Late Pleistocene to Holocene vegetation dynamics in northern Kamchatka (northeastern Russia) inferred from pollen records

Late Quaternary water depth changes in Hala Lake, northeastern Tibetan Plateau, derived from ostracod assemblages and sediment properties in multiple sediment records

The short communication article presents the results of analyses of the lacustrine sediments of Novozhilovo and Chelvinskoe lakes, located at the Kama-Vychegda watershed. Big set (209) of sediments samples from three wells were analyzed by the loss on ignition (550 °C) method. Age of cores and the rate of sediment accumulation were based on the 14 radiocarbon dates. Six stages of deposits accumulation and nature dynamics during the Late Glacial and Holocene in the lakes catchment area are proposed. The first stage (14.15 – 13.5 cal. kyr BP) is characterized by high rates of deposits accumulation at low values of organic matter content, indicating alluvial sedimentogenesis. Peak of accumulation rates as well as a sharp rise in bioaccumulation were observed during the second stage (13.5 – 12.4 cal. kyr BP), which is interpreted as stabilization of the lake level and external environmental conditions. During the third stage (12.4 – 10.7 cal. kyr BP), the sediment accumulation rate decreases rapidly, reaching a minimum by the end of the period. The organic matter content also decreases significantly (to 30 %). The short-term fourth period (10.7 – 10.0 cal. kyr BP) records the transition from the Late Pleistocene (dominance of rarefied periglacial vegetation) to the Early Holocene (predominance of forest communities). This is marked by a drastic increase in the loss on ignition values (up to 92-95%). During the fifth stage (10.0 – 8.8 cal. kyr BP), the sediments accumulation rate increases and the organic matter content decreases to 77-82%. Synchronously with some increase in the concentration of mineral particles. Smoothing of the loss on ignition curve (average values - 92-96%), a marked increase in the sediment accumulation rate during the sixth stage (8.8 - 5.0 cal. kyr BP) probably indicates the stabilisation of external conditions in the lake catchment.

The palaeoenvironment of the Karelian Isthmus area during the Litorina Sea stage of the Baltic Sea history, between 8.0 and 4.5 kyr BP (8.8‐5.2 cal. kyr BP), was reconstructed by studying four sites located on the Karelian Isthmus in Russia. Methods included diatom and pollen analyses, sediment lithostratigraphical interpretation and 14C dating. The brackish‐water (Litorina) transgression began c. 7.7 kyr BP (8.45 cal. kyr BP) in the Karelian Isthmus area. The transgression maximum occurred between 6.7 and 5.7 kyr BP (7.6‐6.5 cal. kyr BP), depending on the glacio‐isostatic land uplift rate. Regarding the vegetation, the maximum occurrence of temperate deciduous trees took place at the same time. The transgression was interrupted by a short‐lived sea‐level standstill during the middle phase of the main transgression, c. 6.3 kyr BP (7.2 cal. kyr BP), on the eastern part of the isthmus. The highest Litorina shoreline is located between 8 and 13 m above present sea‐level and the amplitude of the Litorina transgression has varied between 5 and 7 m. The 8.2‐kyr cold event is not evident, but the sea‐level standstill around 6.3 kyr BP (7.2 cal. kyr BP) could reflect a cool episode at that time in the Karelian Isthmus area.

Holocene climate and civilization

Millennial-scale vegetation and climatic changes from an Early to Mid-Holocene lacustrine archive in Central Ganga Plains using multiple biotic proxies

