41 results
Search Results
2. The Holocene of Sweden – a review.
- Author
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Wastegård, Stefan
- Subjects
HOLOCENE Epoch ,LITTLE Ice Age ,PLEISTOCENE-Holocene boundary ,CLIMATE research ,TRANSFER functions - Abstract
This paper presents a review on more than hundred years of palaeoenvironmental research in Sweden; from early descriptions of peat and tufa deposits in the late nineteenth and early twentieth centuries to multiproxy transfer function studies in the late twentieth and early twenty-first centuries CE. Research on Holocene climate variability has a long history in Sweden and many ideas and concepts about changes in temperature and precipitation during the Holocene originated in Fennoscandia. The Holocene climate evolution in Sweden follows a pattern in common for many northern latitude records with a rapid warming starting at the Pleistocene–Holocene boundary at c. 11 650 cal a BP, followed by the middle Holocene thermal maximum between c. 8000 and 5000 cal a BP. A change to colder and wetter conditions starts c. 4000 cal a BP and lasts until the late 1800 s CE. There is evidence for climatic anomalies such as the 8.2 and 4.2 ka BP events and the Little Ice Age (LIA) but only inconclusive evidence for other events, such as the 10.3 ka BP event. The main pattern of Holocene climate and environmental evolution is well known for most parts of Sweden, but the present review also shows that several research questions remain to be addressed. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
3. Environment and settlement - A multiproxy record of holocene palaeoenvironmental development from Lake Wonieść, Greater Poland
- Author
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Dörfler, Walter, Feeser, Ingo, Hildebrandt-Radke, Iwona, and Rzodkiewicz, Monika
- Published
- 2023
- Full Text
- View/download PDF
4. A multi-proxy lake-sediment record of middle through late Holocene hydroclimate change in southern British Columbia, Canada
- Author
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Shea, Christopher J., Steinman, Byron A., Brown, Erik T., and Schreiner, Kathryn M.
- Published
- 2022
- Full Text
- View/download PDF
5. Environmental change inferred from Rb and Sr of lacustrine sediments in Huangqihai Lake, Inner Mongolia.
- Author
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Chen, Lei, Shen, Hongyuan, Jia, Yulian, Wu, Jinglu, Li, Xusheng, Wei, Ling, and Wang, Pengling
- Abstract
Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986, the paper investigates the record of palaeolake stand state, sedimentary environmental evolution, and winter monsoon change. First, these samples are separated into three different grain size fractions, i.e., total sediments, 77-20 μm and <20 μm. Second, the chemical elements—Rb and Sr—of the grain size separation were tested and analyzed systematically in this paper. Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument, respectively. The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company. The results showed the elements and the ratios varied regularly with the grain size. But the ratio of Rb/Sr in the sediments <20 μm correlates positively with the magnetic susceptibility of these samples. Therefore, the ratio of Rb/Sr in the fraction <20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites. It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoenvironment. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
6. Analysis of relationship between soil erosion and lake deposition during the Holocene in Xingyun Lake, southwestern China.
- Author
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Zhao, Hongfei, Zhou, Jie, Sun, Qianli, Delang, Claudio O, Mokhtar, Ali, Ma, Yue, and He, Hongming
- Subjects
- *
SOIL erosion , *HOLOCENE Epoch , *EFFECT of human beings on climate change , *LAKE restoration , *WATERSHEDS - Abstract
Quantifying the relative influences of anthropogenic activities and climate change on soil erosion and deposition during the Holocene, when both forces have been interacting is a complex problem. Analysis of long-term patterns in soil erosion and lake deposition in a basin can provide the basis for untangling the complexities of climate and anthropogenic forcings. In this paper, sedimentary sequences from Xingyun Lake are compared with simulated soil erosion rates in the basin to explore the relationship between river basin soil erosion and lake deposition during the Holocene in Yunnan, China. Modern soil erosion rates are calculated using RUSLE, while Holocene soil erosion rates are estimated using modern rates with reconstructed precipitation and vegetation cover sequences. Through this investigation, we found the following results. First, Holocene vegetation in the lake basin was mainly affected by climate change, and the vegetation experienced the same pattern of changes as the climate. Soil erosion and lake deposition rates, along with changes to vegetation cover, were synchronous with precipitation trends during the Holocene. Second, soil erosion and lake deposition have been exacerbated by human activities, such as deforestation and land reclamation in the Xingyun Lake basin. Finally, this study provides new insights into the effects by anthropogenic impacts and climate forcing on the processes of soil erosion and lake deposition on the millennium scale. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
7. Human-environment interaction during the Holocene along the shoreline of the Ancient Lake Ladoga: A case study based on palaeoecological and archaeological material from the Karelian Isthmus, Russia.
- Author
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T, Alenius, D, Gerasimov, T, Sapelko, A, Ludikova, D, Kuznetsov, A, Golyeva, and K, Nordqvist
- Subjects
- *
HOLOCENE Epoch , *SHORELINES , *LAKE sediment analysis , *STONE Age , *WATER levels - Abstract
This paper presents the results of pollen, diatom, charcoal, and sediment analyses from Lake Bol'shoye Zavetnoye, situated between the Gulf of Finland and Lake Ladoga on the Karelian Isthmus, north-western Russia. The main goal is to contribute to the discussion of Neolithic land use in north-eastern Europe. The article aims to answer questions related to Stone Age hunter-gatherer economy, ecology, and anthropogenic environmental impact through a comprehensive combination of multiple types of palaeoecological data and archaeological material. According to diatom data, Lake Bol'shoye Zavetnoye was influenced by the water level oscillations of Ancient Lake Ladoga during much of the Holocene. Intensified human activity and prolonged human occupation become visible in the Lake Bol'shoye Zavetnoye pollen data between 4480 BC and 3250 BC. During the final centuries of the Stone Age, a new phase of land use began, as several anthropogenic indicators, such as Triticum, Cannabis, and Plantago lanceolata appear in the pollen data and a decrease in Pinus values is recorded. In general, the results indicate that socio-cultural transformations could have taken place already from the mid-5th millennium BC onwards, including new ways of utilizing the environment, perhaps also in the field of subsistence, even though the livelihood was based on foraging throughout the period. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
8. Postglacial succession of caddisfly (Trichoptera) assemblages in a central European montane lake
- Author
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Vondrák, Daniel, Schafstall, Nick B., Chvojka, Pavel, Chiverrell, Richard C., Kuosmanen, Niina, Tátosová, Jolana, and Clear, Jennifer L.
- Published
- 2019
- Full Text
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9. Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing.
