the paleoelevation of the Wulan Basin during the Miocene was estimated to be c. 1655–2025 m, suggesting an uplift of c. 1275–1645 m since that time. These findings corroborate previous suggestions that the northeastern TP had not reached its current elevation prior to the Late Miocene.

A Holocene fire history from Terra Nova National Park, Newfoundland, Canada: vegetation and climate change both influenced the fire regime

Fire is the largest natural disturbance factor in the boreal forest and plays a critical role in the composition, structure, and succession of stands and landscapes. The island of Newfoundland, located in eastern Canada, is subjected to a greater maritime influence, which may result in longer fire return intervals. The limited data on the fire regime does not account for interactions between fire, vegetation, and climate throughout the Holocene. We used sediment cores from Arnold’s Pond, Terra Nova National Park, which covered the last ~11,800 cal. yr BP, to investigate these interactions. We recognize 4 pollen zones and macroscopic charcoal analysis detected 45 local fire events. The 250-year mean fire return interval associated with the current vegetation is longer than a previous estimate for the park, but significantly shorter than other estimates for the island. Our mean fire return interval is within the range of fire estimates from Québec with similar vegetation. Our results suggest that the fire regime was primarily influenced by vegetation and climate. The transition to an open forest from a shrub tundra resulted in increased fire activity and fire frequency, which were likely driven by additional fuel on the landscape, but could have also been influenced by unknown climatic factors. We identified several examples of changes in the fire frequencies and/or charcoal accumulation that coincided with regional climate shifts, but we also identified a non-synchronous change. The non-synchronous shift to drier conditions resulted in a ~500-year time lag between peak Pinus strobus abundance and maximum fire frequency. Synchronous shifts in fire activity and/or fire frequency coincided with the 8200 event, Medieval Climate Anomaly and Little Ice Age. We also noted a decrease in fire frequency between 2600–1500 cal. yr BP that coincided with similar changes in the fire frequency from ~3000–1000 cal. yr BP in Québec. Our study highlights the complex interactions influencing the fire regime in our study area during the Holocene.

Pollen signal of modern vegetation registered in surface soil samples along an elevation gradient from Iztaccíhuatl volcano, central Mexico

AbstractCharacterising the vegetation-pollen signal is a crucial task for enhancing the interpretation of fossil pollen records. This study analyses 28 surface soil samples collected in the surroundings of Iztaccíhuatl volcano, between 2,650 and 4,024 m asl. Pollen zones and ordination analysis were assessed to establish a qualitative connection between the pollen signal and the distribution of plant communities along the elevation gradient. The results show: (i) the predominant pollen type in the pollen assemblage is Pinus; (ii) pollen grains of Quercus and Alnus are present along the elevation gradient, even at high elevations where the parental plants are not typically found; (iii) samples taken between 2,650 and 3,338 m asl., where fir forests dominate, exhibit higher values of Abies pollen compared to samples above 3,405 m asl.; (iv) the locally-dispersed pollen of the hemiparasite Arceuthobium results key in identifying the presence of pine forests; and (v) pollen taxa such as Apiaceae, Eryngium, Valerianaceae, and Caryophyllaceae are linked to higher elevations, specifically where the plant communities of Pinus hartwegii and alpine grassland occur. The study suggests that the pollen signal along the elevation gradient is useful to characterise the main plant communities of the study site (fir forest, pine forest and alpine grassland). Additionally, the percentage variations of Abies in the pollen signal below 3,600 m asl. show the reduction of fir forest communities resulting from recent human activities in the area.

