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2. Comment on the Kaiho et al., paper “A forest fire and soil erosion event during the Late Devonian mass extinction” [Palaeogeography, Palaeoclimatology, Palaeoecology 392 (2013): 272–280]
- Author
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Marynowski, Leszek and Racki, Grzegorz
- Published
- 2015
- Full Text
- View/download PDF
3. Comment on the paper “Palynological records of the Permian Ecca Group (South Africa): Utilizing climatic icehouse-greenhouse signals for cross basin correlations” by K. Ruckwied, A. Götz and P. Jones (PPP, 413, 167-172, 2014)
- Author
-
Cole, Doug, primary
- Published
- 2017
- Full Text
- View/download PDF
4. Comment on the Chu et al., paper 'Lilliput effect in freshwater ostracods during the Permian–Triassic extinction' [Palaeogeography, Palaeoclimatology, Palaeoecology 435 (2015): 38–52]
- Author
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Marie-Béatrice Forel, Sylvie Crasquin, Centre de Recherche en Paléontologie - Paris (CR2P), Muséum national d'Histoire naturelle (MNHN)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de recherche sur la Paléobiodiversité et les Paléoenvironnements (CR2P), Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Université Pierre et Marie Curie - Paris 6 (UPMC)
- Subjects
Taphonomy ,Extinction ,Permian ,Anticline ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences ,Paleontology ,[SDV.BID]Life Sciences [q-bio]/Biodiversity ,Oceanography ,[SDU]Sciences of the Universe [physics] ,Genus ,Paleoclimatology ,Paleoecology ,14. Life underwater ,[SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology ,ComputingMilieux_MISCELLANEOUS ,Ecology, Evolution, Behavior and Systematics ,Geology ,Permian–Triassic extinction event ,Earth-Surface Processes - Abstract
Chu et al. (2015, Lilliput effect in freshwater ostracods during the Permian–Triassic extinction) reported a sharp decrease of the size of freshwater ostracods through the terrestrial end-Permian extinction (EPE) interval of the Dalongkou Anticline section in Northwest China. The proposed work is however unacceptable because of taxonomic and methodological issues. Most of the identifications are rejected because of too poor preservation and generic misidentifications due to the unawareness of the abundant literature published for years on Permian freshwater ostracods. The proposed analysis of the size of the misidentified genus Darwinula considers the totality of the recovered specimens but is meaningless by ignoring the aspect of the ontogenetic development of ostracods. As a consequence, the observed reduction of size of ostracods could be related to changes in the taphonomic conditions or in the proportions of juveniles under special environmental, which have already been suggested for marine ostracods through the EPE.
- Published
- 2015
5. Comment on the paper 'Palynological records of the Permian Ecca Group (South Africa): Utilizing climatic icehouse-greenhouse signals for cross basin correlations' by K. Ruckwied, A. Götz and P. Jones (PPP, 413, 167-172, 2014)
- Author
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Doug Cole
- Subjects
Palynology ,010504 meteorology & atmospheric sciences ,Permian ,Paleontology ,Greenhouse ,Structural basin ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Group (stratigraphy) ,Geochronology ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Published
- 2017
6. Population response during an Oceanic Anoxic Event: The case of Posidonotis (Bivalvia) from the Lower Jurassic of the Neuquén Basin, Argentina
- Author
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Susana E. Damborenea, Hugh C. Jenkyns, Javier Echevarría, A. H. Al-Suwaidi, Miguel O. Manceñido, Stephen P. Hesselbo, Sonia Ros-Franch, and Alberto Carlos Riccardi
- Subjects
Cronologia geològica ,010506 paleontology ,OPPORTUNISTIC SPECIES ,Fauna ,TOARCIAN OAE ,Espècies (Biologia) ,Paleontologia ,Structural basin ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,PAPER-CLAMS ,purl.org/becyt/ford/1 [https] ,purl.org/becyt/ford/1.5 [https] ,Paleontology ,Benthos ,SOUTH AMERICA ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Total organic carbon ,biology ,Hypoxia (environmental) ,Bivalvia ,biology.organism_classification ,Anoxic waters ,BIOTIC REACTIONS ,Fossil wood ,Geology - Abstract
Benthonic marine species show a wide range of biological reactions to seawater chemical changes through time, from subtle adjustments to extinction. The Early Toarcian Oceanic Anoxic Event (T-OAE) was recently recognized in the Neuquén Basin, Argentina, confirming its global scope. The event was identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13Corg) in bulk rock and fossil wood in the upper Pliensbachian–lower Toarcian interval in the Arroyo Lapa section (Neuquén). Simultaneously with collection of lithological samples, a high-resolution biostratigraphical survey was carried out, and the scarce benthonic fauna was collected in order to check the biotic response to changing marine geochemical conditions. We present here an analysis of size and abundance data from the T-OAE interval in the Neuquén Basin for the dominant bivalve species, the paper-clam Posidonotis cancellata (Leanza), and relate these data to geochemical proxies (%TOC and δ13Corg) obtained at the same locality. The abundance of P. cancellata increased when the rest of the benthos diminished, reaching a maximum at the onset level of the T-OAE, and then decreasing. Size-frequency distributions show a noteworthy lack of juvenile shells. Shell size shows a positive correlation with %TOC in the whole section, though over the T-OAE interval proper, it decreases below the level where the maximum %TOC value is attained and increases above it. Posidonotis cancellata shows features of opportunistic species, such as high tolerance to hypoxia, strong dominance in impoverished environments and a strong dependence on primary productivity, but at the same time had a reproductive strategy more similar to equilibrium species, with relatively low juvenile mortality rates. Several anatomical features suggest adaptation to permanently dysaerobic environments. The species disappeared just before the minimum negative carbon-isotope value was reached; and by the same time the genus became extinct worldwide. Fil: Ros Franch, Sonia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Echevarría, Javier. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Damborenea, Susana Ester. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Manceñido, Miguel Oscar. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Jenkyns, Hugh C.. University of Oxford; Reino Unido Fil: Al Suwaidi, Aisha. Khalifa University Of Science And Technology; Emiratos Arabes Unidos Fil: Hesselbo, Stephen P.. University of Exeter; Reino Unido Fil: Riccardi, Alberto Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina
- Published
- 2019
7. Cyclostratigraphy and astrochronology: Case studies from China
- Author
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James G. Ogg, David B. Kemp, and Chunju Huang
- Subjects
Astrochronology ,010506 paleontology ,Milankovitch cycles ,Invited Research Papers ,Paleontology ,Climate change ,Structural basin ,Cyclostratigraphy ,010502 geochemistry & geophysics ,Oceanography ,Orbital cycles ,01 natural sciences ,Sequences ,Geologic time scale ,Paleoclimatology ,Astronomical time scale ,Palaeogeography ,Ecology, Evolution, Behavior and Systematics ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
A high-precision geologic time scale is the essential key for understanding the Earth’s evolutionary history and geologic processes. Astronomical tuning of orbitally forced stratigraphic records to construct high-resolution Astronomical Time Scales (ATS) has led to a progressive refinement of the geologic time scale over the past two decades. In turn, these studies provide new insights regarding the durations and rates of major Earth events, evolutionary processes, and climate changes, all of which provide a scientific basis for contextualizing and predicting future global change trends. South China hosts some of the best-exposed and well-dated Neoproterozoic through Mesozoic stratigraphic sections in the world; many of which are suitable for cyclostratigraphy and calibrating the geologic time scale. In North China, several Cenozoic oil-bearing basins have deep boreholes with continuous sampling and/or well logging that enable derivation of astronomically tuned time scales for an improved understanding of basin evolution and hydrocarbon generation. This Special Issue focuses on case studies of astrochronology and applied cyclostratigraphy research using reference sections within China. In this introductory overview, we: (1) summarize all existing astrochronology studies of the Neoproterozoic through Cenozoic sections within China that have been used to enhance the international geologic time scale, (2) examine briefly the astronomically forced paleoclimate information recorded in various depositional systems and the modern techniques employed to analyze the periodicity of these signals encoded within the sedimentary record, and (3) summarize the 20 contributions to this Special Issue of Palaeogeography, Palaeoclimatology, Palaeoecology on 'Cyclostratigraphy and Astrochronology: Case studies from China’.
- Published
- 2020
8. Editorial preface to special issue: Neogene-Quaternary changes of the Indo-Pacific Warm Pool encompassing oceanic, hydrologic and carbon cycles, and their implications for future change.
- Author
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Huang, Jie, Xiong, Zhifang, Dang, Haowen, and Opdyke, Bradley
- Subjects
- *
HYDROLOGIC cycle , *CARBON cycle , *CLIMATE change , *HYDROGRAPHY , *BIOLOGICAL productivity , *GLOBAL warming ,TROPICAL climate - Abstract
The Indo-Pacific Warm Pool (IPWP) is the primary supplier of heat and moisture to the global atmosphere, and exerts a significant impact on tropical and worldwide climate variability. This special issue expands our understanding of the paleoceanographic and paleoclimatic evolution of the IPWP since Neogene times with implications for understanding future change. It contains fifteen research articles addressing two primary themes: (1) Ocean-atmosphere coupled processes via the ocean water-column, sea surface, atmospheric evaporation/precipitation; and (2) Sediment source-to-sink and biogeochemical carbon-cycles, and their interactions with oceanographic, hydrological, tectonic and other factors. These contributions improve our understanding of thermocline temperature, salinity, oxygenation, hydrography, carbon cycle, biological productivity, and sedimentary response in the IPWP across Neogene and Quaternary time scales, as well as aiding in the forecast of future climate responses in the context of current global warming. The special issue will capture the attention of geologists, climatologists, and anybody else interested in global climate change. • This is the editorial preface for the VSI on Indo-Pacific Warm Pool. • 15 papers are included and shortly introduced. • Two themes are included. • The 15 papers provide new views on paleoceanographic and paleoclimatic changes in the Indo-Pacific Warm Pool. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
9. A tale from the Neogene savanna: Paleoecology of the hipparion fauna in the northern Black Sea region during the late Miocene.
- Author
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Rivals, Florent, Belyaev, Ruslan I., Basova, Vera B., and Prilepskaya, Natalya E.
- Subjects
- *
NEOGENE Period , *MIOCENE Epoch , *DIETARY patterns , *LIONS , *SAVANNAS , *FOOD habits , *RHINOCEROSES , *PALEOECOLOGY - Abstract
This paper investigates the paleoecology of the Neogene savanna in the northern Black Sea region during the late Miocene, focusing on the " Hipparion fauna" that inhabited the area. The study explores the dietary habits of various ungulates and carnivorans through dental mesowear and microwear patterns, aiming to infer aspects of trophic interactions and ecological niches occupied by different species. The research covers three sites that span from the late Khersonian (late Tortonian; MN11) to the late Maeotian (Messinian; MN13) stages. We report catastrophic bone accumulation at the Grebeniki and Cioburciu 1 sites. Results indicate a significant dietary diversity that is challenging the traditional assumptions about the " Hipparion fauna". Rhinoceroses, specifically Chilotherium schlosseri and Aceratherium incisivum , are identified as true grazers, contradicting previous beliefs about their preference for forested or swampy ecosystems. The hipparions, traditionally considered open landscape foragers, are revealed as browsers or mixed-feeders. The study also highlights the diverse dietary traits among small antelopes, giraffids, and suids, emphasizing their adaptability to various environmental conditions. Data obtained on the hyaenid Adcrocuta eximia indicate a diet very similar to that of the bone-cracking spotted hyena. The microwear pattern of the cubs was very different from both adults and any other carnivorans used for comparison. The large felid Machairodus copei was characterized by a hypercarnivorous diet similar to lions, while smaller-size Ictitherium viverrinum was characterized by a more opportunistic feeding strategy. These findings suggest similarities and differences in feeding patterns between modern and Neogene savanna mammals. The presence of both grazing and browsing herbivores indicates a more heterogeneous landscape, with a mixture of open grasslands and denser vegetation. Additionally, the paper provides insights into the changing paleoenvironment, suggesting a transition from wooded grasslands to open landscapes during the late Miocene. Overall, this research contributes to a comprehensive understanding of the Neogene savanna ecosystem and challenges existing perceptions of the paleoecology of the " Hipparion fauna" in the northern Black Sea region. • Dietary habits of the ungulates and carnivorans in the Eastern Paratethys region • High dietary diversity among Neogene savanna herbivores • True grazers among rhinoceroses; browsers and mixed-feeders among hipparions • Diverse dietary traits among small antelopes, giraffids, and suids. • Hyaenids had a strictly carnivorous diet while the other carnivorans had a broader diet. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
10. Quantitative palaeogeographical reconstruction of the North China Block during the Carboniferous and Permian transition: Implications for coal accumulation and source rock development.
