Evolution of stomatal and trichome density of the Quercus delavayi complex since the late Miocene

A fossil oak species,Quercus tenuipilosa Q.Hu et Z.K.Zhou,is reported from the upper Pliocene Ciying Formation in Kunming,Yunnan Province,southwestern China.The establishment of this species is based on detailed morphologic and cuticular investigations.The fossil leaves are elliptic,with serrate margins on the apical half.The primary venation is pinnate,and the major secondary venation is craspedodromous.The tertiary veins are opposite or alternate-opposite percurrent with two branches.The stomata are anomocytic,occurring only on the abaxial epidermis.The trichome bases are unicellular or multicellular.The new fossil species shows the closest affinity with theextant Q.delavayi and the late Miocene Q.praedelavayi Y.W.Xing et Z.K.Zhou from the Xiaolongtan Formation of the Yunnan Province.All three species share similar leaf morphology,but differ with respect to trichome base and stomatal densities.Q.tenuipilosa.Q.praedelavayi,and Q.delavayi can be considered to constitute the Q.delavayi complex.Since the late Miocene,a gradual reduction in trichome base density has occurred in this complex.This trend is the opposite of that of precipitation,indicating that increased trichome density is not an adaptation to dry environments.The stomatal density(SD)of the Q.delavayi complex was the highest during the late Miocene,declined in the late Pliocene,and then increased during the present epoch.These values show an inverse relationship with atmospheric CO_2 concentrations,suggesting that the SD of the Q.delavayi complex may be a useful proxy for reconstruction of paleo-CO_2 concentrations.     

Evolution of the East Asian monsoon and its response to uplift of the Tibetan Plateau since 1.8 Ma recorded by major elements in sediments of the South China Sea

Evolution of the East Asian monsoon and its response to uplift of the Tibetan Plateau has been investigated in the study of global change. Core sediment samples drilled in the South China Sea during ODP Leg184 are the best materials for studying long-term variability of the East Asian monsoon. R-mode factor analysis of major elements in the fine grain-sized carbonate-free sediments (<4 μm) of the upper 185 mcd splice of ODP Site 1146 drilled during Leg184 in the South China Sea shows that Ti, TFe2O3, MgO, K2O, P, CaO, and Al2O3 are representative of a terrestrial factor. The variation in the terrestrial factor score is subject to chemical erosion in the source region and thus indicates the evolution of the East Asian summer monsoon. The terrestrial factor score has three stepwise decreases at ~1.3 Ma, ~0.9 Ma, and ~0.6 Ma, indicating the phased weakening of the East Asian summer monsoon is related to wholly stepwise, quick uplifts of the Tibetan Plateau since 1.8 Ma. The periodic fluctuation of the terrestrial factor score since ~0.6 Ma indicates that the glacial-interglacial cycles have been the main force driving the evolution of the East Asian monsoon. As in the case of Chinese loess, the long-term evolution of the East Asian monsoon recorded in sediments of the South China Sea reflects a coupled effect of the glacial-interglacial cycle and uplift of the Tibetan Plateau.     

Modeling the climate effects of different subregional uplifts within the Himalaya-Tibetan Plateau on Asian summer monsoon evolution

Considering the different uplifting time of different subregions of the Himalaya-Tibetan Plateau(TP),a series of numerical simulations have been conducted with the Community Atmosphere Model(CAM4) developed at the National Center for Atmospheric Research to explore the effects of the phased tectonic uplift of the Himalaya-TP on the evolution of Asian summer monsoons.The results show that the uplifts of the Himalaya and northern TP significantly affect the evolutions of South Asian summer monsoon and northern East Asian summer monsoon respectively.That is,the tectonic uplift of the Himalaya intensifies the South Asian summer monsoon circulation and increases the precipitation in South Asia,whereas the uplift of the northern TP intensifies the northern East Asian summer monsoon circulation and increases the precipitation in northern East Asia.Compared with previous simulations,current comparative analyses of modeling results for different subregional uplifts within the Himalaya-TP help deepen our understanding of the evolutionary history of Asian monsoons.     

