Field meeting: Coastal Suffolk Crag weekend, 23-25 April 2004     

R.G. Dixon 《Proceedings of the Geologists' Association. Geologists' Association》2005,116(2):149-160

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晚新生代以来天山南、北麓冲断作用的定量分析   总被引：11，自引：0，他引：11       下载免费PDF全文

管树巍李本亮  何登发汪新 John Suppe 雷刚林 《地质学报》2007,81(6):725-744

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。  相似文献   

北京天竺晚上新世以来植被演替与气候变迁   总被引：4，自引：2，他引：4  

姚轶锋  叶超  寇香玉  徐景先  贾三满  杜乃秋  李承森 《古地理学报》2007,9(1):45-58

研究了北京天竺TZ01钻孔岩心孢粉样品239块，孢粉组合反映了北京天竺晚上新世以来(约3.580 Ma BP)植被演替和气候变迁大致经历了10个发展阶段：(1) 3.580～3.050 Ma BP：以针叶林植被为主，气候寒冷偏湿；(2) 3.050～2.555 Ma BP：植被为落叶阔叶和常绿阔叶混交林-草原类型，该阶段开始升温，但气候较为温暖湿润；(3)2.555～2.300 Ma BP：植被为温凉偏干的疏林草原，湿度开始下降；(4) 2.300～1770 Ma BP：植被类型仍为疏林草原，该阶段温度上升，但幅度并不大，湿度基本不变，气候温凉干爽；(5) 1.770～1.070 Ma BP：植被类型为针阔混交林-草原，气候温暖湿润；(6) 1.070～0.922 Ma BP：植被演替为较暖湿略干的针阔混交林-草原；(7)0.922～0.800 Ma BP：植被为较寒冷干燥的疏林草原，温度降低，降水减少；(8) 0.800～0.650 Ma BP：植被为温暖偏干的以松为主的疏林草原，温度有所上升，但湿度变化较小；(9)0.650～0.160 Ma BP：植被为温凉湿润的针阔叶混交林-草原；(10) 0.160 Ma BP至今：植被以针阔叶混交林-草原为主，前期气候冷湿，后期较为温暖湿润。  相似文献   

Late Tertiary–Quaternary tectonics of the Southern Apennines (Italy): New evidences from the Tyrrhenian slope     

Cesare Caiazzo  Alessandra Ascione  Aldo Cinque 《Tectonophysics》2006,421(1-2):23-51

This paper summarises the results of combined structural and geomorphological investigations we carried out in two key areas, in order to obtain new data on the structure and evolution of the Tyrrhenian slope of the southern Apennines. Analysis by a stress inversion method [Angelier, J., 1994. Fault slip analysis and paleostress reconstruction. In: Continental Deformation. P.L. Hancock Ed., Pergamon Press, Oxford, 53–100] of fault slip data from Mesozoic to Quaternary formations allowed the reconstruction of states of stress at different time intervals. By integrating these data with those deriving from the stratigraphic and morphotectonic records, chronology and timing of the sequence of the deformation events was obtained.The tectonic history of the region can be related to four deformation events. Structures related to the first event, that was dominated by a strike-slip regime with a NW–SE oriented σ1 and was active since Mid–Late Miocene, do not significantly affect the present day landscape, as they were strongly displaced and overprinted by subsequent deformation events and/or deleted by erosion. The second and third events, that may be considered as the main responsible for the morphostructural signature of the region, are comparable with the stretching phases recognised offshore and considered to be responsible for the opening and widening of the Tyrrhenian basin. In particular, the second event (with an E–W oriented σ3), took place in the Late Miocene/earliest Pliocene and was first dominated by a strike-slip regime, that was also responsible for thrusting and folding. Since Late Pliocene, it was dominated by an extensional regime that created large vertical offsets along N–S to NW–SE trending faults. The third event, that was dominated by extension with a NW–SE oriented σ3, started in the Early Pleistocene and was responsible for formation of the horst-and-graben structure with NE–SW trend that characterises the Tyrrhenian margin of the southern Apennines. The fourth deformation event, which is characterised by an extensional regime with a NE–SW trending σ3, started in the late Middle Pleistocene and is currently active.  相似文献   

