Peat Sediments Research Articles

Late Quaternary tephrostratigraphy of southern Chile and Argentina

The Southern and Austral Volcanic Zones of the Andes comprise 74 volcanic centres with known post-glacial activity. At least 21 of these have had one or more large explosive eruptions in the late Quaternary, dispersing tephra over vast areas. These tephra layers therefore have great potential as tephrochronological marker horizons in palaeoenvironmental studies in southern Chile and Argentina, a region that is particularly useful to study climate dynamics of the southern hemisphere. However, to date tephrochronology has rarely been fully utilised in this region as a correlation and dating tool. Here we review the existing post-glacial tephrostratigraphic record of the Southern and Austral Volcanic Zones, and compile a database of known occurrences of tephra from these volcanoes in ice and lacustrine, marine, peat, and cave sediment records. We address the inconsistencies in and revisions of the tephrostratigraphies presented in prior literature, and discuss the challenges in correlating tephras and the limitations of the tephrostratigraphic record in this area. This study highlights the many gaps that still exist in our knowledge of the eruptive histories of these volcanoes, but also reveals the largely under-utilised potential of tephra as a correlation tool in this region. This is exemplified by the severe lack of adequate geochemical analysis of tephra layers preserved in many lacustrine and peat sediment sections, which are particularly important tephrostratigraphic records in southern Chile and Argentina due to the paucity of surface preservation.

Variations and driving forces of the relative abundance of C<sub>3</sub>/C<sub>4</sub> plants in the northern Leizhou Peninsula since the Last Glacial Age

末次冰期以来陆地植被中C₃/C₄植物相对丰度变化及其驱动因素是当前古生态古气候研究中的重要内容.本文利用雷州半岛北部下录和屋山两处泥炭沉积有机碳同位素组成(δ¹³C_org)重建了该区域末次冰期以来C₃/C₄植物相对丰度演化历史,并探讨了其可能的驱动因素.结果表明,在MIS-3阶段初期,屋山地区的植被以C₃和C₄混合植被为主,在此后的MIS-3阶段绝大部分时期,下录和屋山地区的植被主要为C₃植被,在个别时段C₄植物也曾一度有所扩张;在MIS-2阶段,下录地区C₃植物含量显著降低,区域植被以C₄植物为主;在全新世初期,下录地区的C₃植物含量呈现出增加趋势,气候环境变得有利于C₃植物生长.对比研究表明,由于在末次冰期乃至冰期最盛期阶段,雷州半岛地区的气温下降幅度可能仅在5~8℃左右,温度足以满足C₃/C₄植物的生长需要,从而使得受东亚夏季风强度直接影响的降水增多或减少成为控制本区域C₃/C₄植物相对丰度变化的主导因素.此外,大气CO₂浓度可能对该地区C₃/C₄植物相对丰度变化也具有一定的影响.;The relative abundance of C₃/C₄ plants since the Last Glacial Age and its possible driving mechanisms are the key contents in the fields of paleoecology and paleoclimate research. Here we present a new organic carbon isotope (δ¹³C_org) time series of peat sediments, spanning from 61000 cal a B. P. to 10000 cal a B. P. derived from the northern Leizhou Peninsula. To better understand the past vegetation responses to the climatic and environmental changes, we estimated the relative abundance of C₃ and C₄ plants using the δ¹³C_org records and compared them with other climatic records. The estimated results indicate that the vegetations in the study region were mainly composed of mixture of both C₃ and C₄ plants in the early stage of MIS-3. During the rest of the MIS-3, C₃ plants were dominant, although C₄ plants expanded to a certain extant during certain periods. During the MIS-2, the relative abundance of C₃ plants decreased significantly and C₄ plants expanded greatly. At the beginning of the Holocene, the proportion of C₃ plants seemed to increase gradually. Variations of the relative abundance of C₃ and C₄ plants in the northern Leizhou Peninsula was similar to the pattern of East Asian monsoon intensity reconstructed from the stalagmites records, suggesting that the East Asian monsoon intensity accompanied with the changes in monsoonal precipitations exerted a very strong control on the relative abundance of C₃ and C₄ plants. It is likely that the temperature threshold, which is normally an important factor in high latitudes, may be less important in influencing the relative abundance of C₃ and C₄ plants in tropical southern China. The atmospheric CO₂ concentration may also partly superimpose some influences on the variations of relative abundance of C₃ and C₄ plants at orbital scale.

