This study presents multiproxy record of benthic foraminiferal assemblages, relative abundances of planktic foraminifer Globigerina bulloides, stable isotope ratios in benthic foraminifer Uvigerina peregrina, and signature of pyritization from Core SK291/GC17, located at a water depth of 182 m in the eastern Arabian Sea (EAS). The sediment core covers an age from ∼40,000 to 3500 calibrated years before present (cal yr BP). Distinctly high abundance of G. bulloides, suggests strong upwelling and high productivity driven by intense Indian summer monsoon (ISM) winds in the EAS during ∼40,000–29,000 cal yr BP, corresponding to the late Marine Isotope Stage 3 (MIS3). As the sea level was lower than the recent time in the MIS3, closer proximity of the core to the coast aided high continental influx, which led to eutrophic, oxygen deficient condition at the sediment-water interface. This hypoxic condition is evident from the subjugation of oxic benthic foraminifera and their very low species diversity. Framboidal pyrite aggregates were observed during the MIS 3, suggesting iron-rich continental influx to the study core followed by pyritization in the anoxic environment. During the Last Glacial Maximum (LGM), a lower sea level and weak ISM caused relatively mesotrophic (and better oxygenated) condition over Core SK291/GC17. The extreme eutrophic and associated hypoxic condition in the late MIS 3 at Core SK291/GC17 was never experienced in the younger intervals, with G. bulloides percentages showing continuous decrease.
{"title":"Changes in surface conditions and associated hypoxia since the late Marine Isotope Stage 3, eastern Arabian Sea","authors":"Jeet Majumder , Anil K. Gupta , Prasanta Sanyal , Rudra Narayan Mohanty","doi":"10.1016/j.gloplacha.2025.104734","DOIUrl":"10.1016/j.gloplacha.2025.104734","url":null,"abstract":"<div><div>This study presents multiproxy record of benthic foraminiferal assemblages, relative abundances of planktic foraminifer <em>Globigerina bulloides</em>, stable isotope ratios in benthic foraminifer <em>Uvigerina peregrina</em>, and signature of pyritization from Core SK291/GC17, located at a water depth of 182 m in the eastern Arabian Sea (EAS). The sediment core covers an age from ∼40,000 to 3500 calibrated years before present (cal yr BP). Distinctly high abundance of <em>G. bulloides</em>, suggests strong upwelling and high productivity driven by intense Indian summer monsoon (ISM) winds in the EAS during ∼40,000–29,000 cal yr BP, corresponding to the late Marine Isotope Stage 3 (MIS3). As the sea level was lower than the recent time in the MIS3, closer proximity of the core to the coast aided high continental influx, which led to eutrophic, oxygen deficient condition at the sediment-water interface. This hypoxic condition is evident from the subjugation of oxic benthic foraminifera and their very low species diversity. Framboidal pyrite aggregates were observed during the MIS 3, suggesting iron-rich continental influx to the study core followed by pyritization in the anoxic environment. During the Last Glacial Maximum (LGM), a lower sea level and weak ISM caused relatively mesotrophic (and better oxygenated) condition over Core SK291/GC17. The extreme eutrophic and associated hypoxic condition in the late MIS 3 at Core SK291/GC17 was never experienced in the younger intervals, with <em>G. bulloides</em> percentages showing continuous decrease.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104734"},"PeriodicalIF":4.0,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-29DOI: 10.1016/j.gloplacha.2025.104728
Laifeng Li , Shenghui Ouyang , Gen K. Li , David William Hedding
Chemical weathering of basalt plays a vital role in the long-term carbon cycle and Earth's habitability. Quantifying the magnitude and controlling factors of basalt weathering requires assessing the contribution to weathering solutes from groundwater, which has remained challenging. In this work, we apply radiogenic uranium isotope activity ratios (234U/238U) to trace groundwater input to riverine weathering solutes in an inactive volcanic field from East China. Dissolved (234U/238U) is closely tied to the residence time of water bodies on the Earth's surface, allowing us to separate surface weathering solutes and groundwater characterized by distinct flow paths and residence time. We constrain the surface-weathering and groundwater end-members using hillslope-weathering solutes and spring waters, respectively. Based on the (234U/238U) ratios of the collected end-member samples, we developed a mass balance model and determined that groundwater contributes significantly to riverine solutes (∼41.5 %) but only has a minor contribution (∼10 %) to the water in man-made reservoirs in the study area. The estimated basalt weathering rates based on the alkalinity of river water may deviate from the global trend between basalt weathering rates and temperature if the contribution of groundwater is not corrected. Overall, our findings highlight the necessity to account for the influence of groundwater when estimating basalt weathering rates using river water, whereas man-made reservoirs may be less prone to groundwater inputs.
