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Wout Krijgsman - One of the best experts on this subject based on the ideXlab platform.
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New age constraints on the western Betic intramontane basins : A late Tortonian closure of the Guadalhorce Corridor?
Terra Nova, 2018Co-Authors: Marlies Van Der Schee, Bas C.j. Van Den Berg, Walter Capella, Dirk Simon, Francisco Javier Sierro, Wout KrijgsmanAbstract:Several gateways connected the Mediterranean with the Atlantic during the late Miocene but the timing of closure and therefore their role prior to and during the Messinian Salinity Crisis (5.97-5.33 Ma) is still under debate. The timing of closure of the Guadalhorce Corridor is especially disputed as the common lack of marine microfossils hampers precise age determination. Here we present new biostratigraphic age constraints on the sediments of the Ronda, Antequera and Arcos regions, which formed the northern part of the Guadalhorce Corridor. The general presence of Globorotalia menardii 4 in the youngest deep-marine sediments of all three regions indicates a late Tortonian age, older than 7.51 Ma. We conclude that the Guadalhorce Corridor closed during the late Tortonian, well before the onset of the Messinian Salinity Crisis and that the late Tortonian tectonic uplift of the eastern Betics extended into the western Betics.
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Concurrent tectonic and climatic changes recorded in upper Tortonian sediments from the Eastern Mediterranean
Terra Nova, 2010Co-Authors: Cornelia M Köhler, Wout Krijgsman, Douwe J.j. Van Hinsbergen, David Heslop, Guillaume Dupont-nivetAbstract:Terra Nova, 22, 52–63, 2010 Abstract The upper Tortonian Metochia marls on the island of Gavdos provide an ideal geological archive to trace variations in Aegean sediment supply as well as changes in the North African monsoon system. A fuzzy-cluster analysis on the multiproxy geochemical and rock magnetic dataset of the astronomically tuned sedimentary succession shows a dramatic shift in the dominance of ‘Aegean tectonic’ clusters to ‘North African climate’ clusters. The tectonic signature, traced by the starvation of the Cretan sediment, now enables to date the late Tortonian basin foundering on Crete, related to the tectonic break-up of the Aegean landmass, at c. 8.2 Ma. The synchronous decrease in the North African climate proxies is interpreted to indicate a change in the depositional conditions of the sink rather than a climatic change in the African source. This illustrates that interpretations of climate proxies require a multiproxy approach which also assesses possible contributions of regional tectonism.
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The upper Tortonian–lower Messinian at Monte dei Corvi (Northern Apennines, Italy): Completing a Mediterranean reference section for the Tortonian Stage
Earth and Planetary Science Letters, 2009Co-Authors: S.k. Hüsing, Frederik J Hilgen, K.f. Kuiper, W. Link, Wout KrijgsmanAbstract:A high-resolution integrated stratigraphy including biostratigraphy, magnetostratigraphy, tephrostratigraphy and cyclostratigraphy is presented for the upper Tortonian and lower Messinian (Upper Miocene) at Monte dei Corvi. Numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning, while radioisotope dating of ash layers produced less reliable ages. The deep marine succession is characterized by large-scale non-repetitive stratigraphic changes allowing the discrimination between a Lower, Brownish, Rossini and Euxinic Shale Interval. The sedimentary cycles, which occur superimposed on these large-scale changes, are related to astronomical climate forcing. Astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events, reversal boundaries and volcanic ash layers, but also for the observed non-cyclic changes. These can be linked to environmental and geodynamic changes in the Mediterranean region preceding the Messinian Salinity Crisis. The beginning of the Brownish Interval marked by tripartite cycles at 8.017 Ma coincides with tectonic re-arrangements in the Mediterranean, such as compression in the Betics and opening of the Rifian corridor. At 7.616 Ma the change to the calcareous Rossini Interval can be linked to tectonic uplift in the northern Apennines and the deepening of the Rifian corridor, while the Betic corridor became restricted coinciding with the end of evaporite deposition in the eastern Betics. The change to euxinic shales at 7.168 Ma reflects basin-wide restriction marked by diatomite and sapropel formation in the Mediterranean basin related to the severely constricted Betic and Rifian corridors. The occurrence of a tripartite construction of cycles in the euxinic shales at 6.719 Ma coincides with diatomite formation in the eastern Mediterranean, uplift and shallowing in the Northern Apennines and further constriction of the Atlantic gateways. We conclude that late Tortonian-early Messinian tectonic and environmental events occur remarkably synchronously in the Mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity-controlled climatic changes. In combination with the upper Serravallian and lower Tortonian interval, which includes the formal Tortonian Global Stratotype Section and Point (GSSP), the Monte dei Corvi is the only complete section in the Mediterranean covering the entire Tortonian Stage. We therefore propose the Monte dei Corvi section as Tortonian reference section, particularly for the Mediterranean region. In addition, it may serve as a unit-stratotype for the Tortonian
