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1.
北大西洋洛克尔海槽东北部内波沉积--深水大型沉积物波成因的再解释 总被引：25，自引：2，他引：23
北大西洋洛克尔海槽东北部水深约1 000～ 1 000 m 处有两个大型沉积物波发育区。波长1 ～ 2 km,波高18 ～ 20 m,分布面积分别为350 km 2 与 20 km 2。沉积物波向上坡迁移,内部包括上攀床形单元、不对称波形单元及正弦波形单元。前人提出的大区沉积物波挪威海底层水溢流成因及小区沉积物Lee波迁移模式都存在许多问题。根据古气候及古洋流资料,研究区内沉积物波各单元形成时具备内波形成的条件,内波的发育与等深流的活动密切相关。运用内波理论可对沉积物波各构成单元作出合理的水动力学解释,研究区内两列同向内波的叠加、单列内波及内驻波先后作用海底,可分别形成大型上攀床形、不对称波形及正弦波形单元。 相似文献
2.
塔中地区中晚奥陶世内波、内潮汐沉积 总被引：35，自引：7，他引：28
现代海底普遍发育由内波、内潮汐引起的深水牵引流,内波、内潮汐不仅可形成各种厘米级的深水牵引流沉积构造,还可建造千米级的大型沉积物波。这种大型沉积物波既可沿斜坡向下迁移,也可沿斜坡向上迁移。在古代地层记录中已发现各种厘米级的内波、内潮汐沉积单元,但尚未发现内波成因的大型沉积物波。塔中地区中上奥陶统碎屑岩段内发育内波及内潮汐形成的各种牵引流沉积构造单元。通过详细的岩心观察,识别出 4种内波、内潮汐沉积微相类型及 5种基本垂向沉积层序。此外,通过地震剖面分析,在研究区中上奥陶统陆坡相中识别出顺坡向上迁移的大型沉积物波,该沉积物波的特征与现代海底发育的沉积物波的特征类似,运用内波理论可对其成因进行合理的解释。 相似文献
3.
海底上发育深水牵引流形成的各种床形单元,包括等深岩丘及大型沉积物波在内的不同床形单元有规律地组合在一起,对于此类床形组合的确切形成机理,目前仍在探讨之中。本文经详细研究得出以下几点进展：① 运用内波理论可对海底上大型沉积物波各组成单元的成因作出较为合理的解释,向深海方向传播的内波可形成向上坡方向迁移的大型沉积物波;② 在等深流与上覆低密度水体之间的界面上具备产生大规模界面内波的条件;③ 某些底流成因的床形单元组合属于等深流与等深流所引发内波的联合作用的产物,首次提出了等深流－内波沉积组合的概念;④ 在现代海底上及古代地层记录中均发现了等深流－内波沉积组合的实例;⑤ 建立了一个古代地层记录中的深水牵引流沉积组合综合模式。 相似文献
4.
内波沉积中指向沉积构造的形成机理 总被引：4，自引：0，他引：4
深海大型沉积物波的发现,引起了国内外内波成因理论的兴起和发展。研究认为,内波作用于海底时可对海底沉积物进行改造,形成指向沉积构造,这种指向沉积构造可为单向、双向或多向,而其中与内波传播方向相反的反向沉积构造可能是内波沉积所特有的。对于这种反向沉积构造的形成,以LaFond的理论为代表,认为内波引起的底流水平流速反比于密度界面距海底的高度,波谷接近海底,因而可形成反向沉积构造。经研究分析,发现内波与表面波在本质上具有一定的相似性,因而认为用一般意义上的波动理论来解释内波沉积中指向沉积构造的形成机理更加易于理解。明确指向沉积构造的形成机理对于内波沉积的识别具有重要意义。 相似文献
5.