{"title":"Significant contribution of groundwater to the basalt weathering flux in an inactive volcanic field: Evidence from radiogenic uranium isotope","authors":"Laifeng Li , Shenghui Ouyang , Gen K. Li , David William Hedding","doi":"10.1016/j.gloplacha.2025.104728","DOIUrl":"10.1016/j.gloplacha.2025.104728","url":null,"abstract":"<div><div>Chemical weathering of basalt plays a vital role in the long-term carbon cycle and Earth's habitability. Quantifying the magnitude and controlling factors of basalt weathering requires assessing the contribution to weathering solutes from groundwater, which has remained challenging. In this work, we apply radiogenic uranium isotope activity ratios (<sup>234</sup>U/<sup>238</sup>U) to trace groundwater input to riverine weathering solutes in an inactive volcanic field from East China. Dissolved (<sup>234</sup>U/<sup>238</sup>U) is closely tied to the residence time of water bodies on the Earth's surface, allowing us to separate surface weathering solutes and groundwater characterized by distinct flow paths and residence time. We constrain the surface-weathering and groundwater end-members using hillslope-weathering solutes and spring waters, respectively. Based on the (<sup>234</sup>U/<sup>238</sup>U) ratios of the collected end-member samples, we developed a mass balance model and determined that groundwater contributes significantly to riverine solutes (∼41.5 %) but only has a minor contribution (∼10 %) to the water in man-made reservoirs in the study area. The estimated basalt weathering rates based on the alkalinity of river water may deviate from the global trend between basalt weathering rates and temperature if the contribution of groundwater is not corrected. Overall, our findings highlight the necessity to account for the influence of groundwater when estimating basalt weathering rates using river water, whereas man-made reservoirs may be less prone to groundwater inputs.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104728"},"PeriodicalIF":4.0,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-28DOI: 10.1016/j.gloplacha.2025.104732
Chaoyong Wang , Kan Zhang , Zhimian Cao , Kuanbo Zhou , Zhongwei Yuan , Junhui Chen , Yifan Ma , Bei Zhou , Xin Liu , Yihua Cai , Dalin Shi , Minhan Dai
Particulate C:N:P:Si ratios and their variations in the upper ocean are crucial for understanding carbon export and its coupling with nutrient dynamics and phytoplankton community composition associated with nutrient limitation. Here, we present the first dataset of size-fractionated biogenic particle concentrations and their elemental ratios, including particulate organic carbon (POC), particulate nitrogen (PN), particulate phosphorus (PP), and biogenic silica (BSi), in the upper 500 m of the water column in the subtropical western North Pacific. The highest POC, PN, and PP concentrations consistently occurred in surface water and then decreased with increasing depth, whereas BSi concentration was frequently highest in the subsurface chlorophyll maximum layer at ∼ 120 m. The small size fraction (SSF, 0.8 or 1–51 μm) dominated the total pool of POC, PN, and PP but contributed less to the total BSi pool than the large size fraction (LSF, >51 μm). This feature was accompanied by lower C:N, C:P, and N:P ratios and higher C:Si ratios in the SSF than in the LSF. In the euphotic zone, total particulate C:N, C:P, N:P, and C:Si ratios averaged 8 ± 1, 146 ± 30, 17 ± 3, and 120 ± 48 mol:mol respectively, and exceeded the canonical Redfield and Brzezinski ratio. The three former ratios aligned with cellular C:N:P ratios of Prochlorococcus and Synechococcus. Moreover, these ratios exhibited observable latitudinal gradients; they were generally higher in the gyre center than in its southern boundary occupied by the North Equatorial Current. Below the euphotic zone down to 500 m, there was a distinct increase in SSF molar C:N, C:P, and N:P ratios with depth, while total particulate molar C:Si ratios remained relatively constant. Combined with data collected in the subtropical eastern South Pacific and North Atlantic, our results demonstrate that the composition of the phytoplankton community primarily controls particulate molar C:N:P:Si stoichiometry in the euphotic zone of ocean gyres, in particular in the SSF, below which preferential remineralization of various bioelements plays an important role.