Geochemical records of palaeoenvironmental controls on peat forming processes in the Mfabeni peatland, Kwazulu Natal, South Africa since the Late Pleistocene

The Mfabeni peatland is the only known sub-tropical coastal fen that transcends the Last Glacial Maximum (LGM). This ca. 10m thick peat sequence provides a continuous sedimentation record spanning from the late Pleistocene to present (basal age c. 47kcalyr BP). We investigated the paleaeoenvironmental controls on peat formation and organic matter source input at the Mfabeni fen by: 1) exploring geochemical records (mass accumulation rate, total organic carbon, carbon accumulation rate, δ13C, δ15N and C/N ratio) to delineate primary production, organic matter source input, preservation and diagenetic processes, and 2) employ these geochemical signatures to reconstruct the palaeoenvironmental conditions and prevailing climate that drove carbon accumulation in the peatland. We established that the Mfabeni peat sediments have undergone minimal diagenetic alteration. The peat sequence was divided into 5 linear sedimentation rate (LSR) stages indicating distinct changes in climate and hydrological conditions: LSR stage 1 (c. 47 to c. 32.2kcalyr BP): predominantly cool and wet climate with C4 plant assemblages, interrupted by two short warming events. LSR stage 2 (c. 32.2 to c. 27.6kcalyr BP): dry and windy climate followed by a brief warm and wet period with increased C4 sedge swamp vegetation. LSR stage 3 (c. 27.6 to c. 20.3kcalyr BP): initial cool and wet period with prevailing C4 sedge plant assemblage until c. 23kcalyr BP; then an abrupt change to dry and cool glacial conditions and steady increases in C3 grasses. LSR stage 4 (c. 20.3 to c. 10.4kcalyr BP): continuation of cool and dry conditions and strong C3 grassland signature until c. 15kcalyr BP, after which precipitation increases. LSR stage 5 (c. 10.4kcalyr BP to present): characterised by extreme fluctuations between pervasive wet and warm to cool interglacial conditions with intermittent abrupt millennial-scale cooling/drying events and oscillations between C3 and C4 plant assemblages. In this study we reconstructed a high-resolution record of local hydrology, bulk plant assemblage and inferred climate since the Late Pleistocene, which suggest an anti-phase link between Southern African and the Northern Hemisphere, most notably during Heinrich (5 to 2) and Younger Dryas events.

Vertical variations and associated ecological function of bacterial communities from Sphagnum to underlying sediments in Dajiuhu Peatland

To investigate vertical changes of bacterial communities from living plants to the associated sediments and bacterial biogeochemical roles in peatland ecosystem, samples of different part of individual Sphagnum palustre and the different layers of the underlying sediments were collected from Dajiuhu Peatland in central China. All samples were subject to 16S rRNA gene clone libraries and quantitive PCR analysis. Even though bacteria vary in abundance at the same order of magnitude in all samples, they show great profile difference in composition from the top part of S. palustre to the low layer of the sediments. Cyanobacteria and alpha-Proteobacteria dominate at the top part whereas Acidobacteria at the middle part of S. palustre. Alpha-Proteobacteria and Acidobacteria are the dominant phyla at the bottom part of S. palustre and in the surface peat sediment. In contrast, bacterial communities in the subsurface sediments are dominated by Acidobacteria. These profile distributions of different bacterial communities are closely related to their ecological functions in the peatland ecosystem. Specifically, most Cyanobacteria were observed at the top green part of S. palustre, a horizon where the active photosynthesis of the moss occurs, which infers their endosymbiosis. In contrast, Acidobacteria, dominant in the subsurface sediments, are able to decompose the specific compounds on the cell wall of Sphagnum moss and thus might play an important role in the formation of the peatland, including the acidic condition. Methane oxidizing process might have been underestimated in Sphagnum peatland due to the identification of Methylocystaceae in all parts of the moss investigated here. The vertical difference in bacterial composition and bacterial ecological functions presented here sheds light on the understanding of biogeochemical processes, in particular the CH4 flux, in peat ecosystems.

