The timing and mechanisms of fluvial terrace formation along the Yangtze River in the Yichang region provide critical insights into the interplay between tectonics,climate,and river evolution.In this study,we present ...The timing and mechanisms of fluvial terrace formation along the Yangtze River in the Yichang region provide critical insights into the interplay between tectonics,climate,and river evolution.In this study,we present new cosmogenic nuclide isochron burial ages for the fifth(T5)and fourth(T4)terraces,yielding ages of 0.49±0.05 Ma and 0.35±0.04 Ma,respectively.By integrating our data with existing 14C and ESR ages for lower terraces,we reconstruct a detailed incision history,showing~85 m of river downcutting since the Middle Pleistocene.Incision rates varied over time,with a notable acceleration after 0.1 Ma coinciding with the Gonghe movement of the Tibetan Plateau,highlighting the role of tectonic uplift in driving fluvial incision.The formation of the fifth terrace is associated with the Kunlun–Huanghe uplift,while the development of the fourth terrace corresponds to the phase of regional uplift in the Qinling Mountains.Sedimentological evidence further indicates that terrace formation was influenced by both climatic and tectonic controls:while T4 aggraded during a glacial period,T5 formed during the interglacial MIS 13 under strong monsoonal conditions—demonstrating that major aggradation can occur during warm phases.However,sustained incision required tectonic forcing,as climatic transitions alone were insufficient to drive deep bedrock erosion.Our results also constrain the longdebated integration of the Three Gorges.The 0.49 Ma age for T5 provides a robust minimum age for the hydrological connection between the Sichuan and Jianghan Basins.This timing,combined with the earlier formation of the"First Bend of the Yangtze"(Eocene–Miocene),contradicts the classical east-towest headward erosion model.Instead,geomorphic analysis of the gorges—showing diachronous valley development from east to west—supports a progressive,bottom-to-top integration,initiated in the Xiling Gorge and culminating in the incision of the Qutang Gorge.This sequence aligns with knickpoint migration driven by base-level fall and regional tectonic uplift.We conclude that the evolution of the Yangtze River through the Three Gorges is the result of a complex interplay between climate,tectonics,and base-level dynamics,with terraces serving as key archives of landscape response to these forces.展开更多
Objective The Qinling Mountains （QM） in Central China is a natural harrier that corresponds to the boundary between the southern and northern climate and environment （Gong Hujun et al., 2017）. Northern QM is rela...Objective The Qinling Mountains （QM） in Central China is a natural harrier that corresponds to the boundary between the southern and northern climate and environment （Gong Hujun et al., 2017）. Northern QM is relatively steep, and southern QM is in contrast relatively low and gentle. Investigations have shown that the average uplift rate of northern QM since 17.8 Ma is approximately 0.19 mm/a （Yin Gongming et al., 2001）, whereas that of central QM since 0.36 Ma is approximately 0.32 mm/a （Wang Fei et al., 2004）. To date, however, few investigations have yet been conducted on the uplift rate of southern QM. Accordingly, we aim to obtain the uplift rate of southern QM by using the cosmogenic ^26A1/^10 Be burial dating method to determine the age of the highest river terrace on the southern slope of QM.展开更多
了解浅水湖泊沉积物有机碳埋藏的时空分布规律及其影响因素对于深入认识这类湖泊碳埋藏过程及正确评价其在区域/全球碳循环中的作用具有重要意义。通过在巢湖东、西湖区采集沉积物柱状样,应用210Pbex-239+240Pu复合定年法建立沉积物年...了解浅水湖泊沉积物有机碳埋藏的时空分布规律及其影响因素对于深入认识这类湖泊碳埋藏过程及正确评价其在区域/全球碳循环中的作用具有重要意义。通过在巢湖东、西湖区采集沉积物柱状样,应用210Pbex-239+240Pu复合定年法建立沉积物年代序列,利用沉积物中总有机碳(TOC)、总氮(TN)、总磷(TP)、碳氮比(C/N)、常微量元素和粒度等指标,结合流域历史数据资料分析,研究了巢湖有机碳埋藏的时空变化特征及其影响因素。结果表明,210Pbex-239+240Pu复合计年法估算得到近70年巢湖沉积速率和有机碳埋藏速率的变化范围分别为0.19~0.90 g cm^(-2)a^(-1)和16.6~71.2 gC m^(-2)a^(-1),均呈现出随时间先降后增的变化趋势,且总体东部湖区均快于西部湖区;巢湖东西湖区沉积物中有机碳的来源均主要为内源,东部湖区沉积物中较快的有机碳埋藏速率主要归因于其较快的沉积速率及较深的水位阻碍了沉积物中有机碳的分解与矿化;而西部湖区则是由于强烈的人类活动带来的湖泊底泥扰动以及藻源性有机质自身的性质促进了有机碳在沉积-埋藏过程中的降解和矿化,影响了其沉积物中有机碳的有效埋藏。此外,流域增温、经济快速发展、人口数量增加、农业化肥施用量提升等流域气候变化和人类活动因素均给巢湖近70年来的有机碳埋藏带来积极影响。展开更多