- Author
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Shen, Bo-heng, Hou, Zhang-shuai, Wang, Xiang-dong, Wu, Qiong, Zhang, Hua, Chen, Jitao, Yuan, Dong-xun, Hu, Bing, Sun, Bei-lei, and Shen, Shu-zhong
- Subjects
- *
COAL reserves , *TIDAL flats , *COAL , *CLASTIC rocks , *CARBONATE rocks , *COASTAL development - Abstract
The Carboniferous-Permian strata of the North China Block (NCB) contain significant economic reserves of coal and gas. In this paper, a comprehensive dataset comprising 401 stratigraphic sections encompassing the Carboniferous-Permian transition in the NCB is compiled from the OneStratigraphy and Geobiodiversity databases. We conducted quantitative analyses of this dataset using ArcGIS and GPlates software, and utilized an up to date plate motion model, to perform a dynamic palaeogeographical reconstruction. The spatio-temporal distribution of depositional facies were also analysed, including basement terranes, fluvio-lacustrine settings, swamps, shorelines, tidal flats, and carbonate platforms. Our reconstructions reveal that the NCB was flanked by basement areas of the Yinshan-Yanshan landmass in the north and the Qinling-Dabie landmass in the south. Peat (coal) deposition occurred across a range of terrestrial to coastal environments, including fluvio-lacustrine settings, deltas, shorelines and tidal flats. Carbonaceous and organic-rich clastic rocks also developed in these areas while organic-rich carbonate rocks were primarily deposited in carbonate platform. The conditions conducive to peat (coal) formation were intricately connected to eustatic fluctuations, which resulted in frequent transgressions and regressions. The sea-level fluctuations during the Pennsylvanian might be, in part, a response to both the waxing and waning of continental ice sheets and tectonic process in the northern margin of the NCB. In contrast, sea-level changes during the early Permian were probably controlled by the tectonic process only. This paper provides a state-of-the-art review of palaeogeographical evolution of the NCB during the Carboniferous and Permian transition, in response to eustatic and palaeoclimate change, and sheds light on resource accumulation based on quantitative analyses. • Carboniferous-Permian palaeogeography of the NCB were quantitatively reconstructed based on 401 sections. • The western, central, and southeastern parts of the NCB exhibit most significant potential for exploring coal and source rocks. • The sea-level fluctuations of the NCB were in response to the global palaeoclimate changes and the regional tectonic process. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
11. Population response during an Oceanic Anoxic Event: The case of Posidonotis (Bivalvia) from the Lower Jurassic of the Neuquén Basin, Argentina.
- Author
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Ros-Franch, Sonia, Echevarría, Javier, Damborenea, Susana E., Manceñido, Miguel O., Jenkyns, Hugh C., Al-Suwaidi, Aisha, Hesselbo, Stephen P., and Riccardi, Alberto C.
- Subjects
- *
CHEMOSTRATIGRAPHY , *FOSSIL trees , *JURASSIC Period , *BIVALVES , *CHEMICAL reactions , *POPULATION , *BENTHOS - Abstract
Benthonic marine species show a wide range of biological reactions to seawater chemical changes through time, from subtle adjustments to extinction. The Early Toarcian Oceanic Anoxic Event (T-OAE) was recently recognized in the Neuquén Basin, Argentina, confirming its global scope. The event was identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13C org) in bulk rock and fossil wood in the upper Pliensbachian–lower Toarcian interval in the Arroyo Lapa section (Neuquén). Simultaneously with collection of lithological samples, a high-resolution biostratigraphical survey was carried out, and the scarce benthonic fauna was collected in order to check the biotic response to changing marine geochemical conditions. We present here an analysis of size and abundance data from the T-OAE interval in the Neuquén Basin for the dominant bivalve species, the paper-clam Posidonotis cancellata (Leanza), and relate these data to geochemical proxies (%TOC and δ13C org) obtained at the same locality. The abundance of P. cancellata increased when the rest of the benthos diminished, reaching a maximum at the onset level of the T-OAE, and then decreasing. Size-frequency distributions show a noteworthy lack of juvenile shells. Shell size shows a positive correlation with %TOC in the whole section, though over the T-OAE interval proper, it decreases below the level where the maximum %TOC value is attained and increases above it. Posidonotis cancellata shows features of opportunistic species, such as high tolerance to hypoxia, strong dominance in impoverished environments and a strong dependence on primary productivity, but at the same time had a reproductive strategy more similar to equilibrium species, with relatively low juvenile mortality rates. Several anatomical features suggest adaptation to permanently dysaerobic environments. The species disappeared just before the minimum negative carbon-isotope value was reached; and by the same time the genus became extinct worldwide. Unlabelled Image • P. cancellata size and abundance data from Toarcian relate to OAE geochemical proxies. • Shell size correlates positively with %TOC, probably linked to primary productivity. • Maximum abundance at the onset of the T-OAE, and then decreasing until its extinction. • P. cancellata shows opportunistic species features, but with a low juvenile mortality. • P. cancellata anatomical features suggest adaptation to dysaerobic environments. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
12. Editorial preface to special issue: Recovery of marine ecosystem after the Permian-Triassic mass extinction: New progress from South China.
- Author
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Song, Huyue, Hu, Shixue, Benton, Michael, and Jiang, Dayong
- Subjects
- *
MASS extinctions , *COPROLITES , *VOLCANIC eruptions , *MARINE sediments , *BIOSTRATIGRAPHY , *BIOTIC communities , *BIOMARKERS , *MARINE ecology - Abstract
The end Permian to Middle Triassic interval (∼252–242 Ma) witnessed the largest marine mass extinction and the most delayed recovery in the Phanerozoic. The nature and mechanism of these biotic and environmental changes remain unclear. This special issue focuses on the Triassic marine sediments in South China, which provide unique documentation of the collapse and recovery of marine ecosystems. Six papers focus on biotic changes and their ecological significance in Early and Middle Triassic times, documenting evidence from bivalves, marine reptiles, stromatolites, hybodontid teeth, vertebrate coprolites, and other putative fossils. Two papers study conodont biostratigraphy across the Permian-Triassic boundary (PTB) and Induan-Olenekian boundary. Two papers reconstruct the palaeoenvironments of the Early Triassic Chaohu Fauna and Middle Triassic Luoping Biota. Two further papers present new marine δ13C records and biomarker data and link them to volcanic eruptions in Early Triassic times. These new findings are important for understanding the co-evolution between biotic and environmental changes in the aftermath of Permian-Triassic boundary mass extinction. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
13. Editorial Preface to Special Issue: The radiations within the Great Ordovician Biodiversification Event.
- Author
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Servais, Thomas, Harper, David A.T., and Wang, Wenhui
- Subjects
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ORDOVICIAN Period , *MARINE biodiversity , *CAMBRIAN explosion (Evolution) , *MARINE biology , *RADIATION - Abstract
In order to improve our understanding of the biodiversification of marine life that took place during the early Palaeozoic, we present this special issue focused on the Ordovician radiations. The Great Ordovician Biodiversification Event (GOBE) is a conceptual term that is today largely used to refer to the most significant increase of marine biodiversity of the Phanerozoic that occurred during the Ordovician Period between 485 and 444 Ma. Some authors, focusing on taxonomic diversity counts of selected groups, understand the GOBE to be related to a single dramatic biodiversification event of short duration in the Darriwilian Stage of the Middle Ordovician Series between 470 and 455 Ma, whereas others follow the more traditional view and consider the Ordovician biodiversification as an aggregation of radiation events capturing a large and complex increase of taxonomic diversity but also ecological complexity of marine organisms covering the entire Ordovician. This special issue features 16 selected papers that provide different perspectives on these Ordovician biodiversification events, illustrating a variety of radiations occurring during the Ordovician Period. Several papers focus on the available biodiversity datasets and their biases, and the difficulty to distinguish and interpret the various regional and global scales. It becomes clear that the Cambrian and Ordovician radiations are artificially separated by a late Cambrian 'Furongian Biodiversity Gap' and that a single long-term early Palaeozoic radiation is more and more visible. A few papers provide additional data on this crucial interval across the Cambrian-Ordovician boundary displaying a much higher ecological complexity than previously assumed. Both the diversification of the plankton and the evolution of nektonic groups during the Ordovician are investigated, in papers including Computational Fluid Dynamic simulations. The virtual special issue closes with papers documenting the development of reefs during the Late Ordovician. • This is the editorial preface for the VSI on Ordovician radiations. • 16 papers are included and shortly introduced. • One review paper is included. • The 16 papers provide new views on the Ordovician radiations. • They cover intervals from the late Cambrian to early Silurian. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
14. Periodic hydroclimate variations during the first half of the Holocene in the Luoyang Basin: Evidence from the Tiancun paleolake sedimentary sequence.
- Author
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Chen, Liang, Feng, Zhaodong, Zhang, Yangyang, Li, Hongbin, Liu, Chang, Wang, Xin, and Zhou, Xuewen
- Subjects
- *
STALACTITES & stalagmites , *HOLOCENE Epoch , *SOLAR activity , *CLIMATE change , *SOIL moisture , *SOUTHERN oscillation ,EL Nino - Abstract
The periodicities of the climate change have long been explored by researchers not only because they reflect the inherent characteristics of the climate systems, but also because they are the foundations of climate-change predictability. This paper reports the periodicities of the hydroclimate variations reconstructed from a lacustrine sequence at Tiancun section (TC section) in the Luoyang Basin within the Central Plains of China and the sequence covers the first half of the Holocene. Our reconstruction shows that the hydroclimate variations at the TC section during the period from ∼10,135 and ∼ 5890 cal. yr BP were well corresponding with the effective soil moisture variations recorded by the stalagmite δ13C sequence at the Magou Cave. This corresponding relationship suggests that when the effective soil moisture increases (i.e., more negative δ13C values), the ratio of evaporation over precipitation in the paleolake at the TC section decreased, resulting in lower CaCO 3 content. It also suggests that when the effective soil moisture increases, more inflowing water entered the paleolake, resulting in coarser sediments. Our reconstruction also shows that the hydroclimate variations or lake level variations in the Luoyang Basin were characterized by millennial-scale quasi-periodicities that were most likely paced by the changes in ITCZ (Inter-tropical Convergent Zone) position and also by alterations in ENSO-like phase. And, both (ITCZ and ENSO) were most likely regulated by the solar activity. Our further analysis shows that the hydroclimate in the Luoyang Basin also experienced centennial-scale variations. Specifically, the grain size data express the following cycles: 692-year, 538-year, 217-year, 170-year and 123-year, all at the 99% confidence level. And, the CaCO 3 content data express the following cycles: 202-year, 184-year, 169-year and 85-year, all at the 99% confidence level. These cycles are approximately coincident with the widely-reported solar-activity cycles. • This paper reports the periodicities of the hydroclimate variations reconstructed from a lacustrine sequence in the Central Plains of China and the sequence covers the first half of the Holocene. • The hydroclimate variations were primarily paced by changes in ITCZ position and also by alterations in ENSO-like phase. And, both (ITCZ and ENSO) were most likely regulated by solar activity. • The centennial-scale hydroclimate variations were approximately coincident with the widely-reported solar-activity cycles. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
15. Introduction to special issue: Environmental and climatic change records in coral reefs of the South China Sea during the Holocene.
