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1.
K.B. Lewis 《Earth》1974,10(1):37-71
The continental terrace, defined as the sediment and rock underlying the coastal plain, the continental shelf and continental slope, has been extensively explored during the last decade using seismic techniques. Some facts and theories about its structure and formation are reviewed.The development of the continental terrace is considered in three main stages: first, the formation of the major discontinuity between continent and ocean basin; second, the deposition of sedimentary strata; and third, the Quaternary modification of the continental terrace to form the present topography.The major discontinuity may be formed either by rifting of a continent or by accretion of a large mass of contorted continental terrace and continental rise sediments to a pre-existing edge of a continent. Both types of discontinuity may be either ancient or presently forming in an orogenic area. Sedimentary strata are built generally upwards and outwards but at most places development is modified either by basement structure, by current and slump erosion or by growth of organic and diapiric structures.During the Quaternary Era the terrace has been extensively modified as a result of large fluctuations of sea level. The present wide continental shelf and deep shelf break are at most places the result of wave planation and offshore deposition during the last low sea level and during the subsequent rise of sea level. The final process at many places has been formation of a Holocene coastal plain and deposition of a prism of sediment on the inner continental shelf.Most continental terraces show evidence of continental flexure, which is the seaward tilting of land and seabed with a zero isobase, a line of no vertical movement, close to the shore. The reasons for continental flexure are discussed. The relative positions of the shore line, the zero isobase and the boundary between erosion and deposition are controlled by rates of tilting, by rates of sedimentary processes and by eustatic movements of sea level.From an assessment of the general processes operating today, some conclusions are reached about the changes in form and topography of continental terraces of the past. 相似文献
2.
南海北部狭窄陆架-断裂陆坡控制的深水沉积体系研究程度极低.以“源-渠-汇”耦合思想为指导,基于岩石学特征、测井相、地震相分析,刻画了揭阳凹陷珠海组深水扇砂体的垂向叠置和横向迁移特征,并将其形成演化划分为珠海组四段初始形成期、珠海组三段-二段发展扩大期、珠海组一段萎缩消亡期.揭阳凹陷珠海组大型盆底扇的形成受控于易剥蚀的中生界物源、多期的相对海平面快速下降、狭窄陆架-断裂陆坡的有利地貌这3个关键因素的耦合作用;在区域三级相对海平面快速下降的背景下,揭阳凹陷北侧东沙隆起富砂的下白垩统快速剥蚀,沉积物直接沿狭窄陆架区的侵蚀下切谷或小型陆架边缘三角洲的水下分流河道搬运,顺断裂坡折带或构造转换带调节,以重力流形式经峡谷水道继续搬运至下陆坡盆地形成大型海底扇. 相似文献
3.
WILLIAM B.F. RYAN 《Sedimentology》1976,23(6):791-813
Quantitative geophysical calculations which take into consideration the isostatic loading of sediment overburden, the overlying water cover, and the thermal cooling history of the continental edge, and its adjacent oceanic lithosphere, demonstrate the foundering of the margins of the western Mediterranean had already commenced in the Aquitanian stage of the early Miocene. The calculations are based on magnitudes and rates of sediment accumulation observed along a profile of three commercial boreholes into the subsurface of the continental shelf of southern France. By the time of the late Miocene (Messinian) salinity crisis, the depth of the seafloor within the Balearic basin exceeded 2.5 km. Sea-level fluctuations induced by evaporitic draw-down permitted the exposure of large tracts of the former submerged continental margins to subaerial processes. The measured magnitude of sediment removal by erosion and channel incision near the outer shelf of the modern Gulf of Lion surpasses 1 km. The subsidence history of this shelf platform south of France provides new evidence that the continental lithosphere behaves as if it is rigidly coupled to its oceanic counterpart commencing with the initial phase of the pull-apart. No major vertical fault displacements have subsequently offset their overlying crustal layers. The sedimentary shaping and construction of the margin seaward of the Rhône delta resulted in a pronounced shelf edge migration and slope progradation during the pre-salinity crisis Miocene. It has taken 5 million years of predominant upbuilding to establish a new equilibrium profile similar in cross-section to the precrisis depositional surfaces created by outbuilding. 相似文献
4.