塔中低凸起的结构特征及其演化

根据地震资料剖析了塔中低凸起的结构特征及其演化史 .结果表明 ,塔中低凸起是塔里木早古生代盆地经晚加里东—早海西期构造改造作用最终形成的的下古生界残余古隆起 ,经历了初始形成、定型演化和埋藏三大演化阶段 .隆起区断裂构造发育 ,主要存在北西、北西西和北东东两大构造方向 ,北西、北西西向断裂控制了低凸起的结构特征 ,北东东向构造对北西、北西西向断裂在走向上具有分段特征 .目前 ,高产油井多集中在北东东向构造与北西或北西西向断裂相交部位或附近 ,进一步深入研究这两组构造 ,对勘探有重要的指导意义     

Late Miocene–early Pleistocene paleoproductivity variations of the Lop Nor in the Tarim Basin and its implications on aridification in Asian Interior

Extensive lacustrine deposits in the eastern Tarim Basin provide records of climate change influenced by the westerly winds and the Asian monsoon. To char- acterize the evolution of climate change in this region, we analyze elemental concentrations of barium （Ba） from the Ls2 drill core of Lop Nor, a paleo-lakebed located in the eastern Tarim Basin. Biogenic Ba concentrations from this drill core display a large-amplitude oscillation that gener- ally follows a pattern similar to that of Artemisia content and ostracod assemblages, suggesting that is may serve as an index for climate change experienced in the basin. Our results indicate that biogenic Ba is especially sensitive to precipitation. All climatic proxies served in this study vary significantly over late Miocene to early Pleistocene time period. Strong aridification of eastern Tarim in the late Miocene to the early Pliocene may be attributed to a lati- tudinal shift in the westerly winds, which would have resulted in more moisture transported to southern and eastern Tibet. The growth of the Himalaya and Tibetan Plateau may have acted as an orographic barrier that blocked moisture sourced in the south from the northern margins of the plateau. We link weaker aridification in the late Pliocene to an increased intensity of the Indian Monsoon.     

A new orang-utan relative from the Late Miocene of Thailand

The fossil record of the living great apes is poor. New fossils from undocumented areas, particularly the equatorial forested habitats of extant hominoids, are therefore crucial for understanding their origins and evolution. Two main competing hypotheses have been proposed for orang-utan origins: dental similarities support an origin from Lufengpithecus, a South Chinese and Thai Middle Miocene hominoid; facial and palatal similarities support an origin from Sivapithecus, a Miocene hominoid from the Siwaliks of Indo-Pakistan. However, materials other than teeth and faces do not support these hypotheses. Here we describe the lower jaw of a new hominoid from the Late Miocene of Thailand, Khoratpithecus piriyai gen. et sp. nov., which shares unique derived characters with orang-utans and supports a hypothesis of closer relationships with orang-utans than other known Miocene hominoids. It can therefore be considered as the closest known relative of orang-utans. Ancestors of this great ape were therefore evolving in Thailand under tropical conditions similar to those of today, in contrast with Southern China and Pakistan, where temperate or more seasonal climates appeared during the Late Miocene.     

论中国书法艺术自近代以来的衰落

中国书法艺术在封建社会有辉煌发展和繁荣的历史,但近代以来总体上呈衰落状态,在现代社会发展面临一定危机。书法艺术是中华民族数千年的情感载体,生存空间在将来比较乐观。     

Influence of the Tibetan Plateau uplift on the Asian monsoon-arid environment evolution

