Siga este link para ver outros tipos de publicações sobre o tema: Paleoenvironmental changes reconstruction.
Artigos de revistas sobre o tema "Paleoenvironmental changes reconstruction"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores artigos de revistas para estudos sobre o assunto "Paleoenvironmental changes reconstruction".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja os artigos de revistas das mais diversas áreas científicas e compile uma bibliografia correta.
1
Dowsett, Harry, Aisling Dolan, David Rowley, Robert Moucha, Alessandro M. Forte, Jerry X. Mitrovica, Matthew Pound et al. "The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction". Climate of the Past 12, n.º 7 (13 de julho de 2016): 1519–38. http://dx.doi.org/10.5194/cp-12-1519-2016.
Texto completo da fonteResumo:
Abstract. The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian ( ∼ 3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.
2
Liu, Bing, Robert K. Booth, Jaime Escobar, Zhiqiang Wei, Broxton W. Bird, Andres Pardo, Jason H. Curtis e Jun Ouyang. "Ecology and paleoenvironmental application of testate amoebae in peatlands of the high-elevation Colombian páramo". Quaternary Research 92, n.º 1 (18 de fevereiro de 2019): 14–32. http://dx.doi.org/10.1017/qua.2018.143.
Texto completo da fonteResumo:
AbstractWe investigated the ecology and paleoecology of testate amoebae in peatlands of the Colombian páramo to assess the use of testate amoebae as paleoenvironmental indicators. Objectives were to (1) identify environmental controls on testate amoebae, (2) develop transfer functions for paleoenvironmental inference, and (3) examine testate amoebae in a Holocene peat core and compare our findings with other proxy records. Results from 96 modern samples indicate that testate amoebae are sensitive to pH and surface moisture, and cross-validation of transfer functions indicates potential for paleoenvironmental applications. Testate amoebae from the Triunfo Peatland in the Central Cordillera provided a proxy record of pH and water-table depth for the late Holocene, and inferred changes were correlated with peat C/N measurements during most of the record. Comparison with a lake-level reconstruction suggests that at least the major testate amoeba–inferred changes were driven by climate. Our work indicates that testate amoebae are useful paleoenvironmental indicators in high-elevation tropical peatlands.
3
Bazarova, V. B., N. G. Razjigaeva, T. A. Grebennikova, L. A. Ganzey, L. M. Mokhova, A. M. Korotky e L. D. Sulerzhitsky. "14C Dating of Late Pleistocene–Holocene Events on Kunashir Island, Kuril Islands". Radiocarbon 40, n.º 2 (1997): 775–80. http://dx.doi.org/10.1017/s0033822200018725.
Texto completo da fonteResumo:
Kunashir Island is a very important site for paleoenvironmental reconstructions. Until recently, very little information on Quaternary deposits was available. We studied the environmental evolution of this oceanic island under the influence of geomorphological processes, volcanism and strong marine currents. This paper presents new data that allow a detailed reconstruction of the environmental development of Kunashir Island during the Late Pleistocene–Holocene, based on ca. 80 radiocarbon dates and diatom, pollen and sedimentological data. The vegetation development reflects climate changes and warm/cold current migrations.
4
Gao, Youhong, Zhuolun Li, Nai’ang Wang e Ruolan Li. "Controlling factors and the paleoenvironmental significance of chemical elements in Holocene calcareous root tubes in the Alashan Desert, Northwest China". Quaternary Research 91, n.º 1 (10 de outubro de 2018): 149–62. http://dx.doi.org/10.1017/qua.2018.80.
Texto completo da fonteResumo:
AbstractIn the hinterland of the desert, valuable archives of paleoenvironmental evolution are scarce. Calcareous root tubes (CRTs) have a strong potential for reconstructing paleoenvironmental conditions. It is still unclear, however, whether chemical elements in the CRTs can provide insights into paleoenvironmental conditions. In this study, the major- and trace-element composition of 32 CRT samples from the Alashan Desert were analyzed by X-ray fluorescence spectrometry. Results showed that the elemental composition and content change were controlled by the parent material and climatic conditions at the time of CRT formation. Ca, Mg, and Sr were significantly affected by climate, whereas the enrichment of P is likely related to the growth of plants. Higher (lower) Mg/Ca and Sr/Ca ratios corresponded to higher (lower) effective moisture and a higher (lower) Mg/Sr ratio indicated a higher (lower) temperature during the middle Holocene (8–5 cal ka BP). The reconstruction results for effective moisture were consistent with those in the Asian monsoon margin of northwestern China, which were caused by higher monsoon precipitation and lower evaporation. Therefore, chemical elements in the CRTs can reflect changes in paleo-effective moisture and paleotemperature at a millennial resolution in this area.
5
Stamatis, Dionysios, Alexandros Emmanouilidis, Alessia Masi, Adam Izdebski e Pavlos Avramidis. "Holocene Hydroclimatic Changes in Northern Peloponnese (Greece) Inferred from the Multiproxy Record of Lake Lousoi". Water 14, n.º 4 (18 de fevereiro de 2022): 641. http://dx.doi.org/10.3390/w14040641.
Texto completo da fonteResumo:
This research presents the paleoenvironmental evolution of a drained lake at the Lousoi plateau (northern Peloponnese), for the last 10,000 years, through the study of a 7 m depth core. Analyses conducted on the core include grain size, TOC, TN, pH, EC, total carbonates (%), magnetic susceptibility measurements, XRF analysis, and radiocarbon dating. Our paleoenvironmental reconstruction was based on geochemical proxies’ distribution in the core, combined with sediment physical and textural characteristics and later comparison between additional lacustrine archives from northern Peloponnese. From 10,900 to 7700 cal BP lacustrine, organic-rich deposits were recognized, reflecting increased lake water levels. Wet climatic conditions seem to have prevailed during this phase, interrupted by a dry pulse at 9400 cal BP. Transition to more shallow waters was marked at 8200 cal BP due to increased sediment deposition in the lake, with the environmental status shifting to a more oxygenated phase. Overall, wet conditions prevailed in this period and are in good agreement with regional records. In the Late Holocene period, the lake seems to have been highly affected by pedogenic processes, and thus, it was difficult to distinguish paleoclimatic/paleoenvironmental signals.
6
Cavaliere, Marco, Vittoria Scipioni, Fabio Francescangeli, Luciana Ferraro e Fabrizio Frontalini. "Paleoenvironmental Changes in the Gulf of Gaeta (Central Tyrrhenian Sea, Italy): A Perspective from Benthic Foraminifera after Dam Construction". Water 15, n.º 4 (20 de fevereiro de 2023): 815. http://dx.doi.org/10.3390/w15040815.
Texto completo da fonteResumo:
A 300-year paleoenvironmental reconstruction using benthic foraminifera in the Gulf of Gaeta (central Tyrrhenian Sea, Italy) is here presented. The Gulf of Gaeta dynamics are strongly influenced by the fluvial input, particularly the Volturno River and human activities. The sedimentary archive reveals a strong relation between the variations in the composition of the benthic foraminiferal assemblages and human interventions in the Volturno coastal area. According to the statistical analysis, three main temporal phases are identified and supported by the variations in the enhanced benthic foraminifera oxygen index (EBFOI) values over time. We hypothesize that the main environmental modifications might be ascribed to the construction of two dams, Sorgente Capo Volturno (1909–1916) and Ponte Annibale (1953–1958). The dams have probably altered the supply of sediments causing a physical stress related to the variations in grain-size, the organic matter and the oxygen availability. This temporal reconstruction further supports the ability of foraminifera to register paleoenvironmental changes induced by human activities such as the modification of the physical environment within the sedimentary record.
7
Margielewski, Włodzimierz. "Landslide Fens as a Sensitive Indicator of Paleoenvironmental Changes Since the Late Glacial: A Case Study of the Polish Western Carpathians". Radiocarbon 60, n.º 4 (27 de julho de 2018): 1199–213. http://dx.doi.org/10.1017/rdc.2018.68.
Texto completo da fonteResumo:
AbstractIn the sequences of landslide fen (mire) deposits of the Polish Western Carpathians, Late Glacial-Holocene paleoenvironmental changes were recorded. Downpours and/or continuous rains cyclically repeated during phases of climate humidity growth, causing supplies of mineral material to the minerogenic mires. In effect, illuvial or mineral horizons were formed in landslide fen deposits, as well as mineral covers overly fens in some sites. Sedimentological records reflect various, overlapping factors, as climatic changes, human activity (e.g. accelerating erosion), as well the specificity of the sedimentary environment in each studied landslide fens. The reconstruction and interpretation of the paleoenvironmental changes recorded in landslide fen sediments must be supported by multiproxy analysis of the sequences using pollen, lithological (loss on ignition, grain size and petrography) analyses of samples accurately dated by numerous radiocarbon (14C) dates.
8
Campeau, Stéphane, Arnaud Héquette e Reinhard Pienitz. "Late Holocene diatom biostratigraphy and sea-level changes in the southeastern Beaufort Sea". Canadian Journal of Earth Sciences 37, n.º 1 (1 de abril de 2000): 63–80. http://dx.doi.org/10.1139/e99-107.