Jean‐Pierre Larue 《第四纪科学杂志》2009,24(3):294-310
This study aims to reconstruct the Cenozoic and Pleistocene morphodynamic evolution of the Orb, a Mediterranean river which crosses all the structural units of the south Massif Central border. A geomorphological and sedimentological analysis of detrital deposits was carried out as a basis for correlating the different formations and reconstructing the palaeodrainage. Heavy minerals were used to reconstruct the main sedimentary palaeochannels since the Messinian. The successive Orb longitudinal profiles show anomalies which can be caused by structure and by interactions between fluvial dynamics and tectonics. Evidence of volcanic heavy minerals on the Faugères Mountains and in the Upper Pliocene deposits of the Languedocian piedmont demonstrates that a north–south flow took place during the Upper Pliocene. Nevertheless, a palaeo‐Orb existed at the place of the present course when the basaltic lava flows were spreading, but headward erosion did not reach them until the Upper Pleistocene, because the Orb middle and high terraces do not contain volcanic minerals sourced from the Escandorgue. The successive Orb longitudinal profiles show that headward erosion due to Pleistocene low sea levels does not reach beyond Béziers and that a tectonic hinge has functioned near the shoreline. The non‐lithologic knickpoints are explained by the Montagne Noire and Avant‐Monts uplift up until the Pleistocene. A progressive continental uplift is necessary to explain the Orb terraces staircase in the Béziers district, and the fluctuations of incision from upstream to downstream are due to laterally differential movements, which are isostatic effects of thick regressive deposits on the Gulf of Lion shelf during the cold periods. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
5.
壳幔拆离断裂活动与沉积体系响应为世界陆缘演变研究的热点,选取珠江口盆地白云凹陷壳幔拆离体系及其沉积响应开展系统性解剖.结合陆缘演变认识新进展、长电缆三维地震和钻井综合解释等揭示白云凹陷南部主控断裂带主要由4排NEE-NE向断至莫霍面的高角度铲式壳幔拆离断裂组成,裂陷期幕式活动使得白云凹陷经历了均一裂陷、拆离裂陷和断拗转换三阶段演化;均一裂陷期（下文昌组）,控洼断裂未延伸至莫霍面,主要发育断裂转换带控制下的轴向陡坡辫状河三角洲/湖相沉积体系,缓坡物源体系不甚发育;拆离裂陷期（上文昌组）,壳幔拆离断裂断至莫霍面,呈现强烈水平伸展和垂向落差,导致上盘远离断层一侧强烈旋转翘倾、抬升剥蚀成为最主要缓坡物源体系,靠近断层北侧沉降深陷成为深湖盆,上盘中段发育大型三角洲沉积;断拗转换期（恩平组）,拆离作用减弱而沉降作用显著增强,控制了北部缓坡挠曲坡折和NW-SE向推进的大型三角洲/湖相沉积体系的发育.由此,主控断裂由均一伸展到壳幔拆离伸展的构造演变导致白云凹陷上文昌组至恩平组缓坡大型三角洲、下文昌组东西轴向转换带辫状河三角洲和洼陷周边陡坡带扇三角洲砂岩三类规模储集体与湖相泥岩满盆叠置的分布格局,使其成为深水勘探向中深层拓展的主要对象. 相似文献
6.
Sonia Scarselli Guy D. H. Simpson Philip A. Allen Giorgio Minelli Lorenzo Gaudenzi 《地学学报》2007,19(1):74-81
The Marche Apennines (Italy) offer an excellent opportunity to constrain the temporal and spatial relationships between drainage network formation and tectonic activity. Using a combination of field data, seismic lines and boreholes we show that the main deformation phase took place during the Messinian when the area, affected by the Messinian sea level drop, emerged and evolved from marine to continental conditions. The results highlight that during the Messinian emersion a drainage network developed contemporaneously with an increase in tectonic activity that could be related to sea level fall and river erosion. The present‐day river system, which is dominated by transverse rivers that cut straight across the tectonic grain, is located in older Messinian palaeovalleys, even though the region was subsequently covered by water until the late Pliocene–early Pleistocene. 相似文献
7.
8.
二维沉积层序计算机模拟研究 总被引：14，自引：2，他引：12
本项研究建立了综合性的二维沉积层序模拟系统SSMS。该模拟系统由盆地的沉降过程模拟与盆地充填过程模拟两个子系统构成。盆地的沉降模拟结合了反演的沉降回剥和盆地形成的正演模型;盆地充填过程模拟综合考虑了盆地沉降、重力均衡作用、海（湖）平面升降、沉积物供给、侵蚀作用、沉积物分布和压实等因素。结合实例分析表明,该模拟系统可用于定量分析盆地构造、海（湖）平面、沉积物供给等变化对沉积层序的形成过程、几何形态及其沉积体系分布的控制作用,检验地质模型和进行预测。 相似文献
9.
