共查询到19条相似文献，搜索用时 171 毫秒
1.
末次冰消期以来的气候突变事件的时空变化特征及其区域响应是古气候环境变化研究的重要内容,然而亚洲中部干旱区末次冰消期以来的气候突变记录较少,尤其缺少末次冰消期期间快速转暖过程的区域响应.本研究通过对位于亚洲中部干旱区的新疆西天山中部亚高山湖泊赛里木湖湖心采得的长300 cm的SLM2009钻孔沉积物的碳酸盐含量和粒度变化特征的分析,在 14 个 AMS 14C测年数据的基础上,探讨了末次冰消期约23. 4 cal. ka B. P.以来亚洲中部干旱区的气候突变事件记录及其区域响应过程.结果表明:赛里木湖湖心钻孔沉积物完整记录了 H1 ( 17. 5 ~ 15. 2 cal. ka B. P.)、 YD ( 12. 6 ~ 11. 7 cal. ka B. P.)冷事件以及 B-A ( 15. 2 ~12. 9 cal. ka B. P.)暖事件等末次冰消期气候突变事件以及全新世以来的10. 5 ka、 8. 2 ka、 5. 5 ka、 4. 2 ka、 2. 8 ka和小冰期冷事件,这与亚洲中部干旱区已有的气候突变事件记录相吻合,表明末次冰消期以来亚洲中部干旱区具有相似的气候突变演化模式.同时这些气候突变事件与高纬冰芯以及低纬石笋氧同位素记录的一致性则表明气候突变具有全球性影响,受相同的成因机制因素控制. 相似文献
2.
在末次冰消期总体持续增温的过程中,全球气候经历了一系列以"快速增温/降温"为主要特征的千-数十年尺度的突变事件.由于这些气候突变事件具有明显的高频特性,需要在全球范围不同地区开展更多高分辨率的古气候研究,用于进行突变事件的对比和机制的探讨.本研究对比滇西南腾冲青海湖、滇西北泸沽湖和高山湖泊天才湖约2万以来的孢粉、炭屑记录,揭示了中国滇西地区末次冰消期的植被演替与气候变化历史,探讨了末次冰消期存在的气候突变事件.结果表明,滇西地区末次冰消期开始转暖发生在约19 ka(1 ka=1000 cal. a B. P.);冰消期开始以后,滇西地区气候普遍依次在 17. 5±0. 5~15. 2±0. 1 ka期间、 15. 2±0. 1~14. 3±0. 1 ka期间、 14. 3± 0. 1~12. 9±0. 1 ka期间和12. 9±0. 1~11. 7±0. 2 ka期间存在冷干-逐渐变暖变湿-明显更暖湿-温度湿度略有下降等这几个突变事件,它们在时间上分别对应于H1冷事件、波令前增暖期、 B/A暖期和YD冷事件;滇西地区比较一致地在 11. 7±0. 2 ka进入全新世.除此之外,滇西北地区在约17. 7~17. 0 ka期间可能还存在一次短暂的较明显的暖湿期.对末次冰消期气候变化机制的探讨认为,末次冰消期开始转暖及以后逐渐增温的趋势主要受夏季太阳辐射量从约20 ka逐渐增加,到11 ka左右达到峰值的控制;而末次冰消期发生的气候突变事件如H1冷事件、波令前增暖期、 B/A暖期和YD冷事件主要是受大西洋温盐环流的影响,同时温室气体浓度的变化也起了重要的调制作用. 相似文献
3.
对中国东北地区科尔沁沙地13个风成沙剖面和3个黄土剖面进行了研究,测试分析了黑色砂质土壤和下伏古风成沙的OSL年龄及粒度、磁化率、色度数据;OSL测年获得的古风成沙数据位于末次冰期晚期-全新世期间(13 ～1Oka),小于26.5 ～19.Oka的末次冰盛期时段.末次冰盛期干冷气候背景下沙丘持续不断的活化翻动,风成沙在进入全新世气候转暖后才被固定,沙地内全新世黑色砂质土壤下伏的疏松流沙为末次冰盛期产物,其分布范围可代表末次冰盛期流动沙丘的分布范围.现今科尔沁沙地面积约为42000km2,活动沙丘面积约占10％.在末次冰盛期不仅原固定沙丘活化,沙质平原与部分甸子也被流沙覆盖,面积约85000km2,活动沙丘或流沙面积相对目前扩大了约20倍.末次冰盛期沙地活化扩张的控制因素主要有两方面:一方面冰期气候干旱寒冷,降水减少,地表植被覆盖下降,地表松散沉积物遭受风力剥蚀而活化成流沙;另一方面科尔沁沙地内部水系发育,河流流经途中会沉积大量松散物质.在冰期干冷环境下,河流水位下降,河流沙暴露并遭受风蚀改造,为流沙扩张提供物源,沙漠沿西拉木伦河流域扩展. 相似文献
4.