Macrophyte loss drives decadal change in benthic invertebrates in peatland drainage ditches

Summary Agricultural peatlands and their associated drainage systems are often highly managed and exposed to anthropogenic pressures, such as eutrophication and stable water tables, maintained via drainage during periods of high rainfall and inlet of, alkaline‐rich, waters during dry periods. These pressures promote peat degradation, resulting in the accumulation of fine‐degraded peat particles that dramatically alter aquatic habitats by smothering surfaces and decreasing water quality. Consequential effects on benthic communities are expected but have not been investigated so far. We hypothesised that peat degradation can lead to the decline in submerged macrophytes, which are of critical importance to sustaining biodiversity of benthic invertebrate communities. To investigate this, we analysed decadal (1985–2007) changes in benthic species richness in 29 peat ditches in the Netherlands and, to determine patterns of macroinvertebrate habitat occupancy, carried out a complementary field experiment with submerged artificial macrophytes, natural sediments and emergent bank vegetation. Results from long‐term monitoring indicate that chemical conditions in agricultural peat ditches have improved slightly over the last decades; however, there has been a simultaneous decline in benthic invertebrate species richness and densities corresponding to a decline in the numbers of submerged macrophytes. The apparent dependence of macroinvertebrates on macrophytes was reinforced by our field experiment which revealed that invertebrate density was highest in submerged artificial plants, while invertebrate species richness was highest in natural emergent vegetation. Conversely, degraded peat sediments supported extremely few invertebrates. Our results clearly illustrate the strong influence of submerged macrophyte loss on macroinvertebrate assemblages in peatland waters. Furthermore, this suggests that improvements in water quality alone will not benefit invertebrates in the absence of suitable vegetative habitats.

Brinson Review: Perspectives on the Influence of Nutrients on the Sustainability of Coastal Wetlands

Among the solutions being proposed for reversing wetland loss in the Mississippi River Delta are the creation of diversions to reintroduce suspended sediment carried in the river. In areas of rapid relative sea-level rise, as in the Mississippi Delta, it is generally accepted that a supply of sediment in flood water and mineral sedimentation are critical to sustaining wetlands. But plans to create diversions have raised questions about the collateral effects of nutrients carried in the Mississippi River, effects that may contravene the benefits of sediment. This review finds the balance of empirical and theoretical evidence supports that nutrients benefit above- and belowground plant production and that fresh water and sediment diversions can be effective and beneficial for restoring wetlands in the Delta, especially if designed to maximize sediment inputs. The input of sediment, nutrients, and fresh water will change the community composition of some wetlands and their biogeochemical processes. Most of the nitrogen input should be assimilated or denitrified. Labile organic matter is likely to degrade more quickly, but labile organic matter does not add ‘new’ soil volume and its speed of decay is of little consequence. Additional research is needed before we fully understand the consequences of nutrients on the preservation of organic matter in sediment, but building on what is known of the activities of lignin-degrading fungi and their enzymes, it is likely that refractory organic matter should increase and contribute positively to sediment accretion. This is supported by long-term studies of sediment accretion in a New England salt marsh with peat sediment, and in a mineral-dominated southeastern salt marsh, that show elevations in fertilized plots gained as much or more than in reference plots.

Tafonomia de Esporos de Pteridófitas Encontrados em Sedimentos Turfosos Quaternários do Rio de Janeiro, Brasil

Taphonomy is a tool used in palaeoenvironmental interpretations dating back to the process of palynomorphs deposition. The interpretation of taphonomic studies provides subsidies to the understanding of the environmental past conditions through the marks left on the preserved palynomorphs. The study area is located in the Praia Vermelha, Urca district, municipality of Rio de Janeiro, in the entrance of Guanabara Bay. The preservation of spores inside a columnar profile, constituted of peat and sandy mud sediments, was studied, comprising a time interval from about 4,520 to 4,270 years B.P. Eight levels were selected and sampled. The spores were classified according to the type of deterioration, by damages of corrosion and degradation and by mechanical damages. The percentage of each kind of deterioration was calculated in relation to the total number of counted spores and the concentration in relation to one cm³ of sediment. A large number of spores presenting corrosion and degradation damages was observed, being characteristic of air exposure, indicating occasions of lower water availability in this site. The predominance of undamaged spores in some levels suggests an underwater sedimentation, corroborated by sedimentary analyses.

