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This paper describes an approach assuming that already in the sea, based on the express analysis of visually similar cores of Arctic Holocene sediments and their comparison with dated and studied in detail cores of the regional sediments, it is possible to select a material that is promising for sequence stratigraphic correlation and paleoreconstructions. The range of lithological, colorimetric (CIE L*, CIE a*, and CIE b*), geophysical (magnetic susceptibility), and geochemical (Fe/Rb, Mn/Rb, and Ti/Rb) parameters is analyzed. The most informative characteristics include the CIE b* color coordinate, magnetic susceptibility, and Fe/Rb. [ABSTRACT FROM AUTHOR]

The paper presents the results of comprehensive (microprobe, paleomagnetic and magnetic) studies on peats from the Tyapka peat section (Russian Far East). Radiocarbon dating placed the start of peat formation at ∼11.7 ky B.P. The principle carriers of magnetization were found to be magnetite, to a lesser extent hematite and, possibly, greigite. The relative paleointensity values obtained through calculations are in good agreement with the literature data. Intervals with negative inclinations of the magnetization vector were identified in peats, which most likely correspond to geomagnetic excursions in the Holocene. The research constrained the duration of the geomagnetic excursions, as well as the geomagnetic field intensity behavior not typical for such variations. [ABSTRACT FROM AUTHOR]

This paper presents data on new finds of remains of Mammoth fauna mammals in the Middle Lena River basin (Lena Pillars Nature Park (Yakutia) and adjacent areas). Based on these data, a list of the main localities for large mammal species in this region was compiled. Eleven species of large mammals are identified, among which, the cave lion Panthera spelaea is reported for the first time for this region. A series of new radiocarbon dates allows us to conclude that there was a mass burial of Neopleistocene mammalian remains in this region during the Karginian interstadial (60 (55)–24 kyr ago, MIS-3). The radiocarbon dates obtained and species composition are consistent with the data that the Karginian interstadial was the most favorable for the distribution of the Mammoth fauna in the territory of Yakutia. The study results show that the ecological distribution of Ovis nivicola in the Late Pleistocene differs from its present-day habitat area. [ABSTRACT FROM AUTHOR]

In this paper we restore moisture changes since the Younger Dryas based on the study of diatom flora in sediments of the Zelenyi coastal paleolake, the Lesser Kuril Ridge. The section includes numerous interlayers of tephra, the sources of which were located on the islands of Kunashir and Hokkaido, and interlayers of tsunamigenic sands, which made it possible to determine the impact of catastrophic events on changes in the ecological situation. The stages of the development of the lake are identified and its evolution is analyzed during short-period climatic rhythms. The reservoir had its maximal depth at the beginning of the Holocene, and planktonic forms predominated among diatoms. Three phases when the lake turned into a lagoon were established, and the erosion of the barrier form most likely caused this during large tsunamis associated with earthquakes. Except for these cases, the main factor leading to the change in lacustrine–marsh environments was climate change. We identified relatively dry periods and wet periods associated with an increase in the intensity of cyclogenesis in the South Kurils region. We correlated with high-resolution paleoclimatic records from archives for the Southern Kuriles; the most striking events were compared with data for Sakhalin and the continent. Changes in moisture on the islands and the margin of the mainland in the Middle–Late Holocene were established to be in antiphase in most cases, except for the cooling of 2800–2500 BP and the Little Ice Age. The connection of regional climatic changes with anomalies in the ocean and atmosphere of the Asia-Pacific region is shown. [ABSTRACT FROM AUTHOR]

The paper presents new paleobotanical data in combination with the results of radiocarbon dating obtained from organomineral deposits of the northern shore of Pechevalavato Lake (70°13′22.3″ N, 71°50′57.6″ E) in the Seyakha River basin and characterizing the dynamics of vegetation in the northern part of Central Yamal in the Holocene. It has been shown that a tree birch (Betula sect. Betula) grew in Yamal in the early Holocene (10.2–8.7 cal kyr BP) no less than 400 km north of the modern northern limit of distribution of Betula pubescens ssp. tortuosa. Favorable conditions for the existence of birch woodlands at this time were provided by a higher temperature of the growing season, exceeding the modern parameters of the warmest month of the summer season by approximately 3–4°C. At the end of the early Holocene (after 8.5 cal kyr BP), forest vegetation began to degrade, and open landscapes with diverse plant communities of the subarctic tundra and single trees in the river valley spread. About 6.5 cal kyr BP, the northern subarctic tundra began to form the zonal appearance of the study area in climatic conditions close to modern ones. [ABSTRACT FROM AUTHOR]

The paper presents data on the geochemical processes of postsedimentation transformations of boggy deposits at early diagenesis and the redistribution of chemical elements, including biogenic ones, in the Holocene sections of peat bogs in the Baraba forest-steppe in southern West Siberia. The contents of Fe, Mn, Pb, Hg, Sb, Cd, Cu, and Zn were found out to increase in the upper layers of the peat, whereas the S, N, Ca, and Sr concentrations increase in the middle parts of the peat profiles. The distribution character of various physiological groups of microorganisms in the peat profiles of Ubinskoe and Sherstobitovo peatlands lead to the conclusion that the nitrogen and carbon cycles are more active than that of sulfur. The activity of microorganisms leads to a decrease in pH and Eh in the vertical sections of the peatlands. The high values of , , TOC, and the chemical oxygen demand in the bog waters of Ubinskoe and Sherstobitovo bogs indicate that active biochemical decomposition and oxidation of organic matter proceed in these bogs. According to their predominant ions, the waters of the bogs belong to the hydrocarbonate class of the calcium group and are characterized by elevated concentrations of Al, Fe, Cu, and Zn, which is caused by the acid composition of the waters. The low pH values of the bog waters and the oxidizing environment facilitated the development of goethite–hydrogoethite mineralization in the upper horizon of peat profiles. The formation of hematite and anhydrite in the middle parts of the peat profiles was probably caused by paleofires. The authigenic minerals formed in the process of early diagenesis are, first of all, pyrite and less often siderite, calcite, and kaolinite. Under reducing conditions, nanoparticles of native Ni and Ni–Cr intermetallic compounds can be formed, and amorphous silica can be deposited at the dissolution of aluminosilicate minerals from the upper peat horizons. [ABSTRACT FROM AUTHOR]

Sediments from a small lake, Loch Beag, in Barrees, Beara peninsula, south-western Ireland, provide a record of vegetation history that spans most of the Lateglacial and Holocene (14–0.43 ka). The detailed part of the record relates to the Holocene, which is the focus of this paper. The investigations carried out include pollen and macrofossil analyses, loss-on-ignition measurements and 14C dating. As well as providing records for tree and shrub taxa, and especially Pinus, Quercus, Ulmus, Fraxinus and Taxus, other taxa mainly with Atlantic and/or Lusitanian distributions are also considered. These include Arbutus unedo (strawberry tree) and fern species such as Osmunda regalis, and the filmy ferns Hymenophyllum tunbrigense, H. wilsonii and Trichomanes speciosum (Killarney fern). Detailed records for a suite of bog/heath taxa, including ericoid species (Erica tetralix and E. cinerea), Narthecium ossifragum, Hypericum elodes and Myrica gale, are presented. The results of 14C dating of bog-pines from western Ireland are summarised. Results of other investigations, including key Holocene pollen diagrams, and charcoal and fossil-wood records from archaeological excavations that relate mainly to the Bronze Age in the wider west Cork/Kerry region, are reviewed. Vegetation dynamics, human impact and plant biogeography are discussed in the light of the considerable data now available for the region. [ABSTRACT FROM AUTHOR]

