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1.
The Northern Adriatic Sea is a shallow and very flat shelf area located between the northern Apennines, the southern Alps and the Dinarides; its present day physiography is the result of the filling of a relatively deep Quaternary foredeep basin, developed due to the northeastward migration of the Apennine chain. Multichannel seismic profiles and well data have allowed documenting the stratigraphic architecture, the depositional systems and the physiographic evolution of the Northern Adriatic sea since early Pliocene time. In particular, three main depositional sequences bounded by regional unconformities were recognized. The Zanclean Sequence 1 documents first the drowning of late Messinian incised valleys and then the southward progradation of a shelf-slope system, which is inferred to be related to a tectonic phase of the Apenninic front. The Piacenzian-Gelasian Sequence 2 records a relatively rapid transgressive episode followed by minor southward progradation; the top of the sequence is associated with a major late Gelasian drowning event, linked to the NE-ward migration of the Apennine foredeep. The Calabrian to upper Pleistocene Sequence 3 testifies the infilling of accommodation previously created by the late Gelasian drowning event, and it initially accumulated in deep-water settings and then in shallow-water to continental settings. The upper part of Sequence 3, consisting of the paleo-Po deltaic system, is composed of seven high-frequency sequences inferred to record late Quaternary glacio-eustatic changes. These high-frequency sequences document the stepwise filling of the remaining accommodation, resulting in the development of the modern shelf. 相似文献
2.
Structural analysis of the Indian Merge 3D seismic survey identified three populations of normal faults within the Exmouth Sub-basin of the North West Shelf volcanic margin of Australia. They comprise (1) latest-Triassic to Middle Jurassic N-NNE-trending normal faults (Fault Population I); (2) Late Jurassic to Early Cretaceous NE-trending normal faults (Fault Population II); and (3) latest-Triassic to Early Cretaceous N-NNE faults (Fault Population III). Quantitative evaluation of >100 faults demonstrates that fault displacement occurred during two time periods (210–163 and 145–138 Ma) separated by ∼20 Myr of tectonic quiescence. Latest Jurassic to Early Cretaceous (145–138 Ma) evolution comprises magmatic addition and contemporaneous domal uplift ∼70 km wide characterised by ≥ 900 m of denudation. The areally restricted subcircular uplift centred on the southern edge of the extended continental promontory of the southern Exmouth Sub-basin supports latest Jurassic mantle plume upwelling that initiated progradation of the Barrow Delta. This polyphase and bimodal structural evolution impacts current hydrocarbon exploration rationale by defining the nature of latest Jurassic to Early Cretaceous fault nucleation and reactivation within the southern Exmouth Sub-basin. 相似文献
3.
Reconstructions of the Albian to Campanian foreland basin adjacent to the northern Canadian Cordillera are based on outcrop and well log correlations, seismic interpretation, and reconnaissance-level detrital zircon analysis. The succession is subdivided into two tectonostratigraphic units. First is an Albian tectonostratigraphic unit that was deposited on the flexural margin of a foreland basin. At the base is a shallow marine sandstone interval that was deposited during transgressive reworking of sediment from cratonic sources east of the basin that resulted in a dominant 2000–1800 Ma detrital zircon age fraction. Subsequent deposition in a west-facing muddy ramp setting was followed by east-to-west shoreface progradation into the basin.Near the Albian–Cenomanian boundary, regional uplift and exhumation resulted in an angular unconformity at the base of the Cenomanian–Campanian tectonostratigraphic unit. Renewed subsidence in the Cenomanian resulted in deposition of organic-rich, radioactive, black mudstone of the Slater River Formation in a foredeep setting. Cenomanian–Turonian time saw west-to-east progradation of a shoreface-shelf system from the orogenic margin of the foreland basin over the foredeep deposits. Detrital zircon age peaks of approximately 1300 Ma, 1000 Ma, and 400 Ma from a Turonian sample are consistent with recycling of Mississippian and older strata from the Cordillera west of the study area, and show that the orogen-attached depositional system delivered sediment from the orogen to the foreland basin. A near syndepositional detrital zircon age of ca. 93 Ma overlaps with known granitoid ages from the Cordillera. After the shelf system prograded across the study area, subsequent pulses of subsidence and uplift resulted in dramatic thickness variations across an older structural belt, the Keele Tectonic Zone, from the Turonian to the Campanian.The succession of depositional systems in the study area from flexural margin to foredeep to orogenic margin is attributed to coupled foreland propagation of the front of the Cordilleran orogen and the foreland basin. Propagation of crustal thickening and deformation toward the foreland is a typical feature of orogens and so the distal to proximal evolution of the foreland basin should also be considered as typical. 相似文献
4.
