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1.
The Cenozoic Yinggehai-Song Hong and Qiongdongnan Basins together form one of the largest Cenozoic sedimentary basins in SE Asia. Detail studying on the newly released regional seismic data, we observed their basin structure and stratigraphy are clearly different. The structure of the NW–SE elongation of the Yinggehai-Song Hong Basin is strongly controlled by the strike–slip faulting of steep Red River Fault. And the basement is covered by heavy sediments from the Red River. However, structures closely related with rifting are imagined on the seismic data from the Qiongdongnan Basin. This rifting and thinning on the northern continental margin of the South China Sea is necessary to be explained by the subduction of a Proto-South China Sea oceanic crust toward the NW Borneo block during the Eocene–Early Miocene. To test how the strike–slip faulting in the Yinggehai-Song Hong Basin and rifting in the Qiongdongnan Basin develop together in the northwest corner of the South China Sea, we reconstructed the tectonics of the northwest corner of the South China Sea and test the model with software of MSC MARC. The numerical model results indicate the South China Sea and its surrounding area can be divided into a collision-extrusion tectonic province and a Proto-South China Sea slab pull tectonic province as suggested in previous works. We suggested that offshore Red River Fault in the Yinggehai-Song Hong Basin is confirmed as a very important tectonic boundary between these two tectonic provinces.  相似文献   

2.
Rifting of the Qiongdongnan Basin was initiated in the Cenozoic above a pre-Cenozoic basement, which was overprinted by extensional tectonics and soon after the basin became part of the rifted passive continental margin of the South China Sea. We have integrated available grids of sedimentary horizons, wells, seismic reflection data, and the observed gravity field into the first crust-scale structural model of the Qiongdongnan Basin. Many characteristics of this model reflect the tectonostratigraphic history of the basin. The structure and isopach maps of the basin allow us to reconstruct the history of the basin comprising: (a) The sediments of central depression are about 10 km thicker than on the northern and southern sides; (b) The sediments in the western part of the basin are about 6 km thicker than that in the eastern part; (c) a dominant structural trend of gradually shifting depocentres from the Paleogene sequence (45–23.3 Ma) to the Neogene to Quaternary sequence (23.3 Ma–present) towards the west or southwest. The present-day configuration of the basin reveals that the Cenozoic sediments are thinner towards the east. By integrating several reflection seismic profiles, interval velocity and performing gravity modeling, we model the sub-sedimentary basement of the Qiongdongnan Basin. There are about 2–4 km thick high-velocity bodies horizontal extended for a about 40–70 km in the lower crust (v > 7.0 km/s) and most probably these are underplated to the lower stretched continental crust during the final rifting and early spreading phase. The crystalline continental crust spans from the weakly stretched domains (about 25 km thick) near the continental shelf to the extremely thinned domains (<2.8 km) in the central depression, representing the continental margin rifting process in the Qiongdongnan Basin. Our crust-scale structural model shows that the thinnest crystalline crust (<3 km) is found in the Changchang Sag located in the east of the basin, and the relatively thinner crystalline crust (<3.5 km) is in the Ledong Lingshui Sag in the west of the basin. The distribution of crustal extension factor β show that β in central depression is higher (>7.0), while that on northern and southern sides is lower (<3.0). This model can illuminate future numerical simulations, including the reconstruction of the evolutionary processes from the rifted basin to the passive margin and the evolution of the thermal field of the basin.  相似文献   

3.
The present-day basement depth of the seafloor in the absence of sediment loading was inferred along a traverse crossing the Southern Tyrrhenian Basin. A correction for sediment loading was proposed on the basis of density, seismic velocity and porosity data from selected deep boreholes. The empirical relation between sediment correction and seismic two-way travel time was extrapolated downward by applying the Nafe–Drake curve and a specific porosity–depth relation. The sediment loading response of the basement calculated for flexural isostasy is on average about one hundred meters lower than results for local isostasy. A pure lithosphere extensional model was then used to predict quantitatively the basement subsidence pattern on the margins of the basin. The basement depth is consistent with uniform extension model predictions only in some parts of the margins. The observed variability in the region of greatest thinning (transition from continental to oceanic crust) is attributable to the weakening effect caused by diffuse igneous intrusions. Subsidence of the volcanic Calabrian–Sicilian margin is partly accounted for by magmatic underplating. The comparison of the calculated subsidence with an oceanic lithosphere cooling model shows that subsidence is variable in some areas, particularly in the Marsili Basin. This argues for a typical back-arc origin for the Tyrrhenian Basin, as a result of subduction processes. By taking into account the geodynamic setting, stratigraphic data from the deepest hole and the terrestrial heat flow, we reconstructed the paleotemperatures of cover sediments. The results suggest that low temperatures generally have prevailed during sediment deposition and that the degree of maturation is expected not to be sufficient for oil generation processes.  相似文献   

