Climate sensitivity to changes in land surface characteristics

Using a recently developed global vegetation distribution, topography, and shorelines for the Early Eocene in conjunction with the Genesis version 2.0 climate model, we investigate the influences that these new boundary conditions have on global climate. Global mean climate changes little in response to the subtle changes we made; differences in mean annual and seasonal surface temperatures over northern and southern hemispheric land, respectively, are on the order of 0.5°C. In contrast, and perhaps more importantly, continental scale climate exhibits significant responses. Increased peak elevations and topographic detail result in larger amplitude planetary 4 mm/day and decreases by 7–9 mm/day in the proto Himalayan region. Surface temperatures change by up to 18°C as a direct result of elevation modifications. Increased leaf area index (LAI), as a result of altered vegetation distributions, reduces temperatures by up to 6°C. Decreasing the size of the Mississippi embayment decreases inland precipitation by 1–2 mm/day. These climate responses to increased accuracy in boundary conditions indicate that “improved” boundary conditions may play an important role in producing modeled paleoclimates that approach the proxy data more closely.     

羌塘盆地查郎拉地区中、新生代地质构造特征

本文系统研究了羌塘盆地查郎拉地区中、新生代的构造特征,将整个研究区划分为五个构造单元。即那日－ 破曲褶皱带、江达－ 杜日断褶带、塞仁那来－ 巴陇复式向斜断褶带、气相错－ 查巴断陷带、查曲公玛－ 日昂巴山间盆地。从晚三叠世以来,图幅内经历了印支期、燕山期、喜山期构造运动,印支期主要是在图幅北部上三叠统地层中形成北东向褶皱,燕山运动早期本区构造活动最为强烈,形成了全区范围内的东西向褶皱和断层,其中尤以南部塞仁那来－ 巴陇复式向斜断褶带最为强烈,构造最为紧密,燕山晚期,以断陷构造为主,形成中部的查曲公玛－ 日昂巴山间盆地和南部的气相错－ 查巴断陷带,喜山期主要是形成一些新构造活动。     

�������ط���GPS�߳�ת���е�Ӧ��

?????????????????????????У????????????????????Щ???????ù???????????????????α仯??????????????GPS??????????????????????÷????????????????GPS?????????????????????????????     

辽西医巫闾山地区中生代两期韧性变形的研究

医巫闾山地区的韧性剪切构造是中生代两期韧性变形作用的产物。早期韧性变形中a线理发育,线理走向和糜棱面理走向基本一致,线理在xy面上的侧伏角绝大多数<30°;该期韧性变形是以左行走滑运动为主。晚期韧性变形中a线理发育,线理倾伏向和糜棱岩中糜棱面理倾向相近,线理在xy面上侧伏角主要在45°～90°之间;该期韧性变形是伸展作用的产物。医巫闾山中生代两期韧性剪切变形作用表明,在侏罗纪至早白垩世期间辽西地区不仅发生了强烈挤压推覆作用和伸展作用,也发生了大规模左行走滑作用。该韧性变形作用的发现对进一步研究辽西中生代的构造演化序列、期次和构造格架转换等问题有重要意义。     

135~130 Ma: 大别山第二次“去根”时间？

大别杂岩主要由早白垩世侵入岩和三叠纪变质岩组成。它的四周是四条区域性韧性剪切带:郯城—庐江断裂,商城—麻城断裂,襄樊—广济断裂和晓天—磨子潭断裂。其中,晓天—磨子潭断裂和襄樊—广济断裂在早白垩世具有相反的走滑剪切方向:北侧的边界断裂(晓天—磨子潭断裂)是一个左行剪切断裂,而南侧的边界断裂(襄樊—广济断裂)是一个右行剪切断裂。在大别杂岩内部,早白垩世低角度剪切面理的倾伏向以SE向或NW向为主。这些晚期剪切面理上的拉伸线理的倾伏向同样为SE或NW向。大别杂岩总体具有朝SE向挤出和顶部相对朝NW向剪切的构造特征。这些表明晚中生代是该杂岩演化的重要阶段。该杂岩的边界断裂和内部构造特征指示其晚期抬升是沿造山带方向(SE—NW)以低角度方式进行的。这一过程直接导致高压-超高压变质岩和同构造岩浆岩被抬升至近地表。同时,年代学研究表明:大别杂岩(扬子板块东北缘地壳)在晚侏罗世—早白垩世经历大规模混合岩化的时间为145~135 Ma,同造山岩浆作用的时间为145~135 Ma,后造山火山-岩浆活动的时间为135~120 Ma。因此,该杂岩中三叠纪高压-超高压变质岩所记录的早白垩世抬升过程不是印支事件的后续,而是燕山期陆内造山及随后发生的伸展过程有关。尽管这一陆内造山事件的起始时间至今仍不确定,但大别山未变形岩体(130~120 Ma)的年代学研究结果和我们新测得的同构造伟晶岩脉的锆石U-Pb年龄(130 Ma)为早白垩地壳变形提供了良好的上限制约。这样,大别山经历了三叠纪碰撞造山和伸展,晚侏罗世—早白垩世陆内造山-伸展二次过程。     