Loess, loess-like, sandy loess, and sandy-silty fluvial–aeolian deposits are intercalated to fluvial sediments and lie on a flat surface under intense agricultural land use in Bardibas, Mahottari district, central Nepal. To identify the depositional processes and provenance, we carried out geochemical, mineralogical, SEM, and grain-size analyses. Optically stimulated luminescence (OSL) dating shows the aeolian deposits are from the late Holocene (1.0–4.8 ka). Our results demonstrate that the loess and loess-like deposits (i) were dominantly sourced locally from deflation Quaternary sediments of the Terai Plain; (ii) are related to the composition of Siwalik rocks; and (iii) were deposited during dry periods of weak activity of the Indian Summer Monsoon. [ABSTRACT FROM AUTHOR]

High-resolution dating of volcanic rocks is the foundation for understanding the evolution of volcanoes and for estimating possible hazards. However, dating is often difficult for submarine volcanoes, where radiocarbon or other dating is frequently unavailable or imprecise. Here, we report paleointensity results from submarine basalts around Izu-Oshima Island, a typical island-arc volcano, and their bearing on age constraints. Basaltic lava samples were collected from submarine ridges located southeast of Izu-Oshima Island. Rock magnetic data indicate that the samples contain Ti-rich titanomagnetite with blocking temperatures of around 250–400 °C. The magnetic properties of the samples do not change significantly when heated in Ar or vacuum. We apply the Tsunakawa-Shaw method to estimate absolute paleointensity. Samples from different submarine ridges show distinct behavior. One ridge (SE1) shows moderate paleointensity of about 37 μT, while another ridge (SE3) records relatively strong magnetic fields of about 60 μT. Comparing those results with regional paleointensity data, we estimate the age of the SE1 ridge to be younger than 0.5 ka or around 1.4 ka. The other ridge (SE2) exhibits different paleointensity for two samples obtained from different localities, implying that the ridge consists of multiple eruptions. These results demonstrate that paleomagnetism can improve the dating of submarine volcanic rocks. [ABSTRACT FROM AUTHOR]

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Reconstructing Holocene temperature evolution is important for understanding present temperature variations and for predicting future climate change, in the context of global warming. The evolution of Holocene global temperature remains disputed, due to differences between proxy reconstructions and model simulations, a discrepancy known as the 'Holocene temperature conundrum'. More reliable and quantitative terrestrial temperature records are needed to resolve the spatial heterogeneity of existing records. In this study, based on the analysis of branched glycerol dialkyl glycerol tetraethers (brGDGTs) from a loess-paleosol sequence from the Ganjia Basin in the north-eastern Tibetan Plateau (NETP), we quantitatively reconstructed the mean annual air temperature (MAAT) over the past 12 ka. The MAAT reconstruction shows that the temperature remained low during the early Holocene (12–8 ka), followed by a rapid warming at around 8 ka. From 8 to 4 ka, the MAAT record reached its highest level, followed by a cooling trend from the late Holocene (4–0 ka). The variability of the reconstructed MAAT is consistent with trends of annual temperature records from the Tibetan Plateau (TP) during the Holocene. We attribute the relatively low temperatures during the early Holocene to the existence of ice sheets at high-latitude regions in the Northern Hemisphere and the weaker annual mean insolation at 35°N. During the mid to late Holocene, the long-term cooling trend in the annual temperature record was primarily driven by declining summer insolation. This study provides key geological evidence for clarifying Holocene temperature change in the TP. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is a key region for environmental and climatic research due to its significant linkages with large-scale atmospheric circulation. Understanding the long-term moisture evolution pattern and its forcing mechanisms on the TP during the Holocene may provide insights into the interaction between low-latitude climate systems and midlatitude westerlies. Here, we synthesized 27 paleoclimate proxy records covering the past 9500 years. The results of the rotated empirical orthogonal function analysis of the moisture variation revealed spatial-temporal heterogeneity, which was classified into 5 subregions. Proxy records were then compared with the results from the Kiel Climate Model and other paleorecords. The results showed that moisture evolution on the western-southern-central TP was controlled by the Indian summer monsoon (ISM). On the south-eastern TP, moisture change was affected by the interplay between the East Asian summer monsoon (EASM) and the westerlies, as well as the ISM. With diverse patterns of circulation system precipitation, moisture changes recorded in the paleorecords showed spatial-temporal discrepancies, especially during the early to middle Holocene. Moreover, given the anti-phase pattern of summer precipitation in the EASM area under El Niño/Southern Oscillation (ENSO) conditions and the unstable relationship between the ISM and ENSO, it is reasonable to conclude that relatively strong ENSO variability during the late Holocene has contributed to these discrepancies as Asian summer monsoon precipitation has declined. [ABSTRACT FROM AUTHOR]

Context: The determination of autecological preferences based on long-term vegetation dynamics is hampered by the lack of realistic estimates for past occurrence and abundance patterns. Palaeoecological record has still rather character of points than spatially continuous maps. Objectives: To infer long-term autecological preferences of trees from reconstructed vegetation. Compare reconstructions based on pollen and charcoals. Methods: We employed to the regional training set of 58 sites the Extended Downscaling Approach (EDA) using nine topographic factors clustered in 8 habitat classes, data on pollen productivity estimates, fossil pollen, charcoal sequences from soil and archaeological contexts. Based on abundances and habitat preferences from the last 9 millennia, we calculated the autecological preferences of tree taxa, using multivariate statistics. Results: The significant spatiotemporal patterns between soil-charcoal and pollen-based EDA validated the reconstruction, the use of both records in the EDA, and the EDA model. One of the topographic indices—vertical distance to channel network—evidenced the following: the closest taxon to the groundwater is Picea; Abies, Betula, Pinus and Quercus have intermediate distances; Fagus grows far from the channel network and Corylus even further. Conclusions: The EDA model linked past forest composition to realistic topography. Such a spatially explicit reconstruction produced by our new algorithm allows inferring the relationship between past plant communities and environmental variables. The long-term preferences of tree species to habitat characteristics match their current autecological demands. This might be a breakthrough in quantitative plant paleoecology. [ABSTRACT FROM AUTHOR]

The deposition rate of the floodplain alluvium in various periods of the Holocene is determined for the Istra, Oka, and Seim rivers using a combination of dating methods (radiocarbon, radiocesium, and historical–archeological) and our original method based on estimation of the degree of evolution of the profile of soils buried in the alluvium. The spatial–temporal differences in the floodplain sedimentation rates are established as a result of chronological and soil-geomorphological studies. In the young floodplain areas, the rate is 1.8‒23 (Seim River) and 2‒15 (Istra River) mm/year in contrast to 0.01–0.70 mm/year in ancient areas (Oka and Seim rivers) in various deposition periods and when periods of intensified sedimentation were short. New refined data on typical sedimentation rates in floodplains of the center of the East European Plain are based on the study of the young fast-growing floodplain of the Istra River, the sediments of which are dated on the basis of historical–archeological materials: the sedimentation rate of the alluvium with and without pedogenetic features is 2‒15 and >15 mm/year, respectively, and the cumulative soils accumulate at a rate of 0.5–2 mm/year. Based on the 14С and archeological dates, the cyclic oscillations of the sedimentation rate in the Holocene are established along the Nikitino section (Oka River), which is characterized by a large series of well-developed paleosols: ~2 mm/year during the accumulation of the alluvium layers, which is 20 times higher than during the longer period of soil formation (0.07–0.14 mm/year). [ABSTRACT FROM AUTHOR]

