南海北部深海盆地上中新统浊积砂体物源分析^*     

周俊燊  邵磊  乔培军  崔宇驰  孙珍  侯元立  杨逸凯 《古地理学报》2020,22(4):775-784

IODP367/368航次在南海北部深海盆地多个站位发现上中新统厚达数百米的大规模深海浊积岩。采用碎屑锆石U-Pb年龄谱系分析方法对U1500站上中新统浊积砂体进行源汇对比分析。研究结果表明U1500站上中新统浊积岩碎屑锆石年龄谱系与其西侧琼东南盆地和北侧珠江口盆地中新世沉积物特征类似。多维排列分析(MDS)结果也显示,该站位样品与珠江口盆地、琼东南盆地沉积物关系密切,表明南海北部深海盆地内厚达数百米的上中新统浊积砂体为南海北部物源和南海西部物源混合堆积形成。南海西部陆源输入物质以浊流搬运的方式,沿中央峡谷从西到东搬运至南海东部深海盆地;南海北部珠江物源以重力流的形式,经南海北部陆坡峡谷搬运至深海盆地中,两种来源的沉积物在深海盆地发生混合沉积,形成U1500站厚达数百米的浊积砂体。南海北部深海盆地厚层浊积砂体物质来源的准确识别,对深刻理解南海新生代盆地的构造演化、沉积物充填过程、物源演变以及古地理特征均具有重要意义。  相似文献   

Temporal evolution of the Mariana arc during rifting of the Mariana Trough traced through the volcaniclastic record   总被引：1，自引：0，他引：1  

PeterD.  Clift & Jongman  Lee 《Island Arc》1998,7(3):496-512

The sedimentary sequences that accumulate around volcanic arcs may be used to reconstruct the history of volcanism provided the degree of along-margin sediment transport is modest, and that reworking of old sedimentary or volcanic sequences does not contribute substantially to the sediment record. In the Mariana arc, the rare earth and trace element compositions of ash layers sampled by Deep Sea Drilling Project (DSDP) site 451 on the West Mariana Ridge, and sites 458 and 459 on the Mariana Forearc, were used to reconstruct the evolution of the arc volcanic front during rifting of the Mariana Trough. Ion microprobe analysis of individual glass shards from the sediments shows that the glasses have slightly light rare earth element (LREE)-enriched compositions, and trace element compositions typical of arc tholeiites. The B/Be ratio is a measure of the involvement of subducted sediment in petrogenesis, and is unaffected by fractional crystallization. This ratio is variable over the period of rifting, increasing up-section at site 451 and reaching a maximum in sediments dated at 3–4 Ma, ∼ 3–4 million years after rifting began. This may reflect increased sediment subduction during early rifting and roll-back of the Pacific lithosphere. Parallel trends are not seen in the enrichment of incompatible high field strength (HFSE), large ion lithophile (LILE) or rare earth elements (REE), suggesting that flux from the subducting slab alone does not control the degree of melting. Re-establishment of arc volcanism on the trench side of the basin at ca 3 Ma resulted in volcanism with relative enrichment in incompatible REE, HFSE and LILE, although these became more depleted with time, possibly due to melt extraction from the mantle source as it passed under the developing back-arc spreading axis, prior to melting under the volcanic front.  相似文献   

浊流及相关重力流沉积研究综述   总被引：44，自引：2，他引：42  

方爱民  李继亮 《地质论评》1998,44(3):270-280

本文首先介绍了浊流及相关重力流的有关概念,并对浊流沉积研究历史进行了简要回顾,概括了当前浊流沉积的研究现状;随后,总结了浊积岩的沉积特征并对其成因进行了扼要解释;最后,对浊流及相关重力流沉积研究中两个有争议的问题－浊积相的划分和浊积相模式的建立进行了探讨。  相似文献   

Characteristics and evolution of lacustrine turbidite of Chang-7Member of Yanchang Formation in northern Shaanxi     

PANG Jungang  LI Wenhou  XIAO Li 《世界地质(英文版)》2009,12(4):183-188

Lacustrine turbidite of Chang-7 Member in the studied area consists of siltstone and fine sandstone with respect to grain size, which is feldspathic lithic sandstone, syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology, sedimentary structure, sedimentary sequence and well logs, to recognize turbidite. During the paleogeographic evolution of Chang-7 Member, lake basin and deep lake are both at their maximum extent during Chang-73 stage, resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity, connectivity and more thickness, from stages of Chang-73, Chang-72 and Chang-71 , which can be favorable reservoir in deep-water.  相似文献   

Subaqueous sediment density flows: Depositional processes and deposit types   总被引：7，自引：0，他引：7  