{"title":"Size-fractionated C:N:P:Si stoichiometry of particulate matter in the subtropical Western North Pacific","authors":"Chaoyong Wang , Kan Zhang , Zhimian Cao , Kuanbo Zhou , Zhongwei Yuan , Junhui Chen , Yifan Ma , Bei Zhou , Xin Liu , Yihua Cai , Dalin Shi , Minhan Dai","doi":"10.1016/j.gloplacha.2025.104732","DOIUrl":"10.1016/j.gloplacha.2025.104732","url":null,"abstract":"<div><div>Particulate C:N:P:Si ratios and their variations in the upper ocean are crucial for understanding carbon export and its coupling with nutrient dynamics and phytoplankton community composition associated with nutrient limitation. Here, we present the first dataset of size-fractionated biogenic particle concentrations and their elemental ratios, including particulate organic carbon (POC), particulate nitrogen (PN), particulate phosphorus (PP), and biogenic silica (BSi), in the upper 500 m of the water column in the subtropical western North Pacific. The highest POC, PN, and PP concentrations consistently occurred in surface water and then decreased with increasing depth, whereas BSi concentration was frequently highest in the subsurface chlorophyll maximum layer at ∼ 120 m. The small size fraction (SSF, 0.8 or 1–51 μm) dominated the total pool of POC, PN, and PP but contributed less to the total BSi pool than the large size fraction (LSF, >51 μm). This feature was accompanied by lower C:N, C:P, and N:P ratios and higher C:Si ratios in the SSF than in the LSF. In the euphotic zone, total particulate C:N, C:P, N:P, and C:Si ratios averaged 8 ± 1, 146 ± 30, 17 ± 3, and 120 ± 48 mol:mol respectively, and exceeded the canonical Redfield and Brzezinski ratio. The three former ratios aligned with cellular C:N:P ratios of <em>Prochlorococcus</em> and <em>Synechococcus</em>. Moreover, these ratios exhibited observable latitudinal gradients; they were generally higher in the gyre center than in its southern boundary occupied by the North Equatorial Current. Below the euphotic zone down to 500 m, there was a distinct increase in SSF molar C:N, C:P, and N:P ratios with depth, while total particulate molar C:Si ratios remained relatively constant. Combined with data collected in the subtropical eastern South Pacific and North Atlantic, our results demonstrate that the composition of the phytoplankton community primarily controls particulate molar C:N:P:Si stoichiometry in the euphotic zone of ocean gyres, in particular in the SSF, below which preferential remineralization of various bioelements plays an important role.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104732"},"PeriodicalIF":4.0,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-28DOI: 10.1016/j.gloplacha.2025.104731
Lina Ai , Shengfa Liu , Hui Zhang , Peng Cao , Xiao Wu , Lianhua He , Wenjing Qi , Kaikai Wu , Che Abd Rahim Mohamed , Houjie Wang , Xuefa Shi
The Malacca Strait connects the Sunda Shelf and Andaman Sea, which is a chokepoint for the exchange of both material and energy between two larger bodies of water. However, the evolutionary history of the Malacca Strait is poorly understood, although its development can be closely linked to regional paleoenvironmental changes. In this study, we present multiple new analytical results on the basis of a high-resolution chronology, including grain size, geochemical composition, and SrNd isotopic compositions in both labile and detrital fractions of sediments from surface samples as well as core samples. We aim to reveal the evolutionary history of the Malacca Strait by tracing records of the geochemical compositions and SrNd isotopic compositions of both labile and detrital fractions of sediments. A provenance transition between ∼10 and ∼7 ka has been identified, with the occurrence of a Sunda Shelf sediment signal at approximately 10 ka. Combining the shifting provenance and varying depositional environment since 16.28 ka allows us to distinguish three distinct evolutionary stages of the Malacca Strait: 1) Stage I, during 10–15 ka, a general estuary and embayment environment with provenances from the Malaysian Peninsula, Sumatra and the eastern shelf of the Andaman Sea; 2) Stage II, during the early Holocene at 10–7 ka, a period of an initial strait configuration with a narrow and shallow channel, which only allowed restricted sediment and water mass influx into the strait; and 3) Stage III, a highstand of sea level since ∼7 ka, a phase of a fully opened strait with a high-energy hydrodynamic environment dominated by tidal and northwestward currents. It suggested that the initial opening of the strait may have been incapable of providing higher-energy depositional environments, such as those present today, whereas the optimal sea level since 7.26 ka promoted throughflow in the Malacca Strait. Our results demonstrate that sea level was the first-order control of sedimentary evolution in the strait, whereas the monsoon climate only played a secondary role.