唐山7.8级地震前的震中迁移与远台前兆的关系

以震中迁移始发点的前兆讨论了唐山7.8级地震震中位置的预测,并以此为例分析了汶川8级地震和芦山7级地震的前兆问题。另外,从震中迁移延长线上的前兆来讨论了唐山大震的发生时间。     

秦岭造山带新生代构造隆升与区域环境效应研究

据沉积，构造、地貌并结合地球物理资料综合研究认为，秦岭造山带新生代构造隆升是在中生代白垩纪晚期构造隆升基础上，于晚第三纪中新世迅速隆升，而早更新世早期则是新构造活动最强烈时期。秦岭造山带的新生代构造隆升的方式主要有地垒式、掀斜式、振荡式和翘板式4种。诱发这一地区新构造抬升的主要原因和动力学机制是华北地块自北而南，扬子地块自南而北相向向秦岭造山带之下陆内俯冲和秦岭地块深部软流圈抬升共同作用所致。     

Internal deformation of Sikhote Alin volcanic belt, far eastern Russia: Paleocene paleomagnetic results

We present paleomagnetic results of Paleocene welded tuffs of the 53–50 Ma Bogopol Group from the northern region (46°N, 137°E) of the Sikhote Alin volcanic belt. Characteristic paleomagnetic directions with high unblocking temperature components above 560 °C were isolated from all the sites. A tilt-corrected mean paleomagnetic direction from the northern region is D=345.8°, I=49.9°, α₉₅=14.6° (N=9). The reliability of the magnetization is ascertained through the presence of normal and reversed polarities. The mean paleomagnetic direction from the northern region of the Sikhote Alin volcanic belt reflects a counterclockwise rotation of 29° from the Paleocene mean paleomagnetic direction expected from its southern region. The counterclockwise rotation of 25° is suggested from the paleomagnetic data of the Kisin Group that underlies the Bogopol Group. These results establish that internal tectonic deformation occurred within the Sikhote Alin volcanic belt over the past 50 Ma. The northern region from 44.6° to 46.0°N in the Sikhote Alin volcanic belt was subjected to counterclockwise rotational motion through 29±17° with respect to the southern region. The tectonic rotation of the northern region is ascribable to relative motion between the Zhuravlevka terrane and the Olginsk–Taukhinsk terranes that compose the basements of the Sikhote Alin volcanic belt.     

北京云蒙山地区花岗岩穹隆及伸展构造的探讨

北京云蒙山花岗岩为一中生代侵入的花岗岩穹隆,花岗岩穹隆的叶理普遍发育,叶理轨迹基本平行于穹隆的外部边界,并显示出从核部到边部逐渐增强,东南侧明显强于西北侧的特点。变形构造研究显示,花岗岩穹隆的边部及围岩中普遍存在不同层次及不同运动方向的伸展构造。东南侧以具河防口－水峪伸展型韧性剪切带为特征,剪切运动标志显示为从ＮＷ－ＳＥ的正剪切运动,有限应变分析估算其剪切位移量在１０ｋｍ以上,剪切带上部被河防口正     

Die Rheingrabenrandverwerfung im Wattkopftunnel bei Ettlingen (Nordschwarzwald)

The Wattkopftunnel, near Ettlingen (Nordschwarzwald), drives through the eastern margin of the Rheingraben. The tunnel passes cenozoic and mesozoic sediments. Early quarternary and tertiary beds are situated west of the main thrust of the Rheingraben. Fossil record indicates upper Oligocene age (Chatt) for parts of the tertiary sediments. At the eastern border of the Rheingraben, wedges of jurassic and middle triassic series are squeezed. East of the Rheingraben the tunnel drives in the lower triassic Bausandstein. The eastern margin of the Rheingraben was investigated in detail during tunneling. Faults of the Rheingraben margin are distributed in an 130 meter wide fault zone in the tunnel. Total stratigraphic separation by the normal faults reaches more than 2 000 meters. The cenozoic sequence suffered synsedimentary to early diagenetic deformation, while the mesozoic series are characterized by ruptural deformation. The fault- and joint system is directed in the rheinische Richtung (SSW-NNE). East of the Rheingraben a second direction occur, running parallel to the lower Albtal (W-E).