Peat Sections Research Articles

КОРРЕЛЯЦИЯ ТОРФЯНЫХ РАЗРЕЗОВ НИЖНЕГО ПРИАМУРЬЯ ПО РЕЗУЛЬТАТАМ РАСЧЕТА ОТНОСИТЕЛЬНОЙ ПАЛЕОНАПРЯЖЕННОСТИ

The paper considers the possibility of determining the age and correlating peat sections by solving the inverse problem of magnetostratigraphy based on the findings of comprehensive (palaeomagnetic, petromagnetic, microprobe, and radiocarbon) studies on peats of the «Tyapka» and «Chlya» peat sections in the Lower Amur region. For this purpose, we used the values of relative paleointensity calculated following the technique described by Bagina-Petrova. There is no difference in the rate of magnetization fixation among studied peat samples, and the age of magnetization is comparable to the age of the peat deposits itself. The solution of the inverse problem of magnetostratigraphy using the values of relative paleointensity can be used to correlate peat sections among themselves and to estimate the rate of peat accumulation in different periods of the Holocene, even in the absence of radiocarbon dating for one of the correlated sections.

Above and belowground carbon stocks among organic soil wetland types, accounting for peat bathymetry

Wetlands are widely recognized for their carbon (C) sequestration capacity and importance at mitigating climate change. Yet, to best inform regional conservation planning, the variability of C stocks among wetland types and between above and belowground compartments requires further investigation. Additionally, the bathymetry of peat basins has often been ignored, with soil C stock calculations mostly relying on the thickest peat section, potentially leading to overestimates. Here, we sampled vegetation and soil of 57 wetlands of southeastern Canada to characterize the variability of above and belowground organic C stocks among four wetland types: open bogs, open fens, swamps, and forested peatlands. We also compared carbon stock estimation approaches considering peat bathymetry or not. Results showed that peat thickness, and thus soil organic C (SOC), varied substantially within sites due to peat basin shapes. Omitting bathymetry led to site-scale SOC overestimates of about 20–38 % on average, depending on the approach used, with wide variability among sites (overestimates up to 200 %). Belowground C stocks varied among wetland types with mean values of 132, 101, 19, and 44 kg C m−2 for bogs, fens, swamps, and forested peatlands, respectively. Aboveground C was nearly zero in open bogs and fens but reached ∼30 % of total C stock in swamps and ∼ 15 % in forested peatlands. C stocks in tree roots and shrubs were negligible. Despite the lower C density (per m2) of swamps and forested peatlands, these ecosystems represented the dominant C stocks at the regional scale due to their abundance in the landscape. Overall, the four wetland types stored an estimated 2–7 times more C than forest per unit area. Evaluating differences in C stocks according to wetland type, while integrating peat bathymetry in calculations, can significantly improve regional wetland conservation planning.

InSAR supported by geophysical and geotechnical information constrains two-dimensional motion of a railway embankment constructed on peat

Rail and road embankments constructed on peatlands are subjected to significant challenges due to the high compressibility of peat. They are, therefore, susceptible to considerable settlement following construction. Accurate and timely monitoring of such embankments is important in order to enable proactive intervention strategies and to avoid failures. Multi-temporal Synthetic Aperture RADAR Interferometry (MT-InSAR) techniques applied to satellite-derived SAR data have been shown to be effective for remotely measuring and monitoring the deformation of civil engineering infrastructure. This paper presents a comprehensive approach, involving MT-InSAR supported by local geophysical and geotechnical information, for the detection and investigation of the movement of a railway embankment constructed on peatland. The Small Baselines approach, implemented in StaMPS (referred to as StaMPS-SB), was performed to measure long-term deformation of the embankment in vertical, horizontal east-west and satellite line-of-sight (LOS) directions. In this regard, a Sentinel-1 A/1B dataset composed of 362 descending images, acquired from 2015 to 2022, was analysed to measure LOS displacement. Also, 282 Sentinel-1 A/1B images of both ascending and descending tracks, collected from 2017 to 2022, were analysed to obtain vertical, horizontal and LOS displacements. According to the results, the maximum ground motion rate along the LOS direction was −29 mm/year for the period from 2015 to 2022. However, from 2017 to 2022, this value was about −25 mm/year and − 22 mm/year for descending and ascending tracks, respectively. During this period, the maximum motion rate obtained was −23.1 mm/year in the vertical direction. Moreover, horizontal movement up to −10 mm/year was observed in the westward direction and + 7 mm/year in the eastern direction. We used in-situ data to support corroborate and improve our interpretation of the InSAR results. In this context, peat thickness profiles, records of tamping activities and interpretations of the railway ballast base from ground penetrating radar data, were employed. The in-situ data revealed that the embankment section exhibiting the greatest vertical motion detected by InSAR corresponds closely to the thickest section of railway ballast, the zone of greatest number of tamping activities and the deepest section of peat. As such, this case study highlights how remote detection of embankment motion, coupled with targeted in-situ investigation, can underpin proactive intervention to improve safety.

