Pendleian (early Serpukhovian) marine carbonates from SW Spain: sedimentology,biostratigraphy and depositional model

The San Antonio–La Juliana tectono‐sedimentary unit contains the only Namurian marine carbonates in the southwestern part of the Iberian Peninsula. The analysis of this unit is fundamental in understanding the sedimentary evolution and tectonic movements which operated during the Namurian in this area. Using foraminifera the succession has been assigned to two biozones (Zones 17 and 18), both occurring in the Pendleian (early Namurian). Seven stratigraphic sections have been analysed: San Antonio, Burjadillo, Lavadero de la Mina, Cornuda, Lozana, Caridad and Via Crucis. The stratigraphic succession of the San Antonio–La Juliana Unit consists of olistolites in the basal part, with common debris‐flow deposits (mainly of carbonates, with minor siliciclastic rocks), and turbidites, all of them embedded in shales. These rocks, interpeted as slope deposits, pass up into shallow‐water platform facies, with sediments characteristic of the inner platform and tidal flats. Above these rocks, terrigenous deltaic deposits occur. Thus, the stratigraphic sections show an overall shallowing‐upward trend. The isolation of some outcrops, and the duplication and absence of some parts of the stratigraphic succession are explained by tectonic movements. Overall, tectonic factors seem to be the main control rather than glacio‐eustatic or autocyclic processes, and sedimentation took place in a strike‐slip regime. Copyright © 2004 John Wiley & Sons, Ltd.     

腾冲地块西缘那邦基性麻粒岩中石榴石Sm-Nd等时线年龄及其意义

石榴石 Ｓｍ  Ｎｄ 等时线法是近年来常用于较新年龄的测年方法。腾冲地块西缘新近发现的基性麻粒岩中石榴石和全岩的 Ｓｍ  Ｎｄ 等时线年龄为 １７～２５ Ｍａ, 是该麻粒岩经受后期变形变质作用的年龄, 与区内右旋走滑断裂活动时限相一致,为确证腾冲地区的右旋走滑断裂是印支地块逸出的西部边界提供了 Ｓｍ  Ｎｄ 等时线方法的年龄约束。并推断石榴石 Ｓｍ  Ｎｄ 体系的封闭温度较低, 应低于那邦变质基性岩晚期变质作用的６４０℃～７２０℃。     

GPS动态测量连续周跳检验

本文针对ＧＰＳ动态测量中经常出现的连续周跳,提出了一种新的连续周跳的检验方法。该方法在理论上是最优的,与Ｋａｌｍａｎ滤波平行操作,能够实行处理周跳引起的偏差;而且,在偏差估计的同时,兼顾后续偏差检验,因而可利用尽可能多的观测历元信息来获取精度较高的偏差估值。实例计算表明,该方法在应用中是很有效的。     

Tectonic Evolution of the Lufilian Arc (Central Africa Copper Belt) During Neoproterozoic Pan African Orogenesis

The Lufilian arc of Central Africa (also called Katangan belt or Copperbelt) is a zone of low to highgrade metasedimentary (and subsidiary igneous) rocks of Neoproterozoic age hosting highgrade CuCoU and PbZn mineralizations. The Lufilian arc is located between the Congo and Kalahari cratons and defines a structure which is convex to the north. Three major phases of deformation characterize the construction of the Lufilian arc. The first phase (D1) called the “Kolwezian phase” developed folds and thrust sheets with a northward transport direction. D1 deformation occurred in the Lufilian arc between ca. 800 and 710 Ma, with a peak in the range 790–750 Ma. It is here correlated with the main deformation in the Zambezi belt. Southward-verging folds with the same trends as the D₁ structures were previously linked to a second tectonic event named Kundelunguian phase of the Lufilian orogeny. We show in this paper that they are backfolds developed during D1 along Katangan ramps and especially along the Kibaran foreland. The second phase (D2) of the Lufilian orogeny is the “Monwezi phase” including several large leftlateral strikeslip faults which have been activated successively. During this deformation phase, the eastern block of the belt rotated clockwise, giving the present day NWSE trend of D1 structures in this part of the Lufilian arc, and generating its convex geometry. The Mwembeshi dislocation, the major transcurrent shear zone separating the Zambezi and Lufilian arc, was mostly active during the D2 deformation phase. D2 deformation occurred between ca. 690 and 540 Ma. Such a long time interval is attributed to the migration of strikeslip faults developed sequentially from south to north, and probably to a slow convergence velocity during the collision between the Congo and Kalahari cratons. The third phase (D3) of the Lufilian orogeny is a late event called the “Chilatembo phase”, marked by structures transverse to the trends of the Lufilian arc. This deformation and the post-D_2′ uppermost Kundelungu sequence (Ks3 Plateaux Group), are younger than 540 Ma and probably early Paleozoic.     

