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Letteratura scientifica selezionata sul tema "Paleoenvironmental changes reconstruction"

Autore: Grafiati

Pubblicato: 14 marzo 2023

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Articoli di riviste sul tema "Paleoenvironmental changes reconstruction"

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. 7 (13 luglio 2016): 1519–38. http://dx.doi.org/10.5194/cp-12-1519-2016.

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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.

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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. 1 (18 febbraio 2019): 14–32. http://dx.doi.org/10.1017/qua.2018.143.

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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.

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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. 2 (1997): 775–80. http://dx.doi.org/10.1017/s0033822200018725.

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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.

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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. 1 (10 ottobre 2018): 149–62. http://dx.doi.org/10.1017/qua.2018.80.

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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.

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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. 4 (18 febbraio 2022): 641. http://dx.doi.org/10.3390/w14040641.

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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.

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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. 4 (20 febbraio 2023): 815. http://dx.doi.org/10.3390/w15040815.

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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.

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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. 4 (27 luglio 2018): 1199–213. http://dx.doi.org/10.1017/rdc.2018.68.

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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.

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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. 1 (1 aprile 2000): 63–80. http://dx.doi.org/10.1139/e99-107.

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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.

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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. 3 (maggio 1998): 312–21. http://dx.doi.org/10.1006/qres.1998.1965.

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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.

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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. 17-18 (agosto 2010): 2302–14. http://dx.doi.org/10.1016/j.quascirev.2010.05.033.

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Più fonti

Tesi sul tema "Paleoenvironmental changes reconstruction"

Valentina, Corti. "Palynology and Paleobotany of Permo-Triassic Beacon Supergroup at Allan Hills, South Victoria Land, Antarctica: stratigraphical and paleoenvironmental change implications". Doctoral thesis, Università di Siena, 2021. http://hdl.handle.net/11365/1133988.

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Nowadays the Antarctic continent is almost entirely covered by ice (around 98% of the total land surface) and the conditions are inhospitable for vegetation, apart from very few species such as mosses and lichens. During the geological time however, conditions were very different and the Phanerozoic fossil record documents several occurrences of vegetation remains also indicating the presence of wide high latitude forests. The life of plants in the continent was obviously strictly influenced by the evolving paleogeography and paleoenvironmental conditions and their mutual interactions during each time age of vegetation record. The thesis project has been finalized to define, constrain and discuss with new field and laboratory data the most likely Late Permian and Triassic paleoenvironmental reconstructions for the Victoria Land region in Antarctica, on the basis of a new set of paleobotany and palynological investigations of the unique fossiliferous strata recently found in the Beacon Supergroup of Allan Hills (South Victoria Land). The study was developed following a broad multidisciplinary and multi-analytical methodology in which paleobotany (including innovative approaches), palynology and palynostratigraphy methods and techniques play a key role in the reconstruction of the paleoenvironmental conditions and their changes through the time. In the palynostratigraphic sequence of Allan Hills were recovered the EPE, a strata horizon with long-shaped inertinite probably referred to a paleo-fire, situated in the last level of coal of the Permian sequence; going up in the sequence the paleoflora is affected by deeply change, as an adaptation to the new environmental condition up to the PTB, were the major samples were completely inert, due to a poor presence of flora and a changing of the sedimentary condition. After the PTB the first palynomorphs recovered are associated to an intensive fungal and algae activity, and just at the end of the Early Triassic, the flora came back to be flourishing, even if with a quite completely new association of pollen and spores, where is dominant the genus of Alisporites in the whole Middle and Late Triassic. The genus of Alisporites is probably linked to the Dicroidium macroflora, playing a central role during the Triassic time, replacing the Glossopteris flora which, on the other hand, dominated the Permian landscape. The Dicroidium, together with other genera, were recovered in great abundance in the Middle Triassic deposits of the Lashly Formation in Allan Hills, particularly within a horizon containing a so-called “Allan Hills Fossil Forest”, even if the term “forest “ is not strictly pertinent, as a way the trunks were deposited and transported by a massive flow, and no more in the growth-position. With an innovative technique was possible to reconstruct the main differences between the trunks there deposited and some other Permian fossil trunks outcropping in other areas of South Victoria Land. From this study, after a completely reconstruction of 237 years, that is the longest life-time never done for so old samples, were possible to note that the amplitude of the rings is probably linked to the amount of hours of sunlight during the years, so they are linked to the latitude to which the land was at time life-time of the trees. The last topic analysed about the “Allan Hills fossil forest” is the peculiar kind of fossilization, with a multianalytic approach were in fact possible to reconstruct modalities of coalification/charcoalification and multi-phase fossilization. The PAHs analysis highlights the presence of a high percentage of PAHs >4 ringed polynuclear aromatic hydrocarbons, that are typical attribute to pyrogenetic materials as fluoranthene, 9,10-dimethylanthracene and Pyrene, moreover also the δ13C measured on the growth tree rings shows a shifting of the curve in the more external rings, as an enrichment of 13C due to a partial combustion. After a first phase where the trunks were partially burned due to paleofires, they were transported through massive water flows. Subsequently, they were buried, deformed and petrified by a massive silica gel, probably occurred mainly during the Jurassic sill intrusion. The last step of the fossilization is the precipitation of calcite in a rounded shape occurred for some samples. Taken together the results of the study provide new important constraints and implications for reconstructing the history of sedimentary processes and coupled changing of the paleo-flora during a transition of deeply transformation of the biodiversity linked to the onset of greenhouse conditions, which occurred after the Permo-Triassic boundary, particularly during the Early Triassic.