Chronology and main stages of vegetation development in the central region of the East European Plain during the Mikulino interglacial

The chronology of the Mikulino Interglacial and its individual phases have been the subject of discussion. The goal of this study was to evaluate the time limits of the main stages of the Mikulino Interglacial on the Russian Plain according to ²³⁰Th/U dating and paleobotanical studies of lake and peat sediments from the known sections located within the Tver region on the Bolshaya Dubenka River, Malaya Kosha River, Granichnaya River, and Sizhina River (“Kileshino-2” section). An improved geochronological approach has been applied to identify layers suitable for the ²³⁰Th/U isochronous approximation. In combination with pollen and carpological studies of the deposits, this made it possible to date units corresponding to relatively narrow time intervals in the development of plant formations at different stages of the Last Interglacial. New paleobotanical studies of buried lake and peat sediments from the sections located on the Bolshaya Dubenka River, Malaya Kosha River, and Granichnaya River allowed us to restore the vegetation development during the Mikulino Interglacial in the interval of pollen zones M1–M7, i.e., more pollen zones have been analyzed and in greater detail than in 1960–1970. A chronological scheme of the main stages of vegetation development in the Mikulino Interglacial is proposed based on the results of ²³⁰Th/U dating and paleobotanical studies of organic-rich deposits from the Tver region sections in combination with previously published data obtained for the “Nizhnyaya Boyarshchina” section from the Smolensk region. The Mikulino Interglacial had begun about 130–126 kyr ago. Its first phase, corresponding to the M2 zone, ended ca. 118 kyr ago. The pre-optimal stages of vegetation development (M3 and M4 zones) fit into the time range of ca. 118–112 kyr ago. The climatic optimum of the interglacial (M5 and M6 zones) began ca. 112 kyr ago and ended ca. 100 kyr ago. The duration of the Mikulino Interglacial was probably at least 25 thousand years.

Stratigraphy and OSL chronology of the Middle–Upper Pleistocene sedimentary sequence and vegetation history during Late MIS6–MIS5e in the Neva Lowland (St. Petersburg region, Russia)

ABSTRACTThe quarry of the Sverdlov (Etalon) Factory stands out as a unique site in the northwest of the East European Plain since it exposes an almost complete Upper Pleistocene stratigraphic succession. Previous investigations have revealed a sequence of marine sediments deposited during the whole Mikulino Interglacial [Eemian, Marine Isotope Stage (MIS)5e], but the chronology of the Late Pleistocene deposits remains incomplete and requires further update. We present a study of the Middle–Upper Pleistocene units exposed in the Sverdlov Factory quarry by using geological methods, optically stimulated luminescence (OSL) dating and pollen analysis. The lower part of the Sverdlov Factory section comprises glaciomarine/glaciolacustrine varves, which accumulated during degradation of the Late Moscow (Late Saalian, Late MIS6) glaciation and correspond to pollen zone M1 (lower peak of Picea). They are covered by interglacial marine clayey silt that includes all Mikulino regional pollen zones M2–M8. According to a Bayesian model based on K‐rich feldspar luminescence ages, the interglacial marine deposition started 133 ± 8 ka ago and ended 109 ± 7 ka ago. The marine sediments are overlain by lacustrine silt with a K‐rich feldspar age of 119 ± 7 ka, lacustrine/alluvial sand with plant detritus formed 47–41 ka ago, and lacustrine sand and silt without organic matter accumulated ~39 ka ago. The upper part of the section is composed of subglacial till formed during the Late Valdai (Late Weichselian, MIS2) under the Scandinavian Ice Sheet and glaciolacustrine varved deposits of the Baltic Ice Lake. Two ages were acquired using quartz OSL from these varves, 16.9 ± 1.6 and 15.7 ± 1.0 ka, which are assumed to slightly overestimate the true age.

Environmental changes in the Eastern Arctic during the Early Gelasian Age: Palynological Data from Lake El'gygytgyn

The 2.373-2.510 Ma BP (isotopic stages 92-99; Early Gelasian Age) interval of the palynological record from Lake El'gygytgyn, northern Chukotka, includes 9 pollen zones characterizing interglacial, interstadial, and glacial plant communities. The boundaries of pollen zones and isotope stages in some cases do not correspond, indicating that the age model developed for the El'gygytgyn core requires revision. Between 2.373 and 2.510 Ma, the warmest climate occurred during MIS93, when larch forests, which included dark coniferous species, spread across the region. Alnus hirsuta (Spach) Turcz. ex Rupr., Chosenia arbutifolia (Pall.) A. K. Skvortsov, and Populus suaveolens Fish. dominated the gallery forests of the river valleys. The development of grass-shrub tundra and larch forest-tundra is associated with periods of climatic cooling, with the coolest conditions occurring at the beginning of MIS97. The consistent presence of Larix pollen throughout the Early Gelasian indicates that even in harsher climatic conditions, larch forest-tundra persisted in the areas of the Anadyr Plateau and Lake El'gygytgyn.