4.
Based on bathymetric data and multichannel seismic data, the Manila subduction system is divided into three segments, the North Luzon segment, the seamount chain segment and the West Luzon segment starts in Southwest Taiwan and runs as far as Mindoro. The volume variations of the accretionary prism, the forearc slope angle, taper angle variations support the segmentation of the Manila subduction system. The accretionary prism is composed of the outer wedge and the inner wedge separated by the slope break. The backstop structure and a 0.5–1 km thick subduction channel are interpreted in the seismic Line 973 located in the northeastern South China Sea. The clear décollement horizon reveals the oceanic sediment has been subducted beneath the accretionary prism. A number of splay faults occur in the active outer wedge. Taper angles vary from 8.0° ± 1° in the North Luzon segment, 9.9° ± 1° in the seamount segment to 11° ± 1° in the West Luzon segment. Based on variations between the taper angle and orthogonal convergence rates in the world continental margins and comparison between our results and the global compilation, different segments of the Manila subduction system fit well the global pattern. It suggests that subduction accretion dominates the north Luzon and seamount chain segment, but the steep slope indicates in the West Luzon segment and implies that tectonic erosion could dominate the West Luzon segment.  相似文献   

5.
南黄海盆地是在前震旦系克拉通基础上发育的中、古生界海相与中、新生界陆相多旋回叠合盆地。通过地震资料解释,结合邻区钻井与区域地质资料,对南黄海盆地中部隆起中、古生代地层及其形成演化进行了研究,结果表明,南黄海盆地中部隆起沉积了较全的中、古生界海相地层,发育第四系—新近系、中—下三叠统青龙组、上二叠统、下二叠统—上泥盆统、中—下志留统,奥陶系—震旦系和前震旦系变质岩系等7套地震地质层序;主要经历了前震旦纪基底形成、震旦纪—早古生代克拉通发育、晚古生代—中三叠世稳定台地—陆内裂陷、晚三叠世—古近纪形成与抬升剥蚀及新近纪-第四纪坳陷沉降5个阶段。  相似文献   

6.
The outer rise on the distal periphery of a subduction system is caused by emplacement of an accreted load onto the flexed oceanic lithosphere. By examining the bathymetry and free-air gravity anomaly data collected by satellite observations and marine reflection seismic data collected during the TAIGER project, we demonstrate the characteristics of the flexural outer rise seaward of the Manila Trench. The region of the outer rise on the westernmost periphery of the Manila subduction system is characterized by the positive free-air gravity anomaly seaward parallel to the Manila Trench and the morphological rise at the south of the Manila subduction system. A flexure simulation is performed based on the flexural profiles along the southern Manila Trench-outer system and the resulting effective elastic thickness values may provide an alternative aspect for the spreading rates of the South China Sea basin. Since both the western periphery of the Taiwan collision belt and Manila subduction belt are dominated by the strain regime of extension of flexural origin, it appears that the strain regime of flexural extension associated with the flexural forebulge of the Western Taiwan Foreland Basin to the north, and the strain regime of flexural extension associated with the outer rise seaward of the Manila Trench to the south are meridionally interconnected. This revised understanding of the strain regime of flexural extension origin west of the Taiwan–Luzon convergent belt provides an alternative point of view on the strain regime offshore SW Taiwan.  相似文献   

7.
试论东海陆架盆地的基底构造演化和盆地形成机制   总被引：4，自引：0，他引：4  
本文主要根据东海陆架盆地和周边的地质、地球物理资料,分析盆地的基底岩性特征、结构特征。认为东海陆架盆地的基底除元古界片麻岩外,还分布有一定范围的中生界及古生界。基底构造特征是纵向上多层次,横向上不均一,南北有别,东西分带。构造演化上经历了张、合、压、扭等复杂过程。  相似文献   

