Pub Date : 2024-11-29DOI: 10.1016/j.palaeo.2024.112628
Jie Zhou , Guoping Zhu
The painted notie Nototheniops larseni is a link between the lower and upper levels of food web as one of the most abundant and widespread fish species in the Southern Ocean. Otolith chemistry is a well-established approach for studying fish life histories and differentiating stock structure, and chemical analysis of otolith core can be used to distinguish fish stocks. This study demonstrates that the N. larseni juvenile stocks in the southern Bransfield Strait are sourced from the same environment, but the stocks in the southern Bransfield Strait and at South Georgia shelf are separated geographically using chemical data from otolith core, hatching and feeding checks, and edge. The ratios of 7Li to 42Ca across otolith sections of N. larseni juveniles in the southern Bransfield Strait are lower significantly than those at the South Georgia shelf, indicating the Li in fish otolith may act as a chemical tag for reflecting sea ice dynamics in the Southern Ocean.
{"title":"Otolith chemistry reveals painted notie (Nototheniops larseni) juvenile stocks differed between southern Bransfield Strait and South Georgia shelf","authors":"Jie Zhou , Guoping Zhu","doi":"10.1016/j.palaeo.2024.112628","DOIUrl":"10.1016/j.palaeo.2024.112628","url":null,"abstract":"<div><div>The painted notie <em>Nototheniops larseni</em> is a link between the lower and upper levels of food web as one of the most abundant and widespread fish species in the Southern Ocean. Otolith chemistry is a well-established approach for studying fish life histories and differentiating stock structure, and chemical analysis of otolith core can be used to distinguish fish stocks. This study demonstrates that the <em>N. larseni</em> juvenile stocks in the southern Bransfield Strait are sourced from the same environment, but the stocks in the southern Bransfield Strait and at South Georgia shelf are separated geographically using chemical data from otolith core, hatching and feeding checks, and edge. The ratios of <sup>7</sup>Li to <sup>42</sup>Ca across otolith sections of <em>N. larseni</em> juveniles in the southern Bransfield Strait are lower significantly than those at the South Georgia shelf, indicating the Li in fish otolith may act as a chemical tag for reflecting sea ice dynamics in the Southern Ocean.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"658 ","pages":"Article 112628"},"PeriodicalIF":2.6,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142756749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-23DOI: 10.1016/j.palaeo.2024.112608
Bernardo Peixoto , Daniel Sedorko , Gabriel E.B. de Barros , Heitor Francischini , Renato P. Ghilardi , Marcelo A. Fernandes
The earliest Cretaceous Botucatu Formation (Paraná Basin, Brazil) comprises an erg deposit developed in the central part of Gondwana and is dominated by eolian dune facies. In this paper, we improve understanding of the ichnology of eolian deposits by describing trace fossil assemblages in São Bento Quarry in Araraquara County. The trace fossils occur on paleodune slipface surfaces, and include trackways (Paleohelcura tridactyla and P. araraquarensis) and burrows (Arenicolites isp., Skolithos isp., Taenidium serpentinum, Vagorichnus anyao, and Planolites beverleyensis). The Skolithos isp. and Vagorichnus anyao specimens also occur in clusters in more intensely bioturbated beds. We interpret these assemblages as evidence of episodic wet events, which were unable to generate subaqueous facies, but triggered plant growth and invertebrate proliferation. Based on studies of modern hot deserts, we infer that the overall longstanding water input promoted some primary productivity sustaining striving invertebrates, recorded as low bioturbation levels. Episodic wet events controlled the bioturbation bursts by increasing the primary productivity and inducing consequent invertebrate proliferation. We propose that these bursts of invertebrate bioturbation observed along the stratigraphic section of dry facies can be taken as the main ichnological characteristic of a dry eolian system. We also propose refinements to the Octopodichnus–Entradichnus ichnofacies model, addressing unsolved issues to enhance the interpretation of ancient eolian environments.