Khorlakel Lake is located in the central sector of the Greater Caucasus, on its northern macroslope. The closed lake lies at an altitude of 2045.0 m above sea level on a tectonically determined subhorizontal step with a height of 2020–2100 m a.s.l. associated with the frontal part of the thrust. Two cores were drilled, and 17 samples for radiocarbon dating were taken in 2017 in the deepest (≈8 m) part of the lake, which made it possible to create an age model for the range from 8000 to 500 yr BP. To interpret the stratigraphic–temporal sequence of lacustrine sediments, integrated geological and geomorphological studies in the catchments of the lake and Elbashi Creek and in adjacent territories were conducted. It was established that sedimentation in the lake is associated with the influence of the adjacent Elbashi Creek. A number of episodes of proluvial activation over the last 8500 years with the formation of an proluvial fan have been traced. This was followed by lacustrine sedimentation in a dammed lake, the relic of which is Khorlakel Lake. As a result, sedimentation in Khorlakel Lake and in the adjacent territories is clearly divided into two stages with a partition at ≈3 ka BP with the sedimentation of mainly nonorganic material at the first stage and organic material at the second stage. These stages include ten episodes, which are characterized by different sediments features and varying proportions of mineral and organic components. It was found that the initial lake during the Holocene decreased in size due to the uneven growth of the proluvial fan formed by sediments delivered from the catchment of Elbashi Creek. It has been established that some lithostratigraphic boundaries in the bottom sediments of Khorlakel Lake correlate with known strong earthquakes in the Elbrus region, while other boundaries relate to climatic events in the Central Caucasus that occurred during the Holocene. The complete termination of the connection between the current Khorlakel Lake and the Elbashi Creek catchment occurred in the last ≈1 ka BP. [ABSTRACT FROM AUTHOR]

Geochemical study of volcaniclastic material and radiocarbon dating of charred plant debris from Holocene deposits of the Guram site, which is located in vicinity of Vetrovoi Isthmus on Iturup Island, demonstrate that an explosive eruption (VEI 4-5) occurred there about 2000 years ago. The geochemical and age similarity with the tephra of marker layer CKr that was distinguished on Iturup, Urup, Simushir, Rasshua, and Matua islands of the Kuril Island Arc led to the conclusion that this eruption is possibly a source of this tephra. The data presented are proposed as a motivation for revision of the volcanic hazard on Iturup Island. [ABSTRACT FROM AUTHOR]

This article presents the generalization results of studying the long-term history of paleofires in the world and on the territory of Russia specifically. Perspective and reliable methods of reconstructing the local and regional dynamics of paleofires – micro- and macro-charcoal analyzes, are considered. In the article, we analyze approaches to the study of paleofires, methods of processing and identifying micro- and macroscopic charcoal particles, including the state-of-the-art software tools for their identification ("The Charcoal Quantification Tool", "WinSEEDLETM") and analysis ("CharAnalysis") based on a review of world and Russian scientific achievements. In addition, the possibilities of modern international paleofire databases (Global Charcoal Database, Reading Palaeofire Database), which contain up-to-date information on local and regional paleofire data in the Holocene, are considered here. The results of the study of paleofires globally and on the territory of Russia in particular are analyzed and possible research directions along with fire reconstruction issues are highlighted. The review of Russian publications has shown that the central and south parts of the East European Plain, as well as the southeast of Western Siberia, are the most studied regions in terms of reconstructing the dynamics of paleofires. Few similar studies were carried out in the Urals Mts., Eastern Siberia and the Far East, but most of the regions of Russia remain understudied in this regard. In recent years, Russian researchers are mainly focused on the study of local fire dynamics based on the use of macro-charcoal analysis. The analysis of international paleofire databases (Global Charcoal Database, Reading Palaeofire Database) shows that these data need to be radically revised in relation to key sites in Russia. The authors present a generalized scheme-map of Russia indicating the key areas where paleofire dynamics were reconstructed using micro- or macro-charcoal analyzes. [ABSTRACT FROM AUTHOR]

The impacts of climate change on the relationship between fluvial processes and dune landform evolution have been studied. However, the chronology data used to examine this relationship are deficient. The Keriya River has a glacial origin in the Kunlun Mountains on the south margin of the Tarim Basin. The river flows into the Taklimakan Desert, the second largest shifting-dune desert in the world. The dry channels and shifting dunes in this area provide an ideal opportunity to investigate fluvial and aeolian landform evolution processes and their relationship with climate change. We investigated this area during 2008–2011 and obtained 18 fluvial sediment samples from 16 sections for optically stimulated luminescence (OSL) dating. The results show that the ages ranged from 3.4–44.1 ka. Most of the samples (13) were Holocene in age, around 11 ka, 8–9 ka, 5–6.5 ka, 4.6 ka, and 3.4–3.7 ka and were distributed along ancient river channels around sites of Yuansha and Karadun. Two samples close to the Hotan River (38–47 ka) fall within the Marine Isotope Stage 3 (MIS3). Three samples (from one section) were located near ancient channels flowing towards the Yuansha Site and had ages of around 14.5 ka, i.e., during the Last Glacial Maximum (LGM). The analyses of the sediment samples and OSL ages suggest that the Keriya River flooded in the Holocene, the LGM, and MIS3. Fluvial sediments provided the source material for the dunes, and fluvial processes affected the landform evolution in the lower Keriya River. Our results suggest that most of the dunes covered in fluvial sediments in the lower reaches and the area west of the Keriya River developed since the Holocene. This differs from the results of previous studies, which suggested that they developed since the Han (202BC–220AD) and Tang (618–907AD) dynasties. The OSL ages of the fluvial sediments are consistent with the reported deglaciation (after glacial advance) ages in the alpine mountains surrounding the Tarim Basin. This suggests that climate fluctuations may have affected the occurrence of floods and the formation of dunes in the Taklimakan Desert. [ABSTRACT FROM AUTHOR]

The fossil record of the cave lion, Panthera spelaea, suggests a gradual decrease in body size, the process peaking just before the extinction of the species at the end of the Late Pleistocene. Such an evolutionary trend appears rather unusual for a large felid species and requires further investigation. This study reviews the cave lions of Ukraine, whose fossils are known from 46 localities dated from 800 kyr to 18–17 kyr ago, with a special emphasis on size changes through time. We describe several important finds including those of Panthera spelaea fossilis from Sambir, Panthera spelaea ssp. from Bilykh Stin Cave and Panthera spelaea spelaea from Kryshtaleva Cave. We make subspecific identifications of specimens from the region and focus on their size characteristics. Our analysis of Ukrainian cave lions agrees with the temporal trend of decreasing size, particularly accelerating during MIS 2, as exemplified by the extremely small female skull from Kryshtaleva Cave. We provide a direct AMS date for this specimen (22.0–21.5 cal kyr BP), which suggests that the Kryshtaleva lioness must have belonged to a Panthera spelaea spelaea population forced south by the spreading ice sheet. We discuss some palaeoecological aspects of the evolutionary history and eventual extinction of the cave lion. Finally, we review the subfossil records of the extant lion Panthera leo known from several Ukrainian sites archaeologically dated to 6.4–2.0 kyr BP. These finds most probably represent the Persian lion Panthera leo persica. [ABSTRACT FROM AUTHOR]

Changes in convective activity and hydroclimate over Northeastern Kalimantan are key features to understand glacial to interglacial climate evolution in the center of the West Pacific Warm Pool during the Late Pleistocene to Holocene. We use high-resolution X-ray fluorescence (XRF) scanner-derived elemental ratios in sediment Core SO217-18522 (1º 24.106' N, 119º 4.701'E, 975 m water depth) recovered from the northern Makassar Strait to reconstruct changes in precipitation-related weathering and erosion over Northeastern Kalimantan over the last 50 kyr. Enhanced seasonality of rainfall and an extended dry season during Heinrich Stadials (HS4 to HS1) and the Younger Dryas (YD) suggest weakening of the tropical convection associated with a southward shift of the tropical rain belt and the annual mean position of the Intertropical Tropical Convection Zone. Increasing sediment discharge and intensification of convective activity occurred during the early to mid-Holocene during an interval of high Northern Hemisphere insolation, elevated atmospheric pCO2 levels and global warming. Our reconstructions in comparison with regional terrestrial and marine records highlight the high spatial variability of Kalimantan hydroclimate on millennial to glacial-interglacial timescales. [ABSTRACT FROM AUTHOR]