- Author
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Yang, Hongqiang, Deng, Wenfeng, Yan, Hong, and Zhang, Feifei
- Subjects
- *
CORALS , *CLIMATE change , *CORAL reefs & islands , *HOLOCENE Epoch , *SOUTHERN oscillation , *PALEOCLIMATOLOGY - Abstract
Focusing on the evolution of coral reefs in the South China Sea, this special issue is dedicated to enhancing our understanding of Holocene environmental and climate changes in the region and their driving mechanisms. It comprises twenty-four papers organised into seven themes: (1) Palaeoclimate and palaeoenvironment evolution recorded by coral reefs; (2) Palaeo-ENSO activity recorded by coral reefs; (3) Palaeo-storm activity recorded by coral reefs; (4) The formation and evolution of coral reefs; (5) Carbonate diagenesis in coral reefs; (6) The application of new geochemical record indicators to coral reefs; and (7) Lipid biomarker records in coral reefs. This special issue provides an improved understanding of Holocene paleoclimates and paleoenvironments within the South China Sea, and the development of its coral reefs. It is hoped that these findings will deepen our knowledge of the natural and anthropogenic processes that contribute to climate and environmental change in the region, and aid the long-term protection of coral reef systems. • This special issue on recent advances of coral reefs in the South China Sea comprises twenty-four papers. • This special issue focuses on the evolution of coral reefs and their records on paleoenvironmental and paleoclimate changes. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
16. 10Be exposure age data reveals last Glacial ice sheet histories in the Larsemann Hills of East Antarctica.
- Author
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Chen, Luming, Zhang, Zhigang, Guo, Jingxue, Li, Lin, Tang, Xueyuan, Zhao, Dan, Zhang, Hongmei, and Lin, Yi
- Subjects
- *
LAST Glacial Maximum , *COSMOGENIC nuclides , *GLACIATION , *ICE shelves , *BEDROCK - Abstract
The Larsemann Hills, near Prydz Bay is a key region to understand past glacial dynamics in East Antarctica. However, multi-proxy dating constraints for this area indicate an uncertain chronology for deglaciation history during the Last Glacial Period (LGP). In this paper, we report two 26Al exposure ages and eighteen 10Be exposure ages for bedrock samples to better understand past glacial histories. The minimum exposure ages range from 82.84 ± 4.67 ka to 15.1 ± 1.95 ka corresponding to Marine Isotope Stages (MIS) 5–2, and fourteen of these samples date from before the global Last Glacial Maximum (c. 19–26.5 ka). Analysis of 10Be and 26Al concentrations implies a complex deglaciation history, and surface lowering of bedrock may have caused systematic age underestimation. Further comparisons between two adjacent regions in the Mirror Peninsula reveal two major deglaciations involving the Lambert Glacier / Amery Ice Shelf System dated at 61.78 ka to 82.84 ka and 21.98 ka to 49.5 ka during the LGP. • We present new evidence for studying glacial history of Larsemann Hills, Antarctica. • Cosmogenic nuclides 10Be and 26Al dating method is applied for better analysis. • Two major deglaciation events occurred regionally within MIS 2–3 and MIS 4–5. • The exposure age and elevation show a highly significant positive correlation. • Multi-proxy and adjacent evidence are summarized and compared with this study. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
17. Ornithogenic sedimentary profiles of n-alkanes and PAHs constrain breeding penguin population dynamics at Cape Bird, Ross Island, Antarctica, over the past 1,500 years.
- Author
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Liu, Zhixiang, Nie, Yaguang, Wang, Ruwei, Huang, Qing, Yan, Hong, and Wong, Ming Hung
- Subjects
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ANTARCTIC oscillation , *COLONIAL birds , *POLYCYCLIC aromatic hydrocarbons , *POPULATION dynamics , *SEA ice , *BIRD populations ,EL Nino - Abstract
Ornithogenic sediment may contain important paleoecological information concerning past bird population dynamics. In this paper, we analyse the distribution of n -alkanes and polycyclic aromatic hydrocarbons (PAHs) in two sedimentary profiles collected from abandoned penguin colonies at Cape Bird, Ross Island, Antarctica. The geochronology of the sediment profiles was determined using 210Pb and AMS 14C dating techniques, and spans the past 1500 years. We observe low levels of n -alkanes (0.93–2.67 μg g−1) and PAHs (20.5–46.8 ng g−1) concentrations dominated by short-chain n -alkanes, low-molecular-weight and alkyl PAHs. Principal Component Analysis (PCA) shows that the PC 1 scores for n -alkanes and PAHs are significantly correlated with the input intensity of penguin guano and penguin bioelements. Using these proxies in combination with Generalized Additive Model (GAM), we reveal that breeding penguin population growth reaches a historical peak during the Medieval Climate Anomaly (MCA) prior to 1550 CE. This growth in population size corresponds to the extent of sea ice cover and the activity of the local atmospheric-ocean circulation. Warming induced by El Niño and the positive phase of the Southern Annular Mode, along with the expansion of ice-free zones and increased oceanic nutrient and food availability, are considered primary factors contributing to the growth of breeding penguin populations. Additionally, variations in sea ice extent and Amundsen Sea Low significantly influence penguin population dynamics. Our study suggests that n -alkanes and PAHs may be valuable organic proxies for reconstructing historical changes in breeding penguin populations, with the local sea ice extent and atmospheric-oceanic circulation exerting a major influence on Antarctic penguin population dynamics. [Display omitted] • n -Alkanes and PAHs can function as proxy indicators for historical penguin guano input. • PC 1 scores for n -alkanes and PAHs correlate with guano input intensity metrics and bioelements. • Penguin population significantly increase in mid Cape Bird during the Medieval Climate Anomaly. • Atmospheric-ocean circulation influences penguin population dynamics. [ABSTRACT FROM AUTHOR]
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- 2024
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18. Reconstruction of paleowind direction in the Qinghai Lake area during the last deglacial: Insights from anisotropy of magnetic susceptibility.
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Xie, Hao, Liu, Caicai, Zhang, Huiping, Zhang, Zhuqi, Xu, Hongyan, and Wei, Xiaotong
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PARTICLE size distribution , *MAGNETIC anisotropy , *ATMOSPHERIC circulation , *MAGNETIC traps , *MAGNETIC susceptibility - Abstract
The Qinghai Lake is located near the junction of the East Asian summer monsoon (EASM), East Asian winter monsoon (EAWM), and Westerlies. The aeolian deposits around Qinghai Lake hold significant value in tracking the paleowind direction, which is crucial to reconstruct paleo-atmospheric circulations. In this paper, a systematic study of anisotropy of magnetic susceptibility (AMS), rock and environmental magnetism, grain size distribution, and X-ray diffraction was conducted on a loess sequence (named Heimahe) in the Qinghai Lake area. The AMS results of the Heimahe section reveal two prevailing winds of NE-SW and NW-SE orientations during the last deglacial in the Qinghai Lake area. Grain size distribution and mineral composition analyses suggest that the NE-SW and NW-SE winds are respectively associated with the winter monsoon and the Westerlies. Moreover, the variations in magnetic lineation as well as other AMS parameters indicate that the dominant paleowind direction in the Qinghai Lake region during the last deglacial changed periodically with a ∼ 300 yr frequency. It appears that magnetic fabric is capable of recording rapid changes in paleowind direction. • Heimahe section recorded two groups of magnetic lineations in NW-SE and NE-SW. • NW-SE and NE-SW lineations respectively correspond to Westerlies and Winter monsoon. • Westerlies and Winter monsoon alternately prevailed in Qinghai Lake area in 13–11 ka. • The dominant paleowind direction changed periodically with a ∼ 300 yr frequency. • Magnetic fabric is capable of recording rapid changes in paleowind direction. [ABSTRACT FROM AUTHOR]
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- 2024
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19. Cenomanian terrestrial paleoenvironments from the Bohemian Cretaceous Basin in Central Europe and their implications for angiosperm paleoecology.
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Kvaček, Jiří, Svobodová, Marcela, Čepičková, Jana, Veselá, Veronika, Špičáková, Lenka, Uličný, David, Teodoridis, Vasilis, Dašková, Jiřina, Mendes, Mário Miguel, and Zahajská, Petra
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ALLUVIAL plains , *MEANDERING rivers , *BRAIDED rivers , *SALT marshes , *GEOCHEMISTRY - Abstract
In this paper, we reconstruct the vegetation communities of five terrestrial paleoenvironments from the Cretaceous (Cenomanian) Peruc-Korycany Formation of the Bohemian Cretaceous Basin in Czechia. Reconstructions are based on a synthesis of numerous studies of paleobotany, palynology, paleoecology, sedimentology and geochemistry analyses. Ordered in a transect from coastal marine settings to elevated hinterland regions, paleoenvironments and plant assemblages are reconstructed as follows: (1) Saltmarsh vegetation comprising a Frenelopsis-Classopollis assemblage; (2) Coastal freshwater swamp vegetation comprising a Cunninghamites-Taxodiaceaepollenites assemblage; (3) Meandering river floodplain vegetation comprising a Myrtophyllum - Perucipollis assemblage; (4) Braided river floodplain vegetation comprising a Eucalyptolaurus-Mauldinia assemblage; and (5) Vegetation of drier upland areas comprising fern prairies with angiosperms and Bennettitales - a Zamites - Ephedripites assemblage. Our study shows that in Cenomanian times, angiosperms were diversified, particularly in alluvial plains, where lauroid and platanoid angiosperms prevailed. Comparison of these Cenomanian paleoenvironments in Czechia with other Cenomanian paleoenvironments across Europe show a widespread dominance of angiosperms in the vegetation of alluvial plains across much of the continent. This contrasts with Barremian-Albian times when angiosperms occupied only disturbed habitats, and our findings suggest that angiosperm exchanged a ruderal (disturbed) strategy for a competitive strategy during the Albian-Cenomanian transition. Conversely, conifers dominated alluvial plains in Early Cretaceous times, while they rose to dominate saltmarshes and swamps in the Bohemian Cenomanian, exchanging a competitive strategy for a stress-tolerant strategy. • Five typical Cenomanian palaeoenvironments are described in Central Europe. • The study is based on plant macro-, meso- and microfossils. • Reconstructions of Cenomanian palaeoenvironments are provided. • Gradual expansion of angiosperms in mid-Cretaceous environments is highlighted. • The decline of gymnosperms alongside the rise of the angiosperms is reported. [ABSTRACT FROM AUTHOR]
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- 2024
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20. The influence of North Atlantic sea surface temperature fluctuations on the climate of the Qinling-Bashan Mountains, China based on a 250 year tree-ring record.
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Cai, Qiufang, Xie, Mei, Liu, Yu, Fang, Congxi, Hao, Zhixin, Ren, Meng, Zhou, Qiuyue, Mu, Yikui, and Chen, Yufei
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OCEAN temperature , *MOUNTAIN climate , *ATLANTIC multidecadal oscillation , *CLIMATE change , *LITTLE Ice Age , *TREE-rings - Abstract
Dynamic fluctuations in sea surface temperature within the North Atlantic Ocean (NA-SST) exert a pivotal influence on global climate change. Yet, the specific impacts of these variations on the temperature shifts within the Qinling-Bashan Mountains (QBM) of China, remain to be fully elucidated. Furthermore, a debate surrounding the manifestation of the Little Ice Age (LIA) within the QBM is ongoing, primarily due to the scarcity of reliable, long-term, and high-resolution temperature records. To bridge these knowledge gaps, in this paper, we present a ∼ 250-year temperature reconstruction (Tmax 11 – 7) developed based on a tree-ring-width chronology from the QBM. The new reconstruction not only aligns with a local winter temperature reconstruction based on historical document evidence, but also reveals robust regional and hemispheric temperature signals. Intriguingly, the study shows that the warming trend observed in the QBM since the Industrial Era is less pronounced than that witnessed across China and the Northern Hemisphere. The Tmax 11 – 7 reconstruction provides a glimpse into the final stages of the LIA, highlighting a relatively colder 19 th century followed by a warmer 20 th century. Notably, the warming trend post-1970s remains within the bounds of the 250-year temperature framework. The research further uncovers that NA-SST has predominantly governed the QBM's temperature fluctuations over the past centuries, as evidenced by the tight positive correlation between Atlantic multidecadal Oscillation (AMO)/Atlantic multidecadal variability (AMV) and Tmax 11 – 7. However, this dominant influence of NA-SST was temporarily subdued between 1900 and 1930 CE due to the interference of Pacific Decadal Oscillation (PDO). This finding serves as a reminder that future temperature projections for the QBM must account not only for the primary role of NA-SST but also the modulating effects of the PDO. The study is essential for shaping effective environmental management and adaptation strategies in the region. • A ∼ 250-year temperature reconstruction is developed using tree rings from the QBM. • The QBM saw the last stage of the LIA and recent warming is within historical frame. • North Atlantic SST (NA-SST) played a positive and dominant role on QBM'S temperature changes. • Weakened NA-SST's impact on temperature in 1900–1930 CE was due to PDO's interference. [ABSTRACT FROM AUTHOR]
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- 2024
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21. Neoarchean paleosols in the Eastern Fennoscandian Shield of Central Karelia, Russia, and their paleoatmospheric implication.
