The Major Two-stage Shortening Deformation of the Northern Tibet and Tian Shan Area Since the Latest Oligocene

It seems to be progressively recognized that the stress of the India-Asia convergent front can be transferred rapidly through the southern and central Tibetan lithosphere to the northern Tibet, hence leading to the crustal thickening deformation there during or immediately after the onset of the India-Asia collision（ca.55 Ma）.This study focuses on the late Cenozoic deformation and tectonic uplift of the northern Tibet and Tian Shan area.Detailed compilations of a variety of proxy data from sediments and bedrocks suggest that the northern Tibet and Tian Shan area underwent one stage of approximately synchronous widespread contractile deformation since 25–20 Ma, which seemed to decrease at circa 18 Ma as revealed by low-temperature thermochronological data.The latest Oligocene-early Miocene was also significant basin-forming episodes when many intermontane subbasins began to receive syntectonic sedimentation in the northeastern Tibet.Subsequently, the other phase of compressional deformation began to encroach more widely into the northern Tibet and Tian Shan area in episodic steps or continuously from 16–12 Ma to present.

Deformation Patterns and Shortening Rates in the East Part of the Kalpin Thrust System in the Southwest Tianshan Mountains During the Late Quaternary

Deformation patterns, shortening amounts and rates in the late Quaternary across the Kalpin thrust system have received tittle attention in the past. This paper attempts to discuss them, mainly in the eastern part of the thrust system by doing field investigation along the faults and folds, measuring geomorphic deformation, excavating trenches in several important sites where young alluvial fans were obviously displaced and dating young deposits of alluvial terraces. There are two types of deformation in the surface and near surface for the Kalpin thrust system in the late Quaternary. They are movement of thrust faults on lower angles and bending of young folds. Both kinds of deformation are shown by shortening and uplifting of young geomorphic surfaces. The surface ages of 3 stages are calculated by dating 20 examples using the TL method in the study area and comparing the results of our predecessors on the deposition and incision times of alluvial terraces in the Tianshan mountain which are 100ka B. P., 33 - 18ka B.P. and 6.6 - 8.2ka B.P. respectively for the large-scale deformed alluvial surfaces： T3, T2 and T1 in the Kalpin region. Then, 19 sets of shortening amounts and rates are obtained in 13 sites along 4 rows of anticlines in front of the Kalpin thrust system and Piqiang fold. The shortening amounts and rates show that there are two sections where deformation is stronger than others. The two sections consist of two arcs that are towards the south. The shortening rates near the top of arcs are 1.32mm/a in the west and 1.39mm/a in the east across the thrust system, respectively. In addition, deformation is stronger in the front rows than the rear ones for bifurcate folds.

THE BALANCED CROSS-SECTION AND SHORTENING IN QIANGTANG TERRAIN QINGHAI—TIBET PLATEAU

Geological studies indicate that Qinghai\|Tibet plateau crust has shortened at least 2500km and the thickness was increased to 60～70km in the past 45Ma. Different researchers advocate different views to explain the shortening according to their studies.( Tapponnier,1977;Chang et al,1986;England et al,1986;Murphy,1997;Y.Pan,1999),however it is still unresolved on how much shortening in upper crustal especially in Qiangtang terrain.Qiangtang terrain is located in the center of Qinghai\|Tibet plateau, the tectonic deformation has been resulted from intracontinental convergence and collision of India plate with Eurasian plate.The deformation style of Qiangtang terrain shows east\|west\|trending folds and thrusts which formed in the shallow tectonic level during collisional\|intracontinental period. The folds type is characterized by nonpenetrative\|foliation parallel fold, the hinges have the same trend with the thrusts. These traits are favourable for restoring the balanced cross\|section and measuring the shortening. The balanced reconstruction is based on line balancing on three different stratigraphic sections (A,B and C)across the Northern Qiangtang basin in the area between 85°E and 87°E.The sections are all north\|south\|trending in accordance with the moving direction of thrusts.

Crust Shortening of the Daliangshan Tectonic Zone in the Cenozoic Era and Its Implications

The Daliangshan tectonic zone is a rhombic area to the east of the Anninghe and Zemuhe fault zones in the middle segment of the Xianshuihe-Xiaojiang fault system along the southeast margin of the Qinghai-Xizang （Tibet） Plateau. Since the Cenozoic era, the neotectonic deformation in the Daliangshan tectonic zone has presented not only sinistral slip and reverse faulting along the Daliangshan fault zone, but also proximate SN-trending crust shortening. It is estimated that the average crust shortening in the Daliangshan tectonic zone is 10.9 ± 1.6 km, with a shortening rate of 17.8 ± 2.2% using the method of balanced cross-sections. The crust shortening from folding occurred mainly in the Miocene and the Pliocene periods, lasting no more than 8.6 Ma. Based on this, a crust shortening velocity of 1.3 ± 0.2 mm/a can be estimated. Compared with the left offset along the Daliangshan fault zone, it is recognized that crust shortening by folding plays an important part in transferring crustal deformation southeastward along the Xianshulhe-Xiaojiang fault system.