{"title":"Evolutionary history of the Malacca Strait driven by sea level changes over the last 16 ka","authors":"Lina Ai , Shengfa Liu , Hui Zhang , Peng Cao , Xiao Wu , Lianhua He , Wenjing Qi , Kaikai Wu , Che Abd Rahim Mohamed , Houjie Wang , Xuefa Shi","doi":"10.1016/j.gloplacha.2025.104731","DOIUrl":"10.1016/j.gloplacha.2025.104731","url":null,"abstract":"<div><div>The Malacca Strait connects the Sunda Shelf and Andaman Sea, which is a chokepoint for the exchange of both material and energy between two larger bodies of water. However, the evolutionary history of the Malacca Strait is poorly understood, although its development can be closely linked to regional paleoenvironmental changes. In this study, we present multiple new analytical results on the basis of a high-resolution chronology, including grain size, geochemical composition, and Sr<img>Nd isotopic compositions in both labile and detrital fractions of sediments from surface samples as well as core samples. We aim to reveal the evolutionary history of the Malacca Strait by tracing records of the geochemical compositions and Sr<img>Nd isotopic compositions of both labile and detrital fractions of sediments. A provenance transition between ∼10 and ∼7 ka has been identified, with the occurrence of a Sunda Shelf sediment signal at approximately 10 ka. Combining the shifting provenance and varying depositional environment since 16.28 ka allows us to distinguish three distinct evolutionary stages of the Malacca Strait: 1) Stage I, during 10–15 ka, a general estuary and embayment environment with provenances from the Malaysian Peninsula, Sumatra and the eastern shelf of the Andaman Sea; 2) Stage II, during the early Holocene at 10–7 ka, a period of an initial strait configuration with a narrow and shallow channel, which only allowed restricted sediment and water mass influx into the strait; and 3) Stage III, a highstand of sea level since ∼7 ka, a phase of a fully opened strait with a high-energy hydrodynamic environment dominated by tidal and northwestward currents. It suggested that the initial opening of the strait may have been incapable of providing higher-energy depositional environments, such as those present today, whereas the optimal sea level since 7.26 ka promoted throughflow in the Malacca Strait. Our results demonstrate that sea level was the first-order control of sedimentary evolution in the strait, whereas the monsoon climate only played a secondary role.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104731"},"PeriodicalIF":4.0,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-28DOI: 10.1016/j.gloplacha.2025.104721
Wenhong Johnson Qiu , Mei-Fu Zhou , John Malpas , Jie Li , Zerui Ray Liu , Yafei Wu
Although the Phanerozoic ocean was generally oxygenated, local euxinic events occurred frequently, as witnessed by the widespread Paleozoic sediment-hosted stratiform sulfide (SHSS) deposits. Here, we use redox-sensitive Fe speciation and Mo isotopes of black shales and pyrite ores of the Devonian Dajiangping stratiform pyrite deposit in the South China Block (SCB) to decipher the linkage between redox conditions, basin restrictions and SHSS mineralization. From bottom to top, the host sedimentary succession on the deposit margin is a transgressive sequence of siltstones, carbonaceous limestones and black shales. The ratios of highly reactive Fe to total Fe (FeHR/FeT: 0.29 to 1.0), Fe in pyrite to highly reactive Fe (Fepy/FeHR: 0.09 to 0.91), and δ98/95Mo (0.50 ‰ to 1.30 ‰), show consistently increasing trends upward throughout the stratigraphic sequence, indicative of changes in the redox of bottom seawater from oxic, through anoxic, to weakly euxinic, in response to the subsidence of the basin. Black shales and interlayered laminated pyrite ores on the deposit center have δ98/95Mo varying from +0.90 to +1.50 ‰ and higher than the host succession, clearly demonstrating the redox condition of bottom seawater in the depocenter is more euxinic than the margin of the basin. These δ98/95Mo values lower than those of seawater were resulted from the occurrence of thimolybdates with variable Mo isotopic fractionations in the weakly euxinc conditions. In addition, the positive correlation (R2 = 0.84) between Mo concentrations and total organic carbon (TOC) of the black shales suggests that Mo was authigenic in origin. These black shales have Mo/TOC of ∼1.7 ppm/wt%, which are much lower than those in poorly or unconfined euxinic basins (Mo/TOC > 11 ppm/wt%) and indicative of a restricted basin environment. The redox conditions of seawater changed from oxic to anoxic on the basin margin but maintained weakly euxinic in the basin center, consistent with a basinal environment showing subsidence and restriction. Such a restricted basin was due to the rifting of a fault-bounded trough on the passive margin of the SCB during the Devonian. Our study highlights the importance of locally restricted basins with euxinic and stratified seawater environments for the extensive development of SHSS deposits in an oxygenated Phanerozoic ocean.