Boreal (Eemian) Transgression in the Northeastern White Sea Region: Multiproxy Evidence from Bychye-2 Section

Reconstructing interglacial marine environments helps us understand the climate change mechanisms of the past. To contribute to this body of knowledge, we studied a high-resolution 455 cm-thick sediment sequence of the Boreal (Eemian) marine beds directly overlying Moscovian (Saalian) moraine in the Bychye-2 section on the Pyoza River. We analyzed lithological and microfossil (foraminifers, ostracods, pollen, aquatic palynomorphs) variations at the studied site. Stratigraphical zonation is based on the local and well-established regional pollen zones, correlated with the western European pollen zones. The studied marine beds accumulated from the end of the Moscovian glacial (>131 ka) until ca. 119.5 ka. We distinguished three successive phases: a seasonally sea-ice-covered, relatively deep, freshened basin in the initial rapid flooding stage (>131–130.5 ka); a deep basin in the maximum flooding phase with less extensive sea ice cover (130.5–130.25 ka); and a shallow basin with reduced sea ice cover (130.25–119.5 ka). According to a pollen zone comparison with other sites, the regional glacioisostatic rebound started ca. 130 ka. The diverse warm-water assemblages of benthic foraminifers and ostracods containing typical Baltic Sea species occurred during the regression, mainly 128–124 ka, thus giving evidence for a relatively long-lasting connection between the White and Baltic Seas.

Palynology of Lake Motykino in the Holocene (Vologda region, Northwestern part of European Russia)

This work is dedicated to studying the dynamics of vegetation and natural-climatic conditions in the Mologo-Sheksninskaya lowland in the north of the East European Plain during the Holocene. Lake Motykino, located in the Darwin Nature Biosphere Reserve, was chosen as the research object due to its unique location and preservation of relic lake deposits. Radiocarbon dating and pollen analysis were conducted. The research results are presented in the form of a lithological description of the sediment column, stratigraphic analysis, and a pollen diagram divided into five local pollen zones, reflecting the succession of plant communities from periglacial landscapes in the Late Glacial to the formation of boreal forests in the Holocene. Analysis of pollen spectra allowed for the identification of key periods in the vegetation history of the region, from 13,300 cal BP to 400 cal BP, and to track changes in vegetation composition and peat formation processes.

Environmental Changes in the Eastern Arctic during Marine Isotope Stages 80 and 81

Palynological analysis of a 317-m-long sediment core obtained from Lake El'gygytgyn (67° 30' N, 172° 05' E) located in the Eastern Arctic documents the changes in vegetation between 2.103 and 2.146 Ma. This interval encompasses marine isotope stages (MIS) 80 and 81 and includes the Reunion paleomagnetic event, an important chronological event within MIS 81. Seven pollen zones depict the varying plant communities associated with interglacial, interstadial, and glacial intervals. The warmest climatic conditions occurred during MIS 81 (pollen zone E2) when coniferous forests dominated the landscape. These forests also included moderately thermophilous broadleaf trees and shrubs. The interstade (MIS 81, pollen zone E3) is characterized by open larch forests and forest-tundra. During the period of deepest climatic cooling, which occurred at the end of MIS 80 (pollen zone E7), larch forest-tundra and shrub tundra were present across the region. The palynological analysis of sediments from Lake El'gygytgyn illustrates the varying responses of vegetation to a wide range of climatic conditions and suggests that modern Arctic communities may disappear in the future as a result of global warming.