滇西新近纪植物气孔、碳同位素组成与古环境分析   总被引：1，自引：1，他引：1  

解三平  孙柏年  阎德飞  丛培允  肖良  韦利杰 《沉积学报》2006,24(6):883-888

对滇西腾冲新近纪两种被子植物叶片及其现存对应种的气孔参数和碳同位素组成的综合分析表明:当时的大气CO2浓度略高于现在水平;化石种的碳同位素分馏值高于现存对应种,但水分利用效率低于现存对应种;这证明当时的气候条件比当前更为温暖湿润。受新生代全球气候变冷和喜马拉雅运动的影响,该盆地一方面受印度洋季风的影响增强,干湿季节交替明显;另一方面受地形地貌影响,沿袭了温暖湿润的气候条件。   相似文献   

Plio-Pleistocene climatic transition and the lifting of the Teton Range, Wyoming     

Estella B. Leopold  Gengwu Liu  David W. Love 《Quaternary Research》2007,67(1):1-11

Fine-grained lacustrine, riverine and ash-fall sediments of the Shooting Iron Formation, whose late Pliocene age is established by Blancan gastropods and vertebrates, yield a pollen flora that is essentially similar in composition to the modern pollen rain in the Jackson Hole area. The Pliocene assemblage suggests a climate like that of the Jackson valley and foothills today. These spectra also resemble a Pliocene pollen flora from Yellowstone Park dated at ∼ 2.02 Ma. However, the underlying Miocene Teewinot sediments differ by containing pollen of four exotic deciduous hardwoods (Tertiary relicts) that suggest a summer-moist climate, unlike that of today. The Shooting Iron sediments lie with an angular unconformity on and above the Miocene lake sediments of the Teewinot Formation. Both of these deposits probably preceded the main uplift of the Teton Range based on the absence of Precambrian clasts in the Tertiary valley deposits. Because the Pliocene floras were modern in aspect, a Plio-Pleistocene transition would be floristically imperceptible here. The sequence denotes a protracted period of relative stability of climate during Teewinot time, and a shift in vegetational state (summer-wet trees drop out) sometime between the latest Miocene and latest Pliocene. The Pliocene spectra suggest a dry, cooler climate toward the end of Shooting Iron time.  相似文献   

西藏札达盆地上新统古格组和托林组的厘定与层序地层划分     

朱大岗孟宪刚  邵兆刚杨朝斌韩建恩  余佳雷伟志  孟庆伟吕荣平 《地质通报》2007,26(8):984-995

根据札达盆地剖面中地层的接触关系、沉积旋回、沉积体系和岩相岩性特征,可将上新统河湖相地层划分为2个组、5个沉积相、8个岩段。古格组(N22g)一岩段为砾岩,属河流相沉积;二、三、五岩段以细碎屑岩为主,属浅湖相沉积;四岩段以含粘土质细碎屑岩为主,属深湖相沉积。托林组(N21t)一、二、三岩段为一套砾岩、含砾中粗粒钙质长石岩屑砂岩和中细粒砂岩的碎屑岩,为典型冲(洪)积扇沉积物。ESR法和古地磁法测年结果表明,古格组形成时代为上新世晚期(4.40～2.47Ma);托林组形成时代为上新世早期(5.44～4.40Ma)。札达盆地为一同生断陷盆地,在上新世时期的构造运动过程中,盆地演化经历了水进体系域—湖泊扩张体系域—湖泊收缩体系域3个发展阶段。  相似文献   