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The upper Tortonian-lower Messinian at Monte dei Corvi (Northern Apennines, Italy): Completing a Mediterranean reference section for the Tortonian Stage
Earth and Planetary Science Letters, 2009Co-Authors: S.k. Hüsing, Klaudia F. Kuiper, Frederik J Hilgen, W. Link, Wout KrijgsmanAbstract:Abstract A high-resolution integrated stratigraphy including biostratigraphy, magnetostratigraphy, tephrostratigraphy and cyclostratigraphy is presented for the upper Tortonian and lower Messinian (Upper Miocene) at Monte dei Corvi. Numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning, while radioisotope dating of ash layers produced less reliable ages. The deep marine succession is characterized by large-scale non-repetitive stratigraphic changes allowing the discrimination between a Lower, Brownish, Rossini and Euxinic Shale Interval. The sedimentary cycles, which occur superimposed on these large-scale changes, are related to astronomical climate forcing. Astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events, reversal boundaries and volcanic ash layers, but also for the observed non-cyclic changes. These can be linked to environmental and geodynamic changes in the Mediterranean region preceding the Messinian Salinity Crisis. The beginning of the Brownish Interval marked by tripartite cycles at 8.017 Ma coincides with tectonic re-arrangements in the Mediterranean, such as compression in the Betics and opening of the Rifian corridor. At 7.616 Ma the change to the calcareous Rossini Interval can be linked to tectonic uplift in the northern Apennines and the deepening of the Rifian corridor, while the Betic corridor became restricted coinciding with the end of evaporite deposition in the eastern Betics. The change to euxinic shales at 7.168 Ma reflects basin-wide restriction marked by diatomite and sapropel formation in the Mediterranean basin related to the severely constricted Betic and Rifian corridors. The occurrence of a tripartite construction of cycles in the euxinic shales at 6.719 Ma coincides with diatomite formation in the eastern Mediterranean, uplift and shallowing in the Northern Apennines and further constriction of the Atlantic gateways. We conclude that late Tortonian–early Messinian tectonic and environmental events occur remarkably synchronously in the Mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity-controlled climatic changes. In combination with the upper Serravallian and lower Tortonian interval, which includes the formal Tortonian Global Stratotype Section and Point (GSSP), the Monte dei Corvi is the only complete section in the Mediterranean covering the entire Tortonian Stage. We therefore propose the Monte dei Corvi section as Tortonian reference section, particularly for the Mediterranean region. In addition, it may serve as a unit-stratotype for the Tortonian.
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revised isotopic 40ar 39ar age for the lamproite volcano of cabezos negros fortuna basin eastern betics se spain
Palaeogeography Palaeoclimatology Palaeoecology, 2006Co-Authors: Klaudia F. Kuiper, Wout Krijgsman, Miguel Garcés, J R WijbransAbstract:Abstract A new isotopic age of 7.71 ± 0.11 Ma (1σ) has been obtained with the 40Ar/39Ar incremental heating technique on phlogopites from the Miocene volcanic rocks (lamproites) of the Fortuna Basin in southeast Spain. This age is significantly older than earlier reported K/Ar ages, but confirms recent magnetostratigraphic ages on the sedimentary sequences of the eastern Betics. Because the volcanic rocks are intercalated in the stratigraphic sequence of the Fortuna Basin directly above the transition from evaporitic to continental sediments, it implies that the Fortuna evaporites are older than 7.71 Ma, and thus of Tortonian age. In addition, it shows that the volcanism in the Fortuna Basin must be attributed to a late Tortonian deformation phase and not to Messinian tectonics. Consequently, these results form an important step towards a consistent chronological framework for the sedimentary, tectonic and paleogeographic evolution of the Fortuna Basin during the late Miocene.
Frederik J Hilgen - One of the best experts on this subject based on the ideXlab platform.