通过对云南泸沽湖高分辨率沉积指标序列(硅藻、枝角类和孢粉)的对比分析,初步揭示了水生生物(硅藻、枝角类和水生孢粉)对末次冰盛期期间气候变化的快速响应过程.结果表明,硅藻群落组成首先响应末次冰盛期时期的开始变冷,枝角类滞后,水生孢粉则表现为渐进的响应过程.然而,泸沽湖沉积硅藻记录对末次冰期以来的短时间尺度气候快速变化的Heinrich和新仙女木事件并未有响应,揭示气候事件判别的准确性取决于指标直接响应气候的特征以及多指标的综合对比.综合西南季风区云南不同海拔湖泊沉积记录(硅藻、孢粉、摇蚊等)获得的2万年以来数据及序列表明,末次冰期千年尺度的气候突变事件( Heinrich 1、 B?lling/Aller?d暖期和新仙女木YD冷事件)在整个西南季风系统中都有反映,且气候事件变化区间及幅度存在区域差异,其根本原因是受不同气候系统、复杂地形(青藏高原)的制约. 相似文献
5.
通过对内蒙古东部现代东亚季风界线两侧的浑善达克沙地和呼伦贝尔沙地风成砂-古土壤剖面的光释光、~(14)C年代和沉积物主、微量元素地球化学的分析,重建内蒙古东部末次冰消期以来气候变迁过程。浑善达克沙地的浩来呼热剖面(hsh1-09)显示了末次冰消期以来3次暖湿气候期,分别对应末次冰消期、全新世大暖期、中世纪暖期。呼伦贝尔沙地的嵯岗剖面(CG-09)表现了全新世大暖期和中世纪暖期两次的暖湿气候期。这一过程是对东亚夏季风的响应,大致反映了内蒙古东部末次冰消期以来的东亚夏季风两次不同程度增强及大暖期结束的南退过程。通过对比前人研究结果,全新世中期东亚夏季风较强,在内蒙古东部大约距今4 ka开始减弱、南退;中世纪暖期夏季风强度较弱,持续时间短。 相似文献
6.
解读末次冰消期全球水文气候演变过程对于理解气候系统对内外强迫的响应具有重要意义. 以冲绳海槽中部OKI02岩心为材料,通过浮游有孔虫Globigerinodes ruber和Pulleniatina obliquiloculata壳体Mg/Ca比值分别重建了19 ka BP以来海槽中部表层和温跃层海水温度（SST和TWT）,结合浮游有孔虫群落组成变化重点恢复了末次冰消期（~18~11.7 ka BP）上层水体温度变化的特征和过程. 结果显示SST在LGM显著偏低,末次冰消期表现为显著的千年尺度变化,清楚地记录了HS1、B/A、YD等快速气候波动事件. 19 ka BP以来重建的TWT整体呈明显的上升趋势,但波动频繁而剧烈,末次冰消期相对较低,未显示显著的千年尺度变化. 对比北半球高纬和热带太平洋的记录发现,末次冰消期冲绳海槽中部SST开始上升的时间基本与前者相当,但明显滞后于热带西太平洋;冰消期其变化模式明显区别于热带西太平洋持续稳定的升温过程,而更类似于北半球高纬区的变化. 与SST明显不同,海槽区温跃层的升温（~18 ka BP）明显早于北半球高纬变暖,却接近于热带西太平洋海表温度开始上升的时间;且TWT的上升和波动方式也更接近于热带太平洋海温的变化模式. 对末次冰消期SST和TWT差异化演变的分析表明,AMOC对中低纬大气环流的影响可能通过东亚冬季风强度的变化控制了海槽区SST的演变,而热带太平洋ENSO过程则可能通过黑潮强度的变化决定了区域TWT的演化. 末次冰消期冲绳海槽中部SST和TWT演化存在明显的脱耦现象,显示了其与高、低纬海洋和气候变化之间的密切联系. 相似文献
7.
