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1.
近代黄河三角洲的沉积特征* 总被引：9，自引：4，他引：5
本文论述了近代黄河三角洲沉积物的数量特征、粒度特征及共分布、结构与构造特征,认为:1.各期亚三角洲的淤积厚度、速率和陆地淤积率都与亚三角洲的建造历时及废止方式有关,淤积厚度有共最大限度;2.沉积颗粒均细于0.25mm级,粉砂粘土占优势,无推移质段。Mz(φ)值与δf成正比,与Kg成反比;3.沉积构造与沉积水动力及颗粒大小有关,沉积物的分布与结构反映了三角洲建造的基本特征。 相似文献
2.
黄河口泥沙淤积估算问题和方法——以钓口河亚三角洲为例 总被引：11，自引：1，他引：10
以往在黄河三角洲沉积量的估算中,对沉积物干容重和计算边界等问题不够重视,导致计算结果存在明显出入。本项研究通过广泛收集资料和大量采样分析得到了多种沉积环境下沉积物干容重的计算模型,结合三角洲沉积结构分析和利用地形测量数据,计算了黄河口钓口河流路时期亚三角洲不同时期的沉积量。其中1965年至1974年间钓口河亚三角洲前缘坡脚以内的总淤积量为71.0亿t。其平均干容重为1.36g/cm3。这一干容重用于估算其它亚三角洲沉积量不会造成明显误差。认为忽略三角洲下松软沉积层的压实沉降、三角洲平原相和前缘相中粘性土与非粘性土干容重的差别以及来沙量的测量误差对计算结果影响较小。 相似文献
3.
环境磁学方法作为沉积记录研究的重要手段,已在黄土、湖泊和陆架沉积物中得到广泛应用,但将此方法应用于潮滩沉积环境的研究并不多。因此,通过测量黄河三角洲潮滩YDZ1柱样沉积物磁学和粒度参数,结合AMS14C测年数据,对末次冰盛期后黄河三角洲潮滩沉积物磁性特征与沉积环境进行分析。结果表明:以假单畴(PSD)~多畴(MD)晶粒为主的亚铁磁性矿物主导了潮滩沉积物的磁性特征,磁学参数中的χARM,χARM/SIRM和χARM/χ可视为粘土(4μm)或细粒级组分(32μm)含量的代用指标。潮滩沉积相序自上而下为泛滥平原相、河流相、三角洲前缘相、浅海相、潮坪相和河流相,沉积环境表现为强(陆相)、弱(海相)、强(陆相)的演变过程。 相似文献
4.
黄河口不同粒度泥沙沉积与扩散分析 总被引：1，自引：0，他引：1
本文采集和收集大量黄河三角洲沉积物剖面和钻孔泥沙粒度资料以及黄河口来沙粒度组成数据,定量研究了黄河口泥沙的沉积与扩散特征。结果显示黄河口来沙以粉砂为主,黏土次之,砂最少,年均中值粒径无长期变化趋势。黄河三角洲平原相泥沙与来沙的黏土、粉砂和砂含量无显著差异;前缘相泥沙比来沙的黏土含量较低,砂含量较高;前三角洲相泥沙比来沙的黏土含量明显提高,砂和粉砂含量显著降低。计算了一个亚三角洲分组粒径泥沙的沉积量和扩散量,发现黄河三角洲平原和前缘拦截了来沙中绝大部分砂颗粒、一半以上的黏土颗粒和近3/4的粉砂颗粒,但是向远海扩散的泥沙中粉砂含量超过50%。由于粉砂含量较大,扩散入海的泥沙在近距离内大量沉积在前三角洲上。 相似文献
5.