PETER J. TALLING  DOUGLAS G. MASSON  ESTHER J. SUMNER  GIUSEPPE MALGESINI 《Sedimentology》2012,59(7):1937-2003

Submarine sediment density flows are one of the most important processes for moving sediment across our planet, yet they are extremely difficult to monitor directly. The speed of long run‐out submarine density flows has been measured directly in just five locations worldwide and their sediment concentration has never been measured directly. The only record of most density flows is their sediment deposit. This article summarizes the processes by which density flows deposit sediment and proposes a new single classification for the resulting types of deposit. Colloidal properties of fine cohesive mud ensure that mud deposition is complex, and large volumes of mud can sometimes pond or drain‐back for long distances into basinal lows. Deposition of ungraded mud (T_E‐3) most probably finally results from en masse consolidation in relatively thin and dense flows, although initial size sorting of mud indicates earlier stages of dilute and expanded flow. Graded mud (T_E‐2) and finely laminated mud (T_E‐1) most probably result from floc settling at lower mud concentrations. Grain‐size breaks beneath mud intervals are commonplace, and record bypass of intermediate grain sizes due to colloidal mud behaviour. Planar‐laminated (T_D) and ripple cross‐laminated (T_C) non‐cohesive silt or fine sand is deposited by dilute flow, and the external deposit shape is consistent with previous models of spatial decelerating (dissipative) dilute flow. A grain‐size break beneath the ripple cross‐laminated (T_C) interval is common, and records a period of sediment reworking (sometimes into dunes) or bypass. Finely planar‐laminated sand can be deposited by low‐amplitude bed waves in dilute flow (T_B‐1), but it is most likely to be deposited mainly by high‐concentration near‐bed layers beneath high‐density flows (T_B‐2). More widely spaced planar lamination (T_B‐3) occurs beneath massive clean sand (T_A), and is also formed by high‐density turbidity currents. High‐density turbidite deposits (T_A, T_B‐2 and T_B‐3) have a tabular shape consistent with hindered settling, and are typically overlain by a more extensive drape of low‐density turbidite (T_D and T_C,). This core and drape shape suggests that events sometimes comprise two distinct flow components. Massive clean sand is less commonly deposited en masse by liquefied debris flow (D_CS), in which case the clean sand is ungraded or has a patchy grain‐size texture. Clean‐sand debrites can extend for several tens of kilometres before pinching out abruptly. Up‐current transitions suggest that clean‐sand debris flows sometimes form via transformation from high‐density turbidity currents. Cohesive debris flows can deposit three types of ungraded muddy sand that may contain clasts. Thick cohesive debrites tend to occur in more proximal settings and extend from an initial slope failure. Thinner and highly mobile low‐strength cohesive debris flows produce extensive deposits restricted to distal areas. These low‐strength debris flows may contain clasts and travel long distances (D_M‐2), or result from more local flow transformation due to turbulence damping by cohesive mud (D_M‐1). Mapping of individual flow deposits (beds) emphasizes how a single event can contain several flow types, with transformations between flow types. Flow transformation may be from dilute to dense flow, as well as from dense to dilute flow. Flow state, deposit type and flow transformation are strongly dependent on the volume fraction of cohesive fine mud within a flow. Recent field observations show significant deviations from previous widely cited models, and many hypotheses linking flow type to deposit type are poorly tested. There is much still to learn about these remarkable flows.  相似文献   

松辽盆地大庆长垣地区嫩江组二段滑塌扇的发现及其石油地质意义          下载免费PDF全文

张顺  付秀丽  张晨晨 《地质科学》2012,47(1):129-138

应用三维地震及测井地质剖面,在松辽盆地大庆长垣地区嫩江组二段发现3套滑塌扇体,北部LMD扇体由5个单体组成,垂向呈前积式交叉叠置,总体呈前缘外凸的铲状,近东西走向,最大面积约为95 km²,最大厚度为62 m; 南部MX扇体由7个单体组成,垂向交叉叠置,平面镶嵌连片,总体走向北北东,总覆盖面积约为61.5 km²,最大厚度为55 m; 中部的SET为独立扇体,呈半圆形,近东西走向,面积约为24 km²,最大厚度为92 m; 3套扇体均具有根部厚、前端薄的发育特征,而且前端以发育泥岩为主,中部及根部发育2～4层粉砂岩,厚度为0.8～7.0 m; 3套扇体及其单体表面均具有弧形地震反射波纹,波纹密度分布在4～10条/km; 推测3套扇体最小古坡度为5‰～12‰,最小古水深为30～70 m,滑移距离为2～10 km; 这一发现为在大型陆相坳陷湖盆中研究滑塌浊积扇体的沉积学特征提供了有利的证据,同时南部MX扇体已经发现工业油流,因此,这一发现也为在坳陷盆地湖相泥岩中寻找油藏提供了新的思路。  相似文献   

The spatial and temporal distribution of grain‐size breaks in turbidites     

Christopher J. Stevenson  Peter J. Talling  Douglas G. Masson  Esther J. Sumner  Michael Frenz  Russell B. Wynn 《Sedimentology》2014,61(4):1120-1156