麻城剖面位于江汉平原东北缘山地丘陵与平原过渡带半封闭的宽浅碟形洼地,是江汉平原北缘末次冰消期代表性沉积剖面。沉积环境主要由山麓坡洪积相和沼泽相组成,形成年代为距今18.00~8.60 ka。麻城剖面粒度组成主要以粉砂为主,达60.73%,其中,粗粉砂达40.83%。剖面粒度变化可划分为7个变化阶段。结合剖面的岩性与沉积环境特征等综合分析,发现末次冰消期气候环境经历了四个气候期:第一气候期17.90~17.02 ka B.P.,为冰盛期之后气候开始回暖升温期。此时降水相对较多,地表径流强度中等偏强。第二个时期17.02~12.02 ka B.P.,为快速升温期。总体暖湿多雨,是末次冰消期最显著暖湿期,在江汉平原北缘坡麓地带的洼地广泛发育了沼泽。粒度变化进一步表明气候存在波动,早、晚期降雨强度大,时有强降水发生,地表径流稳定性差;中期（14.47~12.64 ka B.P.）降水明显减少,但雨量相对均匀,地表径流变幅小,此与长江中下游地区石笋记录的冰消期气候特征是一致的。第三气候期12.02~10.80 ka B.P.,该期是新仙女木事件之后的快速升温期,平均粒径和分选系数为剖面最大。表明当时降雨量大,气候稳定性较差,强降雨时有发生。第四气候期10.80~8.60 ka B.P.,气候总体为偏温湿环境。地表径流较第三气候期明显降低,早期降水偏多,后期温湿程度降低,地表径流变小。剖面中有两个明显的气候事件记录,一是新仙女木事件,表现为第④层与第⑤层之间的短暂沉积间断和沼泽环境的结束;二是9.8~9.2 ka B.P.干旱期,为厚约15 cm的黄土状土的沉积。研究表明,长江和汉江洪泛影响不到的江汉平原边缘洼地沉积可能是记录本地区气候特征的良好载体。 相似文献
8.
冲绳海槽的晚第四纪浊流沉积 总被引：1，自引：0，他引：1
张明书 《吉林大学学报(地球科学版)》1988,(1)
冲绳海槽晚第四纪的浊流沉积发育在海底斜坡带和坡折处静水环境,属阵发性纵向浊流。物质来源于海槽中心斜坡区的滑塌沉积物、岛坡、陆坡和台湾宜兰浇滩的碎屑沉积物。受控于海底地形、滞流环境和构造岩浆活动以及伴生的浅源地震。 冲绳海槽海底表层浊流沉积物,形成在晚更新世末次冰期最盛期、末次冰期末和冰后期三个阶段,以末次冰期最盛期阵发频繁,浊积物最发育,与气候寒冷期有一定的相关性。 相似文献
9.
根据对云南腾冲青海湖泊沉积钻孔样品的粒度特征、总有机碳、碳酸盐、磁化率及年代学分析测试,探讨了各指标的变化特点及其环境指示意义,指出了云南高原湖泊沉积物化指标的特殊性及其变化特点.在此基础上,重建了云南腾冲地区末次冰消期(15830a B.P.)以来沉积环境与气候干湿变化历史.通过青海沉积物年代序列的重建和综合各物化参数分析得出,云南腾冲地区自15830a B.P.以来总体呈现冷湿-温湿-暖干-温和偏干的气候演变过程,并可分为4个阶段,即15830～12790a B.P.气候温凉偏湿;12790～4680a B.P.为温暖湿润期,湖泊水位高,气候湿暖,降水多;4680～312a B.P.气候特征呈现出从温湿到暖干气候逐渐演化,降水减少,湖泊水位下降;312a B.P.以来气候特征为前期温和湿润,后期具有暖干化特征,反映了近几十年来全球气候变暖导致的气候变化趋势并叠加了研究区人类活动对区域环境的影响. 相似文献
10.
基于AMS14C测年、有机碳、氮含量及其同位素等指标分析,探讨了冲绳海槽中南部OKT-3孔末次冰消期以来沉积物有机质来源及其对古海洋环境演化的响应。结果显示,OKT-3孔沉积物中有机质主要由中国大陆和中国台湾等陆源有机质,以及海洋自生有机质组成。末次冰消期至全新世晚期（17.3~4 ka B.P.）,中国大陆源有机质贡献逐渐下降,中国台湾源有机质贡献逐渐上升,表明海平面变化、黑潮变动是该阶段有机质来源的主要控制因素。4~1.5 ka期间,陆源有机质供给变化趋势与黑潮变动不一致,表明该时期陆源输入非黑潮单一控制,还可能受季风降雨等变化影响。值得注意的是,OKT-3孔海源有机质贡献在B-A和PB时期高、YD时期低,与北太平洋地区的生产力变化相似,反映了北太平洋中层水（NPIW）对海水表层生产力的控制作用,NPIW是连通冲绳海槽与北太平洋的重要纽带。 相似文献
11.
