The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, howe...The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Nino-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Nina-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Nino-or La Nina-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability.展开更多
The article describes a possible impact of demographic explosion during the Neolith on local ecosystems and on the global climate as well as the role of this explosion in aggravating the course of 4.2 ka cooling event...The article describes a possible impact of demographic explosion during the Neolith on local ecosystems and on the global climate as well as the role of this explosion in aggravating the course of 4.2 ka cooling event. A possible role of human activity in changing the pattern of mid-latitudes westerlies, monsoons and Walker circulation throughout the Holocene is analyzed. It is explained why during the Holocene Climatic Optimum (HCO) monsoons could have been weaker than today, not stronger, as it is commonly stated. It is described how during the HCO the humid Tibetan Plateau could have repelled the Indian monsoon to the west and the East Asian monsoon to the north. The explanation for weaker El Niño-Southern Oscillation (ENSO) during HCO is proposed.展开更多
统计了全新世早期气候突变事件'8.2 ka BP冷事件', 并对其触发机制及区域气候响应做了较深入的分析. 从各种气候记录的分布情况来看, 全新世早期的这次冷事件是全球性气候事件, 并非是一种局部气候变冷事件. 全新世早期Agassiz...统计了全新世早期气候突变事件'8.2 ka BP冷事件', 并对其触发机制及区域气候响应做了较深入的分析. 从各种气候记录的分布情况来看, 全新世早期的这次冷事件是全球性气候事件, 并非是一种局部气候变冷事件. 全新世早期Agassiz和Ojibway阻塞湖在大约8.47 cal ka BP时突然排泄, 可能是造成8.4～8.0 cal ka BP时期北大西洋地区突然降温的主要原因;另外, 8.4～8.0 cal ka BP期间的太阳辐射量减小或太阳活动减弱, 也可能对全新世早期的这次冷事件有一定强化作用. 由于西风带南移和季风环流减弱等原因的影响, 使得这次冷事件区域气候响应有明显的不同, 欧洲的中高纬度地区、东亚地区呈现一种冷干的气候状态;北美洲三分之二的地区降水量减少、风力加强;中美洲、非洲的大部分地区和阿拉伯半岛均以干旱为主;东欧、地中海地区呈现普遍的冷湿气候环境, 亚马逊盆地、智利玻利维亚高原呈现低湿的气候状况.展开更多
5.0 ka BP前后全球普遍经历了一次快速的降温事件,对世界范围内很多地区的环境产生了显著影响。本文利用公开发表的有高精度年代控制的、高分辨率石笋和湖沼沉积记录,系统回顾了5 ka BP气候事件在我国不同地区的降雨表现。这次气候事件...5.0 ka BP前后全球普遍经历了一次快速的降温事件,对世界范围内很多地区的环境产生了显著影响。本文利用公开发表的有高精度年代控制的、高分辨率石笋和湖沼沉积记录,系统回顾了5 ka BP气候事件在我国不同地区的降雨表现。这次气候事件在我国季风区不同区域都有记录,其中在季风区北方和青藏高原地区记录的最为清楚,体现为显著的干旱。事件起始于5.6—5.5 ka BP,在5.0 ka BP左右达到峰值,其后快速回升。5 ka BP气候事件对我国新石器文化的发展产生了重要影响。太阳辐射减少导致的赤道辐合带南移和大西洋经向翻转环流减弱导致的亚洲夏季风减弱可能驱动了此次气候事件。然而,不同地区、特别是南方地区的不同记录在此次事件的表现形式和开始时间有所差异。云南和湖北的泥炭记录显示此次事件为突变事件,发生于4.7—4.9 ka BP,不同于其他地质记录的渐变状态。未来还需加强在南方地区,特别是华东地区重建涵盖5 ka BP气候事件的有绝对定年的高分辨率可靠降雨记录。进一步厘清这些记录的差异是由于不同气候代用指标和记录分辨率的不同以及测年误差导致的,还是对气候事件的响应存在着区域差异。展开更多