Indicators of paleocryogenic processes that disrupt the patterns of peatland autogenic development in the zone of seasonal freezing of rocks of Western Siberia

Оn the data of detailed studies in 2003-2019 and dating of 14C, AMS, 210Pb and 137Cs peat sections of the zone of seasonal freezing of rocks of Western Siberia indicators of paleocryogenic processes were searched. The functional state of these peatlands was reconstructed as a response to continental climate changes. A system-evolutionary methodological approach to the search for disturbances of autogenic development of peatlands, dating of pairs of neighboring peat samples to identify the peat accumulation stopping, data on peat sections - analogues from the permafrost zone and data on paleoreconstructions of the Holocene climate of Western Siberia were used. This allowed indicators of paleocryogenic processes to be proposed. The use of these indicators will increase the objectivity of studying the climatic paleoreconstructions of the territory.

On the question of the distribution of Coniferous Island in the north of the Central Kamchatka Depression in the Holocene

Despite the long history of studying the conifers dispersal in the Central Kamchatka Depression during the Holocene, the understanding of vegetation dynamics in the northern part of the depression is much weaker due to the lack of palynological sections. Pollen analysis of a peat section located to the southwestern of Shiveluch volcano allowed an assessment of the "Coniferous Island’s" expansion dynamics in the northern part of the Central Kamchatka Depression. According to the data obtained, the expansion of larch forests in this area began about 700 cal. yrs. BP, i.e. 100-150 yrs. later than in the southern part of the depression. Spruce, which replaces larch during succession, began to spread here about 400 cal. yrs. BP, as in the rest of the depression.

Assessment of Holocene climate influence on hydrothermal regime of paleoecotopes within Ryams of the Baraba forest-steppe (southern Western Siberia)

A clearly defined trend of alterations in the properties of peat across the depth of the deposit has been observed in the two studied ryams of the Barabinsk forest-steppe. The changes in peat properties influenced by external factors outweigh those induced by autogenic development of the bog. In order to achieve an accurate reconstruction of changes in the water regimes of ryams, it is essential to consider that the properties of peats reflect not only the state of the water regime at the time of their deposition but also subsequent changes over time. Both peat sections exhibit a catastrophic transition from the eutrophic to the oligotrophic stage of development approximately 4100 and 1100 years ago.

Stratigraphy of peat deposits and mire development in the southernpart of the forest zone of Western Siberia in Holocene.

This article provides a historical review of the peatlands study in the Middle and South taiga, as well as Subtaiga zone of Western Siberia, and summarizes the data on the structure of peat deposits in mires of the region, accumulated by the senior author over many years of field research (1980-2004). The features of the main types of stratigraphic structure, as well as a description of the development history of peat mires, are given based on a detailed study of macrofossil composition of peat cores and peat sections. Peat cores were selected within the landscape-ecological profiles, covering all relief elements from the raised bogs of the watershed plains to the mires of river valleys and gullies of ancient water runoff in different climatic zones and subzones (Subtaiga, Southern taiga and Middle taiga). The oldest peat deposits are associated with the deep thalwegs and ancient hydrological system. Peat formation started simultaneously within the taiga zone and the present subarctic zone of Western Siberia and reached the high distribution level in Boreal period. The peatlands development process tightly followed the climate humidity in the wet periods, the watershed mires actively developed and floodplain mires development was constrained by the alluvial deposition process; in the dry periods, the floodplain mires developed actively and the watershed mires grow was stagnated.

