南海北部陆坡区海底峡谷地貌、沉积特征及控制因素          下载免费PDF全文

刘丛舒  丁巍伟  殷绍如  方鹏高  丁航航 《海洋学研究》2019,37(2):28-43

南海北部陆坡发育众多海底峡谷,其形成、发育、演化过程都存在较大差异。本文选取南海北部陆坡典型的珠江口外海底峡谷群、东沙海底峡谷、台湾浅滩南海底峡谷和澎湖海底峡谷进行研究,通过高分辨率多道地震数据和多波束测深数据,结合前人研究成果,对4条典型海底峡谷的形态特征、沉积充填特征及结构、形成发育过程及控制因素进行研究。结果表明,南海北部陆缘各个海底峡谷的形成受多个控制因素的影响,其影响程度及方式都有差别。构造活动、海平面变化及沉积物重力流与海底峡谷的演化密切相关,而陆地河流和局部构造因素也以不同方式影响着海底峡谷的发育。对于发育在主动大陆边缘的台湾岛东南侧的澎湖海底峡谷,其板块运动和岩浆活动活跃,其上发育的海底峡谷的控制因素以内营力地质作用为主。而具有被动大陆边缘属性的其他3条峡谷,由于构造运动较少或停止,其上发育的海底峡谷的控制因素以外营力地质作用为主。  相似文献   

Controls on Holocene deep‐water sedimentation in the northern Gioia Basin,Tyrrhenian Sea     

FABIANO GAMBERI  MICHAEL MARANI 《Sedimentology》2008,55(6):1889-1903

The northern Gioia Basin of the south‐east Tyrrhenian Sea is a slope basin, ～ 20 km wide and ～ 50 km long, with a bathymetry of ≤ 1300 m, bounded by the Calabro‐Sicilian landmass and the Aeolian Island Arc. Coarse sediment is supplied from the Calabrian margin, where the shelf is very narrow to non‐existent, whereas the wider shelf on the Sicilian margin prevents supply by storing river‐fed sediments. The basin is dominated by the Gioia–Mesima canyon/channel system paralleled by a tongue‐shaped depositional lobe. Multibeam bathymetric surveys, sea floor reflectivity data and airgun seismic profiles reveal the recent evolution of the submarine system. Slope canyons and basin‐floor levéed channels formed where major rivers built deltas at the shelfless Calabrian margin and strong hyperpycnal flows predominated. The channels are a few hundred metres wide and a few tens of metres deep, with a downslope change from a straight to meandering pattern where the slope gradient decreases from 3·2% to 1·7%. The Mesima Channel has its lower segment abandoned because of avulsion and crevasse‐splay formation at an upslope bend. The adjacent Gioia Channel has had its upper segment straightened and lower segment entrenched because of erosional deepening of the Stromboli Valley into which it debouches and which acts as the local base level. Overbank features include levées, coalescent splays and ‘yazoo’ channels; their nature and surface characteristics depend upon the magnitude and sediment grain‐size of spill‐over flows. On an adjoining narrow shelf sliver of the Calabrian margin, in contrast, the coalescing plumes of sediment suspension supplied by an array of smaller coastal streams were apparently spilling over the shelf edge, scouring a funnel‐shaped bypass depression with chutes and forming an elongate, non‐channellized depositional lobe at the slope base. The study demonstrates the impact of sediment source type, shelf width, basin‐floor gradient and base‐level change on the style of deep‐water sedimentation.  相似文献   

Dimensions and architecture of late Pleistocene submarine lobes off the northern margin of East Corsica   总被引：2，自引：0，他引：2  

MARK E. DEPTUCK  DAVID J. W. PIPER  BRUNO SAVOYE  ANNE GERVAIS‡ 《Sedimentology》2008,55(4):869-898

Sandy lobe deposits on submarine fans are sensitive recorders of the types of sediment gravity flows supplied to a basin and are economically important as hydrocarbon reservoirs. This study investigates the causes of variability in 20 lobes in small late Pleistocene submarine fans off East Corsica. These lobes were imaged using ultra‐high resolution boomer seismic profiles (<1 m vertical resolution) and sediment type was ground truthed using piston cores published in previous studies. Repeated crossings of the same depositional bodies were used to measure spatial changes in their dimensions and architecture. Most lobes increase abruptly down‐slope to a peak thickness of 8 to 42 m, beyond which they show a progressive, typically more gradual, decrease in thickness until they thin to below seismic resolution or pass into draping facies of the basin plain. Lobe areas range from 3 to 70 km² and total lengths from 2 to 14 km, with the locus of maximum sediment accumulation from 3 to 28 km from the shelf‐break. Based on their location, dimensions, internal architecture and nature of the feeder channel, the lobes are divided into two end‐member types. The first are small depositional bodies located in proximal settings, clustered near the toe‐of‐slope and fed by slope gullies or erosive channels lacking or with poorly developed levées (referred to as ‘proximal isolated lobes’). The second are larger architecturally more complex depositional bodies deposited in more distal settings, outboard more stable and longer‐lived levéed fan valleys (referred to as ‘composite mid‐fan lobes’). Hybrid lobe types are also observed. At least three hierarchical levels of compensation stacking are recognized. Individual beds and bed‐sets stack to form lobe‐elements; lobe‐elements stack to form composite lobes; and composite lobes stack to form lobe complexes. Differences in the size, shape and architectural complexity of lobe deposits reflect several inter‐related factors including: (i) flow properties (volume, duration, grain‐size, concentration and velocity); (ii) the number and frequency of flows, and their degree of variation through time; (iii) gradient change and sea floor morphology at the mouth of the feeder conduit; (iv) lobe lifespan prior to avulsion or abandonment; and (v) feeder channel geometry and stability. In general, lobes outboard stable fan valleys that are connected to shelf‐incised canyons are wider, longer and thicker, accumulate in more basinal locations and are architecturally more complex.  相似文献   