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Lubitz, Rachael Lauren. "A late Holocene paleoenvironmental reconstruction of a coastal lake in northeastern Dominican Republic". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/53950.

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Coastal lakes, lagoons, and wetlands often provide excellent records of environmental change related to both marine and terrestrial processes. Although coastal paleoenvironments in the Caribbean have been a subject of increasing interest, long-term environmental reconstructions from lakes on the Atlantic side of the Caribbean islands are lacking. Laguna Limon is a freshwater lake in the El Seibo province of northeastern Dominican Republic. We collected a 315-cm sediment core from the center of the lake to examine lake evolution using loss-on-ignition and foraminiferal analysis. Loss-on-ignition results indicated the presence of a low-energy lagoon in the lake's present location between about 4700 and 1400 cal yr BP. During this period a foraminiferal assemblage dominated by the brackish-water Ammonia parkinsoniana but also containing relatively-abundant normal-marine salinity taxa (e.g., Quinqueloculina spp., Archaias angulatus, and Trochulina rosea) gradually was replaced by a low-diversity assemblage dominated by Ammonia tepida and Ammonia parkinsoniana, indicating a gradual decline in salinity due to the lagoon's growing isolation from the Atlantic Ocean. By 1400 cal. Yr. BP, the lake had become a shallow wetland, indicated by sediments with a high organic content. At 1200 cal. Yr. BP the lake flooded with freshwater, as it remains today. This study provides context for ongoing research into the environmental and human history of the Laguna Limon area.
Master of Science

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Them, II Theodore Roland. "Biogeochemical Cycling and Paleoenvironmental Reconstructions of the Toarcian Oceanic Anoxic Event from Western North America". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81908.