Texto completo da fonteResumo:
Late Holocene sediments from the Atkinson Point area were analysed to provide quantitative reconstructions of recent sea-level changes in the southeastern Beaufort Sea. The succession of diatom assemblages in five cores revealed paleoenvironmental changes induced by the transgression of the Beaufort Sea during successive periods of lacustrine conditions, breaching and flooding of thermokarst lakes by the sea, and the landward migration of sandy spits. Based on radiocarbon dates and quantitative paleodepth determinations, a relative sea-level curve for the late Holocene has been developed. Despite a loss of temporal precision due to old carbon contamination, an envelope of sea-level change has been defined for the last 2 ka BP, suggesting a sea-level rise in the order of 1.1 mm a-1 for the last millennium. This paper presents the first sea-level reconstruction inferred from a diatom-based transfer function. It represents an improvement over traditional methods which were limited to qualitative estimates of past sea levels.
9
Machado, Maria J., Alfredo Pérez-González e Gerardo Benito. "Paleoenvironmental Changes during the Last 4000 yr in the Tigray, Northern Ethiopia". Quaternary Research 49, n.º 3 (maio de 1998): 312–21. http://dx.doi.org/10.1006/qres.1998.1965.
Texto completo da fonteResumo:
In the Tigray region at the northern Ethiopian Highlands, paleoenvironmental reconstruction based on several infilled valley deposit sequences suggests that the past 4000 yr comprised three major wetter periods (ca. 4000–3500 yr B.P., 2500–1500 yr B.P., and 1000–960 yr B.P.), during which soils were formed, and two degradation episodes (ca. 3500–2500 yr B.P. and 1500–1000 yr B.P.), during which there was an increase of sediment yield from the slopes into the valleys. For the past 1000 yr, and in particular since the early 17th century, stratigraphic records together with historic chronicles suggest increasing aridity. Although difficulties arise in distinguishing between natural and human impacts, particularly in a region with a long established agricultural background, stratigraphical and proxy paleoclimatic data have indicated climate as the main controlling factor responsible for the environmental changes in the Tigray.
10
Adams, Jennifer K., e Sarah A. Finkelstein. "Watershed-scale reconstruction of middle and late Holocene paleoenvironmental changes on Melville Peninsula, Nunavut, Canada". Quaternary Science Reviews 29, n.º 17-18 (agosto de 2010): 2302–14. http://dx.doi.org/10.1016/j.quascirev.2010.05.033.
Texto completo da fonte
11
Khadraoui, Afef, Chahira Zaïbi, Pierre Carbonel, Jérôme Bonnin e Fekri Kamoun. "Ostracods and mollusks in northern Sfax coast: reconstruction of Holocene paleoenvironmental changes and associated forcing". Geo-Marine Letters 39, n.º 4 (20 de junho de 2019): 313–36. http://dx.doi.org/10.1007/s00367-019-00576-0.
Texto completo da fonte
12
Costa-Casais, Manuela, e Joeri Kaal. "La configuración del paisaje cultural durante la Alta Edad Media (siglos V-XI): cambios ambientales y actividad antrópica en el noroeste de la Península Ibérica". Estudos do Quaternário / Quaternary Studies, n.º 12 (21 de julho de 2015): 1–13. http://dx.doi.org/10.30893/eq.v0i12.100.
Texto completo da fonteResumo:
Este trabajo tiene por objetivo aportar algunos elementos para el debate sobre la reconstrucción paleoambien-tal, desde las disciplinas de las Ciencias de la Tierra, centrándose en el período cultural de la Alta Edad Media (siglos V-XI). El artículo se divide en tres apartados. El primero, introduce conceptos básicos sobre la evolu-ción ambiental: ideas generales sobre la reconstrucción paleoambiental y un breve comentario sobre la activi-dad humana en el contexto de los paleoambientes. El segundo, muestra una aproximación metodológica a la reconstrucción desde diferentes disciplinas de las Ciencias de la Tierra. En el tercero, se comentan algunos resultados recientes obtenidos en el noroeste peninsular utilizando ejemplos de archivos que, en este caso, están representados por suelos coluviales y sus señales geoquímicas, analizando los procesos naturales y otros inducidos por la actividad antrópica, con la finalidad de ilustrar los conceptos discutidos en la primera parte. A modo de conclusión, el artículo se cierra con unas pinceladas sobre el paisaje de la Alta Edad Media en el Noroeste Peninsular, a partir de la interpretación y reconstrucción de los datos obtenidos.
The configuration of the cultural landscape during the early Middle Ages (5th-11th centuries): Environ-mental changes and human activity in the northwest of the Iberian Peninsula - This paper aims to promote the discussion of some elements relating to paleoenvironmental reconstruction, from the point of view of the Earth Sciences, focusing on the cultural period of the early Middle Ages (5th-11th centuries). The article is divided into three sections. In the first, the basic concepts of environmental evolution are introduced, such as the general ideas of paleoenvironmental reconstruction and a brief commentary on human activity in the context of paleoenvironments. The second section demonstrates a methodological ap-proach to reconstruction from the point of view of different disciplines of Earth Sciences. In the third section, recent results obtained in the northwest of the Iberian Peninsula are commented on, making use of samples of colluvial soils and their geochemical signals obtained from environmental archives. An analysis is made of both natural processes and those caused by human activity, in order to illustrate the concepts discussed in the first part. The article concludes with some comments on the landscape of the early Middle Ages in the north-west of the Peninsula, based on the interpretation and reconstruction of the data obtained.
13
MONTES DE OCA, FERNANDA, MARCELA S. TONELLO, JULIETA MASSAFERRO, M. SOFIA PLASTANI e CECILIA LAPRIDA. "THE CHIRONOMIDS (DIPTERA: CHIRONOMIDAE) OF SHALLOW LAKES OF THE HUMID PAMPA REGION, ARGENTINA: AN APPROACH TO PALEOPRODUCTIVITY RECONSTRUCTION". PALAIOS 35, n.º 4 (16 de abril de 2020): 191–200. http://dx.doi.org/10.2110/palo.2019.071.
Texto completo da fonteResumo:
ABSTRACT The Humid Pampa, center-east of Argentina, is the most important socio-economical area of the country. Several shallow lakes have been the focus of many studies due to the significant changes in their trophic status related to human activities and to global warming recorded since the beginning of the twentieth century. Although chironomids have been used extensively in paleoclimatic and paleoenvironmental research, they are rarely used for paleoenvironmental reconstructions of the Pampean shallow lakes. The aim of this paper is to contribute to the knowledge of the chironmids' community composition and distribution in the Pampa region, and to relate their distribution to selected climatic and limnological variables. The ultimate goal is to retrieve new ecological information for future paleoenvironmental and paleoclimate reconstructions by using chironomid-based inference models. In this study, chironomids head capsules were collected from surface sediments from 17 shallow lakes of the Humid Pampa. Our analyses indicate that the chironomid assemblages reflect the decreasing NE-SW rainfall gradient of the region as well as the land use intensity, which in turn affects the aquatic ecosystems, in terms of lake productivity. Some chironomids are associated with brackish conditions (e.g., Chironomus, Ablabesmyia, Tanytarsini D2). Additionally the occurrence of assemblages of detritivore taxa such as Goeldochironomus, Chironomus, Polypedilum, and Dicrotendipes reflect the natural eutrophic state of Pampean shallow lakes, whereas assemblages mostly dominated by Coelotanypus, Procladius, and Chironomus are indicative of hypertrophic conditions, which are usually the result of human activity. This is the first study of chironomids from surface sediments from the central temperate plains of Argentina, and our records extend the ecological information of the Diptera in temperate areas. Although more studies are necessary to fully understand the main factors determining the chironomid fauna distribution in the Pampa region, we conclude that chironomids are potentially good proxies for paleoproductivity and salinity reconstructions of Pampean shallow lakes.
14
Gustiantini, Luli, Kresna Tri Dewi, Anne Muller e Praptisih Praptisih. "PALEOENVIRONMENTAL RECONSTRUCTION FROM BENTHIC FORAMINIFERAL ASSEMBLAGES OF EARLY HOLOCENE, SHALLOW MARINE DEPOSITS IN GOMBONG, CENTRAL JAVA". BULLETIN OF THE MARINE GEOLOGY 22, n.º 1 (15 de fevereiro de 2016): 16. http://dx.doi.org/10.32693/bomg.22.1.2007.2.