PEAT DEPOSITS AS A NEW SOURCE OF PALEOMAGNETIC RECORDS IN THE HOLOCENE AS EXEMPLIFIED BY THE ETRUSSIA EXCURSION

The paper presents the results of microprobe, paleomagnetic and rock magnetic studies on peats from the Tyapka peat section (Khabarovsk region) formed 4 thousand years. Alternating field demagnetization of peats yielded a horizon of 57–109 cm (1833–3083 cal. BP) with negative inclination values of the magnetization vector, which corresponds to the geomagnetic Etrussia excursion. Obtaining relative paleointensity estimates for peats was pioneered, which are consistent with the literature archeomagnetic data for the western part of Eurasia. It was found that the Etrussia excursion took place against the background of increased values of the Earth’s magnetic field, and its duration was ~ 1200 years.

Holocene permafrost peatland evolution in drained lake basins on the Pur-Taz Interfluve, North-Western Siberia

The permafrost properties and cryostructure of Holocene peatlands and underlying the Pre-Holocene deposits within Pur-Taz interfluve in the Northern West Siberia were studied. The cryolithological description, particle size, botanical compositions based on plant macro-fossils, and radiocarbon age from 8500 ± 240 cal BC to 1810 ± 150 cal AD were defined. The polygonal peatlands were formed in lacustrine-bog basins. The “arboreal” horizon at the bottom of the peat, which is characteristic of Northern West Siberia, was identified. This “arboreal” horizon dates to the Boreal and Atlantic periods of the Holocene – 8500 ± 240 cal BC and 7390 ± 210 cal BC, which explains the occurrence of forest tundra in the area of typical modern tundra during the Holocene Climatic Optimum. The vegetation composition of peat-forming plants, the ash content, and the decomposition degree of organic matter were controlled by changing natural conditions and dynamics of peat accumulation during the Holocene: flooding and burial of woody vegetation, overgrowing and eutrophication of water bodies, the gradual accumulation of peat and syngenetic ice-wedge polygon formation, peat accumulation slowing caused by drainage of drained lake basin surface. Organic frost boils on the peatland surface indicate modern deepening of the permafrost Table and are related to an increase of the microorganism activity in the thawed, poorly decomposed peat. The peat accumulation rate was about 1 mm per year. A 2-m peat layer containing ground ice has accumulated over 2500 years.The purpose of the present work is study of the history of the vegetation on the northern limits of treeline. Examination of the peat, macrofossil, decomposition degree, and ash content history of a peat sections on the Pur-Taz Interfluve in North-Western Siberia, provides a long-term view of vegetation dynamics, peatland change, and climate history during the Holocene at the Arctic treeline.

Assessment of the Impact of Anthropogenic Drainage of Raised Peat-Bog on Changing the Physicochemical Parameters and Migration of Atmospheric Fallout Radioisotopes in Russia’s Subarctic Zone (Subarctic Zone of Russia)

This paper reports on the research results of the radioactivity levels and upward dispersion of radionuclides of atmospheric fallout 210Pb, 137Cs, 241Am and 234,238U as well as key physicochemical parameters in a peat deposit subjected to drainage in 1969–1971. It was found that drainage of the peat bog led the natural moisture content to shrink in the peat. Active aeration in the peat deposit, accompanied by the growth of Eh, raises the strength of oxidative transformation processes of the organic part of the peat, leading to higher levels of peat degradation and major variations in the elemental content. Changes in these parameters affect the behaviour of radionuclides in the peat section. Thus, in contrast to the sites with a natural hydrological regime, within the dried peat deposit a geochemical barrier of sorption type is not formed, capable of retaining a significant proportion of 137Cs. In this connection, there is an acceleration of 137Cs migration. In addition, changes in the hydrological regime led to the predominance of vascular plants with a more developed root system than that of sphagnum, which also contributed to a more intense transfer of 137Cs by the root system up the section. The findings of 210Pb dating of the dried peat bog showed a significantly lower peat accumulation rate compared to the natural bog massif (0.15 ± 0.02 vs. 0.48 ± 0.08 cm/year). A factor examination of the dataset demonstrated that the leading role in the distribution of radionuclides belongs to redox and acid-base conditions, which have changed significantly after draining the peat deposit.