{"title":"Pulses of life: Wet events in Botucatu Paleodesert evidenced by trace fossils analysis (earliest Cretaceous, Paraná Basin, Brazil)","authors":"Bernardo Peixoto , Daniel Sedorko , Gabriel E.B. de Barros , Heitor Francischini , Renato P. Ghilardi , Marcelo A. Fernandes","doi":"10.1016/j.palaeo.2024.112608","DOIUrl":"10.1016/j.palaeo.2024.112608","url":null,"abstract":"<div><div>The earliest Cretaceous Botucatu Formation (Paraná Basin, Brazil) comprises an erg deposit developed in the central part of Gondwana and is dominated by eolian dune facies. In this paper, we improve understanding of the ichnology of eolian deposits by describing trace fossil assemblages in São Bento Quarry in Araraquara County. The trace fossils occur on paleodune slipface surfaces, and include trackways (<em>Paleohelcura tridactyla</em> and <em>P. araraquarensis</em>) and burrows (<em>Arenicolites</em> isp., <em>Skolithos</em> isp., <em>Taenidium serpentinum</em>, <em>Vagorichnus anyao</em>, and <em>Planolites beverleyensis</em>). The <em>Skolithos</em> isp. and <em>Vagorichnus anyao</em> specimens also occur in clusters in more intensely bioturbated beds. We interpret these assemblages as evidence of episodic wet events, which were unable to generate subaqueous facies, but triggered plant growth and invertebrate proliferation. Based on studies of modern hot deserts, we infer that the overall longstanding water input promoted some primary productivity sustaining striving invertebrates, recorded as low bioturbation levels. Episodic wet events controlled the bioturbation bursts by increasing the primary productivity and inducing consequent invertebrate proliferation. We propose that these bursts of invertebrate bioturbation observed along the stratigraphic section of dry facies can be taken as the main ichnological characteristic of a dry eolian system. We also propose refinements to the <em>Octopodichnus</em>–<em>Entradichnus</em> ichnofacies model, addressing unsolved issues to enhance the interpretation of ancient eolian environments.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"658 ","pages":"Article 112608"},"PeriodicalIF":2.6,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-23DOI: 10.1016/j.palaeo.2024.112623
Yong Zheng , Jiawei Pan , Haibing Li , Zuolin Tian , Dongliang Liu , Mingkun Bai , Shuai Han , Chenglong Ge , Haijian Lu , Ning Zhong
The Chem Co graben is located in the westernmost part of the Qiangtang block, central Tibet. It is adjacent to the Longmu Co Fault to the north and approximately 50 km away from the Karakoram Fault to the west. The formation of the graben resulted in the exposure of basement rocks in the footwalls of the graben bounding normal fault, which hold crucial information on the Mesozoic closure of the Meso-Tethys Ocean. Garnet-biotite schist crops out sporadically in the footwall of the graben-boundary normal fault, and is intruded by leucogranite dikes. Pseudosection modeling indicates peak metamorphic conditions for the schist of 590–670 °C and 4.5–7.5 kbar, similar to the conditions of mid-crustal rocks at the western end of the Qiangtang block. Field investigations and microstructural analysis suggest syn-kinematical left-lateral strike-slip in both the biotite schist and granitoid veins. Zircon U − Pb, monazite U − Th − Pb, and 40Ar/39Ar ages show that intense regional intensive tectonic deformation and contemporaneous magmatism began at ∼120.6 Ma and ended with the peak metamorphism conditions at 105.3 ± 6.0 Ma. These results indicate that the closure of the Meso-Tethys Ocean in the westernmost part of central Tibet occurred over this period (i.e., 121–105 Ma) with final closure during the late Early Cretaceous. The closure of the Meso-Tethys Ocean likely triggered widespread far-field responses, extending from the Altyn Tagh Fault to the Longmu Co Fault, and reaching the Pangong and Hunza regions around the Western Himalayan Syntaxes. Episodic crustal thickening and surface uplift since the closure of the Meso-Tethys Ocean caused the upper crust to be extruded along the westernmost part of central Tibet, leading to the formation of the Chem Co graben.
{"title":"Far-field response to the closure of the Meso-Tethys Ocean: New geochronological evidence from the Chem Co graben in the westernmost part of Central Tibet","authors":"Yong Zheng , Jiawei Pan , Haibing Li , Zuolin Tian , Dongliang Liu , Mingkun Bai , Shuai Han , Chenglong Ge , Haijian Lu , Ning Zhong","doi":"10.1016/j.palaeo.2024.112623","DOIUrl":"10.1016/j.palaeo.2024.112623","url":null,"abstract":"<div><div>The Chem Co graben is located in the westernmost part of the Qiangtang block, central Tibet. It is adjacent to the Longmu Co Fault to the north and approximately 50 km away from the Karakoram Fault to the west. The formation of the graben resulted in the exposure of basement rocks in the footwalls of the graben bounding normal fault, which hold crucial information on the Mesozoic closure of the Meso-Tethys Ocean. Garnet-biotite schist crops out sporadically in the footwall of the graben-boundary normal fault, and is intruded by leucogranite dikes. Pseudosection modeling indicates peak metamorphic conditions for the schist of 590–670 °C and 4.5–7.5 kbar, similar to the conditions of mid-crustal rocks at the western end of the Qiangtang block. Field investigations and microstructural analysis suggest <em>syn</em>-kinematical left-lateral strike-slip in both the biotite schist and granitoid veins. Zircon U − Pb, monazite U − Th − Pb, and <sup>40</sup>Ar/<sup>39</sup>Ar ages show that intense regional intensive tectonic deformation and contemporaneous magmatism began at ∼120.6 Ma and ended with the peak metamorphism conditions at 105.3 ± 6.0 Ma. These results indicate that the closure of the Meso-Tethys Ocean in the westernmost part of central Tibet occurred over this period (i.e., 121–105 Ma) with final closure during the late Early Cretaceous. The closure of the Meso-Tethys Ocean likely triggered widespread far-field responses, extending from the Altyn Tagh Fault to the Longmu Co Fault, and reaching the Pangong and Hunza regions around the Western Himalayan Syntaxes. Episodic crustal thickening and surface uplift since the closure of the Meso-Tethys Ocean caused the upper crust to be extruded along the westernmost part of central Tibet, leading to the formation of the Chem Co graben.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"658 ","pages":"Article 112623"},"PeriodicalIF":2.6,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-22DOI: 10.1016/j.palaeo.2024.112621