The Holocene hydroclimate evolution and underlying mechanisms modulating the East Asian summer monsoon (EASM) remains controversial, especially in south eastern China. Here we present a multiproxy peat record of monsoon evolution from southeastern China covering the last 14 ka. Our new records show a relatively weaker EASM but wetter hydroclimate during the early (10 to 8 ka) and late Holocene (after 5.4 ka), while a stronger EASM and overall drier climate during the mid-Holocene (8 to 5.4 ka). In line with nearby speleothem records, our results reveal a dominant control of the northern-latitude ice-sheet meltwater forcing on millennial-scale East Asian hydroclimate variability during the last deglaciation and early Holocene. This dominant influence, however, likely waned once the global sea level had stabilized during the mid-to-late Holocene, giving way to other drivers of the monsoon and hydroclimate, including a combination of summer insolation and teleconnection patterns associated with vegetation-dust feedbacks. [ABSTRACT FROM AUTHOR]

Geophysical and geochemical methods were applied to detect the subsurface setting of an Upper Pleistocene-Holocene fluvial incised-valley where a travertine body intercalates between alluvial deposits of the Tiber river (central Italy), at Prima Porta (close to Rome). This study allowed us to provide more information regarding the local stratigraphic architecture and structural features, as a reference analogue to similar settings: i.e., hard (stiff) lithic travertines buried below fine and loose alluvial plain covers. Two Electrical Resistivity Tomography (ERT) profiles, interpreted and calibrated using previously collected litho-stratigraphic data from a borehole, identified a massive body, with a relatively high resistivity that correlates with the travertine deposit of Prima Porta. In addition to ERT, ambient noise measurements, processed with the HVSR technique and 2D array, and seismic refraction tomography were carried out; HVSR data were highly consistent with ERT results and allowed to discriminate between the travertine body and the silty-sand channels and overbank deposits, which were attributed to the Tiber river's evolution during Upper Pleistocene-Holocene. Finally, the presence of cracks/fractures could be inferred, as suggested by slight polarisation effects recorded in the HVSR results and soil-gas anomalies. [ABSTRACT FROM AUTHOR]

The paleoclimatic reconstruction of the last 14 ka was carried out by GPR sounding, spore–pollen analysis, and radiocarbon dating of a peat section (7 m) located in the model bog of Valdai National Park (Novgorod oblast). The peat accumulation rates varied from 0.075 mm/yr during the Late Glacial to 0.15–1.15 mm/yr during the Boreal stage (when the level of the Valdai lakes dropped by 10 m) and up to 4.25 mm/yr in recent centuries. Numerous cycles of the Holocene warming/cooling events were within ±1–2°C compared to the current ones and were accompanied by moderate fluctuations in annual precipitation (±25–50 mm). The forest composition changes were the most considerable during the Atlantic period, when spruce–broad-leaved forests and oak woods were predominant. Over the last two thousand years, the regional vegetation dynamics has mainly been influenced by agricultural activity. [ABSTRACT FROM AUTHOR]

The controversial issue of the primary origin of the oak groves of the Volga Uplands has been resolved based on our analysis of the spore–pollen complexes of the Holocene. The main stages of their formation have been reconstructed, namely: "tundra-steppe" with Artemisia–Chenopodioideae, horsetail, and fern cenoses (zone 10, 10 300–9300 years ago); grass–forb and Artemisia and Artemisia–Chenopodioideae steppes and steppificated greatly scattered birch woodland (zone 9, 9300–8500 years ago); grass–forb and sod-grass steppes and greatly scattered birch woodland (zone 8, 8500−8000 years ago); birch forests and grass-forb steppes, the emergence of the Volga upland oak forests (zone 7, 8000–6000 years ago); the formation and climax of oak groves (zones 6–4; 6000–2500 years ago); steppification and thinning of broadleaf forests and sod-grass steppes with the appreciable participation of weed and cultivated species, the emergence of the first agrocenoses (zone 3, 2500–700 years ago); and the emergence of the secondary undergrowth birch, oak, linden, and aspen forests); secondary meadow and sandy steppes with an abundance of weed species (ruderal, pascual, and segetal); the occurrence of secondary steppes in the place of forest clearance; expansion of agrocenoses (zone 2, 700–300 years ago); and reduction in the area of Volga upland oak groves and large-scale introduction of maple and, sporadically, pine (zone 1, 300 years ago–present). It has been concluded that the Volga upland oak groves are a native vegetation formation of the Volga Uplands, formed about 6000 years ago, long before the beginning of human economic activity. The modern appearance of this territory formed about 400–300 years ago, with the beginning of large-scale development in the area. [ABSTRACT FROM AUTHOR]

The Itapeva dunefield is an active aeolian transgressive dunefield system and an important conservation area (PEVA State Park) in Torres-RS, Brazil. It is cataloged as a geosite and contains geoforms of scientific value for studying the sedimentary environments and paleoclimates of southern Brazil. It stands out for its esthetic, cultural, and recreational value for the development of tourism. However, the use and occupation of its surroundings developed rapidly, and the environmental problems associated with these changes make it desirable to apply the principles of coastal management with geoconservation to the region. This study characterizes the geoforms and analyzes how they have changed over time, in addition to describing some of the challenges for the geoconservation of the area. A geomorphological analysis was performed in this study, focusing on the identification and characterization of aeolian landforms and landform units present in the Itapeva dunefield. Recent satellite imagery, field observations, and photographs were used to conduct this research. The results show that the main aeolian depositional units present in the Itapeva dunefield are reversing transverse dunes, U-shaped sub-parabolic dunes, precipitation ridges, nebkhas, deflation plains, vegetated transgressive sand sheets, and foredunes. Erosional features such as blowouts occur mainly in the foredune area and/or are associated with nebkhas/remnant knobs. Understanding the importance of geoconservation within coastal management can be an important step toward the preservation of the few sectors comprising dunefields in Brazil. To benefit the Park’s sustainable development, it is prudent to promote geodiversity, geoconservation, and geotourism, incorporating these principles into coastal management. [ABSTRACT FROM AUTHOR]

Micromammalian fauna and palynological spectra have been studied in two cave-type localities of the Iordanskogo Ravine in the Northern Urals (Pechora-Ilych Nature Reserve): the Studyony canopy and the Filin niche. The cave sedimentation conditions have been reconstructed on the basis of the paleofauna and palynological data. The fossil small mammal assemblages and the spore–pollen spectra are indicative of the spread of shrubby swampy tundra with forest islands in the Upper Pechora region at the end of the Middle Valdai (Byzovaya Interstadial, MIS 3) and tundra-steppe landscapes under the progressive climate drying during the Last Glacial Maximum. During the Late Glacial, tundra-like shrubs prevailed, and the climate was much colder than the recent one. The rodent fauna was dominated by tundra and tundra-steppe species. In the Early Holocene, the climate warming lowered the role of xerophytic shrubs, replaced by birch–spruce–pine forests. In the rodent fauna, the proportion of tundra and tundra-steppe species decreased by more than a factor of three. During the Late Holocene, dark coniferous forests with fir and Siberian pine became widespread. Rodent associations acquired a typical taiga appearance: the forest inhabitants accounted for more than half of all remains (60–80%), while the tundra species were absent. [ABSTRACT FROM AUTHOR]

The evolution of Holocene climate was investigated using grain size and magnetic susceptibility of the Holocene paleosols from Baicaoyuan (BCY), Xifeng (XF) and Linyou (LY) sections in the northwest, central and southern Chinese Loess Plateau (CLP). The results show that the Holocene in the BCY, XF and LY paleosol sections could be divided into three phases: during the early Holocene (11.8–10.5 kyr B. P.), increased magnetic susceptibility (χ) and frequency-dependent magnetic susceptibility (χfd) and decreased median grain size (Md) indicate that the East Asian Summer Monsoon (EASM) has become more intense and the climate has changed from cold to warm. During the middle Holocene (10.5–5.0 kyr B. P.), the values of χ, χfd and 2–5 µm grain-size fraction (GT2/5) are higher and Md and 30–63 µm grain-size fraction (GT30/63) are the lowest, which reflect a warm and humid regional climate. At ∼ 8.0 kyr B. P., there was a transient dry-cold climatic spike corresponding to a Heinrich Event, the cold event was likely due to the collapse of the Laurentide ice sheet. During the late Holocene (5.0–0 kyr B. P.), χ and χfd values are the lowest, while Md and GT30/63 are high, as proxies of a weakened EASM, when the dry-cold climate prevailed in the region. Decreased irradiance since 5.0 kyr B.P. may have caused climatic cooling and drying. Spatially, the increased main peak values and skewness from BCY, XF to LY sections show that the grain size became fine, the East Asian Winter Monsoon (EAWM) reduced, and climate was warmer and wetter from northwest to southeast. In addition, Md can be used as alternative proxy for EAWM, while χfd is positive with the intensity of EASM under semiarid climate conditions in CLP. [ABSTRACT FROM AUTHOR]