天桥沟-黄羊川活动断裂带的几何学和运动学特征

依据１ ：５０ ０００ 地质填图资料,对天桥沟—黄羊川活动断裂带晚更新世以来的几何学和运动学特征进行了详细的论述．认为该断裂带可分为逆走滑（ 左旋） 的天桥沟断裂段和正走滑（ 左旋） 的黄羊川断裂段,其主要活动时期是晚更新世,滑动速率为４ ～５ ｍ ｍ／ａ ．全新世早期,该断裂带活动强度逐渐减弱,其最后一次活动的时间为距今０ ．７５９ ×１０４ ～１ ．０２ ×１０４ 年     

走滑活动断裂带断错冲沟变形角特征及其构造意义初探

阐述了通过走滑活动断裂断错冲沟形成变形角研究冲沟形成年代,进而探讨断裂活动特征的方法。并以天桥沟－黄羊川断裂东段为例,对变形角大小和冲沟形成年代及冲沟水平断错距之间的关系进行了探讨,结果表明它们之间关系密切。最后论述了变形角用于走滑活动断裂研究的可能性及意义。     

蔚广盆地南缘断裂带唐山口段山前断层活动性研究

蔚广盆地是山西地堑系北端京西北盆岭构造区内的一个半地堑盆地,蔚广盆地南缘断裂带为控制该盆地形成的边界断裂。该断裂带位于唐山口段的山前断裂在冲洪积扇体上形成了线性特征显著的断层陡坎。横跨断层陡坎开挖的探槽表明该条山前断裂属于全新世活动断裂,探槽揭示了2条活动断层以及相应的3次古地震事件。在距今约9ka时其中一条断层首次活动,之后在距今约7.3ka时该条断层再次活动并引发了另一条断层的形成与同步活动。最后它们又发生了第三次活动,而最新一次活动的时间由于相应地表沉积的缺失而无法获得。这3次古地震事件的累积垂直位错约为8.1m。估算出整条山前断裂的平均复发周期约为1.7ka、平均滑动速率约为1.6mm/a。此外还依据经验公式估算出了各次古地震的参考震级。     

甘孜-玉树断裂带晚第四纪走滑速率与滑动分解作用

滑动速率是研究断裂运动学特征、地震活动性和区域应变分配的重要参数和依据。前人关于甘孜-玉树断裂带滑动速率的研究结果存在较大差异,因此,其晚第四纪滑动速率有待进一步调查研究。本文基于卫星影像解译和野外实地考察,对甘孜-玉树断裂带西段（玉树断裂）上典型断错地貌点进行测量分析,得到玉树断裂晚第四纪走滑速率为6.6±0.1-7.4±1.2mm/a。通过与前人对甘孜-玉树断裂带东段（甘孜断裂）滑动速率的研究结果进行对比,发现甘孜-玉树断裂带东、西段滑动速率不一致,其原因是甘孜断裂的左旋滑移在向西传递的过程中,一部分应变被分配到了巴塘盆地南缘断裂上。巴塘盆地南缘断裂的存在很好地解释了玉树断裂的走滑速率比甘孜断裂偏低的原因。但是,从区域变形来看,巴塘盆地南缘断裂分配的滑动速率恰好说明了甘孜-玉树断裂带东、西段及鲜水河断裂带的水平构造变形是协调一致的。     

汶川地震震前与同震断层滑移的比较分析

本文利用GPS观测的1999-2007年汶川震前3期地表变形数据和2008年汶川同震地表变形数据,结合地震位错理论,通过高斯变换和坐标旋转建立断层模型,运用遗传算法,反演了龙门山断裂带断层震前3期和同震滑动参数。结果表明龙门山断层震前3期平均走滑位移为-5.39mm,倾向位移为2.66mm,与同震断层滑移相比较,发现震前断层的滑移趋势与同震断层滑移一致,均为逆冲兼右旋的挤压运动。比较震前3期逆冲方向的滑移量,发现逆冲滑移有加速的现象。并根据震前和同震的断层滑动量估算了汶川地震复发周期。     

历史大地震断层滑动模型的建立及其对同震数值计算的影响——以1920年宁夏海原MS8.5大地震为例

大地震的发生会引起区域位移场和应力场发生变化,进而改变区域内及临近断层的应力状态和地震活动性.目前,研究学者可据已有的断层滑动模型来计算分析大地震同震应力变化,同时采用库仑应力触发理论来进一步分析震后余震分布和断层危险性.然而,历史上曾经发生过不少大地震,例如,1920年的海原M_S8.5大地震,是全球范围内少见的特大地震之一.局限于无确切的地震台站地震波等资料,前人在研究历史地震的影响时往往给出一些简单的断层滑动模型,将断层面上错动量视为均匀分布.为更准确地了解历史地震对后续地震的影响,基于前人研究和一般地震滑动形态分布规律及地震反射剖面等资料,以海原M_S8.5大地震为例,探讨了如何建立海原大地震断层滑动模型,并分别搭建了简单断层滑动模型和复杂断层滑动模型的全球同震横向不均匀并行椭球型地球模型.通过对海原M_S8.5地震的同震位移场和应力场的计算,发现采用复杂断层滑动模型比简单断层滑动模型地表位错分布更切合实际.同时,进一步计算和分析了此次大地震对青藏高原东北缘近100年历史地震和周围断层的应力触发作用,得出断层滑动模型对同震计算结果的影响集中在发震断层附近而对远场影响较小.