- Author
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Rapuc, William, Sabatier, Pierre, Arnaud, Fabien, Palumbo, Antoine, Develle, Anne-Lise, Reyss, Jean-Louis, Augustin, Laurent, Régnier, Edouard, Piccin, Andrea, Chapron, Emmanuel, Dumoulin, Jean-Pascal, and von Grafenstein, Ulrich
- Subjects
- *
MASS-wasting (Geology) , *MEDITERRANEAN climate , *FLOODS , *LAKE sediments , *ANALYTICAL geochemistry , *WATERSHEDS - Abstract
Abstract A high-resolution sedimentological and geochemical analysis of a 21 m sediment sequence of Lake Iseo (Southern Alps, Italy) allowed for the reconstruction of the long-term flood frequency by visual identification of the event layers over the last 12 kyr cal BP. In a previous study that was undertaken on another sediment core from Lake Iseo, these layers were attributed to extreme surface runoff events. However, in this former core, large mass-wasting deposits that induce significant hiatuses did not permit a continuous record of flood events to be established. Such disturbances were absent in the core studied in the present paper. This permitted to establish a high-resolution continuous Holocene record. Based on the flood chronicle and sedimentological and XRF geochemical analyses, we found evidence of a major palaeohydrological transition at approximately 3.8 kyr cal BP, which was previously described as occurring in the western Mediterranean region. The oldest part of the record indeed presents a very low frequency of flood events (<1 flood/century), while after 4 kyr cal BP, the flood frequency increased. This pattern appears to be in agreement with other Southern Alpine paleo flood records. The transition is interpreted as a nonlinear climate response to the orbital-driven gradual decrease in summer insolation at 60°N, which together with the influence of the Mediterranean mesoscale precipitation events, is typical for the Mediterranean climate. However, the comparison of the flood record with the archaeological and historical data from the watershed suggests that human activity during the Roman period in the vicinity of the main tributaries also influenced the flood frequency. Even in a large Alpine lake and >2000 years ago, extreme precipitation events that were recorded through the sedimentation process can hence be impacted by the anthropization of the catchment area pointing the requirement of deeper studies of Earth surface critical zone pluri-millennial dynamics. Highlights • In the Alps, flood frequency is higher during period of cold and wetter climate. • A major palaeohydrological transition is observed at approximately 4 kyr cal BP. • From 2 kyr cal BP, human activity is the main driver of the SEB10 flood frequency. • In Alpine lowland lake, flood chronicle can be impacted by the anthropization. • Studying human activity is needed for flood-paleohydrological reconstructions. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
10. A first estimate of organic carbon storage in Holocene lake sediments in Alberta, Canada.
- Author
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Campbell, I. D., Campbell, C., Vitt, D. H., Kelker, D., Laird, L. D., Trew, D., Kotak, B., LeClair, D., and Bayley, S.
- Abstract
This paper reports a first estimate of the Holocene lake sediment carbon pool in Alberta, Canada. The organic matter content of lake sediment does not appear to depend strongly on lake size or other limnological parameters, allowing a simple first estimate in which we assume all Alberta lake sediment to have the same organic matter content. Alberta lake sediments sequester about 15 g C m
-2 yr-1 , for a provincial total of 0.23 Tg C yr-1 , or 2.3 Pg C over the Holocene. Alberta lakes may represent as much as 1/1700 of total global, annual permanent carbon sequestration. [ABSTRACT FROM AUTHOR]- Published
- 2000
- Full Text
- View/download PDF
11. Erosion under climate and human pressures: An alpine lake sediment perspective.
- Author
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Arnaud, Fabien, Poulenard, Jérôme, Giguet-Covex, Charline, Wilhelm, Bruno, Révillon, Sidonie, Jenny, Jean-Philippe, Revel, Marie, Enters, Dirk, Bajard, Manon, Fouinat, Laurent, Doyen, Elise, Simonneau, Anaëlle, Pignol, Cécile, Chapron, Emmanuel, Vannière, Boris, and Sabatier, Pierre
- Subjects
- *
EROSION , *LAKE sediments , *MOUNTAIN ecology , *HOLOCENE Epoch , *HYDROLOGY , *PREVENTION - Abstract
We review the scientific efforts over the last decades to reconstruct erosion from continuous alpine lake sediment records. We focused both on methodological issues, showing the growing importance of non-destructive high resolution approaches (XRF core-scanner) as well as progresses in the understanding of processes leading to the creation of an “erosion signal” in lakes. We distinguish “continuous records” from “event-records”. Both provide complementary information but need to be studied with different approaches. Continuous regionally-relevant records proved to be particularly pertinent to document regional erosion patterns throughout the Holocene, in particular applying the source to sink approach. Event-based approaches demonstrated and took advantage of the strong non-linearity of sediment transport in high altitude catchment areas. This led to flood frequency and intensity reconstructions, highlighting the influence of climate change upon flood dynamics in the mountain. The combination of different record types, both in terms of location (high vs. low elevation), sedimentology (high vs. low terrigenous contribution) and significance (local vs. regional) is one of the main outputs of this paper. It allows the establishment of comprehensive histories of NW French Alps erosion, but also and consequently, soil dynamics and hydrological patterns throughout the Holocene. We also discuss the influence of glacier dynamics, one of the major agents of erosion in the Alps. A major feature is the growing human influence upon erosion at a local scale since at least the middle of the Bronze Age (3500 cal. BP). However and according to the regional record from Lake Bourget, only few periods of rising erosion at local scales generated a regional record that can be discriminated from wetter climatic periods. Among them, the period between 200 BCE and 400 AD appeared to be marked by a generalised rise in human-triggered erosion at local scales in the northern French Alps. This review highlights the importance of modern high-resolution and interdisciplinary studies of lake sediments, in order to better understand the complex relationships between humans, climate and the Earth system in general. We strongly argue that regional integration of data is now required to move a step further. Such an integration is easier with cost- and time-effective methods as well as after a better definition of approaches and their limits. This should lead to a stronger collaboration between paleo-data producers and modellers in the near future. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
12. Reconstructing postglacial hydrologic and environmental change in the eastern Kenai Peninsula lowlands using proxy data and mass balance modeling.
- Author
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Broadman, Ellie, Kaufman, Darrell S., Anderson, R. Scott, Bogle, Sonya, Ford, Matthew, Fortin, David, Hendersone, Andrew C. G., Lacey, Jack H., Leng, Melanie J., McKay, Nicholas P., and Muñoz, Samuel E.
- Subjects
OXYGEN isotopes ,PENINSULAS ,FOREST microclimatology ,ENVIRONMENTAL history ,MAGNETIC susceptibility - Abstract
Despite extensive paleoenvironmental research on the postglacial history of the Kenai Peninsula, Alaska, uncertainties remain regarding the region's deglaciation, vegetation development, and past hydroclimate. To elucidate this complex environmental history, we present new proxy datasets from Hidden and Kelly lakes, located in the eastern Kenai lowlands at the foot of the Kenai Mountains, including sedimentological properties (magnetic susceptibility, organic matter, grain size, and biogenic silica), pollen and macrofossils, diatom assemblages, and diatom oxygen isotopes. We use a simple hydrologic and isotope mass balance model to constrain interpretations of the diatom oxygen isotope data. Results reveal that glacier ice retreated from Hidden Lake's headwaters by ca. 13.1 cal ka BP, and that groundwater was an important component of Kelly Lake's hydrologic budget in the Early Holocene. As the forest developed and the climate became wetter in the Middle to Late Holocene, Kelly Lake reached or exceeded its modern level. In the last ca. 75 years, rising temperature caused rapid changes in biogenic silica content and diatom oxygen isotope values. Our findings demonstrate the utility of mass balance modeling to constrain interpretations of paleolimnologic oxygen isotope data, and that groundwater can exert a strong influence on lake water isotopes, potentially confounding interpretations of regional climate. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
13. A 14,500-year record of landscape change from Okpilak Lake, northeastern Brooks Range, northern Alaska
- Author
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Oswald, W. Wyatt, Gavin, Daniel G., Anderson, Patricia M., Brubaker, Linda B., and Hu, Feng Sheng
- Published
- 2012
- Full Text
- View/download PDF
14. Variation in the moisture regime of northeastern interior Alaska and possible linkages to the Aleutian Low: inferences from a late-Holocene δ18O record
- Author
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Chipman, Melissa L., Clegg, Benjamin F., and Hu, Feng Sheng
- Published
- 2012
- Full Text
- View/download PDF
15. Evaluating Holocene climate change in northern Norway using sediment records from two contrasting lake systems
- Author
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Balascio, Nicholas L. and Bradley, Raymond S.