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The Toarcian Oceanic Anoxic Event (T-OAE; ~183 million years ago) represents an interval during the Mesozoic when the emplacement of the Karoo-Ferrar Large Igneous Province (LIP) is thought to have resulted in significant environmental change. Associated with this interval was the widespread deposition of organic-rich sediments, carbon cycle and seawater chemistry changes, global warming, the development of marine anoxia, and major extinction events. The majority of studies of this event that have documented these responses have come from the Boreal and Tethyan regions of Europe, thus casting some doubt to the regional versus global significance of the event. Thus my dissertation has sought to reconstruct biogeochemical and paleoenvironmental changes across the T-OAE from a sedimentary succession that was deposited on the margins of a different ocean basin away from the well-studied European successions. Specifically, I have studied the chemostratigraphy of the Fernie Formation of the Western Canada Sedimentary Basin (WCSB), which was deposited on the eastern margin of the Panthalassa Ocean. The Toarcian carbon isotope excursions (CIEs) in the WCSB confirm that these features are global phenomena. I have suggested a new driver for small-scale CIEs observed during the event: the release of wetland-derived methane during progressive global warming. The osmium isotope record and numerical modeling of the osmium cycle suggests that continental weathering rates increased during the T-OAE by 230 – 540%. Rhenium abundance data also suggests that the increased geographic extent of marine anoxia during the T-OAE caused a global drawdown in the seawater rhenium inventory. Iron speciation data are used to reconstruct redox conditions within the WCSB, which suggest ferruginous conditions developed in the more distal locations at the onset of the T-OAE before returning to euxinic (anoxic and sulfidic) conditions. This is likely related to enhanced pyrite burial on a global scale, which caused the drawdown of the seawater sulfate inventory, thus limiting pyrite formation in the distal locations. The proximal setting remained euxinic across the T-OAE, and in all locations the iron speciation data suggest anoxic conditions persistent well after the interval that has been traditionally called the end of the T-OAE.
Ph. D.

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Wilbur, Cricket C. "A History of Place: Using Phytolith Analysis to Discern Holocene Vegetation Change on Sanak Island, Western Gulf of Alaska". Antioch University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=antioch1395927847.

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Jamka, Joanna Magdalena. "High resolution integrated reconstruction of holocene climatic and paleoenvironmental changes in the southern tyrrhenian sea: a coda approach". Tesi di dottorato, 2019. http://www.fedoa.unina.it/12985/1/PhDJoannaJamka.pdf.

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The field of this research is the reconstruction of paleoenvironmental changes used complex methods obtained by Compositional Data Analysis statistical methods (CoDA), so in the result to develop new transfer functions (mathematical methods to obtain data to reconstruct paleoenvironmental changes) due to which we can observe the paleoclimatic and paleoenvironmental changes and volcanic activities during The Late Glacial and Holocene in the Gulf of Naples and Gulf of Salerno in collaboration with IAMC (CNR) and University of Girona (statistical methods). One of the main objectives of the thesis is to elaborate statistical methods under the framework of CoDa (Compositional data analysis: CoDa; Aitchison, 1986) to obtain the SST (sea surface temperatures) from counting of fossil assemblages. Two approaches were considered: 1) The modern analogue technique (CoDaMAT)– the revised method adopts the Aitchison distance, obtained from isometric log-ratio coordinates of relative abundances, as a natural measure of similarity among assemblages. The number of analogues from which obtain the estimates was determined through leave-one-out verification of modern assemblages. Mean distances and local outlier factor are considered to evaluate the quality of palaeoestimates. The method has been tested on Atlantic Ocean and Mediterranean planktonic foraminiferal assemblages to reconstruct past sea surface temperatures (SST). The MAT compares fossil assemblages with modern ones using a distance measure or a similarity coefficient. The palaeoenvironmental estimates are obtained from the environmental parameters measured at the location of the most similar modern assemblages. For each fossil samples the nearest modern ones are found by adopting an appropriate distance (d). 2) Regression-based methods - standard and robust Partial Least Squares Regression (PLSR) and Principal Component Regression (PCR), applied to the log-ratio coordinates of percentage data of Atlantic Ocean and Mediterranean Sea planktonic foraminifera assemblages. Due to the presence of groups, it was preferred to model separately high latitude and mid to low latitude assemblages. The application of the obtained transfer function involves cluster, MANOVA and discriminant analysis applied to the log-ratio transformed fossil assemblage’s composition.

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"Geoarchaeology at the Red Tail site : paleoenvironmental reconstruction of climate change during the Holocene". Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-06-1185.