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The upper Tortonian–lower Messinian at Monte dei Corvi (Northern Apennines, Italy): Completing a Mediterranean reference section for the Tortonian Stage
Earth and Planetary Science Letters, 2009Co-Authors: S.k. Hüsing, Frederik J Hilgen, K.f. Kuiper, W. Link, Wout KrijgsmanAbstract:A high-resolution integrated stratigraphy including biostratigraphy, magnetostratigraphy, tephrostratigraphy and cyclostratigraphy is presented for the upper Tortonian and lower Messinian (Upper Miocene) at Monte dei Corvi. Numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning, while radioisotope dating of ash layers produced less reliable ages. The deep marine succession is characterized by large-scale non-repetitive stratigraphic changes allowing the discrimination between a Lower, Brownish, Rossini and Euxinic Shale Interval. The sedimentary cycles, which occur superimposed on these large-scale changes, are related to astronomical climate forcing. Astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events, reversal boundaries and volcanic ash layers, but also for the observed non-cyclic changes. These can be linked to environmental and geodynamic changes in the Mediterranean region preceding the Messinian Salinity Crisis. The beginning of the Brownish Interval marked by tripartite cycles at 8.017 Ma coincides with tectonic re-arrangements in the Mediterranean, such as compression in the Betics and opening of the Rifian corridor. At 7.616 Ma the change to the calcareous Rossini Interval can be linked to tectonic uplift in the northern Apennines and the deepening of the Rifian corridor, while the Betic corridor became restricted coinciding with the end of evaporite deposition in the eastern Betics. The change to euxinic shales at 7.168 Ma reflects basin-wide restriction marked by diatomite and sapropel formation in the Mediterranean basin related to the severely constricted Betic and Rifian corridors. The occurrence of a tripartite construction of cycles in the euxinic shales at 6.719 Ma coincides with diatomite formation in the eastern Mediterranean, uplift and shallowing in the Northern Apennines and further constriction of the Atlantic gateways. We conclude that late Tortonian-early Messinian tectonic and environmental events occur remarkably synchronously in the Mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity-controlled climatic changes. In combination with the upper Serravallian and lower Tortonian interval, which includes the formal Tortonian Global Stratotype Section and Point (GSSP), the Monte dei Corvi is the only complete section in the Mediterranean covering the entire Tortonian Stage. We therefore propose the Monte dei Corvi section as Tortonian reference section, particularly for the Mediterranean region. In addition, it may serve as a unit-stratotype for the Tortonian
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The upper Tortonian-lower Messinian at Monte dei Corvi (Northern Apennines, Italy): Completing a Mediterranean reference section for the Tortonian Stage
Earth and Planetary Science Letters, 2009Co-Authors: S.k. Hüsing, Klaudia F. Kuiper, Frederik J Hilgen, W. Link, Wout KrijgsmanAbstract:Abstract A high-resolution integrated stratigraphy including biostratigraphy, magnetostratigraphy, tephrostratigraphy and cyclostratigraphy is presented for the upper Tortonian and lower Messinian (Upper Miocene) at Monte dei Corvi. Numerical age control comes from a combination of magnetobiostratigrapic dating and astronomical tuning, while radioisotope dating of ash layers produced less reliable ages. The deep marine succession is characterized by large-scale non-repetitive stratigraphic changes allowing the discrimination between a Lower, Brownish, Rossini and Euxinic Shale Interval. The sedimentary cycles, which occur superimposed on these large-scale changes, are related to astronomical climate forcing. Astronomical tuning of the sedimentary cycles provides not only absolute ages for biostratigraphic events, reversal boundaries and volcanic ash layers, but also for the observed non-cyclic changes. These can be linked to environmental and geodynamic changes in the Mediterranean region preceding the Messinian Salinity Crisis. The beginning of the Brownish Interval marked by tripartite cycles at 8.017 Ma coincides with tectonic re-arrangements in the Mediterranean, such as compression in the Betics and opening of the Rifian corridor. At 7.616 Ma the change to the calcareous Rossini Interval can be linked to tectonic uplift in the northern Apennines and the deepening of the Rifian corridor, while the Betic corridor became restricted coinciding with the end of evaporite deposition in the eastern Betics. The change to euxinic shales at 7.168 Ma reflects basin-wide restriction marked by diatomite and sapropel formation in the Mediterranean basin related to the severely constricted Betic and Rifian corridors. The occurrence of a tripartite construction of cycles in the euxinic shales at 6.719 Ma coincides with diatomite formation in the eastern Mediterranean, uplift and shallowing in the Northern Apennines and further constriction of the Atlantic gateways. We conclude that late Tortonian–early Messinian tectonic and environmental events occur remarkably synchronously in the Mediterranean basin and most likely result from a combination of geodynamic processes and eccentricity-controlled climatic changes. In combination with the upper Serravallian and lower Tortonian interval, which includes the formal Tortonian Global Stratotype Section and Point (GSSP), the Monte dei Corvi is the only complete section in the Mediterranean covering the entire Tortonian Stage. We therefore propose the Monte dei Corvi section as Tortonian reference section, particularly for the Mediterranean region. In addition, it may serve as a unit-stratotype for the Tortonian.