Magnetic investigation of peat sediments from the mountain in Arid Regions

Detailed and systematic magnetic analysis was conducted on continuous peat depositional sequences from the Altay Mountains in arid regions, Northwest China. Based on magnetic properties, such as composition, concentration and grain-size, the magnetic-variation mechanism of these minerals can be discussed in peat sediments that are rich in organic matter under redox conditions. The results are showed as follows: The concentration of ferrimagnetic minerals has a low enrichment degree. Magnetite, hematite, a great deal of diamagnetic organic matter and some paramagnetic components have been identified in peat sediments, and there is no magnetotactic bacteria (MTB). The grain sizes are mainly fine particles, but meanwhile there are also coarse particles-multidomain (MD). The results further reveal that the major variations of ferrimagnetic minerals in the peat sediments occur during the short period of post-depositional processes. As for the possible mechanism, we argue that the pseudo single domain (PSD) and MD magnetite on the peatland surface are dissolved and refined in the acid waterlogged sub-oxic conditions, which results in low concentration and smaller grain sizes. Furthermore, we also speculate that no long-term burial-diagenetic dissolution processes take place in the peat sediments and little magnetite dissolution happens under the condition of alkaline and reductive environments in which the peat is buried deeply.

Limnological record inferred from diatoms in sediments of Lake Skaliska (north-eastern Poland)

ABSTRACT Subfossil diatoms analysis was employed to reconstruct past environmental changes in Lake Skaliska. This lake, presently a palaeolake, is located on a wide plain called the Skaliska Basin (northern part of Mazury Lake District, north-eastern Poland). Changes in terrestrial vegetation suggest that the initial phase of the lake was in the early Holocene. In the sediments a total of 176 diatom species belonging to 35 genera were identified. The majority of diatoms are alkaliphilous and alkalibiontic, occurring mainly in meso-eutrophic water. Diatom flora development suggests that the best conditions for diatom growth prevailed throughout the Boreal and in the early Atlantic, a suggestion supported by the increased frequency of planktonic diatoms living in nutrient-rich water. A water pH reconstruction (DIpH) based on diatoms points to alkalinity during the lake’s existence. Since roughly the mid-Atlantic the lake was shallowing, and at the beginning of the Subboreal peat sedimentation led to complete overgrowth of the lake.

Winter and summer monsoonal evolution in northeastern Qinghai-Tibetan Plateau during the Holocene period

Climate change especially moisture condition in the northeastern Qinghai-Tibetan in China are mainly controlled by the strength and variability of Asian winter and summer monsoon. In this paper, we presented the climate record and related winter and summer monsoonal history in Gonghe Basin, northeastern Qinghai-Tibetan Plateau, based on the geochemical indicators (geochemical elements content, i.e., Fe2O3, CaO, Zr and Sr content, and geochemical parameters, i.e., the chemical index of alteration (CIA), Zr/Rb, Rb/Sr, CaO/MgO, SiO2/TiO2 and SiO2/(Al2O3+Fe2O3) ratio) of the peat deposits and 14C and OSL technologies. The regional temperature and humidity gradually increased in 10.0–8.5calkaBP, accompanied by enhanced summer monsoonal strength and decreased winter monsoonal strength. But climate became cold and dry between 8.5calkaBP and 7.6calkaBP owing to the stronger winter monsoon. During the 7.6–3.8calkaBP, stronger summer monsoon and weaker winter monsoon led to an optimal warm and humid condition, although it had several cold phases. From 3.8calkaBP to 0.5calkaBP, the regional climate tended to be cold and dry, with increasing winter monsoonal strength and decreasing summer monsoonal strength. Thereafter, the relatively warm and humid climate appeared again, due to the stronger summer monsoon. That is to say, the regional climate conditions are mainly related to the winter and summer monsoonal changes. These changes are consistent with palaeoclimatic records (monsoonal model) from the region influenced by the Asian monsoon in eastern China. In addition, nine cold events were recorded: 8.5–7.8calkaBP, 6.1–5.6calkaBP, 5.2–4.8calkaBP, 4.7–4.3calkaBP, 4.1–4.0calkaBP, 3.8–3.4calkaBP, 3.0–2.3calkaBP, 1.4–1.3calkaBP, and 1.0–0.5calkaBP, which are coincident with cold fluctuations in the high and low latitudes of the Northern Hemisphere on a millennial scale, as recorded by lakes, peat sediments, and ice cores in the Qinghai-Tibetan Plateau. In conclusion, Holocene millennial-scale climatic changes in Gonghe Basin were controlled by the dual function of Asian monsoonal changes and global cold fluctuations.

