长江将大量泥沙排入东海,对杭州湾的沉积演变产生重大影响,但长江型碎屑对杭州湾不同时期、不同位置的贡献差异缺乏研究。通过分析杭州湾舟山海域水下钻孔(HZW1907孔)沉积物中有机、无机元素地球化学特征,对杭州湾沉积过程中的水体古盐...长江将大量泥沙排入东海,对杭州湾的沉积演变产生重大影响,但长江型碎屑对杭州湾不同时期、不同位置的贡献差异缺乏研究。通过分析杭州湾舟山海域水下钻孔(HZW1907孔)沉积物中有机、无机元素地球化学特征,对杭州湾沉积过程中的水体古盐度、源区风化过程、沉积物组成与来源和长江–杭州湾–东海陆架沉积系统进行研究,并基于稀土元素组成的两端元混合模型,定量探讨长江泥沙对杭州湾不同位置沉积的贡献程度差异。结果表明,杭州湾湾口从晚更新世以来,经历了冰期的下切河谷深切、河谷充填和河谷埋藏3个阶段演化过程,相应发育了河床相(约33.9~23.7kaBP)、河漫滩相(约23.7~12.0kaBP)、古河口湾相(约12.0~9.0 ka BP)、浅海相(约9.0~4.0 ka BP)和现代河口湾相(约4.0 ka BP至今);沉积物的Ga/Rb和K_(2)O/Al_(2)O_(3)关系揭示了中国东部在33.9 ka BP以来经历了冷干–暖湿的气候变化;TS和TOC的变化反映了淡水–不稳定淡水、海水混合–稳定海水的沉积水体演替,与东海陆架一致。晚更新世期间,杭州湾地区发育的河床相、河漫滩相沉积物源区主要来自钱塘江流域,显示长英质火成岩的特征;全新世以来的古河口湾相、浅海相和现代河口湾相沉积物为钱塘江型碎屑与长江型碎屑的混合,显示中基性火成岩的特征,湾口受到长江物质的影响更强。以长江和钱塘江流域(Gd/Yb)_(UCC)为端元的模拟结果显示,杭州湾湾口与湾顶受到长江物质影响差异较大,古河口湾相时期,长江供给杭州湾湾口沉积物约78%,湾顶约39%;浅海相时期,长江供给杭州湾地区超过80%的碎屑,湾口、湾顶无明显差别;现代河口湾相时期,长江供给湾口沉积物约76%,湾顶约22%。该模拟方法在长江向杭州湾输送的碎屑分析中具有定量化的作用,并有望适用于其他沿海陆架河流系统。展开更多
A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare e...A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.展开更多
亚洲内陆荒漠化和干旱化与中国西部人类生存环境和社会可持续发展密切相关。中国西部地区的气候自晚更新世以来经历了多次冷暖、干湿变化,研究其晚更新世古气候变化,有助于预测未来气候的变化趋势。文章分析了宁夏南部清水河盆地晚更新...亚洲内陆荒漠化和干旱化与中国西部人类生存环境和社会可持续发展密切相关。中国西部地区的气候自晚更新世以来经历了多次冷暖、干湿变化,研究其晚更新世古气候变化,有助于预测未来气候的变化趋势。文章分析了宁夏南部清水河盆地晚更新世中晚期的孢粉记录,结果显示孢粉序列可从下至上划分为4个组合带,反映了该地区晚更新世中晚期植被和气候变化规律。研究表明研究区晚更新世中期(75~50 ka B.P.)是植被以蒿属为主的干草原,气候温凉偏干;晚更新世晚期(25~15 ka B.P.)由荒漠草原-干草原和疏林草原交替出现逐渐过渡到荒漠草原,该时期冬季风呈现逐渐增强的趋势,致使气候逐渐变冷变干,气候类型由温凉偏湿过渡到冷干。宁夏南部清水河盆地晚更新世中晚期孢粉记录的深入研究对于正确认识黄土高原自然环境历史演变和黄土高原治理决策的制定具有重要指导意义。展开更多
文摘长江将大量泥沙排入东海,对杭州湾的沉积演变产生重大影响,但长江型碎屑对杭州湾不同时期、不同位置的贡献差异缺乏研究。通过分析杭州湾舟山海域水下钻孔(HZW1907孔)沉积物中有机、无机元素地球化学特征,对杭州湾沉积过程中的水体古盐度、源区风化过程、沉积物组成与来源和长江–杭州湾–东海陆架沉积系统进行研究,并基于稀土元素组成的两端元混合模型,定量探讨长江泥沙对杭州湾不同位置沉积的贡献程度差异。结果表明,杭州湾湾口从晚更新世以来,经历了冰期的下切河谷深切、河谷充填和河谷埋藏3个阶段演化过程,相应发育了河床相(约33.9~23.7kaBP)、河漫滩相(约23.7~12.0kaBP)、古河口湾相(约12.0~9.0 ka BP)、浅海相(约9.0~4.0 ka BP)和现代河口湾相(约4.0 ka BP至今);沉积物的Ga/Rb和K_(2)O/Al_(2)O_(3)关系揭示了中国东部在33.9 ka BP以来经历了冷干–暖湿的气候变化;TS和TOC的变化反映了淡水–不稳定淡水、海水混合–稳定海水的沉积水体演替,与东海陆架一致。晚更新世期间,杭州湾地区发育的河床相、河漫滩相沉积物源区主要来自钱塘江流域,显示长英质火成岩的特征;全新世以来的古河口湾相、浅海相和现代河口湾相沉积物为钱塘江型碎屑与长江型碎屑的混合,显示中基性火成岩的特征,湾口受到长江物质的影响更强。以长江和钱塘江流域(Gd/Yb)_(UCC)为端元的模拟结果显示,杭州湾湾口与湾顶受到长江物质影响差异较大,古河口湾相时期,长江供给杭州湾湾口沉积物约78%,湾顶约39%;浅海相时期,长江供给杭州湾地区超过80%的碎屑,湾口、湾顶无明显差别;现代河口湾相时期,长江供给湾口沉积物约76%,湾顶约22%。该模拟方法在长江向杭州湾输送的碎屑分析中具有定量化的作用,并有望适用于其他沿海陆架河流系统。
