Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sh...Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30–40 ka BP spanned a period in the late Marine Isotope Stage 3（MIS 3） and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level（H_S） was defined as the glaciation-climateforced sea levels, and the relative sea level change（H_R） was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago,whereas the simulated relative sea-levels turned out to be –26.3––29.9 m a.s.l. The small error involved in the simulation results of ±（2.5–4.5） m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between –19.2––22.1m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.展开更多
全新世人类活动逐渐增强,其对自然植被的干扰和改造也逐渐加深,在部分地区已然成为引起植被变化不可忽视的因素之一。考古结果证实,浙江地区在过去10 ka存在连续的文化序列,但全新世人类活动对区域植被的影响程度和范围尚不明确。本文...全新世人类活动逐渐增强,其对自然植被的干扰和改造也逐渐加深,在部分地区已然成为引起植被变化不可忽视的因素之一。考古结果证实,浙江地区在过去10 ka存在连续的文化序列,但全新世人类活动对区域植被的影响程度和范围尚不明确。本文收集、整理了浙江地区共40个样点的全新世孢粉记录,按照有无史前文化的发生将其分为遗址、遗址周边和自然3类数据,利用RRatepol程序包计算了各个样点的植被变化速率(RoC),同时使用孢粉生物群区化方法(Biomisation)重建了古植被变化过程。结果显示,在文化遗址,全新世RoC变化幅度较大且波动频繁,9.0—3.0 cal ka BP期间整体呈增加趋势;遗址周边的RoC变化幅度介于遗址和自然点位之间,在3.0 cal ka BP之后呈现迅速增加;自然点的RoC变幅最小且较为稳定,在2.0 cal ka BP后才出现明显升高。全新世期间人类活动引起的局部植被变化速率可能是自然植被变化的2~3倍,并且在3.0 cal ka BP后,人类活动对浙江古植被影响的空间范围开始明显扩张。人类活动导致的植被变化与自然植被变化存在一定的背离,新石器时代毁林开荒和种植农业的发展导致了浙江地区植被景观的破碎化。遗址点的生物群区停留时间明显低于遗址周边及自然点,说明全新世人类活动加速了区域植被成分变化的同时,也导致植被生态系统的弹性和恢复力显著降低。在浙江地区以孢粉进行的气候重建以及自然保护地体系建设实践中面临的植被保护和恢复问题,必须考虑长期的人类干扰历史以及植被变化历史格局的潜在影响。展开更多
基金the National Basic Research Program of China under contract Nos 2013CB956501 and 2012CB956103
文摘Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30–40 ka BP spanned a period in the late Marine Isotope Stage 3（MIS 3） and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level（H_S） was defined as the glaciation-climateforced sea levels, and the relative sea level change（H_R） was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago,whereas the simulated relative sea-levels turned out to be –26.3––29.9 m a.s.l. The small error involved in the simulation results of ±（2.5–4.5） m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between –19.2––22.1m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.
文摘全新世人类活动逐渐增强,其对自然植被的干扰和改造也逐渐加深,在部分地区已然成为引起植被变化不可忽视的因素之一。考古结果证实,浙江地区在过去10 ka存在连续的文化序列,但全新世人类活动对区域植被的影响程度和范围尚不明确。本文收集、整理了浙江地区共40个样点的全新世孢粉记录,按照有无史前文化的发生将其分为遗址、遗址周边和自然3类数据,利用RRatepol程序包计算了各个样点的植被变化速率(RoC),同时使用孢粉生物群区化方法(Biomisation)重建了古植被变化过程。结果显示,在文化遗址,全新世RoC变化幅度较大且波动频繁,9.0—3.0 cal ka BP期间整体呈增加趋势;遗址周边的RoC变化幅度介于遗址和自然点位之间,在3.0 cal ka BP之后呈现迅速增加;自然点的RoC变幅最小且较为稳定,在2.0 cal ka BP后才出现明显升高。全新世期间人类活动引起的局部植被变化速率可能是自然植被变化的2~3倍,并且在3.0 cal ka BP后,人类活动对浙江古植被影响的空间范围开始明显扩张。人类活动导致的植被变化与自然植被变化存在一定的背离,新石器时代毁林开荒和种植农业的发展导致了浙江地区植被景观的破碎化。遗址点的生物群区停留时间明显低于遗址周边及自然点,说明全新世人类活动加速了区域植被成分变化的同时,也导致植被生态系统的弹性和恢复力显著降低。在浙江地区以孢粉进行的气候重建以及自然保护地体系建设实践中面临的植被保护和恢复问题,必须考虑长期的人类干扰历史以及植被变化历史格局的潜在影响。