渤海莱州湾南岸潍河-弥河三角洲:沉积序列和沉积格架 总被引：9，自引：2，他引：7
潍河-弥河三角洲是一个由多条河流共同塑造的三角洲。前三角洲黏土质粉砂是各河流共同贡献的结果;每条河口之外形成各自的三角洲前缘,主要由极细砂组成;河口间湾沉积物是两条相邻河流共同塑造的,主要为黏土质粉砂。由于河口位置的侧向摆动,三角洲前缘极细砂和河口间湾黏土质粉砂会交替出现。7000a B. P. 以来向海进积20~55km,在海岸附近三角州沉积物厚度超过20m。 相似文献
6.
分析黄河口钓口河亚三角洲不同时期泥沙沉积速率和水沙条件变化,发现来沙输沙率是影响黄河三角洲沉积速率的主要因素,随输沙率增加三角洲泥沙沉积速率增大.来水流量和来沙粒度组成变化对沉积速率的影响不明显.还发现来水含沙量与三角洲泥沙淤积占来沙的比例(沉积比)之间为双值关系,在某一含沙量时沉积比达最大值.对比显示,在河口河道畅通,沙嘴突出时期,三角洲泥沙沉积比反而比河口改道初期大,意味着集中水流入海可能降低海流带走泥沙的比例.另外,根据前三角洲的地形测量资料分析发现,进入远海的泥沙随距离增加呈指数递减.对黄河口这些独特的泥沙扩散规律发生机理进行了深入分析. 相似文献
7.
潍河-弥河三角洲是一个由多条河流共同塑造的三角洲。前三角洲黏土质粉砂是各河流共同贡献的结果;每条河口之外形成各自的三角洲前缘,主要由极细砂组成;河口间湾沉积物是两条相邻河流共同塑造的,主要为黏土质粉砂。由于河口位置的侧向摆动,三角洲前缘极细砂和河口问湾黏土质粉砂会交替出现。7000aB．P．以来向海进积20～55km,在海岸附近三角州沉积物厚度超过20m。 相似文献
8.
近20年辽河三角洲地貌演化 总被引：7，自引：1，他引：6
运用钻探和浅地层探测等最新调查成果,对近20年的辽河三角洲潮流沉积进行了研究.根据不同时期水深地形和卫星影像资料对比分析了现代辽河三角洲潮流地貌变化.现代辽河三角洲的沉积主体位于双台子河口.研究区10 m深度内的地层主要包括:潮滩相、潮道相和浅海相沉积,其下为古三角洲相.潮滩相沉积物以砂和粉砂为主,分选中等,跳跃和悬浮组分各占50%左右:浅海相和潮道相沉积物主要为软弱的粘土质粉砂和粉砂质粘土,以悬浮组分为主.全新世以来至1896年,研究区为古辽河、古大凌河和绕阳河之间的小海湾.1896年,双台子河被人工开挖为分洪河道以来,口门外形成盖州滩等潮滩,并快速发育.1958年,双台子河建闸后,人海径流量和输沙量减小.目前.双台子河口整体处于淤积状态,潮滩面积不断增加,整体向南、西、北3个方向扩展.潮滩最大淤进速率为87～683 m/a,平均淤积速率为0.189 m/a.潮滩东侧局部发生侵蚀,平均侵蚀速率为0.122 m/a.潮道面积缩小,具有向西、向北迁移的趋势,最大迁移速率为48～200m/a.双台子河口地貌发育受径流、海洋动力和人类活动的影响,沉积物的主要来源由双台子河河流输沙演变为潮流和沿岸流输沙. 相似文献
9.
黄河长江珠江三角洲近30年海平面上升趋势及2030年上升量预测 总被引：44，自引：3，他引：44
黄河、长江和珠江三角洲由于地面沉降等原因,过去30年的相对海平面上升率远大于全球或全国海平面上升率（约1.5mm/a）。下一世纪,根据IPCC的最佳估计,至2030年全球海平面将上升18cm。我国三大三角洲,根据目前地面沉降情况、发展趋势及政府的控制措施,估计2030年相对海平面上升量老黄河三角洲（天津地区）为60cm,现代黄河三角洲（山东省东营市地区）为30—35cm,长江三角洲（上海地区）为30—40cm,珠江三角洲20—25cm,以上估计数可供沿海有关决策部门制订今后长远发展规划及拟订政策时的参考。 相似文献
10.