- Published
- 2012
- Full Text
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16. A sedimentary and geochemical record of water-level changes from Rantin Lake, Yukon, Canada
- Author
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Pompeani, D. P., Steinman, B. A., and Abbott, M. B.
- Published
- 2012
- Full Text
- View/download PDF
17. Lake sediment records on climate change and human activities since the Holocene in Erhai catchment, Yunnan Province, China
- Author
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Shen, Ji, Yang, Liyuan, Yang, Xiangdong, Matsumoto, R., Tong, Guobang, Zhu, Yuxin, Zhang, Zhenke, and Wang, Sumin
- Published
- 2005
- Full Text
- View/download PDF
18. A combined carbon and hydrogen isotope approach to reconstruct the SE Asian paleomonsoon : Impacts on the Angkor Civilization and links to paleolimnology
- Author
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Yamoah, Kweku Kyei Afrifa
- Subjects
hydrogen isotopes ,lake sediment ,Holocene ,peat ,summer monsoon ,biomarkers ,Geosciences, Multidisciplinary ,Thailand ,Multidisciplinär geovetenskap - Abstract
Changes in monsoon patterns not only affect ecosystems and societies but also the global climate system in terms of heat energy and humidity transfer from the equator to higher latitudes. However, understanding the mechanisms that drive monsoon variability on longer timescales remains a challenge, partly due to sparse paleoenvironmental and paleoclimatic data. This thesis, which contributes new hydroclimate data sets for the Asian monsoon region, seeks to advance our understanding of the mechanisms that contributed to Southeast Asian summer monsoon variability in the past. Moreover, it explores how past climatic conditions may have impacted societies and ecosystems. In this study lake sediment and peat sequences from northeastern and southern Thailand have been investigated using organic geochemistry, and more specifically the stable carbon and hydrogen isotopic composition of specific biomarkers (n-alkanes, botryococcenes, and highly branched isoprenoids). The hydrogen isotopic composition of leaf waxes (δDwax) in Thailand was shown to relate to the amount of precipitation and the extent of the El Niño Southern Oscillation. Higher values of δDwax can be interpreted as reflecting relatively dry climatic conditions, whereas lower values relate to wetter conditions. The hydroclimate reconstruction for northeastern Thailand, based on the sedimentary record of Lake Kumphawapi, suggests higher moisture availability between ca. 10,700 cal. BP and ca. 7,000 cal. BP likely related to a strengthened early Holocene summer monsoon. Moisture availability decreased during the mid-Holocene, but seems to have increased again around 2,000 years ago and has fluctuated since. The high-resolution Lake Pa Kho peat sequence, which allows for a sub-centennial reconstruction of moisture availability, indicates that the wettest period occurred between ca. 700 and ca. 1000 CE whereas driest intervals were from ca. 50 BCE to ca. 700 CE and from ca. 1300 to ca. 1500 CE. Hydroclimate comparison of Pa Kho’s δDwax record with other paleoclimate records from the Asian-Pacific region suggests that El Niño-like conditions led to Northeastern Thailand being wetter, whereas La Niña-like conditions led to drier conditions. Regional hydroclimate variability also greatly influenced the Angkor Civilization, which flourished between ca. 845 and ca. 1450 CE. The shift from drier to wetter conditions coincided in time with the rise of the Angkor Civilization and likely favored the intense agriculture needed to sustain the empire. The gradual decline in moisture availability, which started after ca. 1000 years CE, could have stretched the hydrological capacity of Angkor to its limit. It is suggested that Angkor’s population resorted to unconventional water sources, such as wetlands, as population growth continued, but summer monsoon rains weakened. The 150-year long record of Lake Nong Thale Prong in southern Thailand offers insights into decadal-scale hydroclimatic changes that can be connected to the instrumental record. δDwax-based hydroclimate was drier from ~1857 to 1916 CE and ~1970 to 2010 CE and wetter from ~1916 to 1969 CE. Drier climatic conditions between ~1857 and 1916 CE coincided with oligotrophic lake waters and a dominance of the green algae Botryococcus braunii. Higher rainfall between ~1916 and 1969 CE concurred with an increase in diatom blooms while eutrophic lake water conditions were established between ~1970–2010 CE. At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Monsoon project
- Published
- 2016
19. Asian monsoon over mainland Southeast Asia in the past 25 000 years
- Author
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Chabangborn, Akkaneewut
- Subjects
palaeo-vegetation ,lake sediment ,Climate Research ,Last Glacial Maximum ,Holocene ,Asian monsoon ,palaeoclimate ,ITCZ ,Klimatforskning - Abstract
The objective of this research is to interpret high-resolution palaeo-proxy data sets to understand the Asian summer monsoon variability in the past. This was done by synthesizing published palaeo-records from the Asian monsoon region, model simulation comparisons, and analysing new lake sedimentary records from northeast Thailand. Palaeo-records and climate modeling indicate a strengthened summer monsoon over Mainland Southeast Asia during the Last Glacial Maximum (LGM), compared to dry conditions in other parts of the Asian monsoon region. This can be explained by the LGM sea level low stand, which exposed Sundaland and created a large land-sea thermal contrast. Sea level rise ~19 600 years before present (BP), reorganized the atmospheric circulation in the Pacific Ocean and weakened the summer monsoon between 20 000 and 19 000 years BP. Both the Mainland Southeast Asia and the East Asian monsoon hydroclimatic records point to an earlier Holocene onset of strengthened summer monsoon, compared to the Indian Ocean monsoon. The asynchronous evolution of the summer monsoon and a time lag of 1500 years between the East Asian and the Indian Ocean monsoon can be explained by the palaeogeography of Mainland Southeast Asia, which acted as a land bridge for the movement of the Intertropical Convergence Zone. The palaeo-proxy records from Lake Kumphawapi compare well to the other data sets and suggest a strengthened summer monsoon between 10 000 and 7000 years BP and a weakening of the summer monsoon thereafter. The data from Lake Pa Kho provides a picture of summer monsoon variability over 2000 years. A strengthened summer monsoon prevailed between BC 170-AD 370, AD 800-960 and since AD 1450, and was weaker about AD 370-800 and AD 1300-1450. The movement of the mean position of the Intertropical Convergence Zone explains shifts in summer monsoon intensity, but weakening of the summer monsoon between 960 and 1450 AD could be affected by changes in the Walker circulation. At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript..