Texto completo da fonteResumo:
A 30m-long sediment core covering the Holocene period was taken from the area of Gombong in the southern part of Central Java. The sediments were deposited in a shallow marine to lagoonal environment that was confirmed by the dominance of Ammonia beccarii along the core intervals. In addition, the species Quinqueloculina poeyana, Miliolinella lakemacquariensis, and Miliolinella subrotunda were also found in the sediments that are typical of normal shallow marine conditions. The decrease and increase in the abundance of these species throughout the core is an expression of sea level change in the area, which results the environmental changes. Low sea level is expressed by the dominance of Ammonia beccarii, and the low abundances or absence of the other three species. In contrast, high sea level stands are reflected by the presence of all four species. The high sea level would imply favorable conditions for benthic foraminifera because it would result in normal shallow marine conditions in the area. Finally, from this benthic assemblages study, it can be assumed that the environmental transformation from the originally shallow marine environment into land was occurred at level 5.5m depths of the sediment core, when all benthic foraminifera were terminated, including Ammonia beccarii. These new results from the shallow marine deposits in the Gombong area are a new contribution to the understanding of paleoenvironmental change in the region, which in turn is important for understanding sea level change as well as climate change in the region. Keywords: Benthic foraminifera, Holocene, paleoenvironmental changes, sea level changes Southcoast of Central Java Sebuah percontoh sedimen bor sepanjang 30m yang berumur Holosen diambil dari daerah Gombong, bagian selatan Jawa Tengah. Percontoh sedimen diendapkan pada lingkungan laut dangkal –laguna, berdasarkan kelimpahan foraminifera bentik Ammonia beccarii di sepanjang sedimen bor. Selain itu ditemukan juga spesies-spesies Quinqueloculina poeyana, Miliolinella lakemacquariensis, dan Miliolinella subrotunda, yang merupakan penciri lingkungan laut dangkal dengan kondisi normal. Penurunan dan kenaikan dari kelimpahan masing-masing spesies foraminifera bentik di atas, dapat mencerminkan perubahan permukaan air laut daerah studi, yang menghasilkan terjadinya perubahan lingkungan. Penurunan muka air laut dapat dicirikan dengan hadirnya Ammonia beccarii yang sangat dominan, sementara spesies lainnya cenderung berkurang bahkan hampir tidak ada. Sebaliknya ketika muka air laut naik, maka keempat spesies foraminifera tersebut cenderung hadir dengan jumlah yang seimbang satu sama lainnya. Kenaikan muka air laut akan menghasilkan lingkungan laut normal yang merupakan kondisi ideal bagi foraminifera. Akhirnya, dari kajian perubahan kelimpahan foraminifera bentik ini, dapat diperkirakan bahwa pada level kedalaman bor 5,5m, terjadi perubahan lingkungan dari lingkungan laut dangkal-laguna menjadi daratan, yang ditandai dengan musnahnya semua jenis foraminifera bentik, termasuk Ammonia beccarii. HAsil kajian ini merupakan kontribusi baru untuk mempelajari perubahan lingkungan pada lokasi penelitian, terutama penting untuk lebih mengerti mengenai perubahan muka air laut dan perubahan iklim. Keywords: Benthic foraminifera, Holocene, paleoenvironmental changes, sea level changes
15
Kis, Éva. "Reconstruction of Late Neogene paleoenvironmental changes in the area of Pannonhalma (Western Hungary) using granulometric methods". Zeitschrift für Geomorphologie, Supplementary Issues 56, n.º 2 (1 de setembro de 2012): 105–20. http://dx.doi.org/10.1127/0372-8854/2012/s-00093.
Texto completo da fonte
16
Sá, Natália de Paula, Marcelo de Araujo Carvalho e Gabriel da Cunha correia. "Miocene paleoenvironmental changes in the Solimões Basin, western Amazon, Brazil: A reconstruction based on palynofacies analysis". Palaeogeography, Palaeoclimatology, Palaeoecology 537 (janeiro de 2020): 109450. http://dx.doi.org/10.1016/j.palaeo.2019.109450.
Texto completo da fonte
17
Cordova, Carlos E., e William C. Johnson. "An 18 ka to present pollen- and phytolith-based vegetation reconstruction from Hall's Cave, south-central Texas, USA". Quaternary Research 92, n.º 2 (7 de maio de 2019): 497–518. http://dx.doi.org/10.1017/qua.2019.17.
Texto completo da fonteResumo:
AbstractPollen, spores, phytoliths, and microscopic charcoal from a sedimentary column in Hall's Cave, south-central Texas, provide information for local and regional vegetation change during the last deglaciation and the Holocene in the context of broader regional and global climatic changes. The combination of paleoenvironmental proxy data from the cave indicates that between about 18,000 and 16,500 cal yr BP the cave area was dominated by an open plant community consisting of herbaceous vegetation, dominated by C3 grasses, and scattered trees, primarily Quercus and Pinus species. After about 16,500 cal yr BP, the arboreal component fluctuated, attaining a peak between 14,000 and 13,000 cal yr BP with relatively equal proportions of C3 and C4 grasses, including a sizable proportion of Panicoideae grasses. The Younger Dryas is marked by a conspicuous decrease in arboreal pollen with an apparent increase of C4 grasses toward its termination. Early Holocene recovery of arboreal vegetation is followed by a drying trend marked by the increasing dominance of C4 drought-tolerant Chloridoideae grasses. Increasing human use of the cave in middle to late Holocene times creates noise in the climatic significance of pollen, phytolith, and other proxies, a factor to consider when interpreting paleoenvironmental proxies in other cave sedimentary records.
18
Kotthoff, Ulrich, Jeroen Groeneveld, Jeanine L. Ash, Anne-Sophie Fanget, Nadine Quintana Krupinski, Odile Peyron, Anna Stepanova et al. "Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)". Biogeosciences 14, n.º 23 (12 de dezembro de 2017): 5607–32. http://dx.doi.org/10.5194/bg-14-5607-2017.
Texto completo da fonteResumo:
Abstract. Sediment records recovered from the Baltic Sea during Integrated Ocean Drilling Program Expedition 347 provide a unique opportunity to study paleoenvironmental and climate change in central and northern Europe. Such studies contribute to a better understanding of how environmental parameters change in continental shelf seas and enclosed basins. Here we present a multi-proxy-based reconstruction of paleotemperature (both marine and terrestrial), paleosalinity, and paleoecosystem changes from the Little Belt (Site M0059) over the past ∼ 8000 years and evaluate the applicability of inorganic- and organic-based proxies in this particular setting. All salinity proxies (diatoms, aquatic palynomorphs, ostracods, diol index) show that lacustrine conditions occurred in the Little Belt until ∼ 7400 cal yr BP. A connection to the Kattegat at this time can thus be excluded, but a direct connection to the Baltic Proper may have existed. The transition to the brackish–marine conditions of the Littorina Sea stage (more saline and warmer) occurred within ∼ 200 years when the connection to the Kattegat became established after ∼ 7400 cal yr BP. The different salinity proxies used here generally show similar trends in relative changes in salinity, but often do not allow quantitative estimates of salinity. The reconstruction of water temperatures is associated with particularly large uncertainties and variations in absolute values by up to 8 °C for bottom waters and up to 16 °C for surface waters. Concerning the reconstruction of temperature using foraminiferal Mg / Ca ratios, contamination by authigenic coatings in the deeper intervals may have led to an overestimation of temperatures. Differences in results based on the lipid paleothermometers (long chain diol index and TEXL86) can partly be explained by the application of modern-day proxy calibrations to intervals that experienced significant changes in depositional settings: in the case of our study, the change from freshwater to marine conditions. Our study shows that particular caution has to be taken when applying and interpreting proxies in coastal environments and marginal seas, where water mass conditions can experience more rapid and larger changes than in open ocean settings. Approaches using a multitude of independent proxies may thus allow a more robust paleoenvironmental assessment.
19
Abad, Manuel, Marta Arroyo, Francisco Ruiz, María Luz González-Regalado, Rodríguez Vidal Rodríguez Vidal, Luis Miguel Cáceres, Tatiana Izquierdo et al. "Miocene-Holocene paleoenvironmental changes in the Tinto River estuary (SW Spain) evidenced by sedimentology, geochemistry and fauna". Carnets de géologie (Notebooks on geology) 22, n.º 19 (25 de dezembro de 2022): 825–45. http://dx.doi.org/10.2110/carnets.2022.2219.
Texto completo da fonteResumo:
This paper investigates the paleoenvironmental evolution of a long core extracted in a small cove located in the Tinto-Odiel estuary (SW Spain). The inferred reconstruction is supported by sedimentological, geochemical, paleontological data and dating. Seven phases have been identified, with the transit from Late Neogene marine environments to a subrecent freshwater pond and a final anthropic filling. On the basis of these data, this area was flooded during the maximum of the MIS-1 transgression (6.5-5.2 cal. kyr BP), with the temporary presence of a subtidal channel with phanerogam meadows. During this evolution, three geochemical peaks have been detected, which correspond to 1) the first evidence of mining activities (~4.5 cal. kyr BP), 2) an interval of intensive mining (1850-1960) and 3) an industrial period (1966-1985), affected by the dumping of highly polluting waste into this estuary.
20
Kuroyanagi, Azumi, Hodaka Kawahata, Hisashi Narita, Ken'ichi Ohkushi e Takafumi Aramaki. "Reconstruction of paleoenvironmental changes based on the planktonic foraminiferal assemblages off Shimokita (Japan) in the northwestern North Pacific". Global and Planetary Change 53, n.º 1-2 (agosto de 2006): 92–107. http://dx.doi.org/10.1016/j.gloplacha.2006.01.015.
Texto completo da fonte
21
Markgraf, Vera. "Paleoenvironmental Changes at the Northern Limit of the Subantarctic Nothofagus Forest, lat 37°S, Argentina". Quaternary Research 28, n.º 1 (julho de 1987): 119–29. http://dx.doi.org/10.1016/0033-5894(87)90037-8.
Texto completo da fonteResumo:
AbstractPaleoenvironmental changes dating back to before 10,000 yr B.P. at the northernmost occurrences of Nothofagus forests in Argentina at about latitude 37°S permit the reconstruction of past changes in the intensity of the winter rains, related to the southern westerlies that appear to determine the forest boundary. The paleoenvironmental interpretation is based on changes in the proportions of different Nothofagus species and changes in the ratio betwen forest and steppe taxa. The relatively most diverse and dense Nothofagus forest developed only during the last 4500 yr, prior to human impact during the last 300 yr. Before the middle Holocene, climatic conditions must have been different from the modern ones, with less overall precipitation judging from the overall lower amount of tree pollen and the reduction to primarily Nothfagus pumilio. An interval dated to older than 10,000 yr B.P. is characterized by co-occurrence of Prumnopitys andina, Nothofagus pumilio, and shrub-steppe taxa. Prumnopitys andina is known today only from scattered upper montane forest sites in Chile between 36° and 43°S lat and its ecological requirements are essentially unknown. The taxa combination, however, suggests that late-glacial climate must have been drier, and probably cooler than today. This implies that the winter rains and, consequently, the seasonal shift of the westerly circulation was reduced during the late Pleistocene and did not reach modern levels before 8500 yr B.P.
