青藏高原东北缘临夏盆地王家山地区沉积环境分析与构造隆升

通过对青藏高原东北缘临夏盆地王家山地区新生代地层沉积相研究，划分出7个沉积旋回；盆地沉积与高原隆升的响应关系揭示出高原29Ma以来先后经历了初期隆升至稳定阶段(29．0—21．4Ma)、中期随升至稳定阶段(21．4—6．25Ma)、后期逐步隆升阶段(6．25—3．58Ma)和晚期急剧强烈隆升阶段(3．58—0Ma)，可见青藏高原的隆升是一个多阶段、不等速和非均变的复杂过程．     

临夏盆地1.95MaBP的气候转型事件与青藏高原隆升作用于大气的临界高度

湖相地层孢粉分析的结果表明，临夏盆地在1．95MaB．P．前后发生过一次重要的气候转型事件。在此之前，南海热带季风信号在地层记录中存在较强的表现，在此之后热带季风信号减弱而高纬冰盖信号加强。CaCO3指标的周期分析同样表明，在1．95MaBP前后确实出现了气候的主导周期转型，在此之前，气候变化周期以类岁差的25kyr周期为主，而在此之后，以类倾角的38kyr周期为主。发生在临夏盆地1．95MaBP的这次气候转型事件表明青藏高原地面在当时隆升到一个可以改变周围地区大气环流的临界高度，如果以青藏高原在2．6MaB．P．- 0．6MaB．P．的平均抬升速率推算，这一临界高度可能在2500m左右。     

张家口地区张家口组火山岩的LA—ICP—MS测年及其地质意义

张家口组的建组剖面在张家口地区．通过对张家口地区典型剖面上4个样品的测年,结果表明张家口地区张家口组火山岩的年龄范围为（143．0±3．7）-（136．1±1．4）Ma左右,跨越了滦平地区张家口组和土城子组的年龄范围之和．在冀北的滦平、赤城等地区,张家口组与土城子组之间为整合接触至过渡关系．暗示上述地区张家口组和土城子组是相同构造背景下的产物,并且在西部（张家口地区）火山作用开始的时间较早（在143Ma左右）、持续的时间较长（143—136Ma左右）,而在东部（滦平地区）火山作用开始的时间较晚,主要作用的时间在135—136Ma左右．对承德、平泉地区的“张家口组”进行了分析．     

黄陵隆起形成（165—100Ma）的碎屑岩磷灰石裂变径迹热年代学约束

黄陵隆起东部9个碎屑岩的磷灰石裂变径迹（AFT）分析表明：∈2-J3碎屑岩的AFT热年龄148—104Ma（径迹长度为12．6313．79μm）代表了沉积物经埋藏加热和径迹完全退火后的抬升冷却年龄;K2碎屑岩的AFT热年龄110-81．5Ma（径迹长度为11．22—12．71μm）表明盆地沉降幅度达到但没有超过AFT的部分退火区间（80—120℃）;3个样品进行AFT多元组分模拟获得了质量较好的热历史曲线．黄陵隆起AFT的时间-温度演化曲线包括四分段,即-2．0--2．1℃／Ma（425Ma→320Ma）,0．2—0．3℃／Ma（320Ma→165Ma）,1．9—2．7℃／Ma（165Ma→100Ma）和0．2—0．5℃／Ma（100Ma以来）．综合AFT年龄、热历史曲线与地层分布等特点,认为由杂岩核与中、古生界环翼组成的黄陵穹窿形成于165—100Ma,这一快速的冷却抬升事件同时造成了隆起周缘J3／K1之间的角度不整合以及K1-K1 2大套的粗碎屑砾岩堆积．     

青藏高原东北部西宁盆地中始新世-渐新世沉积物颜色与气候变化

始新世-渐新世是古近纪气候变化中最显著的时期.通过对西宁盆地42.5～26.0 Ma沉积物颜色指标的详细分析,发现颜色参数L*,a*,b*曲线明显以32.8 Ma为界分为上下两段.其中:L*值在下段(42.5～32.8 Ma)波动剧烈并呈缓慢降低趋势,至32.8 Ma左右大幅度降低,此后(32.8～26.0 Ma)波动变小、稍有回升;a*,b*值则与L*值的变化趋势相反,在下段(42.5～32.8 Ma)呈逐渐增大趋势,剧烈波动,在32.8 Ma左右时突然大幅度升高.至上段波动变小.结合西宁盆地孢粉、有机质及CaCO3质量分数变化的特征分析,该区域在32.8 Ma时可能发生大幅度的降温事件(对应于海洋记录所揭示的Oi-1事件),此事件之前气候干旱程度相对较弱、氧化作用逐渐增强、气候波动剧烈.在Oi-1事件之后大陆性干旱程度增强、氧化强烈、气候波动幅度较小.这是在该区高分辨率获得Oi-1事件前后气候变化的记录.它对始新世-渐新世全球气候变冷背景下陆地系统响应研究具有重要意义.     