《Boreas: An International Journal of Quaternary Research》2018,47(4):1003-1021
Exceptionally high sedimentation rates in Arctic fjords provide the possibility to reconstruct environmental conditions in high temporal resolution during the (pre‐)Holocene. The unique geographical location of Svalbard at the intersection of Arctic and Atlantic waters offers the opportunity to estimate local (mainly glacier‐related) vs. regional (hydrographic) variabilities. Sedimentological, micropalaeontological and geochemical data from the very remote, glacier‐surrounded Wahlenbergfjord in eastern Svalbard provides information on glacier dynamics, palaeoceanographic and sea‐ice conditions during the Holocene. The present study illustrates a high meltwater discharge during the summer insolation maximum (c. 11.3–7.7 ka) when the intrusion of upwelled relatively warm Atlantic‐derived waters led to an almost open fjord situation with reduced sea ice in summer. Around 7.7 ka, a rapid hydrographic shift occurred: the dominance of inflowing Atlantic‐derived waters was replaced by a stronger influence of Arctic Water reflecting regional palaeoceanographic conditions evident in the benthic foraminiferal fauna also at Svalbard's margins. Neoglacial conditions characterized the late Holocene (c. 3.1–0.2 ka), when glaciers probably advanced as cold atmospheric temperatures were decoupled from the advection of relatively warm intermediate waters probably caused by an extending sea‐ice coverage. Accordingly, our data show that even a remote, glacier‐proximal study site reflects rapid as well as longer‐term regional changes. 相似文献
12.
末次盛冰期以来青藏高原东北部共和盆地气候与环境变化研究进展 总被引：2，自引：1，他引：1
青藏高原东北部共和盆地气候与环境变化文献分析认为:末次盛冰期(14 C年龄14ka BP或16cal ka BP之前)地层沉积主要为风成砂和黄土,冰缘地貌发育,气候寒冷干燥,植被可能为干旱荒漠或荒漠草原;末次冰消期(14 C年龄14ka BP或16 cal ka BP-Younger Dryas,缩写YD事件)地层发育古土壤,湖泊水位明显上升,并显著的捕捉到冷暖事件(Blling-Allerd,缩写B/A、YD)的信息,气候趋于温暖湿润,对应植被为荒漠草原;全新世8.5ka BP(14 C年龄)之前区域温度和湿度不同程度增加,湖泊水位较高,地层发育古土壤,植被为荒漠草原或干草原;8.5～7.0ka BP(14 C年龄)风成砂出现,古土壤发育中断,气候寒冷干燥,为全新世新冰期第一期;7.0～3.0ka BP(14 C年龄)古土壤显著发育,高水位湖面出现,水热组合达到全新世最佳,植被向干草原方向演化,但期间也存在千–百年尺度的冷事件(全新世新冰期第二期);3.0ka BP(14 C年龄)以来气候向温凉(寒冷)干燥方向发展.太阳辐射等外部因素变化并触发地球系统内部各个圈层之间相互作用是区域气候、环境变化的主要驱动力.同时,对研究现状进一步剖析,阐明其存在的问题,并提出气候、环境变化研究的发展方向. 相似文献
13.
玛旁雍错位于青藏高原西南部,是研究印度季风演化的理想地区之一。利用活塞采样器在玛旁雍错75 m水深处获取了一根4.69 m长岩芯,利用^210Pb和AMS^14C测年确定了岩芯的年代,根据元素含量(XRF扫描)、总有机碳(TOC)、总无机碳(TIC)和总氮(TN)等代用指标,重建了该地区14 cal.ka B.P.以来气候环境变化。结果显示,冰消期(14~12 cal.ka B.P.),TOC和TIC含量变化显示了湖区环境整体上较为暖湿;12.0~11.4 cal.ka B.P.,径流明显减弱,可能是新仙女木事件的反映;早中全新世(11.4~3.4 cal.ka B.P.),湖区环境整体上以暖湿为主,气候有所波动,出现了两次冷事件(10.2~9.8 cal.ka B.P.和8.2 cal.ka B.P.左右),7.4~6.6 cal.ka B.P.,出现了一个暖时期;晚全新世(3.4~0 cal.ka B.P.),湖区环境整体上趋向于干旱化,并伴有两次相对湿润时期(2.6~2.0 cal.ka B.P.和1.4~1.0 cal.ka B.P.)。玛旁雍错环境变化表明,晚冰期以来(14.0~3.4 cal.ka B.P.),受到太阳辐射的影响,印度季风带来的降水以及冰川融水较多,湖区环境较为湿润,整体上有利于内源生物的生存;晚全新世(3.4~0 cal.ka B.P.),北半球夏季太阳辐射量减少,印度季风减弱,径流减弱,湖区环境朝干旱化方向发展。 相似文献
14.
