北京平谷马坊Zk09钻孔新生代地层格架及其地质意义

本文基于北京平谷马坊地区Zk09钻孔新生代地层岩性岩相分析和沉积物古地磁等测试,建立了北京平原泃河水系中下游冲洪积区完整新生代地层格架。其中,0m～180m为中更新世-全新世陆相辫状河和曲流河沉积,180m～240.5m为中新世-上新世残坡积、湖积和三角洲前缘沉积。Zk09钻孔新生代不连续地层揭示了北京平原区两次重要的抬升构造事件：第一期构造事件发生于中新世,而不是前人研究认定的早更新世或上新世末,其最终结束了大渤海湾盆地古近纪盆-岭构造系统演化;第二次构造事件发生于中更新世早期,其可能是目前以走滑运动为主的最新构造变动形式起始时间。     

阿尔金红柳沟—拉配泉混杂岩带中—新生代隆升-剥露的裂变径迹证据

以阿尔金红柳沟—拉配泉混杂岩带中段阿克达坂至喀腊大湾一带的各类岩石为研究对象,通过锆石、磷灰石裂变径迹测年和热史模拟揭示阿尔金红柳沟—拉配泉混杂岩带中生代以来的隆升演化史。分析结果表明,阿尔金红柳沟—拉配泉混杂岩带中生代以来至少经历了5次构造隆升事件：222～186 Ma(晚三叠世到早侏罗世)、144～13 Ma(早白垩世早期)、103～82 Ma(早白垩世晚期到晚白垩世)、45～27 Ma(始新世到渐新世)和22～7 Ma(中新世)。热史模拟结果显示,阿尔金北缘新生代以来隆升具有一定的整体性和区域差异性：新生代初期,阿尔金北缘整体隆升较为缓慢;始新世到渐新世,具有西快东慢的隆升特点;中新世以来,阿尔金山地区发生了一次剧烈的区域隆升事件,该隆升事件在阿尔金红柳沟—拉配泉混杂岩带呈现出起始时间东早西晚的趋势。     

西昆仑山北缘新生代隆升历史的裂变径迹证据

自新生代以来,西昆仑地区发生强烈的构造变形和隆升,其初始隆升和末次快速隆升的时限仍是有待探讨的重大问题。本文沿西昆仑北缘采集一系列砂岩样品,利用裂变径迹分析方法探讨了西昆仑北缘新生代的冷却历史。结合裂变径迹年龄和径迹长度分布进行分析,可以将6个磷灰石样品分为2组。3个磷灰石样品的径迹年龄远小于所在地层的年龄。平均径迹长度为(12.0±2.3)~(12.6±1.3)μm,呈不对称单峰形态,反映样品缓慢地通过部分退火带;另外3个磷灰石样品径迹年龄与各自地层的沉积年龄接近,平均径迹长度介于(10.7±2.3)~(11.4±1.3)μm,呈现双峰或混合分布的特征,表明沉积后发生部分退火。热史模拟显示,自晚白垩世以来,西昆仑山北缘共经历了3期抬升冷却事件。晚始新世(40~30 Ma),受早期印度板块向古亚洲大陆板块俯冲碰撞的影响,西昆仑山北缘已经开始隆升;晚渐新世―早中新世(25~15 Ma)是西昆仑乃至青藏高原重要的隆升时期;最后一轮强烈隆升则发生在距今5~3 Ma以来,冷却速率最高达15℃/Ma,剥蚀速率相当于600m/my。电子自旋共振测试揭示了早中新世(15 Ma)和晚上新世以来(2.6~0.63 Ma)两期强烈的构造变形和热液活动,更进一步限定了西昆仑最后一期强烈隆升在2.6 Ma以来。     

南海深海盆的沉积充填

 依据大洋钻探井及地震剖面资料，定量确定南海同扩张期和后扩张期深海盆沉积充填差异及沉积物来源变化。研究显示，南海深海盆自渐新世（32 Ma）开始形成，随着南海二次扩张海盆范围逐渐扩大，海盆内主要充填火山碎屑角砾岩及火山灰，碳酸盐岩、超微化石软泥，泥质粘土、粉砂质粘土、泥岩及粉细砂岩。深海盆充填主要沉积物为晚中新世（11.6Ma）以来的陆源碎屑沉积，丰富陆源碎屑的供给与南海闭合过程中同期区域构造事件（如青藏高原快速隆升、菲律宾板块俯冲）密切相关，也与晚中新世以来东亚季风增强以及源区强烈的风化剥蚀有关。     