Cenozoic Stratigraphy Deformation History in the Central and Eastern of Qaidam Basin by the Balance Section Restoration and its Implication

The Qaidam Basin, located in the northern margin of the Qinghai-Tibet Plateau, is a large Mesozoic-Cenozoic basin, and bears huge thick Cenozoic strata. The geologic events of the Indian- Eurasian plate-plate collision since -55 Ma have been well recorded. Based on the latest progress in high-resolution stratigraphy, a technique of balanced section was applied to six pieces of northeast- southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began to shorten deformation nearly synchronous to the early collision, manifesting as a weak compression, the deformation increased significantly during the Middle and Late Eocene, and then weakened slightly and began to accelerate rapidly since the Late Miocene, especially since the Quaternary, reflecting this powerful compressional deformation and rapid uplift of the northern Tibetan Plateau around the Qaidam Basin.

Cenozoic Stratigraphic Deformation History in the Central and Eastern of Qaidam Basin by the Balance Section Restoration and Its Implication

The Qaidam Basin,located in the northern margin of the Qinghai-Tibet Plateau,is a large Mesozoic -Cenozoic basin,and bears huge thick Cenozoic strata.The geologic events of the Indian-Eurasian plate-plate collision since～55 Ma have been well recorded.Based on the latest progress in high-resolution stratigraphy,a technique of balanced section was applied to six pieces of northeast-southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began

应用Ilizarov技术在旋转中心穹顶状截骨治疗青少年股骨远端外翻畸形

目的:探讨应用Ilizarov技术在旋转中心穹顶状截骨治疗青少年股骨远端外翻畸形的疗效。方法:采用回顾性研究分析2016年1月至2020年10月收治并获得完整随访的11例股骨远端外翻畸形患者的临床资料,其中男7例,女4例;右侧6例,左侧5例;年龄10~14岁。在股骨远端畸形处找出成角旋转中心(center of roration of angulation,CORA),以CORA为中点,行穹顶状截骨,根据Ilizarov外固定穿针原则安装环形外固定架,截断股骨远端,即时矫正股骨远端目测下外翻畸形,外固定架固定维持。术后根据双下肢负重全长正侧位X线片提示的下肢力线及长度结果,矫正残余畸形及短缩。结果:11例均得到随访,时间13~25个月,带架时间12~17周。末次随访拍摄双下肢负重全长正侧位X线片测量11例双下肢长度均等长,畸形均矫正。采用美国特种外科医院(Hospital Special Surgery,HSS)评分评价膝关节功能,均为优。结论:应用Ilizarov技术在旋转中心穹顶状截骨治疗青少年股骨远端外翻畸形,术中即时矫正目测下股骨外翻畸形,术后根据双下肢负重正侧位片提示的下肢力线及短缩程度,动态调整矫正残余畸形及短缩,损伤小,恢复快。

Surveying of the deformed terraces and crust shortening rate in the northwestern Tarim Basin

Relief surveying and chronology study were carried out on the deformed river terraces across the Artushi anticline belt in the northwestern Tarim Basin. The crust shortening rate of this anticline belt since late Pleistocene was calculated to be up to 5-6 mm/a. The total crust shortening rate from the northwestern Tarim Basin to southwestern Tianshan since late Pleistocene was estimated to be over 10 mm/a.

Surveying of the deformed terraces and crust shortening rate in the northwestern Tarim Basin: Comment

The paper of Shen et al., entitled "Surveying of the deformed terraces and crust shortening rate in the northwest Tarim Basin", was published in Chinese Science Bulletin (Vol. 46, No. 12). Shen et al. found the deformation of Late Pleistocene to Holocene terraces of the Boguzi River across the Artushi Anticline in the northwest Tarim Basin close to the Pamir, and made level survey and differential GPS measurement, which is of great importance to geodynamics for research on the coupling of Tianshan Mountains uplifting and Tarim Basin depression. But their understanding to the deformation mechanics of terraces and the calculation methods of crustal shortening are open to discussion. Therefore, we discuss it with Shen Jun et al.