在4.2 ka BP气候突变事件的影响下,世界主要文明和中国境内大部分新石器时代文化出现断层或崩溃,但中国中原地区的洛阳盆地却支持了河南龙山文化向二里头文化的传承和成功转型,使中国文明得以一脉相承.为探究洛阳盆地这一时期的环境状...在4.2 ka BP气候突变事件的影响下,世界主要文明和中国境内大部分新石器时代文化出现断层或崩溃,但中国中原地区的洛阳盆地却支持了河南龙山文化向二里头文化的传承和成功转型,使中国文明得以一脉相承.为探究洛阳盆地这一时期的环境状况和人类活动,在AMS^(14)C年代的支持下,基于HZ-1湿地剖面孢粉分析及磁化率和粒度等指标的分析,本文重建了洛阳盆地4990~3890 cal a BP期间自然环境(植被/水文)和人类活动强度的变化历史.自然环境重建结果显示,4990~4330 cal a BP期间气候较干,灰嘴湿地水较浅;4330~4155 cal a BP期间气候湿润,是灰嘴湿地存在的最盛阶段;4155~3995 cal a BP期间气候变干,灰嘴湿地快速萎缩;3995~3890 cal a BP期间气候短暂变湿后再次转干,发育了一层较薄的强风化层后被黄土覆盖.人类活动强度重建结果表明,4990~4330 cal a BP期间人类活动强度较弱;4330~4155 cal a BP期间人类活动强度有所增加;4155~3995 cal a BP期间人类活动强度明显增强;3995~3890 cal a BP期间人类活动强度再次减弱.用大尺度的视角审视灰嘴记录后,我们发现,在4400~3950 cal a BP时段的亚洲季风减弱期内,长江中下游地区与洛阳盆地所在的黄土高原南缘地区确实捕捉到4.2 ka BP气候突变的信号,但二者的干湿状况却出现了明显的差异,即长江中下游地区的弱东亚季风事件较早出现(4400~4100 cal a BP),而黄土高原南缘地区(包括洛阳盆地)的弱东亚季风事件较晚出现(4200~3950 cal a BP).导致这种差异的主要原因可能是,与ENSO由La Ni?a阶段转向El Ni?o阶段有关的赤道太平洋东西方向的热力梯度和西太平洋副热带高压耦合关系的变化.展开更多
The emergence of complex society is a milestone in the history of human society evolution. China is one of the few regions in the world where the earliest complex society appeared; however, its driving mechanisms rema...The emergence of complex society is a milestone in the history of human society evolution. China is one of the few regions in the world where the earliest complex society appeared; however, its driving mechanisms remain unresolved. On the base of available evidence from both archaeology and Holocene climate, in combination with agency theory, this study attempts to address the driving mechanisms for the simultaneous emergence of complex societies in multiple areas of China around 5.5 cal ka BP. It is hypothesized that three factors, including climate change, population growth, and circumscription, jointly act and cause regional population-resource imbalance and trigger inter-group conflicts and wars. Such competitions provide the opportunity for some power-pursuing agents to break the restriction of social leveling mechanism and to become the centralized decision-making leaders, which further lead to the emergence of incipient large-scale complex societies. Increase in extreme climate events during 6.0–5.0 cal ka BP cooling period causes frequent occurrence of resource stress and increase in the frequency of inter-group competitions, which creates conditions for the legitimation, institutionalization, and persistence of centralized leadership, and finally leads to the formation of persistent institutionalized inequity. Our research result can explain not only the process and mechanism of complex society formation, but also two phenomena which cannot be reasonably explained by previous theories, that are, why the earliest complex societies in China emerge around 5.5 cal ka BP, and why they appear simultaneously in multiple regions.展开更多