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The Red Tail site is one of 19 archaeological sites that lie within central Saskatchewan’s Wanuskewin Heritage Park. Since the creation of a long-term research program in 1984, many of these sites have been excavated making this the longest running archaeological project in Canada. This has provided an extensive body of archaeological evidence of human activity dating as early as the Early Precontact Period. Despite the extensive archaeological excavation and research that has occurred, relatively few geomorphic and paleoenvironmental studies have been conducted within the area. Paleoenvironmental data provide important context in building archaeological interpretations of past lifeways. The Red Tail site was originally excavated in 1988 and 1989 to a depth of approximately 2.7 m. In 2007, the site was revisited in order to conduct subsurface coring to a depth of over 6 m using a Geoprobe coring rig. This method allowed recovery of culturally sterile soils/sediments beyond the depth of the original excavation. This project includes analysis of these cores in order to investigate geomorphic processes active at the site and proxy indicators of paleoenvironment and paleoclimate. Analysis of two of the cores included detailed description of the recovered soils and sediments, as well as stable isotope and phytolith analysis of selected units in one of the cores. This suite of methods provides a robust, multi-proxy interpretation of geomorphic change and paleoenvironmental conditions at the site. The site was geomorphically active during the Late Pleistocene and Early Holocene, reflective of a dynamic and fluctuating climate following the glacial retreat. As the environment became more stable during the Middle to Late Holocene, periods of landscape stability are reflected in a sequence of buried soils. The paleoenvironmental and paleoclimatic record recovered from these buried soils shows a fairly consistent history of C3-plant dominated communities, reflective of moist, cool climate conditions. The relatively stable environmental and climatic conditions reflected at the site contribute to the understanding of the Wanuskewin area as an oasis on the prairies.

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McLachlan, Sandy Melvin Stuart. "Dinoflagellate cysts across the Cretaceous–Paleogene (K/Pg) boundary in the North Pacific; biostratigraphy, diversity, and paleoenvironmental reconstructions". Thesis, 2021. http://hdl.handle.net/1828/13341.

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The central objective of this study is to understand phytoplankton community response following the global mass extinction event at the Cretaceous–Paleogene (K/Pg) boundary. The objective is approached through analysis of dinoflagellate cyst assemblages across the boundary interval in the North Pacific. Dinoflagellate cysts are powerful tools for deep time paleoenvironmental reconstructions and this group of microfossils has been vastly underutilized in this region of the world. On this premise, comprehensive marine palynological surveys were undertaken for the Oyster Bay Formation of eastern Vancouver Island, British Columbia, Canada and Shatsky Rise in the northwest Pacific. The Oyster Bay Formation work resulted in the discovery of the first K/Pg boundary succession west of the Rocky Mountains based on biostratigraphic controls and refined taxonomy for the genus Cannosphaeropsis found within these strata. Three new taxa are described: Cannosphaeropsis franciscana subsp. vacuoseptata subsp. nov., Cannosphaeropsis franciscana subsp. vesiculata subsp. nov. and Phelodinium fensomei sp. nov. The cyst assemblages reveal endemic associations and signals of transition between offshore coastal to estuarine settings in keeping with global eustatic trends. Oyster Bay Formation results and interpretations are compared to analyses of core samples from Deep Sea Drilling Project Site 577 at Shatsky Rise. Contrast is seen between a diverse, highly productive coastal to estuarine environment in the Oyster Bay Formation as represented by organic-walled taxa and an oligotrophic bathyal environment at Shatsky Rise during the same interval as represented by a small number of calcareous taxa. These two regions form the basis for comparison between differing assemblages in order to ascertain the extent to which phytoplankton communities were affected by changes in sea-surface and water mass conditions in conjunction with the K/Pg event. The findings reveal measurable impacts of climate and paleoenvironmental change reflected by shifts in assemblage composition and cyst morphology. A lack of extinction among many forms is consistent with studies from around the globe as presented in an exhaustive review of the literature. The dinoflagellates were marginally impacted with the most specialized taxa presenting a record of sea-surface temperature fluctuation, nutrient supply and opportunistic niche exploitation.
Graduate
2022-08-20

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Libri sul tema "Paleoenvironmental changes reconstruction"

Climate and the Dolores River Anasazi: A paleoenvironmental reconstruction from a 10,000-year pollen record, La Plata Mountains, southwestern Colorado. Salt Lake City, Utah: University of Utah Press, 1988.