通过对海南岛三亚地区铁炉港海湾TLG01钻孔沉积物的AMS 14C和OSL测年,以及对地层岩性特征、亮度、粒度、海生贝壳、有孔虫丰度等进行研究,发现全新世海相层较薄,以砂质潮坪相沉积为主;而下伏晚更新世海相层厚度超过38 m,OSL测年结果显示为MIS-5e及MIS-5d沉积。晚更新世海进―海退系列自下而上依次为砂质潮坪―潮下带―泥质潮坪―砂质潮坪,其中可见较深水的软体动物。MIS-5e细粒的粉砂黏土体积分数先陡增、后缓降,结合粒度及有孔虫丰度、亮度L*等指标,判断MIS-5e初期为最高海平面时期,水深较大,其后海平面逐渐降低;沉积物中陆源粗砂的体积分数不断增加,显示进入了MIS-5d相对低海面时期。MIS-1及MIS-5沉积物粒度三角图,分别与湛江海岛潮间带及不同深度南海表层沉积物同类沉积环境有较好的对照,指示2类不同水深的海相环境。 相似文献
11.
Sediment compaction rates and subsidence in deltaic plains: numerical constraints and stratigraphic influences 总被引：2，自引：0，他引：2
Natural sediment compaction in deltaic plains influences subsidence rates and the evolution of deltaic morphology. Determining compaction rates requires detailed knowledge of subsurface geotechnical properties and depositional history, neither of which is often readily available. To overcome this lack of knowledge, we numerically forward model the incremental sedimentation and compaction of stochastically generated stratigraphies with geotechnical properties typical of modern depositional environments in the Mississippi River delta plain. Using a Monte Carlo approach, the range of probable compaction rates for stratigraphies with compacted thicknesses <150 m and accumulation times <20 kyr. varies, but maximum values rarely exceed a few mm yr?1. The fastest compacting stratigraphies are composed primarily of peat and bar sand, whereas the slowest compacting stratigraphies are composed of prodelta mud and natural levee deposits. These results suggest that compaction rates can significantly influence vertical and lateral stratigraphic trends during deltaic evolution. 相似文献
12.
S. van Asselen 《Basin Research》2011,23(2):239-255
Provision of accommodation space for aggradation in Holocene deltaic basins is usually ascribed to eustatic sea‐level rise and/or land subsidence due to isostasy, tectonics or sediment compaction. Whereas many Holocene deltas contain peat, the relative contribution of peat compaction to total subsidence has not yet been quantified from field data covering an entire delta. Subsidence due to peat compaction potentially influences temporal and spatial sedimentation patterns, and therefore alluvial architecture. Quantification of the amount and rate of peat compaction was done based on (1) estimates of the initial dry bulk density of peat, derived from a relation between dry bulk density and organic‐matter content of uncompacted peat samples and (2) radiocarbon‐dated basal peat used to reconstruct initial levels of peat formation of currently subsided peat samples. In the Rhine‐Meuse delta, peat compaction has contributed considerably to total basin subsidence. Depending on the thickness of the compressible sequence, weight of the overburden and organic‐matter content of peat, subsidence of up to approximately 3 m in a 10‐m thick Holocene sequence has been calculated. Calculated local subsidence rates of peat levels are up to 0.6 mm year?1, averaged over millennia, which are twice the estimated Holocene‐averaged basin subsidence rates of 0.1–0.3 mm year?1 in the study area. Higher rates of subsidence due to compaction, on the order of a few mm year?1, occur over decades to centuries, following a substantial increase in effective stress caused by sediment loading. Without such an increase in effective stress, peat layers may accumulate for thousands of years with little compaction. Thus, the contribution of peat compaction to total delta subsidence is variable in time. Locally, up to 40% of total Holocene accommodation space has been provided by peat compaction. Implications of the large amount of accommodation space created by peat compaction in deltaic basins are: (1) increased sediment trap efficiency in deltas, which decelerates delta progradation and enhances the formation of relatively thick clastic sequences and (2) enhanced local formation of thick natural levees by renewing existing accommodation space. 相似文献
13.