塔中地区中—上奥陶统内波内潮汐沉积与油气勘探 总被引：1，自引：0，他引：1
现代海底普遍发育由内波、内潮汐引起的深水牵引流,内波、内潮汐不仅可形成各种小规模、分散的深水牵引流沉积,而且还可建造千米级的大型沉积物波。在古代地层记录中已发现各种厘米级的内波、内潮汐沉积单元,但尚未发现内波成因的大型沉积物波。通过对塔中地区中—上奥陶统碎屑岩段岩心观察和地震剖面的系统分析,发现了该岩段内由内波和内潮汐作用形成的各种牵引流沉积构造单元。已识别出4种内波、内潮汐沉积微相类型及5种基本垂向沉积层序,同时还在研究区中一上奥陶统陆坡相中识别出了内波成因的大型沉积物波。这些内波、内潮汐沉积具有较好的油气潜能,是该区中—上奥陶统潜在的油气勘探新领域。 相似文献
6.
李琳静 《沉积与特提斯地质》2012,32(2):44-48
本文从海洋物理学角度出发,以内波波动理论为基础,通过建立两个不同密度的水层界面上的两层模型的波动方程对内波的传播特征进行定量解释。通过定量解释表达式可知：内波在两个不同密度的水层界面上传播时,两层内波流之水平速度方向相反,保持通过海底的整个截面的流通量为零。在密度界面之下,波谷处内波流的运动方向与内波前进方向相反,由于波谷相对于波峰更接近于海底,即波谷处截面积较小,故波谷下方的流速较波峰下方的流速大,容易形成与内波前进方向相反的单向优势流动,这种单向优势流动搬运沉积物的总趋势与内波的前进方向相反。 相似文献
7.
介绍了内波的概念、沉积实例、沉积特征、沉积模式等;还对内波沉积作用机理作了深入分析。大多数海洋和湖泊中都有内波存在,其波幅可以是表面波的20～30倍,是海水混合和海底沉积物二次搬运的重要营力。内波形成的沉积物规模可以很大,沉积物中的砂岩成分成熟度和结构成熟度高。内波沉积研究对于油气勘探具有重要意义,特别是在海相油气勘探领域。目前对内波沉积物的成岩特征和含油气性方面的研究还比较薄弱;应从沉积特征、地球物理响应、测井响应等方面入手,逐步形成一套全面、系统、完整的识别标志;还应该与海洋学、水动力学等研究紧密结合,深入探讨内波的形成机理和控制因素。 相似文献
8.
关于深水环境下内波、内潮汐沉积分类的探讨 总被引：2，自引：0，他引：2
深水环境下内波、内潮汐沉积从在地层记录中被发现已过去20年,在这20多年里虽然积累了不少资料,但至今未对内波、内潮汐沉积进行细分。本文以地层记录中已发现的内波、内潮汐沉积为基础,结合内波、内潮汐的破碎过程和海洋物理学中内波的研究现状,对深水内波、内潮汐沉积的分类进行了探索。将其分为3个层次下的9种类型,分别为：正压内潮汐沉积、斜压内潮汐沉积、正压短周期内波沉积、斜压短周期内波沉积、等深流叠加内波沉积、低密度浊流叠加内波沉积、长周期内波叠加沉积、驻波沉积和其他内波叠加沉积。地层记录中已发现的内波、内潮汐沉积分别归为：正压内潮汐沉积、正压短周期内波沉积和长周期内波叠加沉积3类,其余类型尚未被发现。这样的分类较合理地解释了为什么在现代海洋中内波、内潮汐无处不在,但地层记录中的内波、内潮汐沉积却少得可怜的现象,同时将内波、内潮汐沉积研究和海洋物理学中对内波的研究结合起来,并能将内波、内潮汐沉积研究置于更为广阔的研究背景之中,使之可以和大洋突发事件、天文旋回及大洋环流等联系起来。 相似文献
9.