基于内蒙古东南缘西拉木伦河上游刘家店河湖相剖面的粒度、磁化率、微量元素地球化学指标,重建该区35 ka BP以来的气候演化过程。结果表明,在MIS 3晚期(35.23~25.15ka BP)研究区气候条件总体温暖湿润,并伴有区域变干的趋势;MIS 2阶段(25.15~11.13 ka BP)气候整体寒冷干燥,但叠加有短暂回暖气候事件。剖面记录的末次盛冰期(LGM)出现于22.25~18.47 ka BP,此时气候极度干冷;MIS 2阶段叠加了两个短暂气候适宜期,分别出现于18.47~16.24 ka BP和14.72~11.13 ka BP。在11.13 ka BP前后研究区进入全新世,气候变得暖湿。刘家店剖面的气候记录与周边气候记录具有可对比性,揭示了区域上东亚夏季风进退具有一致性,并认为自MIS 3晚期以来东亚夏季风受北半球太阳辐射及冰量的共同驱动。此外,刘家店剖面记录揭示的千年尺度气候变化对典型气候事件具有一定的响应,推测这些千年尺度的季风强度变化可能与北大西洋经向翻转环流(AMOC)相关。 相似文献
15.
《Boreas: An International Journal of Quaternary Research》2018,47(1):175-188
Expansion of fresh and sea‐ice loaded surface waters from the Arctic Ocean into the sub‐polar North Atlantic is suggested to modulate the northward heat transport within the North Atlantic Current (NAC). The Reykjanes Ridge south of Iceland is a suitable area to reconstruct changes in the mid‐ to late Holocene fresh and sea‐ice loaded surface water expansion, which is marked by the Subarctic Front (SAF). Here, shifts in the location of the SAF result from the interaction of freshwater expansion and inflow of warmer and saline (NAC) waters to the Ridge. Using planktic foraminiferal assemblage and concentration data from a marine sediment core on the eastern Reykjanes Ridge elucidates SAF location changes and thus, changes in the water‐mass composition (upper ˜200 m) during the last c. 5.8 ka BP. Our foraminifer data highlight a late Holocene shift (at c. 3.0 ka BP) in water‐mass composition at the Reykjanes Ridge, which reflects the occurrence of cooler and fresher surface waters when compared to the mid‐Holocene. We document two phases of SAF presence at the study site: from (i) c. 5.5 to 5.0 ka BP and (ii) c. 2.7 to 1.5 ka BP. Both phases are characterized by marked increases in the planktic foraminiferal concentration, which coincides with freshwater expansions and warm subsurface water conditions within the sub‐polar North Atlantic. We link the SAF changes, from c. 2.7 to 1.5 ka BP, to a strengthening of the East Greenland Current and a warming in the NAC, as identified by various studies underlying these two currents. From c. 1.5 ka BP onwards, we record a prominent subsurface cooling and continued occurrence of fresh and sea‐ice loaded surface waters at the study site. This implies that the SAF migrated to the southeast of our core site during the last millennium. 相似文献
16.
A narwhal (Monodon monoceros) tusk from 34 m above sea level and located at 82°N on the northwest coast of Ellesmere Island has been radiocarbon dated at 6,830 ± 50 B.P. It was collected from a narrow coastal strip which is isolated from the adjacent Arctic Ocean by glacier ice, ice shelf and multiyear pack ice. The specimen represents an early Holocene range extension of 400–700 km over the present. Because the narwhal requires abundant open water to survive, the Holocene tusk is an important independent item of proxy data on palaeoclimatic change. Contemporary migration routes are directly related to seasonal sea ice in the inter-island channels of the central Canadian Arctic archipelago. The presence of a narwhal on the northwest Ellesmere Island coast at 6,830 ± 50 B. P. suggests that sea ice and ice-shelf conditions were more favourable at that time. A comprehensive chronological framework for late Quaternary and Holocene geomorphic/climatic events from northern Ellesmere Island records a warm early Holocene characterized by abundant driftwood entry into the high Arctic. This was followed by a mid-Holocene climatic deterioration during which the ice shelves of the Ellesmere coast formed. Therefore, the narwhal tusk is further evidence that a period of maximum postglacial warmth occurred during the early Holocene in the Canadian high Arctic. 相似文献
17.