酒泉盆地南缘新生代冲断带的变形特征和变形时间

酒泉盆地南缘冲断带具有多层次的逆冲结构,包括浅层的远距离冲断系统、中层的近距离冲断系统和深层的原地冲断系统。远距离冲断系统由奥陶系和志留系构成,局部地区表现为飞来峰;近距离冲断系统由古生界和中生界构成,大部分隐伏在远距离冲断系统之下,局部地带以构造窗的形式出露地表,其变形样式主要为叠瓦状的冲断变形;原地冲断系统隐伏在近距离冲断系统和第四系之下,其南部的变形主要表现为双冲构造或堆垛构造,往NE方向变形逐渐简单,主要表现为断层传播褶皱和断层弯曲褶皱,前锋地带表现为三角带的突起构造。酒泉盆地南缘冲断带的变形是一个具有大缩短量的薄皮冲断系统,旱峡剖面的构造缩短量为52.7 km,缩短率为55.1%。酒泉盆地南缘冲断带的变形时期大致开始于9.0 M a,并以“前展式”向北扩张,变形时间向北变新,前锋断层开始活动时间约为8.3 M a。

中国西南天山山前的晚新生代构造与地震活动

天山是研究现今陆内造山作用及过程、陆内变形、陆内强震及其预测等大陆动力学问题的理想实验场。西南天山和塔里木之间的新生代褶皱 -逆断裂带基本上由一南冲弧形推覆构造系统和一向北反冲的构造系统组成 ,由北而南主要由以下 4个运动学单元组成 :(1)新生代复活的喀拉铁热克山 -天山南脉古生代造山带 ,其快速变形和抬升可能起始于 2 3～ 2 6Ma前 ,持续至 13～ 16Ma前。 (2 )向南逆冲的西南天山前陆薄皮主冲断带 ,包括木兹杜克弧形薄皮推覆体和依柯冲断带 ,前者代表了向南薄皮逆掩的天山型岩系 ,地表主要表现为一系列的飞来峰群 ,在 14Ma前曾有过大规模活动 ,最小缩短量约为 2 0～ 35km ,最小缩短速率约为 1.4～ 2 .7mm a ;后者代表了向南叠瓦状薄皮逆冲推覆的前陆古生代基底 (塔里木地台型沉积岩系 )卷入构造 ,其西段在距今 14Ma时曾有过强烈活动。两者共同组成了一复杂的双重构造 ;新生代地层也卷入变形。 (3)喀什 -阿图什弧形反冲褶皱 -逆断裂带 ,由 3排向北 (天山 )反冲的左阶雁列展布的第四纪地表滑脱褶皱组成 ,仅在大山口以西发育。该构造带形成于距今约 1.4Ma以后。依什拉克喀拉乌尔断裂以南 ,博古孜河剖面的最小缩短速率约为 5 .8mm a ,翁库尔剖面的最小缩短速率约为 8.6mm a。 (4 )塔里木克拉?

青藏高原东北缘临夏盆地晚新生代构造变形及过程

位于青藏高原东北缘的临夏盆地是一个挤压挠曲型的前陆盆地，褶皱和逆冲断裂带自7．8Ma开始由西向东向盆地内部扩展，形成生长地层和生长不整合，代表高原东北部持续的构造变形过程。这种同沉积的构造变形一直持续到大约1．8Ma左右东山组沉积结束，临夏盆地内部强烈褶皱变形，致使东山组及其以下的新生代地层均被卷入褶皱之中（与其上的最老黄河阶地——井沟砾石层为角度不整合接触），拉脊山断裂继续向北东方向扩展，银川背斜最终形成。随后黄河、大夏河出现，开始了发育河流阶地和堆积风成黄土的新阶段。由平衡地质剖面法得到临夏盆地西缘7．8Ma以来总的地壳缩短量为3．2～3．6km，缩短率为0．41～0．46mm／a。如果取从7．8到1．8Ma之间的大约6．0Ma作为临盘夏盆地的构造变形时段，其缩短速率则为0．5～O．6mm／a。从临夏盆地形成和演化过程来看，青藏高原东北缘的构造变形以沿北西西向断裂的逆冲和地壳缩短为主要特征，导致挤压挠曲型前陆盆地的逐渐隆升和消亡，最终使新生代前陆盆地的大部分并入青藏高原东北缘，成为青藏高原的最新组成部分。