22
Pierre, Catherine, Antonio Caruso, Marie-Madeleine Blanc-Valleron, Jean Marie Rouchy e Fabienne Orzsag-Sperber. "Reconstruction of the paleoenvironmental changes around the Miocene–Pliocene boundary along a West–East transect across the Mediterranean". Sedimentary Geology 188-189 (junho de 2006): 319–40. http://dx.doi.org/10.1016/j.sedgeo.2006.03.011.
Texto completo da fonte
23
Farouk, Sherif, Mohamed A. Khalifa, Mohamed M. Abu El-Hassan, Cesare A. Papazzoni, Fabrizio Frontalini, Rodolfo Coccioni e Amr S. Zaky. "Upper Paleocene to lower Eocene microfacies, biostratigraphy, and paleoenvironmental reconstruction in the northern Farafra Oasis, Western Desert (Egypt)". Micropaleontology 65, n.º 5 (2019): 381–406. http://dx.doi.org/10.47894/mpal.65.5.01.
Texto completo da fonteResumo:
Three Paleocene-Eocene (P-E) stratigraphic transect sections namely, from the north to south, Ain Maqfi, Farafra-Ain Dalla road, and El-Quess Abu Said in the northern Farafra Oasis,Western Desert (Egypt) are described and interpreted based upon field observations, microfacies analysis, chronostratigraphy and foraminiferal paleobathymetry, to detect the effect of the Syrian Arc Fold System (SAFS) on the lateral and vertical facies changes, various stratigraphic breaks and to reconstruct the depositional paleoenvironments. Lithostratigraphically, the P-E successions are composed of the upper part of the Dakhla Formation, Tarawan Chalk and Esna Shale Formation. Vertical and lateral facies changes are noted between tectonic paleo-highs and paleo-lows in the Farafra Oasis. Eight microfacies types are recognized. The larger benthic and planktonic foraminiferal zones are here used to correlate the shallow and deeper facies. Two larger benthic (SBZ4 and SBZ6), six planktonic foraminiferal (P4–E4) and one calcareous nannofossil (NP9b) biozones are identified. The recorded basal Eocene Dababiya Quarry Member (DQM) within the Esna Shale Formation in the central Farafra Oasis is represented by units 4 and 5 of the DQMat its GSSPwith a neritic facies types. Towards the northern part of the Farafra Oasis, the P-E interval occurs within the base of the Maqfi Limestone Member that contains the larger benthic foraminiferal SBZ6 Zone and is correlated with the DQM.Amajor sea-level fall near the upper part of P5 Zone, followed by a prominent sea-level risewith a minor hiatus across the P-E interval in the Farafra Oasis reflects the complex interplay between sea level changes and tectonic signatures. Two inferred paleoenvironments, namely inner neritic and mid-outer neritic shelf have been identified.
24
Michczyńska, Danuta J., Adam Michczyński e Anna Pazdur. "Frequency Distribution of Radiocarbon Dates as a Tool for Reconstructing Environmental Changes". Radiocarbon 49, n.º 2 (2007): 799–806. http://dx.doi.org/10.1017/s0033822200042673.
Texto completo da fonteResumo:
Large sets of radiocarbon dates of 1019 peat, 155 speleothem, and 100 tufa samples, as well as dates of 330 fluvial samples, were investigated in order to estimate environmental variability during the last 16,000 calendar years in Poland. All 14C dating was carried out in the Gliwice Radiocarbon Laboratory, and results are stored in the RoS database. Probability density functions (PDFs) were created by summing up (on the calendar timescale) individual age probability distributions of all dates for different types of material and for different regions of Poland. We used an updated version of the Gliwice Radiocarbon Laboratory calibration program GdCALIB. The 14C dates were calibrated using the IntCal04 calibration curve (Reimer et al. 2004), and results were compared with other paleoenvironmental records. The authors conclude that analyzing PDFs of different types of sediments can be helpful in the qualitative reconstruction of the past environment. The PDF for peat samples primarily reflects paleohydrological conditions; the PDFs for speleothem and tufa samples reflect changes in temperature and humidity, while analysis of the PDF created for fluvial data is in a general agreement with the PDFs constructed for peat samples.
25
Andreev, A. A., E. Morozova, G. Fedorov, L. Schirrmeister, A. A. Bobrov, F. Kienast e G. Schwamborn. "Vegetation history of Central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater". Climate of the Past Discussions 8, n.º 2 (20 de abril de 2012): 1409–41. http://dx.doi.org/10.5194/cpd-8-1409-2012.
Texto completo da fonteResumo:
Abstract. Frozen sediments from three cores bored in permafrost surrounding of the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils, and rhizopods. The palynological study of the cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, permafrost records better reflect local environmental changes, thus, allowing more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated in the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significant climate deterioration. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The founds of larch seeds indicate its local presence around 11 000 cal. yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal. yr BP similar-to-modern plant communities became common in the lake vicinity.
26
Ren, Shaofang, Yiqing Song, Hao Long, Chao Wu, Zhigang Wang, Chengxin Yi, Hui Wang, Limin Zhou e Xiangmin Zheng. "Records of Organic Carbon Isotopic Composition and Its Paleoenvironmental Implications in Shengshan Island Loess Deposition in the East China Sea during the Last Glacial Period". Applied Sciences 12, n.º 11 (4 de junho de 2022): 5724. http://dx.doi.org/10.3390/app12115724.
Texto completo da fonteResumo:
Organic carbon isotopic composition (δ13Corg) in loess deposits is an important indicator of terrestrial paleovegetation, and it has been widely used for paleoenvironmental reconstruction in aeolian sediments around the world. However, little research has been done on the variation and paleoenvironmental implication of δ13Corg from loess deposits on Shengshan Island, East China Sea, during the last glacial period (LG). In this research, we present optically stimulated luminescence (OSL) ages, total organic carbon (TOC) data and δ13Corg records of the loess section at Chenqianshan (CQS) on Shengshan Island. Additionally, to study the effectiveness of δ13Corg in documenting paleoenvironmental changes, magnetic susceptibilities and diffuse reflectance spectra were surveyed. TOC concentration for the CQS loess section ranged from 0.11% to 0.47%, and the δ13Corg composition of the CQS loess section varied between −20.80‰ and −24.56‰ during the LG. The average value of C4 abundance was 21.31%. TOC, δ13Corg, χfd, and Hm/(Hm + Gt) curves for the CQS loess section showed similar patterns. The results of our study indicated that the vegetation of the CQS loess deposit was mainly C3/C4 mixed vegetation, and C3 vegetation was the most important vegetation. The comparison between the δ13Corg curve for the CQS section and other existing δ13Corg records of the loess sections from central and northern China showed similar trends and their vegetation succession exhibited synchronous change during the LG. Based on a comparison of the δ13Corg record, C4 abundance and χfd of the CQS section and other global geological records, it was concluded that the mutual effects of precipitation and temperature caused the change of paleovegetation in loess deposits on islands in the East China Sea during the LG.
27
Andreev, A. A., E. Morozova, G. Fedorov, L. Schirrmeister, A. A. Bobrov, F. Kienast e G. Schwamborn. "Vegetation history of central Chukotka deduced from permafrost paleoenvironmental records of the El'gygytgyn Impact Crater". Climate of the Past 8, n.º 4 (17 de agosto de 2012): 1287–300. http://dx.doi.org/10.5194/cp-8-1287-2012.
Texto completo da fonteResumo:
Abstract. Frozen sediments from three cores bored in the permafrost surrounding the El'gygytgyn Impact Crater Lake have been studied for pollen, non-pollen palynomorphs, plant macrofossils and rhizopods. The palynological study of these cores contributes to a higher resolution of time intervals presented in a poor temporal resolution in the lacustrine sediments; namely the Allerød and succeeding periods. Moreover, the permafrost records better reflect local environmental changes, allowing a more reliable reconstruction of the local paleoenvironments. The new data confirm that shrub tundra with dwarf birch, shrub alder and willow dominated the lake surroundings during the Allerød warming. Younger Dryas pollen assemblages reflect abrupt changes to grass-sedge-herb dominated environments reflecting significantly drier and cooler climate. Low shrub tundra with dwarf birch and willow dominate the lake vicinity at the onset of the Holocene. The find of larch seeds indicate its local presence around 11 000 cal yr BP and, thus a northward shift of treeline by about 100 km during the early Holocene thermal optimum. Forest tundra with larch and shrub alder stands grew in the area during the early Holocene. After ca. 3500 cal yr BP similar-to-modern plant communities became common in the lake vicinity.
28
Surić, Maša, György Czuppon, Robert Lončarić, Neven Bočić, Nina Lončar, Petra Bajo e Russell N. Drysdale. "Stable Isotope Hydrology of Cave Groundwater and Its Relevance for Speleothem-Based Paleoenvironmental Reconstruction in Croatia". Water 12, n.º 9 (25 de agosto de 2020): 2386. http://dx.doi.org/10.3390/w12092386.