基金supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea(NRF2023S1A5A2A01077716)。
文摘The timing and mechanisms of fluvial terrace formation along the Yangtze River in the Yichang region provide critical insights into the interplay between tectonics,climate,and river evolution.In this study,we present new cosmogenic nuclide isochron burial ages for the fifth(T5)and fourth(T4)terraces,yielding ages of 0.49±0.05 Ma and 0.35±0.04 Ma,respectively.By integrating our data with existing 14C and ESR ages for lower terraces,we reconstruct a detailed incision history,showing~85 m of river downcutting since the Middle Pleistocene.Incision rates varied over time,with a notable acceleration after 0.1 Ma coinciding with the Gonghe movement of the Tibetan Plateau,highlighting the role of tectonic uplift in driving fluvial incision.The formation of the fifth terrace is associated with the Kunlun–Huanghe uplift,while the development of the fourth terrace corresponds to the phase of regional uplift in the Qinling Mountains.Sedimentological evidence further indicates that terrace formation was influenced by both climatic and tectonic controls:while T4 aggraded during a glacial period,T5 formed during the interglacial MIS 13 under strong monsoonal conditions—demonstrating that major aggradation can occur during warm phases.However,sustained incision required tectonic forcing,as climatic transitions alone were insufficient to drive deep bedrock erosion.Our results also constrain the longdebated integration of the Three Gorges.The 0.49 Ma age for T5 provides a robust minimum age for the hydrological connection between the Sichuan and Jianghan Basins.This timing,combined with the earlier formation of the"First Bend of the Yangtze"(Eocene–Miocene),contradicts the classical east-towest headward erosion model.Instead,geomorphic analysis of the gorges—showing diachronous valley development from east to west—supports a progressive,bottom-to-top integration,initiated in the Xiling Gorge and culminating in the incision of the Qutang Gorge.This sequence aligns with knickpoint migration driven by base-level fall and regional tectonic uplift.We conclude that the evolution of the Yangtze River through the Three Gorges is the result of a complex interplay between climate,tectonics,and base-level dynamics,with terraces serving as key archives of landscape response to these forces.
基金supported by the National Natural Science Foundation of China(grants No.41572155 and 41690111)the Global Change Program of the Ministry of Science and Technology of China(grant No.2016YFA0600503)
文摘Objective The Qinling Mountains （QM） in Central China is a natural harrier that corresponds to the boundary between the southern and northern climate and environment （Gong Hujun et al., 2017）. Northern QM is relatively steep, and southern QM is in contrast relatively low and gentle. Investigations have shown that the average uplift rate of northern QM since 17.8 Ma is approximately 0.19 mm/a （Yin Gongming et al., 2001）, whereas that of central QM since 0.36 Ma is approximately 0.32 mm/a （Wang Fei et al., 2004）. To date, however, few investigations have yet been conducted on the uplift rate of southern QM. Accordingly, we aim to obtain the uplift rate of southern QM by using the cosmogenic ^26A1/^10 Be burial dating method to determine the age of the highest river terrace on the southern slope of QM.
文摘了解浅水湖泊沉积物有机碳埋藏的时空分布规律及其影响因素对于深入认识这类湖泊碳埋藏过程及正确评价其在区域/全球碳循环中的作用具有重要意义。通过在巢湖东、西湖区采集沉积物柱状样,应用210Pbex-239+240Pu复合定年法建立沉积物年代序列,利用沉积物中总有机碳(TOC)、总氮(TN)、总磷(TP)、碳氮比(C/N)、常微量元素和粒度等指标,结合流域历史数据资料分析,研究了巢湖有机碳埋藏的时空变化特征及其影响因素。结果表明,210Pbex-239+240Pu复合计年法估算得到近70年巢湖沉积速率和有机碳埋藏速率的变化范围分别为0.19~0.90 g cm^(-2)a^(-1)和16.6~71.2 gC m^(-2)a^(-1),均呈现出随时间先降后增的变化趋势,且总体东部湖区均快于西部湖区;巢湖东西湖区沉积物中有机碳的来源均主要为内源,东部湖区沉积物中较快的有机碳埋藏速率主要归因于其较快的沉积速率及较深的水位阻碍了沉积物中有机碳的分解与矿化;而西部湖区则是由于强烈的人类活动带来的湖泊底泥扰动以及藻源性有机质自身的性质促进了有机碳在沉积-埋藏过程中的降解和矿化,影响了其沉积物中有机碳的有效埋藏。此外,流域增温、经济快速发展、人口数量增加、农业化肥施用量提升等流域气候变化和人类活动因素均给巢湖近70年来的有机碳埋藏带来积极影响。