西南天山柯坪推覆构造东段晚第四纪变形样式与缩短速率

柯坪推覆构造的变形量和变形速率对于认识中国大陆的地球动力学过程有重要意义,但晚第四纪以来的变形特征与缩短速率是众多研究中的薄弱环节。文中通过大量的野外调查、探槽开挖、变形地貌面实测与阶地堆积物的测年,分析了柯坪推覆构造普昌断裂以东部分的晚第四纪变形样式、变形量和缩短速率。晚第四纪以来,研究区在地表和近地表的变形主要通过2种形式表现出来:低角度逆断层运动和新褶皱的弯曲变形。这些变形主要由最新地貌面的隆升和缩短来实现。研究区存在2个变形强度大的地段,缩短速率西段为1·32mm/a;东段为1·39mm/a。

青藏高原东北缘岩石圈缩短变形——深地震反射剖面再处理提供的证据

青藏高原是由印度板块和亚洲板块于50～60Ma碰撞而形成的全球最高最大的高原,已成为多数国内外学者的共识。然而,关于它的岩石圈变形机制却是长期争论的问题。深地震反射剖面是精细揭示岩石圈结构、分辨变形样式的有效技术。重新处理的松潘地块-西秦岭造山带深地震反射剖面揭示出岩石圈变形的细节,以地壳上部的双重逆冲构造、地壳中部一系列近水平拆离断层的叠置和地壳下部莫霍面的重叠为主要特征,展现出青藏高原东北缘岩石圈变形以缩短变形为主要机制。横向上上千公里展布的大规模左旋走滑的昆仑断层,自地表向下陡倾延伸到地壳中部的叠瓦状逆冲构造之上,在埋深约35km处被近水平的拆离层所截断。本次研究建立的岩石圈垂向构造图也展现出西秦岭造山带与若尔盖盆地岩石圈尺度的构造关系。

晚新生代以来天山南、北麓冲断作用的定量分析

利用地表地质、二维地震和钻、测井资料建立了两条横穿天山南、北麓库车河地区和金钩河—安集海河地区的构造剖面,从几何学和运动学的角度探讨新生代以来不同序次台阶状逆断层及其相关褶皱的叠加过程、以及叠加过程中断层形态、褶皱形态与位移量之间的定量关系。生长地层和生长不整合分析表明,上新世早期(4.2～5Ma)可能是天山南、北麓新生代冲断褶皱的主要形成期,发育自天山内部的台阶状逆断层在向两侧沉积盆地扩展过程中形成多个滑脱面和断坡,断层位移在断坡位置引发褶皱变形,从而形成南北方向背斜带成排分布的构造格局。在天山南麓库车河剖面中,控制库车地区构造变形的三条台阶状逆断层位移量分别为5.7km、6.3km和18km,它们的活动时代由老到新,而位移量却逐渐增大,反映新生代以来天山南麓的冲断作用可能存在一个加速的过程。按上述数值计算,渐新世(23Ma)以来的缩短速率为1.3mm/a,上新世(5.2±0.2Ma)以来的缩短速率为3.6mm/a。在天山北麓金钩河—安集海河剖面中,山前深部楔形体内的断层位移量为16.9km,但只有6km的位移量沿中上侏罗统西山窑组煤层内的滑脱面向北传递至第二排背斜带,而至第三排背斜带,位移量已递减为0.22～0.29km。以上新世早期(4.2～5Ma)作为构造活动时间,计算出该剖面上、下构造层上新世以来的缩短速率为2.6～3.1mm/a和3.8～4.5mm/a,其中下构造层内的山前深部楔形体、霍尔果斯深层背斜和安集海背斜的缩短速率分别为3.9～4.6mm/a、1.2～1.4mm/a和0.04～0.38mm/a,这说明由于断层位移量在向北传递过程中不断被褶皱作用吸收或沿反冲断层向南消减,各排背斜带的变形强度由南向北依次减弱。

大凉山地区新生代地壳缩短及其构造意义

大凉山地区位于青藏高原的东南边缘,具体指鲜水河-小江断裂带中段安宁河断裂带和则木河断裂带以东的菱形地区。新生代以来大凉山地区的新构造运动不仅表现为沿区内大凉山断裂带的左旋走滑和逆冲2种分量的断层运动,还表现为轴向近SN的褶皱缩短。利用平衡剖面方法结合误差分析得出研究区的地壳平均缩短量为(10.9±1.6)km,缩短率为(17.8±2.2)%。研究区发生缩短变形的时间段主要集中在中新世和上新世(12～3.4MaBP),结合地壳缩短量计算出的研究区地壳缩短速率为(1.3±0.2)mm/a。对比沿大凉山断裂带的左旋滑动量,可以看出这种褶皱形式的地壳缩短在沿鲜水河-小江断裂带向SE方向传递左旋位移的过程中起着重要的作用。