《Geodinamica Acta》2013,26(6):389-400
It is difficult to explain the position and behaviour of the main karst springs of southern France without calling on a drop in the water table below those encountered at the lowest levels of Pleistocene glacio-eustatic fluctuations. The principal karst features around the Mediterranean are probably inherited from the Messinian period (“Salinity crisis”) when sea level dropped dramatically due to the closing of the Straight of Gibraltar and desiccation of the Mediterranean Sea. Important deep karst systems were formed because the regional ground water dropped and the main valleys were entrenched as canyons. Sea level rise during the Pliocene caused sedimentation in the Messinian canyons and water, under a low hydraulic head, entered the upper cave levels. The powerful submarine spring of Port-Miou is located south of Marseille in a drowned canyon of the Calanques massif. The main water flow comes from a vertical shaft that extends to a depth of more than 147 m bsl. The close shelf margin comprises a submarine karst plateau cut by a deep canyon whose bottom reaches 1,000 m bsl. The canyon ends upstream in a pocket valley without relation to any important continental valley. This canyon was probably excavated by the underground paleoriver of Port-Miou during the Messinian Salinity Crisis. Currently, seawater mixes with karst water at depth. The crisis also affected inland karst aquifers. The famous spring of Fontaine de Vaucluse was explored by a ROV (remote observation vehicle) to a depth of 308 m, 224 m below current sea level. Flutes observed on the wall of the shaft indicate the spring was formerly an air-filled shaft connected to a deep underground river flowing towards a deep valley. Outcroppings and seismic data confirm the presence of deep paleo-valleys filled with Pliocene sediments in the current Rhône and Durance valleys. In the Ardèche, several vauclusian springs may also be related to the Messinian Rhône canyon, located at about 200 m below present sea level. A Pliocene base level rise resulted in horizontal dry cave levels. In the hinterland of Gulf of Lion, the Cévennes karst margin was drained toward the hydrologic window opened by the Messinian erosional surface on the continental shelf. 相似文献
10.
Although the main events of the Messinian Salinity Crisis (MSC) are today mostly known, the exact succession of the different episodes remains unclear. This, in particular, is because (i) no drilling has reached the base of the Salt, and thus the onset of the MSC in the basins is unknown, and (ii) lateral correlations between the margins and the deep basins are missing. The Valencia Basin, which is intermediate in depth between the marginal basins and the deep basins, is an ideal location for studying the transitional domain. It displays the relationships between the polygenic erosion on the margins, the deposition of the thin Upper Evaporites bracketed by basal and top erosion surfaces in the central part of the basin, and the thick MSC sequence in the deep oceanic Provençal Basin. Early detrital deposits located below the MSC sequence of the deep basin suggest an early lowering of the sea level prior to the MSC desiccation. 相似文献
11.
沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识.沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间,与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映.在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录,而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层,它们被解释为构造高地重复隆升和溯源侵蚀的结果.最近的研究工作表明,急剧的构造沉降主要是通过细粒级河湖相沉积补偿的,广泛的砾岩进积发生在构造活动的平静期.构造驱动的山脉隆升表现为砾岩地层呈楔状体,纵向河流水系发育;重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积.从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获取重大构造变革时期的信息,也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段. 相似文献
12.
沉积盆地的地层形态、岩相类型以及空间配置样式是构造事件的重要标识，沉积序列中特征岩石组分的出现标志着毗邻造山带隆升的初始启动时间，与物源区地层单元垂向叠置序列相反或相同的岩屑组分剖面分布则是幕式构造旋回的反映，在前陆盆地中砾石层的出现被认为是冲断岩席活动的记录，而在断陷盆地和走滑拉分盆地中通常可识别出100m级的向上变粗和向上变细的旋回层，它们被解释为构造高地重复姓升和溯源侵蚀的结果，最近的研究工作表明，急剧的构造沉降主要是通过细粒级河湖相沉积补偿的，广泛的砾岩进积发生在构造活动的平静期，构造驱动的山脉隆升表现为砾岩地层呈楔状体，纵向河流水系发育；重力均衡回返所导致的山系隆升则形成以横向河流水系为主的板状砾岩沉积，从青藏高原腹地、周缘和外延海洋盆地的沉积记录中可获得取重大构造变革时期的信息，也许是解决目前有关印度与亚洲大陆碰撞、高原隆升等时性或穿时性以及限定陆内变形调节机制的一个重要手段。 相似文献
13.
