汾河裂谷晋中盆地内第四纪沉积序列与沉积环境恢复

晋中盆地是位于汾渭地堑系中部的新生代陆内断陷沉积盆地,研究晋中盆地第四纪的沉积序列对于进一步认识该盆地区域构造和区域气候环境变化具有重要意义。为查明晋中盆地第四纪沉积序列结构、研究揭示晋中盆地第四纪沉积环境及演化,通过构造岩相学方法,对晋中盆地地表和钻孔内第四纪沉积物和沉积环境进行了研究。结果表明：晋中盆地清徐地区地表第四纪沉积序列结构为盆地内部沱阳组河床相和河漫滩相-盆地边缘汾河组河流相—盆山过渡带峙峪组河流相、汾河组冲积扇相及马兰组风积相-基岩山地（盆地外围）二叠系浅海相。钻孔岩芯内第四纪沉积序列结构为下更新统浅湖相和滨湖相—中更新统浅湖相和河流相—上更新统河流相和冲积扇相—全新统冲积扇相。研究认为晋中新生代陆内断陷盆地内沉积序列和演化结构为早更新世陆相湖盆沉积环境—中更新世萎缩湖泊环境—晚更新世强烈萎缩的湖泊和河流环境—全新世再度沉降的陆相湖盆;陆相湖盆从中心向山地沉积环境分带为湖泊沉积环境—河流和湖泊沉积环境—冲积扇沉积环境（盆地边缘出山口区）。盆山过渡带地区上更新世沉积物错位现象与同沉积活动断裂有关,断裂活动性揭示了晋中盆地阶梯式断陷成盆的动力学机制。这些研究成果为区域气候环境变化和晋中盆地区域构造研究提供了新证据,也为太原市城市群建设中工程场址的选择提了供参考。     

中国第四系研究中的几个问题

在第四系地层典着手编写之际,本文对第四系研究的一些基本问题进行了讨论。第四系长期以来的“四分”及相应的符号,将下、中、上更新亚统与全新统并列而应废止;且由于全新统资料已很丰富,可以再予细划分,则在取Q_p和Q_h作更新统和全新统代号后,再行划分,并在其右上角做亚统标记。从多重标准划分地层后,为求得国际可使用的对比基础,应尽量使用时间标尺。西部依构造期划分的地层,未能精确地确定地质时代,除非对构造期及相应地层做测年,否则,与东部沉降地区地层对比将有很多困难。应严格组的内容、概念、延伸性的研究。     

固城湖晚全新世以来的孢粉组合及环境变迁

本文依据固城湖GD钻孔系统的孢粉分析资料,将井深6.3m岩心所做的孢粉图式,结合~(14)C测年,从下面上分为8个孢粉组合带,进而论述了4000年来该区的植被发展和气候的4次冷暖交替的变化。4次冷期约为3.0—2.5KaB.P.2.0—1.5KaB.P.、1.0—0.8KaB.P.和0.4Ka以来。此外,还根据沉积物中的硅藻分析、有机质δ~(13)C值、有机碳含量及历史记载等资料,侧重讨论了气候及人类活动对湖泊环境演变的影响。     

The recent fault scarps of the Western Alps (France): Tectonic surface ruptures or gravitational sackung scarps? A combined mapping, geomorphic, levelling, and Be dating approach

In the Western Alps, some recent scarps were previously interpreted as surface ruptures of tectonic reverse and normal faults that agree with microseismicity and GPS measurements. Our analysis shows that in fact there are hundreds of recent scarps, up to 30 m high and 2.1 km long, with only pure normal motions. They share the same characteristics as typical sackung scarps. The scarps are mainly uphill facing, parallel to the ridge crests and the contour lines. They are relatively short (less than 2.1 km) with respect to tectonic fault ruptures, and organized in swarms. They cut screes and relict rock glaciers with a slow (commonly 1 mm/year) average slip rate. In the Aiguilles Grives massif these sackung scarps clearly express the gravitational toppling of sub-vertical bedding planes in hard rocks. In contrast, the Belledonne Outer Crystalline Massif exhibits scarps that stem from the gravitational reactivation of conjugate tectonic faults. The recent faults extend to about 1600 m beneath the Rognier ridge crest, but are always above the valley floor. The main scarp swarm is 9.2 km long and constitutes the largest sackung ever described in the Western Alps. ¹⁰Be dating of a scarp and offset surfaces shows that > 4 m slip may have occurred rapidly (in less than 3800 years) sometimes between the end of the glaciation and 8800 ± 1900 years ago. This dating, together with the location of some faults far from the deep glacial valleys, suggests that sagging might have been triggered by strong earthquakes during a post-glacial period of probably enhanced seismicity. The Belledonne and Synclinal Median faults (just beneath the Rognier sackung) could have been the sources of this seismicity.     