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radioisotopic dating of the Tortonian global stratotype section and point implications for intercalibration of 40ar 39ar and astronomical dating methods
Terra Nova, 2005Co-Authors: Klaudia F. Kuiper, Jan Wijbrans, Frederik J HilgenAbstract:In this paper we present new 40 Ar/ 39 Ar data of volcanic ash layers intercalated in the astronomically dated sections of Monte dei Corvi and Monte Gibliscemi (Italy) to obtain better radioisotopic time constraints on the Serravallian/Tortonian boundary and to confirm the intercalibration of radioisotopic and astronomical time proposed by Kuiper et al. [2004; Fish Canyon Tuff (FCT)-sanidine at 28.21 ± 0.03 Ma]. The latter intercalibration is supported by astronomically calibrated FCT sanidine ages for two ash layers at Monte Gibliscemi (GiF-1: 28.28 ± 0.04; GiD-3: 28.16 ± 0.04 Ma; ±1 SE). As a consequence, our results support the astronomically calibrated age of 11.608 Ma for the Tortonian Global Stratotype Section and Point and, hence, the tuning of the Serravallian/ Tortonian boundary interval. The Ancona and Respighi levels at Monte dei Corvi give a more diffuse picture, possibly because of contamination with detrital or xenocrystic material and the inferior quality of biotite for intercalibration
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Radioisotopic dating of the Tortonian Global Stratotype Section and Point: implications for intercalibration of 40Ar/39Ar and astronomical dating methods
Terra Nova, 2005Co-Authors: Klaudia F. Kuiper, Jan Wijbrans, Frederik J HilgenAbstract:In this paper we present new 40 Ar/ 39 Ar data of volcanic ash layers intercalated in the astronomically dated sections of Monte dei Corvi and Monte Gibliscemi (Italy) to obtain better radioisotopic time constraints on the Serravallian/Tortonian boundary and to confirm the intercalibration of radioisotopic and astronomical time proposed by Kuiper et al. [2004; Fish Canyon Tuff (FCT)-sanidine at 28.21 ± 0.03 Ma]. The latter intercalibration is supported by astronomically calibrated FCT sanidine ages for two ash layers at Monte Gibliscemi (GiF-1: 28.28 ± 0.04; GiD-3: 28.16 ± 0.04 Ma; ±1 SE). As a consequence, our results support the astronomically calibrated age of 11.608 Ma for the Tortonian Global Stratotype Section and Point and, hence, the tuning of the Serravallian/ Tortonian boundary interval. The Ancona and Respighi levels at Monte dei Corvi give a more diffuse picture, possibly because of contamination with detrital or xenocrystic material and the inferior quality of biotite for intercalibration
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integrated stratigraphy and astronomical tuning of the serravallian and lower Tortonian at monte dei corvi middle upper miocene northern italy
Palaeogeography Palaeoclimatology Palaeoecology, 2003Co-Authors: Frederik J Hilgen, Wout Krijgsman, Isabella Raffi, Abdul H Aziz, E. TurcoAbstract:An integrated stratigraphy (calcareous plankton biostratigraphy, magnetostratigraphy and cyclostratigraphy) is presented for the Serravallian and lower Tortonian part (Middle^Upper Miocene) of the Monte dei Corvi section located in northern Italy.The detailed biostratigraphic analysis showed that both the Discoaster kugleri acme and the first influx of Neogloboquadrina acostaensis are recorded at Monte dei Corvi; these events, which passed unobserved in previous studies, play an important role in delineating the Serravallian^Tortonian boundary.Thermal and alternating field demagnetization revealed a characteristic low-temperature component marked by dual polarities.The resultant magnetostratigraphy for the upper part of the section can be unambiguously calibrated to the GPTS ranging from C5n.2n up to C4r.2r. Unfortunately, the lower part of the section, including the Serravallian^Tortonian boundary interval, did not produce a reliable magnetostratigraphy despite the fact that some short reversed intervals and a single normal interval are recorded.Using sedimentary cycle patterns in combination with the calcareous plankton biostratigraphy the section can be correlated cyclostratigraphically in detail to the partially overlapping and previously tuned section of Monte Gibliscemi on Sicily.The Monte dei Corvi section is dated astronomically by calibrating the basic small-scale sedimentary cycles to the precession and 65‡N lat.summer insolation time series of the La93 solution following an initial tuning of larger-scale cycles to eccentricity.An almost perfect fit is found between the cycle patterns and intricate details, especially precession^obliquity interference, in the insolation target between 8.5 and 10 Ma. The tuning to precession remains robust for most intervals back to the base of the section dated at 13.4 Ma and shows that the section is continuous apart from a possible short hiatus in the Tortonian. It provides accurate astronomical ages for all sedimentary cycles, calcareous plankton events, polarity reversals and ash layers and marks a significant improvement of the recently proposed astronomical calibrations of the Monte dei Corvi section and of parallel sections in the Mediterranean.Astronomical ages for the Ancona and Respighi ashbeds are significantly older than previously reported 40 Ar/ 39 Ar biotite ages, even if the revised older age for the FCT-san dating standard of 28.02 Ma is applied. The astronomical dating of the magnetic reversals in the Monte dei Corvi section results in the completion of the astronomical polarity time scale for the last 13 Myr.The Monte dei Corvi section has recently been proposed as the stratotype section for the Serravallian^Tortonian boundary despite the moderate to
Mark J. Dekkers - One of the best experts on this subject based on the ideXlab platform.