{"title":"Development of weakly euxinic basin environments in the Phanerozoic oxic ocean: Insights from Fe speciation and Mo isotopes of Devonian pyrite-bearing black shales, Dajiangping pyrite mine, South China","authors":"Wenhong Johnson Qiu , Mei-Fu Zhou , John Malpas , Jie Li , Zerui Ray Liu , Yafei Wu","doi":"10.1016/j.gloplacha.2025.104721","DOIUrl":"10.1016/j.gloplacha.2025.104721","url":null,"abstract":"<div><div>Although the Phanerozoic ocean was generally oxygenated, local euxinic events occurred frequently, as witnessed by the widespread Paleozoic sediment-hosted stratiform sulfide (SHSS) deposits. Here, we use redox-sensitive Fe speciation and Mo isotopes of black shales and pyrite ores of the Devonian Dajiangping stratiform pyrite deposit in the South China Block (SCB) to decipher the linkage between redox conditions, basin restrictions and SHSS mineralization. From bottom to top, the host sedimentary succession on the deposit margin is a transgressive sequence of siltstones, carbonaceous limestones and black shales. The ratios of highly reactive Fe to total Fe (Fe<sub>HR</sub>/Fe<sub>T</sub>: 0.29 to 1.0), Fe in pyrite to highly reactive Fe (Fe<sub>py</sub>/Fe<sub>HR</sub>: 0.09 to 0.91), and δ<sup>98/95</sup>Mo (0.50 ‰ to 1.30 ‰), show consistently increasing trends upward throughout the stratigraphic sequence, indicative of changes in the redox of bottom seawater from oxic, through anoxic, to weakly euxinic, in response to the subsidence of the basin. Black shales and interlayered laminated pyrite ores on the deposit center have δ<sup>98/95</sup>Mo varying from +0.90 to +1.50 ‰ and higher than the host succession, clearly demonstrating the redox condition of bottom seawater in the depocenter is more euxinic than the margin of the basin. These δ<sup>98/95</sup>Mo values lower than those of seawater were resulted from the occurrence of thimolybdates with variable Mo isotopic fractionations in the weakly euxinc conditions. In addition, the positive correlation (R<sup>2</sup> = 0.84) between Mo concentrations and total organic carbon (TOC) of the black shales suggests that Mo was authigenic in origin. These black shales have Mo/TOC of ∼1.7 ppm/wt%, which are much lower than those in poorly or unconfined euxinic basins (Mo/TOC > 11 ppm/wt%) and indicative of a restricted basin environment. The redox conditions of seawater changed from oxic to anoxic on the basin margin but maintained weakly euxinic in the basin center, consistent with a basinal environment showing subsidence and restriction. Such a restricted basin was due to the rifting of a fault-bounded trough on the passive margin of the SCB during the Devonian. Our study highlights the importance of locally restricted basins with euxinic and stratified seawater environments for the extensive development of SHSS deposits in an oxygenated Phanerozoic ocean.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"248 ","pages":"Article 104721"},"PeriodicalIF":4.0,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-27DOI: 10.1016/j.gloplacha.2025.104724
Yunqi Zhang , Bangrun Guo , Wei Li , Lan Tang , Xinxin Zhang , Yi Long , Xinbao Zhang , Bo Tan , Ziteng Luo , Xun Hu , Yong Wang
Previous studies have examined sediment yields and erosion in karst settings over recent decades, with little consideration of the evolution of rocky desertification over longer timescales. Here we reconstruct sediment yields from karst terrain in SW China over the past 600+ years by dating sediment deposition in a representative karst depression, and assess the contribution of historical sediment yields to rocky desertification. Results indicate that area-specific sediment yields (SSYs) during the early stage of sediment deposition (1368–1652) were the highest, triggered by deforestation and then cultivation associated with the first Hu-Guang Fills Sichuan migration during the Ming Dynasty. The relatively high SSYs during the middle stage (1653–1922) were related mainly to cultivation associated with the second Hu-Guang Fills Sichuan migration rather than deforestation, including the introduction of maize (Zea mays) and sweet potato (Ipomoea batatas) during the Qing Dynasty. SSYs increased again during the modern stage (1923–1962) due to massive deforestation at the end of the 1950s. During the latest stage (1963–2022), SSYs were the lowest as a result of increasing rocky desertification, reduced human disturbance, and the restoration of vegetation. The contributions of sediment yield to rocky desertification decreased across the middle, modern and latest stages, suggesting that the present-day rocky desertification was caused mainly by sediment yield stimulated by human activity over the past 500+ years before 1923, rather than over recent decades. Overall, our study provides more-comprehensive insights into the dynamics of rocky desertification over long timescales.