基金Supported by the China Institute of Water Resources and Hydropower Research(No.K20231586)the Water Conservancy Bureau of Yunyang County(No.YYX24C00008)+1 种基金the Ecological Forestry Development Center of Lishui City(No.2021ZDZX03)the Asia-Pacific Network for Global Change Research(No.CRRP2020-06MY-Loh)。
文摘A sediment core(YJK19-02)collected from the southern outlet of Hangzhou Bay near the Yongjiang River estuary in East China was analyzed for grain size,lignin,bulk elemental composition,stable carbon isotope,and rare earth elements(REEs)to determine the sources and diagenesis of sedimentary organic matter(OM)of the estuary and adjacent areas since the Late Pleistocene.δ^(13)C values(-24.80‰–-23.60‰),total organic carbon/total nitrogen(TOC/TN)molar ratios(8.00–12.14),and light rare earth element/heavy rare earth element ratios(LREE/HREE=8.34–8.91)revealed the predominance of terrestrial sources of OM,mainly from the Changjiang(Yangtze)River.The lignin parameters of syringyl/vanillyl(S/V=0.20–0.73)and cinnamyl/vanillyl(C/V=0.03–0.19)ratios indicate the predominance of nonwoody angiosperms,and the vanillic acid/vanillin ratios[(Ad/Al)_(V)=0.32–1.57]indicate medium to high degrees of lignin degradation.An increasing trend ofΛ(total lignin in mg/100-mg OC)values from ca.14500 a BP to ca.11000 a BP reflected the increase in temperature during the Late Pleistocene.However,a time lag effect of temperature on vegetation abundance was also revealed.The relatively higher and stableΛvalues correspond to the higher temperature during the mid-Holocene from ca.8500 a BP to ca.4500 a BP.Λvalues decreased from ca.4000 a BP to the present,corresponding to historical temperature fluctuations during this time.Our results show that the vegetation abundance in the Yongjiang River Basin since the Late Pleistocene was related to the temperature fluctuation duo to climate change.
文摘亚洲内陆荒漠化和干旱化与中国西部人类生存环境和社会可持续发展密切相关。中国西部地区的气候自晚更新世以来经历了多次冷暖、干湿变化,研究其晚更新世古气候变化,有助于预测未来气候的变化趋势。文章分析了宁夏南部清水河盆地晚更新世中晚期的孢粉记录,结果显示孢粉序列可从下至上划分为4个组合带,反映了该地区晚更新世中晚期植被和气候变化规律。研究表明研究区晚更新世中期(75~50 ka B.P.)是植被以蒿属为主的干草原,气候温凉偏干;晚更新世晚期(25~15 ka B.P.)由荒漠草原-干草原和疏林草原交替出现逐渐过渡到荒漠草原,该时期冬季风呈现逐渐增强的趋势,致使气候逐渐变冷变干,气候类型由温凉偏湿过渡到冷干。宁夏南部清水河盆地晚更新世中晚期孢粉记录的深入研究对于正确认识黄土高原自然环境历史演变和黄土高原治理决策的制定具有重要指导意义。