A 27.15-m-long core from Lake Chapala, west-central Mexico (1520 masl) possesses a continuous 15,000-year record of sediment accumulation with abundant diatoms, pollen, charcoal particles, and organic and inorganic carbon. Analyses of multiple sediment variables revealed the lake was deep, dominated by Stephanodiscus niagarae, and was surrounded by temperate forests of Pinus, Quercus, and Alnus in the late Pleistocene (14,700–12,760 cal yr BP). During the Pleistocene-Holocene transition (12,760–9660 cal yr BP), the lake level dropped and a temperate forest of Pinus and Quercus occupied the watershed and was persistently affected by fire. During the earliest Holocene, Quercus nearly disappeared and Pinus, relatively abundant, declined abruptly. Pollen of dry forests became more common, indicating the onset of drier conditions in the region. During the interval from 7500 to 6500 cal yr BP, more humid climate conditions prevailed and abundant Surirella spp. diatom valves were well preserved. Sediments of the time also contain Stephanodiscus niagarae and Ulnaria acus, suggesting deep-water conditions. Between 6500 and 2000 cal yr BP, the lake experienced higher conductivity and longer water residence times. The Pinus and Quercus forests began to be replaced by open vegetation, with Asteraceae and Poaceae dominating the pollen spectrum. Lake level fluctuated, but overall declined. Between the interval of ca. 2 ky to 0.5 cal yr BP basin conditions remained relatively wet. During the last ~ 0.5 kyr BP to present day, the lake level declined and ionic concentration increased, as inferred from representation of planktonic and benthic saline diatom taxa and TIC increases. Numerous micro-tephras are common in this interval; additionally, frequent fires favored the dominance of Poaceae. Paleolimnological records suggest that after the Last Glacial Maximum, Chapala and other lakes of west-central Mexico maintained relatively high water levels. Some records from the region showed evidence of increased humidity beginning ca. 8200 cal yr BP, a consequence of strength intensification in North American Monsoon, associated with ENSO variability and/or tropical cyclones. The record from the last 0.5 cal yr BP in Lake Chapala is similar to records from other lakes in Central Mexico, as it displays a trend toward drier conditions with a more variable precipitation regime. [ABSTRACT FROM AUTHOR]

Shell mounds, or middens, are artificial accumulations of food remains such as shells, sediments, artefacts and remains from daily life and funerary rituals, which were deposited in our study area by groups of Sambaquian fisher-hunter-gatherers. These mounds contain remains, which are representative of the fauna and flora at the time they were formed, enabling the recovery of palaeoenvironmental data related to biodiversity of taxa and biogeography, 14C dating and analysis of changes in the patterns of marine biodiversity and ocean circulation. This paper uses the Casa de Pedra shell mound rock shelter, located in São Francisco do Sul, state of Santa Catarina, southeastern Brazil, to study aspects of the palaeoenvironment through analyses of the archaeological material of the site, which contains well-preserved phytoliths and sponge spicules. Among the phytoliths, those from grasses predominate and some trees and palms were present, with no variation in vegetation type during the period of site occupation, between 5,470 and 4,460 years bp. Despite the general stability of the vegetation, a small increase in the density of the tree cover was identified from the base to the top, which may be related to an increase in precipitation, and is in agreement with other palaeoenvironmental studies carried out in southern Brazil. [ABSTRACT FROM AUTHOR]

The results of interdisciplinary research conducted at the Late Neolithic settlements Algai and Oroshaemoe (Aleksandrovo-Gaisky district of Saratov oblast, Lower Volga region) dated back to the 7th–5th millennia BC are considered. Modern soils of the study area are represented by light chestnut soils (Eutric Cambisols (Loamic, Protocalcic, Ochric)). In archaeological excavations, anthropogenically transformed variants of the same soils have been identified. Reconstruction of paleoenvironmental conditions in the area of archaeological settlements and their comparison with data from other parts of the Lower Volga region attests to periodic aridization and humidization of the climate and the related alternation of the stages of soil formation and sedimentation. An analysis of two neighboring sites indicates that the rate of soil formation in the study area varied from 0.8 to 35 cm/100 years. The soil strata have been identified and subdivided into several series of Holocene soils of different ages. Sterile (light-colored horizons without artifacts) or B horizons serve as parent materials for each of the formed soils. Sterile horizons were formed under arid climatic conditions with the development of salt-affected soils. The duration of the formation of each Holocene soil varied. Cyclic stages of aridization and humidization of the climate have been observed during the entire Holocene against the general background trend of increasing humidization. [ABSTRACT FROM AUTHOR]

Spore–pollen analysis of lacustrine and subaerial sediments of the KamPlen reference section in the Central Kamchatka Depression (CKD) is conducted. The results of the analysis allowed the reconstruction of the CKD landscape formation conditions in the Late Peni-Glacial, Late Glacial, and the transition to the Holocene, which significantly expands the paleogeographical record elaborated for the Holocene of Kamchatka into the past. It is established that, after 18 ka (under relatively cold climate), the watershed of the paleolake that filled the CKD during the last glaciation was characterized by open landscapes with dominant herbaceous–grass communities. The presence of pollen of trees and warm water plants indicates the limited scales of mountainous–valley glaciation. The identified cooling period of 15–13 ka characterized by scarcer vegetation did not lead to a significant expansion of glaciers. After 13 ka, warming of the climate with a gradual degradation of glaciers resulted in regeneration of coniferous forests on the paleolake watershed. The drainage of the lake at ~11.5 ka BP and the beginning of sedimentation of subaerial deposits in the area of the studied section approximately correspond to the lower boundary of the Holocene, which confirms the key role of the climate at stages of the CKD landscape formation during the period considered. [ABSTRACT FROM AUTHOR]

The gully system of the Sal and Don Rivers in the southeastern part of Rostov oblast was surveyed; the collected data indicate that Holocene deposits occupy a significant area and show high diversity. Accumulation of Holocene deposits in different areas was determined by local specifics, exogenous processes, landforms, parent rocks, and other factors. The following types of Holocene deposits were identified: (1) deposits on negative landforms (floodplain and first terrace above the floodplain) formed by alluvial, deluvial, and, to a certain extent, eolian processes; (2) deposits on the second terrace above the floodplain formed at the end of the Khvalynian stage of the Caspian Sea and during the new euxinic stage of the Black Sea; and (3) intermediate forms of Holocene deposits in minor depressions. The deposit accumulation history on negative and positive landforms is determined by the presence of contrasting stages reflecting changes in the external environment. The identified Holocene deposits of different ages turned out to be confined to archaeological artifacts indicating short-term habitats of nomadic cattle herders in various epochs. This makes it possible to identify and subsequently research "invisible" early human sites and obtain additional data on anthropogenic impacts on steppe resource areas in ancient times. [ABSTRACT FROM AUTHOR]