Grain‐size breaks are surfaces where abrupt changes in grain size occur vertically within deposits. Grain‐size breaks are common features in turbidites around the world, including ancient and modern systems. Despite their widespread occurrence, grain‐size breaks have been regarded as exceptional, and not included within idealized models of turbidity current deposition. This study uses ca 100 shallow sediment cores, from the Moroccan Turbidite System, to map out five turbidite beds for distances in excess of 2000 km. The vertical and spatial distributions of grain‐size breaks within these beds are examined. Five different types of grain‐size break are found: Type I – in proximal areas between coarse sand and finer grained structureless sand; Type II – in proximal areas between inversely graded sand overlain by finer sand; Type III – in proximal areas between sand overlain by ripple cross‐laminated finer sand; Type IV – throughout the system between clean sand and mud; and Type V – in distal areas between mud‐rich (debrite) sand and mud. This article interprets Types I and V as being generated by sharp vertical concentration boundaries, controlled by sediment and clay concentrations within the flows, whilst Types II and III are interpreted as products of spatial/temporal fluctuations in flow capacity. Type IV are interpreted as the product of fluid mud layers, which hinder the settling of non‐cohesive grains and bypasses them down slope. Decelerating suspensions with sufficient clay will always form cohesive layers near to bed, promoting the generation of Type IV grain‐size breaks. This may explain why Type IV grain‐size breaks are widespread in all five turbidites examined and are commonplace within turbidite sequences studied elsewhere. Therefore, Type IV grain‐size breaks should be understood as the norm, not the exception, and regarded as a typical feature within turbidite beds.  相似文献   

Recognition of cyclic steps in sandy and gravelly turbidite sequences,and consequences for the Bouma facies model   总被引：2，自引：0，他引：2  

George Postma  Kick Kleverlaan  Matthieu J. B. Cartigny 《Sedimentology》2014,61(7):2268-2290

Preservation of cyclic steps contrasts markedly with that of subcritical‐flow bedforms, because cyclic steps migrate upslope eroding their lee face and preserving their stoss side. Such bedforms have not been described from turbidite outcrops and cores as yet. A conceptual block diagram for recognition of cyclic steps in outcrop has been constructed and is tested by outcrop studies of deep water submarine fan deposits of the Tabernas Basin in south‐eastern Spain. Experimental data indicate that depositional processes on the stoss side of a cyclic step are controlled by a hydraulic jump, which decelerates the flow and by subsequent waxing of the flow up to supercritical conditions once more. The hydraulic jump produces a large scour with soft‐sediment deformation (flames) preserved in coarse‐tail normal‐graded structureless deposits (Bouma Ta), while near‐horizontal, massive to stratified top‐cut‐out turbidite beds are found further down the stoss side of the bedform. The architecture of cyclic steps can best be described as large, up to hundreds of metres, lens‐shaped bodies that are truncated by erosive surfaces representing the set boundaries and that consist of nearly horizontal lying stacks of top‐cut‐out turbidite beds. The facies that characterize these bedforms have traditionally been described as turbidite units in idealized vertical sequences of high‐density turbidity currents, but have not yet been interpreted to represent bedforms produced by supercritical flow. Their large size, which is in the order of 20 m for gravelly and up to hundreds of metres for sandy steps, is likely to have hindered their recognition in outcrop so far.  相似文献   

Architecture and depositional development of the Eocene deep‐marine Morillo and Coscojuela Formations,Aínsa Basin,Spain     

F. Pohl  T. McCANN 《Geological Journal》2014,49(3):221-238

The Aínsa Basin of northern Spain contains a deep‐marine succession comprising up to 24 sandstone bodies separated by thick marl‐rich units. A detailed analysis of nine outcrops (>900 m of sediment profiles) from the Morillo Formation of the San Vicente Group, from the upper part of the basin succession, has enabled a reappraisal of the unit. Within the Morillo Formation, sediment transport was to the NW, and a range of environments are recognized including channels, lobes and pelagic deposits. The overlying Coscojuela Formation, which partly cuts into the Morillo Formation, shows W‐directed palaeocurrents in its proximal reaches, with flows being deflected to the N along an adjacent slope. Destabilization of the adjacent carbonate platform resulted in a significant input of carbonate material into the flow. The final phases of sedimentation within the Aínsa Basin were more complex than previously suspected, probably as a result of a combination of factors, including tectonic activity, resulting in basin narrowing due to anticlinal growth, as well as encroachment and/or destabilization of the adjacent regional carbonate platforms. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

地震沉积学在滨南浊积砂岩区的研究及应用     

蒋成国  焦海燕  苗长波 《山东地质》2011,(10):23-26

运用地震沉积学的理论,使用90°相位转换和地层切片等关键技术,结合钻测井资料,对滨南地区滨682井区古近纪沙河街组3个层序的砂体分布特征和沉积体系进行了精细研究。结果表明,该区东部和东南部浊积砂体较为发育。层序I早期浊积砂体分布面积较大,中期和晚期面积较小;层序Ⅱ早期和晚期浊积砂体分布范围较大,中期很小;层序Ⅲ主要分布在南部地区。证明该方法不但简单,而且减少了穿时问题,适合楔形沉积层序的分析研究。  相似文献