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Bakaeva, Alexandra V., Chazhengina, Svetlana Y., and Svetov, Sergei A.
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PALEOPEDOLOGY , *ATMOSPHERIC oxygen , *NEOARCHAEAN , *NEOTECTONICS , *WEATHER , *TEMPERATE climate , *PROTEROZOIC Era - Abstract
Precambrian paleosols provide important evidence for deciphering ancient atmospheric conditions; however, reconstruction using the Archean–Early Proterozoic weathering crusts is challenging due to reworking by later superimposed events. In this paper, we describe 2.6 Ga paleoweathering crusts developed on ultramafic rocks recognized in the Eastern Fennoscandian Shield of northwest Karelia, Russia. Mafic index of alteration shows an increasing trend from parent rock to the paleosol and indicates moderate weathering. Geochemical and mineralogical data provide evidence for paleosol formation under anoxic acidic conditions. The results allow reconstruction of palaeoatmospheric p O 2 and p CO 2 levels estimated to be 1 × 10−4 PAL and 22 PAL, respectively. Analysis of the paleosols in the Eastern Fennoscandian Shield reveals that the anoxic weathering seems to have prevailed over Archean–Early Proterozoic interval. The study contributes to understanding of evolution of atmospheric oxygen levels and paleoenvironmental conditions prior to the Great Oxidation Event. • Neoarchean paleosols have been recognized in the Eastern Fennoscandian Shield • Pitkilampi paleosols developed under a cool to temperate and humid climate • Anoxic weathering in the Eastern Fennoscandian Shield during pre-GOE timeframe [ABSTRACT FROM AUTHOR]
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- 2024
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22. Palaeoenvironmental changes since the last deglaciation recorded at Moon Lake on the Bashang Plateau, northern China: implications for the future sustainability of regional forests.
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Yin, Zhiqiang, Jia, Hongjuan, Peng, Chao, Qin, Xiaoguang, Zhang, Hao, He, Anyuan, and Wan, Liqin
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YOUNGER Dryas , *ACCELERATOR mass spectrometry , *SUSTAINABLE forestry , *SUSTAINABILITY , *AFFORESTATION , *FOREST management - Abstract
Warming-induced ecological degradation and the continuous shrinking of lakes have been observed in the Bashang Plateau, northern China, leading to the recent demise of cultivated forests. The objective of this paper is to investigate the long-term palaeoenvironmental context of these recent changes through a multi-proxy sediment core analysis at Moon Lake to better understand forest sustainability in the future. The core chronology was determined based on seven accelerator mass spectrometry (AMS) 14C dates and covers the period from 14,000 yr BP to the present. The Moon Lake record reveals four climate stages: (1) a warm and humid period followed by a cold and arid phase corresponding to the Allerod warm period and the Younger Dryas stadial (14,000 to 11,700 yr BP), (2) a relatively warm and humid period (11,700 to 7400 yr BP), (3) a period of fluctuating dry-wet-dry changes (7400 to 4000 yr BP), and (4) a relatively arid period (4000 yr BP to present). Since 1800 yr BP, drought conditions have intensified, and significant warming and drying trends have been observed over the past 500 yr BP. This consistent warming and drying trend over the past few centuries indicate that large-scale afforestation is no longer sustainable in the Bashang region. Coupled with instrumental records of soil drying and water scarcity, our Holocene records of climate change are useful for ecological resource management and sustainable forestry planning in the region. • Study area has shown ecological degradation and continuous shrinking of lakes. • Seasonal soil drying and the death of certain artificial forests also observed. • Study investigates environmental changes since the last deglaciation. • Study explores if reforestation would be effective under future warming conditions. [ABSTRACT FROM AUTHOR]
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- 2024
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23. An end-Permian two-stage extinction pattern in the deep-water Dongpan Section, and its relationship to the migration and vertical expansion of the oxygen minimum zone in the South China Basin.
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He, Weihong, Weldon, Elizabeth A., Yang, Tinglu, Wang, Han, Xiao, Yifan, Zhang, Kexin, Peng, Xingfang, and Feng, Qinglai
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BRACHIOPODA , *OXYGEN , *BENTHOS , *BIVALVES , *FORAMINIFERA , *PLANKTON , *WATER depth - Abstract
The diversity and last appearance patterns of different taxa, inhabiting varied palaeo-water depths, can provide significant insights into the deterioration process of palaeoecosystems. This paper systematically summarizes the last appearance of the end-Permian planktons (including deep-water, intermediate-water, and shallow-water radiolarians) and benthos (including ostracods, foraminifers, brachiopods and bivalves) from Dongpan, a deep-water section of South China. Results show that the deep-water radiolarian Albaillellaria was the first order to go extinct, quickly followed by the intermediate- and shallow-water radiolarians and bottom-water ostracods and foraminifers. This was followed by the extinction of the bottom-water brachiopods and bivalves. We propose that the two-stage extinction pattern was related to the end-Permian migration and vertical expansion (both upward and downward) of an oxygen minimum zone (OMZ) along the southern margin of South China. • An end-Permian two-stage extinction pattern in deep water. • Planktons and benthos at Dongpan. • Deep-water, shallower-water, and bottom-water dwellers successively went extinct. • Extinction was related to the upward and downward migrations of an OMZ. [ABSTRACT FROM AUTHOR]
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- 2024
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24. Triassic-Jurassic evolution of the Dabashan Foreland Basin: Detrital zircon perspectives on the tectonic amalgamation of the South China and North China blocks.
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Huang, Hanyu, Chen, Anqing, Li, Yingqiang, He, Dengfa, Li, Di, Xu, Yanhua, and Gao, Jie
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ZIRCON , *OROGENIC belts , *PROVENANCE (Geology) , *TRIASSIC Period , *GEOLOGICAL time scales , *MESOZOIC Era , *TRACE elements - Abstract
The Mesozoic Dabashan Foreland Basin, a result of the Mianlue Ocean closure, formed through the collision and amalgamation of the South China and North China blocks. As such, it contains an important record of the tectonic processes leading to the formation of the Qinling Orogenic Belt; however, the timing of transition from basin to mountainous terrains remains debated. Geochronological studies indicate continental collision occurred in the mid-Permian to early Triassic, while some paleomagnetic data suggest a Middle to Late Jurassic occurrence time. Utilizing detrital zircon geochronology and trace element data, in this paper, we examine Triassic-Jurassic sediment provenance patterns during the evolution of the Dabashan Foreland Basin. Results show that in the Middle Triassic, the north Yangtze Block received detrital input from the southern margin of the North China Block. In the Late Triassic, significant tectonic inversion occurred, with detrital sources from the southern margin of North China Block, North Qinling, South Qinling, and the north Yangtze Block. During the early and Middle Jurassic, detrital sources gradually shifted to a dominance from South Qinling, indicating a phased southward migration of collisional orogenic belt sources. Combining thermal events, crustal thickness variations, and paleomagnetic data, we propose a novel model explaining oblique compression along the north Yangtze Block during the early Mesozoic. This model suggests that the Dabashan Foreland Basin likely predates the Middle Triassic, and we contend that crustal deformation and lateral shortening during Mesozoic accretionary orogeny between North China Block and South China Block may explain the debate over collision timing. • Provenance analysis dates Dabashan Foreland Basin to the Middle Triassic or earlier. • Frontal orogenic belt migration alters sediment sources to the basin. • Divergent views on collision timing may stem from crustal deformation. [ABSTRACT FROM AUTHOR]
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- 2024
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25. Rates of sedimentary organic carbon preservation in the Bering Sea and Chukchi Sea, and their response to climate change over the past 75 years.
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Huang, Dekun, Dai, Mengyao, Bao, Hongyan, Qiao, Jing, Wang, Hao, Li, Keyuan, Zhong, Qiangqiang, Zhang, Fule, and Yu, Tao
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CLIMATE change , *VOLCANIC ash, tuff, etc. , *CARBON cycle , *CARBON isotopes , *ORGANIC compounds - Abstract
The Arctic Ocean is rapidly warming. In this paper, we document changes in the source, distribution, and accumulation rate of organic matter (OM) for three sediment cores in the Bering and Chukchi seas to investigate changes to the oceanic carbon cycle over the past ∼75 years. Analyses were undertaken using bulk properties, such as total organic carbon (OC), total nitrogen (TN), stable carbon isotope (δ13C), OC to TN molar ratio (C/N), and biomarkers (lignin phenols). The OC, TN, and lignin (Σ8, in mg (g sediment)−1) contents were found to be significantly related to the fraction of sand (Sand%) as a result of sediment sorting and/or different sediment sources. Using an end-member mixing model, we estimated marine OM accounted for ∼67% of all organic matter in all cores, being the dominant source. Moreover, terrestrial OM mainly originated from angiosperm non-woody tissue, while moss contribution was negligible. In the Bering Sea shelf, OC% has not changed over time, but there have been some extreme peaks around the 1960s–1970s and in 2005, which correspond to increased terrestrial input from North American rivers. In the southern core from the Chukchi Sea, the OC% showed an apparent decrease after 2000, accompanied by an increase in sand content, likely due to enhanced delivery of volcanic rocks by the Pacific Inflow from the Bering Sea. In contrast, in the northern core from the Chukchi Sea, the OC% showed a significant increasing trend, with some peaks occurring at the same time as in the Bering Sea core. The mean increase rate was compared to the increase in Siberian riverine discharge, which both could be caused by long-term climate changes. The results highlight the regional differences in the response of OC preservation to climate change and other controlling factors. Further studies with higher spatial resolution are required to better understand the preservation of OC in response to climate change. [Display omitted] • The main vegetation source was vascular plant, contribution from moss was limited. • Marine source accounted for ∼67% of the sedimentary OC in the (sub)Arctic cores. • OC preservation changed differently in the (sub)Arctic Ocean in past decades. [ABSTRACT FROM AUTHOR]
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- 2024
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26. Success and demise of exceptionally preserved terebratulide brachiopod accumulations in a Jurassic (early Pliensbachian) tropical lagoonal setting (Southern Alps, Italy): brachiopod response to environmental changes.
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Bassi, Davide, Angiolini, Lucia, Nebelsick, James H., and Posenato, Renato
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BRACHIOPODA , *CORALLINE algae , *TROPICAL ecosystems , *MARINE habitats , *CONDITIONED response , *INCRUSTATIONS , *ECOSYSTEMS - Abstract
During the Early Jurassic, the shallow marine carbonate platforms of the western-Tethys margins were characterized by highly diverse benthos including larger foraminifera, sponges, bivalves, gastropods, brachiopods, echinoderms, and dasycladalean calcareous algae. In this paper, we document examples of such assemblages within the lower Pliensbachian part of the Rotzo Formation (upper Orbitopsella Zone) of the Southern Alps, Italy. This carbonate succession was deposited in a complex mosaic of marine and brackish habitats within a tropical lagoon of the Trento Platform area. Large terebratulide brachiopod shells form autochthonous accumulations comprising exceptionally well-preserved monospecific assemblages of Lychnothyris rotzoana. These brachiopod-bearing successions were analysed in terms of biotic components, microfacies analysis, shell biofabric (three-dimensional arrangement of skeletal elements), and taphonomic signatures to understand brachiopod response to changing conditions within a highly variable lagoonal palaeoecosystem. Findings show that terebratulide shell accumulations are dominated by adult specimens and juveniles are rare. The brachiopods thrived during low energy conditions that resulted in the accumulation of highly temporally-condensed shell beds. Stabilized by microbialite encrustations, the shells were not re-oriented during the subsequent rapid burial. The abrupt demise of these communities was possibly related to rapid environmental change, and causal factors are discussed. The medium-term response of brachiopods to the relatively instable ecosystem of the tropical lagoon shows that they were not able to adapt to continuous perturbations, and that continuing stress severely compromised the resilience of benthic taxa. • Large terebratulide brachiopods thrived in Pliensbachian lagoonal settings. • Autochthonous accumulations with abundant adults and rare juveniles. • Accumulations grew under low sedimentation rate and low hydrodynamic energy. • Stabilized by microbialites shells underwent to rapid burial and early lithification. • Unpredictable environmental changes brought about the demise of the community. [ABSTRACT FROM AUTHOR]
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- 2024
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27. Mid to late Holocene climate changes and grazing activities in northern Loess Plateau, China.
