Ecological restoration in the deep sea: Desiderata

An era of expanding deep-ocean industrialization is before us, with policy makers establishing governance frameworks for sustainable management of deep-sea resources while scientists learn more about the ecological structure and functioning of the largest biome on the planet. Missing from discussion of the stewardship of the deep ocean is ecological restoration. If existing activities in the deep sea continue or are expanded and new deep-ocean industries are developed, there is need to consider what is required to minimize or repair resulting damages to the deep-sea environment. In addition, thought should be given as to how any past damage can be rectified. This paper develops the discourse on deep-sea restoration and offers guidance on planning and implementing ecological restoration projects for deep-sea ecosystems that are already, or are at threat of becoming, degraded, damaged or destroyed. Two deep-sea restoration case studies or scenarios are described (deep-sea stony corals on the Darwin Mounds off the west coast of Scotland, deep-sea hydrothermal vents in Manus Basin, Papua New Guinea) and are contrasted with on-going saltmarsh restoration in San Francisco Bay. For these case studies, a set of socio-economic, ecological, and technological decision parameters that might favor (or not) their restoration are examined. Costs for hypothetical restoration scenarios in the deep sea are estimated and first indications suggest they may be two to three orders of magnitude greater per hectare than costs for restoration efforts in shallow-water marine systems.     

Rapid incision of a small,coarse and steep fan‐delta in response to base‐level fall: the case of Nahal Qedem,the Dead Sea,Israel

The Dead Sea has been continuously dropping 0·4–1·0 m yr^?1 since the middle of the 20th century and thus provides a unique field laboratory for studying in real time the response of drainage systems to a non‐tectonic base‐level fall. The aim of this work is to study the short‐term ongoing erosive response to a rapid base‐level drop in a small, steep‐fronted, erodible fan‐delta setting. The work explores the controls of the steep Qedem fan‐delta, guided by its clinoform structure, on its incision. Longitudinal profiles of the fan‐delta and of its entrenched channel were measured in the field. Sedimentary facies changes – fluviatile, shallow lacustrine and beach – were followed along exposures. The existence of large boulders provided an opportunity to examine the uncertain role of armouring and boulder flux on incision. The field study was combined with digital elevation models (DEMs) that were extracted from pairs of overlapping aerial photos. Maps of erosion and deposition were prepared using a change detection algorithm. The longitudinal profile of the entrenched channel was found to be steep and linear. The outlet temporarily ‘hangs’ elevated and ungraded above the retreating lake level, indicating years without incision flow events, which cause lags in response to the rapid lake level drop. In spite of the large boulders, the small drainage basin and precipitation volume over the basin of the Qedem, the recorded vertical incision rates in the unconsolidated sediments are as high as 0·8 m yr^?1, i.e. similar to those of the largest wadis draining to the Dead Sea. The steep front of the fan‐delta is suggested to be a main factor controlling the efficient incision. A unique transport mechanism of rolling boulders, following undercutting, contributed to the entrenchment efficiency. Copyright © 2010 John Wiley & Sons, Ltd.     

北京平原区永定河冲洪积扇地下水水化学特征与演化规律

本文以北京市平原区永定河冲洪积扇地下水化学场的演化机理及地下水水循环规律为研究目的,根据水化学特征的水平分布及典型剖面上的演化过程研究,得到以下结论:1)从永定河冲洪积扇顶部补给区到扇缘排泄区,地下水水化学类型呈现水平分带性,潜水水化学类型由Ca-HCO3过渡到Ca·Mg-HCO3、Mg·Na-SO4,局部因人类活动影...     

松辽盆地北部英台～他拉哈地区青一段、青二段深水湖底扇的识别及其油气地质意义

综合利用钻井资料和三维地震资料,通过精细井震标定、地震正演、地震属性分析、古地貌分析和相控储层预测技术,在松辽盆地英台～他拉哈地区青一段、青二段发现深水湖底扇群。湖底扇分布受控于西部坡折带,呈南北向展布,在空间上呈透镜状分布,扇体总面积约447 km2。深水湖底扇烃源岩条件优越,储盖关系良好,具有较大油气勘探潜力,是松辽盆地不可忽视的勘探区域。     

LS凹陷岩性油气藏勘探实践

LS凹陷是一个东断西超的断陷盆地,古新统MYF组低位沉积时期,西斜坡上形成了“沟＋坡＋扇”沉积格局,岩性圈闭发育其中。从岩性圈闭沉积背景出发,综合应用高分辨率层序地层学、沉积相分析、储层预测和描述等关键技术,发现了一组有利油气聚集的低位扇,揭示了一个具有相同沉积背景、相同成藏机理的勘探领域。     