- Published
- 2014
20. Ecological and human land-use indicator value of fungal spore morphotypes and assemblages.
- Author
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Doyen, Elise and Etienne, David
- Abstract
The value of non-pollen palynomorphs (NPPs) to complement reconstructions of past communities and environments has led to the identification of an increasing number of microfossil morphotypes. Unfortunately, limited knowledge about their specific ecological indicator values still restricts the interpretation of NPP accumulation rates or assemblage variations. Here, a comparison with classical palaeoecological proxies along a sedimentary sequence has been tested to improve the ecological indicator values of NPP morphotypes. Pollen, geochemical and NPP analyses performed on the same samples all along the Holocene sedimentary sequence of Lac de Moras (France) were compared using principal component analysis to identify statistical relationships and to establish correlations between all these parameters. Ecological indicator values were obtained for some morphotypes such as UG-1097 which is related to specific taxa ( Corylus sp.), or Diporotheca rhizophila defined as an indicator of the local presence of alder swamp habitat. However, most of the NPP morphotypes can be combined in two opposite NPP assemblages reflecting the change from natural to managed ecosystems at the drainage basin scale and over the Holocene. It more specifically illustrates a change in the source of organic matter transferred to the lake system provided from the plant debris of woodland cover (litter) to organic matter from animal excreta (dung and manure). [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
21. Holocene summer temperature reconstruction from sedimentary chlorophyll content, with treatment of age uncertainties, Kurupa Lake, Arctic Alaska.
- Author
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Boldt, Brandon R, Kaufman, Darrell S, McKay, Nicholas P, and Briner, Jason P
- Subjects
CLIMATE change ,LAKE sediments ,HOLOCENE extinction ,TEMPERATURE control ,HOLOCENE Epoch ,PALEOCLIMATOLOGY - Abstract
Quantitative records of pre-industrial temperature changes are fundamental for understanding long-term natural climate variability. We used visible reflectance spectroscopy to measure chlorophyll content (and its derivatives) in a sediment core from Kurupa Lake, north-central Brooks Range, Alaska, to reconstruct summer temperature and the number of annual non-freezing days over the past 5.7 ka. A calibration-in-time approach was used to convert downcore changes in chlorophyll content to the climate variables, and an ensemble approach was used to integrate age and calibration uncertainties. The strongest correlation (rmedian = 0.69, pmedian = 0.02, RMSEP = 1.9°C) is for summer (June through September) temperature using the 20th Century Reanalysis Project dataset. The chlorophyll-inferred 3-year-mean summer temperature shows that the warmest century (3.0–2.9 ka BP) was about 3.0°C (90% range of the ensemble members = 2.3–4.0°C) higher and that the coldest century (1.4–1.3 ka BP) was about 5.5°C lower (90% range = −7.6°C to −5.0°C) than during the reference period (AD 1961–1990). Century-to-century temperature changes over the past 5.7 ka at Kurupa Lake have been large (90% range = −2.8°C to 3.1°C shifts in centennial mean), including the shift between the 19th and 20th centuries, which was above the 90th percentile of temperature changes across all representations of the reconstruction. In contrast to most Northern Hemisphere temperature reconstructions, Kurupa Lake shows no overall millennial-scale cooling trend. We suggest that increased summer duration (by 4.3 days during the last 6 ka) along with no long-term increase in sea-ice cover over the adjacent Chukchi Sea counter-balanced the influence of decreased insolation intensity on the aquatic productivity in Kurupa Lake. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
22. Human-environment interaction during the Holocene along the shoreline of the Ancient Lake Ladoga: A case study based on palaeoecological and archaeological material from the Karelian Isthmus, Russia
- Author
-
Alexandra Golyeva, T. V. Sapelko, Kerkko Nordqvist, Denis A. Kuznetsov, Teija Alenius, Anna Ludikova, Dmitry Gerasimov, Department of Cultures, and Archaeology
- Subjects
010506 paleontology ,Archeology ,the Karelian Isthmus ,medicine.disease_cause ,01 natural sciences ,615 History and Archaeology ,hunter-gatherer archaeology ,Pollen ,HISTORY ,medicine ,0601 history and archaeology ,SEA-LEVEL CHANGES ,Charcoal ,Holocene ,0105 earth and related environmental sciences ,Earth-Surface Processes ,DISPLACEMENT ,Shore ,STONE-AGE ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,060102 archaeology ,Ecology ,Ancient lake ,biology ,LAND-USE ,NICHE CONSTRUCTION ,POLLEN ,Paleontology ,Sediment ,06 humanities and the arts ,15. Life on land ,palaeoecology ,FINLAND ,biology.organism_classification ,Archaeology ,SOUTHERN ,Diatom ,lake sediment ,visual_art ,visual_art.visual_art_medium ,Paleoecology ,BALTIC SEA ,Geology ,human-environment interactions - Abstract
This paper presents the results of pollen, diatom, charcoal, and sediment analyses from Lake Bol’shoye Zavetnoye, situated between the Gulf of Finland and Lake Ladoga on the Karelian Isthmus, north-western Russia. The main goal is to contribute to the discussion of Neolithic land use in north-eastern Europe. The article aims to answer questions related to Stone Age hunter-gatherer economy, ecology, and anthropogenic environmental impact through a comprehensive combination of multiple types of palaeoecological data and archaeological material.According to diatom data, Lake Bol’shoye Zavetnoye was influenced by the water level oscillations of Ancient Lake Ladoga during much of the Holocene. Intensified human activity and prolonged human occupation become visible in the Lake Bol’shoye Zavetnoye pollen data between 4480 BC and 3250 BC. During the final centuries of the Stone Age, a new phase of land use began, as several anthropogenic indicators, such as Triticum, Cannabis, and Plantago lanceolata appear in the pollen data and a decrease in Pinus values is recorded. In general, the results indicate that socio-cultural transformations could have taken place already from the mid-5th millennium BC onwards, including new ways of utilizing the environment, perhaps also in the field of subsistence, even though the livelihood was based on foraging throughout the period.
- Published
- 2020
23. Biogeochemical evidence for hydrologic changes during the Holocene in a lake sediment record from southeast Greenland.
- Author
-
Balascio, Nicholas L, D’Andrea, William J, Bradley, Raymond S, and Perren, Bianca B
- Subjects
BIOGEOCHEMICAL cycles ,HOLOCENE Epoch ,LAKE sediments ,MARINE west coast climate ,DIATOMS ,PALEOCLIMATOLOGY - Abstract
Holocene paleoclimate records from Greenland help us understand the response of the Greenland Ice Sheet and regional oceanic and atmospheric circulation systems to natural climate variability in order to place recent changes in a longer-term perspective. Here biogeochemical analysis of a lake sediment core from southeast Greenland is used to define changes in moisture balance and runoff during the Holocene in a catchment near the margin of the Greenland Ice Sheet. A 1.6 m sediment core that spans the last 8.8 ka was recovered from Flower Valley Lake on Ammassalik Island. Magnetic susceptibility, diatoms, bulk biogeochemical properties (TOC, C/N, δ13Corg), and lipid biomarkers (n-alkanes; C16–C31) reveal changes in clastic sedimentation and the relative input of terrestrial- and aquatic-derived organic matter. Hydrogen isotope values (δD) of mid- (n-C25) and long-chain (n-C29, n-C31) n-alkanes allow reconstruction of δD of precipitation and summertime evaporation of lake water. Following a period of early lake ontogeny and landscape stabilization after deglaciation from 8.4 to 7.0 ka, the mid Holocene, 8.4–4.1 ka, is characterized by greater evaporative enrichment of the lake water as indicated by δD records. After 4.1 ka, there is a decrease in evaporative enrichment of the lake water. There is also an abrupt transition to more variable sedimentation marked by sharp increases in magnetic susceptibility, C/N, δ13Corg, and the concentration of long-chain n-alkanes, showing periodic delivery of terrestrial organic matter and clastic sediment to the lake. Higher insolation during the mid Holocene resulted in a warmer and drier climate with longer ice-free periods in the summer and enhanced evaporation of lake water. The reduction in insolation and colder temperatures during the late Holocene caused a reduction in evaporation of lake water over the last 4.1 ka and was accompanied by periodic increases in surface runoff, which correspond with intervals of cold Greenland Ice Sheet surface temperatures. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
24. Late Pleistocene- Holocene records from Lake Ulaan, southern Mongolia: implications for east Asian palaeomonsoonal climate changes.