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palaeomagnetism and rock magnetism of the Tortonian messinian boundary stratotype at falconara sicily
Physics of the Earth and Planetary Interiors, 1992Co-Authors: Cor G. Langereis, Mark J. DekkersAbstract:Langereis, C.G. and Dekkers, MJ., 1992. Palaeomagnetism and rock magnetism of the Tortonian—Messinian boundary stratotype at Falconara, Sicily. Phys. Earth Planet. Inter., 71: 100—111. The Tortonian—Messinian boundary stratotype at Stazione Falconara (Sicily) yields normal polarity remanent magnetizations of post-tilting age, implying that the entire section is (sub)recently remagnetized. The absence of direct time control on the biostratigraphic datum levels in the section makes it therefore less suited as a boundary stratotype section. Existing age estimates for the Tortonian—Messinian boundary are discussed; it is concluded that an age of 5.6 Ma is at present the best estimate. Assessment of the magnetic mineralogy in the Falconara section shows that rock magnetic parameters are for a large part lithologically controlled. A second important controlling factor is the numerous joints, which could have acted as channels for circulating groundwater and from which predominantly (sub)recent finely crystalline haematite was precipitated, possibly mediated by weathering processes. This haematite has completely replaced an earlier and presumably magnetite-dominated magnetic mineralogy.
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Palaeomagnetism and rock magnetism of the Tortonian—Messinian boundary stratotype at Falconara, Sicily
Physics of the Earth and Planetary Interiors, 1992Co-Authors: Cor G. Langereis, Mark J. DekkersAbstract:Langereis, C.G. and Dekkers, MJ., 1992. Palaeomagnetism and rock magnetism of the Tortonian—Messinian boundary stratotype at Falconara, Sicily. Phys. Earth Planet. Inter., 71: 100—111. The Tortonian—Messinian boundary stratotype at Stazione Falconara (Sicily) yields normal polarity remanent magnetizations of post-tilting age, implying that the entire section is (sub)recently remagnetized. The absence of direct time control on the biostratigraphic datum levels in the section makes it therefore less suited as a boundary stratotype section. Existing age estimates for the Tortonian—Messinian boundary are discussed; it is concluded that an age of 5.6 Ma is at present the best estimate. Assessment of the magnetic mineralogy in the Falconara section shows that rock magnetic parameters are for a large part lithologically controlled. A second important controlling factor is the numerous joints, which could have acted as channels for circulating groundwater and from which predominantly (sub)recent finely crystalline haematite was precipitated, possibly mediated by weathering processes. This haematite has completely replaced an earlier and presumably magnetite-dominated magnetic mineralogy.
Stephen J. Hunter - One of the best experts on this subject based on the ideXlab platform.
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a Tortonian late miocene 11 61 7 25 ma global vegetation reconstruction
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Matthew J. Pound, Alan M. Haywood, Ulrich Salzmann, James B. Riding, Daniel J. Lunt, Stephen J. HunterAbstract:For the Tortonian age of the Miocene Epoch (11.6–7.25 Ma) we present a global palaeobotanical and palaeoecologically-based vegetation dataset, combined with a best-fit Late Miocene climate-vegetation model experiment to create an advanced global data–model hybrid biome reconstruction. This new palaeoecological database and global vegetation reconstruction can be used both for the purposes of validating future palaeoclimate model simulations, as well as a land cover dataset to initialise palaeoclimate modelling experiments. Our Tortonian reconstruction shows significant changes in the distribution of vegetation compared to modern natural vegetation. For example in contrast to the modern scenario in the Northern Hemisphere, boreal forests reached 80°N and temperate forests were present above 60°N. Warm–temperate forests covered much of Europe, coastal North America and South-East Asia. Our reconstruction shows a spread of temperate savanna in central USA, the Middle East and on the Tibetan Plateau. Evidence for arid deserts is sparse, with the exception of the Atacama region (South America). Areas that exhibit arid desert today in the Tortonian were instead covered by shrublands, grasslands, savannas and woodlands. The extent of tropical forests in South America was likely reduced but expanded in the Indian sub-continent and East Africa. This pattern of global vegetation in the Late Miocene suggests a warmer and wetter world, which is supported by the pattern of climate anomalies predicted by our best-fit palaeoclimate-vegetation model experiment. Global mean annual temperature may have been as much as 4.5 °C higher than present day with many regions experiencing higher than modern amounts of precipitation over the annual cycle. The pattern of temperature and precipitation change reconstructed palaeobotanically, and predicted within our climate model experiment, infers a global forcing agent on Tortonian climate (e.g. such as elevated concentrations of greenhouse gases) to explain the observed and modelled climate anomalies. This is in contrast to current proxy records of Tortonian atmospheric CO2 which range from Last Glacial Maximum to mid-20th Century levels.