As one of the most important geological events in Cenozoic era,the uplift of the Tibetan Plateau(TP)has had profound influences on the Asian and global climate and environment evolution.During the past four decades,many scholars from China and abroad have studied climatic and environmental effects of the TP uplift by using a variety of geological records and paleoclimate numerical simulations.The existing research results enrich our understanding of the mechanisms of Asian monsoon changes and interior aridification,but so far there are still a lot of issues that need to be thought deeply and investigated further.This paper attempts to review the research on the influence of the TP uplift on the Asian monsoon-arid environment,summarize three types of numerical simulations including bulk-plateau uplift,phased uplift and sub-regional uplift,and especially to analyze regional differences in responses of climate and environment to different forms of tectonic uplifts.From previous modeling results,the land-sea distribution and the Himalayan uplift may have a large effect in the establishment and development of the South Asian monsoon.However,the formation and evolution of the monsoon in northern East Asia,the intensified dryness north of the TP and enhanced Asian dust cycle may be more closely related to the uplift of the main body,especially the northern part of the TP.In this review,we also discuss relative roles of the TP uplift and other impact factors,origins of the South Asian monsoon and East Asian monsoon,feedback effects and nonlinear responses of climatic and environmental changes to the plateau uplift.Finally,we make comparisons between numerical simulations and geological records,discuss their uncertainties,and highlight some problems worthy of further studying.     

Responses of South and East Asian summer monsoons to different land-sea temperature increases under a warming scenario

We used outputs from climate models that participated in the fourth assessment (AR4) of the Intergovernmental Panel on Climate Change (IPCC) to evaluate the responses of the South Asian summer monsoon (SASM) and the East Asian summer monsoon (EASM) circulations to different warming over land and ocean under a medium warming scenario, SRES A1B. Our results suggest that, even though near-surface warming over the Tibetan Plateau (TP) is greater than that over the tropical Indian Ocean (TIO) and the northwestern Pacific (NWP), the upper-tropospheric land-sea thermal contrasts between the TP and the TIO (TP-TIO) and between the TP and the NWP (TP-NWP) will decrease. At interdecadal and longer time scales, the change in the SASM circulation is consistent with the TP-TIO upper-troposphere thermal contrast. Conversely, the change in the EASM circulation is consistent with the TP-NWP lower-troposphere thermal contrast. However, at the interannual time scale, both changes in the EASM and SASM are significantly correlated with the upper-troposphere thermal contrast. Further analyses suggest that increases in moisture and changes in cloud cover induced by global warming may cause amplified upper-tropospheric warming over the TP and the oceans resulting in inconsistent changes in the vertical temperature distribution over these regions. Because the warming over the TIO and NWP is greater than that over the TP, the TP-TIO meridional and TP-NWP zonal thermal contrasts will both decrease. However, at the lower layer, the difference in thermal capacity between land and sea result in a larger thermal effect in the near-surface region of the TP than those over the surrounding oceans. We showed that a range of factors that affect thermal conditions will likely cause changes in the Asian monsoon across a range of time scales under a warming scenario. These changes reflect differences in the influence of the greenhouse effect and natural variability.     

Late Miocene decoupling of oceanic warmth and atmospheric carbon dioxide forcing

Deep-time palaeoclimate studies are vitally important for developing a complete understanding of climate responses to changes in the atmospheric carbon dioxide concentration (that is, the atmospheric partial pressure of CO(2), p(co(2))). Although past studies have explored these responses during portions of the Cenozoic era (the most recent 65.5 million years (Myr) of Earth history), comparatively little is known about the climate of the late Miocene (～12-5 Myr ago), an interval with p(co(2)) values of only 200-350?parts per million by volume but nearly ice-free conditions in the Northern Hemisphere and warmer-than-modern temperatures on the continents. Here we present quantitative geochemical sea surface temperature estimates from the Miocene mid-latitude North Pacific Ocean, and show that oceanic warmth persisted throughout the interval of low p(co(2)) ～12-5 Myr ago. We also present new stable isotope measurements from the western equatorial Pacific that, in conjunction with previously published data, reveal a long-term trend of thermocline shoaling in the equatorial Pacific since ～13?Myr ago. We propose that a relatively deep global thermocline, reductions in low-latitude gradients in sea surface temperature, and cloud and water vapour feedbacks may help to explain the warmth of the late Miocene. Additional shoaling of the thermocline after 5?Myr ago probably explains the stronger coupling between p(co(2)), sea surface temperatures and climate that is characteristic of the more recent Pliocene and Pleistocene epochs.     