The northeastern shelf margin of the South China Sea(SCS) is characterized by the development of large scale foresets complexes since Quaternary. Based on integral analysis of the seismic, well logging and paleontological data, successions since ～3.0 Ma can be defined as one composite sequence, consist of a set of regional transgressive to regressive sequences. They can be further divided into six 3 rd order sequences(SQ0–SQ5) based on the Exxon sequence stratigraphic model. Since ～1.6 Ma, five sets of deltaic systems characterized by development of wedge-shaped foresets complexes or clinoforms had been identified. High-resolution seismic data and the thick foresets allowed further divided of sub-depositional sequences(4 th order) of regression to transgression, which is basically consistent with published stacked benthic foram O-isotope records. Depositional systems identified in the study area include deltaic deposits(inner-shelf deltas and shelf-edge deltas), incised valleys, and slope slumping massive deposits. Since ～1.6 Ma, clinoforms prograded from the southern Panyu Lower Uplift toward the northern Baiyun Depression, shelf slope break migrated seaward, whereas the shelf edge of SQ0 migrated landward. The development of incised valleys in the continental shelf increased upward,especially intensive on the SB3 and SB2. The slumping massive deposits increased abruptly since SB2, which corresponds to the development of incised valleys. The evolution of depositional systems of continental slope mainly controlled by the combined influence of sea level changes, tectonic movements, sediment supply and climate changes. Since ～3.0 Ma, relative sea level of the northern SCS had been experienced transgression(～3.0 Ma BP) to regression(～1.6 Ma BP). The regional regression and maximum transgressions of the composite sequences were apparently enhanced by uplift or subsidence related to tectono-thermal events. In addition,climatic variations including monsoon intensification and the mid-Pleistocene transition may have enhanced sediment supply by increasing erosion rate and have an indispensable influence on the development of the incised valleys and 5 sets of deltaic systems since ～1.6 Ma. 相似文献
5.
晚新生代西太平洋通过水文循环和碳循环两类关键过程,对区域乃至全球气候变化产生深刻的影响。本文从上新世以来西太暖池及其主流系演化、晚第四纪北太平洋中层水演化和白令海峡开合、第四纪中国东部陆架环境演化以及新生代亚太沉积物源-汇过程与碳埋藏等方面,综述了西太平洋古海洋环境演化过程与机制。上新世以来西太暖池与印尼贯穿流的演化过程伴随构造运动而阶段性地发生,但其在轨道时间尺度上演化的细节过程并不清晰,尚未形成系统性认识。北太平洋中层水以及白令海峡开合等关键高纬过程在冰期旋回中发生了显著变化,并与低纬过程之间存在遥相关。第四纪中国东部陆架环境演化主要受控于海平面变化以及与低纬过程相关联的热量与物质传输,在此背景下,中国东部陆架形成了富有机碳的泥质沉积体系。构造隆升和亚洲季风驱动下的亚洲大陆与邻洋的沉积物源-汇过程具有显著的碳汇效应,可能在大气CO2浓度（${p_{{\rm{C}}{{\rm{O}}_2}}} $）冰期旋回和新生代气候变冷中发挥重要作用。就西太平洋古海洋环境演化过程与机制中若干关键科学问题开展深入和系统研究,不仅可为建立气候变化的低纬驱动理论提供支撑,也可为更好认识我国陆架环境变化规律以及碳汇潜力提供科学依据。 相似文献
6.