Texto completo da fonteResumo:
Speleothems deposited from cave drip waters retain, in their calcite lattice, isotopic records of past environmental changes. Among other proxies, δ18O is recognized as very useful for this purpose, but its accurate interpretation depends on understanding the relationship between precipitation and drip water δ18O, a relationship controlled by climatic settings. We analyzed water isotope data of 17 caves from different latitudes and altitudes in relatively small but diverse Croatian karst regions in order to distinguish the dominant influences. Drip water δ18O in colder caves generally shows a greater resemblance to the amount-weighted mean of precipitation δ18O compared to warmer sites, where evaporation plays an important role. However, during glacial periods, today’s ‘warm’ sites were cold, changing the cave characteristics and precipitation δ18O transmission patterns. Superimposed on these settings, each cave has site-specific features, such as morphology (descending or ascending passages), altitude and infiltration elevation, (micro) location (rain shadow or seaward orientation), aquifer architecture (responsible for the drip water homogenization) and cave atmosphere (governing equilibrium or kinetic fractionation). This necessitates an individual approach and thorough monitoring for best comprehension.
29
Cahill, Niamh, Andrew C. Kemp, Benjamin P. Horton e Andrew C. Parnell. "A Bayesian hierarchical model for reconstructing relative sea level: from raw data to rates of change". Climate of the Past 12, n.º 2 (29 de fevereiro de 2016): 525–42. http://dx.doi.org/10.5194/cp-12-525-2016.
Texto completo da fonteResumo:
Abstract. We present a Bayesian hierarchical model for reconstructing the continuous and dynamic evolution of relative sea-level (RSL) change with quantified uncertainty. The reconstruction is produced from biological (foraminifera) and geochemical (δ13C) sea-level indicators preserved in dated cores of salt-marsh sediment. Our model is comprised of three modules: (1) a new Bayesian transfer (B-TF) function for the calibration of biological indicators into tidal elevation, which is flexible enough to formally accommodate additional proxies; (2) an existing chronology developed using the Bchron age–depth model, and (3) an existing Errors-In-Variables integrated Gaussian process (EIV-IGP) model for estimating rates of sea-level change. Our approach is illustrated using a case study of Common Era sea-level variability from New Jersey, USA We develop a new B-TF using foraminifera, with and without the additional (δ13C) proxy and compare our results to those from a widely used weighted-averaging transfer function (WA-TF). The formal incorporation of a second proxy into the B-TF model results in smaller vertical uncertainties and improved accuracy for reconstructed RSL. The vertical uncertainty from the multi-proxy B-TF is ∼ 28 % smaller on average compared to the WA-TF. When evaluated against historic tide-gauge measurements, the multi-proxy B-TF most accurately reconstructs the RSL changes observed in the instrumental record (mean square error = 0.003 m2). The Bayesian hierarchical model provides a single, unifying framework for reconstructing and analyzing sea-level change through time. This approach is suitable for reconstructing other paleoenvironmental variables (e.g., temperature) using biological proxies.
30
Cahill, N., A. C. Kemp, B. P. Horton e A. C. Parnell. "A Bayesian hierarchical model for reconstructing relative sea level: from raw data to rates of change". Climate of the Past Discussions 11, n.º 5 (16 de outubro de 2015): 4851–93. http://dx.doi.org/10.5194/cpd-11-4851-2015.
Texto completo da fonteResumo:
Abstract. We present a holistic Bayesian hierarchical model for reconstructing the continuous and dynamic evolution of relative sea-level (RSL) change with fully quantified uncertainty. The reconstruction is produced from biological (foraminifera) and geochemical (δ13C) sea-level indicators preserved in dated cores of salt-marsh sediment. Our model is comprised of three modules: (1) A Bayesian transfer function for the calibration of foraminifera into tidal elevation, which is flexible enough to formally accommodate additional proxies (in this case bulk-sediment δ13C values), (2) A chronology developed from an existing Bchron age-depth model, and (3) An existing errors-in-variables integrated Gaussian process (EIV-IGP) model for estimating rates of sea-level change. We illustrate our approach using a case study of Common Era sea-level variability from New Jersey. USA We develop a new Bayesian transfer function (B-TF), with and without the δ13C proxy and compare our results to those from a widely-used weighted-averaging transfer function (WA-TF). The formal incorporation of a second proxy into the B-TF model results in smaller vertical uncertainties and improved accuracy for reconstructed RSL. The vertical uncertainty from the multi-proxy B-TF is ∼ 28 % smaller on average compared to the WA-TF. When evaluated against historic tide-gauge measurements, the multi-proxy B-TF most accurately reconstructs the RSL changes observed in the instrumental record (MSE = 0.003 m2). The holistic model provides a single, unifying framework for reconstructing and analysing sea level through time. This approach is suitable for reconstructing other paleoenvironmental variables using biological proxies.
31
Piličiauskas, Gytis, Jonas Mažeika, Andrejus Gaidamavičius, Giedrė Vaikutienė, Albertas Bitinas, Žana Skuratovič e Miglė Stančikaitė. "New Archaeological, Paleoenvironmental, and 14C Data from the Šventoji Neolithic Sites, NW Lithuania". Radiocarbon 54, n.º 3-4 (2012): 1017–31. http://dx.doi.org/10.1017/s0033822200047640.
Texto completo da fonteResumo:
Archaeological, geological, and paleoecological investigations supported by radiocarbon dating enabled us to present a reconstruction of chronologically based paleoenvironmental and human activity changes in the Šventoji region, NW Lithuania, during the period 4000–800 cal BC. In addition, we describe the main stages of the Late Glacial and Holocene periods in the area. The Baltic Ice Lake regression was succeeded by a terrestrial period until the Littorina Sea maximal transgression at 5700–5400 cal BC. A marine bay with brackish water was transformed into a freshwater lagoon before the oldest archaeological evidence of human presence, i.e. 4000/3700 cal BC. However, the presence of Cerealia type and Plantago lanceolata pollen dating back to about 4400–4300 cal BC suggests earlier farming activities in the area. Pollen analyses show the minor but continuous role of cereal cultivation after 3250 cal BC. Due to the predominance of the boggy landscape in the immediate vicinity of the Šventoji sites, agricultural fields were situated further away from the sites themselves. Exploitation of remote areas of the freshwater basin by diverse fishing gear was proven by the discovery of a new fishing site, Šventoji 41 (2900–2600 cal BC). This finding together with data of previous research suggest a complex and elaborate coastal economy involving seal hunting and year-round freshwater fishing during the 3rd millennium cal BC. A decline in human activity is seen in the pollen diagram after 1800 cal BC, which could be due to significant environmental changes, including overgrowth of the freshwater lagoon basin with vegetation.
32
Maanan, Mohamed, Pierre Pouzet, Sabine Schmidt e Marc Robin. "Historic Storms Detected in a Changing Environment over Recent Centuries in the Belle Henriette Lagoon". Atmosphere 13, n.º 2 (18 de janeiro de 2022): 151. http://dx.doi.org/10.3390/atmos13020151.
Texto completo da fonteResumo:
This paper explores extreme storms with marine flooding events in historical times. It focuses on the challenges associated with detecting these events with a degree of certainty in a changing environment. The paleoenvironmental changes which turned the Gulf of Pictons into the Belle Henriette lagoon have required the reconstruction of events to be based on cored sediments. This study aims to establish how sedimentological washovers can be detected in a depositional environment that has changed profoundly over recent centuries. The Belle Henriette lagoon site is unique. Despite the profound environmental changes that have taken place, the impact of storms was well preserved in the five cores extracted. Eighteen historical extreme storms with marine floods were detected in the sediment. By cross-referencing with historical archives, thirteen storms were estimated in 1990, 1940, 1896, 1876, 1859, 1838, 1820, 1811, 1751, 1711, 1645, 1469, and 1351. Five older storms dating back to 1090, 1036, 941, 809, and 581 will also be discussed. By conducting a thorough historical review, we can conclude that these extreme storms caused significant damage and had a profound impact on the socioeconomic coastal communities.
33
Liu, Hongye, Yansheng Gu, Zijian Lun, Yangmin Qin e Shenggao Cheng. "Phytolith-inferred transfer function for paleohydrological reconstruction of Dajiuhu peatland, central China". Holocene 28, n.º 10 (2 de julho de 2018): 1623–30. http://dx.doi.org/10.1177/0959683618782590.
Texto completo da fonteResumo:
Depth to water table (DWT, the depth from the water surface to the top of the peat surface) is one of the most important environmental variables related to the habitat types and distribution of vegetation within a subalpine peatland. The distribution of phytolith assemblages and basic environmental data from 43 surface soil samples with significant ecological and hydrological gradients were investigated to generate transfer functions for quantitative reconstruction of paleoenvironmental changes in Dajiuhu peatland, central China. Detrended correspondence analysis (DCA) and redundancy analysis (RDA) were employed to explore the relationship between main environmental variables and phytolith morphotypes and distributions. Our results indicate that the spatial distribution of phytoliths was significantly correlated with the DWT (25% variance), total organic carbon (TOC, 10% variance) and magnetic susceptibility (χ, 7% variance). We established the transfer functions for the significant variables based on modern analogue technique (MAT), weighted averaging techniques (WA) and weighted averaging partial least squares (WA-PLS), and model performance was assessed using bootstrap cross-validation. The high correspondence of the predicted DWT results based on phytolith-environment calibration data with observed data reflects that the phytolith-based WA-PLS is a reliable effective calibration method for the quantitative DWT reconstruction of ombrotrophic (rain-fed) subalpine peatland.