Sedimentary transport and fate of polycyclic aromatic hydrocarbons (PAH) from managed burning of moorland vegetation on a blanket peat, South Yorkshire, UK

This study reports the concentrations of 18 polycyclic aromatic hydrocarbons (PAH) from managed burning of moorland vegetation and compares them to PAH in catchment vegetation, underlying peats, head water suspended sediment (HSS), stream water and reservoir sediment cores. Total PAH ranged from 203 to 11,112μg/kg in the blanket peats, 101–290μg/kg in the fresh moorland vegetation, 4186μg/kg at the burnt site, 17,439μg/kg in the HSS, 56ng/L in the stream water and 987 to 7346μg/kg in the reservoir sediments. No total or individual PAH concentrations exceeded the published sediment quality guidelines. The perylene content of selected moorland vegetation (sphagnum, heather and bilberry) ranged from 10 to 18% as compared to only 2% for the sediment hosted PAH. A comparison of whole and <250μm fractions from the burnt surface layer revealed a near threefold increase in PAH concentration in the fine fraction and a change in the PAH distribution such that naphthalene>>phenanthrene>2-methylnaphthalene. Elevated total PAH contents were observed close to the blanket peat sediment surface (0–10cm) and then declined at greater depths. The high PAH content of the HSS was attributed to the high sorption capacity of the organic-rich particles (TOC 25.8% (wt/wt)). The distribution of individual PAH in reservoir cores and HSS was consistent and the results of the principal component analysis and isomeric ratios suggest mainly pyrolytic inputs, from either vegetation burning and coal combustion. A comparison of the reservoir core PAH profiles shows that the source(s) have remained largely unchanged since the reservoir construction in 1929A.D. reflecting consistent moorland management practices.

The Age of the Late Mesolithic on the North York Moors, England: radiocarbon dating a small flint tool stratified in peat from East Bilsdale Moor

There has been a considerable amount of pollen-analytical research on the palaeoecology and palaeoenvironment of the Late Mesolithic culture of the North York Moors upland in north-east Yorkshire, which together with the Pennines is the most prolific area in Britain for Late Mesolithic flint sites. The peat sediments of the Moors have provided detailed data on the vegetation history of the mid-Holocene, both natural developments and also woodland disturbance by fire, as revealed in the macroscopic and microscopic charcoal evidence preserved in the peats and in its relation to the recorded changes in woodland composition and density. The Late Mesolithic vegetation history of the North York Moors can now be reconstructed with confidence and, given the high concentration of lithic sites of that period, linkages between the archaeological and palaeoecological records are often attempted with a view to explaining disturbance regimes as resulting from the impacts of foragers’ activities in the landscape. Unlike the Pennines, however, in the North York Moors no Late Mesolithic sites have been radiocarbon dated, so no chronological correlation can be made between the palaeoenvironmental data and the archaeological evidence. This paper presents the first radiocarbon date for a Late Mesolithic flint artefact from the North York Moors, from East Bilsdale Moor, and examines its implications for the age range of the Late Mesolithic on the Moors as a whole, and for the association of evidence of woodland disturbance on the Moors upland with the presence of Late Mesolithic hunters there.

