闽江水利工程引发的环境地质灾害问题初步研究

闽江干-支流上众多水利水电工程的建设运营,显著地改变了闽江干-支流的流速、流量、输砂量和挟砂能力等水动力场因素,也改变了沿江两岸的应力场强度与分布状态,导致闽江流水地质作用类型、强度及其时空分布与演化状态产生较大的变化,相伴产生日益突出的空间分布较广的、持续时间长的沿江两岸(含库区)的环境地质灾害问题。本文概要地就闽江水利工程建设运营与沿江及库区岸坡的失稳破坏危害、水口水库诱发地震灾害以及水利工程运营与水库下游河道稳定性变化及危害的关系等3方面问题进行初步的研究。研究表明:沿江库区及岸坡的失稳破坏灾害发生与水利工程运营具有明显的相关性,随运营时间的延续,灾害发生的频率显著提高; 水库蓄水拦砂致使大坝下游河床的流水侵蚀冲刷作用增强,这是导致水库下游河道形态变化、破坏并伴生沿江岸工程危害的重要因素; 水口水库蓄水加载及水化作用是诱发水口库区地震的重要因素,该水库诱发地震的余震时间持续长,在未来若干年内仍存在发生起伏性增强,或强度较大的并具破坏性地震的可能,对此应予高度重视并展开专项研究。同时提出,应开展水利工程引发的地质灾害的专项监测和预报分析研究,并建立水利工程环境地质灾害动态区域信息监测和预警预报系统。     

贵州开阳地区澄江组第二段砂岩粒度分析与沉积环境

对开阳地区金中背斜及翁昭地区澄江组第二段砂岩的进行了粒度分析,得出了其粒度参数特征。以粒度参数为基础,根据萨胡粒度判别函数、离散图解及粒度概率累积曲线及Sr/Ba测试分析,显示其沉积环境为河流相沉积。结合砂岩岩石学特征综合判断金中地区为辫状河沉积而翁昭地区为曲流河沉积。整体证实了贵州南华系澄江晚期古地理格局为北西高,南东低的特征。     

基于无人机航测的天景山断裂孟家湾地貌精细解译及活动构造定量参数提取

利用无人机摄影测量技术航测天景山断裂孟家湾的地表地形地貌数据,以获取的数字高程模型为基础,通过构造地貌精细解译进一步提取地震断层的水平位移量及垂直位错量,计算断层的平均水平滑动速率,并分析判识了古地震事件。结果表明:①研究区发育3期河流阶地T₃、T₂、T₁,且均被断错,最新的冲沟T₀未见错动;②在T₁阶地面上提取水平位移量为(7.77±0.98)m,计算得到全新世中期以来的平均水平滑动速率为0.86~0.91 mm/a;③在T₁阶地面上跨陡坎提取垂直位错量为(0.61±0.11)m,其坡度存在2个明显拐点,代表2次地表破裂型地震事件,推测在12000 a前,即晚更新世末期或全新世初期以来至少发生过2次地表破裂型地震。     

The impact of agriculture on solute and suspended sediment load on a Mediterranean watershed after intense rainstorms

The solute and suspended‐sediment load following five rainstorms (2005–2007) with varied intensities were studied at the Vernegà experimental watershed, north‐western Spain. Two land‐use areas are located within this watershed, the upstream one (forest) with 160 ha a 100% forested area, and the downstream one (agricultural) with 97 ha being 9 ha conventional agricultural field and 88 ha forest. This study investigates the capacity of each land‐use to yield water, suspended sediment concentration (SSC) and dissolved solid concentration (DSC). The hypothesis is that DSC and SSC from the agricultural area are greater than DSC and SSC of the forest area. Results showed that the agriculture area produced significantly greater mean DSC than in the forest area, the main contribution was the Ca²⁺ (24·68 ± 46·52 mg l^?1) ion at the agricultural area. A long‐term sediment production rate at the agricultural outlet was calculated (69·1 tonnes per 100 years) based on the total sediment discharge (TSD) and the recurrence interval of the largest event of the five rainstorms (October 2005). Geographic information system (GIS) spatial data layers of the watershed were produced to determine the relation of tracks, landforms, slopes and forest management to SSC yield in the forest outlet (133·89 ± 308·14 mg l^?1) during the five rainstorms. Agriculture practices are the main cause of soil erosion at the study area. Copyright © 2010 John Wiley & Sons, Ltd.     