8.
The South Caspian Basin (SCB) is a relic of the back-arc basin in the margin of the Tethys paleoocean. The SCB has an oceanic-type crust and is filled with a thick (15–28 km) sedimentary series. In the modern structure, it is a part of the South Caspian microplate, which also comprises the Lower Kura and West Turkmenian depressions, parts of the Kopet Dagh and Alborz ranges. The geological and seismological data evidence an underthrust (or, probably, subduction) of the South Caspian Basin’s lithosphere beneath the Apsheron threshold and the simultaneous westward displacement of the South Caspian Microplate (SCM). Different authors refer the South Caspian Basin’s formation to the Early Mesozoic, Late Jurassic, and Paleocene. In this paper, on the basis of geologic information, a two-phase model of the South Caspian Basin’s opening is considered. The first phase is referred to the Late Triassic-Early Jurassic, when the sinking of the Kopet Dagh Basin and the opening of the Great Caucasus rift began as well. Jointly, these three structures formed a prolonged basin related to the development of the Early Mesozoic subduction zone. The age of the oceanic crust in the central part of the South Caspian Basin calculated by the thermal flux is 200 Ma. The second phase of the South Caspian Basin opening referred to the Eocene is related to the extension in the back-arc part of the Elbrus volcanic arc. The formation of the oceanic crust in the southwestern part of the South Caspian Basin and in the Lower-Kura depression is associated with this phase, which is proved by the high values of the thermal flux.  相似文献   

9.
The Pelotas Basin is the classical example of a volcanic passive margin displaying large wedges of seaward-dipping reflectors (SDR). The SDR fill entirely its rifts throughout the basin, characterizing the abundant syn-rift magmatism (133–113 Ma). The Paraná–Etendeka Large Igneous Province (LIP), adjacent to west, constituted the pre-rift magmatism (134–132 Ma). The interpretation of ultra-deep seismic lines showed a very different geology from the adjacent Santos, Campos and Espírito Santo Basins, which constitute examples of magma-poor passive margins. Besides displaying rifts totally filled by volcanic rocks, diverse continental crustal domains were defined in the Pelotas Basin, such as an outer domain, probably constituted by highly stretched and permeated continental igneous crust, and a highly reflective lower crust probably reflecting underplating.The analysis of rifting in this portion of the South Atlantic is based on seismic interpretation and on the distribution of regional linear magnetic anomalies. The lateral accretion of SDR to the east towards the future site of the breakup and the temporal relationship between their rift and sag geometries allows the reconstitution of the evolution of rifting in the basin. Breakup propagated from south to north in three stages (130–127.5; 127.5–125; 125–113 Ma) physically separated by oceanic fracture zones (FZ). The width of the stretched, thinned and heavily intruded continental crust also showed a three-stage increase in the same direction and at the same FZ. Consequently, the Continental-Oceanic Boundary (COB) shows three marked shifts, from west to east, from south to north, resulting into rift to margin segmentation. Rifting also propagated from west to east, in the direction of the final breakup, in each of the three segments defined. The importance of the Paraná–Etendeka LIP upon the overall history of rupturing and breakup of Western Gondwanaland seems to have been restricted in time and in space only to the Pelotas Basin.  相似文献   

10.
我国南海历史性水域线的地质特征   总被引：3，自引：1，他引：2  
40a的海洋地质、地球物理实测研究表明,九段线不仅是显示我国南海主权的历史性水域线,而且总体上也是南海与东部、南部和西部陆区及岛区的巨型地质边界线。根据实测数据,本文将从地质成因、来源、演化的角度论述此南海历史性水域线的合理性。主要结论包括:历史性水域线的东段在地形上基本与马尼拉海沟一致,海沟西侧为南海中央海盆洋壳区,东侧为菲律宾群岛。根据国际地质研究的资料,菲律宾群岛始新世以前位于较偏南的纬度,后来于中晚中新世(距今16~10Ma)仰冲于南海中央海盆之上,因此菲律宾群岛是一个外来群岛。而黄岩岛在马尼拉海沟以西,是中央海盆洋壳区的一个岛礁,与菲律宾群岛成因不同。南海历史性水域线的南段在地形上基本与南沙海槽一致,伴随南沙地块由北部陆缘向南裂离,古南海洋壳沿此海槽以南俯冲至加里曼丹岛陆壳之下,因此南沙地块与加里曼丹陆块为两个来历不同的地块。南海历史性水域线西段的分布在地形上与越东巨型走滑断裂带基本一致,可能与西沙地块、中沙地块、南沙地块从南海北部陆缘向南滑移有关。南沙地块北缘陡直的正断层结构,突显中央海盆是拉裂形成,其基底和中新生代地层与北部珠江口盆地的地层结构可以对比,说明南沙岛礁原属我国华南大陆南缘,后因南海的形成裂离至现今的位置。  相似文献   