发生在大约4200年前的一场持续干旱可能是当时史前文明快速衰落的重要推手,这在全球许多区域均有记录,但在中国西北干旱区是否存在该事件依然缺乏有力证据。本文通过分析托勒库勒湖沉积地层的孢粉,发现新疆地区也存在类似4.2 ka BP气候...发生在大约4200年前的一场持续干旱可能是当时史前文明快速衰落的重要推手,这在全球许多区域均有记录,但在中国西北干旱区是否存在该事件依然缺乏有力证据。本文通过分析托勒库勒湖沉积地层的孢粉,发现新疆地区也存在类似4.2 ka BP气候事件的记录。4.5—3.8 cal ka BP期间的孢粉谱与前后时段相比有显著差异,禾本科和蒿属花粉含量快速降低、藜科急剧增加、A/C值降低;区域环境短期内变得极为寒冷-干旱,先前的草原/荒漠草原演化为荒漠。对比也发现,尽管这一事件在不同研究点的开始和结束时间略有差异,但变化特征具有较好的一致性。目前,关于这次事件的驱动机制仍不清楚,还需在新疆及其他敏感区域开展更多古气候研究。展开更多
利用湖北神农架利川市玉龙洞一支长约400 mm的石笋(TCL),结合稳定同位素、 微量元素以及灰度等多指标重建了14.4 ka B.P.~2012 A.D.时段十年际分辨率的东亚地区气候与环境变化.该时段内,δ^18O变化范围为-9.5‰^-6.6‰,平均值为-8.48‰...利用湖北神农架利川市玉龙洞一支长约400 mm的石笋(TCL),结合稳定同位素、 微量元素以及灰度等多指标重建了14.4 ka B.P.~2012 A.D.时段十年际分辨率的东亚地区气候与环境变化.该时段内,δ^18O变化范围为-9.5‰^-6.6‰,平均值为-8.48‰.该记录与亚洲季风区同时段其他石笋记录重现性良好,说明石笋δ^18O可以较好地反映轨道至千年尺度的亚洲夏季风强度变化.结合其δ^13C、 微量元素以及灰度重建了多指标气候变化.石笋δ^13C变化范围是-8.2‰^-3.8‰,围绕均值-5.4‰上下波动,主要存在千年尺度振荡,反映了洞穴上覆植被覆盖率和土壤CO2产率的变化.石笋TCL的灰度值、Sr/Ca和Ba/Ca比值与δ^13C值在千年尺度波动上对应关系良好,间接指示了与当地水热条件相关的洞穴水文状况变化.石笋灰度与δ^13C值对应关系良好,间接指示了干湿度或降雨量的变化.石笋中Sr/Ca和Ba/Ca变化的总体趋势基本一致,主要受当地降水量控制下土壤淋滤作用变化的影响.TCLδ^18O序列显示"4.2 ka事件"的起止时间段为4.4~4.1 ka B.P.,整体呈现"缓慢开始,快速结束"的结构特征.此时段其δ^13C值偏正,灰度以及微量元素代用指标趋势均呈现低值,这种不同指标间出现的协同变化,说明当时利川地区降水量减少,局域环境明显偏向干冷.文章推测此次干旱事件的发生是由于大量淡水注入北大西洋,海表温降低,使得赤道辐合带(ITCZ)南移,进而引起北半球中低纬度季风减弱并得以在石笋多指标记录中反映.展开更多
文章选择沙漠/黄土过渡带的榆林市白河庙村钻孔（38°35＇9.89″N，109°24＇0.71″E）泥炭沉积，通过建立良好的年代序列和高分辨率花粉记录分析，重建研究区内植被演替和气候环境变化过程。在此基础上，结合考古学资料，探讨...文章选择沙漠/黄土过渡带的榆林市白河庙村钻孔（38°35＇9.89″N，109°24＇0.71″E）泥炭沉积，通过建立良好的年代序列和高分辨率花粉记录分析，重建研究区内植被演替和气候环境变化过程。在此基础上，结合考古学资料，探讨适宜的气候环境阶段和极端气候事件对人类活动的影响。结果表明，6 ka B.P.以来研究区植被类型经历典型草原、荒漠草原、干草原、荒漠草原4个阶段，指示6.0～4.2 ka B.P.气候较为暖湿，为全新世适宜期；4.2 ka B.P.时发生极端干旱事件，之后（4.2～1.1 ka B.P.）气候向干旱化发展；1.1～0.5 ka B.P.，气候经历短暂的湿润期；0.5 ka B.P.之后，气候再次转干。另外，通过统计沙漠/黄土过渡带6～3 ka B.P.考古遗址数量及其空间分布变化信息，发现史前人类活动与气候、生态系统变化紧密相关。东亚夏季风带来的降水量控制干旱/半干旱地区水资源变化，从而影响依赖水资源的旱作农业发展、人类活动强弱和考古学文化兴衰。6.0～4.2 ka B.P.降水较多，植被盖度高，毛乌素沙地固定，沙漠/黄土过渡带发育古土壤，并向西北移动。适宜的气候环境和良好的生态条件有利于旱作农业生产，导致人口增加，遗址点数量增多，人类活动范围扩大，仰韶时期和龙山时期的考古学文化繁荣发展。而4.2～3.0 ka B.P.遗址点大幅减少，人类活动规模减小，考古学文化衰退。4.2 ka B.P.极端干旱事件及之后持续的干旱，导致植被退化，毛乌素沙地沙丘活化，沙漠/黄土过渡带向东南方向摆动。水资源短缺和生态环境破坏，对以粟为主的旱作农业生产和人类生存造成严重影响，可能是导致该地区史前考古学文化大范围衰退的重要原因。展开更多
基金The National Natural Science Foundation of China under contract No.91428203the Guangxi Scientific Projects under contract Nos AD17129063 and AA17204074the Bagui Fellowship from Guangxi of China
文摘The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Nino-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Nina-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Nino-or La Nina-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability.