Evolution of an incised valley system in the southern Adriatic Sea (Apulian margin): an onshore–offshore correlation

Seismic surveys with sub‐bottom profiler were carried out in the Manfredonia Gulf in the southern Adriatic Sea. Here, a buried surface was recognized on which three valleys, located about 80 km from the shelf edge, were deeply incised. Beneath this surface, a pre‐upper Würm seismic unit (PW) was identified. Above, two seismic units were recognized: the transgressive system tract (TST) and highstand system tract (g₂)_. On the basis of regional correlation with onshore and offshore data, these units and their boundaries were dated and correlated with phases of the last glacial–interglacial cycle. The incised valley system was attributed to the Marine Isotopic Stage (MIS) 2. The TST and g₂ units fill the valleys and were attributed to the post‐glacial sea‐level rise and highstand. The incised valleys are anomalous with respect to published models; despite having many characteristics that would have limited the fluvial incision (the lowstand shoreline that remained on the shelf, the low gradient of the shelf, the subsidence that affected the study area since MIS 5), the valleys appear to be deeply incised on the shelf, with valley flanks that can exceed 40 m in height. The model to explain the formation of the valleys comprises enhanced river discharge as the key factor in increasing river energy and promoting erosion across the low gradient shelf. Copyright © 2014 John Wiley & Sons, Ltd.     

长春郊区红嘴子发现哺乳动物化石和旧石器

在红嘴子首次发现猛犸象等哺乳动物化石和石核、石片及刮削器等旧石器。其中刮削器为目前吉林省境内发现最好的两刃刮削器。旧石器和猛犸象等哺乳动物化石一起出土,表明其地质时代为晚更新世,文化时代为旧石器时代晚期。该发现证明早在1～4万年前长春地区就有古人类活动。为在该区寻找古人类化石和古文化遗存提供了佐证,对研究当地第四纪气候、古地理也有一定的意义。     

遥感技术在新生代水文地质调查中的应用：以喀喇昆仑山温泉幅1∶25万区域水文地质调查为例

以ETM+遥感数据为主要遥感信息源,应用遥感技术对喀喇昆仑山温泉地区进行1∶25万图幅的水文地质调查。根据地质体的影像特征并与前人地质填图结果对比,建立了遥感解译标志。重点对新生代地层及与水文地质有关的要素等进行解译,编制1∶25万新生代遥感解译图。根据遥感图像对研究区的第四纪沉积物的成因类型和分布范围、地貌特征及河流、湖泊、泉群、地下水溢出带、湿地等水文地质特征进行了研究。基于区内地下水形成环境的差异,地下水资源体系可以分为南部河谷冲积层地下水系统和北部内流湖盆地下水系统。总结地下水的分布特征认为,南部冲积层储水条件较为优越,且补给充分,其地下水与地表水构成一个统一的水资源系统;北部内流湖盆地区多为湖相沉积,受气象因素制约,山前巨大的冲洪积扇存在丰富的地下水外,地下水资源总体贫乏。遥感水文地质调查表明,遥感技术在高原区域填图与水文地质调查中具有高效率低成本的优点,可以在青藏高原水文地质调查中发挥重要作用。     

柴达木盆地第四纪环境演变、构造变形与青藏高原隆升的关系

青藏高原北部柴达木盆地发育了巨厚的第四纪河湖相沉积。盆内沉积地层强烈的构造变形以及湖盆环境突变进一步证实了青藏高原经历了多期挤压隆升运动。沉积环境、介形虫和植物孢粉化石及磁性地层研究表明,自距今 2.5Ma以来,青藏高原共经历了距今2.52～2.28Ma,1.94～1.66Ma,1.38～1.1Ma,0.71～0.5Ma和 0.24～0.09Ma 5次强烈的隆升阶段,分别对应于青藏运动B幕和C幕、昆黄运动A幕和B幕以及共和运动。高原内、外 9个盆地的构造—沉积记录对比研究也进一步揭示了青藏高原隆起的整体性和阶段性。     

Late Quaternary uplift and subsidence of the west coast of Tanna,south Vanuatu,southwest Pacific: U–Th ages of raised coral reefs in the Median Sedimentary Basin

An X‐ray determinative curve, based on the parameter (Smith &; Gay, 1958) has been derived from twelve analysd plagioclases in the range An₆₂‐₈₇. The line differs from previous calibrations of against anorthite content, and it is suggested that this is due to the differing thermal histories of the materials used.

A break in slope in the determinative line at about An₇₅ may correspond to the change in lattice type from low intermediate plagioclase, to “body centred” anorthite. Heating of the plagioclases results in an increase in and the disappearance of the discontinuity.     

海原、六盘山断裂带至银川断陷第四纪构造应力场分析

利用断层滑动资料反演构造应力张量从而确定出海原、六盘山断裂带至银川断陷的第四纪两期构造应力场 :早更新世末期以前 ,为北东—南西挤压型构造应力场 ,由此造成该地区断裂活动主要以逆断为主 ;早更新世末期至中更新世以后 ,构造应力场发生了调整 ,主压应力方向由早期的北东—南西改变为北东东—南西西 ,应力结构由挤压型转变为走滑型 ,并导致断裂活动由早期的逆断为主变为走滑为主 ,这种应力场格局一直持续至今。研究区现代构造应力场可划分为 :海原断裂带走滑应力区、六盘山逆断 -走滑混合应力区和银川断陷拉张应力区