11.
东海陆架盆地是位于中国东部华南大陆边缘的一个中、新生代叠合盆地,具有较大油气潜力。目前东海陆架盆地油气的发现均来自于新生界,对中生代残留地层的各方面特征认识不足:在空间上通常集中于特定构造单元,且基本位于盆地西部;在时间上主要涉及白垩纪和侏罗纪,且多是定性或半定量的研究。本文在前人研究的基础上,收集、整理了研究区目前最新、最全的反射地震资料和钻井数据,从钻遇中生界井的标定出发,以地震资料的层序划分和解释为基础,进行残留地层的研究,空间上统一盆地东、西两大坳陷带,时间上统揽白垩纪、侏罗纪以及前侏罗纪三个时期。结果表明,东海陆架盆地中生代残留地层遭受了后期严重的剥蚀改造,总体呈现东厚西薄、南厚北薄的特征,残留地层范围随时间不断东扩。对比各时期残留地层平面展布特征,揭示了东海陆架盆地的演变过程:三叠纪时期盆地原型为被动大陆边缘坳陷型盆地,早、中侏罗世时期为活动大陆边缘弧前盆地,晚侏罗世—晚白垩世时期为大陆边缘弧后伸展盆地;与此相对应,古太平洋板块俯冲肇始于晚三叠世—早、中侏罗世时期,板块后撤始于晚侏罗世。东海陆架盆地在中生代的东侧边界位于钓鱼岛隆褶带的东侧。  相似文献   

12.
南极布兰斯菲尔德海峡及邻区地壳结构反演及构造解析   总被引：1，自引：0，他引：1  
马龙  邢健 《海洋与湖沼》2020,51(2):265-273
南极布兰斯菲尔德海峡及邻区是南极半岛海域火山、地震等新构造运动最活跃的地区,由于前人对资料处理解释的差异,导致盆地的构造格局仍部分存疑。本文以研究区的卫星重力数据为基础,以多道反射地震和部分岩性资料为约束,采用重震联合反演方法构建了三条横跨研究区的地壳结构剖面,并进一步研究布兰斯菲尔德海峡盆地的地壳结构。研究结果表明布兰斯菲尔德海峡盆地莫霍面深度为33—38km。菲尼克斯板块俯冲消减下沉至南设得兰岛弧之下,导致南设得兰海沟的俯冲带后撤,产生3—4km厚的岩浆混染地壳,密度为2.9g/cm~3。分析认为受板块运动和弧后扩张影响,沿布兰斯菲尔德海峡盆地扩张脊分布的海底火山裂隙式喷发,并进一步导致盆地的持续性扩张。  相似文献   

13.
Most of the basins developed in the continental core of SE Asia (Sundaland) evolved since the Late Cretaceous in a manner that may be correlated to the conditions of the subduction in the Sunda Trench. By the end of Mesozoic times Sundaland was an elevated area composed of granite and metamorphic basement on the rims; which suffered collapse and incipient extension, whereas the central part was stable. This promontory was surrounded by a large subduction zone, except in the north and was a free boundary in the Early Cenozoic. Starting from the Palaeogene and following fractures initiated during the India Eurasia collision, rifting began along large faults (mostly N–S and NNW–SSE strike-slip), which crosscut the whole region. The basins remained in a continental fluvio-lacustrine or shallow marine environment for a long time and some are marked by extremely stretched crust (Phu Khanh, Natuna, N. Makassar) or even reached the ocean floor spreading stage (Celebes, Flores). Western Sundaland was a combination of basin opening and strike-slip transpressional deformation. The configuration suggests a free boundary particularly to the east (trench pull associated with the Proto-South China Sea subduction; Java–Sulawesi trench subduction rollback). In the Early Miocene, Australian blocks reached the Sunda subduction zone and imposed local shortening in the south and southeast, whereas the western part was free from compression after the Indian continent had moved away to the north. This suggests an important coupling of the Sunda Plate with the Indo-Australian Plate both to SE and NW, possibly further west rollback had ceased in the Java–Sumatra subduction zone, and compressional stress was being transferred northwards across the plate boundary. The internal compression is expressed to the south by shortening which is transmitted as far as the Malay basin. In the Late Miocene, most of the Sunda Plate was under compression, except the tectonically isolated Andaman Sea and the Damar basins. In the Pliocene, collision north of Australia propagated toward the north and west causing subduction reversal and compression in the short-lived Damar Basin. Docking of the Philippine Plate confined the eastern side of Sundaland and created local compression and uplift such as in NW Borneo, Palawan and Taiwan. Transpressional deformation created extensive folding, strike-slip faulting and uplift of the Central Basin and Arakan Yoma in Myanmar. Minor inversion affected many Thailand rift basins. All the other basins record subsidence. The uplift is responsible for gravity tectonics where thick sediments were accumulated (Sarawak, NE Luconia, Bangladesh wedge).  相似文献   