Растительные сообщества Восточной Арктики в изотопные стадии 50-59

Palynological analysis of sediments from Lake El'gygytgyn, formed during oxygen-isotope stages 50-59, documents the changes of cold stages, interstades and interglaciations. Ten pollen zones were identified and correspond to the interval 1.4920-1.6975 million years ago. This interval includes the Gilsa magnetic event (1.68 Ma), which is an important chronological landmark. Larix pollen appears in the palynological spectra of all stages. The presence of this taxon during warm climates indicates that larch forests established in the areas of the Anadyr Plateau and Lake El'gygytgyn and replaced the larch forest-tundra, which is characteristic of the cold stages. The warmest climatic conditions occur in pollen zone 6 (MIS55) and are in the range of 1.4920-1.6975 million years ago. Vegetation in the period of maximum cooling is characterized by pollen zones 7-10 (MIS50 - MIS54). The interval 1.4920-1.6975 million years ago represents the last step in the completion of the Quaternary vegetation history from a unique region of Arctic Siberia.

Vegetation Response to the Climate Change in Polar Chukotka from 2.510-2.554 Ma BP

The response of vegetation to climate change in Polar Chukotka between 2.510 and 2.554 Ma was determined by a palynological study of sediment cores from Lake Elgygytgyn recovered during the international expedition "El'gygytgyn Drilling Project". Six pollen zones were defined for this interval, which spans marine isotope stages (MIS) 101 and 100. Pollen zones 1 and 2 (MIS 101) as well as zones 3 and 4 (MIS 100) indicate the presence of Larix and Larix-Betula forests during interglaciations. The plant communities reflected in the spectra of zone 3 represent the warmest climates during the early Gelasian Age. During MIS 100, the period of maximum climate cooling is marked by the regional presence of shrub and herb dominated tundra (pollen zone 5). During the interstade (MIS 100, zone 6), the vegetation was dominated by Larix forest tundra. Pollen zones 3 and 4, which have spectra more indicative of interglacial rather than glacial plant communities, are more consistent with climate of MIS 101 and not MIS 100, as suggested by the core's age model. The incorrect age assignment of the boundary between these stages indicates that the Lake El'gygytgyn age model needs revision.

Изменения растительных сообществ арктической Чукотки в изотопные стадии 40-49

The palynological record from Lake El'gygytgyn, spanning the interval between c. 1.286 and 1.492 million years ago, shows repeated changes in plant communities in Arctic Chukotka, which reflect variations in glacial, interstadial, and interglacial climatic conditions. Thirteen pollen zones were defined, corresponding to marine oxygen isotope stages 40-49. The consistent presence of Larix pollen in these pollen spectra indicates that even under extremely severe climatic conditions that occurred in areas of the Anadyr plateau and Lake El'gygytgyn during the Calabrian Age, larch forest-tundra survived. The continued presence of forest habitats differs sharply from the herb- dominated tundra that characterized many glacial intervals in the Arctic during the Middle and Late Pleisto?ene. The warmest climate within the 1.286-1.492 million year interval, seen in pollen zone 9, appeared during isotope stage 43. The maximum in cold conditions occurred during the second half of isotope stage 44 (pollen zone 8).

Middle-Late Eocene Climate in the Pearl River Mouth Basin: Evidence from a Palynological and Geological Element Record in the Xijiang Main Subsag

The temperature changes in the middle-late Eocene had a profound impact on various ecosystems around the world. This has been confirmed not only in marine sediments but also in lake ecosystems, which have provided more detailed isochronous continental sedimentary records. Based on systematic palynological and element analyses of fine-grained lacustrine sediments from the Xijiang main subsag in the Pearl River Mouth Basin, southern China, we reconstructed the climate evolution of the middle-late Eocene. A total of 73 genera and 115 species of sporopollen fossils were identified from the middle-late Eocene in the study area. Three pollen zones comprising Quercoidites–Polypodiaceaesporites–Pinuspollenites, Pinuspollenites–Ulmipollenites–Cedripites, and Pinuspollenites–Abietineaepollenites–Juglanspollenites were established from bottom to top. The analysis of the vegetation types, climatic zones, and dry–humid types of the sporopollen showed that, in the study area, the Eocene was dominated by a subtropical–warm temperate climate: the early-late Eocene was dominated by a temperate climate, and the late Eocene was characterized by the prevalence of a warm temperate climate, which was consistent with the palaeoclimate reconstruction results for element geochemical indices (Fe/Mn, Sr/Cu, CIA, PIA, etc.). In addition, the comparative study showed that the middle-late Eocene in the study area was characterized by a warm and humid climate, which transitioned to a warm and cool semihumid–semiarid climate and then a warm and cool semihumid climate. These findings demonstrated a good coupling relationship with the trend for the changes in the global palaeotemperature and can be used as an isochronous continental sedimentary response.