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A Tortonian (Late Miocene, 11.61–7.25Ma) global vegetation reconstruction
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Matthew J. Pound, Alan M. Haywood, Ulrich Salzmann, James B. Riding, Daniel J. Lunt, Stephen J. HunterAbstract:For the Tortonian age of the Miocene Epoch (11.6–7.25 Ma) we present a global palaeobotanical and palaeoecologically-based vegetation dataset, combined with a best-fit Late Miocene climate-vegetation model experiment to create an advanced global data–model hybrid biome reconstruction. This new palaeoecological database and global vegetation reconstruction can be used both for the purposes of validating future palaeoclimate model simulations, as well as a land cover dataset to initialise palaeoclimate modelling experiments. Our Tortonian reconstruction shows significant changes in the distribution of vegetation compared to modern natural vegetation. For example in contrast to the modern scenario in the Northern Hemisphere, boreal forests reached 80°N and temperate forests were present above 60°N. Warm–temperate forests covered much of Europe, coastal North America and South-East Asia. Our reconstruction shows a spread of temperate savanna in central USA, the Middle East and on the Tibetan Plateau. Evidence for arid deserts is sparse, with the exception of the Atacama region (South America). Areas that exhibit arid desert today in the Tortonian were instead covered by shrublands, grasslands, savannas and woodlands. The extent of tropical forests in South America was likely reduced but expanded in the Indian sub-continent and East Africa. This pattern of global vegetation in the Late Miocene suggests a warmer and wetter world, which is supported by the pattern of climate anomalies predicted by our best-fit palaeoclimate-vegetation model experiment. Global mean annual temperature may have been as much as 4.5 °C higher than present day with many regions experiencing higher than modern amounts of precipitation over the annual cycle. The pattern of temperature and precipitation change reconstructed palaeobotanically, and predicted within our climate model experiment, infers a global forcing agent on Tortonian climate (e.g. such as elevated concentrations of greenhouse gases) to explain the observed and modelled climate anomalies. This is in contrast to current proxy records of Tortonian atmospheric CO2 which range from Last Glacial Maximum to mid-20th Century levels
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A Tortonian (Late Miocene, 11.61–7.25 Ma) global vegetation reconstruction
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Matthew J. Pound, Alan M. Haywood, Ulrich Salzmann, James B. Riding, Daniel J. Lunt, Stephen J. HunterAbstract:For the Tortonian age of the Miocene Epoch (11.6–7.25 Ma) we present a global palaeobotanical and palaeoecologically-based vegetation dataset, combined with a best-fit Late Miocene climate-vegetation model experiment to create an advanced global data–model hybrid biome reconstruction. This new palaeoecological database and global vegetation reconstruction can be used both for the purposes of validating future palaeoclimate model simulations, as well as a land cover dataset to initialise palaeoclimate modelling experiments. Our Tortonian reconstruction shows significant changes in the distribution of vegetation compared to modern natural vegetation. For example in contrast to the modern scenario in the Northern Hemisphere, boreal forests reached 80°N and temperate forests were present above 60°N. Warm–temperate forests covered much of Europe, coastal North America and South-East Asia. Our reconstruction shows a spread of temperate savanna in central USA, the Middle East and on the Tibetan Plateau. Evidence for arid deserts is sparse, with the exception of the Atacama region (South America). Areas that exhibit arid desert today in the Tortonian were instead covered by shrublands, grasslands, savannas and woodlands. The extent of tropical forests in South America was likely reduced but expanded in the Indian sub-continent and East Africa. This pattern of global vegetation in the Late Miocene suggests a warmer and wetter world, which is supported by the pattern of climate anomalies predicted by our best-fit palaeoclimate-vegetation model experiment. Global mean annual temperature may have been as much as 4.5 °C higher than present day with many regions experiencing higher than modern amounts of precipitation over the annual cycle. The pattern of temperature and precipitation change reconstructed palaeobotanically, and predicted within our climate model experiment, infers a global forcing agent on Tortonian climate (e.g. such as elevated concentrations of greenhouse gases) to explain the observed and modelled climate anomalies. This is in contrast to current proxy records of Tortonian atmospheric CO2 which range from Last Glacial Maximum to mid-20th Century levels.