《Marine Geology》2001,172(3-4):331-358
Analyses of over 6600 km of reflection seismic profiles on the northern continental margin of the South China Sea permit the recognition of four Quaternary high-frequency type 1 sequences of the 4th order, deposited during the past ca. 690 kyr. At the present-day shelf edge, only lowstand systems tracts characterised by a prograding clinoformal internal reflection pattern are preserved. The prograding complexes can be considered as regressive units accumulated during relative sea-level falls. They exhibit internal discontinuities which might point to minor sea-level fluctuations of the 5th order. A preliminary regional relative sea-level curve for the past 630 kyr is established using the present positions of the delta fronts mapped. The neotectonics curve derived by subtracting eustatic sea-level changes from the relative sea-level curve shows that the depths of the delta fronts today are controlled primarily by regional tectonic movements and the global sea-level.Our seismo-stratigraphic interpretation documents that the area off Hong Kong and around the Dongsha Islands experienced two uplift episodes during the past 5 ma, namely at the Miocene/Pliocene boundary and at the end of the lower Middle Pleistocene, respectively. These uplift events which are centred on the Dongsha Rise led to its subaerial exposure and to the erosion of the Pliocene and most of the Pleistocene strata. The change from thermal subsidence of the continental margin initiated at the end of the drift phase to the phase of magmato-tectonic uplift was caused by a reorientation of the tectonic regime.The Recent depositional environment on the northern continental margin of the South China Sea is dominated by sediment accumulation within the inner shelf and the Zhujiang (Pearl River) estuary. The outer shelf and upper slope, especially around the Dongsha Islands, are characterised by bypass of terrigenous material.The sedimentary column in the deepsea basin has a thickness of more than 2 km and comprises 14 depositional units starting with terrestrial rift deposits. It overlies oceanic as well as transitional crust. 相似文献
7.
The paper focuses on the characteristics of faulting and magmatism of the Okinawa Trough and the relation between them.En-echelon grabens are ranked oblique to the continental shelf edge uplift,and the Longwang uplift,the rifting block ridge in the northern segment and the“Mianhua uplift”in the southern segment have possibly preserved characteristics of volcanism and magmatism occurring with those rifting phases.The clockwise rotation of the southern Ryukyu Islands,driven by collision between Luzonand Taiwan,has played a key role in the crustal oceanization,enhancing the crustal extension of the southern segment and inducing volcanic magmatism in those grabens,among which the Yaeyama graben is a typical example of the presence of oceanic crust.Faulting and magmatism were mainly migrating towards the island are asymmetrically.The crustal oceanization of the Okinawa Trough is difficultly interpreted by the linear magnetic anomaly model,which is fit for the symmetric spreading of the mid-oceanic ridges. 相似文献
8.
A. Zabanbark 《Oceanology》2012,52(4):513-525
The North Sea basin occupies a spacious depression almost isometric in shape. In the west and northwest, the basin is bordered by the continental crust consolidated during the Precambrian, Caledonian, and Hercynian orogenic epochs, which now forms epiplatformal orogenic structures. They are represented by the London-Brabant uplift and the Arden massif in the southwest and south and the Baltic Shield in the east and northeast. The North Sea basin may be considered as an ancient aulacogen that was transformed in the Early Mesozoic into a complex system of continental rifts and grabens. The sedimentary cover of the basin is represented by a thick (8.5?C12.5 km) Ordovician-Quaternary sequence. Oil and gas generation in the sedimentary cover of the basin is likely connected with four main productive sequences: the coaliferous Upper Carboniferous (Westphalian), the subsalt Zechstein, the Jurassic-Lower Cretaceous (Lotharingian, Toarcian, Kimmeridgian, and Weldian bituminose shales), and the shaly Cenozoic. The large oil and gas reserves in the North Sea??s sedimentary cover (over 280 fields) implies that the above-mentioned sequences have realized their oil-generating potential. The present-day position of the main oil and gas generation zones in the sedimentary section of the North Sea explains the distribution of the oil and gas fields through the basin from the genetic standpoint. The petroleum resource potential of the basin is still significant. In this regard, most promising are the spacious shelf areas, turbidite sediments, deep Paleozoic sequences, and continental slopes in the northern part of the basin, which remains insufficiently investigated. 相似文献
9.