Fangjian Xu , Xilin Zhang , Jianwei Xu , Zhilei Sun , Shengqiang Yuan , Xiting Liu
This study utilizes AMS 14C dating, grain size analysis, and elemental composition to ascertain the provenance of sediments in core C01, thereby offering insights into the paleoenvironmental evolution of the Okinawa Trough since 19 cal. ka BP. Between 19.0 and 11.3 cal. ka BP, the sediments were predominantly derived from the Changjiang River, a phenomenon attributed to the river's seaward expansion during periods of low sea level. During this interval, the Kuroshio Current (KC) exhibited relative stability. However, the rise in sea level from 11.3 to 7.3 cal. ka BP resulted in a shift in sediment sources, incorporating contributions from the Changjiang River and/or the continental shelf post-deglaciation to Taiwan, alongside a significant intensification of the KC. This increase in KC intensity is likely correlated with heightened summer insolation in the low latitudes of the Northern Hemisphere and an enhanced East Asian summer monsoon. Additionally, volcanic activity occurring at 7.3 cal. ka BP played a critical role in modifying sediment composition. By 7.3 cal. ka BP, sea levels approximated contemporary conditions, with terrestrial sediments primarily sourced from Taiwan. Around 4.9 cal. ka BP, a marked decrease in KC intensity was observed, potentially influenced by the strengthening of the El Niño-Southern Oscillation, which disrupts subtropical circulation in the North Pacific. The sedimentary records from core C01 illustrate that low-latitude Pacific climate variability since the last deglaciation has significantly impacted changes in sedimentary provenance and environmental conditions in the Okinawa Trough.
本研究利用AMS 14C测年、粒度分析和元素组成来确定岩芯C01中沉积物的来源，从而了解自19 cal. ka BP以来冲绳海槽的古环境演变。在 19.0 至 11.3 cal. ka BP 期间，沉积物主要来自长江，这一现象归因于长江在低海平面时期的向海扩张。在这一时期，黑潮（KC）相对稳定。然而，公元前 11.3 至公元前 7.3 千年海平面的上升导致沉积物来源发生变化，将长江和/或脱冰期后大陆架的沉积物汇入台湾，同时 KC 也显著增强。KC 强度的增加可能与北半球低纬度地区夏季日照增强以及东亚夏季季风增强有关。此外，发生在 7.3 cal. ka BP 的火山活动在改变沉积物组成方面起到了关键作用。到 7.3 cal. ka BP 时，海平面与当代情况接近，陆地沉积物主要来自台湾。约公元前 4.9 千年，KC 强度明显下降，这可能是受厄尔尼诺-南方涛动加强的影响，厄尔尼诺-南方涛动扰乱了北太平洋的副热带环流。来自岩芯 C01 的沉积记录表明，自上一次褪冰以来的低纬度太平洋气候变异极大地影响了冲绳海槽沉积产地和环境条件的变化。
{"title":"Sea level and low-latitude climate control on sedimentary provenance and paleoenvironmental evolution in the central Okinawa Trough since 19 cal. ka BP","authors":"Fangjian Xu , Xilin Zhang , Jianwei Xu , Zhilei Sun , Shengqiang Yuan , Xiting Liu","doi":"10.1016/j.palaeo.2024.112621","DOIUrl":"10.1016/j.palaeo.2024.112621","url":null,"abstract":"<div><div>This study utilizes AMS <sup>14</sup>C dating, grain size analysis, and elemental composition to ascertain the provenance of sediments in core C01, thereby offering insights into the paleoenvironmental evolution of the Okinawa Trough since 19 cal. ka BP. Between 19.0 and 11.3 cal. ka BP, the sediments were predominantly derived from the Changjiang River, a phenomenon attributed to the river's seaward expansion during periods of low sea level. During this interval, the Kuroshio Current (KC) exhibited relative stability. However, the rise in sea level from 11.3 to 7.3 cal. ka BP resulted in a shift in sediment sources, incorporating contributions from the Changjiang River and/or the continental shelf post-deglaciation to Taiwan, alongside a significant intensification of the KC. This increase in KC intensity is likely correlated with heightened summer insolation in the low latitudes of the Northern Hemisphere and an enhanced East Asian summer monsoon. Additionally, volcanic activity occurring at 7.3 cal. ka BP played a critical role in modifying sediment composition. By 7.3 cal. ka BP, sea levels approximated contemporary conditions, with terrestrial sediments primarily sourced from Taiwan. Around 4.9 cal. ka BP, a marked decrease in KC intensity was observed, potentially influenced by the strengthening of the El Niño-Southern Oscillation, which disrupts subtropical circulation in the North Pacific. The sedimentary records from core C01 illustrate that low-latitude Pacific climate variability since the last deglaciation has significantly impacted changes in sedimentary provenance and environmental conditions in the Okinawa Trough.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"658 ","pages":"Article 112621"},"PeriodicalIF":2.6,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.palaeo.2024.112614
Zhongxuan Li , Haiping Huang , Simon C. George
Molecular compositions in sediments collected by Ocean Drilling Program Leg 189 at Site 1172 in the Tasmanian Gateway, Australia have been characterised by gas chromatography–mass spectrometry to assess the impact of the Paleocene–Eocene Thermal Maximum (PETM) on organic matter origins and evolution. Total organic carbon (TOC) and sulfur contents reach the lowest values immediately before the initiation of the negative carbon isotope excursion (CIE) in the shallow marine environment on the East Tasman Plateau. The TOC content increases slightly while the sulfur content increases more substantially during deposition of the CIE, suggesting the occurrence of low-oxygen environments during the PETM event. The studied section is thermally immature, as shown by the dominance of biological configuration biomarkers such as 17β(H),21β(H)-hopanes (ββ) and hopenes. Changes in relative abundance of compound classes and isomer ratios are largely caused by the variation of source inputs and depositional conditions. Very low abundance of marine steroids during the CIE, but very