Matthew J. Pound - One of the best experts on this subject based on the ideXlab platform.
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Late Miocene (Tortonian) dinoflagellates and sea surface parameters.
2011Co-Authors: Stephanie Emma Louise Wood, Matthew J. Pound, James B. Riding, Alan M. HaywoodAbstract:In order to understand the predictive ability of global circulation models (GCMs), many palaeoclimate studies use GCMs to simulate past climates. Evaluating these simulations requires a comprehensive view of palaeoclimate from the geological record. Many present day and Quaternary studies of dinoflagellate cysts have shown that they can be used to reconstruct past sea surface parameters (SSPs). In recent decades, dinoflagellate cysts have also proved useful for palaeoenvironmental analysis and have become a key element in reconstructing palaeoceanographic change and climate dynamics. The palaeo sea surface temperatures, salinities, sea ice cover and nutrient availability are also able to be gleaned from the distribution of dinoflagellate cysts. Dinoflagellate cyst palaeoecology is made more comprehensive for Quaternary assemblages due to the increased number of extant taxa. However, working within the constraints of the Tortonian (11.6 - 7.25 Ma), means that only a limited number of taxa are still alive today. Regardless of this, reconstructions have become more complex and representative of their time periods. The advantages of using dinoflagellate cysts as a proxy are numerous. Restrictions on data obtained from traditional micropalaeontology do not apply to dinoflagellate cysts. They are not only abundant in neritic settings and resistant to chemical dissolution, but are also extremely sensitive to small changes in nutrient availability. It is for this reason why they are excellent as a promising tool for palaeoproductivity. In this case we present an almost complete overview of global Tortonian dinoflagellate cyst distributions. We have constructed a comprehensive ArcGIS - MS Access database for the Tortonian using over 80 published studies on dinoflagellate cysts. This technique allows the distribution of individual taxa to be studied and assessed for SSPs. The ratio of Protoperidinium :Gonyaulacoid cysts at each site allows a measure of palaeoproductivity to be assessed based on Harland (1973), linking directly to climate characteristics such as surface current patterns, upwelling systems, water mass mixing, surface winds and the global carbon cycle. While also allowing the comparison of today's extant taxa to be cross referenced and start to build up palaeoceanographic environments for the Tortonian. This database combined with ongoing modelling and terrestrial proxy work is furthering our understanding of the Tortonian climate and the ability of GCMs. Harland, R. 1973. Dinoflagellate cysts and acritarchs from the Bearpaw Formation (upper Campanian) south of Alberta, Canada. Palaeontology, 16 : 665 - 706
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a Tortonian late miocene 11 61 7 25 ma global vegetation reconstruction
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Matthew J. Pound, Alan M. Haywood, Ulrich Salzmann, James B. Riding, Daniel J. Lunt, Stephen J. HunterAbstract:For the Tortonian age of the Miocene Epoch (11.6–7.25 Ma) we present a global palaeobotanical and palaeoecologically-based vegetation dataset, combined with a best-fit Late Miocene climate-vegetation model experiment to create an advanced global data–model hybrid biome reconstruction. This new palaeoecological database and global vegetation reconstruction can be used both for the purposes of validating future palaeoclimate model simulations, as well as a land cover dataset to initialise palaeoclimate modelling experiments. Our Tortonian reconstruction shows significant changes in the distribution of vegetation compared to modern natural vegetation. For example in contrast to the modern scenario in the Northern Hemisphere, boreal forests reached 80°N and temperate forests were present above 60°N. Warm–temperate forests covered much of Europe, coastal North America and South-East Asia. Our reconstruction shows a spread of temperate savanna in central USA, the Middle East and on the Tibetan Plateau. Evidence for arid deserts is sparse, with the exception of the Atacama region (South America). Areas that exhibit arid desert today in the Tortonian were instead covered by shrublands, grasslands, savannas and woodlands. The extent of tropical forests in South America was likely reduced but expanded in the Indian sub-continent and East Africa. This pattern of global vegetation in the Late Miocene suggests a warmer and wetter world, which is supported by the pattern of climate anomalies predicted by our best-fit palaeoclimate-vegetation model experiment. Global mean annual temperature may have been as much as 4.5 °C higher than present day with many regions experiencing higher than modern amounts of precipitation over the annual cycle. The pattern of temperature and precipitation change reconstructed palaeobotanically, and predicted within our climate model experiment, infers a global forcing agent on Tortonian climate (e.g. such as elevated concentrations of greenhouse gases) to explain the observed and modelled climate anomalies. This is in contrast to current proxy records of Tortonian atmospheric CO2 which range from Last Glacial Maximum to mid-20th Century levels.