Architecture and evolution of the Paine channel complex, Cerro Toro Formation (Upper Cretaceous), Silla Syncline, Magallanes Basin, Chile     

WILLIAM H. CRANE  DONALD R. LOWE 《Sedimentology》2008,55(4):979-1009

The Upper Cretaceous Cerro Toro Formation in the Silla Syncline, Parque Nacional Torres del Paine, Magallanes Basin, Chile, includes over 1100 m of mainly thin‐bedded mud‐rich turbidites containing three thick divisions of coarse conglomerate and sandstone. Facies distributions, stacking patterns and lateral relationships indicate that the coarse‐grained sandstone and conglomerate units represent the fill of a series of large south to south‐east trending deep‐water channels or channel complexes. The middle coarse division, informally named the Paine member, represents the fill of at least three discrete channels or channel complexes, termed Paine A, B and C. The uppermost of these, Paine C, represents a channel belt about 3·5 km wide and its fill displays explicit details of channel geometry, channel margins, and the processes of channel development and evolution. Along its northern margin, Paine C consists of stacked, laterally offset channels, each eroded into fine‐grained mudstone and thin‐bedded sandy turbidites. Along its southern margin, the Paine C complex was bounded by a single, deeply incised but stepped erosional surface. The evolution of the Paine C channel occurred through multiple cycles of activity, each involving: (i) an initial period of channel erosion into underlying fine‐grained sediments; (ii) deposition of coarse‐grained pebble to cobble conglomerate and sandstone within the channel; and (iii) waning of coarse sediment deposition and accumulation of a widespread sheet of fine‐grained, thin‐bedded turbidites inside and outside the channel. The thin‐bedded turbidites deposited within, and adjacent to, the channel along the northern margin of the Paine C complex do not appear to represent levée deposits but, rather, a separate fine‐grained turbidite system that impinged on the Paine C channel from the north. The Cerro Toro channel complex in the Silla Syncline may mark either an early axial zone of the Magallanes Basin or a local slope mini‐basin developed behind a zone of slope faulting and folding now present immediately east of the syncline. If the latter, flows moving downslope toward the basin axis further east were diverted to the south by this developing structural high, deposited part of their coarse sediment loads, and exited the mini‐basin at a point located near the south‐eastern edge of the present Silla Syncline.  相似文献   

Sedimentology,structure and age estimate of five continental slope submarine landslides,eastern Australia     

S. Clarke  T. Hubble  J. Webster  D. Airey  E. De Carli  C. Ferraz 《Australian Journal of Earth Sciences》2016,63(5):631-652

Sedimentological and accelerator mass spectrometry (AMS) ¹⁴C data provide estimates of the structure and age of five submarine landslides (～0.4–3 km³) present on eastern Australia's continental slope between Noosa Heads and Yamba. Dating of the post-slide conformably deposited sediment indicates sediment accumulation rates between 0.017 m ka^–1 and 0.2 m ka^–1, which is consistent with previous estimates reported for this area. Boundary surfaces were identified in five continental slope cores at depths of 0.8 to 2.2 m below the present-day seafloor. Boundary surfaces present as a sharp colour-change across the surface, discernible but small increases in sediment stiffness, a slight increase in sediment bulk density of 0.1 g cm^–3, and distinct gaps in AMS ¹⁴C ages of at least 25 ka. Boundary surfaces are interpreted to represent a slide plane detachment surface but are not necessarily the only ones or even the major ones. Sub-bottom profiler records indicate that: (1) the youngest identifiable sediment reflectors upslope from three submarine landslides terminate on and are truncated by slide rupture surfaces; (2) there is no obvious evidence for a post-slide sediment layer draped over, or burying, slide ruptures or exposed slide detachment surfaces; and (3) the boundary surfaces identified within the cores are unlikely to be near-surface slide surfaces within an overall larger en masse dislocation. These findings suggest that these submarine landslides are geologically recent (<25 ka), and that the boundary surfaces are either: (a) an erosional features that developed after the landslide, in which case the boundary surface age provides a minimum age for the landslide; or (b) detachment surfaces from which slabs of near-surface sediment were removed during landsliding, in which case the age of the sediment above the boundary surface indicates the approximate age of landsliding. While an earthquake-triggering mechanism is favoured for the initiation of submarine landslides on the eastern Australian margin, further evidence is required to confirm this interpretation.  相似文献   