enriched hopanoids, indicate low marine productivity, in accord with substantial remineralisation of organic matter in the bottom waters. The ββ-hopanes are the most abundant hopanoid series, followed by the neohop-13(18)-ene and hop-17(21)-ene series, further verifying the immaturity of the organic constituents in the samples. Hopane ratios (ββ/(βα + αβ) and βα/(βα + αβ) with different carbon numbers are systematically higher in sediments deposited during the CIE than those formed pre- and post-CIE, suggest increased bacterial inputs. Higher C30/C29 and C30/C31 hopanoid ratios in the CIE sediments are consistent with a greater contribution from in situ bacterial organic matter, rather than continental soil erosion by flooding. This is supported by the higher C27–32 hopanoids/(C27 + C29 + C31n-alkanes) ratio and sulfur content during the CIE. A relatively lower TOC content in the sediments formed during the PETM is inferred to have been caused by dilution by both enhanced detrital input and intensified bacterial consumption. This study demonstrates that the biomarker approach can play an important role in the identification of organic matter origin and characterisation of depositional environment for PETM sequences.
{"title":"Molecular compositional variation of organic matter deposited on the East Tasman Plateau during the Paleocene–Eocene Thermal Maximum","authors":"Zhongxuan Li , Haiping Huang , Simon C. George","doi":"10.1016/j.palaeo.2024.112614","DOIUrl":"10.1016/j.palaeo.2024.112614","url":null,"abstract":"<div><div>Molecular compositions in sediments collected by Ocean Drilling Program Leg 189 at Site 1172 in the Tasmanian Gateway, Australia have been characterised by gas chromatography–mass spectrometry to assess the impact of the Paleocene–Eocene Thermal Maximum (PETM) on organic matter origins and evolution. Total organic carbon (TOC) and sulfur contents reach the lowest values immediately before the initiation of the negative carbon isotope excursion (CIE) in the shallow marine environment on the East Tasman Plateau. The TOC content increases slightly while the sulfur content increases more substantially during deposition of the CIE, suggesting the occurrence of low-oxygen environments during the PETM event. The studied section is thermally immature, as shown by the dominance of biological configuration biomarkers such as 17β(H),21β(H)-hopanes (ββ) and hopenes. Changes in relative abundance of compound classes and isomer ratios are largely caused by the variation of source inputs and depositional conditions. Very low abundance of marine steroids during the CIE, but very enriched hopanoids, indicate low marine productivity, in accord with substantial remineralisation of organic matter in the bottom waters. The ββ-hopanes are the most abundant hopanoid series, followed by the neohop-13(18)-ene and hop-17(21)-ene series, further verifying the immaturity of the organic constituents in the samples. Hopane ratios (ββ/(βα + αβ) and βα/(βα + αβ) with different carbon numbers are systematically higher in sediments deposited during the CIE than those formed pre- and post-CIE, suggest increased bacterial inputs. Higher C<sub>30</sub>/C<sub>29</sub> and C<sub>30</sub>/C<sub>31</sub> hopanoid ratios in the CIE sediments are consistent with a greater contribution from in situ bacterial organic matter, rather than continental soil erosion by flooding. This is supported by the higher C<sub>27</sub><sub>–</sub><sub>32</sub> hopanoids/(C<sub>27</sub> + C<sub>29</sub> + C<sub>31</sub> <em>n</em>-alkanes) ratio and sulfur content during the CIE. A relatively lower TOC content in the sediments formed during the PETM is inferred to have been caused by dilution by both enhanced detrital input and intensified bacterial consumption. This study demonstrates that the biomarker approach can play an important role in the identification of organic matter origin and characterisation of depositional environment for PETM sequences.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"658 ","pages":"Article 112614"},"PeriodicalIF":2.6,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142748671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.palaeo.2024.112613
Hanfei You , Shixiong Yang , Yuecong Li , Shengrui Zhang , Zhen Zhang , Linyuan Ma , Jiheng Shi , Ying Wang , Xiaotian Zhang , Yunfei Yang
The characteristics and driving mechanisms of early Holocene extreme climatic events can provide a basis for the prediction and assessment of such events under ongoing global warming. Coastal areas, with their unique geographical location and fragile ecological environment, are highly sensitive to climate change, making the study of extreme climatic events in these regions potentially providing a different understanding of the processes and mechanisms involved. We studied the Holocene sediments of core BXZK04 from northern Bohai Bay, China, combining 9 AMS 14C dates with high-resolution analyses of pollen, algal remains, and grain size, together with modern pollen databases, to quantitatively reconstruct mean annual precipitation. Our principal findings are: (1) The climate in northern Bohai Bay during 10,900–8600 cal yr BP showed a gradual trend towards increased humidity, with fluctuations. We propose that long-term climate change in the study area was dominated by Northern Hemisphere insolation and regional sea-level changes. (2) Two significant weak monsoon events occurred in the study area, during 9600–9300 cal yr BP and 9060–8950 cal yr BP, corresponding to the 9.4 ka and 8.9 ka climatic events, respectively. During these events, forest vegetation decreased, herbaceous vegetation expanded, and there was a significant reduction in monsoon precipitation (a decrease of ∼200 mm). These events may have been controlled by the weakening of solar activity and reduced Atlantic Meridional Overturning Circulation (AMOC) caused by freshwater influx to the North Atlantic, leading to the southward shift of the Intertropical Convergence Zone (ITCZ) and more frequent El Niño events.