中国油气勘探的一个新领域——深水牵引流沉积 总被引：4，自引：0，他引：4
深水牵引流沉积主要分为等深流沉积和内波内潮汐沉积两类。前者可形成巨大的堆积体——等深积岩丘,其规模可与海底扇相比拟。现代海洋大陆坡及陆隆地带等深积岩丘非常发育;古代地层记录中也有等深积岩丘,如已开采数十年的阿拉伯克拉通白垩系等深积岩丘油田。后者则不仅可形成分选极好的砂级沉积物,而且可形成规模巨大的“沉积物波”,并成群成带地出现。海洋中沉积物波的迁移可形成巨大的沉积体。在世界各大洋深盆海底,均有大范围分布的现代大型沉积物波。中国地层记录中的大型沉积物波,首先在塔里木盆地塔中地区中一上奥陶统中被识别出来,并有良好油气显示。认为中国的广大地区发育有多个时代的海相深水沉积,深水牵引流沉积储集层是中国21世纪油气勘探具巨大潜力和现实可行性的新领域。其油气勘探首选地区是塔里木盆地、扬子地台南缘和鄂尔多斯西缘。 相似文献
10.
<正> 关于浊流沉积垂向上的结构构造特征的鲍玛序列(1962)已大多数学者所接受,认为这是鉴别经典浊积岩的标准层序。随着人们对深水异地沉积的另一重要领域——深水牵引流沉积的深入研究,鲍玛序列的多解性显得越来越明显。目前,对鲍玛序列各阶段存在的不同成因解释如表1所示。鲍玛序列各段部存在不同的成因解释,沉积物重力流及深水牵引流理论的发展要求重新审视鲍玛序列所代表的真正含义。等深流、内波流及内潮汐流等深水牵引流、沉积物重力流引发的牵引流对早期重力流沉积进行改造,可形成不同类型的沉积物重力流—深水牵引流沉积组合,该组合类似于鲍玛序列的沉积特征,因而在实际解释中极可能将其归为具鲍 相似文献
11.
Based on numerous high-resolution seismic profiles, sediment waves and their distribution, morphological characteristics, internal structure, and potential origins were revealed in the eastern waters of Taiwan. The sediment waves are located at the junction between the Taitung Canyon and other canyons in the slope. The wave length and the wave height of a single waveform ranged from 0.8 to 7.2 km and from 18 to 75 m, respectively (NE-SW direction). Sediment waves, located inside the bend of the Taitung Canyon, were characterized by an upward migration and showed mass transport deposits (MTDs) at the bottom, while the inner curve of the bend was subdivided into lower and upper wavy transition units. The sediment waves on the outer curve of the bend were characterized by vertical accumulation, and there was no mass flow deposit at the bottom. According to the geometry of the sediment waves, the calculated flow thicknesses across the entire wave field ranged from 196 to 356 m, and the current velocity ranged from 15 to 21 cm/s. The morphological characteristics, the internal structure, and the distribution of sediment waves, as well as the numerical calculations, evidenced that these sediment waves had formed by turbidity currents. The development of the sediment wave field in eastern Taiwan was found to be similar to that in southwestern Taiwan. It was the sedimentary response of the tectonic movement between 3 and ~1 Ma which created the sedimentary systems where gravity flow processes predominated. Turbidity current sediments settled in the place of less topographical constraints or overflowed in the bend section of the Taitung Canyon, which resulted in the formation of sediment wave fields. 相似文献
12.
Sediment waves are commonly observed on the sea floor and often vary in morphology and geometry according to factors such as seabed slope, density and discharge of turbidity currents, and the presence of persistent contour currents. This paper documents the morphology, internal geometry and distribution of deep‐water (4000 to 5000 m) bedforms observed on the sea floor offshore eastern Canada using high‐resolution multibeam bathymetry data and seismic stratigraphy. The bedforms have wavelengths of >1 km but fundamentally vary in terms of morphology and internal stratigraphy, and are distinguished into three main types. The first type, characterized by their long‐wavelength crescentic shape, is interpreted as net‐erosional cyclic steps. These cyclic steps were formed by turbidity currents flowing through canyons and overtopping and breaching levées. The second type, characterized by their linear shape and presence on levées, is interpreted as net‐depositional cyclic steps. These upslope migrating bedforms are strongly aggradational, indicating high sediment deposition from turbidity currents. The third type, characterized by their obliqueness to canyons, is observed on an open slope and is interpreted as antidunes. These antidunes were formed by the deflection of the upper dilute, low‐density parts of turbidity currents by contour currents. The modelling of the behaviour of these different types of turbidity currents reveals that fast‐flowing flows form cyclic steps while their upper parts overspill and are entrained westward by contour currents. The interaction between turbidity currents and contour currents results in flow thickening and reduced sediment concentration, which leads to lower flow velocities. Lower velocities, in turn, allow the formation of antidunes instead of cyclic steps because the densiometric Froude number (Fr′) decreases. Therefore, this study shows that both net‐erosional and net‐depositional cyclic steps are distributed along channels where turbidity currents prevail whereas antidunes form on open slopes, in a mixed turbidite/contourite system. This study provides insights into the influence of turbidity currents versus contour currents on the morphology, geometry and distribution of bedforms in a mixed turbidite–contourite system. 相似文献
13.