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Zhang, Yaping, Zhang, Guilin, Zhao, Keliang, Wang, Jian, Vicziany, Marika, Zhou, Xinying, and Li, Xiaoqiang
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FUNGAL spores , *GRAZING , *HOLOCENE Epoch , *BIOLOGICAL evolution , *ANIMAL culture , *CLIMATE change , *ARCHAEOLOGICAL geology - Abstract
Despite the importance of pastoralism, as an alternative or adjunct to farming in China's long history, a clear understanding of the spreading routes and mechanisms of pastoralism in China is lacking. Fungal spores can be a useful addition to zooarchaeological evidence and have been widely used to explore the origins and development of pastoralism in different regions of the globe. The northern Loess Plateau is one of the most important areas for the emergence and development of pastoralism in early China. The aim of this paper was to take the fungal spores in the Baihemiao (BHM) core that we extracted from a site in the Yulin region, combine them with the zooarchaeological records to explore their relationship with climate and environmental changes, and reconstruct the evolution of animal husbandry in the northern Loess Plateau since the mid-Holocene. The results indicate that the climatic conditions in the northern Loess Plateau during the first period of 6–4.2 ka were relatively humid, the number of domesticated herbivores was small, animal husbandry was not developed, and the spores of coprophilous fungi in the sediments mainly originated from wild herbivores. Fungal spores as well as zooarchaeological evidence reveal that cattle and sheep grazing developed rapidly in the region during the second period, c. 4.2–3 ka. We suggest that the arid climatic conditions during this period facilitated the development of pastoral activities in the northern Loess Plateau. However, this pastoral economy gradually weakened after 1.2 ka. • Sporormiella suggests a high volume of herbivore activities in the Baihemiao area in 6–4.2 ka. • Fungal spores and zooarchaeological record from the archaeological sites indicate that grazing activity was strong in 4.2-3 ka. • Arid climatic conditions facilitated the development of pastoral activities in the northern Loess Plateau in 4.2–3 ka. • Pastoralism weakened and declined during the period from 3 ka to 1.2 ka. [ABSTRACT FROM AUTHOR]
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- 2024
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28. The Quaternary record of fossil bats in the Iberian Peninsula and the Balearic Islands: Palaeobiogeographical changes and palaeoenvironmental implications.
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Galán, Julia, López-García, Juan Manuel, Cuenca-Bescós, Gloria, and Sevilla, Paloma
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FOSSILS , *LAST Glacial Maximum , *BATS , *BAT conservation , *HORSESHOE bats , *SPELEOTHEMS , *STALACTITES & stalagmites - Abstract
Bats are a highly diversified order of mammals found all over the world; however, their population size and distribution are decreasing rapidly in Europe nowadays. The study of ancient bat populations by means of their fossil record is a valuable source of contextual information for modern bat conservation studies. This paper is a comprehensive review of published bat records in the Iberian Peninsula and the Balearic Islands through Quaternary times, representing the first attempt to update and standardize the knowledge of chiropters in southwestern Europe during this time period. The main goal is to identify changes in bat assemblages that might be correlatable to palaeoclimate and palaeoenvironmental changes. Our data show that the Quaternary record of bats in the area is fragmentary and strongly dependent on the presence of karstic cavities. Thus, a strong preservation bias towards colonial cave-dwelling bats exists, and species with alternative ecological requirements are under-represented. Nevertheless, this work reveals that most of the bats inhabiting the area today were already present in the region from at least the Middle Pleistocene. Interestingly, we observe a frequent association between certain cave-dwelling bats (i.e., Rhinolophus ferrumequinum , Miniopterus schreibersii , Myotis myotis and M. blythii) that is still observed in many caves today; this reflects a stable ecology that has remained undisturbed despite past climatic changes. Within the well-documented periods at the end of the Late Pleistocene and the Holocene, a reduction in some common components of Quaternary assemblages (Rhinolophus species and M. schreibersii) is observed, coinciding with the Late Glacial Maximum and the Northgrippian Neoglacial (a cooling event in the Holocene). Finally, the Balearic record shows interesting palaeobiogeographical characteristics, including some eastern taxa absent in the Iberian Peninsula (Rhinolophus variabilis and R. cf. blasii) as well as an unusual abundance of Rhinolophus hipposideros. • Most extant bats in the Iberian Peninsula were already present there ca. 600 ka. • A strong bias towards colonial, cave bats counting exists within the fossil record. • Three Mediterranean cave bats associate stably despite Quaternary climate shifts. • The Last Glacial Maximum and the Northgrippian Neoglacial events left a mark. • Two oriental taxa and higher reports on Rhinolophus for the Balearic fossil bats. [ABSTRACT FROM AUTHOR]
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- 2024
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29. On the timing of the opening of Western Pacific's back-arc seas: Data from Sr, O and C isotopes in Miocene molluscs of Sakhalin and Hokkaido.
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Zakharov, Yuri D., Kuznetsov, Anton B., Khudik, Vladimir D., Gavrilova, Anastasia A., Smyshlyaeva, Olga P., and Kiriyenko, Alexandra P.
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MIOCENE Epoch , *BACK-arc basins , *ISOTOPES , *PALEOGENE , *MOLLUSKS , *NEOGENE Period , *EOCENE Epoch - Abstract
This study presents Sr-isotope data to determine the stage affiliation of different parts of the Miocene Sertunaiskaya and Kurasiyskaya formations in Sakhalin, as well as the upper part of the Togeshita Formation in Hokkaido. Additionally, it confirms a diachronous boundary between the Sertunaiskaya and Kurasiyskaya formations. The data received will be useful for globally correlating the Miocene formations of the Sakhalin-Hokkaido area. The study indicates that the Japan and Kuril back-arc basins in the Western Pacific underwent their final opening stages during the Middle Miocene (18.1–17.7 and 15.9–14.2 Ma, respectively), as determined by the SIS method. This process was likely influenced by both global and local factors. One of the local influences on the formation of back-arc basins in the Western Pacific appears to be the influx of cool boreal waters, as indicated by the δ18O signals. The Miocene data from the Sakhalin-Hokkaido area, including evidence from Sr, O, and C isotopes, combined with corresponding paleontological, stratigraphic, palaeomagnetic, and palaeobiogeographic data from the Paleogene and Neogene, provide a four-stage chronological sequence of events related to the opening of the Western Pacific's back-arc seas. This paper presents original information on the Miocene C-isotope excursion in the Western Pacific, which are correlated with the Monterey Event. Recent data on this topic may have enhanced our comprehension of the conditions required for the formation of hydrocarbons, which are found in substantial amounts in the Miocene of northern Sakhalin and Hokkaido. • The SIS method enables the identification of the stage affiliation of Miocene formations in Sakhalin and Hokkaido. • Miocene molluscs were analysed for O- and Sr-isotopes to differentiate temperature changes caused by local and global influences. • The Japan back-arc basin may have begun to form in the late Ypresian of the Eocene. • O-isotope analyses indicate that cool boreal waters entered the Japan basin around 18–17 Ma and the Kuril Basin around 15–14 Ma, which may correspond to their eventual opening. [ABSTRACT FROM AUTHOR]
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- 2024
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30. Evolution of the northward subduction of the Neo-Tethys: Implications of geochemistry of Cretaceous arc volcanics in Qinghai-Tibetan Plateau.
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Ran, Meng-lan, Kang, Zhi-qiang, Xu, Ji-feng, Yang, Feng, Jiang, Zi-qi, Li, Qiang, Wei, Nai-shao, Wei, Tian-wei, and Liu, Di
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SUBDUCTION , *GEOCHEMISTRY , *VOLCANIC ash, tuff, etc. , *ANDESITE - Abstract
Abstract The subduction history of the Neo-Tethys is critical for understanding the early-stage tectonic evolution of the Qinghai–Tibetan Plateau. Arc volcanics, which usually record the subduction process, thus can help trace the evolution of the Neo-Tethys. In this paper, we report for the first time zircon LA-ICP-MS U-Pb ages, whole-rock major and trace element geochemistry, as well as Sr–Nd–Hf isotopic data for the volcanic rocks from the Danshiting Formation at the southern edge of the Lhasa Terrane. Two samples collected from the Danshiting Formation volcanic rocks yield zircon U-Pb ages of 97.1 ± 0.8 Ma and 90.1 ± 0.7 Ma, respectively. The volcanic rocks of the Danshiting Formation are composed dominantly of basalts and andesites characterized by depletion of high-field-strength elements, low (87Sr/86Sr) i ratios (0.7042–0.7045), high ε Nd (t) (+2.1 to +2.7) and high ε Hf (t) values (mean + 11.6). These rocks show geochemical affinity of arc volcanic rocks. The volcanic rocks of the Danshiting Formation may have formed during the northward subduction of the Neo-Tethys. This paper, combined with the previous data, briefly divide the northward subduction of the Neo-Tethys into four periods: the Jurassic (195–150 Ma), when the magmatic activity was controlled by the northward high-angle subduction of the Neo-Tethys that produced volcanics of the Yeba and Bima formations; the Late Jurassic to Early Cretaceous (150–110 Ma), when the Neo-Tethys subducted at low-angles; the Late Cretaceous (110–80 Ma), when subduction was of the Andean-type and produced volcanic rocks of the Danshiting Formation; the Paleogene (70–40 Ma), when there was transition from ocean-to-continent subduction to continent–continent collision that produced volcanic rocks of the Linzizong Group. Highlights • We obtained the first zircon U-Pb ages from the Danshiting Formation volcanic rocks. • The Danshiting Formation was generated by northward subduction of the Neo-Tethys. • This paper divides the evolutionary history of the Neo-Tethys into four stages. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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31. Editorial Preface to Special Issue: Understanding dental proxies of ancient diets.
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Merceron, Gildas, Tütken, Thomas, and Scott, Robert
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GEOLOGICAL time scales , *FOSSIL teeth , *TOOTH abrasion , *DENTAL calculus , *COEXISTENCE of species , *DIET - Abstract
Vertebrate teeth are highly mineralized dermal tissues composed, principally, of bioapatite making them highly resistant to physical and chemical alteration over geologic time scales. This means that the morphology and microstructure of fossil teeth is often preserved, providing diagnostic features for taxonomic classification and enabling inferences about phylogenetic relationships. They also provide abundant information about the feeding ecology of fossil taxa, including diet, feeding behavior, local resource availability, habitat structure, and climate conditions. Tooth shape, tooth wear at different scales, dental chemistry and isotopic composition, as well as ingesta particles aggregated in dental calculus comprise important clues to reconstruct the feeding ecology of a fossil species. This special issue features 21 papers that address the use of dental proxies to infer diet and related ecological habits. Among them, a first paper compares post mortem damages on enamel surfaces with dietary-related tooth wear. Then, nine papers focus on in vivo or in vitro experimentation to test specific hypotheses. Authors address questions about taphonomic processes that may blur dietary or ecological signals, the biotic and abiotic sources of the dental wear, and the calibration of models linking diet composition to dental proxies. Eight papers explore links between dental proxies and ecology and behavior in real world contexts and focus on the study of living mammals in the wild at the individual and population scales. Among those latter studies, three integrate fossil case studies. The remaining papers address questions about niche partitioning, climate effects on local resources and their use, physiology, and the influence of diet on phenotypic selection in extinct species. As such, this special issue will stimulate further work on dental proxies and be of interest to a broad community of palaeoecologists. [ABSTRACT FROM AUTHOR]
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- 2023
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32. Modern vegetation-climate relationships for pollen assemblages across the mountainous regions of southwestern China: Implications for palaeoenvironmental reconstruction.