珠江口盆地陆架坡折带海底滑坡及其影响因素   总被引：3，自引：1，他引：2  

王磊  吴时国  李清平  王大伟 《海洋科学》2016,40(5):131-141

为了解海底滑坡在陆架坡折演化过程中所起的作用并分析影响海底滑坡发育的因素,以最新采集的二维和三维地震资料为基础,综合运用了地貌分析和地震解释技术,通过对滑坡的地貌形态特征及地震响应特征进行详细刻画,在珠江口盆地陆架坡折带新近纪地层中识别出多处海底滑坡,明确了其分布范围并建立了滑坡发育的地质模式。分析认为,珠江口盆地相对海平面变化和流体活动的综合作用是导致研究区海底不稳定的主要因素。海底滑坡发源于海底峡谷的朔源侵蚀,向上陆坡扩展并终止于陆架坡折带。  相似文献   

基于感应电流测量的海峡水通量海底缆线观测系统设计     

连展  官晟  魏泽勋  王新怡  孙宝楠 《海洋科学》2016,40(10):71-75

首先回顾了基于海底缆线的海峡水通量观测理论方法的发展历程,对基于电压测量的水通量反演方法进行了梳理,重点阐述了其中的关键观测要素和主要误差来源。为了提升系统可靠性、摒弃外界因素干扰,提出了一种基于感应电流测量的观测方法。对比传统方法,分析了本方法的优缺点,评估了基于本方法的海洋观测系统建设需求和可能性。最后应用本系统建立的一个理想海域——青岛胶州湾湾口各类海洋要素的典型取值范围,通过合理的特征尺度估算和量纲分析,估计了基于电流测量的观测系统中的各类设备的参数要求,其中关键测量器材——电流表至少应满足观测量程覆盖10~(–1)~10~1 m A,观测精度大于1μA,取样频率大于1/60 Hz。在电学测量仪器中,适应本系统要求的器材较普遍,可选择的测量仪器种类较丰富。  相似文献   

斜向波作用下海底管线周围床沙组成变化          下载免费PDF全文

程永舟  鲁显赫  易蕾  胡有川  李小超 《水科学进展》2016,27(5):735-742

海底管线周围的不平衡输沙影响着海底管线的局部冲刷,进而影响海底管线的安全运营。基于波浪港池实验,考虑规则波的作用,采用中值粒径为0.219 mm的原型沙铺设与波浪传播方向成45°夹角的斜坡,斜坡坡度为1∶15,研究管线局部冲刷坑床沙组成变化情况。实验结果表明:与冲刷深度随时间的发展类似,冲刷宽度随时间的发展也分为初级阶段和次级阶段;管线周围床沙粗化程度最高的地方并不在管线的正下方,而在管线的后下方;周期增加,冲刷坑床沙粗化程度增大;与原始床沙相比,周期较小时,冲刷坑下方床沙细化,周期较大时则粗化,而波高对床沙扰动的影响具有不稳定性。  相似文献   

海底滑坡对置于海床表面管线作用力的CFD模拟   总被引：2，自引：0，他引：2  

王忠涛  王寒阳  张宇 《海洋学报》2016,38(9):110-117

海底管线是海洋工程中用于传输原油和天然气等的重要通道,通常放置在海床表面或处于悬跨状态。本文采用计算流体动力学CFD法模拟了不同冲击角度下海底滑坡对置于海床表面的海底管线的作用,得到了管线所受的轴向荷载和法向荷载与滑坡冲击角度之间的关系。同时分析了沿冲击方向管线截面形状与管线所受阻力之间的关系。对已有研究进行拓展延伸,丰富了不同工况下轴向阻力系数和法向阻力系数的计算成果,得出了海底滑坡对置于海床表面管线冲击力的计算公式。  相似文献   

陵水凹陷北坡海底扇孔隙演化和成岩相研究     

曾小明  于佳  潘燕  陈晓武  张辉 《沉积学报》2016,34(6):1198-1207

琼东南盆地陵水凹陷北坡海底扇储层岩性较细,物性较差,并且对其低渗的成因不明、甜点的展布也不清。通过利用岩石薄片、扫描电镜、粒度分析、压汞以及物性等资料来分析其孔隙演化,并从成岩相的研究角度来预测其甜点展布。研究结果认为研究区梅山组二段储层孔隙类型主要为原生粒间孔和铸模孔,处在中成岩阶段A期。从沉积因素和成岩作用两个方面总结出了研究区的孔隙演化模式:沉积环境控制了原始孔隙度的大小,后期机械压实是孔隙减小的主要原因,溶解作用对孔隙增大起到了巨大贡献。研究区主要识别和划分出了中等压实长石溶蚀相、中等压实海绿石胶结相和强压实弱溶蚀相3种成岩相,甜点主要分布在水动力较强的海底扇内扇中等压实长石溶蚀相中。  相似文献