口腔正畸托槽研究中微小力值的测量

对直丝弓滑动法中正畸托槽与弓丝之间的动摩擦力,托槽上的转矩和结扎翼产生的变形角进行测量.设计的加载系统体外模拟正畸过程中牙齿的缓慢移动,可使动摩擦力测量更为精确.采用光学方法测量托槽结扎翼在弓丝扭转状态时变形角的变化.转矩的施加和测量用自行设计的转动轮实现.为自动采集数据设计了完整的数据采集系统.实时得出动摩擦力的时程曲线和托槽齿翼变形角随转矩变化的动态曲线.该方法为临床医学托槽质量评价提供了检测手段.该方法也可用于工程中各种微小力值和位移量的测量.

一期延长矫正下肢26cm巨大短缩畸形和骨不连的远期效果

目的 总结一期延长矫正下肢 2 6cm巨大短缩畸形同时治愈骨不连的经验。方法 患者 10岁女孩 ,右股骨短缩 15cm ,同时合并骨不连 ,右胫骨短缩 11cm ,采用股骨粗隆下截骨与胫骨上干骺端截骨、缓慢牵伸逐渐延长肢体 ,同时加压外固定治疗骨不连。术后 5d开始延长 ,1 5mm/2次 /日。结果 经 2 2 3d延长股骨 15cm ,胫骨 11cm ,骨不连同时治愈。未发生神经、血管损伤。术后 9个月X线片显示右股骨及胫骨延长区连续性新骨生长好 ,骨不连愈合 ,13个月两个骨延长区骨性愈合 ,拆除外固定架扶拐行走。 14个月延长区骨髓腔形成 ,术后 18月上学读书。远期信访右肢骨、胫骨延长区域和骨不连处未再发生骨折 ,生活基本自理。结论 本例治疗成功关键因素是截骨延长部位合理设计 ,牵伸延长速度缓慢和骨断端牢稳固定。

青藏高原地壳密度变形带及构造分区

将区域重力场多尺度刻痕分析用于提取青藏高原地壳变形带的信息,可了解高原内地壳变形带从浅到深的变化和平面分布特征,并对青藏高原主要地体的空间分布定位,为岩石圈研究提供地表地质难以取得的新信息.多尺度脊形化系数的图像刻划不同深度平面上的地壳变形带.青藏高原地壳变形带从上到下由细密逐渐变为粗稀型,而且细密型变形区分布的范围逐渐缩小,到下地壳完全消失.从这种情况可以推测,以垂直地面方向上看,地壳变形带应该是树形的,下地壳粗稀型的变形带为树的主干,而中地壳粗稀型的变形带为树的分枝,上地壳的变形带为树枝的小枝杈.上地壳细密型变形分布区反映了与中新生代地壳缩短变形区的范围,下地壳清晰连续的变形带反映了青藏高原的构造骨架.多尺度边界刻痕系数的图像刻画不同深度平面上的地体边界,下地壳的刻痕边界系数与密度剧烈变化带位置吻合;因此,由多尺度刻痕分析划分地体时同时取得地体密度信息.青藏高原内密度较高的地体包括喜马拉雅地体、克什米亚地体、察隅河地体、柴达木地体、巴颜喀拉地体和羌塘地体.柴达木地体、巴颜喀拉地体和羌塘地体是青藏高原中有壳根的核,而密度最高的克什米亚和察隅河地体在大陆碰撞时不易碎裂,对东西两个构造结的形成起了关键作用.

中轴构造带(南段)的变形及缩短速率计算

中轴构造带是欧亚大陆的一个重要的构造带 ,具有地震震中密集分布、重力梯级、岩石圈厚度或结构变异等特点 ,但没有突兀连贯的山链 ,其原因是多地块的大规模走滑活动的抑制。以往对于中轴构造带的宏观运动和块体之间的相对运动研究得比较深入 ,但是对其缩短变形的研究尚有明显欠缺 ,这使得在讨论青藏高原东向运动是任其“自由逃逸”还是有阻挡性约束的问题时缺乏必要的依据。针对此问题 ,笔者以地块的宏观变形与块体内变形的透入程度为切入点 ,通过编绘横切中轴构造带的平衡剖面 ,计算出该带的缩短率为 2 2 .37% 7.4 3% ,中新世以来的平均缩短速率为 3.6 34.4 5mm/a ,并对中轴构造带形成的变形机制进行了初步探讨。提出青藏高原东向运动受阻 ,中轴构造带内块体东向汇聚下 ,上下地壳拆离并呈现出上叠式仰冲褶皱缩短的认识。