14.
台湾增生楔的构造单元划分及其变形特征   总被引：6，自引：0，他引：6  
台湾增生楔位于欧亚板块、菲律宾海微板块和南海的结合部位,是现代弧陆碰撞研究的理想场所。通过对南海973航次在该区域的多道地震剖面的解释,对该增生楔进行了构造单元的划分,并分析了变形特征。认为台湾增生楔是由3个部分,即弧陆碰撞产生的增生部分、洋内俯冲产生的增生部分和增生楔后端在恒春海脊和北吕宋海槽之间的构造楔组成,研究区的高屏斜坡、恒春海脊和北吕宋海槽西端变形带分别是3个部分的反映。自中中新世以来,南海洋壳开始沿着马尼拉海沟向菲律宾海微板块俯冲,形成增生楔中洋内俯冲增生部分;与此同时菲律宾海微板块开始向NW方向移动,前缘的吕宋岛弧自6．5Ma B．P以来与亚洲陆缘斜向碰撞,形成增生楔中弧陆碰撞增生部分。碰撞首先发生在台湾岛的北部,由于弧陆强烈的挤压作用,增生楔后端部分向北吕宋海槽倒冲楔人,使得上部的北吕宋海槽的沉积发生隆升变形。滨海的各个地貌单元可以和台湾陆上的地貌单元相联系,它们具有相似的地质特征,但是由于陆上部分增生历史久,不仅抬升为陆,而且地层的年代也更老。  相似文献   

15.
We show the magnetic model of the Selli-Vavilov region. The Selli Line is known as the northwestern edge of the southern Tyrrhenian Basin. The tectonic evolution of the Tyrrhenian Basin is dominated by a Tortonian-Quaternary extension through the eastward movement of the Apennine subduction system. This migration has generated a diffuse stretching of the continental crust with the emplacement of new oceanic material. This latter occurred in several localized zones where the eastward retreating of the Ionian subduction system produced a strong depletion of the crust with formation of basins and correlated spreading. Nowadays the presence of oceanic crust is confirmed through direct drilling investigation but a complete mapping of the oceanic crustal distribution is still lacking. The Selli-Vavilov region shows a differentiated crustal setting where seamount structures, the oceanic basement portions and continental crust blocks are superimposed. To this aim, a 2D inversion of the magnetic data of this region was conducted to define buried structures. The magnetic susceptibility pattern was computed by solving the least squares problem of the misfit between the predicted and real data for separated wavebands. This method produced two 2D models of the high and low frequency fields of the Selli-Vavilov region. The two apparent susceptibility maps provide different information for distinct ranges of depth. The results of the inversions were also combined with seismic data of the Selli region highlighting the position of the highly magnetized buried bodies. The results confirm a role for the Selli Line as a deep crustal boundary dividing the Sardinian passive domain from the easternmost active region where different oceanic structures are located. The Selli Line has worked as a detachment fault system which has moved eastward. Finally, the Selli-Vavilov region may be interpreted as a tectonic result due to a passive asymmetrical rift occurred between the Tortonian and Pliocene.  相似文献   

16.
南黄海盆地地质演化及构造样式地震解释   总被引：6，自引：0，他引：6  
南黄海盆地奠基于前南华纪变质基底之上,盆地演化历经南华纪—早、中三叠世海相地层发育期、晚白垩世—古近纪箕状断陷发育期和新近纪—第四纪坳陷发育期,为一典型地台—断陷-坳陷多层结构的复合盆地。受不同时期地质营力及区域应力场变化的影响,南黄海盆地形成多种构造样式,可分为伸展构造、挤压构造、反转构造和底辟构造4类,前3类构造样式是地壳水平运动的结果,后一类是地壳垂直运动的结果。  相似文献   