A sequence of graded ophiolitic sandstones, 120 m thick (Sanguigna Formation), outcrops within the Messinian Evaporite Group in a limited area near Gabbro, Fine Basin, western Tuscany.The formation lies between fine-grained sediments laid down under a thin water-cover. The graded beds show, on the other hand, many features typical of proximal turbidites, such as amalgamated layers, scour-and-fill structures, clay flakes and lumps, top-truncated Bouma sequences. Grain-size analyses suggest that they were deposited from high-density turbidity flows.The petrographic composition and the grain fabric indicate that the feeding was from the northeast across the Fine Basin. From the inferred dimensions and depth of the basin, the mean slope should have been less than 1°. The turbidity currents probably originated at a river mouth during flood stages.The Sanguigna graded beds are compared with occurrences of shallow-water turbidites. 相似文献
14.
Along the Ligurian coast (NW Italy), Alpine‐folded and slightly metamorphosed rocks experienced fluvial to marine erosion prior to and during the base level fall associated with the Messinian salinity crisis. Following the subsequent sea‐level rise at the onset of the Pliocene, valleys incised along the coastal margins during the Messinian salinity crisis were partly filled with Pliocene marine and continental deposits. One such valley‐infill system is exposed near Ventimiglia (NW Italy). Using geological cross‐sections and geomorphological analysis we have constrained its shape and dimensions, as well as the morphology of its hinterland. The Messinian valley was very open, ∼10 km wide and probably 500 m deep. The basal unconformity between the Pliocene sediments and the underlying substratum is characterized by a smooth surface that has on either side of the palaeo‐valley a dip between 2 and 10°. The basal unconformity in the southernmost part of the palaeo‐valley roughly coincides with present‐day sea level. The hinterland of the middle Pliocene sea was characterized by kilometres‐wide valleys surrounded by mountains with a relief gentler than at present. The shapes and dimensions of the Messinian Ventimiglia valley and the relief during Pliocene times are different from those derived from comparable structures in SE France and NW Italy. We interpret this as being due to the exhumation history that the Ventimiglia region, different from the surrounding areas, experienced over the last few million years. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
15.
Jonathan D. Radley 《Geology Today》2010,26(6):226-232
The central English county of Warwickshire has been shaped by a 600 million‐year history of deposition, erosion, tectonism, continental drift, environmental change and biological evolution. The Neoproterozoic and Lower Palaeozoic rocks indicate island arc accretion, marine transgression and subduction‐related intrusive igneous activity. Upper Palaeozoic through to Triassic times witnessed mainly continental environments, as central England drifted north across the equator. Late Triassic marine transgression led to deposition of richly fossiliferous Jurassic sediments. The bedrock geology shows evidence for the influence of deep‐seated structural lineaments within the central English basement. Influenced by these structures, the modern landscape has been shaped largely by Palaeogene and Neogene uplift and erosion, further alteration by Quaternary erosion and weathering, and glacial and fluvial deposition. 相似文献
16.
古陆碰撞继之为海洋盆地关闭、山脉隆起和前陆盆地巨厚碎屑岩系的堆积。造山带的前陆地区，前身是被动陆,构造上位于较低的部位，其地质记录可以保存得相对完整。长江中下游地区，是大别造山带的前陆构造带。通过对那里沉积物形成环境，特别是物源区的分析研究，识别出震旦系至下三叠统被动陆缘沉积岩系和中三叠统至中侏罗统前陆盆地沉积岩系，据此推测大别造山带碰撞造山作用发生在中三叠世。早三叠世被动陆缘岩系和前陆盆地堆积物的空间分布，揭示出中朝与扬子两个地板之间的碰撞方式，在长江中下游地区从东到西基本是同时的。 相似文献
17.