平潭岛海蚀花岗岩地貌——兼述花岗岩地貌的系列研究和创新

平潭县有“千礁岛县”之称，所属的海潭为全国第五大岛，隔台湾海峡与台湾新竹相距仅68海里，是祖国大陆距台湾最近的地方。千礁岛县皆由花岗岩组成，潮涨潮落，海侵海蚀，铸就了岛上古代海蚀地貌和现代海蚀地貌，且种类齐全，典型奇特，分布广泛，集神、幽、险、趣于一体，尤其花岗岩球状风化铸成的，最突出的有国内最大的海蚀柱、天下奇观“半洋石帆”；浑身赤裸，形体逼真，比四川乐山大佛大四倍的“海坛天神”，横卧海边，头枕沙滩，腿伸大海；等等。素有花岗岩海蚀地貌“甲天下”之称。平潭已开发成国家级风景旅游区，其花岗岩海蚀地貌研究必将为中国研究花岗岩地貌增添新的内容和活力；平潭岛的区位最近台湾，优先利用双休日或节假日开展与台湾北东海岸的类同海蚀地貌进行双向互惠的观光旅游，将有无限广阔、美好前景。     

Pliocene–Quaternary fluvial and aeolian records in the Souss Basin, southwest Morocco: A geomorphological model

The Souss Basin in SW Morocco is filled by Pliocene–Quaternary fluvial, fluvio-lacustrine and aeolian sediments, representing an excellent archive of palaeohydrology, palaeoclimate and the effects of crustal deformation. In general these sediments indicate stream-dominated alluvial systems, influenced by fluctuations in climate (humidity/aridity). Lakes developed within the basin around the Pliocene–Pleistocene transition and persisted into the Early Pleistocene. During this early period, relatively humid conditions are indicated by the dominance of coarse-grained sedimentation in the upper reaches of fluvial systems, the existence of large lakes and the considerable sediment thicknesses in the centre of the basin. Uplift of the surrounding mountain ranges contributed to piedmont formation by providing large amounts of coarse-grained material that accumulated at the lowland margin. Climatic deterioration in the Middle Pleistocene was accompanied by progressively more irregular and disrupted fluvial regimes. These trends were evident in the Late Pleistocene and became clearer after the mid-Holocene, with aeolian activity becoming the dominant sedimentary agent. Differences between upstream and downstream depositional regimes became marked: while coarse-grained sedimentation has characterized the upper reaches of wadi catchments, fine-grained sedimentation has prevailed downstream. Hiatuses in sedimentation throughout the Pliocene and Quaternary are marked by palaeosol horizons interbedded within the sedimentary sequences, indicating alternate vegetated (stable) and unvegetated (unstable/active) phases (biostasy and ‘rhexistasy’).     

Aesthetic evaluation of yardang landforms landscape: the Dunhuang Yardang National Geo-park example

Dunhuang Yardang National Geo-park,situated in the Gansu Province of northwestern China(40o25'36 "N–40o33'10" N,93o00'00 "E–93o13'30" E),was chosen as a research locality of aesthetics evaluation of yardang landforms landscape.The yardang landforms landscape is a composite structural system of patch-corridor-matrix,with four landscape unit elements as dense group,sparse group,single body and remnant.The study of the landscape aesthetics spatial pattern of Dunhuang Yardang National Geo-park shows that yardang dense group,sparse group and single body provide the greatest contribution to the aesthetic value of yardang landforms landscape.Yardang bodies are scarce,unique,irreplaceable,and priceless resources in yardang landforms areas.However,they are easily destroyed under the influence of the natural and artificial factors.Therefore,when the tourism potential of yardang landforms landscape is exploited,the protection should be fully improved.     