34
Badejo, Adegoke Olugboyega, JongKu Gal, Sang-min Hyun, Hi-Il Yi e Kyung-Hoon Shin. "Reconstruction of paleohydrological and paleoenvironmental changes using organic carbon and biomarker analyses of sediments from the northern East China Sea". Quaternary International 344 (setembro de 2014): 211–23. http://dx.doi.org/10.1016/j.quaint.2014.06.035.
Texto completo da fonte
35
Liu, Bangjun, Mirijam Vrabec, Miloš Markič e Wilhelm Püttmann. "Reconstruction of paleobotanical and paleoenvironmental changes in the Pliocene Velenje Basin, Slovenia, by molecular and stable isotope analysis of lignites". International Journal of Coal Geology 206 (abril de 2019): 31–45. http://dx.doi.org/10.1016/j.coal.2019.03.006.
Texto completo da fonte
36
Alexandre, A., J. Crespin, F. Sylvestre, C. Sonzogni e D. W. Hilbert. "The oxygen isotopic composition of phytoliths from tropical rainforest soils (Queensland, Australia): application of a new paleoenvironmental tool". Climate of the Past Discussions 7, n.º 3 (27 de maio de 2011): 1693–735. http://dx.doi.org/10.5194/cpd-7-1693-2011.
Texto completo da fonteResumo:
Abstract. Variations in the oxygen isotopic composition of precipitation (δ18Oprecipitation) in inter-tropical areas mainly record variations in water sources, amounts of precipitation, and atmospheric temperature and provide information regarding local climate and regional atmospheric circulation changes. On continents, fossil biogenic minerals and speleothems formed in isotopic equilibrium with water can produce continuous δ18O records and are becoming increasingly valuable for reconstructing past climate changes. Here, we explore the efficiency and limitations of using the oxygen isotopic composition of wood phytoliths (δ18Owood phytolith) from tropical rainforest soils as a suitable proxy for atmospheric temperature and δ18Oprecipitation values, under conditions that are assumed to be non-evaporative. Soil phytolith assemblages, that should contain 100s of years of phytolith production, were collected along four altitude, temperature, and precipitation gradients in the Queensland rainforests (Australia). Oxygen isotopic analyses were performed on 1.6 mg phytolith samples, after controlled isotopic exchange (CIE), using the IR Laser-Heating Fluorination Technique. Long-term mean annual precipitation (MAP) and mean annual temperature (MAT) values at the sampled sites were obtained using a regional GIS database. The δ18Oprecipitation values were estimated. The δ18Owood phytolith values from the leeward slopes were scattered but recorded the modern combination of weighted mean annual δ18Oprecipitation values and MAT. The empirical relationship was &Delta18Owood phytolith-precipitation (‰ vs. VSMOW) = −0.4 (±0.2) t (°C) + 46 (±3) (R2 = 0.4, p<0.05; n=12). δ18Oprecipitation estimates were close to estimates for δ18Oforming water when using the temperature-dependant relationships previously described for sedimentary diatoms and natural quartz. However, they were 3 ‰ higher than estimates for δ18Oforming water when using the fractionation relationship obtained for harvested grass phytoliths. The shift may result from estimates uncertainties and/or partial dissolution of soil phytolith assemblages. At this stage, the absence of a uniform temperature-dependant relationship for the different silica-water couples prevents the reconstruction of precise values for δ18Oforming water and temperatures from fossil samples. At the same time, the obtained temperature coefficient of −0.4 (±0.2) ‰/°C is in agreement with the fractionation coefficients previously obtained for harvested grass phytoliths, sedimentary and fresh diatoms, and natural quartz. The consistency supports the efficiency of δ18Owood phytolith signatures in recording relative changes in mean annual δ18Osoil water values (assumed to be equivalent to the weighted mean annual δ18Oprecipitation values in rainforest environments) and MAT, provided these changes were on the order of several ‰ and/or several °C in magnitude. While rainforest dynamics can be revealed by morphological phytolith indices, the δ18O analysis of rainforest phytolith assemblages from continuous sedimentary sequences should simultaneously provide insights into terrestrial climate changes.
37
Erbajeva, M. A., A. A. Shchetnikov, A. Yu Kazansky, G. G. Matasova, F. I. Khenzykhenova, I. A. Filinov, O. D. Ts Namzalova e I. O. Nechaev. "New pleistocene key section Ulan-Zhalga of the Western Transbaikalia". Доклады Академии наук 488, n.º 3 (26 de setembro de 2019): 277–81. http://dx.doi.org/10.31857/s0869-56524883277-281.
Texto completo da fonteResumo:
The currant paper presents the preliminary results of the multidisciplinary study of the new Pleistocene section Ulan-Zhalga (51°29′40.75″ С, 107°20′18.11″ В) discovered in the Western Transbauikalaia in 2017. On the base of the paleontological, paleomagmetic, and lithological data the early, middle and late Pleistocene sediments were recognized in the section. The analysis of the rich small mammal fossils resulted in to trace the paleoenvironmental and climatic changes in the region during the Quaternary. The unique alternation of the 19 faunistic horizons and 11 fossil soils in the whole section, the high correlation of the paleomagnetic and paleontological data allow us to refer the studied section Ulan-Zhalga to addition new late Cenozoic Key section of the south Eastern Siberia. The new geological and paleontological data would be important for paleogeographical reconstruction and biostratigraphic analysis.
38
Jo, Kyoung-nam, Kyung Sik Woo, Hai Cheng, Lawrence R. Edwards, Yongjin Wang, Ryeon Kim e Xiuyang Jiang. "Textural and carbon isotopic evidence of monsoonal changes recorded in a composite-type speleothem from Korea since MIS 5a". Quaternary Research 74, n.º 1 (julho de 2010): 100–112. http://dx.doi.org/10.1016/j.yqres.2010.04.005.
Texto completo da fonteResumo:
AbstractTextural and stable isotopic records of a composite-type speleothem from Gwaneum Cave in the eastern part of the Korean peninsula show prominent paleoenvironmental changes since MIS (marine oxygen isotope stage) 5a. Based on 230Th/234U dating, the speleothem experienced growth from 90.9 ± 6.5 ka to 1.2 ± 0.5 ka with several hiatuses. Four growth phases (A, B, C and D) are recognized based on speleothem type and texture. Very irregular and laterally discontinuous growth laminae in Phases B and C indicate that the cave coralloids grew over the stalagmite (Phase A) when the supply of dripping water became limited. Variations within the δ13C time series of Phase A are interpreted as responses to millennial-scale fluctuations of the East Asian monsoon intensity during MIS 5a. The monsoonal interpretation is based on the idea that δ13C values reflect the isotopic composition of soil-derived CO2, which, in turn, should relate to monsoon-driven changes in terrestrial productivity above the cave during the MIS 5a. Our reconstruction reveals that the significant monsoonal changes on the Korean peninsula occurred in conjunction with changes in sea level and/or oceanic circulations during the transition period from MIS 5a to MIS 4.
39
Kasem, Atef M., Mahmoud Faris, Luigi Jovane, Taysir Abdelhamid Ads, Fabrizio Frontalini e Amr S. Zaky. "Biostratigraphy and Paleoenvironmental Reconstruction at the Gebel Nezzazat (Central Sinai, Egypt): A Paleocene Record for the Southern Tethys". Geosciences 12, n.º 2 (20 de fevereiro de 2022): 96. http://dx.doi.org/10.3390/geosciences12020096.
Texto completo da fonteResumo:
The variations in assemblages of calcareous nannofossils are tracked in the Dakhla and Tarawan Formations exposed at Gebel Nezzazat (central Sinai, Egypt). Five calcareous nannofossil biozones, namely NP2/3, NP4, NP5, NP6, and NP7/8 are identified. A distinct marker bed related to the Latest Danian Event (LDE) occurs within the Dakhla Fm. The earliest representative of fasciculiths, Lithoptychius schmitzii, first occurs just below the LDE distinct bed and is followed by the Los of Diantholitha alata, D. mariposa, L. varolii, L. felis, and L. collaris. The abundance of calcareous nannofossils drops within the LDE distinctive bed. The base of Selandian Stage is here approximated at the base of Zone NP5 in concurrence with a sudden drop in the abundance of calcareous nannofossils. No considerable lithological changes are noted across this transition. The absence of subsequent occurrences of L. ulii, L. janii, L. billii, and L. stegostus suggest inconsistent lowest occurrences (Los) of these taxa, insufficient sampling resolution, and/or a hiatus. The base of Thanetian is approximated with the base of Zone NP7/8 in the topmost of Dakhla Fm. No considerable changes in calcareous nannofossil assemblages are associated in correspondence to this transition except the LO of D. mohleri, lowest continuous occurrence (LctO) of Bomolithus megastypus, and the increase in abundance of Heliolithus kleinpellii as well as a sudden drop in abundance within Zone NP7/8. The variations in calcareous nannofossil assemblages at Gebel Nezzazat suggest prevailing warm-water and oligotrophic conditions during the Paleocene and particularly along the Danian Stage that are interrupted by minor fluctuations in paleoclimatic conditions. In particular, the Danian–Selandian transition marks a decrease in warm and oligotrophic conditions that persisted along the Selandian Stage. The Selandian–Thanetian transition shows an increase of warm and oligotrophic conditions prevailed in the Thanetian record. The sudden decrease in abundance of calcareous nannofossils in both the Selandian and Thanetian is likely resulted from an increase in dissolution of carbonates rather than variations in the paleotemperature and/or paleofertility.