We review palaeoenvironmental proxies and combinations of these relevant for understanding hunter-gatherer niche construction activities in pre-agricultural Europe. Our approach consists of two steps: (1) identify the possible range of hunter-gatherer impacts on landscapes based on ethnographic studies; (2) evaluate proxies possibly reflecting these impacts for both the Eemian (Last Interglacial, Middle Palaeolithic) and the Early–Middle Holocene (Mesolithic). We found these paleoenvironmental proxies were not able to unequivocally establish clear-cut differences between specific anthropogenic, climatic and megafaunal impacts for either time period in this area. We discuss case studies for both periods and show that published evidence for Mesolithic manipulation of landscapes is based on the interpretation of comparable data as available for the Last Interglacial. If one applies the 'Mesolithic' interpretation schemes to the Neanderthal record, three common niche construction activities can be hypothesised: vegetation burning, plant manipulation and impact on animal species presence and abundance. Our review suggests that as strong a case can be made for a Neanderthal impact on landscapes as for anthropogenic landscape changes during the Mesolithic, even though the Neanderthal evidence comes from only one high-resolution site complex. Further research should include attempts (e.g. by means of modelling studies) to establish whether hunter-gatherer impact on landscapes played out at a local level only versus at a larger scale during both time periods, while we also need to obtain comparative data on the population sizes of Last Interglacial and Holocene hunter-gatherers, as these are usually inferred to have differed significantly. [ABSTRACT FROM AUTHOR]

The polyphasic evolution of the testimonial buttes in the central area of the Ebro basin (Los Monegros) is analysed. This is a semiarid area that favours high erosion rates. An evolutionary model of the Jubierre hills is presented that shows the environmental cycles represented by aggradational and degradative processes on the slopes that resulted in the present arrangement of talus flatiron rings. In the four studied cases, talus relicts are composed of detritic material from a disappeared caprock pediment. Four slope stages (S4 to S1) that formed under stable climate conditions are identified. Older stages (S4 and S3) are estimated by comparison with other talus flatirons in the region. The S2 stage contains Bronze Age archaeological remains and the radiocarbon age obtained was 1608–1446 years cal BC (2σ), while S1 is younger. A palaeoenvironmental interpretation was made for these aggradational stages (S4 to S1). The active erosion of these hills led to a relief inversion, and talus flatirons remain as the only features revealing the presence of the relict hills and past human occupations. [ABSTRACT FROM AUTHOR]

Data from a high-resolution sediment core off Goa in the eastern Arabian Sea (EAS) show that the Holocene surface-salinity variation off Goa contains four alternating high- and low-salinity events. These events are in contrast with the Bay-of-Bengal (BoB) surface-salinity variation after 5 ka BP, suggesting an asymmetry in the rainfall associated with the Indian summer monsoon over the eastern and western parts of the Indian subcontinent and its surrounding seas. This zonal asymmetry in rainfall is also seen in modern rainfall data. The historical rainfall over the Indian subcontinent indicates that the Northwest India and West Peninsular India and their rainfall subdivisions, which feed freshwater to the EAS, are mutually strongly correlated, but they are not correlated with Northeast India and North Central India and their subdivisions, which feed freshwater to the BoB. This mid-Holocene zonal asymmetry in rainfall over the eastern and western parts of the subcontinent appears to have sustained through to modern times. The Holocene salinity events off Goa are closely comparable to the evolution of Harappan Civilization in the Indus Valley, suggesting that the Holocene salinity variation in the EAS is connected to, and is a reliable indicator of, rainfall over the Harappan Civilization Region. Research Highlights: High-resolution core data off Goa show four alternating high- and low-salinity events during the Holocene. These events are coherent with the Bay of Bengal (BoB) surface-salinity variation till ~5 ka BP, but diverge thereafter. This zonal contrast between the eastern and western parts of the Indian subcontinent is also seen in modern rainfall data. This zonal asymmetry in rainfall may be associated with the northward propagation of rain bands and northwestward movement of low-pressure systems. The analysis favours a flood-forced decline of the Harappan Civilisation. [ABSTRACT FROM AUTHOR]

Cosmogenic radionuclide records (e.g., 10Be and 14C) contain information on past geomagnetic dipole moment and solar activity changes. Disentangling these signals is challenging, but can be achieved by using independent reconstructions of the geomagnetic dipole moment. Consequently, solar activity reconstructions are directly influenced by the dipole moment uncertainties. Alternatively, the known differences in the rates of change of these two processes can be utilized to separate the signals in the radionuclide data. Previously, frequency filters have been used to separate the effects of the two processes based on the assumption that millennial-scale variations in the radionuclide records are dominated by geomagnetic dipole moment variations, while decadal-to-centennial variations can be attributed to solar activity variations. However, the influences of the two processes likely overlap on centennial timescales and possibly millennial timescales as well, making a simple frequency cut problematic. Here, we present a new Bayesian model that utilizes the knowledge of solar and geomagnetic field variability to reconstruct both solar activity and geomagnetic dipole moment from the radionuclide data at the same time. This method allows for the possibility that solar activity and geomagnetic dipole moment exhibit variations on overlapping timescales. The model was tested and evaluated using synthetic data with realistic noise and then used to reconstruct solar activity and the geomagnetic dipole moment from the 14C production record over the last two millennia. The results agree with reconstructions based on independent geomagnetic field models and with solar activity inferred from the Group Sunspot number. Our Bayesian model also has the potential to be developed further by including additional confounding factors, such as climate influences on the radionuclide records. [ABSTRACT FROM AUTHOR]

This study describes time evolution of the Southern Annular Mode (SAM) in Mid- to Late Holocene simulated with a state-of-the-art transient simulation of the last 6000 years carried out with the IPSL-CM5A2 model. Simulated SAM index exhibits significant long-term linear trends of different sign depending on the season that are closely related to multi-millennial changes in insolation which was the main driver of long-term climate change in the study period. Interactions between changes in insolation and the SAM are linked to temperature and pressure changes developed through the entire Southern Hemisphere. In fact, model results suggest that insolation changes produced significant changes in extratropical temperature gradients that, in turn, induced changes in pressure gradients synthesized by significant long-term linear trends in the SAM index from Mid- to Late-Holocene. Considering that changes in the SAM index synthetize changes in hemispheric patterns of temperature, pressure and winds, results exposed in this study should be considered as reference for reconstructions of SAM evolution in the last 6000 years from climate proxy archives. [ABSTRACT FROM AUTHOR]

The origin of the loess deposits of the Cis-Caucasus Region, which form an almost continuous cover on the plains from the Sea of Azov to the Peri-Caspian Depression, is one of the controversial issues of paleogeography of the southern part of European Russia. The remarkably high thickness (up to 140 m) and extended coastal outcrops in the west and in the east of the region studied is of special interest to geologists and geographers who consider the loess strata as a unique record of climate conditions of the Quaternary period. The data on the structure, texture, and geochronology of the Upper Pleistocene and Holocene loess deposits, obtained from the study of 25 borehole logs and outcrop sections, distributed through the territory of the Cis-Caucasus region were received. The average sedimentation rates and the average sand fraction content were estimated for the stratigraphic units correlated with the global climatostratigraphic units (marine isotope stages (MIS)). It has been established that the source of the loess (wind erosion areas), are the valleys and estuary alluvial plains of large rivers: the Terek, Kuma, Volga, Kuban, and Don. The Peri-Caspian Depression was the dominant source of mineral dust throughout Late Pleistocene and Holocene. Large massifs of weakly fixed sands and sandy loams of the western Caspian region in combination with a high level of climate aridity and strong east winds created the prerequisites for the transport of huge volumes of mineral dust westward as far as the Sea of Azov. [ABSTRACT FROM AUTHOR]

The paleoclimatic events of the Late Pleistocene and Holocene have been clarified based on the results of detailed lithological, geochemical, pollen, and paleomagnetic studies of sediment cores collected in the eastern Gulf of Finland. The time frame of the change from lacustrine to marine sedimentation conditions has been refined based on the radiocarbon dating. For deposits of the marine phase of the Baltic Sea in the eastern Gulf of Finland, hypoxia cycles associated with periods of warming during the Holocene have been revealed. [ABSTRACT FROM AUTHOR]