- Author
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LEE, MIN KYUNG, LEE, YONG IL, LIM, HYOUN SOO, LEE, JAE IL, and YOON, HO IL
- Abstract
ABSTRACT A 5.88-m-long core taken from Lake Ulaan was studied for high-resolution paleoclimatic changes during the last 17 000 years. The core sediments are divided into three units based on grain-size distribution: unit 1 (top to 392 cm depth, covering the last 11 200 years), unit 2 (392-530 cm, 11.2-15 ka) and unit 3 (530-588 cm, 15.0-16.7 ka). These sediments were transported by local westerly winds (units 1 and 3) and fluvial processes (unit 2). Based on major element compositions and geological setting of adjacent areas, provenance of unit 1 sediments was interpreted to be the Lake terrane, and that of unit 2 to be the Idermeg terrane. Unit 3 sediments were derived from the Gobi Altai terrane. The records of total organic carbon, C/N ratio and weathering intensity suggest that paleoclimate in the source area of Lake Ulaan sediment was most humid during the Early Holocene, humid during the mid-Holocene and dry in the Late Holocene. The decrease of humidity through the Holocene is a typical characteristic of the East Asian monsoon region. Comparison with lacustrine records of other Mongolia regions suggests that the northern boundary of East Asian summer-monsoon influence could have been located further north than previously assumed. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
25. A 17,300-year record of mercury accumulation in a pristine lake in southern Chile.
- Author
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Hermanns, Y.-M. and Biester, H.
- Abstract
Anthropogenic mercury accumulation in lake sediments has been studied extensively, but natural processes that controlled mercury accumulation in the past are still poorly understood. We present a 17,300-year record of mercury accumulation in the sediments of Lake Hambre, southernmost Patagonia, Chile (53°S, 70°W), in combination with an investigation of environmental changes in the region. Mercury accumulation in the remote pristine lake varied appreciably, as much as 16×, exceeding the anthropogenic forcing of atmospheric mercury fluxes by a factor of 3-5. Principal Component Analysis revealed that short-term variations were not related to changes in atmospheric mercury deposition or to fluxes of mineral soil into the lake. Instead, there was significant covariation between short-term changes in mercury and catchment-derived trace elements, e.g. copper and yttrium, throughout the past 17,000 years. Covariation between mercury and carbon concentration in some parts of the record suggests that fluxes of particulate and dissolved organic matter from the catchment to the lake account for short-term variations in mercury accumulation. Nevertheless, over the long term, there is no common trend for mercury accumulation and organic matter flux. The median mercury accumulation rate was rather constant (29 μg m a), whereas the flux of terrestrial organic matter into the lake increased through time. We hypothesize that this was a consequence of a progressive decrease in the input of terrestrial organic matter-bound mercury through time. Whereas production of terrestrial organic matter increased over the long term because of development of catchment vegetation and soils, following glacier retreat, amounts of mercury, copper and yttrium provided by atmospheric deposition and bedrock weathering remained relatively constant. As a consequence, despite increased fluxes of terrestrial organic matter to the lake, fluxes of mercury remained constant. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
26. Environmental magnetic studies of sediment cores from Gonghai Lake: implications for monsoon evolution in North China during the late glacial and Holocene.
- Author
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Chen, Fahu, Liu, Jianbao, Xu, Qinghai, Li, Yuecong, Chen, Jianhui, Wei, Haitao, Liu, Qingsong, Wang, Zongli, Cao, Xianyong, and Zhang, Shengrui
- Abstract
Environmental magnetic studies were conducted on a 9.42-m-long sediment core from Gonghai Lake, North China. Radiocarbon dating indicates that the record spans the last 15,000 cal year BP. The principal magnetic mineral in the sediments is pseudo-single domain magnetite of detrital origin with minimal post-depositional alteration. Although the variations in the concentration of detrital magnetic minerals and their grain size throughout the core reflect inputs from both soil erosion and eolian dust, it is shown that their climatic and environmental significance changes with time. In the lowermost part of the core, ~15,000-11,500 cal year BP, the magnetic minerals were supplied mainly by bedrock erosion, soil erosion and dust input when climate ameliorated after the cold and dusty last glacial maximum. The increasing magnetic susceptibility (χ) in this interval may indicate a combination of changes in the lake environment together with catchment-surface stabilization and a decreasing proportion of dust input. In the central part of the core, ~11,500-1,000 cal year BP, the detrital magnetic minerals mainly originated from dust inputs from outside the catchment when the lake catchment was covered by forest, and catchment-derived sediment supply (and thus the lake sediment accumulation rate) were minimal. The generally low concentration of magnetic minerals in this part of the core reflects the highest degree of soil stability and the strongest summer monsoon during the Holocene. In the uppermost part of the core, the last ~1,000 years, detrital magnetic minerals mainly originated from erosion of catchment soils when the vegetation cover was sparse and the sediment accumulation rates were high. Within this part of the core the high magnetic susceptibility reflects strong pedogenesis in the lake catchment, and thus a strong summer monsoon. This scenario is similar to that recorded in loess profiles. Overall, the results document three main stages of summer monsoon history with abrupt shifts from one stage to another: an increasing and variable summer monsoon during the last deglacial, a generally strong summer monsoon in the early and middle Holocene and a weak summer monsoon in the late Holocene. The results also suggest that different interpretational models may need to be applied to lake sediment magnetic mineral assemblages corresponding to different stages of environmental evolution. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
27. A Holocene record of Pacific Decadal Oscillation (PDO)-related hydrologic variability in Southern California (Lake Elsinore, CA).
- Author
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Kirby, M. E., Lund, S. P., Patterson, W. P., Anderson, M. A., Bird, B. W., Ivanovici, L., Monarrez, P., and Nielsen, S.