Sedimentary processes in the Selvage sediment-wave field, NE Atlantic: new insights into the formation of sediment waves by turbidity currents 总被引：5，自引：0，他引：5
Russell B. Wynn Philip P. E. Weaver Gemma Ercilla Dorrik A. V. Stow & Douglas G. Masson 《Sedimentology》2000,47(6):1181-1197
An integrated geophysical and sedimentological investigation of the Selvage sediment-wave field has revealed that the sediment waves are formed beneath unconfined turbidity currents. The sediment waves occur on the lower continental rise and display wavelengths of up to 1 km and wave heights of up to 6 m. Wave sediments consist of interbedded turbidites and pelagic/hemipelagic marls and oozes. Nannofossil-based dating of the sediments indicates a bulk sedimentation rate of 2·4 cm 1000 years–1 , and the waves are migrating upslope at a rate of 0·28 m 1000 years–1 . Sediment provenance studies reveal that the turbidity currents maintaining the waves are largely sourced from volcanic islands to the south. Investigation of existing models for sediment-wave formation leads to the conclusion that the Selvage sediment waves form as giant antidunes. Simple numerical modelling reveals that turbidity currents crossing the wave field have internal Froude numbers of 0·5–1·9, which is very close to the antidune existence limits. Depositional flow velocities range from <6 to 125 cm–1 . There is a rapid increase in wavelength and flow thickness in the upper 10 km of the wave field, which is unexpected, as the slope angle remains relatively constant. This anomaly is possibly linked to a topographic obstacle just upslope of the sediment waves. Flows passing over the obstacle may undergo a hydraulic jump at its boundary, leading to an increase in flow thickness. In the lower 15 km of the wave field, flow thickness decreases downslope by 60%, which is comparable with results obtained for other unconfined turbidity currents undergoing flow expansion. 相似文献
14.
台湾东部海域沉积物波特征及其成因探讨 总被引：1，自引：0，他引：1
利用地震剖面对沉积物波的分布、形态和内部结构进行了分析,结合区域地质背景对沉积物来源和成因进行了探讨。识别出的沉积物波域主要位于台东峡谷与陆坡其他峡谷的交汇区,单个波形的波长为0.8～7.2 km,波高为18～75 m左右,呈NE—SW向展布。台东峡谷弯曲段内侧向上坡迁移的沉积物波,其底界发育块体流沉积,内部可细分为下部过渡单元和上部波形单元。弯曲段外侧的沉积物波呈垂向加积的特征,底部无块体流沉积。基于沉积物波的几何形态,估算整个波域的流体厚度在196～356 m之间,流体速度在15～21 cm/s之间。沉积物波的形态特征、内部结构、分布规律以及数值计算表明这些沉积物波为浊流成因。台湾东部海域沉积物波域的发育与台湾西南部的沉积物波域一样,是台湾造山运动的沉积响应。距今3.5 Ma以来花东海脊的形成以及广燠火山岛—绿岛—兰屿火山岛间闸口的抬升和封闭使得沉积物经由卑南溪及海下水道向南输送到绿岛西侧的台东海槽残留弧前盆地时受阻,转而沿台东峡谷及陆坡冲沟体系向东输送入花东海盆。浊流沉积物沿着峡谷/沟谷体系向下坡方向输送的过程中,在峡谷/冲沟的嘴部等地形限制性降低的位置卸载,或在台东峡谷的高弯曲段漫溢出来,从而形成沉积物波域。 相似文献
15.