{"title":"Reduction in sediment yields from karst terrain in SW China over the past 600+ years","authors":"Yunqi Zhang , Bangrun Guo , Wei Li , Lan Tang , Xinxin Zhang , Yi Long , Xinbao Zhang , Bo Tan , Ziteng Luo , Xun Hu , Yong Wang","doi":"10.1016/j.gloplacha.2025.104724","DOIUrl":"10.1016/j.gloplacha.2025.104724","url":null,"abstract":"<div><div>Previous studies have examined sediment yields and erosion in karst settings over recent decades, with little consideration of the evolution of rocky desertification over longer timescales. Here we reconstruct sediment yields from karst terrain in SW China over the past 600+ years by dating sediment deposition in a representative karst depression, and assess the contribution of historical sediment yields to rocky desertification. Results indicate that area-specific sediment yields (<em>SSYs</em>) during the early stage of sediment deposition (1368–1652) were the highest, triggered by deforestation and then cultivation associated with the first Hu-Guang Fills Sichuan migration during the Ming Dynasty. The relatively high <em>SSYs</em> during the middle stage (1653–1922) were related mainly to cultivation associated with the second Hu-Guang Fills Sichuan migration rather than deforestation, including the introduction of maize (<em>Zea mays</em>) and sweet potato (<em>Ipomoea batatas</em>) during the Qing Dynasty. <em>SSYs</em> increased again during the modern stage (1923–1962) due to massive deforestation at the end of the 1950s. During the latest stage (1963–2022), <em>SSYs</em> were the lowest as a result of increasing rocky desertification, reduced human disturbance, and the restoration of vegetation. The contributions of sediment yield to rocky desertification decreased across the middle, modern and latest stages, suggesting that the present-day rocky desertification was caused mainly by sediment yield stimulated by human activity over the past 500+ years before 1923, rather than over recent decades. Overall, our study provides more-comprehensive insights into the dynamics of rocky desertification over long timescales.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104724"},"PeriodicalIF":4.0,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-25DOI: 10.1016/j.gloplacha.2025.104727
Huiyuan Yang , Jian Ma , Songfan He , Jin Wang , Yongge Sun , Xingqian Cui
Weathering of rock-derived organic carbon (OC) is an important source of atmospheric CO2 in the global carbon cycle, contributing to the long-term regulation of climates. Despite numerous investigations on clastic rocks, weathering behaviors of OC in calcareous rocks remain poorly constrained due to their conventional recognition of organic-lean features. Here, we analyzed bulk OC and biomarkers along weathering profiles of organic-rich calcareous rocks from the Green River Formation. Total OC and ramped-temperature pyrolysis/oxidation results reveal a minimal degradation of OC. Given a substantial fraction of bulk OC and a rich pool of biomolecules preserved in carbonate matrix, our results suggest that the limited bulk-level degradation is attributed to the shielding of OC in carbonate matrix. Furthermore, contrasting biomarker proxies are observed between free and associated forms, implying that carbonate-associated lipids are resistant to degradation during weathering; whereas clearly decreasing patterns of free lipids at the molecular level correspond to weathering-induced microbial degradation of excluded OC. Overall, our findings reveal that calcareous rocks might be an overlooked, yet understudied, carbon pool involved in the global organic carbon cycle.
{"title":"Resistant degradation of petrogenic organic carbon in the weathering of calcareous rocks","authors":"Huiyuan Yang , Jian Ma , Songfan He , Jin Wang , Yongge Sun , Xingqian Cui","doi":"10.1016/j.gloplacha.2025.104727","DOIUrl":"10.1016/j.gloplacha.2025.104727","url":null,"abstract":"<div><div>Weathering of rock-derived organic carbon (OC) is an important source of atmospheric CO<sub>2</sub> in the global carbon cycle, contributing to the long-term regulation of climates. Despite numerous investigations on clastic rocks, weathering behaviors of OC in calcareous rocks remain poorly constrained due to their conventional recognition of organic-lean features. Here, we analyzed bulk OC and biomarkers along weathering profiles of organic-rich calcareous rocks from the Green River Formation. Total OC and ramped-temperature pyrolysis/oxidation results reveal a minimal degradation of OC. Given a substantial fraction of bulk OC and a rich pool of biomolecules preserved in carbonate matrix, our results suggest that the limited bulk-level degradation is attributed to the shielding of OC in carbonate matrix. Furthermore, contrasting biomarker proxies are observed between free and associated forms, implying that carbonate-associated lipids are resistant to degradation during weathering; whereas clearly decreasing patterns of free lipids at the molecular level correspond to weathering-induced microbial degradation of excluded OC. Overall, our findings reveal that calcareous rocks might be an overlooked, yet understudied, carbon pool involved in the global organic carbon cycle.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104727"},"PeriodicalIF":4.0,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-23DOI: 10.1016/j.gloplacha.2025.104723
Juan I. Santisteban , Rosa Mediavilla , Cristina Val-Peón , José Antonio López-Sáez , Klaus Reicherter
Projections based on the Intergovernmental Panel on Climate Change scenarios predict a clear rise of the sea level in the near future, together with a decrease in frequency and magnitude of fluvial floods, which are one of the main sources of sediments for some coasts, as response to a decrease in rainfall.