东经90°海岭远洋沉积物非碳酸盐组分的粒度特征及环境指示意义

对东经90°海岭北部ODP758站位远洋沉积物进行了粒度分析，得到了3．6Ma以来非碳酸盐组分的粒度变化曲线，得出在3．6～2．8Ma之间，非碳酸盐组分的粒度以2bLm为主；2．8Ma至今，粒度增大至3μm左右，并且比较稳定地保持增大趋势的结论，这与南亚冬季风的爆发和加强密切相关。印证了青藏高原的隆升对亚州季风的影响。     

大别山造山带白垩纪热窿伸展作用—锆石（U—Tu）／He年代学证据

对大别山造山带的岳西－罗田核部及其南北两翼的13个锆石样品的（U－Th)/He测年结果表明，各样品锆石（U－Th)/He年龄介于85－155Ma之间，核部He年龄为85－107Ma，两翼年龄介于114－155Ma之间，反映岳西－罗田穹隆实际上是一个核部比两翼要热得多的热穹隆，形成大别穹状核杂岩这一热伸展事件可能持续到85Ma左右，核部岩石自85Ma以来的剥露量要比两翼多1528．8m.     

从中国古植被记录看东亚季风的年龄

我国最近发现的早中新世季风记录，对东亚季风系统何时形成又提出了疑问．现代季风系统的一个明显特征，在于它打乱了行星气候系统纬向分布的带状模式，因而地质记录中季风气候地理模式的出现，就应当意味着季风系统的建立．据此汇总了中国大陆125个地点所获得的古植物和岩性资料，揭示了两种完全不同的气候分带模式：早第三纪宽阔的干旱带由西向东横跨中国大陆，而晚第三纪至今的干旱带仅局限在中国西北部．渐新世／中新世交界时气候系统的大改组，就是现代东亚季风建立的证据．其后，季风系统在晚第三纪又经历了巨大变化，包括15～13Ma前、8Ma、3Ma前干旱气候的加剧和季风系统的加强．所获得的新资料并不支持亚洲季风系统起源于约8Ma前这一观点，而认为东亚大约是在晚渐新世向季风气候转变这一假设更为合适．     

Mg65Cu25Y10-xLax块体非晶合金的玻璃形成能力

传统的非晶合金多为粉末或者薄带，这样就大大限制了非晶合金的许多优异性能的发挥以及在工业中的应用，因此研究开发块体非晶合金有重要的理论与应用价值．用真空吹铸法制备了直径2mm的Mg65Cu25Y10-xLax（x=0、0．35、1、2）块体非晶合金梓，采用X射线衍射（XRD）、差热分析（DTA）分别对非晶合金的结构和形成能力进行了研究．研究结果表明，x=2时，合金具有最高的玻璃形成能力（k=0．5872）；当x=0．35时，也就是当原子半径参数λ=0．18时，不但没得到共晶点的成分，反而其玻璃形成能力比Mg65Cu25Y10还差；当x=3、4时，此时在非晶基体中已经出现晶体相，说明其玻璃形成能力显著降低．     

兰州地区1.0Ma黄河阶地的发现和0.8Ma阶地形成时代的重新厘定

通过对阶地砾石层上覆风成黄土的地层分析及其磁性地层学研究，在兰州地区墩洼山黄河阶地和五一山黄河阶地之间发现了一级新的阶地，其形成时代为1.0Ma BP，记录了兰州地区在这一时期发生的黄河强烈下切事件.对黄河第四级阶地（T4）上五一山和枣树沟两个黄土剖面的光释光（OSL）和古地磁年代学研究结果表明，在兰州地区黄河T4阶地的形成时代不是以前所认为的0.6Ma BP，而是0.86Ma BP，从而解决了地貌学界对兰州地区是否存在形成时代为0.8Ma BP左右阶地的长期疑问.兰州地区黄河1.0Ma BP新阶地的发现和T4阶地形成时代的重新厘定为黄河流域的地貌演化研究提供了新的资料.     

西风区湖泊沉积物中砷元素对气候环境变化的响应研究——以新疆巴里坤湖为例

巴里坤湖是我国西风区古气候环境演变研究的理想区域.根据BLK-1剖面多指标建立了巴里坤湖9 000 cal a BP以来的时间序列,了解其气候演变的过程.结合巴里坤湖古气候演变及砷元素含量的波动变化,发现砷元素变化响应气候环境的演变:气候冷干时期,砷含量较多;而暖湿时期则相对少.此外,砷含量的变化很好地指示了全新世的气候突变事件.巴里坤湖沉积物中砷元素主要来源于湖泊周边基岩受物理风化产生的碎屑,并经由风力带入湖中沉积.干旱的气候环境下,砷的沉积速率较湿润期变化明显.研究结果表明,砷对于我国西风区的古气候环境演变及气候突变事件具有指示作用;砷沉积速率的突变表明在干旱气候环境条件下,砷可能比其他元素更为敏感.不同气候环境下砷元素的来源及波动,也为砷污染的防治提供参考.     