40
Carboni, M. Gabriella, Luisa Bergamin, Letizia Di Bella, Daniela Esu, Emanuela Pisegna Cerone, Fabrizio Antonioli e Vladimiro Verrubbi. "Palaeoenvironmental reconstruction of late Quaternary foraminifera and molluscs from the ENEA borehole (Versilian plain, Tuscany, Italy)". Quaternary Research 74, n.º 2 (setembro de 2010): 265–76. http://dx.doi.org/10.1016/j.yqres.2010.07.006.
Texto completo da fonteResumo:
AbstractForaminifera and molluscs from the 90 m deep ENEA borehole (Versilian plain, central Italy) were studied for paleoenvironmental purposes. Palaeontological analyses, integrated with U/Th and radiocarbon data, helped to recognize late Quaternary sea-level changes and supplied results on tectonic mobility of the area. The study highlighted four sedimentary phases. The first phase consists of a shore environment attributed to MIS 7.1. A hiatus corresponding to MIS 6 is hypothesized at the top of this interval. Recognition of the paleo-shoreline of MIS 7.1 at − 72.8 m signifies a vertical displacement due to the extensional tectonics of the Apennine orogenesis. The second phase consists of a transgressive succession with evidence of warm temperatures, which was interpreted as part of the transgression leading to the MIS 5.5 highstand. The third phase includes sub-aerial and lacustrine deposits. Radiocarbon dates and palaeoecological reconstruction led us to attribute this interval to MIS 4, MIS 3 and MIS 2. The fourth phase begins with a lagoon environment attributable to Holocene sea-level rise and ends with marsh episodes, signifying the progradation of the alluvial plain. This reconstruction confirms the hypothesis of tectonic stability for the Versilian area during the Holocene.
41
Avdieienko, Yuliia. "On methodology of palaeogeographical studies of karst cave deposits of Ukraine". Physical Geography and Geomorphology 103-104, n.º 5-6 (2020): 50–56. http://dx.doi.org/10.17721/phgg.2020.5-6.06.
Texto completo da fonteResumo:
New approaches developed within the complex palaeogeographic methodology of cave deposits studies for reconstruction of the past ecological conditions are presented in the paper. The relevance and reliability of results of such studies are shown on the cases from the previous research of cave systems in Ukraine. The methodology based of palynological and lithological (including grain-size analysis) study of terrigenous cave deposits is proposed, and the advantages of their complex application within the multidisciplinary palaeoenvironmental study are proved. The reliability of palaeovegetational reconstructions based on pollen studies of clastic cave deposits is confirmed by the compatibility of their results with those obtained from coeval subaerial deposits. The same patterns were shown by a comparison of pollen from hyaena coprolites in the cave and their enclosing sediments. It has been found that the content of redeposited pollen in the clastic sediments of caves depends on their particle size distribution, sharply increasing in sandy deposits. The grain-size composition of cave deposits also provides information on the genesis of deposits and, thus, indirectly, on paleoenvironmental conditions. Changes in clay, large silt and sand fractions are of main importance for the interpretation of the results. A direct correlation of paleoclimatic signals obtained by the results of pollen and lithological analyses with the indicators of magnetic susceptibility has been established. The use of these paleogeographic methods for studying cave deposits, namely pollen analyses, lithological (in particular, grain-size), palaeontological, petromagnetic, palaeogenetic, radiocarbon and paleomagnetic methods, will be able to control the reliability of the reconstruction by collate them. Multidisciplinary study of the cave deposits has a great potential for reconstructions of the ancient Man environments as deposits of many caves include archaeological horizons of different material cultures from the Early Palaeolithic to the Early Iron Age.
42
May, Jan-Hendrik, Stephen G. Wells, Timothy J. Cohen, Samuel K. Marx, Gerald C. Nanson e Sophie E. Baker. "A soil Chronosequence on Lake Mega-Frome Beach Ridges and its Implications for Late Quaternary Pedogenesis and Paleoenvironmental Conditions in the Drylands of Southern Australia". Quaternary Research 83, n.º 1 (janeiro de 2015): 150–65. http://dx.doi.org/10.1016/j.yqres.2014.11.002.
Texto completo da fonteResumo:
AbstractThe terminal lake systems of central Australia are key sites for the reconstruction of late Quaternary paleoenvironments. Paleoshoreline deposits around these lakes reflect repeated lake filling episodes and such landforms have enabled the establishment of a luminescence-based chronology for filling events in previous studies. Here we present a detailed documentation of the morphology and chemistry of soils developed in four well-preserved beach ridges of late Pleistocene and mid-to-late Holocene age at Lake Callabonna to assess changes in dominant pedogenic processes. All soil profiles contain evidence for the incorporation of eolian-derived material, likely via the formation of desert pavements and vesicular horizons, and limited illuviation due to generally shallow wetting fronts. Even though soil properties in the four studied profiles also provide examples of parent material influence or site-specific processes related to the geomorphic setting, there is an overall trend of increasing enrichment of eolian-derived material since at least ~ 33 ka. Compared to the Holocene profiles, the derived average accumulation rates for the late Pleistocene profiles are significantly lower and may suggest that soils record important regional changes in paleoenvironments and dust dynamics related to shifts in the Southern Hemisphere westerlies.
43
Betancurth Montes, Liliana, e Julio Eduardo Cañón Barriga. "Paleoenvironmental Interpretation of Last Millennium Sediments in the Marriaga Swamp, Atrato Delta, Colombia". Ciencia e Ingeniería Neogranadina 31, n.º 1 (23 de julho de 2021): 9–24. http://dx.doi.org/10.18359/rcin.5071.
Texto completo da fonteResumo:
This paper presents the first paleoenvironmental reconstruction of the last 1,130 a of the Marriaga Swamp in the Atrato River delta in northwestern Colombia. The geochemical analyses of a 220 cm sediment core retrieved from the swamp reveal interesting climatic episodes and sedimentary changes in the last millennium. We split the core into three segments, according to sediment features, organic carbon content (OC), and geological ages. Records show different alternations of humid and dry periods, biological productivity, carbonate precipitation, weathering grade, and high heavy metal concentrations. The segments also concur with the geochemical differences determined by (Zr+Rb)/Sr, Ca/Ti Mn/Fe, OC/Ti, Mg/Ca Ba/Al, Sr/Al, and Ca/Al ratios. The older sequence (between 1,130 ± 90 a and 870 ± 70 a) shows a dry period with intermittent flooding events and high OC production in subareal conditions, followed by a more humid environment between 870 ± 70 a and 530 ± 40 a, with depletion of trace element ratios and OC. The more recent period (530 ± 40 a to present) evinces an environment dominated by the fluvial regime, based on a lower Ca/Al ratio and a rise of OC. The statistical correlations display three main clusters that distinguish among organic-biological productivity, bedrock source components, and heavy metal inputs.
44
Whitlock, Cathy, Patricio I. Moreno e Patrick Bartlein. "Climatic controls of Holocene fire patterns in southern South America". Quaternary Research 68, n.º 1 (julho de 2007): 28–36. http://dx.doi.org/10.1016/j.yqres.2007.01.012.
Texto completo da fonteResumo:
AbstractHolocene fire–climate–vegetation linkages are mostly understood at individual sites by comparing charcoal and pollen records with other paleoenvironmental proxy and model simulations. This scale of reconstruction often obscures detection of large-scale patterns in past fire activity that are related to changes in regional climate and vegetation. A network of 31 charcoal records from southern South America was examined to assess fire history along a transect from subtropic to subantarctic biomes. The charcoal data indicate that fire activity was greater than present at ca. 12,000 cal yr BP and increased further and was widespread at 9500 cal yr BP. Fire activity decreased and became more spatially variable by 6000 cal yr BP, and this trend continued to present. Atmospheric circulation anomalies during recent high-fire years show a southward shift in westerlies, and paleoclimate model simulations and data syntheses suggest that such conditions may have prevailed for millennia in the early Holocene when the pole-to-equator temperature gradients were weaker and annual temperatures were higher than present, in response to orbital-time-scale insolation changes.
45
Di Bella, Letizia, Piero Bellotti, Virgilio Frezza, Luisa Bergamin e Maria Gabriella Carboni. "Benthic foraminiferal assemblages of the imperial harbor of Claudius (Rome): Further paleoenvironmental and geoarcheological evidences". Holocene 21, n.º 8 (18 de julho de 2011): 1245–59. http://dx.doi.org/10.1177/0959683611405239.
Texto completo da fonteResumo:
This paper presents a paleoenvironmental reconstruction of historical development in the area of the ancient harbor of Claudius based on micropaleontological and sedimentological data. Benthic foraminifera are reliable tools for this kind of research because they are sensitive to short-time environmental changes induced by both natural and anthropogenic events. By studying eight sediment cores collected from different sections of the harbor, it was possible to reconstruct a comprehensive picture of the harbor complex. Qualitative and quantitative analysis of foraminiferal associations and sedimentological data, along with radiocarbon dating, were useful to identify three key intervals in the history of the coastal area where the harbor developed. The first interval, located at the bottom of all cores, is characterized by a brackish water environment, corresponding to the formation of the first deltaic cusp of the Tiber River. The second interval is characterized by the harbor activities that developed after a general increase in water depth due to a diversion of the Tiber River mouth. The third interval marks the final phase of harbor activities and the subsequent filling of Claudius’ basin. However, a link with the inner Trajanus’ basin was maintained via the central part of the basin, which remained submerged longer, until the early Middle Ages.