台湾海峡地区新生代的构造演化 总被引：9，自引：1，他引：9
根据采集反射剖面,结合区域地质资料,分析了晋江凹陷、九龙江凹陷、新竹凹陷、台中凹陷和台湾凹陷为半地堑结构。新竹凹陷和台中凹陷下拗,演变为前陆盆地。晋江凹陷和九龙江凹陷因岩石圈上隆,其沉积较薄。这种模式决定了在台湾海峡地区,西部的生油气层为下第三系,而东部的生油气层为下第三系和上第三系。 相似文献
10.
We analyse tectonic and sedimentary field and subsurface data for the Angola onshore margin together with free-air gravity anomaly data for the offshore margin. This enables us to characterize the mode of syn-rift tectonism inherited from the Precambrian and its impact on the segmentation of the Angola margin. We illustrate that segmentation by the progressive transition from the Benguela transform-rifted margin segment to the oblique-rifted South Kwanza and orthogonal-rifted North Kwanza margin segments. The spatial variation in the intensity of post-rift uplift is demonstrated by the study of a set of geomorphic markers detected in the post-rift succession of the coastal Benguela and Kwanza Basins: Upper Cretaceous to Cenozoic uplifted palaeodeltas, erosional unconformities, palaeovalleys, Quaternary marine terraces and perched Gilbert deltas. The onshore Benguela transform margin has a distinctive, mainly progradational stratigraphic architecture with long-term sedimentary gaps and high-elevation marine terraces resulting from moderate Upper Cretaceous–Cenozoic to major Quaternary uplifting (i.e. 775–1775 mm/ky or m/Ma). By contrast, repeated synchronous episodes of minor Cenozoic to Quaternary uplift occurred along the orthogonal-rifted North Kwanza segment with its Cenozoic aggradational architecture, short-term sedimentary gaps and low-elevation Pleistocene terraces. Margin style likewise governs spatial variations in the volume of offshore sediment dispersed in the associated deep-sea fans. Along the low-lying North Kwanza margin, sedimentation of the broad Cenozoic to Pleistocene Kwanza submarine fan was probably governed by the width of the Kwanza interior palaeodrainage basin combined with the wet tropical Neogene climate. Along the high-rising Benguela margin, the small size of the Benguela deep-sea fan is related to the interplay between moderate continental sediment dispersal from long-lived small catchments and a warm, very arid Neogene climate. However, the driving forces behind the epeirogenic post-rift uplift of the Angola coastal bulge remain a matter of speculation. 相似文献
11.
The morphology of the Gulf of Oman Basin, a 3,400 m deep oceanic basin between Oman and southern Pakistan and southern Iran, ranges from a convergent margin (Makran margin) along the north side, a passive type (Oman margin) along the south side, translation types along the basin's west (Zendan Fault-Oman Line) and east (Murray Ridge) sides and a narrow continental rise and a wide abyssal plain in the centre of the basin. Sediment input into the basin during the Late Quaternary has been mainly from the north as a result of the uplift of the Coast Makran Mountains in the Late Miocene-Pliocene. Today most of this detritrus is deposited on the shelf and upper continental slope and perched basins behind the fold/fault ridges on the lower slope. The presence of fans and channels on the continental rise on the north side of the basin indicate, however, that continental derived debris was, and possibly is, being transported to the deep-sea by turbidity currents via gaps in the ridges on the lower slope. In addition to land derived terrigenous sediments, the basin deposits also contain biogenic (organic matter and calcium carbonate), eolian detritus and hydrates and authigenic carbonates from the tectonic dewatering of the Makran accretionary wedge. The eolian sediment is carried into the Gulf of Oman Basin from Arabia and the Mesopotamia Valley by the northwesterly Shamal winds. This type of detritus was particularly abundant during the glacial arid periods 21,000–20,000 and 11,000 (Younger Dryas) years ago when exposure of the Persian (Arabian) Gulf increased the area of dust entrainment and shifted the position of the source of the eolian sediments closer to the basin. 相似文献
12.
中更新世以来东海陆架的古环境 总被引：12，自引：4，他引：12
基于１９９６年中法合作在东海陆架进行的电火花单道地震调查资料,并与位于东海外陆架钻孔ＤＺＱ４对比,发现对应于氧同位素６期以来的六个地震地层与钻孔地层呈现很好的对应关系,其间共有四次海退－海进的沉积旋回。资料分析表明东海第四纪环境演变与全球气候冷暖变化所导致的海面升降直接相关。 相似文献
13.