- Abstract
High-resolution terrestrial records of Holocene climate from Southern California are scarce. Moreover, there are no records of Pacific Decadal Oscillation (PDO) variability, a major driver of decadal to multi-decadal climate variability for the region, older than 1,000 years. Recent research on Lake Elsinore, however, has shown that the lake's sediments hold excellent potential for paleoenvironmental analysis and reconstruction. New 1-cm contiguous grain size data reveal a more complex Holocene climate history for Southern California than previously recognized at the site. A modern comparison between the twentieth century PDO index, lake level change, San Jacinto River discharge, and percent sand suggests that sand content is a reasonable, qualitative proxy for PDO-related, hydrologic variability at both multi-decadal-to-centennial as well as event (i.e. storm) timescales. A depositional model is proposed to explain the sand-hydrologic proxy. The sand-hydrologic proxy data reveal nine centennial-scale intervals of wet and dry climate throughout the Holocene. Percent total sand values >1.5 standard deviation above the 150-9,700 cal year BP average are frequent between 9,700 and 3,200 cal year BP ( n = 41), but they are rare from 3,200 to 150 cal year BP ( n = 6). This disparity is interpreted as a change in the frequency of exceptionally wet (high discharge) years and/or changes in large storm activity. A comparison to other regional hydrologic proxies (10 sites) shows more then occasional similarities across the region (i.e. 6 of 9 Elsinore wet intervals are present at >50% of the comparison sites). Only the early Holocene and the Little Ice Age intervals, however, are interpreted consistently across the region as uniformly wet (≥80% of the comparison sites). A comparison to two ENSO reconstructions indicates little, if any, correlation to the Elsinore data, suggesting that ENSO variability is not the predominant forcing of Holocene climate in Southern California. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
28. Investigating the influence of hydrogeomorphic setting on the response of lake sedimentation to climatic changes in the Uinta Mountains, Utah, USA.
- Author
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Corbett, Lee B. and Munroe, Jeffrey S.
- Abstract
Reader Lake and Elbow Lake, two high-altitude lakes in the Uinta Mountains of Utah, are located approximately 2 km apart, at similar elevations, and within identical vegetation communities. Loss on ignition, carbon to nitrogen ratios, biogenic silica, and sediment grain size were analyzed throughout percussion cores retrieved from both lakes to construct continuous time series spanning 14 to ca. 2 ka BP. Given the proximity of the lakes, it is assumed that both were subjected to the same climatic forcing over this time. Accordingly, the first goal of this study was to consider these two multiproxy datasets in concert to yield an integrated paleoclimate record for this region. Close inspection of the records identified discrepancies indicating that the lakes responded to climate changes in different ways despite their proximity and similar setting. Clarifying these differences and understanding why the two lakes behaved differently at certain times was the second goal of this study. Overall, the paleoclimatic records document lake formation in the latest Pleistocene following glacier retreat. Buried glacier ice at the location of Reader Lake may have persisted through the Younger Dryas. Both lakes became biologically productive ca. 11.5 ka BP, and the first appearance of conifer needles indicates that trees had replaced alpine tundra in these watersheds by 10.5 ka BP. The interval from 10 to 6 ka BP was marked by a dramatic increase in precipitation, perhaps related to enhanced monsoonal circulation driven by the insolation maximum. The two lakes recorded this event in notably contrasting ways given their differing hydrogeomorphic settings. Precipitation decreased from 6 to 4 ka BP, and low water levels and drought conditions marked the interval from 4.0 to 2.7 ka BP. The integrated paleoclimate record developed from these cores provides a useful point of comparison with other records from the region. The differences between the records from these closely spaced lakes underscore the need to consider hydrogeomorphic setting when evaluating the suitability of a lake for a paleolimnological study. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
29. Vegetation and climate changes during the last 8660 cat. a BP in central Mongolia, based on a high-resolution pollen record from Lake Ugii Nuur.
- Author
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Wang Wei, Ma YuZhen, Feng ZhaoDong, Meng HongWei, Sang YanLi, and Zhai XinWei
- Subjects
POLLEN ,VEGETATION & climate ,CLIMATE change ,HUMIDITY ,PLANTS & the environment - Abstract
Based on modern pollen studies and reliable chronology of nine AMS
14 C dates, a detailed history of vegetation and climate changes during the past 8660 cal. a BP was reconstructed by a high-resolution pollen record from Ugii Nuur in central Mongolia. Poaceae-steppe dominated the study area and the climate was mild and semi-humid before 7800 cal. a BP with a noticeable cool and humid interval at 8350-8250 cal. a BP. Xerophytic plant increased and the climate became warm and dry gradually since 7800 cal. a BP. From 6860 to 3170 cal. a BP, semi-desert steppe expanded, suggesting a prolonged warm and dry climate. Between 3170 and 2340 cal. a BP, regional forest steppe expanded whereas semi-desert steppe retreated, indicating the climate became cool and wet gradually and the humidity reached the maximum at the end of this stage. From 2340 to 1600 cal. a BP, a general cool and wet climate prevailed. And the climatic instability increased after 1600 cal. a BR Review of regional published palaeoclimatic records implies that the mid-Holocene dry climate might have prevailed in vast areas from central Mongolia to arid areas of northwest China. Pollen-based climate reconstruction for UGO4 core was well correlated with the result of climate model on Central Asia by Bush. In addition, several abrupt climatic events (cool and wet) were found and some could be broadly compared with the cool events in Atlantic. [ABSTRACT FROM AUTHOR]- Published
- 2009
- Full Text
- View/download PDF
30. Integrated varve and pollen-based temperature reconstruction from Finland: evidence for Holocene seasonal temperature patterns at high latitudes.
- Author
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Ojala, Antti E. K., Alenius, Teija, Seppä, Heikki, and Giesecke, Thomas
- Subjects
CLIMATE change ,METEOROLOGICAL precipitation ,MINIMUM temperature forecasting ,SEASONS ,CLIMATOLOGY ,HOLOCENE stratigraphic geology ,GEOGRAPHICAL positions ,SCIENTIFIC method - Abstract
A detailed understanding of decadal to millennial-scale climate changes requires seasonal-scale (summer-winter) reconstructions of past precipitation and temperature fluctuations. Comparing seasonally resolved varve records with pollen-based sum of growing degree-days (GDD) reconstructions from Lake Nautajärvi, we examined the intra-annual nature of climate variability in central southern Finland during the Holocene. The organic varve record and the GDD reconstruction show roughly comparable trends supporting the interpretation that both proxies predominantly reflect summer temperatures in the study area. The records suggest low but rising early-Holocene (9500 to 8500 cal. yr BP) summer temperatures. The Holocene Thermal Maximum (HTM) in the GDD record dates to about 7500 to 4500 cal. yr BP, but the organic varve record along with reconstructed changes in vegetation composition, notably a peak of Tilia pollen percentages, indicate that during the HTM there was a trend towards a more continental climate with maximum mid-summer temperatures reached at 6500 to 4500 cal. yr BP. Both records reflect the start of the post-HTM cooling at about 4500 cal. yr BP, simultaneously with an increase of the amount of catchment erosion and mineral matter influx into the lake, suggesting gradually colder and/or longer winters with high net accumulation of snow. The organic varve record and the GDD record start to diverge at 2000 cal. yr BP, possibly owing to the human influence on catchment processes. The reconstructed mid-Holocene summer temperature peak deviates from the regional climate model outputs, which suggest highest summer temperatures during the early Holocene. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
31. Untitled.
- Subjects
ENVIRONMENTAL geochemistry ,ENVIRONMENTAL chemistry ,BIOGEOCHEMICAL cycles - Abstract
The article presents abstracts of several studies on environmental geochemistry. Some of the abstracts presented include "Biogeochemical Cycling of Nutrients in Karstic Catchments, Southwestern China: Linkages to Changes of Eco-Environments," by Congqiang Liu and "Emerging Organic Contamination in China," by Guibin Jiang and colleagues.