Palaeovalleys in foreland ramp settings: what happens as accommodation decreases down dip? 
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下载免费PDF全文 Recent advances in our understanding of palaeovalleys are largely guided by examples from passive margins, in which accommodation increases down depositional dip. This study tests these models against a dataset from the Pennsylvanian Breathitt Group of the central Appalachian foreland basin, USA. This fluvio‐deltaic succession contains extensive erosionally based fluvio‐estuarine sand bodies that can be tracked over 80 km down depositional dip from a proximal zone of high accommodation close to the orogenic margin to a distal, lower accommodation zone close to the cratonic margin of the basin. The sand bodies are up to 25 m thick, multi‐storey and characterized in their lower parts by strongly amalgamated storeys containing sandy fluvial to estuarine bar accretion elements, and in their middle to upper parts by more fully preserved storeys up to 10 m thick and laterally extensive over 100s of metres. The upper storeys include abandonment channel‐fills of heterolithic marine or marginal marine deposits or muddy to sandy point‐bar elements. Three major regional‐scale architectures include: (i) Tabular sand bodies that everywhere incise open marine prodelta and mouth bar facies and are interpreted as palaeovalleys formed during falling stage and lowstand systems tracts, when eustatic sea‐level fall outpaced tectonic subsidence across the entire study area. (ii) Sand bodies that incise genetically related floodplain lake and/or bay‐fill minor mouth bar deposits up depositional dip and open marine prodelta and mouth bar facies down dip. These stacked distributary channel deposits map down dip into palaeovalleys and formed when up dip subsidence rate resulted in positive, but reduced rate of accommodation creation, while lower tectonic subsidence rate down‐dip resulted in incision. (iii) Sand bodies that incise genetically related floodplain, lake and/or bay‐fill minor mouth bars up dip and pass down‐dip into genetically related unconfined floodplain, prodelta and mouth bar deposits. These sand bodies represent stacked distributary channel fills and channel amalgamation was the product of high rates of lateral migration, typical of the behaviour of channels above their backwater reach. Case (2) sand bodies demonstrate that in rapidly subsiding foreland basins, cross‐shelf palaeovalleys may form down depositional dip from aggradational, distributive fluival strata. Additionally, the genetic relationship between stacked distributary channels and palaeovalleys supports recent models for palaeovalley formation that emphasize diachronous, cut‐and‐fill during falling stage and lowstands of relative sea level. 相似文献
14.
Extensive studies of land subsidence in the Yellow River Delta (YRD) have identified sediment consolidation and compaction as important contributors to geologic processes. Although previous studies were informed by detailed knowledge of subsurface getechnical properties and depositional history, geotechnical data that are sufficient for detailed modeling are still unavailable for much of the delta. To overcome this limitation, we use a modified Monte Carlo method to model the incremental sedimentation and compaction in the delta and identify the stratigraphic characteristics of all abandoned lobes in the delta on a short-term scale of decades. A Digital Elevation Model (DEM) of the thickness of the delta plain is generated based on a contour map of the delta using Geographic Information Systems technology. Combining our simulation results and the DEM creates an overall view of the delta’s temporal and spatial land subsidence characteristics. Most data from the 152 boreholes show properties of soft soil, which is saturated and compressible. Our data confirm that the most rapidly compacting strata contain 100% soft soil. Research on settlement from soft soil compaction is particularly important because of the widespread distribution of soft soil in the YRD. 相似文献
15.