文摘The article describes a possible impact of demographic explosion during the Neolith on local ecosystems and on the global climate as well as the role of this explosion in aggravating the course of 4.2 ka cooling event. A possible role of human activity in changing the pattern of mid-latitudes westerlies, monsoons and Walker circulation throughout the Holocene is analyzed. It is explained why during the Holocene Climatic Optimum (HCO) monsoons could have been weaker than today, not stronger, as it is commonly stated. It is described how during the HCO the humid Tibetan Plateau could have repelled the Indian monsoon to the west and the East Asian monsoon to the north. The explanation for weaker El Niño-Southern Oscillation (ENSO) during HCO is proposed.
文摘统计了全新世早期气候突变事件'8.2 ka BP冷事件', 并对其触发机制及区域气候响应做了较深入的分析. 从各种气候记录的分布情况来看, 全新世早期的这次冷事件是全球性气候事件, 并非是一种局部气候变冷事件. 全新世早期Agassiz和Ojibway阻塞湖在大约8.47 cal ka BP时突然排泄, 可能是造成8.4～8.0 cal ka BP时期北大西洋地区突然降温的主要原因;另外, 8.4～8.0 cal ka BP期间的太阳辐射量减小或太阳活动减弱, 也可能对全新世早期的这次冷事件有一定强化作用. 由于西风带南移和季风环流减弱等原因的影响, 使得这次冷事件区域气候响应有明显的不同, 欧洲的中高纬度地区、东亚地区呈现一种冷干的气候状态;北美洲三分之二的地区降水量减少、风力加强;中美洲、非洲的大部分地区和阿拉伯半岛均以干旱为主;东欧、地中海地区呈现普遍的冷湿气候环境, 亚马逊盆地、智利玻利维亚高原呈现低湿的气候状况.