<p>Environmental conditions along the Algerian margin (AM) involve complex atmosphere-hydrosphere-biosphere interactions with superimposed anthropogenic activities on adjacent watersheds across the Holocene. Surface waters of the Atlantic Ocean entering the western Mediterranean Sea become the Algerian Current (AC) flowing along the North African coast and generating anticyclonic eddies. Upwelled waters are other recurring hydrological feature reflecting the instability of the AC. In this area, Holocene vegetation and paleohydrological dynamics have not yet been described. The marine core MD04-2801 (2,067 m water depth) has been analyzed to assess environmental and climatic conditions over the last 14 kyrs BP at a secular-scale resolution to fill this gap. A multi-proxy approach including terrestrial (pollen grains and continental non-pollen palynomorphs such as Glomus spores and freshwater microalgae) and marine (dinoflagellate cysts or dinocysts) palynological data as well as sedimentological data (grain-size analysis and clay mineral assemblages) and biomarkers (alkenones and n-alkanes) have been used to investigate the links between past sea surface hydrological conditions characterized by the over-representation of heterotrophic dinocyst taxa (especially <em>Brigantedinium</em> spp.) and regional environmental changes on nearby watersheds. Quantifications of hydrological and climate parameters are also estimated using the Modern Analogue Technique applied to dinocyst and pollen assemblages. Our data evidence linkages between continental dryness or moisture and surface ocean conditions. High productivity is recorded during the cold and arid climate conditions of the Younger Dryas (12.7 to 11.7 ka BP). During the Early-Middle Holocene (11.7 to 8.2 and 8.2 to 4.2 ka BP), fluvial discharges increase concomitantly with the colonization of coastlands by the Mediterranean forest and oligotrophic conditions in the AM. In contrast, aridification characterizes the Late Holocene with the notable 4.2 ka BP megadrought  between 4.3 and 3.9 ka BP. Comparison between with other paleoenvironmental records from the Gulf of Cadiz to the Siculo-Tunisian strait underlines a west to east climatic gradient at orbital and infra-orbital timescales, with marked cold-dry events at 9, 8.1, 7.3 and 6.5 ka BP. This zonal gradient is discussed to explain contradictory results from the Alboran Sea to Tunisia. Finally, the last 3 kyrs BP highlight the establishment of modern ocean production conditions reflecting both vertical mixing in the AM (wind-driven eddies of the AC) and nutrient-enriched fluvial discharges intensified by human land-use.</p>

Holocene environments and climate in the Mongolian Altai reconstructed from the Hoton-Nur pollen and diatom records: a step towards better understanding climate dynamics in Central Asia

Pollen-inferred precipitation time-series from equatorial mountains, Africa, the last 40 kyr BP

Last glacial–interglacial vegetation and environmental dynamics in southern Siberia: Chronology, forcing and feedbacks

Landscape evolution, post-LGM surface denudation and soil weathering processes from Dickinson Park mire, Wind River Range, Wyoming (USA)

This work analyzes the results of the SP2 core (50.30 m length) collected in the coastal plain of Sepetiba Bay (SB; SE Brazil), 2 km away from the Guandu River mouth (latitude 22° 55′S, longitude 43° 46′W). It aims to study the influence of the Holocene relative sea level (RSL) on the coastal plain of SB. After description, the SP2 core was sampled at every 5 cm for grain size, geochemical, mineralogical and foraminiferal analyses. Four radiocarbon dates obtained in the first 18 m were modulated with Bayesian statistics. The SP2 core is composed of basement rocks, gneisses (50.30–43.80 m); river sediments (43.80–21.00 m) up to about ≈ 5.0 kyr BP; a sediment package marked by sudden textural and compositional changes, accumulated between ≈ 5.0 and 4.7 kyr BP; muddy sediments deposited between 4.7 and 0.8 kyr BP (18.80–3.35 m) with intercalations of sandy levels; an upper part of disturbed embankment sediments used for the implantation of Santa Cruz Thermoelectric Power Plant. The fluvial sands accumulated before ≈ 5.0 kyr BP were deposited before the maximum Mid-Holocene relative sea level. They were probably eroded and transported by the drainage network of the N region of SB, namely by the Guandu River. Between ≈ 4.5 and 3.5 kyr BP, the foraminiferal abundance and assemblage composition indicate that the study site was a shallow marine environment, due to the Mid-Holocene relative sea-level highstands (MHSLH). Between ≈ 3.5 and 3.0 kyr BP, the sediment accumulation rate (SAR) was the lowest of the last ≈ 5 kyr BP and the study site was exposed to subaerial weathering processes, in a scenario of the relative sea-level drop. A new phase of marine influence was recorded between ≈ 3.0 and 1.9 kyr BP, associated with the highest SAR of this record, up to ≈ 27.4 m/kyr BP. Between ≈ 1.9 and 1.8 kyr BP, the study site was under subaerial weathering processes. Since then the SAR reduced significantly to a mean value of ≈ 4.5 m/kyr and, between ≈ 1.8 and 0.8 kyr BP, the study site was again under the marine influence. Foraminifera were not found, after ≈ 0.8 kyr BP, in the SP2 core. However, the occurrence of a shallow marine environment was identified in another core, between ≈ 1.4 and 0.35 kyr BP, in the Guaratiba Mangrove, NE of SB. The results of the SP2 core suggest that MHSLH left a striking record in the study area, although some of the identified environmental changes are probably related to adjustments of the lower course of Guandu River and tidal channels and variations in the configuration of sandy littoral strands. The growth of a barrier–island system, the Marambaia barrier island, since the last ≈ 8–7.5 kyr BP may also have induced changes in the study area.