Luigi Bruno Bruno Campo Andrea Di Martino Wan Hong Alessandro Amorosi 《Basin Research》2019,31(3):621-639
Peat horizons are characteristic features of delta plains worldwide. In this study, we tested the use of peat‐based correlations to assess the deformation of Holocene strata in the Po coastal plain (Northern Italy). The Holocene stratigraphy, about 30 km inland from the modern coastline consists of a peat‐bearing, estuarine and deltaic succession, up to 23 m thick. Through the analysis of 31 core data and 100 piezocone penetration tests, we identified and mapped three 10–40 cm‐thick peat layers (T1–T3) dated to 6.6–5.8, 5.5–5.0 and 3.3–2.7 cal kyr BP respectively. These peat horizons were found to be suitable stratigraphic markers within the Holocene succession over an area of about 200 km2. The mid‐late Holocene palaeogeography, reconstructed through high‐resolution peat correlation, supported by 72 radiocarbon dates, highlights a typical upper delta plain environment, with ribbon‐shaped distributary channels and swamp interdistributary areas. Peat layers are inclined towards E‐NE with gradients that increase downsection from ~0.016% (T3) to 0.021% (T1). The gradient of the oldest peat horizon is one order of magnitude larger than the slope of the modern delta plain (~0.0025%). We infer that peat horizons accumulated during periods of low sediment supply mainly controlled by autogenic processes and were deformed after deposition. Differential compaction of underlying sedimentary strata and recent tectonic activity of the buried Apenninic thrust systems are the most likely drivers of strata deformation. Based on isochore maps, we document that higher sedimentation rates in topographically depressed areas compensated, in part at least, the ongoing deformation, keeping unaltered the topographic gradient and the depositional environment. This study demonstrates that peat‐based correlation and mapping can shed lights on the mechanisms of strata accumulation and deformation in deltaic settings, constituting a robust basis for reconstructing delta evolution. 相似文献
16.
Multiscale simulation of fluvio‐deltaic stratigraphy was used to quantify the elements of the geometry and architectural arrangement of sub‐seismic‐scale fluvial‐to‐shelf sedimentary segments. We conducted numerical experiments of fluvio‐deltaic system evolution by simulating the accommodation‐to‐sediment‐supply (A/S) cycles of varying wavelength and amplitude with the objective to produce synthetic 3‐D stratigraphic records. Post‐processing routines were developed in order to investigate delta lobe architecture in relation to channel‐network evolution throughout A/S cycles, estimate net sediment accumulation rates in 3‐D space, and extract chronostratigraphically constrained lithosomes (or chronosomes) to quantify large‐scale connectivity, that is, the spatial distribution of high net‐to‐gross lithologies. Chronosomes formed under the conditions of channel‐belt aggradation are separated by laterally continuous abandonment surfaces associated with major avulsions and delta‐lobe switches. Chronosomes corresponding to periods in which sea level drops below the inherited shelf break, that is, the youngest portions of the late falling stage systems tract (FSST), form in the virtual absence of major avulsions, owing to the incision in their upstream parts, and thus display purely degradational architecture. Detailed investigation of chronosomes within the late FSST showed that their spatial continuity may be disrupted by higher‐frequency A/S cycles to produce “stranded” sand‐rich bodies encased in shales. Chronosomes formed during early and late falling stage (FSST) demonstrate the highest large‐scale connectivity in their proximal and distal areas, respectively. Lower‐amplitude base level changes, representative of greenhouse periods during which the shelf break is not exposed, increase the magnitude of delta‐lobe switching and favour the development of system‐wide abandonment surfaces, whose expression in real‐world stratigraphy is likely to reflect the intertwined effects of high‐frequency allogenic forcing and differential subsidence. 相似文献
17.