Quaternary sediments of the Haji Arab River catchment located in Qazvin Plain, northwestern Iran, were studied in terms of sedimentology and geochemistry to determine the sedimentary environment and rock weathering. Discrimination diagrams show that the source rock of these sediments is granite and their tectonic setting is the active continental margin. These rocks show a negative Eu anomaly and a high ratio of light rare earth elements to heavy rare earth elements, suggesting that these sediments are originated due to the weathering of felsic rocks. Regarding the descending trend of chemical index of weathering, chemical index of alteration values, and the increase in coarse-grained particles, it was concluded that the sediments from the depth of 6 to 2.6 m formed under arid and high-energy conditions; however, this trend for sediments from 2.6 m depth to surface changes slightly toward semi-humid up to semiarid climate. Hence, it can be stated that the conditions of sedimentation environments in the Haji Arab basin are not constant at least in the Upper Holocene (Schmidt et al. in Holocene, 2011. https://doi.org/10.1177/0959683610385961) and this has led to changes in river sedimentation. These results indicate the changes in river regime conditions probably because of the changes in weather conditions during the Quaternary. [ABSTRACT FROM AUTHOR]

For almost a century there has been debate on the functional interpretation of desert kites. These archaeological structures have been interpreted as constructions for animal hunting or domestication purposes, sometimes for both, but with little conclusive evidence. Here, we present new evidence from a large-scale research programme. This unprecedented programme of archaeological excavations and geomatics explorations shows the unequivocal and probably exclusive function of kites as hunting traps. Considering their gigantic size, as well as the significant energy and organization required to build them, these types of traps are called mega-traps. Our research is based on five different field studies in Armenia, Jordan, Kazakhstan and Saudi Arabia, as well as on satellite imagery interpretation across the global distribution area of kites throughout the Middle East, the Caucasus and Central Asia. This hunting interpretation raises questions about the transformation of the landscape by human groups and the consequent anthropogenic impacts on local ecological equilibrium during different periods of the Holocene. Finally, the role of trapping in the hunting strategies of prehistoric, protohistoric and historic human groups is addressed. [ABSTRACT FROM AUTHOR]

Increasing evidence for the effects of Holocene history on modern biotic communities suggests that current explanations of community patterns and conservation strategies require revisiting. Here we focused on Central European rich fens that are at high risk among mire habitats because of their relatively low environmental stability, and hence sensitivity to successional shifts. At each of 57 study sites, inventory of specialist species of bryophytes, vascular plants and land snails, measurements of local environmental conditions, area, and radiocarbon dating were conducted. We used Moran's I spatial autocorrelation, multiple linear regression models, MDS, db-RDA, and null models to identify drivers of species richness and occurrence. We tested the importance of site age and historical metacommunity dynamics expressed by regional age of the habitat for the diversity of three taxonomic groups of fen organisms differing in dispersal and life history strategies. The richness of specialist species was affected by local environmental conditions and area in all three groups, but the effect of regional age was significant and positive for vascular plants and snails, once the effect of fen area was set as a covariable. We identified 11 species significantly associated with ancient fens independently of site area and pH effects; this group includes species currently considered to be umbrella species in European habitat conservation (the moss Hamatocaulis vernicosus and the snail Vertigo geyeri). The effect of fen age per se on the communities of specialists calls for the incorporation of age into conservation schemes. Restoration or de novo construction of peat-forming fens cannot compensate for a loss of ancient fens. [ABSTRACT FROM AUTHOR]

Lakes provide high-sensitivity and high-resolution documents and evidence, which are required for studying climatic changes and sedimentary environments at the global level. Furthermore, aeolian deposits in lacustrine environments, because of recording drought periods and dust storms, are valuable archives of paleoenvironmental conditions. In the present study, besides collecting the previous data, it was attempted to sample three intact sedimentary cores with the maximum depth of 7.3 m and total depth of above 20 m, from the sediments of the lakebed by auger. Sedimentary facies were separated based on their color, grain size; sedimentary composition, grain shape, and type of evaporate minerals. The existence of brown-colored coarse-grained pneumatic sand particles during the early to mid-Holocene period (8.2 ka BP) indicated the occurrence of intense storms in Sistan Basin. Sequence of the fine- and very fine-grained pneumatic sands at the depth of 2.5 m represented the presence of the winds similar to the current "120 day winds" in Sistan plain. Moreover, in this study, two major drought periods (8.2 and 4.5 ka BP) were identified in Holocene sediments of the lakebeds of Hamun-e-Helmand and Hamun-e-Sabari, which indicated drying and expansion of the aeolian sediments on Hamun's lakebed. [ABSTRACT FROM AUTHOR]

Lake sediments are important archives of past climate variability and lake responses to climate. In order to accurately infer past climates, it is necessary to understand, and account for, the ecological processes that affect the record of indicators preserved in lake sediment. This is particularly the case with respect to the concentration of carbon and nitrogen (TOC, TN, and calculated C:N), and the stable isotope composition of organic matter preserved in lake sediments. These are common, yet ambiguous, tracers of environmental change. Ideally, palaeoenvironmental reconstructions using the concentration and isotope composition of organic matter should be grounded in a detailed understanding of the sources of the organic material. This study documents the history and evolution of Blue Lake, an environmentally and culturally important oligotrophic, groundwater window lake on North Stradbroke Island, Queensland, Australia. We utilise organic matter δ13C, TOC, TN, and C:N from a 2.4 m sediment core with a basal age of 7.5 cal kyr BP, to investigate changing organic matter sources as a measure of the climate sensitivity of Blue Lake. This interpretation is supported by data from contemporary algae, aquatic and terrestrial plants, and catchment soils. We show that lake nutrient dynamics drove an increase in algal biomass at 4.2 cal kyr BP. This change coincides with a widely documented intensification of the El Niño-Southern Oscillation, which we infer to have influenced lake nutrient concentrations by reducing groundwater throughflow. Climatic changes resulted in marked changes in lake primary productivity, despite relatively little turnover of the lake diatom flora and catchment vegetation. This suggests that south-east Queensland dune lakes are sensitive to climate changes and helps to refine past and future palaeoclimate research using sediments from these lakes. It also indicates that increased nutrient concentrations in Blue Lake may result from projected changes in 21st Century climate. [ABSTRACT FROM AUTHOR]

A core of bottom sediments of 4.98 m depth has been taken from Lake Rubskoe, Ivanovo area (central part of the East European Plain). According to radiocarbon dating, the age of the lower layer of the core is 11 000 cal BP. A study of 23 samples has revealed the remains of 38 taxa of Cladocera (Crustacea: Branchiopoda). According to Lyubarsky's scale, there are no dominant taxa among the cladocerans; Chydorus cf. sphaericus (Müller, 1776) and Bosmina (Eubosmina) cf. longispina (Leydig, 1860) are subdominant taxa. Typical arctic species that had inhabited the lake at the earlier stages of its formation were replaced by taxa that preferred temperate conditions during the development of the water body. Four faunistic zones have been identified on the stratigrhaphic diagram of the cladoceran community of Lake Rubskoe. An increase in the proportion of Bosmina (Eubosmina) cf. longispina in the layers of 8500 cal BP may have been related to an increase of the pelagic area of the water body at that period. In many cases, it is obvious that the rates of certain taxa in the taphocoenosis of Lake Rubskoe correlate with the climatic changes reported at that time. [ABSTRACT FROM AUTHOR]

Stand-scale gap-phase dynamics is generally viewed as the main driver of development in mesic deciduous forests of the temperate biome. Soil charcoal of temperate forests in eastern North America are unnoticed in most surveys, thus explaining why fire is undervalued as a driver of forest succession. The extent to which gap-phase, fire, or other processes are responsible for the regeneration and maintenance of mesic deciduous forests is unknown because paleoecological evidence is lacking. We tested the fire-driven succession hypothesis on the development of this major forest type. Based on charcoal 14C dates of two sites, 44 and 55 fires occurred since early Holocene, with a mean interval of 170 to 215 years. The vegetation of both sites followed comparable post-glacial trajectories consisting of three distinct periods. Conifers dominated the two first periods during 5200–6000 years and were replaced by hardwoods–conifers over the last 3500 years. The first period was represented by boreal conifers, whereas the second period, dominated by white pine (Pinus strobus) forests, persisted during 3000–4300 years. The third period marked the development of hardwood (sugar maple, Acer saccharum) forests. Fires occurred continuously on the sites since early Holocene likely under dry conditions during the conifer periods and cooler and moister conditions during the hardwood–conifer period. Recurrent fires appear with climate as key drivers of the long-term dynamics of several temperate forests in eastern North America. Similar studies on other temperate forests should be pursued to test the hypothesis of climate–fire interactions influencing tree composition change. [ABSTRACT FROM AUTHOR]