天水盆地古近纪地层年代及其意义

天水盆地位于青藏高原东北缘六盘山与西秦岭二重要构造带交汇处,该盆地充填的新生代沉积序列记录着该区构造变形历史,因此研究该盆地沉积记录对探讨青藏高原东北缘新生代构造活动事件具有重要意义.通过对天水盆地古近纪砾石层砂质透镜体中碎屑颗粒磷灰石裂变径迹热年代学研究,获得样品地层的最大沉积年龄为24.8士1.5 Ma.结合前人的工作,厘定该套古近纪地层最顶部地层年龄为22～24.8 Ma,并确定天水盆地古近纪沉积物源区在24.8 Ma左右发生了构造冷却事件,推断印度板块与欧亚大陆碰撞的远程效应在古近纪末-新近纪初已传递到青藏高原的最东北缘.     

塔里木盆地库车坳陷中、新生代沉降特征探讨

应用回剥分析方法(Backstripping analalysis)选取有代表性的四条剖面地层,计算了库车盆地中、新生代地层的沉降速率和沉积速率,其中构造沉降在早三叠世、早白垩世、上新世分别达到32.45 m/Ma、37.35 m/Ma和59.82 m/Ma的高峰,沉积速率曲线也清楚的揭示了库车盆地在演化过程中沉降速率起伏变化的特点.结合地震剖面上的构造证据以及岩相古地理、古生物化石证据,分析了库车盆地在中生代以来的构造演化过程,认为库车盆地自中生代以来的构造活动经历了挤压,应力松弛,构造伸展,挤压,应力松弛,再挤压等六个构造活动阶段,说明了盆地演化过程中构造活动的阶段性.由盆地的沉降特点、构造的活动性质,分析认为库车盆地是由三叠纪早期的前陆盆地经历了中生代应力松弛、盆地伸展以及晚白垩世的挤压隆升和剥蚀,经过早第三世的海侵,在新生代再次复活,是再生的前陆盆地.     

青藏高原东缘安宁河断裂带中-新生代构造变形及其磁组构特征

安宁河断裂带是青藏高原东缘大型走滑断裂系鲜水河-小江断裂系重要组成部分,演化历史悠久,构造变形复杂。为了进一步理清青藏高原东缘安宁河断裂带中-新生代构造变形,文中通过详细的野外构造观察与解析并结合构造岩磁组构对安宁河断裂带进行精细的构造变形研究,厘定了安宁河断裂中-新生代构造变形序列及其变形特征。结果表明中生代安宁河断裂带先后经历了印支晚期NEE-SWW向挤压作用下的早期具有左行走滑特征的韧性剪切和晚期韧-脆性密集劈理化构造变形过程以及晚中生代近E-W向挤压作用下形成的低角度韧-脆性剪切三期构造变形过程;构造岩磁组构样品的平均磁化率具有强、弱磁化率2种特征,且构造岩具有磁面理较磁线理发育的特征,磁化率椭球体以压扁型为主,构造强应变特征明显;最小磁化率主轴呈NEE-SWW向,即中生代早期的韧脆性变形受到了NEE-SWW向的挤压作用,但运动学分析结果反映出了后期叠加改造的特征。新生代安宁河断裂带整体经历了NWW-SEE向挤压作用下以左行走滑为主的具有自西向东扩展特征的三幕挤压走滑和两幕斜张走滑构造变形过程,奠定了安宁河断裂带现今两堑夹一垒的构造地貌。这为深入认识和恢复川滇南北构造带及其青藏高原东缘的形成演化过程奠定了基础。     

吉隆盆地构造、环境演化与青藏高原隆升

位于喜马拉雅北麓的晚新生代吉隆断陷盆地,在中新世晚期-上新世沉积了总厚约300m的河湖相地层。根据沉积学、碳氧同位素及控盆构造分析,结合已有的古生物学孢粉学资料,恢复了晚新生代盆地构造控制、沉积环境、气候变动及其演变过程;探讨了构造演化和气候变动两者之间的耦合关系;指出盆地由早期半封闭型断陷湖盆,中期开放型湖盆,向后期封闭型湖盆的演化。     

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.     