14.
The marine geological map n. 502 “Agropoli”, located offshore the Cilento Promontory, southern Italy, is here described and the regional geology interpreted, particularly referring to water depths between the 30 and 200 m isobaths. The geologic map has been constructed in the frame of a research program financed by the National Geological Survey of Italy (CARG Project), finalized to the construction of up-to-date cartography of the Campania region. Geological and geophysical data on the continental shelf and slope offshore of the Southern Campania region have been collected in the study area, bounded northwards by the Salerno Gulf and southwards by the Policastro Gulf. A high resolution multibeam bathymetry allowed for the construction of a marine digital elevation map; sidescan sonar profiles also have been collected and interpreted. The latter, merged to the bathymetry, have represented the base for the marine geologic cartography. The integrated geologic interpretation of seismic, bathymetric and sidescan sonar data has been calibrated by sea-bottom samples. The morpho-structures and the seismic sequences overlying the outcrops of acoustic basement reported in the cartographic representation have been studied in detail using single-channel seismics. The interpretation of seismic profiles has been a support for the reconstruction of the stratigraphic and structural setting of the Quaternary continental shelf successions and the outcrops of rocky acoustic basement in correspondence to the Licosa Cape morpho-structural high. These areas result from the seaward prolongation of the stratigraphic and structural units, widely cropping out in the surrounding emerged sector of the Cilento Promontory. The cartographic approach is based on the recognition of laterally coeval depositional systems, interpreted in the frame of the system tracts of the Late Quaternary depositional sequence. We present evidence of now subaqueous terraces inferred to be palaeoshorelines representing past sea-level positions and tentatively correlated these to oxygen isotopic stratigraphy. 相似文献
15.
Hardbottoms are sequence boundaries and condensed sections that offer clues for the interpretation of the incomplete record of Tertiary continental shelf evolution. Seaward of 5 km, 50% of the inner west-central Florida shelf seafloor is flat hardbottom. These lithified surfaces are punctuated by shorefacing, scarped hardbottoms that trend shore-parallel (330°–0°) and vary in relief (up to 4 m). Scarped hardbottoms are the only natural relief on the inner shelf and support a diverse benthic community, the activities of which erode the outcrops, producing undercuts in excess of 1 m. Outcropping hardbottom strata are comprised of distinct, phosphate-rich, mixed carbonate–siliciclastic lithofacies, that range in age from Miocene to Quaternary. Miocene units are dolomite-rich and mark the upper surface of the inner shelf bedrock (Hawthorn Group). Dolomite within these beds (silt-sized, cloudy centered rhombs) fall into two age groups, correlating with highstands at 15 and 5 Ma. This lithofacies is consistent with models that indicate an increased flux of organic matter – resulting from topographically induced upwelling – promoting dolomitization during early burial diagenesis in the sulfate-reduction zone. Quaternary units are calcite-rich and perched atop the shelf bedrock. Samples of these units record a complex diagenetic history and multiple sea-level fluctuations. Based on evidence of primary marine cementation, they are interpreted to be hardground (non-deposition) surfaces, forming as a function of sediment starvation and minimal sediment movement. Decreased highstand magnitude or duration may have resulted in the absence of a significant organic component to Quaternary hardbottoms, which, in turn, may prevent subsequent dolomitization. These outcrops are a potential source for sediments to the inner shelf, not only as habitat for biological sediment production, but also through their destruction. The undercut, shorefacing, scarped hardbottom morphology displayed by west-central Florida hardbottoms is indicative of bio-erosion. Preliminary studies indicate a potential mass of 0.04 kg m−2 yr−1 of siliciclastic sediment is released to the inner shelf. 相似文献
16.
G.F. Birch 《Marine Geology》1977,23(4):305-337
A combination of climatic and oceanic factors has resulted in slow sedimentation rates on the continental shelf off the west coast of South Africa since Tertiary times. This has enabled a study to be made of the residual Late Tertiary, relict Pleistocene and Holocene sediments.Sediments on the continental shelf form rough belts parallel to the coast. Most of the coarse sediment is confined to the littoral zone and Holocene mud is concentrated at the base of a rocky nearshore platform. A veneer of Quaternary quartzitic sand seawards of the Recent mud belt wedges out onto a Tertiary erosion surface on the mid shelf. Residual glauconite and phosphorite sands derived by erosion during Tertiary sea-level fluctuations cover large parts of the mid shelf in the south. Most of the slope and parts of the outer shelf in the north are draped by Recent foraminiferal and coccolithophorid debris. 相似文献
17.