辽河西部凹陷欢喜岭地区沙河街组沉积特征及其演化

在充分利用岩芯、录井、测井等相关资料的基础上,总结辽河西部凹陷欢喜岭地区沙河街组的沉积相类型,首次提出运用相对单因素综合作图法来绘制各沉积时期的沉积相平面图,综合探讨了沙河街组的沉积特征及空间沉积演化规律。结果表明:欢喜岭地区沙河街组主要发育扇三角洲相、湖底扇相、滨浅湖相和半深湖—深湖相4种沉积相类型;扇三角洲砂体为欢喜岭地区主要的储集砂体,在沙河街组沉积时期持续发育,主要发育于盆地缓坡部位;湖底扇主要发育在SQ3和SQ4沉积时期,主要分布在广阔的半深湖—深湖环境内;相对单因素综合作图法可以弥补传统的沉积相作图方法精度低的不足;沙河街组的沉积相垂向演化的旋回性明显,自下而上分为两个水进旋回,分别为SQ2～SQ5沉积时期和SQ6、SQ7沉积时期;每个水进旋回初期,盆地构造活动相对较弱,水体较浅,扇三角洲沉积广泛发育,湖底扇沉积规模较小;每个水进旋回中后期,盆地构造活动强度大,湖盆水体加深,扇三角洲规模减小,而湖底扇沉积规模明显扩大,形成非常有利的储集砂体,在研究区广泛发育,是研究区深层勘探的有利目标之一。     

西秦岭文县地区关家沟组海底扇沉积体系

对西秦岭南部文县地区关家沟组的成因,学者之间的认识存在较大分歧,长期以来被看作是可与南沱组对比的冰碛层.关家沟组形成于新元古代末期(晚震旦世),沿扬子板块西北边缘分布.根据地层剖面和扇地质体的平面填图研究表明,关家沟组存在两种沉积体系--海底扇沉积体系和盆地沉积体系;海底扇沉积体系中发育大量的各种类型的粒序层理及鲍玛层序;扇体的剖面结构相似于Walker(1979)提出的海底扇反旋回沉积序列,层理类型与Winn和Dott(1979)提出的海底扇的层理类型类似;扇体的平面结构(填图追索圈定)清楚地显示了海底扇砂砾岩与盆地相页岩、硅质岩之间的穿插相变关系.其剖面结构可划分出4个级别的不对称它旋回性韵律,显示出扇体向盆地推进和相对海平面的降低.研究表明关家沟组砂砾岩为海底扇沉积体系,而非冰碛层.     

东营凹陷王庄地区古近纪沙河街组三段扇三角洲砂砾岩体沉积特征分析

本文利用现代沉积学、测井学和地震勘探等手段,对王庄地区砂砾岩扇体特征进行了研究,认为该区在古近纪以形成古近系的较高水动力能砂砾岩扇体沉积体为主,其中扇三角洲砂砾岩体是本区最主要的砂砾岩扇体类型,并具有较好的储集性能,是本区最主要的油气储集体;王庄地区砂砾岩扇体沉积,强烈地受控于边界构造条件;砂砾岩扇体沉积及其形态均受沉积相的控制,并具有复杂多变的特征,从而导致了本区油气藏的聚集和分布具有复杂多变的特点。     

Application of kinematic wave theory for predicting flash flood hazards on coupled alluvial fan–piedmont plain landforms

A rainstorm that caused a severe flash flood on the piedmont plain at the toe positions of two alluvial fans located to the west of the Organ Mountains in Dona Ana County, New Mexico, USA, is analysed. The space–time distributions of rainfall are evaluated from the Next Generation Weather Radar (NEXRAD) and overland flow is modelled as kinematic wave. The spatial distribution of rainfall shows a topographic control. The greatest rainfall depth, duration, and intensity occurred at the higher elevation mountain slopes and decreased with decreasing elevation from the alluvial fans to the piedmont plain. The alluvial fan–piedmont plain system is modelled by coupling divergent and rectangular overland flow planes. Explicit finite difference approximations, hybridized with the analytical method of characteristics, are made to the kinematic wave equations to account for the spatial and temporal distribution of the rainfall and variable boundary conditions. Simulation results indicate that sheet‐flow floodwater elevations rise (1) in a nonlinear fashion from the apex to toe positions of the alluvial fans, and (2) near linearly from the toe positions of the alluvial fans onto the piedmont plains with the formation of kinematic shocks near the middle to the upstream end of the plane at times between the initiation of the rainstorm and the time of concentration of the plane. Thus, the maximum flooding occurs at the middle or upstream sections of the piedmont plains regardless of the pattern of space–time variability of rainfall. These results are in agreement with observed geomorphologic features suggesting that piedmont plains are naturally flood‐prone areas. This case study demonstrates that flood hazards on piedmont plains can exceed those on alluvial fans. The models presented in this study suggest that the flood hazard zones on coupled alluvial fan–piedmont plain landforms should be delineated transverse to the flow directions, as opposed to the flood hazard zones with boundaries in the longitudinal direction of the axis of an alluvial fan. Copyright © 2003 John Wiley & Sons, Ltd.     

云南小江流域泥石流堆积扇研究

泥石流堆积扇是判别泥石流性质、发育阶段和危险度的重要依据。通过对小江流域泥石流堆积扇的调查和观测,阐述了泥右流堆积过程和扇形地形成模式,并对泥石流扇群横向、平面组合类型及变形方式进行了分析。研究结果表明:小江流域泥石流堆积扇发育典型,类型齐全,扇群组合复杂,且呈现一定的规律性。