{"title":"Characteristics and driving mechanisms of early Holocene weakened monsoon events: Evidence from northern Bohai Bay, China","authors":"Hanfei You , Shixiong Yang , Yuecong Li , Shengrui Zhang , Zhen Zhang , Linyuan Ma , Jiheng Shi , Ying Wang , Xiaotian Zhang , Yunfei Yang","doi":"10.1016/j.palaeo.2024.112613","DOIUrl":"10.1016/j.palaeo.2024.112613","url":null,"abstract":"<div><div>The characteristics and driving mechanisms of early Holocene extreme climatic events can provide a basis for the prediction and assessment of such events under ongoing global warming. Coastal areas, with their unique geographical location and fragile ecological environment, are highly sensitive to climate change, making the study of extreme climatic events in these regions potentially providing a different understanding of the processes and mechanisms involved. We studied the Holocene sediments of core BXZK04 from northern Bohai Bay, China, combining 9 AMS <sup>14</sup>C dates with high-resolution analyses of pollen, algal remains, and grain size, together with modern pollen databases, to quantitatively reconstruct mean annual precipitation. Our principal findings are: (1) The climate in northern Bohai Bay during 10,900–8600 cal yr BP showed a gradual trend towards increased humidity, with fluctuations. We propose that long-term climate change in the study area was dominated by Northern Hemisphere insolation and regional sea-level changes. (2) Two significant weak monsoon events occurred in the study area, during 9600–9300 cal yr BP and 9060–8950 cal yr BP, corresponding to the 9.4 ka and 8.9 ka climatic events, respectively. During these events, forest vegetation decreased, herbaceous vegetation expanded, and there was a significant reduction in monsoon precipitation (a decrease of ∼200 mm). These events may have been controlled by the weakening of solar activity and reduced Atlantic Meridional Overturning Circulation (AMOC) caused by freshwater influx to the North Atlantic, leading to the southward shift of the Intertropical Convergence Zone (ITCZ) and more frequent El Niño events.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"657 ","pages":"Article 112613"},"PeriodicalIF":2.6,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-19DOI: 10.1016/j.palaeo.2024.112606
Sharrah McKenzie , Ghislain Thiery , David M. Alba , Daniel DeMiguel
The earliest Vallesian (∼11.2 Ma) sites of Castell de Barberà (CB) and Creu de Conill 20 (CCN20), in the Vallès-Penedès Basin (NE Iberian Peninsula), are similarly well sampled but display differences in faunal composition that hint at paleoenvironmental differences. Most importantly, CB records one of the few co-occurrences of hominoids and pliopithecoids in the Miocene of Europe, while primates are seemingly absent from CCN20. Differences are also reflected in the more diverse suid assemblage from CB. To ascertain the paleoecological basis for such differences, here we investigate the diets of the suids from these sites—the suine Propotamochoerus palaeochoerus, the tetraconodontines Parachleustochoerus valentini and Versoporcus steinheimensis, and the listriodontine Listriodon splendens. We use 3D dental topography to infer paleodiet and provide further insight into the local paleoenvironmental differences between these sites. We measure four variables—orientation patch count, relief index, angularity, and mean surface slope—and distinguish herbivorous from omnivorous taxa, with the former categorized as browsers, mixed feeders, and grazers. The analyzed suids are similar in terms of angularity but differ in mean surface slope, orientation patch count and relief index. A canonical variate analysis classifies the CB and CCN20 suids as herbivorous (mixed feeders), except for P. palaeochoerus from CCN20, which displays greater similarities to omnivores (higher surface complexity), suggesting more varied diets in the latter locality. We conclude that, despite being roughly coeval and geographically close (∼10 km), these two sites record different local paleoenvironments—with CB representing a very humid and densely forested habitat, and CCN20 recording a more open, arid, and seasonal environment. This confirms previous inferences based on faunal composition and would explain the absense of primates from CCN20. Our study further highlights the relevance of local paleoenvironments for understanding differences in faunal composition among past communities from the same area.