Early to Mid-Holocene Tree Immigration and Spread in the Isle of Man: The Roles of Climate and Other Factors

The Isle of Man is a large island which lies in the middle of the northern Irish Sea between Britain and Ireland and, because of its insularity and size, has an impoverished flora compared with the two main islands. This has been the case throughout the postglacial and warrants the island’s description as a separate phytogeographic province. We have considered Holocene tree pollen data from seventeen sites on the island which together preserve a vegetation history that spans the six thousand years of the early and mid-postglacial from the end of the Lateglacial at 11,700 cal. BP to the mid-Holocene Ulmus decline at ca. 5800 cal. BP. Radiocarbon dating of the rational limits of the pollen curves for the main tree taxa has allowed an appraisal of the timing of each one’s expansion to become a significant component of the island’s woodland, and comparison with the dates of their expansion on the adjacent regions of Britain and Ireland. The radiocarbon dates show that, although some variability exists probably due to local factors, there is considerable concordance between the timings of major pollen zone boundaries in Britain and Ireland around the northern Irish Sea. On the Isle of Man the expansions of both Juniperus and Betula were delayed by several centuries compared to the British/Irish data, however the timing of the expansions of Corylus, Ulmus, Quercus, Pinus and Alnus on the Isle of Man all appear closely comparable to the ages for these pollen stratigraphic events in north Wales, northwest England, southwest Scotland and eastern Ireland, as are those for the Ulmus decline. It is likely that local pedological and edaphic factors on the island account for the differences in the first Holocene millennium, while regional climatic factors governed the timings for the rest of the expansions of tree taxa across the wider region, including the Isle of Man. Disturbance, including by human agency, was important at the site scale and perhaps triggered early tree expansion in some places, including Quercus, Ulmus and Alnus. Insularity seems not to have been a significant factor in the expansion of the major forest trees.

Reconstruction of the sedimentary environment of phytogenic deposits in the Tomisławice opencast mine (Konin Region, central Poland)

Palynological analysis of the Tomis³awice opencast mine deposits has allowed reconstruction of the plant communities and investigation of the evolution of sedimentary environments at various stages of lignite-forming marsh development, recorded in the composition of pollen assemblages from deposits of the 1st Mid-Polish lignite seam (MPLS-1). Rich pollen communities from an ~9 m thick section has enabled study of the succession of plant communities and of the evolution of phytogenic sedimentation. The pollen succession indicates that the assemblages in the whole lignite seam represent the VIII Celtipollenites verus pollen Zone. Slight differences in the composition of the communities reflect different stages of basin development, depending more on the variable water dynamics than on climatic oscillations. Lignite of the MPLS-1 developed in a continental regime on alluvial plains. Changes in the succession of plant communities in the Tomis³awice section record flooding-drainage cycles caused by groundwater level oscillations. Peat bog accumulation took place in river basins, in which the lack of siliciclastic intercalations within the massive lignite seams points to weak fluvial dynamics. A rise in groundwater level and/or surface water resulted in flooding of the marshes and the formation of an extensive shallow lake basin, as shown by the presence of freshwater algae and pollen of aquatic plants. The section as a whole does not record an increased contribution of thermophilic plant taxa. The flora was generally dominated by warm-temperate and thermophilic species, without the participation of strongly thermophilic vegetation, which indicates that the lignite seam in the Tomis³awice opencast mine was formed in the generally stable conditions of a warm temperate climate.