为研究潮汐河道不同区段在流域来沙减少条件下的冲淤响应机制,以长江澄通河段为例,根据水动力特性将其划分为江阴—天生港和天生港—徐六泾两段,结合1950—2014年的水沙资料及2005—2014年的地形资料,比较两段冲淤对流域减沙的响应差异。结果表明:上游江阴—天生港段对流域减沙敏感,较快地由淤积转为冲刷;下游天生港—徐六泾段1998—2004年期间受洪季平均径流流量减小、潮汐顶托作用相对增大的影响,冲刷速率为减小趋势,2004年以后受洪季平均径流流量增大、潮汐顶托作用相对减小及流域来沙持续减少的共同影响,冲刷速率为增大趋势。使得潮汐动力对天生港—徐六泾段由促淤变为促冲的临界洪季平均径流流量为36 000 m3/s,该径流流量也是使得潮汐顶托作用在江阴—天生港段由不显著变为显著的临界流量。目前,流域减沙已加剧澄通河段整体的冲刷。 相似文献
18.
A.P. Lisitsyn 《Russian Geology and Geophysics》2009,50(4):278-298
According to recent data from seas and oceans, marine sediments have extremely uneven thicknesses varying from tens of meters to 15–20 km. Sedimentary material is localized mainly at three global levels: river–sea boundary (zero level, continental base of erosion), continental rise (3–5 km), and trenches (6–11 km). As a result of extremely rapid (“avalanche”) deposition in trenches, large amounts of organic matter accumulate in bottom sediments, thus providing their high petroleum reservoir potential. Sediments in areas of rapid sedimentation have a particular rheology, which causes them to move downslope hundreds of kilometers on the sea floor. Continental rise is a global area where gravitites accelerate, with their potential energy due to a depth difference of 3 to 5 km. Global-scale drift of sedimentary masses driven by eustatic sea level change produces very large deposition zones rich in oil and gas at the continental rise (global piedmont), i.e., at the second level. Predicted oil and gas fields of this kind have been discovered recently at sea depths over 3.5 km, which lie in stock for future development through the 21st century. 相似文献
19.
Tectonic, eustatic and environmental controls on mid-Cretaceous carbonate platform deposition, south-central Pyrenees, Spain 总被引：2，自引：0，他引：2
Cenomanian–Turonian strata of the south‐central Pyrenees in northern Spain contain three prograding carbonate sequences that record interactions among tectonics, sea level, environment and sediment fabric in controlling sequence development. Sequence UK‐1 (Lower to Upper Cenomanian) contains distinct lagoonal, back‐margin, margin, slope and basin facies, and was deposited on a broad, flat shelf adjacent to a deep basin. The lack of reef‐constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. Sequence UK‐2 (Upper Cenomanian) contains similar shallow‐water facies belts, but syndepositional tectonic modification of the margin resulted in a steep slope and deposition of carbonate megabreccias. Sequence UK‐3 (Lower to Middle Turonian) records a shift from benthic to pelagic deposition, as the shallow platform was drowned in response to a eustatic sea‐level rise, coupled with increased organic productivity. Sequences UK‐1 to UK‐3 are subdivided into lowstand, transgressive and highstand systems tracts based on stratal geometries and facies distribution patterns. The same lithologies (e.g. megabreccias) commonly occur in more than one systems tract, indicating that: (1) the depositional system responded to more than just sea‐level fluctuations; and (2) similar processes occurred during different times throughout sequence development. These sequences illustrate the complexity of carbonate platform dynamics that influence sequence architecture. Rift tectonics and flexural subsidence played a major role in controlling the location of the platform margin, maintaining a steep slope gradient through syndepositional faulting, enhancing slope instability and erosion, and influencing depositional processes, stratal relationships and lithofacies distribution on the slope. Sea‐level variations (eustatic and relative) strongly influenced the timing of sequence and parasequence boundary formation, controlled changes in accommodation and promoted platform drowning (in conjunction with other factors). Physico‐chemical and climatic conditions were responsible for reducing carbonate production rates and inducing platform drowning. Finally, a mud‐rich sediment fabric affected platform morphology, growth geometries (aggradation vs. progradation) and facies distribution patterns. 相似文献
20.
Julien Gargani 《Comptes Rendus Geoscience》2004,336(10):901-907
The isostatic response to erosion and Mediterranean Sea unloading of the Messinian Rhone has been quantified. The consequences of the isostatic rebound on fluvial dynamic have been analysed considering the Messinian Rhone profile. To cite this article: J. Gargani, C. R. Geoscience 336 (2004). 相似文献