伊比利亚半岛东北部瓦莱斯-佩内德斯盆地（Vallès-Penedès Basin）最早的瓦莱斯时期（11.2Ma∼）遗址 Castell de Barberà（CB）和 Creu de Conill 20（CCN20）的采样情况类似，但动物组成却有所不同，这暗示了古环境的差异。最重要的是，CB 记录了欧洲中新世为数不多的类人猿和猿人的共同出现，而 CCN20 似乎没有灵长类动物。这种差异也反映在中新世更多样化的麂类群中。为了确定造成这种差异的古生态学基础，我们在此研究了这些地点的麂类--麂Propotamochoerus palaeochoerus、四齿兽Parachleustochoerus valentini和Versoporcus steinheimensis，以及长齿兽Listriodon splendens的饮食。我们利用三维牙齿地形推断古饮食，并进一步了解这些地点之间的局部古环境差异。我们测量了四个变量--方位斑块数、地貌指数、角度和平均表面坡度，并区分了草食类群和杂食类群，前者被分为食草动物、混合食草动物和食草动物。所分析的麂类在角度方面相似，但在平均表面坡度、方位斑块数和浮雕指数方面有所不同。典型变异分析将 CB 和 CCN20 的麂子归类为草食性（混合取食者），只有 CCN20 的 P. palaeochoerus 与杂食者更为相似（表面复杂性更高），这表明后者的食性更为多样。我们的结论是，尽管这两个地点大致处于同一时期，地理位置也很接近（∼10 km），但它们记录了当地不同的古环境--CB代表了一个非常潮湿和森林茂密的栖息地，而CCN20则记录了一个更加开阔、干旱和季节性的环境。这证实了之前基于动物组成的推断，也解释了为什么CCN20没有发现灵长类动物。我们的研究进一步强调了当地古环境对于理解同一地区过去群落动物组成差异的意义。
{"title":"Three-dimensional dental topography of fossil suids and paleoenvironmental reconstruction of earliest Vallesian (Late Miocene) sites from the Vallès-Penedès Basin (NE Iberian Peninsula)","authors":"Sharrah McKenzie , Ghislain Thiery , David M. Alba , Daniel DeMiguel","doi":"10.1016/j.palaeo.2024.112606","DOIUrl":"10.1016/j.palaeo.2024.112606","url":null,"abstract":"<div><div>The earliest Vallesian (∼11.2 Ma) sites of Castell de Barberà (CB) and Creu de Conill 20 (CCN20), in the Vallès-Penedès Basin (NE Iberian Peninsula), are similarly well sampled but display differences in faunal composition that hint at paleoenvironmental differences. Most importantly, CB records one of the few co-occurrences of hominoids and pliopithecoids in the Miocene of Europe, while primates are seemingly absent from CCN20. Differences are also reflected in the more diverse suid assemblage from CB. To ascertain the paleoecological basis for such differences, here we investigate the diets of the suids from these sites—the suine <em>Propotamochoerus palaeochoerus</em>, the tetraconodontines <em>Parachleustochoerus valentini</em> and <em>Versoporcus steinheimensis</em>, and the listriodontine <em>Listriodon splendens</em>. We use 3D dental topography to infer paleodiet and provide further insight into the local paleoenvironmental differences between these sites. We measure four variables—orientation patch count, relief index, angularity, and mean surface slope—and distinguish herbivorous from omnivorous taxa, with the former categorized as browsers, mixed feeders, and grazers. The analyzed suids are similar in terms of angularity but differ in mean surface slope, orientation patch count and relief index. A canonical variate analysis classifies the CB and CCN20 suids as herbivorous (mixed feeders), except for <em>P. palaeochoerus</em> from CCN20, which displays greater similarities to omnivores (higher surface complexity), suggesting more varied diets in the latter locality. We conclude that, despite being roughly coeval and geographically close (∼10 km), these two sites record different local paleoenvironments—with CB representing a very humid and densely forested habitat, and CCN20 recording a more open, arid, and seasonal environment. This confirms previous inferences based on faunal composition and would explain the absense of primates from CCN20. Our study further highlights the relevance of local paleoenvironments for understanding differences in faunal composition among past communities from the same area.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"657 ","pages":"Article 112606"},"PeriodicalIF":2.6,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.palaeo.2024.112609
Yijia Ye, Xibin Tan
Following the India-Eurasian collision, widespread mountain building has occurred in and around the Tibetan Plateau, and further influenced the regional climate. The tectonic activity and climate changes significantly affect the evolution of drainage basins. The Yellow River originates from the central Tibetan Plateau and flows through the northeastern margin of the plateau. Although the tectonic and surface processes in the Yellow River headwater area have been extensively studied, the drainage evolution in this region and its controlling mechanisms remain controversial. Drainage divides, which serve as the boundaries of drainage basins, can migrate for tens of millions of years after a tectonic and/or climatic disturbance. Therefore, drainage-divide stability can provide new and independent constraints on drainage evolution. In this study, we assess the stability of the drainage divide surrounding the Yellow River headwater area using two methods, χ-plot and Gilbert metrics. The result shows that the Yellow River headwater is shrinking as surrounding rivers encroach upon it. Based on the drainage-divide stability analysis, numerical simulation, and previous research, we suggest that both tectonic activity and climate changes have profoundly influenced the drainage evolution in the Yellow River headwater area. The shrinkage of the Yellow River headwater is mainly driven by the northeastward expansion of the Tibetan Plateau in the Late Cenozoic. Meanwhile, the Yellow River headwater area has become increasingly flattening, which creates conditions for sedimentation and periodic disintegration and re-integration events driven by cyclical climate changes (e.g., glacial cycles).