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Chi, Changting, Xiao, Xiayun, and Jia, Baoyan
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POLLEN , *TREE-rings , *FOSSIL pollen , *GROUND cover plants , *MOUNTAIN plants , *PALEOENVIRONMENTAL studies , *MOUNTAIN soils - Abstract
A comprehensive understanding of modern pollen transport processes is a prerequisite for utilizing fossil pollen to elucidate the evolution of palaeoclimates and palaeoenvironments, especially in areas such as southwestern China where complex mountainous topography results in vegetation heterogeneity. In this paper, we selected four vertical profiles in mountainous regions of southwestern China, each with distinct plant communities, to investigate the relationship between modern pollen rain, vegetation types and vegetation cover, and to quantify the influence of environmental factors. Results show that pollen assemblages are generally representative of regional plant communities, although long-distant transport of arboreal pollen by valley winds can introduce signals from a much wider area. The calibrated arboreal pollen percentage (AP) and ratio of arboreal pollen to non-arboreal pollen (AP/NAP) serves as reliable quantitative proxies for vegetation cover, highlighting the importance of appropriate calibration when interpreting fossil pollen assemblages. Climate is the primary determinant of pollen distribution across these mountains, with mean temperature of the coldest month (MTCM) playing the most prominent contribution. Additionally, the impact of vegetation cover and soil nutrients on pollen distribution are also significant. Our modern study improves the accuracy of pollen interpretation for palaeoenvironmental reconstruction in mountainous regions of southwestern China. • Pollen assemblages can effectively depict the characteristics of mountain vegetation communities. • The calibrated AP percentage and AP/NAP can quantitatively indicate arboreal cover. • MTCM controls pollen distribution in different mountains of southwestern China. • Climate dominates pollen distribution below treeline and vegetation cover controls above treeline. [ABSTRACT FROM AUTHOR]
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- 2024
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33. Human activities caused lake ecological transitions in the Chinese Loess Plateau over the past 1400 years.
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Zhang, Can, Zhou, Aifeng, Kong, Xiangzhen, Xue, Bin, and Zhao, Cheng
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LAKE ecology , *LAKE management , *LAKES , *ALGAL growth , *CLIMATE change - Abstract
The combined effects of climate change and human disturbance has degraded lake ecosystems worldwide in recent times, but there are few studies that explore the relative impact of these factors over long timescales. In this paper, we use sedimentary pigment data to reveal variations in algal abundance and the lake ecological environment of a typical subalpine lake (Beilianchi Lake) in the southwestern Chinese Loess Plateau, to distinguish the relative effects of natural climate change and human disturbance over the past 5000 years. Our data show that between 5000 and 1400 cal yr BP, algal abundance exhibited a slow decline without obvious fluctuations, mainly driven by a gradually drying and cooling climate. After 1400 cal yr BP, algal abundance showed large and rapid fluctuations characterized by a pattern of a decline, then increase, and then decline again. During this period, human activities began to affect lake ecology and gradually overshadowed the role of climatic changes as the main driving factor. Enhanced human disturbances caused a rapid and synchronous decline in algal abundance due to increases in soil erosion and reductions in water transparency. Algal biomass levels recovered when the soil erosion intensity decreased during 800–500 cal yr BP corresponding to the period from Southern Song to Yuan Dynasties. Thereafter (during the period of Ming and Qing Dynasties), as human activities became further enhanced and the soil erosion intensity became very high, the lake ecosystem rapidly transitioned to a stable state of low algal growth. This indicates that the lake ecosystem may have had the capacity to recover from moderate external disturbances in the early stages of human activity, but the resilience of the lake ecosystem began to decrease under stronger human disturbances. Our findings provide important empirical evidence for evaluating the current state of lakes and for sound lake management in the future. • High-resolution sedimentary pigment data reveal the lake ecological evolution of an alpine lake since 5000 yr BP. • Human activities began to exceed climate in driving lake ecological changes since 1400 yr BP. • The effect of human activities on lake ecological changes is more dramatic. • Lake ecosystem may have the capacity to recover from moderate human disturbances. [ABSTRACT FROM AUTHOR]
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- 2024
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34. Fuel-use strategies at ultrahigh elevations on the Tibetan Plateau since the last deglaciation.
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Sun, Qingli, Gao, Yu, Yang, Qi, Yang, Jishuai, Huang, Yunzhe, Wang, Yanren, Tong, Yan, Shen, Xuke, Ma, Zhikun, and Yang, Xiaoyan
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GLACIAL melting , *ALTITUDES , *ANIMAL droppings , *FUELWOOD , *BURNUP (Nuclear chemistry) , *PLATEAUS , *TUNDRAS , *SEA buckthorn - Abstract
Often referred to as the "Third Pole", the Tibetan Plateau combines high elevation, extreme cold temperatures, hyper-aridity, and low oxygen levels. The strategy that early populations adopted to adapt to the harsh environment of the Tibetan Plateau has always attracted much attention. However, relevant studies have predominantly focused on the relatively lower elevation northeastern part of the Tibetan Plateau (<3000 m a.s.l.), with limited study in areas of ultrahigh elevation (>3500 m a.s.l.). This paper employed the flotation method and charcoal analysis of survey profiles from thirteen archaeological sites in the ultrahigh-elevation region of the middle Yarlung Zangbo River basin on the southern Tibetan Plateau, and finds that ancient people have been active in this region since the last deglaciation. The primary fuel sources used by ancient populations were small trees such as sea buckthorn (Hippophae gyantsensis) and shrubs such as juniper (Juniperus). The widespread use of undesirable wood (dwarf thorny shrub) like Sophora moorcroftiana and Caragana , along with the phenomenon of many sites relying on a single taxon, reflects the prevalent issue of fuel scarcity in this ultrahigh-elevation region. This might have been a driving factor for the early adoption of animal dung as a primary fuel source by ancient populations on the southern Tibetan Plateau. • Thirteen new dating data greatly fill the gap in the history of human activities in the ultrahigh elevations. • First study of wood-fuel strategies of ancient populations at ultrahigh elevations. • Interpreting the livelihoods of ancient populations at ultrahigh elevations from the perspective of fuel utilization. • Proposing that the use of animal dung as fuel by populations was earlier due to the wood fuel scarcity at ultrahigh elevations on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]
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- 2024
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35. Vegetation changes through stadial and interstadial stages of MIS 4 and MIS 3 based on a palynological analysis of the Girraween Lagoon sediments of Darwin, Australia.
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Rowe, Cassandra, Brand, Michael, Wurster, Christopher M., and Bird, Michael I.
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VEGETATION dynamics , *LAGOONS , *SAVANNAS , *PALEOECOLOGY , *VEGETATION patterns - Abstract
A palynological record from Girraween Lagoon sediments (Darwin region of the Northern Territory, Australia) provides detailed long-term insight into tropical savanna vegetation community patterns, climatic and fire relationships, through Marine Isotope Stage 4 (MIS 4: 71–57 thousand years ago, ka) and Marine Isotope Stage 3 (MIS 3: 57–29 ka). Owing to a lack of data in reconstructing northern Australian environments, this paper looks to define and describe to a greater degree the nature and scope of these stadial and interstadial stages for the region. Girraween Lagoon simultaneously provides proximal palaeoecological data for the time and region of Aboriginal people's first arrival into Australia, also encompassing the late Pleistocene continental decline of megafauna. This study provides a dataset enabling full exploration of long-term people-landscape and faunal-floral interactions. Sea levels and associated variations imposed on the transportation of moisture and heat, held implications for MIS 4 and MIS 3 monsoon strength, which was particularly consequential for Girraween regional ecology. Results reveal a prolonged transition from wooded- to grassy-savanna, into a cool drier semi-arid savanna. Increasingly episodic delivery of moisture influenced the permanency of freshwater in the landscape. • A detailed picture of vegetation in monsoonal north Australia during MIS 4 and MIS 3. • An ultimate transition from grassy eucalypt savanna into semi-arid savanna revealed. • Changed monsoonal delivery particularly consequential for regional ecology. • An indication of baseline landscapes during people's first arrival into Australia. • Assisting to place megafaunal decline within an ecological landscape. [ABSTRACT FROM AUTHOR]
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- 2024
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36. A palaeoecological analysis of the Cretaceous (Aptian) insect fauna of the Crato Formation, Brazil.
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Bezerra, Francisco Irineudo and Mendes, Márcio
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FOSSIL insects , *PALEOECOLOGY , *AQUATIC insects , *INSECTS , *ARID regions , *SEDIMENTARY facies (Geology) ,GONDWANA (Continent) - Abstract
A rich insect fauna is found in the Cretaceous (Aptian) Nova Olinda Member of the Crato Formation in the Araripe Basin, northeastern Brazil. The Crato Formation was deposited close to the centre of the supercontinent Gondwana, prior to significant rifting. In this paper, we analyzed remains of 1135 insect specimens, representing 55 families, within two limestone facies of the Nova Olinda Member: pale yellow and dark gray limestones. We collected taphonomical data and assessed the paleoecological significance of insect faunas in terms of their distribution and interaction with the paleoenvironment. The insect fauna is dominanted by fully terrestrial taxa despite preservation in an aquatic paleoenvironment. Considering both facies, the distribution of insect families is similar throughout the Nova Olinda Member, which excludes possible overlapping of one entomofauna over another. The pale yellow limestones near the top of the section are richer in fossil insect content and show a higher incidence of aquatic and semiaquatic insects preserved in dorsoventral view compared to the dark gray limestones. This suggests that the Crato insects preserved in the pale yellow limestones experienced short transport distances or prolonged decay or both. In contrast, insects preserved in the dark gray limestones appear proportionally with higher degrees of disarticulation than those preserved in the pale yellow limestones, indicating that these insects underwent a higher degree of postmortem transport in the biostratinomic stage. Compared to descriptions of other Early Cretaceous assemblages, the taxonomic literature of Crato Paleoentomofauna shows distinct differences. The Yixian and Zaza formations are described as being dominated by beetles and wasps. The Crato Formation, however, is relatively richer in Paleoptera species. Both the sedimentary facies studied and the paleoentomological content reveal a complex ecosystem inserted in a depositional setting, similar to modern long-standing wetlands, and where periodically flooded zones were surrounded by dry lands with xeromorphic vegetation. • Crato insects preserved in the dark gray limestones appear proportionally with higher degrees of disarticulation. • The paleoentomological content reveals an ecosystem inserted in a setting similar to modern long-standing wetlands. • Compared to other Early Cretaceous assemblages, the Crato Paleoentomofauna is relatively richer in Paleoptera species. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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37. A late Quaternary palynological record from the southeastern margin of Brazil: Implications for the evolution of palaeoceanography, palaeoclimates and vegetation over the last 109 kyr.
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Barreto, Cintia Ferreira, da Silva de Freitas, Alex, de Souza, Taísa Camila Silveira, de Toledo, Mauro Bevilacqua, da Costa Portilho-Ramos, Rodrigo, dos Reis, Antonio Tadeu, and da Silva, Cleverson Guizan
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DINOFLAGELLATE cysts , *HOLOCENE Epoch , *POLLEN , *FERNS , *GLACIATION , *MARINE sediments , *TREE-rings - Abstract
Integration of late Quaternary continental and marine proxies allows improved reconstruction of palaeoenvironment and palaeoclimates models for the south-eastern coast of Brazil. In this paper, we analyse pollen, fern spores, and dinoflagellate cysts in a marine sediment core (GL74) over the last ∼109 kyr. Results showed that, between 109 and 89.5 kyr, low sea levels promoted the expansion of herbaceous taxa across open areas while climatic conditions were relatively warm and humid, as indicated by the high frequency of Atlantic rainforest Ombrophilous forest pollen types and abundant of fern spores. Between ∼79–49 kyr, higher concentrations of palynomorphs were recorded, which were likely related to the low relative sea level during the last glacial period. During this interval, there was a decrease in tree pollen grains and an increase in shrub and herbaceous pollen grains, indicating cold and relatively dry weather conditions. In the Holocene period, the low deposition of palynomorphs may have been influenced by the gradual submergence of the central part of the Brazilian coast. This process was associated with warm and humid climatic conditions, as suggested by the expansion of rainforests and the presence of hygrophyte/aquatic taxa and fern spores, as well as the retraction of grassland pollen types. Dinocyst assemblages suggest that nutrient-rich waters and/or the presence of upwelling cells were dominant between ∼109–88 kyr, but gradually reduced between 88 and 65 kyr (and/or ∼ 88–20 kyr) under the influence of subtropical fronts. The study culminated in the dominance of unproductive warm water in the upper column between 65 and 0.5 kyr. • Correlation of continental and marine proxies in south-eastern Brazil during the late Quaternary Late • Quaternary dynamics of the South Atlantic Ocean based on dinocysts • Reconstruction of palaeovegetation and palaeoclimate for the last ∼109 kyr along the southeast coast of Brazil [ABSTRACT FROM AUTHOR]
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- 2024
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38. Records of deep-sea turbidity current activity in the Bengal Fan since the Last Glacial Maximum.