Middle to late Holocene lake level changes of Lake Sevan (Armenia) – Evidence from macro and micro plant remains of Tsovinar-1 peat section

In the Caucasus, peat deposits exposed near Lake Sevan (Armenia) provide a Middle to Late Holocene record of lake level fluctuations. The Tsovinar-1 section at the southern shore of Lake Sevan in the Armenian Highlands reveals a well-dated and divers pollen and carpo-flora covering a time span from 6000 BC to 900 AD. The abundances of pollen of forest taxa in relation to steppe vegetation indicate climatic changes through time. In parallel, the presence and number of fossils of aquatic and wetland plants, both in micro and macro floras, provide information about the presence of water and allows estimating changes of water depth. Characteristic taxa pointing to deeper water at Tsovinar-1 are Myriophyllum sp., Ceratophyllum demersum, and several species of Potamogeton. In shallow water, Persicaria amphibia,Sparganium sp., and Typha sp. dominate. In fluctuating water and wetlands those plants are replaced by Menyanthes trifoliata, Ceratophyllum submersum, Alisma sp., and others. High lake levels can be inferred at 6000−5000 BC, 1700−900 BC and 200−900 AD and are associated with humid climate and the development of forest vegetation. Low lake levels occurred at 4000−2600 BC and 600 BC−100 AD corresponding to epochs of decreased humidity and expanded steppe vegetation. Macro and micro remains of plants from the Tsovinar-1 site serve as reliable sources of information for determining environmental changes over time, which are in accordance with archaeological data from the region showing the effects of lake level changes on human activities․

Late-Holocene wildfire record from the Stagmo peat section, Leh valley, NW Himalaya

Wildfire is an integral component of the terrestrial ecosystem that plays a significant role in regulating the vegetation cover. The paleofire records stored in lacustrine, peat, or marine sedimentary deposits along with environmental proxy records provide temporal information on fire activity and contemporary climatic conditions on a regional scale. A ~2.8m long peat sedimentary profile from Stagmo, Indus Valley, Ladakh Himalaya was examined for sedimentology and charcoal microfossil contents to investigate fire characteristics and reconstruct wildfires which are compared with paleoclimatic changes and past human activities to assess their significance in biomass burning. Charcoal count (CC) analysis provides a suitable method for investigating climatic and vegetation changes with human intervention when no direct evidence is available in the Late-Holocene Trans Himalaya records. The results bring new insight into the interaction between vegetation, fire, and human activity in the Ladakh Himalaya during the past ~2.8 cal kyr BP. An event characterized by high CC at ~2.8 cal kyr BP is distinct from the whole sequence and cannot easily be explained as only the result of a climatic event. This first high charcoal count phase (2.81–2.55 cal kyr BP) could be a natural response to the expansion of forest and dense vegetation with human management interruption. This paleo wildfire event likely corresponds with the time of the Tibetan Plateau’s immediate human occupation. In the second phase, a relatively low charcoal count (1.65–1.54 cal kyr BP) is supported by the high fuel availability during a transitional phase. The third phase of wildfire reconstruction in Ladakh Himalaya is identified at ~1.38 cal kyr BP. This phase can be correlated with the intensified Indian Summer Monsoon (ISM) advancing to Trans-Himalaya leading to increased human settlement in the region.