{"title":"The Yellow River headwater is shrinking in response to the northeastward expansion of the Tibetan Plateau","authors":"Yijia Ye, Xibin Tan","doi":"10.1016/j.palaeo.2024.112609","DOIUrl":"10.1016/j.palaeo.2024.112609","url":null,"abstract":"<div><div>Following the India-Eurasian collision, widespread mountain building has occurred in and around the Tibetan Plateau, and further influenced the regional climate. The tectonic activity and climate changes significantly affect the evolution of drainage basins. The Yellow River originates from the central Tibetan Plateau and flows through the northeastern margin of the plateau. Although the tectonic and surface processes in the Yellow River headwater area have been extensively studied, the drainage evolution in this region and its controlling mechanisms remain controversial. Drainage divides, which serve as the boundaries of drainage basins, can migrate for tens of millions of years after a tectonic and/or climatic disturbance. Therefore, drainage-divide stability can provide new and independent constraints on drainage evolution. In this study, we assess the stability of the drainage divide surrounding the Yellow River headwater area using two methods, χ-plot and Gilbert metrics. The result shows that the Yellow River headwater is shrinking as surrounding rivers encroach upon it. Based on the drainage-divide stability analysis, numerical simulation, and previous research, we suggest that both tectonic activity and climate changes have profoundly influenced the drainage evolution in the Yellow River headwater area. The shrinkage of the Yellow River headwater is mainly driven by the northeastward expansion of the Tibetan Plateau in the Late Cenozoic. Meanwhile, the Yellow River headwater area has become increasingly flattening, which creates conditions for sedimentation and periodic disintegration and re-integration events driven by cyclical climate changes (e.g., glacial cycles).</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"657 ","pages":"Article 112609"},"PeriodicalIF":2.6,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-17DOI: 10.1016/j.palaeo.2024.112612
Pankaj Mahanta , Anil K. Gupta , Prasanta Sanyal
This study investigates changes in the bottom water circulation of the Indian Ocean since 6.5 Ma, based on benthic foraminiferal relative abundances and their stable isotope ratios from Ocean Drilling Program (ODP) Sites 709 and 758. A significant shift, from dominant North Indian Deep Water (NIDW) to Antarctic Bottom Water (AABW) circulation, is documented at ∼3.3 Ma. Principal Component Analysis (PCA) reveals two major benthic foraminiferal assemblages (PCA1 and PCA2). PCA2 is dominated by Nuttallides umbonifera, Globocassidulina subglobosa, and Epistominella exigua, representing cold and well‑oxygenated bottom water conditions between 3.3 and 2.3 Ma. The increased δ18O values of Cibicides wuellerstorfi and high relative abundance of N. umbonifera between ∼3.3 and 2.3 Ma at both sites, indicate an increased influence of AABW in the Indian Ocean due to a major increase in Antarctic ice volume. PCA1 is dominated by Uvigerina proboscidea, Fissurina spp., and miliolids, indicating oxygen-poor bottom waters and high surface productivity between 1.7 and 0.5 Ma associated with an influence of NIDW. The high relative abundance of U. proboscidea and low relative abundance of E. exigua signify low seasonality and sustained flux of organic matter with a signature of strong South Equatorial Counter Current formed by the seasonal reversal of winds during 1.7–0.5 Ma at Site 709.