Fission track age of granite batholith from Southern Tibet:implications for the plateau uplift

Fission track (FT) ages of apatite and zircon from four granite batholiths from Lhasa and Shannan areas are measured.The FT ages of apatite range from 3.2±8.3 Ma, corresponding to the uplift rates of 0.12±0.20 mm·a~(-1) during this period. The upliftheight is 580m, showing that there is not large-scale rapid uplifting in southern Tibet from 3.2 to 8.3 Ma. The zircon FT ages of Lhasabatholith are 25.9±1.7 and 32.7±2.8 Ma, yielding an uplift rate of 0.08 mm·a~(-1) between 26 and 33 Ma. Combining this work withother studies, it is suggested that the average uplift rate in southern Tibet is low from the time of collision between India and Asian conti-nents to ～3Ma. The uplift of Tibetan Plateau seems to have finished in multi-stage processes with varied rates.     

Pollen evidence from Baode of the northern Loess Plateau of China and strong East Asian summer monsoons during the Early Pliocene

The red clay eolian sequence on the Chinese Loess Plateau (CLP) is an important archive for paleoclimate change from the late Miocene to Pliocene,and can provide significant information for the controversial problems of East Asian monsoon evolution and its forcing mechanism.In this study,we present a pollen record from Baode,northern CLP.The record shows four stages of paleoecological evolution.From 5.6-4.4 Ma,a forest steppe ecosystem developed under an extremely warm period with high seasonal precipitation.Since 4.4 Ma,a drier episode occurred,which prompted parkland landscapes to develop.During 3.5-3.05 Ma,the environment changed to a rather open steppe ecosystem with a much cooler and drier climate.After 3.05 Ma,the vegetation evolved to forest steppe.Using the percentages of arboreal plants to mirror precipitation,and comparing with other published pollen data from the CLP,we find the existence of S-N directionality of the precipitation change and high percentage of arboreal plants in the entire CLP during the Early Pliocene,which suggest the CLP was characterized by a strong East Asian summer monsoon.The strong summer monsoon corresponds well to the low global ice volume,which may illuminate global climate mechanism for the summer monsoon evolution in the early Pliocene.     

Fossil evidence reveals uplift of the central Tibetan Plateau and differentiated ecosystems during the Late Oligocene

The uplift of different parts of the Tibetan Plateau caused by the collision,subduction and thickening of the Indian-Eurasian conti-nent is considered to be the...     

鄂尔多斯盆地西缘差异抬升的裂变径迹证据

目的探讨鄂尔多斯盆地西缘从南至北不同地区的差异抬升时期及抬升速率。方法利用磷灰石和锆石裂变径迹年龄的综合分析,研究盆地西缘的构造差异抬升。结果西缘北部汝箕沟地区中生代以来有两次较大的抬升时期,分别为晚白垩世和始新世,抬升速率分别为29.5 m/Ma和46.5 m/Ma。中部石沟驿地区抬升时期较早,为晚侏罗世和晚白垩世,抬升速率分别为40.0m/Ma和21.9 m/Ma。南部的差异抬升最为强烈,最早的抬升时期为晚侏罗世,在炭山地区表现明显;早白垩世末—晚白垩世南部地区发生整体抬升;中新世末期六盘山地区发生快速抬升。罗山、炭山地区相对抬升速率和后期抬升速率为46.3 m/Ma和25 m/Ma,六盘山地区则分别为22.5m/Ma和283.3 m/Ma。结论在鄂尔多斯盆地西部,最早的抬升时期为晚侏罗世,晚三叠世并没有抬升事件,故西部前陆盆地的形态始显现于晚侏罗世。西部的差异抬升导致了不同地区前陆盆地构造发展的不平衡。     

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.     