Relations entre production organique et apports terrigènes dans les sédiments fluviatiles holocènes : observations et conclusions hétérodoxes

Accumulation of organic matter in fens of fluvial valleys is often related to a low terrigenous matter delivery and to palaeoenvironmental conditions inducing low mechanical erosion. These assumptions come from the interpretation of contents in organic (MO) and mineral (MM) matters in sediments, expressed in percents, and then exactly anticorrelated. Calculation of mass accumulation rates of MO $(T_{{\mathrm{a}}_{\mathrm{MO}}})$ and MM $(T_{{\mathrm{a}}_{\mathrm{MM}}})$, expressed in g?m^?2?yr^?1, shows that $T_{{\mathrm{a}}_{\mathrm{MO}}}$ and $T_{{\mathrm{a}}_{\mathrm{MM}}}$ generally are not anticorrelated and that high values of $T_{{\mathrm{a}}_{\mathrm{MO}}}$ and $T_{{\mathrm{a}}_{\mathrm{MM}}}$ could appear simultaneously. That expression of MO and MM accumulation makes it possible to precise the climatic and human impact on sedimentation. To cite this article: J.-J. Macaire et al., C. R. Geoscience 337 (2005).     

The influence of upper-crust lithology on topographic development in the central Coast Ranges of California

A fundamental geological tenet is that as landscapes evolve over graded to geologic time, geologic structures control patterns of topographic distribution in mountainous areas such that terrain underlain by competent rock will be higher than terrain underlain by incompetent rock. This paper shows that in active orogens where markedly weak and markedly strong rocks are juxtaposed along contacts that parallel regional structures, relatively high topography can form where strain is localized in the weak rock. Such a relationship is illustrated by the topography of the central Coast Ranges between the Pacific coastline and the San Andreas fault zone (SAFZ), and along the length of the Gabilan Mesa (the “Gabilan Mesa segment” of the central Coast Ranges). Within the Gabilan Mesa segment, the granitic upper crust of the Salinian terrane is in contact with the accretionary-prism mélange upper crust of the Nacimiento terrane along the inactive Nacimiento fault zone. A prominent topographic lineament is present along most of this lithologic boundary, approximately 50 to 65 km southwest of the SAFZ, with the higher topography formed in the mélange on the southwest side of the Nacimiento fault.This paper investigates factors influencing the pattern of topographic development in the Gabilan Mesa segment of the central Coast Ranges by correlating shortening magnitude with the upper-crust compositions of the Salinian and Nacimiento terranes. The fluvial geomorphology of two valleys in the Gabilan Mesa, which is within the Salinian terrane, and alluvial geochronology based on optically-stimulated luminescence (OSL) age estimates, reveal that the magnitude of shortening accommodated by down-to-the-southwest tilting of the mesa since 400 ka is less than 1 to 2 m. Our results, combined with those of previous studies, indicate that at least 63% to 78% of late-Cenozoic, northeast-southwest directed, upper-crustal shortening across the Gabilan Mesa segment has been accommodated within the Nacimiento terrane. This is significant because perpendicular to orogenic strike the Nacimiento terrane constitutes less than ¼ of the distance between the coast and the SAFZ, and the other ¾ (or greater) of the distance between the coast and the SAFZ is underlain by the granitic upper crust of the Salinian terrane. We propose that strain and mountain building are localized within the Nacimiento terrane because it consists predominantly of the relatively weak Franciscan Complex mélange, and because the upper crust of the Salinian terrane is composed of relatively strong granitic rocks. Our hypothesis is supported by the distribution of post-seismic surface uplift associated with the 2003, 6.5 M_W San Simeon earthquake, which mimics the topography of the southwestern part of the Gabilan Mesa segment of the central Coast Ranges.     

BOOK REVIEW

Eolian landforms as sandy dunes and dune heaps were mapped by the author in 1979–1980 in a zone where vegetation had been destroyed by a forest fire on 30 June 1976, in an area to the east of Elverum, south-east Norway. The mapped eolian landforms are discussed together with information from 40 samples of the eolian sediment. Winds, mostly from the north and north-west, were responsible for the development of these eolian landforms, utilizing the fluvioglacial sediments accumulated as a sandur during the retreat of the inland ice approximately 10,000 years ago. The winds were active during a short period of time, only a century or so before the area became vegetated.