- Published
- 2006
32. Use of scanning electron microscopy to investigate records of soil weathering preserved in lake sediment.
- Author
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Ewing, Holly A. and Nater, Edward A.
- Subjects
SOILS & climate ,PALEONTOLOGY ,SCANNING electron microscopy - Abstract
Reconstruction of soil weathering is one of the more difficult problems for palaeoecologists interested in landscape-scale environmental changes. Here we use scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDS) to study the pitting of feldspars in soils and lake sediments at two sites in the Great Lakes region, USA. A semi-quantitative feldspar weathering index (FWI) allows description of the weathering status for large numbers of individual grains, and reveals differences among soil horizons and strata of lake sediment as well as between the two sites. Feldspars in upper soil horizons generally have greater FWI than those in lower horizons, but analyses also suggest considerable weathering in the soil C horizon at the site with more rapid water infiltration. At one site, the FWI of upper soil horizons and surface lake sediment are similar, implying that lake sediments have the potential to record changes in soil over time. However, differences between upper soil horizons and surface sediment at the other site highlight the need to examine more sites and more profiles within sites to better relate catchment and sediment characteristics. We interpret increases in the FWI over time within lake sediments as evidence of progressive weathering of soils and conclude that the sites had different histories of soil development. However, the complexities of sediment deposition in lakes and the paucity of information relating FWI to soil characteristics prevent straightforward reconstruction of soil development. Variability within each record appears tied to initial grain chemistry, depositional environment, changes in lake level and progressive degradation of grains. As more information relating micromorphology to soil characteristics becomes available, this technique should become a more useful complement to chemical studies of lake sediment. [ABSTRACT FROM AUTHOR]
- Published
- 2003
- Full Text
- View/download PDF
33. Holocene landscape development and human impact in the Connemara Uplands, Western Ireland.
- Author
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Huang, Chun Chang
- Subjects
LANDSCAPES ,BIOGEOGRAPHY - Abstract
Aim Aim Investigate: (1) the role of human impact in shaping the landscape and particularly the initiation of blanket bog; (2) the short-lived abrupt changes and their causation; (3) the phenomenon of large-scale upland peat erosion to answer the question of when and why erosion of upland blanket peat commenced in the Connemara uplands. Location Lough Maumeen in the Maumeen Gap, Connemara, Western Ireland. Methods Pollen, sedimentary analysis and
14 C dating on the lake sediment cores. Results Pollen diagrams, charcoal fragments, bulk and dry densities, mineral content (or loss-on-ignition), whole core magnetic susceptibility, specific magnetic susceptibility for the core profile. Main conclusions Pine-dominated woodland developed from 9250 BP. Human activities effected the deforestation between 5050–4000 BP. Peat bog initiated on the wet hollow ground in the gap during the elm decline. The major expansion of blanket bog landscape in the upland commenced at 4000 BP following immediately the Taxus decline. Human impact was the dynamic force responsible for the destruction of the woodland and the formation of blanket bog in the upland. Three episodes of short-lived erosion events were identified between 8650–8400 BP, 5450–5250 BP, and 600–200 cal. BP, respectively. They are very different from each other in their causation. Large-scale peat erosion is a recent phenomenon. It has been caused by intensive sheep grazing, which has been extended to the upland blanket bogs since the late eighteen century. [ABSTRACT FROM AUTHOR]- Published
- 2002
- Full Text
- View/download PDF
34. Evolution of the trophic state of Lake Annecy (eastern France) since the last glaciation as indicated by iron, manganese and phosphorus speciation.
- Author
-
Loizeau, Jean-Luc, Span, Daniel, Coppee, Véronique, and Dominik, Janusz
- Abstract
Lake Annecy sediments have been studied to provide an insight into the evolution of the lake trophic state in response to climate changes during the Holocene. Determination of the concentration of carbonate, Fe, Mn, and different forms of P in conjunction with total sediment fluxes derived from
14 C ages allows an estimation of yearly fluxes of these sediment components. High fluxes of endogenic carbonate occur during the early to middle Holocene. Non apatitic inorganic phosphorus flux is variable but shows some higher-than-present values during this period. These observations are interpreted as being a result of enhanced productivity by favourable conditions for phytoplankton development. In addition, the low Mn/Fe ratio of the redox-sensitive forms of these elements recorded during this period suggests low oxygen concentrations in the bottom waters. Therefore it appears that the lake may have undergone oxygen depletion in the bottom water during the warmer-than-present periods, due to increased productivity and subsequent oxygen consumption from the decay of organic matter. With future climate changes, this suggests that lake water quality may likely degrade under global warming. [ABSTRACT FROM AUTHOR]- Published
- 2001
- Full Text
- View/download PDF
35. Holocene-long record of flood frequency in the Southern Alps (Lake Iseo, Italy) under human and climate forcing
- Author
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Edouard Régnier, Fabien Arnaud, Jean-Pascal Dumoulin, Andrea Piccin, Laurent Augustin, Antoine Palumbo, Anne-Lise Develle, William Rapuc, Jean-Louis Reyss, Emmanuel Chapron, Ulrich von Grafenstein, Pierre Sabatier, Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Océan et Interfaces (OCEANIS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Géochrononologie Traceurs Archéométrie (GEOTRAC), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Regione Lombardia, Géographie de l'environnement (GEODE), Université Toulouse - Jean Jaurès (UT2J), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de mesure du carbone 14 (LMC14 - UMS 2572), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Radioprotection et de Sûreté Nucléaire (IRSN)-Ministère de la Culture et de la Communication (MCC)-Centre National de la Recherche Scientifique (CNRS), Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université Toulouse - Jean Jaurès (UT2J)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université Toulouse - Jean Jaurès (UT2J)
- Subjects
Mediterranean climate ,010506 paleontology ,010504 meteorology & atmospheric sciences ,[SDE.MCG]Environmental Sciences/Global Changes ,Oceanography ,01 natural sciences ,Flood chronicle ,Sequence (geology) ,C2FN ,Precipitation ,[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology ,Holocene ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences ,Global and Planetary Change ,Flood myth ,Sediment ,Human impact ,Anthropization ,[SHS.GEO]Humanities and Social Sciences/Geography ,Lake sediment ,13. Climate action ,Physical geography ,Surface runoff ,Geology ,Southern Alps - Abstract
A high-resolution sedimentological and geochemical analysis of a 21 m sediment sequence of Lake Iseo (Southern Alps, Italy) allowed for the reconstruction of the long-term flood frequency by visual identification of the event layers over the last 12 kyr cal BP. In a previous study that was undertaken on another sediment core from Lake Iseo, these layers were attributed to extreme surface runoff events. However, in this former core, large mass-wasting deposits that induce significant hiatuses did not permit a continuous record of flood events to be established. Such disturbances were absent in the core studied in the present paper. This permitted to establish a high-resolution continuous Holocene record. Based on the flood chronicle and sedimentological and XRF geochemical analyses, we found evidence of a major palaeohydrological transition at approximately 3.8 kyr cal BP, which was previously described as occurring in the western Mediterranean region. The oldest part of the record indeed presents a very low frequency of flood events ( 2000 years ago, extreme precipitation events that were recorded through the sedimentation process can hence be impacted by the anthropization of the catchment area pointing the requirement of deeper studies of Earth surface critical zone pluri-millennial dynamics.