河北三河上更新统——全新统磁化率变化旋回分析

为了获取河北三河地区上更新统-全新统古气候和古环境变化,在该区实测一地层剖面,采集磁化率样品进行测试,以磁化率变化为沉积环境代用指标,在前人研究确立的地质年代框架下,运用频谱分析、演化谱分析等方法对地层垂向磁化率变化进行旋回分析。结果表明研究区冲积沉积中存在23ka的岁差尺度旋回,由于剖面较短未识别出更长周期的斜率和偏心率旋回。根据分析结果计算出剖面沉积时限为4-45ka,属于晚更新世晚期至全新世早期河流砂坝和泛滥平原沉积,平均沉积速率为24cm/ka。磁化率的变化与粒度变化具有正相关性,粗粒沉积磁化率较高、细粒沉积磁化率较低;磁化率的变化受岁差驱动气候变化影响,岁差高值时大气降水对河流补给增多,陆源碎屑增多提高了沉积物中磁性矿物的含量,反之,则磁性矿物少,磁化率低。岁差驱动气候变化在河流冲积物中的发现,为河流冲积沉积天文驱动气候变化研究提供参考依据,为第四纪冲积沉积和地质事件研究提供新的年龄约束手段。     

Determination of the Altyn Tagh strike-slip fault basin and its relationship with mountains

A special extended basin topography is developed in the middle segment of the Altyn Tagh Fault Zone. The ratio of its length to width is over 50. The long boundaries at the two sides of the basin are controlled by the straight normal faults with strike-slip component. Within the basin, the Cenozoic strata are spread. The Altyn Tagh main fault goes through the basin, and a series of strike-slip topography was formed within the basin. The reverse thrust structures were formed at the two sides of the center of the basin, thus making the geological bodies composed of old metamorphic rocks at the two sides of the basin extrude vertically，and forming the extended massif (mountain) at the sides of the basin and parallel to the basin. This special topography was called the strike-slip fault basin. The giant extended strike-slip fault basin began to form during Pliocene, and its topography was basically formed during the late Pleistocene. It is the special topography formed during the strike-slip deformation process of the Altyn Tagh Fault Zone and under both transpression and uplifting.     

Molecular phylogeny of the specialized schizothoracine fishes （Teleostei： Cyprinidae）,with their implications for the uplift of the Qinghai-Tibetan Plateau

Molecular phylogeny of three genera containing nine species and subspecies of the specialized schizothoracine fishes are investigated based on the complete nucleotide sequence of mitochondrial cytochrome b gene. Meantime relationships between the main cladogenetic events of the specialized schizothoracine fishes and the stepwise uplift of the Qinghai-Tibetan Plateau are also conducted using the molecular clock, which is calibrated by geological isolated events between the upper reaches of the Yellow River and the Qinghai Lake. Results indicated that the specialized schizothoracine fishes are not a monophyly. Five species and subspecies of Ptychobarbus form a monophyly. But three species of Gymnodiptychus do not form a monophyly. Gd.integrigymnatus is a sister taxon of the highly specialized schizothoracine fishes while Gdo pachycheilus has a close relation with Gd. dybowskii, and both of them are as a sister group of Diptychus maculatus. The specialized schizothoracines fishes might have originated during the Miocene(about 10 MaBP), and then the divergence of three genera happened during late Miocene (about 8 MaBP). Their main specialization occurred during the late Pliocene and Pleistocene (3.54-0.42 MaBP). The main cladogenetic events of the specialized schizothoracine fishes are mostly correlated with the geological tectonic events and intensive climate shift happened at 8, 3.6, 2.5 and 1.7 MaBP of the late Cenozoic.Molecular clock data do not support the hypothesis that the Qinghai-Tibetan Plateau uplifted to near present or even higher elevations during the Oligocene or Miocene, and neither in agreement with the view that the plateau uplifting reached only to an altitude of 2000 m during the late Pliocene(about 2.6 MaBP).     

南海生物礁碳酸盐台地演化

 南海碳酸盐台地分布自早中新世开始发育，至中中新世达到鼎盛，再到晚中新世大量台地被淹没而逐渐消亡。从分布看，南海碳酸盐台地具有南早北晚、东早西晚的发育规律；从堆积速率看，中中新统速率最大。控制这些台地的诞生、发育演化和消亡的因素十分复杂，可能包括构造活动、相对海平面的变化、陆源碎屑物质输入变化、古海洋环境变化。     

A Miocene ostrich fossil from Gansu Province,northwest China

A pelvic skeleton, recognized as a large terrestrial bird in the field, was recently collected by our paleomammalo-gist colleagues from the Institute of Vertebrate Paleontol-ogy and Paleoanthropology from the late Miocene sandy mudstones in the Linxia Basin in Gansu Province, north-west China. We have further referred this bird to as an early representative of ostrich. Ostrich fossils usually co-existed with the famous Hipparion Fauna from the Mio-cene to Pliocene. The Linxia Basin is we…     