Lacustrine deposits of the Malanzán Formation record sedimentation in a small and narrow mountain paleovalley. Lake Malanzán was one of several water bodies formed in the Paganzo Basin during the Late Carboniferous deglaciation. Five sedimentary facies have been recognized. Facies A (Dropstones-bearing laminated mudstones) records deposition from suspension fall-out and probably underflow currents coupled with ice-rafting processes in a basin lake setting. Facies B (Ripple cross-laminated sandstones and siltstones) was deposited from low density turbidity currents in a lobe fringe environment. Facies C (Massive or graded sandstones) is thought to represent sedimentation from high and low density turbidity currents in sand lobes. Facies D (Folded sandstones and siltstones) was formed from slumping in proximal lobe environments. Facies E (Wave-rippled sandstones) records wave reworking of sands supplied by turbidity currents above wave base level.The Lake Malanzán succession is formed by stacked turbidite sand lobe deposits. These lobes were probably formed in proximal lacustrine settings, most likely relatively high gradient slopes. Paleocurrents indicate a dominant direction from cratonic areas to the WSW. Although the overall sequence shows a regressive trend from basin fine-grained deposits to deltaic and braided fluvial facies, individual lobe packages lack of definite vertical trends in bed thickness and grain size. This fact suggests aggradation from multiple-point sources, rather than progradation from single-point sources. Sedimentologic and paleoecologic evidence indicate high depositional rate and sediment supply. Deposition within the lake was largely dominated by event sedimentation. Low diversity trace fossil assemblages of opportunistic invertebrates indicate recolonization of event beds under stressed conditions.Three stages of lake evolutionary history have been distinguished. The vertical replacement of braided fluvial deposits by basinal facies indicates high subsidence and a lacustrine transgressive episode. This flooding event was probably linked to a notable base level rise during postglacial times. The second evolutionary stage was typified by the formation of sand turbidite lobes from downslope mass-movements. Lake history culminates with the progradation of deltaic and braided fluvial systems 相似文献
18.
Pennsylvanian carbonate platforms adjacent to deltaic systems in an active marine foreland basin (Escalada Fm., Cantabrian Zone,NW Spain) 下载免费PDF全文
下载免费PDF全文 Juan Ramón Bahamonde Oscar Merino‐Tomé Giovanna Della Porta Elisa Villa 《Basin Research》2015,27(2):208-229
The Pennsylvanian marine foreland basin of the Cantabrian Zone (NW Spain) is characterized by the unique development of kilometre‐size and hundred‐metre‐thick carbonate platforms adjacent to deltaic systems. During Moscovian time, progradational clastic wedges fed by the orogen comprised proximal alluvial conglomerates and coal‐bearing deltaic sequences to distal shelfal marine deposits associated with carbonate platforms (Escalada Fm.) and distal clay‐rich submarine slopes. A first phase of carbonate platform development (Escalada I, upper Kashirian‐lower Podolskian) reached a thickness of 400 m, nearly 50 km in width and developed a distal high‐relief margin facing a starved basin, nearly 1000‐m deep. Carbonate slope clinoforms dipped up to 30° and consisted of in situ microbial boundstone, pinching out downslope into calciturbidites, argillaceous spiculites and breccias. The second carbonate platform (Escalada II, upper Podolskian‐lower Myachkovian) developed beyond the previous platform margin, following the basinward progradation of siliciclastic deposits. Both carbonate platforms include: (1) a lower part composed of siliciclastic‐carbonate cyclothems characterized by coated‐grain and ooid grainstones; and (2) a carbonate‐dominated upper part, composed of tabular and mound‐shaped wackestone and algal‐microbial boundstone strata alternating at the decametre scale with skeletal and coated‐grain grainstone beds. Carbonate platforms initiated in distal sectors of the foreland marine shelf during transgressions, when terrigenous sediments were stored in the proximal part, and developed further during highstands of 3rd‐order sequences in a high‐subsidence context. During the falling stage and lowstand systems tracts, deltaic systems prograded across the shelf burying the carbonate platforms. Key factors involved in the development of these unique carbonate platforms in an active foreland basin are: (1) the large size of the marine shelf (approaching 200 km in width); (2) the subsidence distribution pattern across the marine shelf, decreasing from proximal shoreline to distal sectors; (3) Pennsylvanian glacio‐eustacy affecting carbonate lithofacies architecture; and (4) the environmental conditions optimal for fostering microbial and algal carbonate factories. 相似文献