文摘5.0 ka BP前后全球普遍经历了一次快速的降温事件,对世界范围内很多地区的环境产生了显著影响。本文利用公开发表的有高精度年代控制的、高分辨率石笋和湖沼沉积记录,系统回顾了5 ka BP气候事件在我国不同地区的降雨表现。这次气候事件在我国季风区不同区域都有记录,其中在季风区北方和青藏高原地区记录的最为清楚,体现为显著的干旱。事件起始于5.6—5.5 ka BP,在5.0 ka BP左右达到峰值,其后快速回升。5 ka BP气候事件对我国新石器文化的发展产生了重要影响。太阳辐射减少导致的赤道辐合带南移和大西洋经向翻转环流减弱导致的亚洲夏季风减弱可能驱动了此次气候事件。然而,不同地区、特别是南方地区的不同记录在此次事件的表现形式和开始时间有所差异。云南和湖北的泥炭记录显示此次事件为突变事件,发生于4.7—4.9 ka BP,不同于其他地质记录的渐变状态。未来还需加强在南方地区,特别是华东地区重建涵盖5 ka BP气候事件的有绝对定年的高分辨率可靠降雨记录。进一步厘清这些记录的差异是由于不同气候代用指标和记录分辨率的不同以及测年误差导致的,还是对气候事件的响应存在着区域差异。
文摘在4.2 ka BP气候突变事件的影响下,世界主要文明和中国境内大部分新石器时代文化出现断层或崩溃,但中国中原地区的洛阳盆地却支持了河南龙山文化向二里头文化的传承和成功转型,使中国文明得以一脉相承.为探究洛阳盆地这一时期的环境状况和人类活动,在AMS^(14)C年代的支持下,基于HZ-1湿地剖面孢粉分析及磁化率和粒度等指标的分析,本文重建了洛阳盆地4990~3890 cal a BP期间自然环境(植被/水文)和人类活动强度的变化历史.自然环境重建结果显示,4990~4330 cal a BP期间气候较干,灰嘴湿地水较浅;4330~4155 cal a BP期间气候湿润,是灰嘴湿地存在的最盛阶段;4155~3995 cal a BP期间气候变干,灰嘴湿地快速萎缩;3995~3890 cal a BP期间气候短暂变湿后再次转干,发育了一层较薄的强风化层后被黄土覆盖.人类活动强度重建结果表明,4990~4330 cal a BP期间人类活动强度较弱;4330~4155 cal a BP期间人类活动强度有所增加;4155~3995 cal a BP期间人类活动强度明显增强;3995~3890 cal a BP期间人类活动强度再次减弱.用大尺度的视角审视灰嘴记录后,我们发现,在4400~3950 cal a BP时段的亚洲季风减弱期内,长江中下游地区与洛阳盆地所在的黄土高原南缘地区确实捕捉到4.2 ka BP气候突变的信号,但二者的干湿状况却出现了明显的差异,即长江中下游地区的弱东亚季风事件较早出现(4400~4100 cal a BP),而黄土高原南缘地区(包括洛阳盆地)的弱东亚季风事件较晚出现(4200~3950 cal a BP).导致这种差异的主要原因可能是,与ENSO由La Ni?a阶段转向El Ni?o阶段有关的赤道太平洋东西方向的热力梯度和西太平洋副热带高压耦合关系的变化.
基金supported by the National Natural Science Foundation of China (Grant No. 41672176)the State Key Basic Research and Development Program (Grant No. 2015CB953802)
文摘The emergence of complex society is a milestone in the history of human society evolution. China is one of the few regions in the world where the earliest complex society appeared; however, its driving mechanisms remain unresolved. On the base of available evidence from both archaeology and Holocene climate, in combination with agency theory, this study attempts to address the driving mechanisms for the simultaneous emergence of complex societies in multiple areas of China around 5.5 cal ka BP. It is hypothesized that three factors, including climate change, population growth, and circumscription, jointly act and cause regional population-resource imbalance and trigger inter-group conflicts and wars. Such competitions provide the opportunity for some power-pursuing agents to break the restriction of social leveling mechanism and to become the centralized decision-making leaders, which further lead to the emergence of incipient large-scale complex societies. Increase in extreme climate events during 6.0–5.0 cal ka BP cooling period causes frequent occurrence of resource stress and increase in the frequency of inter-group competitions, which creates conditions for the legitimation, institutionalization, and persistence of centralized leadership, and finally leads to the formation of persistent institutionalized inequity. Our research result can explain not only the process and mechanism of complex society formation, but also two phenomena which cannot be reasonably explained by previous theories, that are, why the earliest complex societies in China emerge around 5.5 cal ka BP, and why they appear simultaneously in multiple regions.