Vegetation dynamics around Lake Baikal since the middle Holocene reconstructed from the pollen and botanical composition analyses of peat sediments: Implications for paleoclimatic and archeological research

The present paper summarizes the current evidence of natural changes in the forest and forest-steppe areas of the Lake Baikal Region (LBR) since ca. 7 cal ka BP, covering the period from the late Neolithic to the present time. To reconstruct local to small-regional scale vegetation changes and their probable causes during this period, pollen content and peat botanical composition were analyzed from three radiocarbon-dated peat sections, located near Lake Baikal. For better understanding of the local and regional environmental history and climate variability during the middle and late Holocene, the results are compared with published environmental records from lacustrine and mire sediments from the LBR and from elsewhere. The comparison confirms the earlier interpretations that the middle and late Holocene vegetation dynamics in the LBR was primarily driven by natural forcing and likely was associated with large-scale circulation processes controlling the regional water balance rather than with human activities. Some synchronous changes in environmental and archeological data likely point to a possible causal link between past climate changes and the cultural history of the region. The Kuchelga (53°00′57″N, 106°44′49″E), Ochkovoe (51°26′05″N, 104°38′57″E) and Cheremushka (52°45′09″N, 108°05′50″E) peat records represent three different climatic regions around Lake Baikal and demonstrate that the environments and vegetation of the drier western coast were more sensitive to the climate oscillations of the middle and late Holocene in comparison to the more humid areas east, and particularly south of Baikal. Therefore, it could be expected that environmental impact on early human societies was strongest in the arid region to the west of Lake Baikal. To test this hypothesis, however, accurately dated multi-proxy records of the Holocene climate and environments from this so far poorly studied region are absolutely necessary.

Upper Holocene development of vegetation and radiocarbon dating in the vicinity of the Cerhovka Brook (Bohemian-Moravian Uplands, Czech Republic)

Abstract The paper reports the results of a palynological study of a newly exposed section in the peat sediments of Bezděkov site and its correlation with the previous palaeobotanical studies. The main goal was to elucidate the stratigraphic position and paleogeographic development of fossil peat bog and its environment in the Protected Landscape Area Žďárské vrchy and Železné hory in the Bohemian-Moravian Uplands. The development of peatbog vegetation, as shown by the pollen analysis and radiocarbon dating, took place in the Holocene. Pollen analyses provide evidence for occurrences of wetland assemblages with huge representation of alder wood in all the part of succession, followed by willow near the Cerhovka Brook. Alnus and Abies were the dominant trees during all the time. The deciduous forests consist of elm (Ulmus), oak (Quercus), lime tree (Tilia), maple (Acer) and hazel (Corylus). The mosaic picture of woodland and wetland, which covered this landscape during the Upper Holocene, contrasts with the present day monotonous open lowland. Sediments of the peat bog provide information on the origin and vegetation evolution of this area.