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Li, Jingrui, Shan, Xin, Shi, Xuefa, Liu, Shengfa, Qiao, Shuqing, Zhang, Hui, Wu, Kaikai, Miao, Xiaoming, Jiang, Rui, Khokiattiwong, Somkiat, and Kornkanitnan, Narumol
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LAST Glacial Maximum , *TURBIDITY currents , *SUBMARINE fans , *SEA level , *LONG-Term Evolution (Telecommunications) , *TURBIDITES - Abstract
The long-term evolution of deep-sea turbidity current activity is closely related to climate and sea level changes; however, the impact of abrupt climate change (e.g. millennial-scale events in high northern latitudes) is poorly known. In this paper, deep-sea turbidite records in the western part of the lower Bengal Fan were identified since the Last Glacial Maximum (LGM) to investigate the effects of abrupt climate change on the development of the Earth's largest deep-sea fan. Our records show a termination of turbidite activity in the western lower fan at 16.6 ka–15.4 ka almost contemporaneous with Heinrich 1 event (a cooling stadial in high northern latitudes). The trigger of this termination in turbidite activity may have been a sharp decrease in erosion rates during a time of relatively stable sea level and rapid source-sink processes. The subsequent episodes of the Bolling/Allerod warm interstadial and Younger Dryas cold stadial and the rapid sea level rise event that followed possibly induced adjustment of turbidity current activities in the Bengal Fan, as indicated by other published records. In summary, we show that close links exist between abrupt climate changes in the high-latitude Northern Hemisphere and deep-sea turbidity current activity in the low-latitude South Asia. • Deep-sea turbidite records in the Bengal Fan since LGM were recovered. • Termination of turbidite in the western lower fan was triggered by HS1 event. • Links between high latitudes climate and low latitudes sedimentation were revealed. [ABSTRACT FROM AUTHOR]
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- 2024
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39. Modern pollen-plant diversity relationship in open landscapes of Tibetan Plateau.
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Liao, Mengna, Jin, Yili, Li, Kai, Liu, Lina, Wang, Nannan, Ni, Jian, and Cao, Xianyong
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NON-monogamous relationships , *PALYNOLOGY , *POLLEN , *HUMAN settlements , *ECOLOGICAL disturbances - Abstract
Past plant diversity dynamics can provide a historical perspective on biodiversity change and ecosystem dynamics as a guide to conservation management in the future. Pollen analysis is one of the most widely used approaches to reconstruct plant diversity change through time, but the representativeness of pollen diversity to plant diversity is not yet fully understood and especially in open landscapes. In this paper, we compare pollen assemblages from topsoil in the open landscapes of the Tibetan Plateau with the surrounding vegetation to investigate their compositional similarity and the correlations between their diversity (richness and evenness), and to evaluate the influence of climate variables, landscape characteristics, and human disturbance on the pollen diversity. The results show that pollen assemblages vary obviously in different vegetation types and they can represent their surrounding plant communities at low taxonomic levels. Pollen richness boarders a better match with plant richness than pollen evenness with plant evenness across the whole study area, but the correlation is weak (r adj 2 < 0.2, p < 0.001). Transforming plants into their pollen equivalents has little improvement for the correlations between pollen and plant richness/evenness. Pollen richness and evenness can capture well the trend in plant richness and evenness along the vegetation gradient, suggesting that they can be used as gamma (landscape scale) rather than alpha (local scale) diversity metrics in the study area. Mean annual precipitation (MAP), mean annual temperature (MAT), and patch richness (PatchS) are positively associated with pollen richness. MAP, PatchS, and human disturbance (HD) are significantly predictors for pollen evenness. These confirm that pollen richness and evenness can provide insights into past plant diversity dynamics and help evaluating the effects of climate and habitat changes and human disturbance on long timescales. • Pollen assemblages represent surrounding plant communities at low taxonomic levels. • Pollen diversity is reliable proxy for plant diversity at the landscape scale. • Vegetation shift is an important prerequisite in studying past plant diversity. • Pollen-equivalent transformation cannot improve pollen-plant diversity correlations. • Pollen diversity can indicate changes in past climate and habitat conditions. [ABSTRACT FROM AUTHOR]
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- 2024
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40. An integrated chronological study on the Quaternary sedimentary sequences of the Yangtze River delta, China.
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Li, Guomin, Ji, Wenting, Xiao, Guoqiao, Xu, Huiru, Liang, Yuan, Lai, Yiming, Du, Jianguo, Li, Xiangqian, and Wu, Jianqiang
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INTERGLACIALS , *CLIMATE change , *ELECTRON spin resonance dating , *PALEOMAGNETISM , *LAND subsidence - Abstract
The sedimentary sequences of the Yangtze River delta comprise important Quaternary records of tectonics, sea-level oscillation, and climatic change; however, analysis is hampered by a lack of a reliable chronological framework. In this paper, we present an integrated chronology for two sedimentary sequences (core ZKW2 and ZKW4) on the southern side of the Yangtze River delta, based on magnetostratigraphy and absolute methods (OSL, 14C, and ESR dating). The basal ages of the core ZKW2 and ZKW4 are ca. 2.25 Ma and 2.96 Ma, respectively. The integrated chronology indicates significant increases in the sedimentary accumulation rate at ∼0.15 Ma, rather than the Matuyama-Brunhes boundary as indicated by magnetostratigraphy alone. The observed sedimentary transition is possibly controlled by regional subsidence of the Zhe-Min Uplift, and climate evolution during the last interglacial period. • High-quality magnetostratigraphy is obtained for the Quaternary sediments in the YRD. • The SARs of the YRD sediments significantly enhanced since ∼0.15 Ma. • Tectonics and climate factors jointly control the sedimentary evolution in the YRD. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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41. Early Holocene vegetation development at Mesolithic fen dwelling sites in Dagsmosse, south-central Sweden, and its implications for understanding environment–human dynamics at various scales.
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Blaesild, Paulina, Hallgren, Fredrik, and Nielsen, Anne Birgitte
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MESOLITHIC Period , *PALYNOLOGY , *ANTHROPOGENIC effects on nature , *HOLOCENE Epoch , *VEGETATION management , *CYPERUS , *PHRAGMITES - Abstract
Recent discoveries of several Mesolithic sites within the Dagsmosse Basin, south-central Sweden, offer an opportunity to study the lifestyle and skillsets of Mesolithic hunter-gatherer-fishers operating in wetland environments. In this paper, we present a combined archaeological and palaeoecological analysis of a Mesolithic fenland environment using Repetitive-Proxy Pollen Analysis (RPPA) of early Holocene sequences. Based on comparison of stratigraphic profiles from two cores within the basin, we infer that the variance in pollen composition and anthropogenic signals reflect variability in human/vegetation interactions in the fenland, at different distances to the main human dwelling at Jussberg (9.0–8.2 ka cal BP). Our study describes the socio-environmental relations within the wetland and adjacent terrestrial areas, providing a basis for tracking changes in forager interactions with their surroundings during the Mesolithic. Pollen analysis is consistent with the previously established sequence of settlement phases and extent as well as providing new data concerning the anthropogenic impacts on plant communities within the wetland including the use, reuse, and management of vegetation taxa. Correlations between palaeoecological and archaeological data demonstrate that forager communities (i) prevailed in the open fenland landscape between 9.3 and 8.2 ka cal BP, (ii) actively altered taxa composition through small-scale clearings of pine (Pinus), birch (Betula) and sedges (Cyperaceae) and (iii) reduced canopy cover, possibly to intentionally encourage the growth of taxa such as hazel (Corylus), but that also promoted the establishment of pioneer plants such as mugwort (Artemisia) and bracken (Pteridium). • Mesolithic foragers impacted forest and grassland vegetation around the Dagsmosse basin as well as the wetland formation. • HGF clearance and plant-use was perceivable at multiple spatial scales through comparative pollen analysis. • Human activity and movement within the middle Scandinavian inland changed throughout the Mesolithic and the 8.2 ka stadial. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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42. Reply to the comment on Sanz-Pérez et al., "Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U[sbnd]Pb ages from the Pampas of Argentina" [Palaeogeography, Palaeoclimatology, Palaeoecology 634 (2024), 111917]
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Sanz-Pérez, Dánae, Montalvo, Claudia I., Mehl, Adriana E., Tomassini, Rodrigo L., Hernández Fernández, Manuel, and Domingo, Laura
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FOSSIL mammals , *STABLE isotope analysis , *PALEOECOLOGY , *LASER ablation inductively coupled plasma mass spectrometry , *NEOGENE Period , *ZIRCON , *RADIOACTIVE dating - Abstract
In the comment on our paper, Prevosti et al. (2024) make a series of criticisms regarding the alleged lack of information provided on the dated samples and their geographic and stratigraphic provenance. In this contribution, we will give a reply to their comments. Our new zircon dating achieves the objective of the original study and provides valuable insights into the paleoecological dynamics of the period. It was out of the scope for our work to undertake a high resolution stratigraphical/sedimentological and dating analysis of each of the selected outcrops/sites. • First zircon dates from Neogene classic sites in central Argentina are provided. • The new dating achieves the objective of the original study. • Dating sets a solid time frame for paleoecological interpretations. [ABSTRACT FROM AUTHOR]
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- 2024
- Full Text
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43. A quantitative method to infer lake area changes based on an extensive survey of lake surface sediment grain size across the Inner Mongolia Plateau, and its application to understanding the evolution of Lake Wulanhushao in northern China since 18.59 cal. kyr BP
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Liu, Zhennan, Wang, Wei, Niu, Zhimei, Jiang, Yajuan, Wen, Xue, Lv, Zhuoran, Wang, Hanyang, He, Jiang, Lv, Changwei, and Ma, Yuzhen
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LAKE sediments , *GRAIN size , *PARTICLE size distribution , *LAKE hydrology , *LAKES - Abstract
Grain size is commonly used as a proxy to reconstruct past lake hydrology; however, published research rarely links grain size with modern processes, and uncertainties exist for interpretation. In this paper, we decompose the grain size frequency distributions (GSFD) for 196 lake surface sediments from 61 lakes and 9 reservoirs across the Inner Mongolia Plateau and adjacent areas and divide them into five GSFD components. We statistically analyze the relationship between the GSFD components and influencing variables to determine the taphonomic dynamics and their environmental implications. Within individual lakes, we found that GSFD component 4 (74.00–209.30 μm) and GSFD component 5 (209.30–592.00 μm) dominate near the lake margin and reduce toward the lake center in proportions. By contrast, GSFD component 2 (2.75–15.56 μm) increases toward the lake center. Therefore, the proportions of GSFD component 2, 4, and 5 reflect the relative distance to the lakeshore and allow inferences about lake area changes. We apply this large modern dataset to a sediment core obtained from Lake Wulanhushao (WLHS) on the Inner Mongolia Plateau and link the lake surface sediment-based GSFD components to BEMMA end-members of grain size records to define their environmental implications over the last 18.59 cal. kyrs BP. We found that the Lake WLHS has responded to the orbital and suborbital climate changes since the last deglaciation. Specifically, maximum lake transgression prevailed during the early to middle Holocene (11.70–7.10 cal. kyr BP), medium lake transgression dominated during 17.05–15.80 cal. kyr BP, and weak transgression developed during 14.60–12.90 cal. kyr BP. Maximum lake regressions prevailed before 17.05 cal. kyr BP, during 15.80–14.60 cal. kyr BP and 12.90–11.70 cal. kyr BP. Our reconstructed early Holocene maximum lake area is consistent with regional abiotic proxy-based moisture records, but contrasts with the regional biotic proxy-based moisture records, which reconstruct increasing moisture conditions. Our new method to determine lake area changes will provide valuable data to understand the climate dynamics of northern China. • We numerically revealed the environmental implications of grain size components of lake surface sediment. • Linking lake surface sediment grain size component to core end members provide basis for interpretations. • Maximum lake transgression prevailed during the early Holocene in northern China. • Abiotic proxies-based early Holocene lake transgression is distinct with biotic proxies' reconstructions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
44. Comment on "Paleoenvironment and paleoecology associated with the early phases of the Great American Biotic Interchange based on stable isotope analysis of fossil mammals and new U[sbnd]Pb ages from the Pampas of Argentina" by Sanz-Pérez et al. [Palaeogeography, Palaeoclimatology, Palaeoecology, 634 (2024), 111917]
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Prevosti, Francisco J., Romano, Cristo O., and Pardiñas, Ulyses F.J.