Atmospheric Anomaly Bioindicators in Peat Sections on the Eastern Macroslope of the Sikhote-Alin Range in the Late Holocene

Atmospheric Anomaly Bioindicators in Peat Sections on the Eastern Macroslope of the Sikhote-Alin Range in the Late Holocene

БИОИНДИКАЦИОННЫЕ ПРИЗНАКИ АТМОСФЕРНЫХ АНОМАЛИЙ В РАЗРЕЗАХ ТОРФЯНИКОВ НА ВОСТОЧНОМ МАКРОСКЛОНЕ СИХОТЭ-АЛИНЯ В ПОЗДНЕМ ГОЛОЦЕНЕ

Studies of peat stratigraphy in the upper reaches of the Milogradovka River made it possible to restore changes in humidity as a source of moisture in the middle Sikhote-Alin over the last 3400 years. High-resolution reconstructions were based on the data from biostratigraphic analyses (botanical and diatom); the ash content of peat was also studied. Radiocarbon dating of the events was performed using an age-depth model. In the upper part of the section, the B-Tm cryptotephra of the Baitoushan caldera-forming volcano was found, which was identified by the volcanic glass chemical composition. Prolonged rains are assumed to cause a massive landslide with the formation of a dam and a shallow reservoir turning the river valley into a swamp. Bioindicators of changes in humidity in the river valley and the occurrence of floods were identified. Events were correlated with the data for the main watershed of the Sikhote-Alin, mountainous plateaus, lakes on the slopes of the ancient Solontsovsky volcano and the eastern Primorye coast. The peat section in the valley is shown to record in more detail the hydrological changes associated with the nature of cyclogenesis. A relationship was revealed between paleoevents and anomalies of large-scale atmospheric circulation. Long dry phases occurred during global cooling and were accompanied by aridization in East Asia, caused by a decrease in the intensity of the East Asian summer monsoon. Studies show that floods occurred in the summer to autumn season even in dry phases. The phases of flooding were associated with the activation of the summer monsoon, as well as more intense cyclogenesis. The most complex climate rhythm was established for the last 1340 years.

Геологические свидетельства проявлений сильных цунами на побережье острова Итуруп (Курильские острова) за последние 3500 лет

The distribution of tsunami deposits in the lacustrine-swamp sections on the Kasatka Bay coast is analyzed. The main objects were a swamp formed on the place of overgrown lagoon-type lake located behind dune ridge, and a low swampy isthmus between Oktyabrskoe and Srednee lakes. Five major events have been identified, run-up parameters and age have been determined on the base of radiocarbon dating and tephrostratigraphy. Diatom analysis data were used to confirm the marine origin of the sand. Established events are correlated with data on adjacent islands and the Eastern Hokkaido coast. A trace of only one strong historical tsunami was found, its deposits lie above marking volcanic ash Ta-a (1739) of the Tarumai Volcano, Hokkaido. The tsunami took place in the second half of the 18th century. Perhaps this is a trace of 1780 AD tsunami, the source was located near Urup Island. Four paleotsunamis are well compared in age with the megatsunamis of the region (17th, 13th centuries, 1.5; 2.3–2.4 ka), which most clearly manifested on the Eastern Hokkaido coasts and left sea sands and silts sheets in marshes of the Lesser Kuril Ridge and Kunashir Island. On Iturup, the thickness of tsunami deposits and wide of sand cover is much less. It has been suggested that the peat section of Iturup recorded the run-up values in the distal zone of the Late Holocene megatsunami, which had sources in the southernmost of the Kuril-Kamchatka Trench. Regional strong tsunamis occurred in the period of instrumental observations did not leave geological evidence in the studied sections.

Сравнение моделей 210Pb-датирования применительно к торфяным отложениям Европейской Субарктики России (на примере Архангельской области)

The dating of young peatlands with 210Pb method is a difficult task. Standard 210Pb dating models require an exponential decrease in activity down the peat profile. In Arctic peatlands, we note a significant migratory capacity of lead, therefore, for accurate dating of peat, it is necessary to improve the existing dating models to eliminate the effect of migration and their verification using independent isotope chronometers, for example, 137Cs. We applied several models CA, CFCS, PF, CF together with the Monte Carlo method for peat core samples taken within the European Subarctic of Russia (Arkhangelsk region). Comparison with the specific activities of 137Cs, determined at a depth of 19—21 cm, associated with the global fallout in 1963, showed that the closest age to the specified reference point is given by the CFCS and CF models (1965 and 1962, respectively). Among these two options, CF using the Monte Carlo method turned out to be preferable, since it provided, taking into account the error, a slightly better agreement with the specific activities of 137Cs in the reference horizon. Despite the difficulties associated with the complex distribution of 210Pb over the peat section due to migration, the dating methods used were successful and, in the future, can be applied to dating other peat deposits.