A tribute to Prof. DSc Elissaveta Bozilova on the occasion of her 80th birthday

One of the outstanding European palynologists and palaeoecologists, Prof. DSc Elissaveta Bozilova celebrates her 80th birthday on March 17th 2012. For more than 50 years she has been actively involved in science and teaching in the Faculty of Biology at Sofia University St. Kliment Ohridski. Her interest in botany, and subsequently in palynology, was encouraged and supported by her master’s degree supervisor Prof. Boris Kitanov in the mid 1950s and also by her family members. The remarkable scientific and teaching career of Elissaveta Bozilova started in 1958 when she joined the academic staff of the Department of Botany as an Assistant Professor. The initial years of her research were devoted mostly to the investigation of the pollen morphology of various gymnosperm and flowering plant taxa, but subsequently this knowledge was applied to the study of the late Quaternary history of the Bulgarian flora and vegetation, and gradually expanded to aeropalynology, melissopalynology, archaeobotany, marinopalynology and pollen monitoring. Numerous pollen analytical studies were conducted by her on lake, mire and peat sediments in the glaciated and nonglaciated Bulgarian mountains, along the Black Sea coast, the Danube valley and inland plains as well as on marine cores. Elissaveta Bozilova and her co-workers postulated for the first time the main chronological stages in the lateglacial and Holocene vegetation development in different parts of the country and contributed to the elucidation of important scientific issues such as location of glacial tree refugia and migration routes, fluctuations in the tree line, formation of recent vegetation belts and specific plant communities, pollen dispersal mechanisms, climate changes, sea-level fluctuations, human impact on the natural environment since prehistoric times, etc. She also laid the foundations of contemporary aeropalynological and melissopalynological studies in Bulgaria. An important premise for the recognition of Elissaveta Bozilova as a leading Bulgarian palynologist was the establishment of personal and fruitful long standing scientific contacts with outstanding foreign specialists, including Prof. H. -J. Beug, Prof. G. Lang, Prof. B. E. Berglund, Dr. A. Smit, Prof. K. Faegri, Prof. H. J. B. Birks, Prof. M. Ralska-Jasiewiczowa, Prof. Y. Vasari, Prof. B. Ammann, Prof. L. -K. Konigsson, Prof. S. Hicks, Prof. J. -L. de Beaulieu, Prof. K. -E. Behre, Prof. N. Athanasiadis, Prof. C. -A. Haeggstrom, Prof. H. Jungner, Prof. A. Gerasimidis, and many others, who shared generously their knowledge and expertise in palaeoecological and botanical research, both in the field and in the laboratory. One of the most important professional merits of Elissaveta Bozilova, in addition to her intensive research and teaching activities, was the organization of the Laboratory of Palynology at the Department of Botany, which she administrated successfully until 2000. The laboratory established itself as the leading national centre in fundamental and applied palynology and palaeoecology, where Elissaveta Bozilova supervised over 25 master and doctoral students from several generations, most of them being engaged today either in research or teaching in the broad Communicated by F. Bittmann.

PECULIARITIES OF COAL SEAM &lt;i&gt;L&lt;sub&gt;3&lt;/sub&gt;&lt;/i&gt; STRUCTURE IN THE KRASNOARMEYSKY COAL-MINING DISTRICT, DONETS BASIN

Formation of l3 coal seam rock massif in the Krasnoarmeysky district occurred in active tectonic setting that evidenced by its thickness and one of interlayers and composition. Identical interlayer characteristics of CC Krasnolymanska and Almazna coal mine production fields speak about simultaneous and drastic changes of peat sedimentation. The studies have proved decreasing of coal seams thickness and increasing of their quantity westward to the Ukrainian Shield. Present-day structure of coal rock massif testifies of significant tectonic impact onto sedimentation processes during a basin formation and post-formation period.

A 2,500-year record of environmental change in Highlands Hammock State Park (Central Florida, U.S.A.) inferred from siliceous microfossils

Analysis of siliceous microfossils of a 79 cm long peat sediment core from Highlands Hammock State Park, Florida, revealed distinct changes in the local hydrology during the past 2,500 years. The coring site is a seasonally inundated forest where water availability is directly influenced by precipitation. Diatoms, chrysophyte statospores, sponge remains and phytoliths were counted in 25 samples throughout the core. Based on the relative abundance of diatom species, the record was subdivided into four diatom assemblage zones, which mainly reflect the hydrological state of the study site. An age-depth relationship based on radiocarbon measurements of eight samples reveals a basal age of the core of approximately 2,500 cal. yrs. BP. Two significant changes of diatom assemblage composition were found that could be linked to both, natural and anthropogenic influences. At 700 cal. yrs. BP, the diatom record documents a shift from tychoplanktonic Aulacoseira species to epiphytic Eunotia species, indicating a shortening of the hydroperiod, i.e. the time period during which a wetland is covered by water. This transition was interpreted as being triggered by natural climate change. In the middle of the twentieth century a second major turnover took place, at that time however, as a result of human impact on the park hydrology through the construction of dams and canals close to the study site.