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J, Dowsett Harry, e Geological Survey (U.S.), a cura di. Middle Pliocene paleoenvironmental reconstruction: PRISM2. [Reston, Va.?: U.S. Dept. of the Interior, U.S. Geological Survey, 1999.

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J, Dowsett Harry, e Geological Survey (U.S.), a cura di. Middle Pliocene paleoenvironmental reconstruction: PRISM2. [Reston, Va.?: U.S. Dept. of the Interior, U.S. Geological Survey, 1999.

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Capitoli di libri sul tema "Paleoenvironmental changes reconstruction"

Aakala, Tuomas, Cécile C. Remy, Dominique Arseneault, Hubert Morin, Martin P. Girardin, Fabio Gennaretti, Lionel Navarro et al. "Millennial-Scale Disturbance History of the Boreal Zone". In Advances in Global Change Research, 53–87. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-15988-6_2.

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AbstractLong-term disturbance histories, reconstructed using diverse paleoecological tools, provide high-quality information about pre-observational periods. These data offer a portrait of past environmental variability for understanding the long-term patterns in climate and disturbance regimes and the forest ecosystem response to these changes. Paleoenvironmental records also provide a longer-term context against which current anthropogenic-related environmental changes can be evaluated. Records of the long-term interactions between disturbances, vegetation, and climate help guide forest management practices that aim to mirror “natural” disturbance regimes. In this chapter, we outline how paleoecologists obtain these long-term data sets and extract paleoenvironmental information from a range of sources. We demonstrate how the reconstruction of key disturbances in the boreal forest, such as fire and insect outbreaks, provides critical long-term views of disturbance-climate-vegetation interactions. Recent developments of novel proxies are highlighted to illustrate advances in reconstructing millennial-scale disturbance-related dynamics and how this new information benefits the sustainable management of boreal forests in a rapidly changing climate.

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Khadraoui, Afef, Jérôme Bonnin, Chahira Zaïbi e Fekri Kamoun. "Reconstruction of Holocene Paleoenvironmental Changes Along Northern Coast of Sfax: Analysis of Foraminiferal Associations". In Patterns and Mechanisms of Climate, Paleoclimate and Paleoenvironmental Changes from Low-Latitude Regions, 77–79. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-01599-2_18.

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Morrison, Brigid V., e Joanna C. Ellison. "Palaeo-Environmental Approaches to Reconstructing Sea Level Changes in Estuaries". In Applications of Paleoenvironmental Techniques in Estuarine Studies, 471–94. Dordrecht: Springer Netherlands, 2017. http://dx.doi.org/10.1007/978-94-024-0990-1_19.

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Staines-Urías, Francisca. "Corals in Estuarine Environments: Their Response to Environmental Changes and Application in Reconstructing Past Environmental Variability". In Applications of Paleoenvironmental Techniques in Estuarine Studies, 389–422. Dordrecht: Springer Netherlands, 2017. http://dx.doi.org/10.1007/978-94-024-0990-1_16.

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Lazarus, Dave, e Jean Pierre Caulet. "Cenozoic Southern Ocean reconstructions from sedimentologic, radiolarian, and other microfossil data". In The Antarctic Paleoenvironment: A Perspective on Global Change: Part Two, 145–74. Washington, D. C.: American Geophysical Union, 1993. http://dx.doi.org/10.1029/ar060p0145.

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Cohen, Andrew S. "Paleoecological Archives in Lake Deposits I: Problems and Methods". In Paleolimnology. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195133530.003.0014.