Late Quaternary tephrostratigraphy and pollen stratigraphy of Uwa Formation, Shikoku Island, SW Japan: Reconsidering the MIS 11 super-interglacial horizon

We investigated a late Quaternary terrestrial sedimentary sequence (Uwa Formation) in core IC2, from a site adjacent to that of the reported core IC on NW Shikoku Island, SW Japan, and developed its tephra and pollen stratigraphy to refine the age model of the formation. First, we identified 19 horizons with high glass shard concentrations in the IC2 core sediments as possible tephras or cryptotephras, and correlated them with reported tephras on the basis of the major- and trace-element compositions of their glass shards. All correlated widespread tephras and cryptotephras were products of volcanoes in the Kyushu volcanic zone (Aso, Kakuto, Aira, Ata, and Kikai calderas). Second, we confirmed the presence in core IC2 of two pollen zones dominated by Quercus subgen. Cyclobalanopsis , which is an indicator of very warm interglacial vegetation. In the Japanese Islands, these two vegetation zones have usually been considered to characterize marine isotopic stages (MISs) 1 and 11. A previous study of the Uwa Formation correlated the upper pollen zone to MIS 1, but the lower zone was not correlated to MIS 11; rather, it was inferred to be older than MIS 12 because it was stratigraphically below the “Oda” tephra (equivalent to a distal Kasamori 5 [Ks5] tephra [MIS 12]). In this study, however, noting that the Naruohama-IV tephra (Nh-IV; MIS 10d) and Ks5 cannot be distinguished by their shard chemistries, we inferred that the suggested “Oda” tephra actually correlates to Nh-IV, rather than to the Ks5 tephra. By re-assigning the “Oda” tephra to Nh-IV, we could correlate the underlying Quercus subgen. Cyclobalanopsis -abundant zone to MIS 11 and, consequently, a pair of pollen zones indicating cool and warm conditions below the MIS 11 pollen zone to MISs 12 and 13, respectively. The resulting age model whereby tephra and pollen constraints are integrated showed a roughly constant sedimentation rate from MIS 13, without any long-term gaps; further, our MIS 13 horizon in core IC2 corresponds to the reported 1 Ma tephra horizon in core IC. Therefore, these findings represent a dramatic change in the Uwa Formation age model and validate the Uwa Formation as one of the most useful terrestrial archives of Quaternary tephrostratigraphy and paleoclimatic fluctuation in SW Japan. • 1.Tephra and pollen stratigraphies of Uwa Basin deposits on Shikoku were investigated (83/85 characters) . • 2.Tephrostratigraphy was revised by single-shard major- and trace-element compositions (84/85 characters) . • 3.The tephra-based age model is consistent with the pollen stratigraphy (69/85 characters) . • 4.The MIS 11 period was found to be characterized by a very warm pollen assemblage (80/85 characters) . • 5.In the revised age model, the sedimentation rate is approx. Constant from MIS 1 to 13 (85/85 characters) .

Vegetation Response to Climate Change during the Middle Calabrian in Arctic Chukotka

A palynological record obtained from El'gygytgyn Lake sediments, which spans the 1.244-1.304 million years (Ma) interval of the Calabrian Stage, shows repeated changes in the plant communities of Arctic Chukotka. These variations in the vegetation further suggest a dominance of interstadial and interglacial climates. Eight pollen zones were distinguished within this interval. According to the working age model for the composite El'gygytgyn core, these pollen zones correspond to marine oxygen isotope stages (MIS) 40, 39, and 38. The upper boundary of MIS 38 coincides with magnetic event the Cobb Mountain (1.240 Ma), which is one of the main chronological landmarks used in creating the core's chronology. The features of modern pollen-spore spectra obtained from the water-sediment interface within the lake aided in reconstructing both the local and regional paleovegetation. The consistent presence of Larix pollen throughout the 1.244-1.304 Ma interval indicates that even under the severest climatic conditions Larix forest-tundra persisted on the Anadyr Plateau and near El'gygytgyn Lake. This pattern differs sharply from that seen in the Middle and Late Pleistocene when herb-dominated tundra characterized the glacial intervals in the Arctic. The spore-pollen spectra further show that the warmest climatic conditions occurred during MIS 39. The data from the 1.244-1.304 Ma interval represent the last step in completing the Quaternary vegetation history from this unique site in Arctic Siberia.