Effect of recent climate change on Arctic Pb pollution: A comparative study of historical records in lake and peat sediments

Historical changes of anthropogenic Pb pollution were reconstructed based on Pb concentrations and isotope ratios in lake and peat sediment profiles from Ny-Ålesund of Arctic. The calculated excess Pb isotope ratios showed that Pb pollution largely came from west Europe and Russia. The peat profile clearly reflected the historical changes of atmospheric deposition of anthropogenic Pb into Ny-Ålesund, and the result showed that anthropogenic Pb peaked at 1960s–1970s, and thereafter a significant recovery was observed by a rapid increase of 206Pb/ 207Pb ratios and a remarkable decrease in anthropogenic Pb contents. In contrast to the peat record, the longer lake record showed relatively high anthropogenic Pb contents and a persistent decrease of 206Pb/ 207Pb ratios within the uppermost samples, suggesting that climate-sensitive processes such as catchment erosion and meltwater runoff might have influenced the recent change of Pb pollution record in the High Arctic lake sediments.

Holocene environmental changes in northern Mongolia inferred from diatom and pollen records of peat sediment

The Holocene paleoenvironment in Nur sphagnum bog, northern Mongolia, was reconstructed by diatom, pollen analysis and measurement of chemical properties on a 3.7m long peat boring sample. Development processes of peatland are well reflected in these multiproxy records, showing that peat accumulation started as early as 9kacalBP, and the present acidic peat bog was established no later than 6kacalBP. Synchronous trends in diatom and pollen assemblages revealed wetter climate in the early Holocene and extensive drought in the mid-late Holocene centered at 5900–2800calBP as a result of temperature increase and low precipitation. Periods of shifts in proxy data were potentially correlated with other studies in not only Mongolia and Siberia, but also the North Atlantic Ocean, and the climatic periods at 8.4 and 2.8kacalBP were highly significant. However, responses to climate changes seem regionally varied in time and strength, demonstrating that local differences in vegetation and orography greatly influence the balance of precipitation and evapotranspiration. Climate changes that coincided in time with the Medieval Climate Anomaly and Little Ice Age were observed as wetter (1200–980calBP) and drier (370–240calBP) conditions, probably caused by meridional shifts of westerlies.

Flexible paleoclimate age-depth models using an autoregressive gamma process

Radiocarbon dating is routinely used in paleoecology to build chronolo- gies of lake and peat sediments, aiming at inferring a model that would relate the sediment depth with its age. We present a new approach for chronology building (called \Bacon) that has received enthusiastic attention by paleoecologists. Our methodology is based on controlling core accumulation rates using a gamma au- toregressive semiparametric model with an arbitrary number of subdivisions along the sediment. Using prior knowledge about accumulation rates is crucial and in- formative priors are routinely used. Since many sediment cores are currently ana- lyzed, using difierent data sets and prior distributions, a robust (adaptive) MCMC is very useful. We use the t-walk (Christen and Fox, 2010), a self adjusting, robust MCMC sampling algorithm, that works acceptably well in many situations. Out- liers are also addressed using a recent approach that considers a Student-t model for radiocarbon data. Two examples are presented here, that of a peat core and a core from a lake, and our results are compared with other approaches. Past climates and environments can be reconstructed from deposits such as ocean or lake sediments, ice sheets and peat bogs. Within a vertical sediment proflle (core), mea- surements of microfossils, macrofossils, isotopes and other variables at a range of depths serve as proxy estimates or \proxies of climate and environmental conditions when the sediment of those depths was deposited. It is crucial to establish reliable relationships between these depths and their ages. Age-depth relationships are used to study the evolution of climate/environmental proxies along sediment depth and therefore through time (e.g., Lowe and Walker 1997). Age-depth models are constructed in various ways. For sediment depths containing organic matter, and for ages younger than c. 50,000 years, radiocarbon dating is often used to create an age-depth model. Cores are divided into slices and some of these are radiocarbon dated. A curve is fltted to the radiocarbon data and interpolated to obtain an age estimate for every depth of the core. The flrst restriction to be considered is that age should be increasing monotonically with depth, because sediment can never have accumulated backwards in time (extraordinary events leading to mixed or reversed sediments are, most of the time, noticeable in the stratigraphy and therefore such cores are ruled out from further analyses). Moreover, cores may have missing sections, leading to ∞at parts in the age depth models.