Geochemistry of Early Diagenesis of Bog Deposits by the Example of the Holocene Section of the Dulikha Peat Bog (Eastern Baikal Region)

Abstract —Two cores of the Dulikha peat bog deposits, 4.0 and 5.2 m thick, were studied in detail. The reduction type of diagenesis has been established. Decomposition of the organic matter of the bog deposits begins already in the upper intervals of the section at the earliest stages of diagenesis. Microbiological studies of the peat bog revealed numerous organotrophic, ammonifying, nitrifying, and phosphate-mobilizing microorganisms as well as Fe-Ox and Mn-Ox microorganisms and showed the almost complete absence of sulfate-reducing bacteria (except for the lower intervals of the peat section). The processes of the nitrogen, phosphorus, and carbon cycles are more active than the sulfur cycle processes. The chemical composition of the bog water changes during diagenesis. The contents of HCO3-, NH4+, PO43-, NO3- and Corg increase in the peat bog section, which is the result of the destruction of organic matter, leading to the transition of the most mobile and labile components into the bog water. The results of physicochemical modeling show that the high content of organic matter significantly changes the chemical composition of the bog water. The enrichment of the latter in Cu, Zn, Sr, Ba, As, Si, Al, and Pb indicates a diagenetic transformation of the bog deposits. A change of oxidizing conditions by reducing ones in the peat bog leads to the reduction of oxidized Fe (III) and Mn (IV) forms to mobile Fe (II) and Mn (II) forms and their subsequent migration from the solid phase of deposits into the bog water. With depth, the reduced S (II) forms become predominant in the peat, which indicates more reducing environmental conditions. The concentration of SO42- decreases in the pore water of the peat-underlying mineral deposits, which marks the beginning of sulfate reduction. This process, however, is very slow in the bog deposits because of the acid environmental conditions and the lower degree of transformation of organic matter.

Mid-Late Holocene vegetation and hydrological variations in Songnen grasslands and their responses to the East Asian Summer Monsoon (EASM)

Exploring the Mid-Late Holocene interactions between ecological and climate variations in semi-arid areas such as Songnen grasslands (northeastern China) provide insights into how future vegetation changes and hydrological variations may have an impact on semi-arid ecosystems, in general. In this study, we present a high-resolution palaeoecological dataset covering the past 7300 years. For this purpose, a peat section has been sampled from the shore of Dabusu lake situated in the southwestern part of the Songnen grasslands. We use pollen analyses to reconstruct the regional and local vegetation dynamics, and measure TOC (total organic carbon) and the degree of peat humification to study changes in regional and local biomass. Diatom analysis, grain size analysis, and CaCO3 contents are used to assess the water-table fluctuations of the Dabusu peatlands. The results show that from 7300 to 6000 cal BP, Dabusu peatlands were characterized by grasslands, dominated by Poaceae plants and high-water level. From 6000 to 910 cal BP, forest-steppes and dry-steppes dominated in the region alternatively. The water level of Dabusu peatlands experienced relatively low levels following an earlier rapid decline around 6000–5100 cal BP. Then after a slight increase between 5100 and 4000 cal BP, it remained at a relatively low level until 910 cal BP. After 910 cal BP, steppe vegetation dominated in the region and the water level of Dabusu peatlands slightly rose. By comparing these features with regional climate change, we show that EASM circulations might be the main driving forces controlling the regional paleovegetation dynamics and hydrological variations. This outcome is critical for the understanding of the long-term interactions between vegetation, hydrology, and climate of mid-latitude semi-arid grasslands.