中新生代天山及其两侧盆地性质与演化

天山两侧中新生代盆地中的沉积记录、沉积中心展布及其迁移特征反映了盆地演化特征,天山地区的年代学数据则是构造活动的响应。这些沉积学记录、年代学记录及山前构造变形与天山地区的构造演化、天山快速隆升和区域地壳缩短相对应,反映晚侏罗世晚期—早白垩世早期、晚新生代是天山快速隆升的2个时期,也是盆地性质发生转变的重要时期。综合分析认为,天山两侧盆地早中侏罗世为陆内断陷坳陷盆地阶段,晚侏罗世—早白垩世早期盆地开始进入挤压背景下的陆内坳陷盆地阶段,晚新生代开始发育再生前陆盆地。天山晚新生代构造变形总体显示西强东弱的特点,这种变形差异可能与帕米尔构造结的向北推挤有关。     

Rapid denudation of the Himalayan orogen in the Nyalam area,southern Tibet,since the Pliocene and implications for tectonics–climate coupling

The Himalayan orogen characterized by very high variability in tectonic and climatic processes,and is thus regarded as a natural laboratory for investigating the coupling of tectonics and climate,as well as the influence of this coupling on geomorphological processes.This study uses apatite fission track(AFT)dating of samples from a45-km-long section crossing the Great Himalaya Crystalline Complex(GHC)in the Nyalam area,southern Tibet,to constrain the timing and rate of late Cenozoic denudation.The AFT ages can be divided into two groups:(1)15–6 Ma,to the north of Nyalam town,for which the bestfit line of elevation-age has a gentle slope of 0.05,and for which a denudation rate of 0.27 mm/a is calculated;and(2)3–1 Ma,south of Nyalam town,for which the best-fit line has a steep slope of 0.64,and for which a denudation rate of 1.32 mm/a is calculated.The whole AFT ages has a positive correlation with sample elevation(i.e.,older ages are found at higher elevations),and the geographical location of the point of inflexion of the two fitted lines corresponds closely to the junction of Poqu River near Nyalam town.By integrating the AFT data with thermotectonic modeling,it can be inferred that the GHC has experienced two different periods of denudation:(1)slow denudation during middle to late Miocene(15–6 Ma)is recorded in the northern part of the GHC;and(2)rapid denudation from the Pliocene to the Pleistocene(3–1 Ma)is recorded in the southern part of the GHC.An abrupt change in denudation rate occurred between the two periods,with the Pliocene–Pleistocene denudation rate being five times higher than that during the Miocene.This abrupt change in denudation rate during Pliocene pervaded the Himalayan orogen,and was roughly synchronous with a marked change in global climate at 4–3 Ma,and intensification of the Asian monsoon.Importantly,the later period of rapid denudation in the study region closely coupled to the mean annual precipitation,while there is no clear evidence for large-scale faulting activity and associated uplift during this period.Therefore,climate(precipitation)is inferred to be the main cause of the rapid denudation of the Himalayan orogen since the Pliocene.     

Late Cenozoic high-resolution magnetostratigraphy in the Kunlun Pass Basin and its implications for the uplift of the northern Tibetan Plateau

The Kunlun Pass Basin, located in the middle of the eastern Kunlun Mountains, received relatively continuous late Cenozoic sediments from the surrounding mountains, archiving great information to understand the deformation and uplift histories of the northern Tibetan Plateau. The Kunlun-Yellow River Movement, identified from the tectonomorphologic and sedimentary evolution of the Kunlun Pass Basin by Cui Zhijiu et al. （1997, 1998）, is roughly coincident with many important global and Plateau climatic and environmental events, becoming a crucial time interval to understand tectonic-climatic interactions. However, the ages used to constrict the events remain great uncertainty. Here, we present the results of detailed magnetostratigraphy of the late Cenozoic sediments in the Kunlun Pass Basin, which show the basin sediments were formed between about 3.6 Ma and 0.5 Ma and the Kunlun-Yellow River Movement occurred at 1.2 to ～0.78 Ma. The lithology, sedimentary facies and lithofacies associations divide the basin into five stages of tectonosedimentary evolution, indicating the northern Tibetan Plateau having experienced five episodes of tectonic uplifts at ～3.6, 2.69-2.58, 1.77, 1.2, 0.87 and ～0.78 Ma since the Pliocene.     

大同盆地晚新生代环境演化特征

大同盆地是一受北东向主干断裂控制的不对称地堑盆地。盆地基底形态控制了晚新生代沉积的厚度、结构和分布规律。大同盆地古湖泊在上新世早期即已存在,并被盆地中部呈北东走向的玄武岩垅岗分隔成南北两部分;由于构造运动和古气候变化的影响,早更新世早期湖泊发育达到全盛期,然后几经扩张与收缩,于晚更新世早期逐惭消亡。河流与湖泊的相互消长在盆地内沉积了一套河湖相地层,其物质来源主要是东北部火山岩和变质岩分布区。