本研究根据大洋钻探计划（ODP）第 709 和 758 号站点的底栖有孔虫相对丰度及其稳定同位素比值，研究了自 6.5 Ma 以来印度洋底层水环流的变化。北印度深水（NIDW）到南极底层水（AABW）环流在 3.3 Ma ∼发生了重大转变。主成分分析（PCA）显示了两种主要的底栖有孔虫组合（PCA1 和 PCA2）。PCA2 以 Nuttallides umbonifera、Globocassidulina subglobosa 和 Epistominella exigua 为主，代表了 3.3 至 2.3 Ma 期间低温和高氧的底层水条件。在两个地点，Cibicides wuellerstorfi 的 δ18O 值增加，N. umbonifera 的相对丰度较高，表明由于南极冰量的大幅增加，AABW 对印度洋的影响增大。PCA1 以 Uvigerina proboscidea、Fissurina spp.U. proboscidea 的相对丰度较高，而 E. exigua 的相对丰度较低，这表明在 709 地点 1.7-0.5 Ma 期间风向季节性逆转形成的南赤道逆流具有低季节性和有机物持续通量的特征。
{"title":"A pronounced deep water cooling in the Indian Ocean at ∼ 3.3–2.3 Ma linked to a major increase in the Antarctic ice volume","authors":"Pankaj Mahanta , Anil K. Gupta , Prasanta Sanyal","doi":"10.1016/j.palaeo.2024.112612","DOIUrl":"10.1016/j.palaeo.2024.112612","url":null,"abstract":"<div><div>This study investigates changes in the bottom water circulation of the Indian Ocean since 6.5 Ma, based on benthic foraminiferal relative abundances and their stable isotope ratios from Ocean Drilling Program (ODP) Sites 709 and 758. A significant shift, from dominant North Indian Deep Water (NIDW) to Antarctic Bottom Water (AABW) circulation, is documented at ∼3.3 Ma. Principal Component Analysis (PCA) reveals two major benthic foraminiferal assemblages (PCA1 and PCA2). PCA2 is dominated by <em>Nuttallides umbonifera</em>, <em>Globocassidulina subglobosa</em>, and <em>Epistominella exigua</em>, representing cold and well‑oxygenated bottom water conditions between 3.3 and 2.3 Ma. The increased δ<sup>18</sup>O values of <em>Cibicides wuellerstorfi</em> and high relative abundance of <em>N. umbonifera</em> between ∼3.3 and 2.3 Ma at both sites, indicate an increased influence of AABW in the Indian Ocean due to a major increase in Antarctic ice volume. PCA1 is dominated by <em>Uvigerina proboscidea</em>, <em>Fissurina</em> spp.<em>,</em> and miliolids, indicating oxygen-poor bottom waters and high surface productivity between 1.7 and 0.5 Ma associated with an influence of NIDW. The high relative abundance of <em>U. proboscidea</em> and low relative abundance of <em>E. exigua</em> signify low seasonality and sustained flux of organic matter with a signature of strong South Equatorial Counter Current formed by the seasonal reversal of winds during 1.7–0.5 Ma at Site 709.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"657 ","pages":"Article 112612"},"PeriodicalIF":2.6,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.palaeo.2024.112610
Liang Yu , Maodu Yan , Mathew Domeier , Bingshuai Li , Miaomiao Shen , Chong Guan , Qiang Fu , Wanlong Xu , Zunbo Xu , Zhichao Niu , Dawen Zhang , Liye Yang
To constrain the drift history of the Eastern Qiangtang Terrane and the closure time of the Paleo-Jinshajiang Ocean, we conducted a paleomagnetic study of Late Triassic limestones in the Qamdo region of the Eastern Qiangtang Terrane. The results of the rock magnetic, petrographic, and reversal test indicate the limestones carry primary magnetizations. Our new paleomagnetic data provide a Late Triassic paleopole of 30.9°N, 161.4°E (A95 = 8.4°), which corresponds to a paleolatitude of 35 ± 8.4°N for the study area. Integrating these data with existing paleomagnetic results and geological evidence, we determine that the Eastern Qiangtang Terrane was situated at a relatively constant paleolatitudinal position without significant N-S displacements during ∼230–209 Ma. We conclude that the Paleo-Jinshajiang Ocean in the Qamdo region had already closed before ∼221 Ma, and likely around ∼230 Ma.
{"title":"New Paleomagnetic results from Late Triassic limestone of the Eastern Qiangtang Terrane: Implications for the closure of the Paleo-Jinshajiang Ocean","authors":"Liang Yu , Maodu Yan , Mathew Domeier , Bingshuai Li , Miaomiao Shen , Chong Guan , Qiang Fu , Wanlong Xu , Zunbo Xu , Zhichao Niu , Dawen Zhang , Liye Yang","doi":"10.1016/j.palaeo.2024.112610","DOIUrl":"10.1016/j.palaeo.2024.112610","url":null,"abstract":"<div><div>To constrain the drift history of the Eastern Qiangtang Terrane and the closure time of the Paleo-Jinshajiang Ocean, we conducted a paleomagnetic study of Late Triassic limestones in the Qamdo region of the Eastern Qiangtang Terrane. The results of the rock magnetic, petrographic, and reversal test indicate the limestones carry primary magnetizations. Our new paleomagnetic data provide a Late Triassic paleopole of 30.9°N, 161.4°E (A<sub>95</sub> = 8.4°), which corresponds to a paleolatitude of 35 ± 8.4°N for the study area. Integrating these data with existing paleomagnetic results and geological evidence, we determine that the Eastern Qiangtang Terrane was situated at a relatively constant paleolatitudinal position without significant N-S displacements during ∼230–209 Ma. We conclude that the Paleo-Jinshajiang Ocean in the Qamdo region had already closed before ∼221 Ma, and likely around ∼230 Ma.</div></div>","PeriodicalId":19928,"journal":{"name":"Palaeogeography, Palaeoclimatology, Palaeoecology","volume":"657 ","pages":"Article 112610"},"PeriodicalIF":2.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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