【研究目的】越来越多的高分辨率古气候记录证实全新世存在一系列数十年至百年尺度的快速波动,而这种突然的气候变化与人类社会经济发展有着非常密切的关系。4.2 ka BP气候突变事件在亚洲、非洲、北美洲以及地中海和南欧等地均有记录,...【研究目的】越来越多的高分辨率古气候记录证实全新世存在一系列数十年至百年尺度的快速波动,而这种突然的气候变化与人类社会经济发展有着非常密切的关系。4.2 ka BP气候突变事件在亚洲、非洲、北美洲以及地中海和南欧等地均有记录,表明了它的全球性特征。但在海陆交互的海岸带、特别是中国北方泥质海岸带地区,该事件的记录迄今未得到充分证实。【研究方法】本文以渤海湾西北岸相距1~6 km的岭头、罾口河及俵口南部3处埋藏牡蛎礁体及其上覆泥层为研究对象,通过硅藻分析(83个样品)、加速器^(14)C测年(32个数据)与沉积学研究,重建了礁体及上覆泥层所记录的古环境信息,同时探索了可能存在的“4.2 ka BP事件”在海岸带的印记。【研究结果】全新世以来,研究区依次经历了早全新世潮上带盐沼至潮间带→中全新世潮下带—潮间带中下部—潮间带中上部→晚全新世沼泽-盐沼低地沉积环境演变的海进-海退.过程。在约7 ka cal BP以来,3处礁体先后出现,气候温暖。随着礁体的向上建造,海水影响减弱,在5~4.3 ka cal BP时,3处礁体进入潮间带中下部,气候相对寒冷,致使3处礁体同时在4.2~4 ka cal BP时停止建礁,随即被上覆泥层覆盖。【研究结论】研究区在5~4 ka cal BP发生了一次气候波动过程:5~4.3 ka cal BP期间相对寒冷,4.3 ka cal BP后逐渐转暖,气候变化事件的转折点发生于约4.3 ka cal BP。这一明显的环境变化是中国北方泥质海岸带地区对“4.2 ka BP事件”的响应。展开更多
相距3-20km的岭头、罾口河、俵口和空港物流中心4 处埋藏牡蛎礁体的年代学研究证实,开始发育的时间不同,但同时在4.2-4.0kacalBP时结束建礁,即其灭亡与“4.2ka事件”在时间上重合.岭头、罾口河剖面〇稳定同位素和罾口河剖面孢粉数据进...相距3-20km的岭头、罾口河、俵口和空港物流中心4 处埋藏牡蛎礁体的年代学研究证实,开始发育的时间不同,但同时在4.2-4.0kacalBP时结束建礁,即其灭亡与“4.2ka事件”在时间上重合.岭头、罾口河剖面〇稳定同位素和罾口河剖面孢粉数据进一步表明,4.5-4.3ka cal BP时研究区气候出现变冷变干的趋势,4.3-4.2ka cal BP逐渐好转,推测这一气候波动变化过程可能是对“4.2ka事件”的响应.展开更多
Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L12 phase was studied during the phase transformation of Ni75Al...Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L12 phase was studied during the phase transformation of Ni75Al4.2V20.8. The results demonstrate that the growth of L12 phase can be divided into two stages： at the early stage, the composition of alloying elements in DO22 phase almost remains unchanged; at the late stage, the compositions of Ni and Al decrease while V increases in DO22 phase. Part of alloying elements for L12 phase growth are supplied from the site occupation evolution of alloying elements on three kinds of sublattices in DO22 phase. Ni is mainly supplied from V sublattice, and part of Al is supplied from NiⅠ and V sites at the centre of DO22 phase. The excessive V from the decreasing DO22 phase migrates into the centre of DO22 phase and mainly occupies V and NiII sites. It is the site occupation evolution of antisite atoms and ternary additions in DO22 phase that controls the growth rate of L12 phase at the late stage.展开更多
文摘【研究目的】越来越多的高分辨率古气候记录证实全新世存在一系列数十年至百年尺度的快速波动,而这种突然的气候变化与人类社会经济发展有着非常密切的关系。4.2 ka BP气候突变事件在亚洲、非洲、北美洲以及地中海和南欧等地均有记录,表明了它的全球性特征。但在海陆交互的海岸带、特别是中国北方泥质海岸带地区,该事件的记录迄今未得到充分证实。【研究方法】本文以渤海湾西北岸相距1~6 km的岭头、罾口河及俵口南部3处埋藏牡蛎礁体及其上覆泥层为研究对象,通过硅藻分析(83个样品)、加速器^(14)C测年(32个数据)与沉积学研究,重建了礁体及上覆泥层所记录的古环境信息,同时探索了可能存在的“4.2 ka BP事件”在海岸带的印记。【研究结果】全新世以来,研究区依次经历了早全新世潮上带盐沼至潮间带→中全新世潮下带—潮间带中下部—潮间带中上部→晚全新世沼泽-盐沼低地沉积环境演变的海进-海退.过程。在约7 ka cal BP以来,3处礁体先后出现,气候温暖。随着礁体的向上建造,海水影响减弱,在5~4.3 ka cal BP时,3处礁体进入潮间带中下部,气候相对寒冷,致使3处礁体同时在4.2~4 ka cal BP时停止建礁,随即被上覆泥层覆盖。【研究结论】研究区在5~4 ka cal BP发生了一次气候波动过程:5~4.3 ka cal BP期间相对寒冷,4.3 ka cal BP后逐渐转暖,气候变化事件的转折点发生于约4.3 ka cal BP。这一明显的环境变化是中国北方泥质海岸带地区对“4.2 ka BP事件”的响应。
文摘相距3-20km的岭头、罾口河、俵口和空港物流中心4 处埋藏牡蛎礁体的年代学研究证实,开始发育的时间不同,但同时在4.2-4.0kacalBP时结束建礁,即其灭亡与“4.2ka事件”在时间上重合.岭头、罾口河剖面〇稳定同位素和罾口河剖面孢粉数据进一步表明,4.5-4.3ka cal BP时研究区气候出现变冷变干的趋势,4.3-4.2ka cal BP逐渐好转,推测这一气候波动变化过程可能是对“4.2ka事件”的响应.
基金Projects(51174168,51274167)supported by the National Natural Science Foundation of ChinaProject(2013M532082)supported by Postdoctoral Science Foundation of ChinaProjects(13R21421700,13R21421800)supported by the Postdoctoral Science Foundation of Shanghai,China
文摘Based on the microscopic phase-field model, the correlation between site occupation evolution of alloying elements in Ni3V-DO22 phase and growth of Ni3Al-L12 phase was studied during the phase transformation of Ni75Al4.2V20.8. The results demonstrate that the growth of L12 phase can be divided into two stages： at the early stage, the composition of alloying elements in DO22 phase almost remains unchanged; at the late stage, the compositions of Ni and Al decrease while V increases in DO22 phase. Part of alloying elements for L12 phase growth are supplied from the site occupation evolution of alloying elements on three kinds of sublattices in DO22 phase. Ni is mainly supplied from V sublattice, and part of Al is supplied from NiⅠ and V sites at the centre of DO22 phase. The excessive V from the decreasing DO22 phase migrates into the centre of DO22 phase and mainly occupies V and NiII sites. It is the site occupation evolution of antisite atoms and ternary additions in DO22 phase that controls the growth rate of L12 phase at the late stage.