中新世以来滇西高原内红河流域区的古高程反演

流经滇西高原的红河水系将高原内被剥蚀下来的物质输送到莺歌海盆地与琼东南盆地中堆积.滇西高原隆升剥蚀区与莺歌海盆地和琼东南盆地堆积区构成了一个相对封闭系统.采用质量平衡法,将莺-琼盆地内的堆积物回剥至隆升剥蚀区,重建了中新世以来滇西高原内红河流域区所达到的可能高程.16.2～19.6 Ma前红河流域区海拔高度低于560 m,16.2～11 Ma前的隆升使高程升至860～950 m.经过11～5.3 Ma前的剥蚀夷平后,海拔高度降为800m.距今5.3～1.6 Ma前的快速隆升,使海拔高度曾达到2600～2725 m,隆升幅度达1800～1925 m,滇西高原形成.近1.6 Ma以来则主要是剥蚀削低,海拔高度从2560 m降为2300m.中新世以来红河流域区被剥蚀掉约3900 m.     

Pedogenic carbonate isotope record of vegetational evolution since late Miocene in Loess Plateau

Isotopic analyses for paleovegetational evolution have been carried out on samples of the pedogenic carbonate nodules in the Red Clay-Loess sequence at Lingtai (35°N), the Loess Plateau. Stable carbon isotopic composition indicates that ( i ) C4 plants might be present at least by7.0 Ma; ( ii ) C4 plants expanded gradually between ～4.0 and ～3.2 Ma, and their biomass fraction was up to 50% ; and (Ⅲ ) the biomass of C4 vegetation since ～2.0 Ma seems to have been decreased to the level (about 20%) before 4.0 Ma. C4 plant expansion at Lingtai cannot be fully understood with the "global C4 expansion" model because it occurred much later up to 3.0 Ma than in Pakistan, which indicates that some changes in the regional climatic system may also contribute to C3/C4 shift except changes in atmospheric CO2 concentrations and temperature. The latitudinal zone for C3/C4 transition seems to move southwards slightly in East Asia, compared with the case in North America where 37°N癗 is the ideal boundary for the C4 expansion.     

中古以来舌音开合的演变

从舌音的角度出发,聚焦于开合口的衍化,分隋唐、两宋、金元、明清和现代五个阶段,描绘出汉语语音从中古到现代开合口变化的轨迹,探讨变化的成因,分析成系列发生过开合口变化的10组舌音字,从舌音的角度展示汉语语音演变的详貌。     

柴达木盆地甜参1井砾岩层厚度特征及其青藏高原隆升意义初探

通过对青藏高原北麓柴达木盆地内甜参1井晚新近纪以来的砾岩层特征的研究,并结合砾岩层年代分析,初步探讨了砾岩层反映的青藏高原隆起信息:新近纪晚期青藏高原经历了一系列的隆起阶段,隆起频度较大;早更新世青藏高原处于相对平静的时期,以较短时期的相对隆起;中更新世高原进入强烈隆升时期,尤以晚中更新世和晚更新世的两次隆升强度最大。     

鲁西隆起中-新生代伸展构造演化的模拟试验

通过野外地质调查对鲁西隆起伸展构造特征进行研究,并根据相似理论建立相关试验模型,对鲁西隆起晚中生代以来的伸展构造的发育演化进行构造物理模拟.结果表明:鲁西隆起晚中生代以来的伸展裂陷作用主要经历了晚侏罗-早白垩世、新生代两个阶段,新生代又分为古近纪古新世-始新世初期(65～53 Ma)、早始新世-晚始新世(53～39 Ma)和始新世末期-渐新世(39～23.5 Ma)3个时期,各个时期与研究区伸展构造的主要发育时期相符;物理模拟试验证实泰山在新生代有两次快速抬升,分别为始新世(45 Ma)和渐新世(23 Ma);伸展构造的形成归因于晚中生代和古近纪近南北向大规模的伸展作用,其深部背景主要为晚侏罗世以来太平洋板块俯冲方向及速度的改变、郯庐断裂带的走滑活动、新生代印欧板块的碰撞以及幔源岩浆活动.