Three‐dimensional seismic analysis of sediment waves and related geomorphological features on a carbonate shelf exposed to large amplitude internal waves,Browse Basin region,Australia 
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下载免费PDF全文 This study analyses the three‐dimensional geometry of sedimentary features recorded on the modern sea floor and in the shallow subsurface of a shelf to upper slope region offshore Australia that is characterized by a pronounced internal wave regime. The data interpreted comprise an extensive, >12 500 km2 industrial three‐dimensional seismic‐reflection survey that images the northern part of the Browse Basin, Australian North West Shelf. The most prominent seismic–morphological features on the modern sea floor are submarine terrace escarpments, fault‐scarps and incised channels, as well as restricted areas of seismic distortion interpreted as mass wasting deposits. Besides these kilometre‐scale sea floor irregularities, smaller bedforms were discovered also, including a multitude of sediment waves with a lateral extent of several kilometres and heights up to 10 m. These sedimentological features generally occur in extensive fields in water depths below 250 m mostly at the foot of submerged terraces, along the scarps of modern faults and along the shelf break between the outer shelf and the upper continental rise. Additional bedforms that characterize the more planar regions of the outer shelf are elongate, north‐west/south‐east oriented furrows and ridges. The formation of both sediment waves and furrow‐ridge systems requires flow velocities between 0·3 m sec?1 and 1·5 m sec?1, which could be generated by oceanic currents, gravity currents or internal waves. In the studied setting, these velocities can be best explained as being generated by bottom currents induced by internal waves, an interpretation that is discussed against oceanographic background data and modelling results. In addition to the documentation of three‐dimensional seismic–geomorphological features of the modern sea floor, it was also possible to map kilometre‐scale buried sediment wave fields in the seismic volume down to ca 500 ms two‐way‐time below the present sea floor, indicating the general potential for the preservation of such bedforms in the sedimentary record. 相似文献
16.
A 4·7 km2 field of sediment waves occurs in front of the Slims River delta in Kluane Lake, the largest lake in the Yukon Territory. Slims River heads in the Kaskawulsh Glacier, part of the St Elias Ice Field and discharges up to 400 m3 s?1 of water with suspended sediment concentrations of up to 7 g l?1. The 19 km long sandur of Slims River was created in the past 400 years since Kaskawulsh Glacier advanced and dammed the lake and the sandur has advanced into Kluane Lake at an average rate of 48 m a?1. However, this rate is decreasing as flow is diverted from Slims River because of the retreat of the Kaskawulsh Glacier. The sandur and a road constructed on the delta remove coarse‐grained sediment, so the river delivers dominantly mud to the lake. Inflow during summer generates quasi‐continuous turbidity currents with velocities up to 0·6 m s?1. The front of the delta consists of a plane surface sloping lakeward at 0·0188 (1·08°). A field of sediment waves averaging 130 m in length and 2·3 m in amplitude has developed on this surface. Slopes on the waves vary from ?0·067 (?3·83°, i.e. sloping in the opposite direction to the regional slope) to 0·135 (7·69°). The internal structure of the sediment waves, as documented by seismic profiling, shows that sedimentation on the stoss portion of the wave averages 2·7 times that on the lee portion. Rates of sediment accumulation in the wave field are about 0·3 m a?1, so these lacustrine waves have formed in a much shorter period of time (less than 200 years) and are advancing upslope towards the delta much more quickly (1 to 2 m a?1) than typical marine sediment waves. These waves formed on the flat surface of the lake floor, apparently in the absence of pre‐existing forms, and they are altered and destroyed as the wave field advances and the characteristics of the turbidity currents change. 相似文献