A proto-monsoonal climate in the late Eocene of Southeast Asia: Evidence from a sedimentary record in central Myanmar

The Burma Terrane has yielded some of the earliest pieces of evidence for monsoonal rainfall in the Bay of Bengal. However, Burmese ecosystems and their potential monsoonal imprint remain poorly studied. This study focuses on the late Eocene Yaw Formation (23° N) in central Myanmar, which was located near the equator (c. 5° N) during the Eocene. We quantitatively assessed the past vegetation, climate, and depositional environments with sporomorph diagrams, bioclimatic analysis, and sequence biostratigraphy. We calculated the palynological diversity and drew inferences with rarefaction analysis by comparing with four other middle to late Eocene tropical palynofloras. Palynological results highlight a high floristic diversity for the palynoflora throughout the section formed by six pollen zones characterized by different vegetation. They indicate that lowland evergreen forests and swamps dominated in the Eocene Burmese deltaic plains while terra firma areas were occupied by seasonal evergreen, seasonally dry, and deciduous forests. This vegetation pattern is typical to what is found around the Bay of Bengal today and supports a monsoon-like climate at the time of the Yaw Formation. Bioclimatic analysis further suggests that in the late Eocene, the Yaw Formation was more seasonal, drier, and cooler compared to modern-day climate at similar near-equatorial latitude. More seasonal and drier conditions can be explained by a well-marked seasonal migration of the Intertropical Convergence Zone (ITCZ), driver of proto-monsoonal rainfall. Cooler temperatures in the late Eocene of central Myanmar may be due to the lack of adequate modern analogues for the Eocene monsoonal climate, while those found at other three Eocene Asian paleobotanical sites (India and South China) may be caused by the effect of canopy evapotranspirational cooling. Our data suggest that paleoenvironmental change including two transgressive–regressive depositional sequences is controlled by global sea level change, which may be driven by climate change and tectonics. The high diversity of the Yaw Formation palynoflora, despite well-marked seasonality, is explained by its crossroads location for plant dispersals between India and Asia.

Middle Miocene (Serravallian) wetland development on the northwest edge of Europe based on palynological analysis of the uppermost Brassington Formation of Derbyshire, United Kingdom

In this paper, we describe palynological assemblages in the Middle Miocene (Serravallian) Kenslow Member of the Brassington Formation at Bees Nest Pit, near Brassington, Derbyshire, U.K., and infer vegetation types and their palaeoclimate implications. The limited lateral extent of the 1.33 m-thick succession of clay and lignite, and its position surrounding fragments of a large tree trunk, suggests that the succession may have accumulated within a tree throw hole or possibly within a shallow stagnant pond, although aquatic lacustrine palynomorphs have not been identified to confirm this latter hypothesis. The stratigraphical distribution of palynological assemblages, based on 58 samples allows reconstruction of a wetland succession. Two pollen zones were identified using CONISS cluster analysis, and a predominantly warm-temperate and mixed mesophytic forest biome was recognised with Tsuga conifer pollen-types being dominant (<42%) in both pollen zones. Changes in the make-up of this forested wetland were in response to local environmental changes rather than major climatic shifts. Wetland development culminated in the formation of a relatively open shrub and reed-dominated mire which produced the lignite-precursor peat. Applying the Co-existence Approach, Mean Annual Temperature was 15.6–21.7 °C and Mean Annual Precipitation was 703–1682 mm indicating a warm-temperate to subtropical palaeoclimate, and both parameters show no significant change through the section. Findings suggest that, following the Middle Miocene Climatic Optimum, the Serravallian climate of the northwestern margin of Europe remained much wetter than Central Europe, where more arid climates have been reconstructed, and this difference may have been due to the influence of the proto-North Atlantic Current.