- Published
- 2019
36. Mechanism of variations in environmental magnetic proxies of lake sediments from Nam Co, Tibet during the Holocene
- Author
-
Su, YouLiang, Gao, Xing, Liu, QingSong, Hu, PengXiang, Duan, ZongQi, Jiang, ZhaoXia, Wang, JunBo, Zhu, LiPing, Doberschütz, Stefan, Mäusbacher, Roland, Daut, Gerhard, and Haberzettl, Torsten
- Published
- 2013
- Full Text
- View/download PDF
37. Holocene history of lacustrine and marsh sediments in a dune-blockeddrainage, southwestern Nebraska Sand Hills, U.S.A.
- Author
-
Mason, J. P., Loope, D. B., and Swinehart, J. B.
- Abstract
As many as 2500 interdune lakes lie within the Nebraska Sand Hills, a 50000 km stabilized sand sea. The few published data on cores from these lakes indicate they are typically underlain by less than two m of Holocene lacustrine sediments. However, three lakes in the southwestern Sand Hills, Swan, Blue, and Crescent, contain anomalously thickmarsh (peat) and lacustrine (gyttja) sediments. Swan Lake basin contains as much as 8 m of peat, which was deposited between about 9000 and 3300 years ago. This peat is conformably overlain by as much as 10.5 m of gyttja. The sediment record in Blue lake, which is 3 km downgradient from Swan lake, dates back to only about 6000 years ago. Lessthan two m of peat, which was deposited from 6000 to 5000 years ago,is overlain by 12 m of gyttja deposited in the last 4300 years. Crescent Lake basin, one km downgradient from Blue Lake, has a similar sediment history except for a lack of known peat deposits. Recently, a 8-km long segment of a paleovalley was documented running beneath thethree lakes and connecting to the head of Blue Creek Valley. Blockage of this paleovalley by dune sand during two and intervals, one shortly before 10 500 yr BP and one in the mid-Holocene, has resulted in a 25 m rise in the regional water table. This made possible the deposition of organic-rich sediment in all three lakes. Although these lakes, especially Swan, would seem ideal places to look for a nearly complete record of Holocene climatic fluctuations, the paleoclimatic record is confounded by the effect dune dams have on the water table. InSwan Lake, the abrupt conversion from marsh to lacustrine deposition3300 years ago does not simply record the change to a wetter regional climate; it reflects the complex local hydrologic changes surrounding the emplacement and sealing of dune dams, as well as regional, climate. [ABSTRACT FROM AUTHOR]
- Published
- 1997
- Full Text
- View/download PDF
38. AMS-radiocarbon dating of organic-poor lake sediment, an example from Linnévatnet, Spitsbergen, Svalbard.
- Author
-
Snyder, J.A., Miller, G.H., Werner, A., Jull, A.J.T., and Stafford, T.W.
- Abstract
AMS-radiocarbon dating of specific organic fractions is used to evaluate sources of errors in dating of organic-poor lake sediment from Linnévatnet, a proglacial arctic lake. Dates on un differentiated (bulk) organic matter are much too old because of contamination from detrital coal. Attempts to remove coal from other organic matter were only partially successful, a consequence of the wide grain-size distribution of the coal. Even if coal contamination is fully removed, the bulk of the remaining organic matter is of aquatic origin and is unsuitable for 14C dating because the lake waters are depleted in 14 C due to dissolution of carbonate minerals. Terrestrial plant macrofossils provide the only reliable material to date the lake sediment; however, this material is present in sufficient quantity for AMS-radiocarbon dating only in cores proximal to the main inlet streams. Paired dates on terrestrial plants and aquatic insects from the same core level and paired dates on modern aquatic and terrestrial vegetation indicate differences in carbon reservoir activities of 1000 and 3000 years. In hard-water lakes, coring is recommended in inlet-proximal areas where inwashed terrestrial vegetation is most concen trated. Chronologies established in proximal cores can be transferred to central-basin cores using litho or chemo-stratigraphic indices. [ABSTRACT FROM PUBLISHER]
- Published
- 1994
- Full Text
- View/download PDF
39. Postglacial changes in chironomid communities and inferred climate near treeline at Mount Stoyoma, Cascade Mountains, southwestern British Columbia, Canada
- Author
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Smith, Michael J., Pellatt, Marlow G., Walker, Ian R., and Mathewes, Rolf W.
- Published
- 1998
- Full Text
- View/download PDF
40. Prediction of Holocene Mercury Accumulation Trends by Combining Palynological and Geochemical Records of Lake Sediments (Black Forest, Germany).
- Author
-
Schütze, Martin, Pérez-Rodríguez, Marta, Biester, Harald, Tserendorj, Gegeensuvd, and Rösch, Manfred
- Subjects
MERCURY ,HOLOCENE paleobotany ,LANDSCAPES - Abstract
Forest vegetation plays a key role in the cycling of mercury (Hg) and organic matter (OM) in terrestrial ecosystems. Litterfall has been indicated as the major transport vector of atmospheric Hg to forest soils, which is eventually transported and stored in the sediments of forest lakes. Hence, it is important to understand how changes in forest vegetation affect Hg in soil and its biogeochemical cycling in lake systems. We investigated the pollen records and the geochemical compositions of sediments from two lakes (Schurmsee and Glaswaldsee) in the Black Forest (Germany) to evaluate whether long-term shifts in forest vegetation induced by climate or land use influenced Hg accumulation in the lakes. We were particularly interested to determine whether coniferous forests were associated with a larger export of Hg to aquatic systems than deciduous forests. Principal components analysis followed by principal component regression enabled us to describe the evolution of the weight of the latent processes determining the accumulation of Hg over time. Our results emphasize that the in-lake uptake of Hg during warm climate periods, soil erosion after deforestation and emissions from mining and other human activities triggered changes in Hg accumulation during the Holocene stronger than the changes caused by forest vegetation alone. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
41. Radioisotopic evidence of perturbations of recent sedimentary record in lakes: a word of caution for climate studies
- Author
-
Daniel Gilbert Span, Jean-Luc Loizeau, and Janusz Dominik
- Subjects
Atmospheric Science ,Climate change ,Perturbation (astronomy) ,Sediment ,Variable thickness ,Archive ,Perturbation ,Lake sediment ,Climatology ,ddc:550 ,Radionuclide ,Sedimentary rock ,Geology ,Holocene - Abstract
The rate of climatic change estimated from the gradient of signals recorded in lake sediments may be erroneous if post-depositional perturbations are overlooked. A smear out of a pulse signal, over a variable thickness of core section, due to physical or biological mixing, is a well known phenomena. Much less attention is paid to a possible overestimation of the rate of change when a part of record is missing due to an erosion event. In this paper we show a few examples of recent lake sediment perturbations and the resulting distortions in the time scale, as documented by short-lived radionuclides.
- Published
- 1992
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