皖南风尘堆积—古土壤序列磁化率初步研究

将北方黄土研究中广泛应用的磁化率参数引入江南第四纪风尘堆积区研究,对安徽宣城风尘堆积－古土壤序列向阳剖面进行了系统的磁化率化采样、测试,根据该剖面磁化率及其曲线的变化特征,对其古气候指示意义进行了初步的探讨．     

2000～2018年黄土高原沙尘天气遥感监测及尘源分析

利用19年（2000~2018）MODIS L1B数据对黄土高原102次沙尘天气过程进行遥感监测与分析,以探究黄土高原沙尘天气发生的时空规律。结果表明,黄土高原沙尘天气呈减少趋势,沙尘频发季节为春季。黄土高原沙尘源地主要分布在其西北部,位于沙地和沙漠区、农灌区与黄土丘陵沟壑区、黄土高原沟壑区等生态脆弱的原生沙尘暴带。黄土高原典型的沙尘源为活动沙丘及丘间沙地、干涸湖泊河道和农田等,表明沙尘天气频发是由自然因素和人为因素共同导致的。沙尘天气的遥感监测捕捉了黄土高原沙尘活动的时空变化特征,高效地识别了沙尘源地和尘源类型,对黄土高原气候变化、生态环境变化研究和环境修复与评价具有重要指导意义。     

Climate instability in the Yili region, Xinjiang during the last glaciation

The climate is influenced by westerlies year in year out and the aeolian loess is widespread in the Yili region, the Xinjiang Uygur Autonomous Region. Through the study of the loess section with a thickness of 21.5 m, much useful information about climatic change in this region during the last glaciation was gotten. Grain size analysis of loess samples in the section showed that the climatic change in the Yili region was of instability during the last glaciation and similar to those of the North Atlantic Ocean and Greenland. In correspondence with the Heinrich events, the percentage of the size fraction of loess with grain size less than 10 μm decreased in cold stadials in the Yili region. This result suggests that the westerly wind be strengthened during the cold periods. Compared with the stadials, the content of the loess with grain size less than 10 μm was increased in interstadials, which indicated that the strength of the westerly wind was weakened. It is obvious that the climate was instable not only in the North Atlantic Ocean and polar regions, but also in other areas of Northern Hemisphere during the last glaciation.     

1.2～0.6MaBP青藏高原的隆升与东亚地表各圈层的相互作用

结合近年来黄土、河流阶地、冰冻圈、沙漠、植被等地表各个圈层在1.2～0.6 MaBP青藏高原构造隆升期间环境变化的最新研究成果,综合论述了在此期间青藏高原的隆升对地表其他各个圈层的影响.研究表明:1.2～0.6 MaBP期间,青藏高原的隆升对东亚地表环境产生了重大影响,中国内陆主要沙漠(主要是西部沙区的沙漠)在这一时期形成并极端扩张;黄土在祁连山、昆仑山、天山等高山山前和西秦岭等地开始大范围地堆积;以昆仑山和念青唐古拉山为代表的西部高山开始了冰冻圈的发育,各地植被变化都不同程度地反映了环境的逐步干旱化.结合这些研究,提出了1.2～0.6 MaBP期间东亚地表圈层间相互作用的简单模式,并探讨了青藏高原隆升与地表圈层变化之间的内在耦合.     

Reconstruction of the spatial patterns of desert/loess boundary belt in North China during the Holocene

The desert/loess boundary belt is the transi-tional region between desert and loess, where aeolian sandand loess interlock in space and alternate in time. It, being seriously unstable in space-time, sensitive to climatic changes and with fragile ecological environment, is an ideal region for studying the global climate change. There are deposi-tional sequences of paleosol with sub-horizontal interbedded aeolian sand and loess, and the stratigraphical evidences show that there widely exist 3—4 layers paleosol in sand lands of northeastern China, 4—5 layers in Mu Us Sandy Land and Hunshandake Sandy Land, more than 4 layers in the Qinghai Lake region and the Gonghe Basin of Qinghai Province during the Holocene. These indicate that the desert has experienced several times of extending and compacting, along with which the desert/loess boundary belt vibrated. It possesses good coherence with global climate change and eustasy. The coherence shows that the monsoon change in East Asia is the primary driving factor for the swing of desert/loess boundary belt. Besides, human influence con-stantly intensified the swing of the belt, especially in the south of Mu Us Sandy Land during the 2000—3000 aBP.     