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FOSSIL mammals , *STABLE isotope analysis , *PALEOECOLOGY , *STABLE isotopes , *ZIRCON - Abstract
Sanz-Pérez et al. (2024) recently, based on detrital zircon, presented new maximum depositional ages for several sites of the Neogene of central Argentina to constraint the age of the faunas studied with stable isotopes. Unfortunately, the precise provenance of the dated samples is not clear. In this comment, we discuss the absence of key basic information to replicate their (geochronological) study, or even to evaluate their inferences and conclusions. Without more information about the precise geographic provenance of the dated detrital zircons, and their stratigraphic position in the geological profile/schema of each locality the interpretation of the authors is not supported by the presented information. • Detrital Zircon Dates presented by Sanz-Pérez et al. (2024) lack of precise geographic location information. • These samples lack of any stratigraphic position in the profile of each location. • Based on a new work, the date of Salinas Grandes is from the top of the profile, and irrelevant for age constraint. • Geochronological inferences of Sanz-Pérez et al. (2024) are unsupported by the data presented in the paper. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
45. Marine sedimentary ancient DNA from Antarctic diatoms.
- Author
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Singh, Prashasti, Teixeira, João C., Bolch, Christopher, and Armbrecht, Linda
- Subjects
- *
FOSSIL DNA , *GEOLOGICAL time scales , *DIATOMS , *FOSSIL diatoms , *BIOLOGICAL fitness - Abstract
Antarctica is one of the most susceptible regions to climate change on Earth. Rising ocean temperatures, glacier melting, and disruptions of marine ecosystems make this polar region a focus of research on ecosystem transformation associated with ongoing climate change. Within the Antarctic ecosystem, diatoms, a key group of phytoplankton at the base of the marine food web, play a crucial role in maintaining marine ecosystem balance and functioning. Conventionally, fossil diatom assemblages have been investigated in marine sediment records to reconstruct paleoenvironmental conditions and understand climate change patterns of Antarctica. Recently, the application of ancient DNA techniques to ocean sediments (sedimentary ancient DNA, sed aDNA) has provided new insights into diatom community responses to environmental change over geological time scales. One benefit of sed aDNA analysis is that this technique can detect fragile diatom species that do not preserve well and are thus difficult to study via traditional microscopy techniques. In this paper, we review the importance of diatoms as indicators of Antarctic paleoenvironmental change, the novel use of diatom sed aDNA to assist Antarctic paleoenvironmental reconstruction, and the challenges and promises of using the sed aDNA approach. We propose that Fragilariopsis cylindrus , an extant polar diatom species, is an ideal model organism to study adaptation patterns of diatoms to changing climate due to its ecological success through time and the availability of whole-genome information for this species. Novel genetic information obtainable from ancient F. cylindrus, as well as other diatoms, will help us to better predict the evolutionary and adaptive dynamics of this important group of primary producers in the climatically vulnerable Antarctic region. • Climate change in Antarctica and the need to study this polar region. • Diatoms in Antarctic ecosystem and their role as paleoenvironmental indicators. • Using the novel technique of sedimentary ancient DNA (sed aDNA) in Antarctica. • Fragilariopsis cylindrus to study adaptation and evolution of diatoms in Antarctica. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
46. Significant anthropogenic impact on the mountain vegetation of Southeast China commenced ∼1 kyr BP, lagged behind similar changes in the lower Yangtze River basin and coastal plains by 2000–4000 years.
- Author
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Feng, Shi, Huang, Zhenhui, Ma, Chunmei, Zhu, Cheng, Meadows, Michael, and Lu, Huayu
- Subjects
- *
ANTHROPOGENIC effects on nature , *COASTAL plains , *MOUNTAIN plants , *WATERSHEDS , *PALYNOLOGY , *FIRE management - Abstract
Human impact on the coastal plain of Southeast China has been well studied over late Holocene timescales; however, an understanding of anthropogenic impact in mountainous regions is still lacking. In this paper, we present records of vegetation, fire, and human impact, spanning the past 4000 years, with a resolution of ∼40 years, obtained from an upland peatland in Southeast China. The results reveal that climate change (dominated by the evolution of the East Asia Monsoon) was the most critical factor controlling vegetation before 1.0 cal kyr BP, while human impact gradually emerged as the primary driver after 1.0 cal kyr BP in the mountains of Southeast China. As such, the record of anthropic impact in mountainous regions lagged behind the signal from the coastal plains by some 2000–4000 years. As the population migrating from northern China dispersed into the mountainous regions of Southeast China, demand for agricultural land promoted slash-and-burn cultivation and the destruction of broad-leaf forest. • Three climatic stages identified spanning 4.0 cal kyr BP based on pollen and charcoal analysis. • Significant anthropogenic impact on mountain vegetation of Southeast China occurred in 1.0 kyr BP, lagged coastal plains by 2000–4000 years. • The population migrating from northern China dispersed into the mountainous regions of southeastern China in 1.0 kyr BP, urgent demand for cultivated land. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
47. Middle to late Holocene hydroclimate instability in the Yangtze River Delta region of China inferred from phytolith records, and its implications for societal disruption.
- Author
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Xueming, Li, Yan, Liu, Jun, Jiang, Jinqi, Dai, Li, Xiao, Xiaoyu, Zhang, Xiaoshuang, Zhao, Jing, Chen, Shihao, Liu, Ning, Zhao, and Qianli, Sun
- Subjects
- *
ATLANTIC meridional overturning circulation , *INTERTROPICAL convergence zone , *HOLOCENE Epoch - Abstract
The decline of ancient societies has been often associated with hydroclimate instabilities. In this paper, we report phytolith records from the Yangtze River Delta of China, to reconstruct middle and late Holocene climate dynamics, and understand societal impacts. Our findings reveal that the area experienced a consistent decline in temperature and humidity punctuated by several rapid climate shifts. A distinct dry episode from 7000 to 6000 cal yr BP likely developed in response to weakened Atlantic Meridional Overturning Circulation (AMOC) and a southward shift of the intertropical convergence zone (ITCZ), resulting in a weakened East Asian summer monsoon (EASM) and a strengthened East Asian winter monsoon (EAWM). This dry condition would have favoured the emergence of dryland and facilitated rice cultivation in the lower Yangtze region. Another dry episode at 4500–4000 cal yr BP, which was probably associated with the widespread 4.2 ka climate event, and linked to a further retreat of the ITCZ and highly variable ENSO intensity, led to highly unstable hydroclimate conditions in the region. We argue that this event disrupted social resilience and culminated in the cultural collapse at the end of Liangzhu Culture. • Cooling trend since 8000 cal yr BP in response to decline of summer insolation. • Dry episodes at 7000–6000 and 4500–4000 cal yr BP. • Strength of AMOC and position of ITCZ jointly modulates the EASM. • Neolithic societal resilience shows varied responses to each dry episode. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
48. Provenance of fine-grained sediments along the South Bohai Coast, China since the mid-Holocene, and its implications for understanding coastal evolution and anthropogenic influences.
- Author
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Sun, Xiao, Li, Yan, Yi, Liang, Zhang, Jingran, Bi, Jianhua, Chen, Guangquan, and Hu, Ke
- Subjects
- *
PALEOGEOGRAPHY , *OPTICALLY stimulated luminescence dating , *ACCELERATOR mass spectrometry , *SEDIMENTATION & deposition , *ANTHROPOGENIC effects on nature , *SEDIMENTS - Abstract
Discriminating the provenance of fine-grained sediments is crucial for reconstructing paleogeography, sedimentary processes, and paleoclimate. In this paper, we investigate the South Bohai Coast to better understand source-to-sink systems in East Asia. This region is influenced by both distant sources such as the large-scale Yellow River and small local river sources flowing from the Luzhong Mountain area. Two Holocene sedimentary cores, dated using optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C chronology, were used to investigate the provenance of the fine-grained sediments over the last 7 kyrs. Clay mineralogy and relevant non-linear modeling were employed for provenance discrimination. The results show that the fine-grained sediments along the South Bohai Coast were mainly derived from the Yellow River during the periods of 7.0–5.4 ka and 4.5–2.6 ka, respectively, while the input from the Luzhong Mountain-derived rivers was greater during 5.4–4.5 ka and 2.6–0.2 ka, respectively. Fluvial activities and marine-terrestrial interaction driven by climate factors such as East Asian winter monsoon, temperature, and precipitation in river basins, dominantly influenced the provenance of fine-grained sediments from 7.0 to 2.6 ka. Anthropogenic impact on provenance increased after 2.6 ka. The chronology of the two cores showed extremely rapid sedimentation rate transitions at 5.2 ka and 1.5 ka, respectively, very likely attributed to anthropogenic-induced rapid progradation. Our study provides a model for better understanding the paleoenvironmental and paleogeographic evolution of a coastal area where multiple sources exist. • Anthropogenically high sedimentation rate in the South Bohai Coast in late Holocene. • Provenance discrimination of the fine-grained sediments in the South Bohai Coast since the mid-Holocene. • The major source of the fine-grained sediments in the South Bohai Coast changed episodically. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
49. Response of late Holocene vegetation to abrupt climatic events on the northwestern coast of the Bay of Bohai, China.
- Author
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Wang, Rongrong, Li, Yuecong, Zhang, Shengrui, Xu, Qinghai, Ge, Yawen, Li, Bing, Fan, Baoshuo, Zhang, Zhen, Li, Cange, Wang, Ying, You, Hanfei, Cao, Yihang, and Li, Yue
- Subjects
- *
COASTAL wetlands , *ATLANTIC meridional overturning circulation , *HALOPHYTES , *HOLOCENE Epoch , *PHRAGMITES , *CLIMATE change , *FOREST microclimatology ,EL Nino - Abstract
Coastal wetlands provide valuable ecosystem services and understanding their response to past climatic changes may help predict their possible future responses. In this paper, we obtained records of pollen, algae, sediment grain-size, and other environmental proxies, from a late Holocene sediment core (CFD-E) from the Caofeidian area, on the northwest coast of the Bay of Bohai, China. Our results indicate three major stages of environmental change. During Stage I (3500–2800 cal yr BP), arboreal pollen content was high (mostly >60%), especially for Pinus and Quercus , and the PCA sample scores on Axis 1 were negative indicating that regional vegetation was temperate broadleaved forest and the climate was wet. During Stage II (2800–2350 cal yr BP), the arboreal pollen content decreased substantially (mostly <40%), and the PCA Axis 1 sample scores were positive indicating a decrease in forest vegetation, grassland expansion, and a drier climate. During Stage III (2350–1400 cal yr BP), the arboreal pollen content increased again (mostly >40%), although it remained lower than during Stage I, indicating that forests expanded under a relatively humid climate while the wetland area decreased slightly. Our results also record the 2.8 ka and 2.4 ka events of monsoon weakening, which were characterized by increases in herbaceous pollen (indicating grassland expansion) and the drying of the regional climate. There are several differences in the regional expression of these two climatic events. During the 2.4 ka event, Chenopodiaceae pollen increased substantially (average of 42.0%), indicating the expansion of halophytes; whereas during the 2.8 ka event, an increase in Artemisia indicates the occurrence of a dry climate throughout the region. We suggest that the aridity during the 2.8 ka event was triggered by decreased solar activity and the resulting changes in the El Niño-Southern Oscillation, which weakened the East Asian summer monsoon. However, we suggest that the 2.4 ka event was driven by the weakening of the Atlantic Meridional Overturning Circulation. • Significant increase in halophytic vegetation during 3500–1400 cal yr BP • The 2.8 ka and 2.4 ka events were characterized by climate drying lasting ∼150 years. • During these two events the area of forest decreased and grassland expanded. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
50. The role of vegetation cover and slope angle in tephra layer preservation and implications for Quaternary tephrostratigraphy
- Author
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Dugmore, Andrew, Streeter, Richard, and Cutler, Nick
- Published
- 2018
- Full Text
- View/download PDF
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