海平面变化及其海岸响应 总被引：4，自引：0，他引：4
第四纪气温的大幅度冷暖变化，导致全球海平面的变化，引起陆架海侵扣海退。海岸上的各种地貌如海滩、沙坝、三角洲扣陆架沙脊等响应海平面升降而发生新的演化扣变异。东海陆架古岸线、围绕古岸线发育的陆架沙脊、陆架深切河谷扣河谷充填沉积以及冰后期海进型扣海退型沙坝的形成乖演化等沉积事件都是响应海平面升降的结果。近百年来特别是近30年全球海平面普遍上升，引起风暴潮的频度扣幅度的增大。近岸波能增强，越滩浪增多，导致海滩侵蚀，岸线后退。Bruun法则扣其他一些模型能够说明海滩随海平面上升而蚀退的规律，但在预测速率时仍存在很多问题。使用时应注意海平面变化的区域性、海滩发育的滞后性和海滩蚀退因素间的权重关系。 相似文献
18.
Abstract The very unique continental margin of North Victoria Land, Antarctica, is characterized by complex bathymetry, reflecting control by glacial, tectonic, and marine processes. The abnormally shallow shelf can be divided into a deep, rugged, glacially dominated inner shelf and a smoother, shallower outer shelf, which is dominated by marine and glacial marine processes. Deep u‐shaped glacial troughs incise the shelf, while relict v‐shaped canyons incise the upper slope. Trending northwest‐southeast along the eastern edge of the area lies a rugged chain of seamounts representing the southern extension of the Balleny Fracture Zone. The continental slope is dominated by strong contour currents and gravity processes. 相似文献
19.
大陆岛入海沉积物通量（Qs）信息对于精确解译大陆架沉积记录的研究是个重要补充。针对如何估算大陆岛Qs的科学问题,本文以中国东南部海域的8 227个大陆岛为例,提出了一种基于邻近大陆中小型河流Qs的经验公式计算大陆岛Qs的解决方案。该方案在实施时需设置两个假定,即大陆岛的Qs法则遵循邻近大陆中小河流的Qs法则和可将1个大陆岛当作1个河流流域计算其Qs。结果表明:（1）经验公式计算的大陆岛Qs为其最小估计值;如考虑大陆岛流域的具体情况,实际的Qs值会稍微增加,但其增幅不超过n0.13（n为流域数量）;（2）经验公式能获取大陆岛Qs的大致数量级信息;大陆岛的总面积为4 418.49 km2,对应Qs的数量级为106 t/a,与邻近大陆中型河流入海通量的数量级相当;（3）在大河河口湾充填阶段完成以前,大陆岛沉积物是内陆架泥质沉积体的主要物源之一。因此,大陆岛入海沉积物会对大陆架沉积体系的形成和演化造成一定程度的影响,需引起研究人员的高度重视。 相似文献
20.
冲绳海槽断裂、岩浆构造活动和洋壳化进程 总被引：3，自引：1，他引：2
讨论了冲绳海槽断裂、岩浆构造活动特征和它们之间的关系,认为雁行排列的地堑斜交于陆架外缘隆起带,海槽北段断块隆脊、龙王构造带和海槽南段"棉花构造带"可能保留了海槽各幕断陷前的火山岩浆活动特征,而现在活动的吐噶喇火山岛弧可沿海槽南段岛坡追踪到台湾。吕宋岛向台湾的碰撞挤压引起的旋张活动加强了海槽南段的地壳拉张,诱发了地堑内火山岩浆活动,在洋壳化进程中起关键作用,其中最典型的八重山地堑已经形成洋壳。断裂和岩浆活动主要是单向地向岛弧侧迁移,由洋中脊扩张产生的对称条带状磁异常模式难以解释冲绳海槽的洋壳化进程。 相似文献