46
Törőcsik, Tünde, Sándor Gulyás, Dávid Molnár, Réka Tapody, Balázs P. Sümegi, Gábor Szilágyi, Mihály Molnár, Gusztáv Jakab, Pál Sümegi e Zsolt Novák. "Probabilistic 14C Age-Depth Models Aiding the Reconstruction of Holocene Paleoenvironmental Evolution of a Marshland from Southern Hungary". Radiocarbon 60, n.º 5 (outubro de 2018): 1301–15. http://dx.doi.org/10.1017/rdc.2018.112.
Texto completo da fonteResumo:
ABSTRACTThis paper presents first chronological results for a Holocene marshland system from the southern part of the Danube-Tisza Interfluve. Radiocarbon (14C) ages were used to build age-depth models relying of probabilistic tools. Four models have been built: a linear one using dates gained via simple calibration, a P_Sequence model, fitting a polynomial function to calibrated dates; a Gamma_Sequence considering priori given and posterior accumulation rates have been constructed. As there was no significant difference between the mean values of individual models all seem suitable for establishing a reliable chronology despite differences in 95% CI ranges. While P_Sequence models underestimated SR, values calculated from the polynomial model were not significantly different from those of the G_Sequence. Based on multiproxy geochemical, sedimentological, paleoecological data the evolution of the system was reconstructed, covering a timespan of ca. 13,000 years starting from 12,000 BC and lasting until 1300 AD. Highest accumulation rates are dated to the Early Middle Ages from the 11th century. Several climate changes could have been identified which are present in other Hungarian and Western European records too, such as the 5b IRD event at ca. 5800 BC, a humid phase around 1600 BC, and a cool humid phase around the 6th century AD.
47
Demory, François, Gilles Conesa, Julien Oudet, Habib Mansouri, Philippe Münch, Jean Borgomano, Nicolas Thouveny, Juliette Lamarche, Franck Gisquet e Lionel Marié. "Magnetostratigraphy and paleoenvironments in shallow-water carbonates: the Oligocene-Miocene sediments of the northern margin of the Liguro-Provençal basin (West Marseille, southeastern France)". Bulletin de la Société Géologique de France 182, n.º 1 (1 de janeiro de 2011): 37–55. http://dx.doi.org/10.2113/gssgfbull.182.1.37.
Texto completo da fonteResumo:
Abstract The present study proposes to estimate the influence of climate, eustatism and local tectonics on the sedimentation of a basin margin at the syn-rift to post-rift transition. For that, paleomagnetic measurements were performed on a marine marly-calcareous sedimentary succession ranging from Upper Oligocene to Lower Miocene and located on the northern margin of the Liguro-Provençal basin. The magnetostratigraphic record is correlated to the reference geomagnetic polarity scale [ATNTS04, Lourens et al. 2004] with the help of biostratigraphy based on calcareous nannofossils and planctonic foraminifers [Oudet et al., 2010]. The resulting age model shows that the 100 m-thick sedimentary succession covers a time span of 5 m.y. from the Late Chattian to the Early Burdigalian. Despite several exposure surfaces and a change in the sedimentation rate, no significant hiatus of sedimentation is documented. In addition, we also estimate the paleoenvironmental evolution through the sedimentary succession. Comparing the dated paleoenvironmental reconstruction with global δ18O and sea level curves [Miller et al., 2005], we show that the Carry-le-Rouet succession is an excellent paleoclimatic archive. Indeed, coral reefs developed at the glacial-interglacial stage transition marking the end of the Oligocene. In addition, the most diversified coral reefs occurred during the warmest period of the Aquitanian. During rifting, bathymetric variations recorded in the studied succession are related to local synsedimentary tectonics whereas, during oceanic crust accretion, global sea level changes influence the sedimentation. This result allows to characterise and to accurately date the break-up unconformity at 20.35 Ma.
48
Rostami, Masoud A., Fabrizio Frontalini, R. Mark Leckie, Rodolfo Coccioni, Eric Font e Behnaz Balmaki. "Benthic Foraminifera Across the Cretaceous/Paleogene Boundary in the Eastern Tethys (Northern Alborz, Galanderud Section): Extinction Pattern and Paleoenvironmental Reconstruction". Journal of Foraminiferal Research 50, n.º 1 (1 de janeiro de 2020): 25–40. http://dx.doi.org/10.2113/gsjfr.50.1.25.
Texto completo da fonteResumo:
Abstract Extinction patterns, paleobathymetric inferences, and paleoenvironmental changes based on benthic foraminifera were investigated across the Cretaceous/Paleogene (K/Pg) boundary at the Galanderud section (Northern Alborz, Iran), which contains one of the most continuous and expanded K/Pg transitions in the eastern Tethys. On the basis of benthic foraminiferal taxa abundance and distribution, an outer neritic to uppermost bathyal paleo-depositional setting is inferred. In addition, benthic foraminiferal assemblages and planktic/benthic ratios do not indicate any major change in relative sea level during latest Maastrichtian-early Danian time. Changes in benthic foraminiferal assemblages, morphotypes, diversity, heterogeneity, and benthic foraminiferal oxygen index, coupled with statistical analyses, define three intervals. In the first interval (uppermost Maastrichtian Plummerita hantkeninoides Zone), benthic foraminiferal assemblages are moderately to well preserved and highly diverse, with a combination of epibenthic and endobenthic taxa indicating stable, mesotrophic to weakly eutrophic, normal marine conditions. A major change in benthic foraminiferal assemblages at the K/Pg boundary defines a second interval (basal Danian Guembelitria cretacea and lower part of Parvularugoglobigerina eugubina Zones) that is marked by a decrease in the endobenthic morphogroups as well as a decrease in diversity, heterogeneity, genus and species richness. This second interval denotes highly oligotrophic conditions and a collapse in productivity and food availability due to the extinction of some primary producers, with the exception of the three chalk beds representing short-lived blooms of calcareous dinoflagellates. Benthic foraminifera do not show significant extinction at the end of the Cretaceous at this section with only about an 8% loss of species. Additionally, the abundance of some opportunistic species, including Cibicidoides pseudoacutus and Tappanina selmensis, may reflect instability in the benthic foraminiferal assemblages. The third interval (middle-upper part of the Pv. eugubina Zone) is characterized by the dominance of epibenthic morphogroups (up to 70% of the assemblages) with a partial recovery of endobenthic groups. The characteristics of the benthic foraminiferal assemblages indicate that the flux of food to the benthos had not fully recovered during the early Danian.
49
Zech, Michael, Simon Rass, Björn Buggle, Manfred Löscher e Ludwig Zöller. "Reconstruction of the late Quaternary paleoenvironments of the Nussloch loess paleosol sequence, Germany, using n-alkane biomarkers". Quaternary Research 78, n.º 2 (1 de junho de 2012): 226–35. http://dx.doi.org/10.1016/j.yqres.2012.05.006.
Texto completo da fonteResumo:
AbstractThis study contributes to the paleoenvironmental reconstruction of the loess–paleosol sequence of Nussloch, Germany, by using n-alkanes as plant leaf-wax-derived lipid biomarkers. We found that n-alkane patterns and concentrations in the Saalian loess and the last interglacial Eemian paleosol of Nussloch point to very strong degradation and prevailing deciduous vegetation. Degradation effects in the overlying paleosols and loess layers are less pronounced and allow for the application of an end-member mixing model to estimate vegetation changes semi-quantitatively. Our findings highlight the potential for the interpretation of degradation-corrected n-alkane ratios. n-Alkane modelling results for loess layers, paleosols and an in-filled paleochannel dated to ~ 60–32 ka suggest that up to ~ 50% of the n-alkanes were derived from deciduous trees or shrubs. This finding is in agreement with the abundant occurrence of wood fragments and indicates a highly variable and dynamic landscape dominated by tundra shrubland. On the other hand, deciduous trees or shrubs did not contribute significantly to the soil organic matter in the late Weichselian loess layers and the intercalated Gelic Gleysols (~ 32–18 ka).
50
Hernández Fernández, Manuel. "Rodent paleofaunas as indicators of climatic change in Europe during the last 125,000 years". Quaternary Research 65, n.º 02 (março de 2006): 308–23. http://dx.doi.org/10.1016/j.yqres.2005.08.022.
Texto completo da fonteResumo:
AbstractThis paper presents a quantitative reconstruction of the European late Pleistocene paleoclimate based on 72 rodent assemblages of five sequences from France, Germany and Bulgaria, covering the last interglacial–glacial cycle. They show a pattern of severe changes in temperature, with reduced precipitation during the coldest periods. A tentative correlation between the isotopic and palynological records and the paleotemperature changes is shown. These changes are consistent with variations in atmospheric circulation patterns in response to an expanding–retracting Fennoscandian ice-sheet. They can be attributed to the enhancement–weakening of the Scandinavian-Polar anticyclone and its associated dry winds, the south–north shifting of the North Atlantic Polar Front, and the varying supply of moist air from the Atlantic. Qualitative paleoenvironmental analysis shows broadleaved-deciduous forests in France and Bulgaria during most of the studied period. Taiga and tundra appeared in eastern France during the lower Würm. The German sequence indicates the presence of coniferous forests. These results are broadly consistent with other paleobiological records (mammalian, avian and insect faunas, isotopic record in dental tissue, palynology). The main discrepancies with the paleoclimate inferred from the palynological record are found during the coldest periods and are probably due to the interaction between vegetation, climate, and atmospheric CO2 levels.