СТРАТИГРАФИЯ И ДИНАМИКА АККУМУЛЯЦИИ ТОРФА И УГЛЕРОДА НА РЯМАХ БАРАБИНСКОЙ ЛЕСОСТЕПИ В ГОЛОЦЕНЕ (ЗАПАДНАЯ СИБИРЬ)

Detailed studies of the properties and dating (13 14C dates) of peat sections of the Sherstobitovo and Ubinskoe burnt ryams were carried out. The first data on the dynamics of peat and carbon accumulation in the oligotrophic bogs of the Baraba forest-steppe of West Siberia in the Holocene were obtained. The peat deposits of these sections, respectively, are mixed multilayer forest-swamp and high moor fuscum, 2.5 and 3.47 m thick, 5254 and 6472 cal. years ago, with total reserves of absolutely dry peat – 200 and 267 kg m–2 and carbon – 91 and 124 kg C m–2. The long-term peat accumulation rates are 37.6 and 40.9 g m–2 yr–1, carbon – 17.1 and 19.0 g C m–2 yr–1, the limits of variation of peat accumulation rates in various periods of bog formation are 14.2–78.8 and 14.8–59.0 g m–2 yr–1, carbon – 6.7–32.6 and 6.8–27.5 g C m–2 yr–1. The dependence of peat accumulation dynamics on the hydrothermal climate regimes of the second half of the Holocene, the genesis and age of sections, and the local conditions of their formation is revealed. The confirmed deposition of peats on lake sapropels and organomineral deposits of reed inundated plains occurred after periods of climate aridization. Significant differences between the subsequent dynamics of peat accumulation and presence and location of primary lakes in bog massifs were revealed.

The Early Neolithic–Middle Bronze Age environmental history of the Mamakan archaeological area, Eastern Siberia

This study presents the first radiocarbon-dated palynological record from a peat section (57°49′10.03"N; 114°03′31.37"E, 251 m above sea level) in the Mamakan area located in the lower Vitim River valley, about 350 km northeast of Lake Baikal. While the area is particularly renowned for its numerous multi-layered Upper Palaeolithic (ca. 50,000–14,000/10,000 cal yr BP) archaeological sites with rich cultural assemblages, there is also evidence for human occupation during the Mesolithic–Neolithic–Bronze Age period (ca. 14,000/10,000–3000 cal yr BP). However, the absence of accurately dated palaeoenvironmental records does not allow discussion of prehistoric human–environment interactions in this area. The records of pollen, spores and other non-pollen palynomorphs (NPPs) from the Mamakan site presented in this article document changes in the vegetation and climate of the study area between 6570 and 3630 cal yr BP. From 6570 to 6200 cal yr BP the vegetation around the site was dominated by sparse forests of mainly spruce and larch, indicating that the permafrost layer was located relatively close to the surface. Fir was part of the forest communities in habitats with a milder microclimate and a deeper permafrost layer. Around 6200 cal yr BP Scots pine started to spread across the study area. Until 4670 cal yr BP it dominated the pollen spectra of the Mamakan record, indicating warmer conditions. Climate cooling and higher soil moisture is indicated by the spread of Siberian pine and Siberian dwarf pine at the expense of Scots pine between 4670 and 3840 cal yr BP. From 3840 cal yr BP the Mamakan record suggests a landscape opening associated with the spread of Sphagnum-dominated bog vegetation and an increase in the occurrence of wildfires (3870–3820 cal yr BP), which were either natural in origin or caused by human activities. The spread of Scots pine paralleled by a decline in dark conifers (spruce and fir) and larch in the Lake Baikal Region (LBR) has been linked to a ‘hiatus’ in the Cis-Baikal archaeological records of the Middle Neolithic (6660–6060 cal yr BP). Around the Mamakan site this vegetation change occurred comparatively late, about 600 years later than in the regions around and east (e.g. Lake Baunt area) of Lake Baikal. The Mamakan pollen and NPP records, together with the available archaeological data, suggest that the environmental conditions in the lower Vitim River area may have sustained the hunter-gatherer lifestyle also during the ‘hiatus’ interval.