Stepwise advance of the Mu Us Desert since late Pliocene: Evidence from a red clay-loess record

Analyses of paleomagnetic polarity reversals, magnetic susceptibility and grain size on the red clay-loess sequence, about 280 m thick, at Jingbian show that this sequence contains most of the stratigraphic units recorded in the standard red clay-loess sections of the Loess Plateau over the past 3.5 Ma. Using sand particle percentage ( > 63 μm%) of the eolian sequence as a proxy indicator of desert extent and aridity in the dust source regions, it is found that during the past 3.5 Ma, there are three important climatic events indicating the advance of the Mu Us Desert. The events occurred at about 2.6, 1.1 and 0.6 MaBP, respectively. The stepwise advance of the Mu Us Desert may be linked closely to increase in global ice volume and uplift of the Tibetan Plateau in the late Cenozoic.     

Climate instability during the last glaciation recorded in the Yuanbu loess section

Abrupt events within the Linxia Yuanbu loess section in the western Loess Plateau in China were investigated. The climatic proxy index of the content of mean grain-size and >4 μm grain-size fraction of the section was used as a climatic indicator, and a moving average method was applied in the statistical analysis to extract the abrupt events recorded in the section. It was found that the loess of the last glaciation recorded not only the abrupt events teleconnected with the high-latitude North Atlantic and Greenland regions but also as many as 15 abrupt events in addition to the Heinrich (H) and Younger Dryas (YD) events. This indicates that abrupt climate changes were typical of the climate changes occurring in the Loess Plateau during the last glaciation. The widely recognized mechanisms of the abrupt climate changes, including the heat transfer theory of the North Atlantic Ocean, the atmospheric circulation theory, and the theory of the interaction between low-latitude ocean and the atmosphere remains to be discussed. Perhaps this problem could be resolved by revealing the relation between the evolution of the features of the East Asian monsoon climate and the climate in the surrounding areas. Through a detailed study of the features of the Heinrich and YD events, criteria on which the abrupt events recorded in the loess could be distinguished were tentatively defined. The events were associated with a large grain size, high carbonate content, high lightness, low susceptibility, low redness and low yellowness. In addition, the variation amplitude of the adjacent peak and valley on the curve of the content of the mean grain-size and >40 μm grain-size fraction was larger than 3.4 μm and the content of >40 μm grain-size fraction was larger than 2.0 μm. Lastly, the length of the variation time was less than 500 years. If all these criteria were met, the event was viewed as an abrupt event.     

青藏高原：全球气候变化的驱动机与放大器──Ⅰ 新生代气候变化的基本特征

除周期性气候波动外，新生代气候变化的基本特征是阶梯状气候变冷、波动幅度的不断增加和气候波动周期的转变。深海氧同位素记录表明新生代曾发生至少三次快速变冷事件，它们分别发生在３６，１５和２．４ＭａＢＰ前后。根据来自北大西洋的深海氧同位素记录，第四纪气候变化的趋势是波动幅度增加、频率降低。Ｂ／Ｍ界限附近，气候波动周期由４１ｋａ转变为１００ｋａ。黄土高原上黄土地层与磁化率研究揭示，现代东亚季风出现于２．４Ｍａ前，并于１．１和０．６ＭａＢＰ前后两度加强，现在的季风环流形势形成于０．６ＭａＢＰ，米兰柯维奇理论不能解释上述新生代气候的阶梯状变冷、第四纪气候的阶段性和东亚季风的形成及加强，因此除轨道因素外，还有别的因素控制气候变化。     

Holocene abrupt climate shifts recorded in Gun Nuur lake core, northern Mongolia

A continuous 7.44 m lake core was successfully drilled at Gun Nuur Lake, northern Mongolia, and analyses on environment magnetic parameters, organic matter content and organic δ^13C were conducted in an attempt to retrieve the Holocene chronosequence of climatic changes based on 6 AMS ^14C dates. We found that the Holocene climate in northern Mongolia has been alternating between cold (or cool)/wet conditions and warm/arid conditions, and also punctuated with a series of abrupt climate shifts. The abrupt climate shifts occurred around 1750, 2800, 4000, 5200, 7200, and 9200 aBP (^14C age), being chronologically correlative to those abrupt climatic events recorded in the high-latitude North Atlantic Ocean. The correlation indicates that the climatic changes in northern Mongolia were linked with those in the North Atlantic Ocean probably via the North Atlantic Oscillation-affected westerly winds. The strength and position of westerly winds might have modulated the Siberian-Mongolian high pressure system (winter monsoon), directly influencing the climate in China.