B. Gehrke K. S. Lackschewitz H. -J. Wallrabe-Adams 《International Journal of Earth Sciences》1996,85(3):525-535
Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to
identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses.
The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary.
Holocene sediments are characterized by high contents of smectite, mainly of less developed crystallinity. In the spatial
distribution of clay minerals high smectite concentrations on the eastern flank and slightly decreasing concentrations on
the western flank of the Reykjanes Ridge indicate the action of bottom-water transport. The smectite originates mainly from
the volcanogenous Icelandic shelf and reflects the influence of Iceland-Scotland Overflow Water (ISOW). Stratigraphic variability
in the clay mineral composition reflects predominantly the influence of different sources, resulting from oceanographic and
glacial transport processes. During glacial time sediment transport is due mainly to input by icebergs. Increasing amounts
of illite, chlorite, and kaolinite characterize ice-rafted sediments of the “Heinrich layers”. In these sediments smectite
crystallinity is well developed. In contrast, several other ice-rafted layers contain smectite with low crystallographic order,
similar to smectites of Holocene age. The icelandic source was proved by distinct amounts of basaltic glass in the coarse-grained
sediment. At approximately 55 ka increasing amounts of chlorite and kaolinite suggest an enhanced influx of warm North Atlantic
surface waters. This hypothesis is supported by a high carbonate shell production at this time. Relative low concentrations
and the well-developed crystallinity of smectite minerals characterize the Last Glacial Maximum (LGM; 18–16 ka), indicating
a reduced supply of fine icelandic material. Shortly after the LGM, at the beginning of termination IA, a distinct increase
in fine-grained quartz (<2μm) and smectite are visible, which are proposed to reflect a supply of fine-grained ice-rafted
material. At 13 ka linear increasing smectite concentrations of lower crystallographic order indicate increasing supply of
fine-grained material from Iceland, linked to reinitiation of bottom currents of the ISOW. Full reinitiation is indicated
at around 10 ka, where a strong increase in smectite of low crystallographic order is detected. 相似文献
18.
通过对云南寻甸仙人洞XR1石笋进行TIMS-U系测年、氧碳同位素、有机碳含量分析,重建了寻甸地区中全新世季风气候演化模式:(1)8.0～6.0kaB.P.为温暖湿润期;(2)6.0～5.1kaB.P.为气候突变期,气候由温湿变为冷干;(3)5.1～2.1kaB.P.为凉干期。通过石笋有机碳含量与石笋δ18O记录对比,认为石笋有机碳可以反映气候变化,但是存在滞后效应。最后,利用XR1石笋δ18O记录与北半球33°N太阳辐射量,本文初步分析了云南寻甸地区中全新世气候变化的驱动因素:寻甸地区中全新世气候的整体变化趋势受33°N太阳辐射量控制,同时受中全新世火山活动的影响。 相似文献
19.
Field stratigraphy and optical and radiocarbon dating of lateral moraines in the monsoon dominated Dunagiri valley of the Central Himalaya provide evidence for three major glaciations during the last 12 ka. The oldest and most extensive glaciation, the Bangni Glacial Stage-I (BGS-I), is dated between 12 and 9 ka, followed by the BGS-II glaciation (7.5 and 4.5 ka) and the BGS-III glaciation (∼1 ka). In addition, discrete moraine mounds proximal to the present day glacier snout are attributed to the Little Ice Age (LIA). BGS-I started around the Younger Dryas (YD) cooling event and persisted till the early Holocene when the Indian Summer Monsoon (ISM) strengthened. The less extensive BGS-II glaciation, which occurred during the early to mid-Holocene, is ascribed to lower temperature and decreased precipitation. Further reduction in ice volume during BGS-III is attributed to a late Holocene warm and moist climate. Although the glaciers respond to a combination of temperature and precipitation changes, in the Dunagiri valley decreased temperature seems to be the major driver of glaciations during the Holocene. 相似文献