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A Tortonian (Late Miocene, 11.61–7.25Ma) global vegetation reconstruction
Palaeogeography Palaeoclimatology Palaeoecology, 2011Co-Authors: Matthew J. Pound, Alan M. Haywood, Ulrich Salzmann, James B. Riding, Daniel J. Lunt, Stephen J. HunterAbstract:For the Tortonian age of the Miocene Epoch (11.6–7.25 Ma) we present a global palaeobotanical and palaeoecologically-based vegetation dataset, combined with a best-fit Late Miocene climate-vegetation model experiment to create an advanced global data–model hybrid biome reconstruction. This new palaeoecological database and global vegetation reconstruction can be used both for the purposes of validating future palaeoclimate model simulations, as well as a land cover dataset to initialise palaeoclimate modelling experiments. Our Tortonian reconstruction shows significant changes in the distribution of vegetation compared to modern natural vegetation. For example in contrast to the modern scenario in the Northern Hemisphere, boreal forests reached 80°N and temperate forests were present above 60°N. Warm–temperate forests covered much of Europe, coastal North America and South-East Asia. Our reconstruction shows a spread of temperate savanna in central USA, the Middle East and on the Tibetan Plateau. Evidence for arid deserts is sparse, with the exception of the Atacama region (South America). Areas that exhibit arid desert today in the Tortonian were instead covered by shrublands, grasslands, savannas and woodlands. The extent of tropical forests in South America was likely reduced but expanded in the Indian sub-continent and East Africa. This pattern of global vegetation in the Late Miocene suggests a warmer and wetter world, which is supported by the pattern of climate anomalies predicted by our best-fit palaeoclimate-vegetation model experiment. Global mean annual temperature may have been as much as 4.5 °C higher than present day with many regions experiencing higher than modern amounts of precipitation over the annual cycle. The pattern of temperature and precipitation change reconstructed palaeobotanically, and predicted within our climate model experiment, infers a global forcing agent on Tortonian climate (e.g. such as elevated concentrations of greenhouse gases) to explain the observed and modelled climate anomalies. This is in contrast to current proxy records of Tortonian atmospheric CO2 which range from Last Glacial Maximum to mid-20th Century levels
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A Tortonian (Late Miocene, 11.61–7.25 Ma) global vegetation reconstruction
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Matthew J. Pound, Alan M. Haywood, Ulrich Salzmann, James B. Riding, Daniel J. Lunt, Stephen J. HunterAbstract:For the Tortonian age of the Miocene Epoch (11.6–7.25 Ma) we present a global palaeobotanical and palaeoecologically-based vegetation dataset, combined with a best-fit Late Miocene climate-vegetation model experiment to create an advanced global data–model hybrid biome reconstruction. This new palaeoecological database and global vegetation reconstruction can be used both for the purposes of validating future palaeoclimate model simulations, as well as a land cover dataset to initialise palaeoclimate modelling experiments. Our Tortonian reconstruction shows significant changes in the distribution of vegetation compared to modern natural vegetation. For example in contrast to the modern scenario in the Northern Hemisphere, boreal forests reached 80°N and temperate forests were present above 60°N. Warm–temperate forests covered much of Europe, coastal North America and South-East Asia. Our reconstruction shows a spread of temperate savanna in central USA, the Middle East and on the Tibetan Plateau. Evidence for arid deserts is sparse, with the exception of the Atacama region (South America). Areas that exhibit arid desert today in the Tortonian were instead covered by shrublands, grasslands, savannas and woodlands. The extent of tropical forests in South America was likely reduced but expanded in the Indian sub-continent and East Africa. This pattern of global vegetation in the Late Miocene suggests a warmer and wetter world, which is supported by the pattern of climate anomalies predicted by our best-fit palaeoclimate-vegetation model experiment. Global mean annual temperature may have been as much as 4.5 °C higher than present day with many regions experiencing higher than modern amounts of precipitation over the annual cycle. The pattern of temperature and precipitation change reconstructed palaeobotanically, and predicted within our climate model experiment, infers a global forcing agent on Tortonian climate (e.g. such as elevated concentrations of greenhouse gases) to explain the observed and modelled climate anomalies. This is in contrast to current proxy records of Tortonian atmospheric CO2 which range from Last Glacial Maximum to mid-20th Century levels.