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Fossils provide some of the most detailed sources of information for environmental reconstruction available to the paleolimnologist. The use of lacustrine fossils to infer paleoenvironmental conditions is fundamentally based on inferences derived from modern correlations between the distribution of organisms and environmental variables, coupled with an understanding of taphonomy, the study of the fossilization process. No single group of organisms provides a comprehensive picture of lake ecosystems or environmental change, so it is always desirable to gather paleoecological records from multiple clades and habitats in a paleolimnological study. Analysis of multiple clades provides a means of establishing or testing ecological hypotheses that may not be possible from the study of one group alone. For example, many limnological processes affect the plankton, littoral organisms, and benthos in predictable sequences, and with predictable intensities. The most comprehensive study of fossil data and data analysis will be meaningless if the fossils studied are misidentified. A good taxonomic framework is an essential element of paleoecological studies. Accurate identification of described species, and the curation of voucher specimens, photographs, and other descriptive materials of undescribed species is important, to insure the quality of a paleolimnologist’s ongoing work, and to avoid future errors based on previously misidentified fossil specimens. Using fossils to interpret lacustrine paleoenvironments requires not only an understanding of modern organism distributions, but also an understanding of four additional factors we did not consider in chapter 5: (1) ecological causality and scale, (2) taphonomy and time-averaging, (3) historical contingency, and (4) evolutionary processes. One of the most common uses of fossil data in lakes is to try and reconstruct changes in some physical or biological forcing process from changes in abundance or morphology of the fossil organisms affected by the process. We might be interested in reconstructing changes in nutrient flux to the lake, based on changes in the relative abundances of some fossil animals. However, these animals actually responded to nutrient load only indirectly, through the effect of nutrient load on autotrophs and/or organic detritus. Now suppose that our ultimate objective is not really to understand productivity changes or nutrients, so much as to understand climate changes that may be driving productivity changes.

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Rickard, David. "Framboid Sizes". In Framboids, 21–46. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780190080112.003.0002.

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Framboid size-frequency plots show log-normal distributions with a geometric mean diameter of 6.0 μ‎m and with 95% of framboids ranging between 2.9 and 12.3 μ‎m. The largest framboids may be 250 μ‎m in diameter, although spherical aggregates of framboids, known as polyframboids, may range up to 900 μ‎m in diameter. Various spherical clusters of nanoparticles have been described which are less than 0.2 μ‎m in diameter. These do not form a continuum with framboids. There is no evidence for any significant change in framboid diameters with geologic time, and the differences in mean sizes between hydrothermal and sedimentary framboids do not, at present, appear to be statistically significant. By contrast, it appears that the mean diameters of framboids from non-marine sediments are significantly larger (7.6 μ‎m) than marine framboids (5.7 μ‎m). There is some evidence that framboids formed in the water column are smaller than those formed in sediments, but the non-critical use of this possible difference as a proxy for paleoenvironmental reconstructions is not robust. So-called microframboids and nanoframboids are discrete entities which are distinct from framboids. They are nanoparticle clusters and are not produced by the same processes as those involved in framboid formation, nor do they behave in the same way. They are more akin to atomic clusters, which form similar constructs.

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Atti di convegni sul tema "Paleoenvironmental changes reconstruction"

Johnson, Luke, Jillian M. Maloney, Shannon A. Klotsko, Amy E. Gusick, Todd J. Braje e David Ball. "PRELIMINARY SEDIMENT CORE ANALYSIS AND PALEOENVIRONMENTAL RECONSTRUCTION: NORTHERN CHANNEL ISLANDS PLATFORM, CALIFORNIA". In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-337923.

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Harff, Jan, Wenyan Zhang, Michael Meyer e Ralf Schneider. "Coastline Change from Paleoenvironmental Reconstruction to Future Scenarios: A Case Study from the Baltic". In Solutions to Coastal Disasters Conference 2011. Reston, VA: American Society of Civil Engineers, 2011. http://dx.doi.org/10.1061/41185(417)16.

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Knezaurek, G., E. Menichetti, A. Piva e S. Torricelli. "A Multiproxy Approach to the Paleoenvironmental Reconstruction of the Paleogene Succession in the Rovuma Basin, Offshore Mozambique: Signatures of Eustatism, Climate Change and ‘African Superswell’". In Third EAGE Eastern Africa Petroleum Geoscience Forum. Netherlands: EAGE Publications BV, 2017. http://dx.doi.org/10.3997/2214-4609.201702413.

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