The structure, composition and cut and fill sequence of the Late Glacial and Holocene erosional landforms in the Kuitunka River basin on the right bank of the Selenga River were studied based on a detailed analysis and radiocarbon dating of the soil-sedimentary sequence in the Studenyi Klyuch 2 and Kovalev Pad’ sections. A correlation was carried out between seven sections in the intermittent stream valleys in the Kuitunka River basin. There are three episodes of the Late Glacial and Holocene cutting dated back to ~18–17, ~14.7–14.3, and 0.25–0 cal. kyr BP (ka BP). There are distinguished the periods of colluvial, colluvial-deluvial and aeolian-deluvial sediment deposition in the intermittent stream valleys (17.0–14.7 ka BP) and predominantly aeolian-deluvial loess-like sediment accumulation involving pedogenetic stages (14.30–0.25 ka BP). The climatic warming and humidification led to a decrease in sedimentation rate, prevalence of loessification processes in formation of loess-like deposits, and formation of organic–accumulative soil horizons of different thicknesses. The Late Glacial warming, comparable to the Bølling – Allerød Interstadial (14.3–12.9 ka BP) and the Holocene (11.7–0 ka BP), is characterized by a dynamic change in the stages of loess-like deposit accumulation and pedogenesis. The Younger Dryas cooling (12.9–11.7 ka BP) is associated with the activation of aeolian and cryogenic processes and a short phase of pedogenesis. It was revealed that the most frequent changes in sedimentary phases and soil formation occurred during the Late Glacial Interstadial and the Early (11.7–8.2 ka BP) Holocene. The Middle Holocene (8.2–4.2 ka BP) is characterized by a decrease in the rate of accumulation of intermittent-stream valley loess-like bottom deposits and a long-term (several ka) active pedogenetic process. The cross-sections of the Late Holocene (last 4.2 ka BP) draws and valley-bottom gullies exhibit the stages of pedogenesis (4.2–1.0 ka BP), activation of erosion–accumulation processes (1.00–0.25 ka), gullying, accelerated erosion, and accumulation (last 0.25 ka BP).

To understand the early- to mid-Holocene vegetation and climate dynamics on the eastern coast of the Yellow Sea, we obtained a sedimentary core with high-resolution accelerator mass spectrometry (AMS) carbon 14 (14C) data from the Gunsan coast in South Korea. The palynological analysis demonstrated that the riverine wetland meadow from 12.1 to 9.8 cal. kyr BP changed to temperate deciduous broad-leaved forest in 9.8–2.8 cal. kyr BP. In addition, the cold climate from 12.1 to 9.8 cal. kyr BP became warmer from 8.5 to 7.3 cal. kyr BP. This was followed by another relatively cold period from 7.3 to 2.8 cal. kyr BP. The temperature change was mainly in response to solar factors. However, there are two relatively humid periods from 12.1 to 9.8 and 8.5 to 7.3 cal. kyr BP, which arose for different reasons. The earlier humid period resulted from strong westerlies and a rapidly rising sea level. The later humid period was produced mainly by the strong East Asian summer monsoon (EASM) and may also be linked to La Niña–like activity. The cold ‘Younger Dryas’ event from 12.0 to 11.4 cal. kyr BP recorded in this study may have been produced by a North Atlantic meltwater pulse. This would have reduced temperatures that were already low because of weak insolation, and the strong winter monsoons would have increased the precipitation.