We present a fluvial flood series for the last 17,000 yrs. obtained from cores retrieved in a former restricted embayment by using a multiproxy approach (geochemistry, sedimentology, stratigraphy, palynology), with sub-decadal time-resolution. Flood subfacies are defined by their siliciclastic and saline components. Time distribution reveals that fluvial floods controlled sedimentation rates. Comparison against other records of the Southern Iberian Peninsula allows to identify common periods. For the end of the Pleistocene, low frequency floods are associated to Meltwater Pulses or Heinrich events. During early Holocene, there is a noticeable increase in flood frequency, reaching their maximum at the Holocene Thermal Maximum. The mid- to late-Holocene is characterized by a flood frequency clearly lower than the early Holocene one, but higher than the late Pleistocene one.
Millennial scale changes in insolation controlled atmospheric moisture which, in turn, determined evolution of floods. Centennial scale changes in irradiance were responsible of shorter-term flood episodes over moisture changes.
These results do not fully agree with the expected evolution of floods under IPCC projected scenarios, so further research is needed to improve our knowledge about flood behaviour.
{"title":"High- vs. low-rate of sea level change fluvial floods: Past analogues for future forecast","authors":"Juan I. Santisteban , Rosa Mediavilla , Cristina Val-Peón , José Antonio López-Sáez , Klaus Reicherter","doi":"10.1016/j.gloplacha.2025.104723","DOIUrl":"10.1016/j.gloplacha.2025.104723","url":null,"abstract":"<div><div>Projections based on the Intergovernmental Panel on Climate Change scenarios predict a clear rise of the sea level in the near future, together with a decrease in frequency and magnitude of fluvial floods, which are one of the main sources of sediments for some coasts, as response to a decrease in rainfall.</div><div>We present a fluvial flood series for the last 17,000 yrs. obtained from cores retrieved in a former restricted embayment by using a multiproxy approach (geochemistry, sedimentology, stratigraphy, palynology), with sub-decadal time-resolution. Flood subfacies are defined by their siliciclastic and saline components. Time distribution reveals that fluvial floods controlled sedimentation rates. Comparison against other records of the Southern Iberian Peninsula allows to identify common periods. For the end of the Pleistocene, low frequency floods are associated to Meltwater Pulses or Heinrich events. During early Holocene, there is a noticeable increase in flood frequency, reaching their maximum at the Holocene Thermal Maximum. The mid- to late-Holocene is characterized by a flood frequency clearly lower than the early Holocene one, but higher than the late Pleistocene one.</div><div>Millennial scale changes in insolation controlled atmospheric moisture which, in turn, determined evolution of floods. Centennial scale changes in irradiance were responsible of shorter-term flood episodes over moisture changes.</div><div>These results do not fully agree with the expected evolution of floods under IPCC projected scenarios, so further research is needed to improve our knowledge about flood behaviour.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104723"},"PeriodicalIF":4.0,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-22DOI: 10.1016/j.gloplacha.2025.104726
Xiangying Xi , Xixi Zhou , Xiaohui Liu , Youjia Zou
The Indian summer monsoon is characterized by exceptionally intense cross-equatorial southwest winds, with its underlying mechanism vigorously debated. From the perspective of the general circulation, changes in regional atmospheric circulation are also ambiguous. Here, we present our latest research results, which show that the Hadley cells over the Indian Ocean change from two cells in boreal winter to a single cell in boreal summer, due mainly to a strong meridional shift of the ascending branch of the Hadley cells. Simultaneously, an enhancement of the Mascarene High also occurs over the south Indian Ocean. The coincidence of a deepening of the Indian Low and an uncharacteristically enhancing of the Mascarene High is likely to contribute to a northward expansion of the southern cell, with the northern cell totally vanished in the north Indian Ocean in summer, resulting in the Indian summer monsoon. This is the first time that the Hadley cells have been identified as having considerable inter-hemispheric variability, calling into question the long-held belief that the Hadley cells only occur in one hemisphere.