Statistics of sediment mass in the South China Sea: Method and results     

Huang Wei  Wang Pinxian 《Frontiers of Earth Science》2007,1(1):88-96

Sediment mass volumes for periods since the Oligocene (E₃, N₁ ¹, N₁ ², N₁ ³, N₂, and Q) in the South China Sea (SCS) were calculated on the basis of geological and geophysical data including ODP borehole data. Above the pre-Oligocene base, the estimated sediment volume is 7.01 × 10⁶ km³ and the mass is 1.44 × 10¹⁶ t for the entire SCS, with an average sedimentation rate of 6.22 cm/ka and accumulation rate of 12.8 g/(cm²·ka) since the Oligocene. Most of the sediment was deposited on the continent shelf and slope, while only 5% of the total mass accumulated in the Central Basin. Sediment basins on shelf and slope occupy 34% of the entire SCS area bounded by the 2 000 m thickness contour, but receive more than 82% of the total sediment mass, indicating that sediment basins played a central role of sedimentary process in the SCS. The highest sedimentation rate and the largest mass volume occurred in the Oligocene SCS, which is quite different from global sedimentation rate patterns. Therefore, we conclude that deposition in marginal seas was primarily controlled by local tectonics. Translated from Advances in Earth Science, 2006, 21(5): 465–473 [译自: 地球科学进展]  相似文献   

东营凹陷东辛2-4井上新世至全新世天文地层研究     

YAO Yi-min )  XU Dao-yi )  ZHANG Hai-feng )  HAN Yan-ben )  ZHANG Shou-peng )  YIN Zhi-qiang )  HE Qing-fang )  BIAN Xue-mei ) ) Geological Scientific Research Institute of Shengli Oilfield Company  SINOPEC  Dongying    ) Institute of Geology  China Earthquake Administration  Beijing    ) National Astronomical Observatories  Chinese Academy of Sciences  Beijing 《地层学杂志》2007,(Z2)

东辛2-4井钻取岩芯0—530.1m,明化镇组上段的上亚段至平原组划分为18个层,其中,下更新统平原组一段(简称平一段)的底作为第四系下界;同时进行了古地磁研究,测定出布容、松山、高斯和吉尔伯特等4个极性时。由于天文地层研究的需要,对90年代古地磁的年龄与"国际地层表"(2004)对比,作了相应调整,确定井深242.5m处的年龄为781ka,274.5m处的为2581ka,452.0m处的为3596ka和529.5m处的为4493ka,井深242.5m和452.0m这两个界线的年龄值作为天文地层计时的标定。研究大致分为两步:①以磁化强度(MI)数值曲线的频谱和小波分析,选定平原组一段102.4m周期和明化镇组上段68.36m周期分别对应于天文偏心率404ka旋回,求出了堆积速率为0.1584mm/a和0.1692mm/a及其他各层位的年龄:井深274.5m处上新统明上(上)亚段顶界的年龄为2546ka,平一段底界的年龄是970ka,不整合的延续时间大约为1.6Myr。②推测明上(上)亚段顶2546—1806ka期间可能沉积了129m地层;而在1806—908ka期间,由于构造活动上升,把原沉积又剥蚀掉了,形成井深274.5m处的一个大的不整合面,对储层孔隙的扩张和压实有重要影响,成为最后二次烃源物质的卸载和封堵。  相似文献   

西藏札达盆地晚上新世古植被型分析   总被引：4，自引：0，他引：4       下载免费PDF全文

李建国  周勇 《古地理学报》2002,4(1):52-58

札达盆地晚上新世生长着以高山荒漠小灌木、草原、亚高山常绿针叶林和中低山常绿针叶林为主的植被。气候显示了从干旱寒冷至温暖湿润的垂向分异，总体偏于干、寒，属亚热带高山或亚高山类型。当时区内海拔已较高，南低北高的地势特征也已形成。古植被重建及现青藏高原的植被调查资料表明，当时盆地最低处的海拔可能不会超过2 500 m，其周围及北部可能存在海拔4 000 m的高地或更高的山峰。中、晚上新世迄今，该地区隆升的高度的可能不会超过1千米，幅度较喜马拉雅山中部地区小。  相似文献