The Cueva Mayor karst system of Atapuerca, in Northern Spain, hosts a highly significant record of human occupation from the Pleistocene. The climatic context of the human activities during the Pleistocene-Holocene for this inland site has not been well constrained, since existing records of the palaeoclimatic evolution of the Northern Iberian Peninsula are from more distal coastal and high-elevation sites. In this study, we interpret the palaeoenvironmental information recorded on the petrography of a stalagmite and the pollen spectra of the Sierra de Atapuerca karst system during the last 20 kyr. The integration of both types of records has allowed us to define four palaeoenvironmental stages. During the Upper Pleistocene and until 12.8 kyr BP, the climate was cold and dry, toward the end of the interval evolving to wetter and warmer conditions. From 12.8 to 7.7 kyr BP, during the Mesolithic-Neolithic, a major erosion event in both records marks the Pleistocene-Holocene transition. Around 5.9 kyr BP, the Late Neolithic, environmental conditions indicate a climatic optimum with a marked seasonality. The environmental conditions became drier from 4.2 kyr BP until the present, with a decrease in the woodlands. This aridity signal might be amplified by the impact of a more intense human agricultural activity after 3.1 kyr BP, during the Bronze Age.

Late Pleistocene and/or Holocene high-resolution palynological studies are available for the south basin of the Caspian Sea (CS), the world's largest lake. However, the north and middle basins have not been the object of high-resolution palynological reconstructions. This new study presents the pollen, spores and dinoflagellate cysts records obtained from a 10 m-long sediment core recovered in the middle basin, which currently has brackish waters and is surrounded by arid and semi-arid vegetation.An age–depth model built based on six radiocarbon dates on ostracod shells indicates that the sequence spans the period from 14.47 to 2.43 cal. ka BP. The present palaeoenvironmental study focuses on the top 666 cm, or from 12.44 to 2.43 cal. ka BP.At the vegetation level, the Younger Dryas is characterised by an open landscape dominated by desert vegetation composed by Amaranthaceae with shrubs and salt-tolerant plants. However, although the Early Holocene is also characterised by desert vegetation, it is enriched in various shrubs such as Ephedra and Calligonum, but tree expansion is not important at the Holocene onset. After a major shift at 8.19 cal. ka BP, the Middle Holocene displays now both the character of desert and of steppe, although some trees such as Quercus and Corylus slightly spread. The Late Holocene records steppe vegetation as dominant, with more tree diversity.Regarding the lacustrine signal, the dinocyst assemblage record fluctuates between slightly brackish conditions highlighted by Pyxidinopsis psilata and Spiniferites cruciformis, and more brackish ones – similar to the present day – with the dominance of Impagidinium caspienense. The Late Pleistocene is characterised by low salinities, related to the Khvalynian highstand. From 11.56 cal. ka BP, slightly more saline waters are reconstructed with an increase of I. caspienense for a period of 1000 years, which could be attributed to the Mangyshlak lowstand. From 10.55 cal. ka BP, low salinity conditions return with remains such as Anabaena and Botryococcus abundant until 8.83 cal. ka BP, followed by a slow, progressive decrease of P. psilata and S. cruciformis until 4.11 cal. ka BP, which is the main assemblage change at lacustrine scale. Since then, higher salinities, similar to the present one, are reconstructed. Finally, Lingulodinium machaerophorum starts its development only at 2.75 cal. ka BP, in the Late Holocene.The present research revealed fundamental differences from previously published sea-level curves, in that a 6000 yr-long highstand suggested by low salinities is shown between 10.55 and 4.11 cal. ka BP. Amongst other arguments, using a comparison to a similar palynological regard but in the south basin, a N–S salinity gradient that is the reverse of the present one across the CS, suggests that the Amu Darya was flowing in the CS. Hence the CS levels during the Late Pleistocene and Holocene were influenced by a combination of precipitation over the high European latitudes and the indirect influence of the Indian summer monsoon over the Pamirs.