文摘发生在大约4200年前的一场持续干旱可能是当时史前文明快速衰落的重要推手,这在全球许多区域均有记录,但在中国西北干旱区是否存在该事件依然缺乏有力证据。本文通过分析托勒库勒湖沉积地层的孢粉,发现新疆地区也存在类似4.2 ka BP气候事件的记录。4.5—3.8 cal ka BP期间的孢粉谱与前后时段相比有显著差异,禾本科和蒿属花粉含量快速降低、藜科急剧增加、A/C值降低;区域环境短期内变得极为寒冷-干旱,先前的草原/荒漠草原演化为荒漠。对比也发现,尽管这一事件在不同研究点的开始和结束时间略有差异,但变化特征具有较好的一致性。目前,关于这次事件的驱动机制仍不清楚,还需在新疆及其他敏感区域开展更多古气候研究。
文摘利用湖北神农架利川市玉龙洞一支长约400 mm的石笋(TCL),结合稳定同位素、 微量元素以及灰度等多指标重建了14.4 ka B.P.~2012 A.D.时段十年际分辨率的东亚地区气候与环境变化.该时段内,δ^18O变化范围为-9.5‰^-6.6‰,平均值为-8.48‰.该记录与亚洲季风区同时段其他石笋记录重现性良好,说明石笋δ^18O可以较好地反映轨道至千年尺度的亚洲夏季风强度变化.结合其δ^13C、 微量元素以及灰度重建了多指标气候变化.石笋δ^13C变化范围是-8.2‰^-3.8‰,围绕均值-5.4‰上下波动,主要存在千年尺度振荡,反映了洞穴上覆植被覆盖率和土壤CO2产率的变化.石笋TCL的灰度值、Sr/Ca和Ba/Ca比值与δ^13C值在千年尺度波动上对应关系良好,间接指示了与当地水热条件相关的洞穴水文状况变化.石笋灰度与δ^13C值对应关系良好,间接指示了干湿度或降雨量的变化.石笋中Sr/Ca和Ba/Ca变化的总体趋势基本一致,主要受当地降水量控制下土壤淋滤作用变化的影响.TCLδ^18O序列显示"4.2 ka事件"的起止时间段为4.4~4.1 ka B.P.,整体呈现"缓慢开始,快速结束"的结构特征.此时段其δ^13C值偏正,灰度以及微量元素代用指标趋势均呈现低值,这种不同指标间出现的协同变化,说明当时利川地区降水量减少,局域环境明显偏向干冷.文章推测此次干旱事件的发生是由于大量淡水注入北大西洋,海表温降低,使得赤道辐合带(ITCZ)南移,进而引起北半球中低纬度季风减弱并得以在石笋多指标记录中反映.
文摘文章选择沙漠/黄土过渡带的榆林市白河庙村钻孔（38°35＇9.89″N，109°24＇0.71″E）泥炭沉积，通过建立良好的年代序列和高分辨率花粉记录分析，重建研究区内植被演替和气候环境变化过程。在此基础上，结合考古学资料，探讨适宜的气候环境阶段和极端气候事件对人类活动的影响。结果表明，6 ka B.P.以来研究区植被类型经历典型草原、荒漠草原、干草原、荒漠草原4个阶段，指示6.0～4.2 ka B.P.气候较为暖湿，为全新世适宜期；4.2 ka B.P.时发生极端干旱事件，之后（4.2～1.1 ka B.P.）气候向干旱化发展；1.1～0.5 ka B.P.，气候经历短暂的湿润期；0.5 ka B.P.之后，气候再次转干。另外，通过统计沙漠/黄土过渡带6～3 ka B.P.考古遗址数量及其空间分布变化信息，发现史前人类活动与气候、生态系统变化紧密相关。东亚夏季风带来的降水量控制干旱/半干旱地区水资源变化，从而影响依赖水资源的旱作农业发展、人类活动强弱和考古学文化兴衰。6.0～4.2 ka B.P.降水较多，植被盖度高，毛乌素沙地固定，沙漠/黄土过渡带发育古土壤，并向西北移动。适宜的气候环境和良好的生态条件有利于旱作农业生产，导致人口增加，遗址点数量增多，人类活动范围扩大，仰韶时期和龙山时期的考古学文化繁荣发展。而4.2～3.0 ka B.P.遗址点大幅减少，人类活动规模减小，考古学文化衰退。4.2 ka B.P.极端干旱事件及之后持续的干旱，导致植被退化，毛乌素沙地沙丘活化，沙漠/黄土过渡带向东南方向摆动。水资源短缺和生态环境破坏，对以粟为主的旱作农业生产和人类生存造成严重影响，可能是导致该地区史前考古学文化大范围衰退的重要原因。