{"title":"Alternative mechanism of the Indian summer monsoon formation","authors":"Xiangying Xi , Xixi Zhou , Xiaohui Liu , Youjia Zou","doi":"10.1016/j.gloplacha.2025.104726","DOIUrl":"10.1016/j.gloplacha.2025.104726","url":null,"abstract":"<div><div>The Indian summer monsoon is characterized by exceptionally intense cross-equatorial southwest winds, with its underlying mechanism vigorously debated. From the perspective of the general circulation, changes in regional atmospheric circulation are also ambiguous. Here, we present our latest research results, which show that the Hadley cells over the Indian Ocean change from two cells in boreal winter to a single cell in boreal summer, due mainly to a strong meridional shift of the ascending branch of the Hadley cells. Simultaneously, an enhancement of the Mascarene High also occurs over the south Indian Ocean. The coincidence of a deepening of the Indian Low and an uncharacteristically enhancing of the Mascarene High is likely to contribute to a northward expansion of the southern cell, with the northern cell totally vanished in the north Indian Ocean in summer, resulting in the Indian summer monsoon. This is the first time that the Hadley cells have been identified as having considerable inter-hemispheric variability, calling into question the long-held belief that the Hadley cells only occur in one hemisphere.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104726"},"PeriodicalIF":4.0,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143124907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2025-01-22DOI: 10.1016/j.gloplacha.2025.104720
Lingyun Wu, Aizhong Ye, Yunfei Wang, Qiaoqiao Li, Shengsheng Zhan
Extreme precipitation events have caused obvious damage to human environments and socioeconomic systems. However, the changes in extreme precipitation and their underlying causes remain unclear. This study analyzed daily precipitation data from 2254 meteorological stations across China from 1981 to 2018, focusing on two key extreme precipitation indicators: Max 1-day precipitation amount (Rx1day) and Max 5-day precipitation amount (Rx5day). Trend analysis was conducted for 17 river basin divisions using the Mann-Kendall method. We also applied the field significance test, a statistical method to evaluate whether a spatial pattern of locally significant results, to determine whether observed trends at individual stations were statistically significant or due to random variation. The results showed that 59.3 % and 58.6 % of the stations exhibited increasing trends in Rx1day and Rx5day, respectively, with significant trends identified at 5.4 % and 4.1 % of the stations. The field significance test revealed a significant increasing in Rx1day across China at the 5 % significance level. Among the 17 sub-basins, significant increases in extreme precipitation were observed in the Inland rivers of Xinjiang and Northern Tibet. The result was consistent with the warming and humidification trends in northwest China. We further analyzed the relationship between urbanization and extreme precipitation by using population density to distinguish rural and urban stations. We found that the spatial distribution of urban stations closely overlapped with stations experiencing increased extreme precipitation, while rural stations corresponded with those showing a decrease. With the progress of urbanization, variations in the trends observed at urban and rural stations have emerged. Nevertheless, urban stations exerted a more pronounced influence on the increasing trend of extreme precipitation.
{"title":"Urbanization influence on changes of extreme precipitation in mainland China","authors":"Lingyun Wu, Aizhong Ye, Yunfei Wang, Qiaoqiao Li, Shengsheng Zhan","doi":"10.1016/j.gloplacha.2025.104720","DOIUrl":"10.1016/j.gloplacha.2025.104720","url":null,"abstract":"<div><div>Extreme precipitation events have caused obvious damage to human environments and socioeconomic systems. However, the changes in extreme precipitation and their underlying causes remain unclear. This study analyzed daily precipitation data from 2254 meteorological stations across China from 1981 to 2018, focusing on two key extreme precipitation indicators: Max 1-day precipitation amount (Rx1day) and Max 5-day precipitation amount (Rx5day). Trend analysis was conducted for 17 river basin divisions using the Mann-Kendall method. We also applied the field significance test, a statistical method to evaluate whether a spatial pattern of locally significant results, to determine whether observed trends at individual stations were statistically significant or due to random variation. The results showed that 59.3 % and 58.6 % of the stations exhibited increasing trends in Rx1day and Rx5day, respectively, with significant trends identified at 5.4 % and 4.1 % of the stations. The field significance test revealed a significant increasing in Rx1day across China at the 5 % significance level. Among the 17 sub-basins, significant increases in extreme precipitation were observed in the Inland rivers of Xinjiang and Northern Tibet. The result was consistent with the warming and humidification trends in northwest China. We further analyzed the relationship between urbanization and extreme precipitation by using population density to distinguish rural and urban stations. We found that the spatial distribution of urban stations closely overlapped with stations experiencing increased extreme precipitation, while rural stations corresponded with those showing a decrease. With the progress of urbanization, variations in the trends observed at urban and rural stations have emerged. Nevertheless, urban stations exerted a more pronounced influence on the increasing trend of extreme precipitation.</div></div>","PeriodicalId":55089,"journal":{"name":"Global and Planetary Change","volume":"246 ","pages":"Article 104720"},"PeriodicalIF":4.0,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143055166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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