Ruins of archaeological structures, mainly dating to the Bronze Age till Byzantine period, were investigated in a case study in the Petra region in southern Jordan and in the northern Negev desert in Israel. They are covered by post-abandonment debris sediments which provided the parent material of initial soils now developed on the ruins. Such debris sediments have so far rarely been studied although they likely contain a significant aeolian dust fraction because structures and wall remains may act as effective dust traps. We analyzed different types of archaeological structures: cult sites on hilltops, runoff-irrigated terraces on slopes, and cisterns including associated cleanout mounds. As well, we collected current aeolian sediments in nearby dry marble dust traps. It was expected that the various ruins and location types would matter for sediment properties, but substrate composition in all investigated structures was similar. This suggests that most of the fine fractions of the debris material were primarily supplied by wind whereas fluvial processes only re-distributed aeolian sediments. A major aeolian contribution from local weathered rocks could be observed in the Petra region, but not in the Negev, which seems connected with the geology. In situ pedogenesis in both investigation regions is negligible. The ruins seem to act as current dust collectors, but their sediments cannot directly be compared with the material collected in nearby dry marble dust traps. Analogies to different types of collectors for aeolian sediments can be made: depending on design, dust traps gather aeolian material differently. Standard dry marble dust collectors are characterized by similar size of settling dust samples as compared to average aeolian deposition in the ruins, but are of dissimilar substrate composition with regard to particle size distribution and contents of major and trace elements. Sediments in the archaeological structures in southern Jordan show finer textures and higher contents of most major and trace elements which may indicate preferential fixation of silt and clay against sand in the ruins, whereas sediments in dry marble dust collectors in Jordan are relatively depleted in silt and clay. This could be due to crusts and clast covers because the studied archaeological hilltop structures were found covered by surface crusts and pavements of stones and pottery sherds. These may mirror the effect of desert pavements. In addition, current dust samples suggest that precipitation during aeolian sedimentation, in particular in case of snow, is connected with enhanced deposition of (possibly clay-coated) silt. Sediments in the archaeological structures include material from remote and local sources as well as from "recycled" paleosols. Average hilltop dust accretion rates were calculated as ~ 0.14 mm/year, which is in good agreement with results from dry marble dust collectors. They exceed rates calculated for Pleistocene hilltop loess in the Negev. This seems due to enhanced dust fixation in the archaeological ruins as compared to natural Negev loess soils, underlining a so far rarely considered but important role of sediment fixation mechanisms. [ABSTRACT FROM AUTHOR]

Lake level and its inferred East Asian summer monsoon (EASM) evolution in northern boundary of EASM during the Holocene are highly debated. Here, we present a 15-ka record of glycerol dialkyl glycerol tetraethers (GDGTs) in a closed lake in northern China to address this issue. Surface and downcore sediment data demonstrate sedimentary GDGT-0 and branched GDGTs (brGDGTs) are of aquatic production. Contents of GDGT-0 and brGDGTs increase but brGDGT-based paleo-temperature proxy decreases with water depth in surface sediments along a nearshore to offshore transect. This trend is likely due to an increasingly hypoxic condition, favored by anaerobic microbes producing these GDGT-0 and brGDGTs, in bottom water. Accordingly, brGDGT-derived water temperature and pH would reflect bottom water conditions that are largely regulated by water depth of the lake. Downcore GDGT data and their derived temperature and pH consistently reveal a gradually increasing lake level from the late Pleistocene to the early Holocene, a high level during 9.5–5 ka BP and a decreasing trend afterward. The lake-level records from independent and robust proxies in this study largely agree with pollen records in the region, supporting a mid-Holocene maximum EASM precipitation. [ABSTRACT FROM AUTHOR]

The characterization of organic matter (OM) composition, physico-chemical, geochemical, and mineralogical studies of sedimentary core can help to better understand the paleoclimates and the depositional environments. The purpose of this work is to identify the factors monitoring the mineralogical composition and the sedimentation of sebkha Mhabeul sediments (southeastern Tunisia), during the Holocene. A 100.5 cm core (Mh 1) collected from this sebkha was analyzed for the determination of chemical composition by X-ray fluorescence (XRF), carbonate content by Bernard calcimetry, grain-sized sediments by AFNOR sieves, OM content by Rock-Eval 6 Pyrolysis, and mineralogical composition by X-ray diffraction (XRD), scanning electronic microscope (SEM), and infrared spectroscopy (IR). The sedimentary fillings of this sebkha, constituted by fine fractions, are characterized by the dominance of the detrital minerals (72–96 %) with high quartz percentages (42.2–91.5 %). The mineralogical composition of the studied sediments included detrital minerals (clay minerals, quartz, and feldspars), carbonate minerals (ankerite, dolomite, and calcite), and evaporitic minerals (halite, bassanite). The clay minerals (11–14%) are composed of a mixture of kaolinite, illite and palygorskite. Fourier transform infrared (FTIR) absorption spectra of all sediment samples confirm the mineralogical composition obtained by XRD and the existence of OM, by defining the band assignments for OM and different minerals as quartz, feldspar, clay, and carbonate minerals. The Rock Eval pyrolysis shows that the OM is immature and has a mixed origin (terrestrial and aquatic). The statistical analyses prove the results of geochemical and mineralogical studies. Indeed, the principal component analysis (PCA) of geochemical and mineralogical data and the depth help to prove the relationships between minerals and chemical elements. Moreover, the negative correlation between the Rock Eval Pyrolysis parameters and the depth shows a homogenous statistical group. [ABSTRACT FROM AUTHOR]

This study explores the paleoenvironmental changes of the Acholla coast over the last 2000 years by means of subsurface sediment analyses of lagoonal deposits via a multiproxy approach. A sequence of 5 steps is shown to have shaped the coastal development at Acholla and includes (i) the settlement of an open marine embayment during the Upper Pleistocene (substage 5e) in response to a transgressive event as evidenced by the deposition of carbonate sandstones rich in mollusc associations and marine elemental ratios Sr/Al, Ca/Al, Cl/Al, and S/Al; (ii) a sea-level rise towards183 AD, after a long period of emergence of the coast, leading to transgressive deposits of poorly sorted fine sands that are rich in diversified mollusc and ostracod taxa; (iii) a high-energy event (towards 417AD) with a peculiar biofacies characterized by coarse bioclastic mollusc-rich sands, charcoal particles, Tyrrhenian lithoclasts, and high values of marine elemental ratios Cl/Al, S/Al, and Ca/Al; (iv) a progradation of coastal habitats (between 417 and 1577 AD), favored by a period of flooding/detrital input and longshore current drifts, resulting in the development of an extensive sandspit and the formation of the Acholla lagoon. The construction of a Roman pier, originally constructed to protect the Acholla harbor from sedimentation, was counterproductive and favored the expansion of coastal swash bars and extension of the sandspit, ultimately resulting in the abandonment of the Acholla harbor; (v) the closure of the lagoon (from 1577 AD onward) and the built-up of well-sorted silt deposits are marked by the decrease of detrital elemental ratios (Ti/Al, Si/Al, and K/Al) and by reduced ostracod species richness values. The inferred scenario for the evolution at Acholla coast matches those for Sfax and Skhira coast in the Gulf of Gabes (Tunisia). Unlike Sfax and Skhira, however, the Acholla coast has been subjected to uplift by active faults, resulting in a time shift of depositional patterns. [ABSTRACT FROM AUTHOR]