17.
In 2001 and 2002, Australia acquired an integrated geophysical data set over the deep-water continental margin of East Antarctica from west of Enderby Land to offshore from Prydz Bay. The data include approximately 7700 km of high-quality, deep-seismic data with coincident gravity, magnetic and bathymetry data, and 37 non-reversed refraction stations using expendable sonobuoys. Integration of these data with similar quality data recorded by Japan in 1999 allows a new regional interpretation of this sector of the Antarctic margin. This part of the Antarctic continental margin formed during the breakup of the eastern margin of India and East Antarctica, which culminated with the onset of seafloor spreading in the Valanginian. The geology of the Antarctic margin and the adjacent oceanic crust can be divided into distinct east and west sectors by an interpreted crustal boundary at approximately 58° E. Across this boundary, the continent–ocean boundary (COB), defined as the inboard edge of unequivocal oceanic crust, steps outboard from west to east by about 100 km. Structure in the sector west of 58° E is largely controlled by the mixed rift-transform setting. The edge of the onshore Archaean–Proterozoic Napier Complex is downfaulted oceanwards near the shelf edge by at least 6 km and these rocks are interpreted to underlie a rift basin beneath the continental slope. The thickness of rift and pre-rift rocks cannot be accurately determined with the available data, but they appear to be relatively thin. The margin is overlain by a blanket of post-rift sedimentary rocks that are up to 6 km thick beneath the lower continental slope. The COB in this sector is interpreted from the seismic reflection data and potential field modelling to coincide with the base of a basement depression at 8.0–8.5 s two-way time, approximately 170 km oceanwards of the shelf-edge bounding fault system. Oceanic crust in this sector is highly variable in character, from rugged with a relief of more than 1 km over distances of 10–20 km, to rugose with low-amplitude relief set on a long-wavelength undulating basement. The crustal velocity profile appears unusual, with velocities of 7.6–7.95 km s−1 being recorded at several stations at a depth that gives a thickness of crust of only 4 km. If these velocities are from mantle, then the thin crust may be due to the presence of fracture zones. Alternatively, the velocities may be coming from a lower crust that has been heavily altered by the intrusion of mantle rocks. The sector east of 58° E has formed in a normal rifted margin setting, with complexities in the east from the underlying structure of the N–S trending Palaeozoic Lambert Graben. The Napier Complex is downfaulted to depths of 8–10 km beneath the upper continental slope, and the margin rift basin is more than 300 km wide. As in the western sector, the rift-stage rocks are probably relatively thin. This part of the margin is blanketed by post-rift sediments that are up to about 8 km thick. The interpreted COB in the eastern sector is the most prominent boundary in deep water, and typically coincides with a prominent oceanwards step-up in the basement level of up to 1 km. As in the west, the interpretation of this boundary is supported by potential field modelling. The oceanic crust adjacent to the COB in this sector has a highly distinctive character, commonly with (1) a smooth upper surface underlain by short, seaward-dipping flows; (2) a transparent upper crustal layer; (3) a lower crust dominated by dipping high-amplitude reflections that probably reflect intruded or altered shears; (4) a strong reflection Moho, confirmed by seismic refraction modelling; and (5) prominent landward-dipping upper mantle reflections on several adjacent lines. A similar style of oceanic crust is also found in contemporaneous ocean basins that developed between Greater India and Australia–Antarctica west of Bruce Rise on the Antarctic margin, and along the Cuvier margin of northwest Australia.  相似文献   

18.
Complementary to previous work mainly based on seismic interpretation, our compilation of geophysical data (multibeam bathymetry, gravity, magnetic and seismic) acquired within the framework of the ZoNéCo (ongoing since 1993) and FAUST (1998–2001) programs enables us to improve the knowledge of the New Caledonia Basin, Fairway Basin and Fairway Ridge, located within the Southwest Pacific region. The structural synthesis map obtained from geophysical data interpretation allows definition of the deep structure, nature and formation of the Fairway and New Caledonia Basins. Development of the Fairway Basin took place during the Late Cretaceous (95–65 Ma) by continental stretching. This perched basin forms the western margin of the New Caledonia Basin. A newly identified major SW–NE boundary fault zone separates northern NW–SE trending segments of the two basins from southern N–S trending segments. This crustal-scale fault lineament, that we interpret to be related to Cretaceous-early Cainozoic Tasman Sea spreading, separates the NW–SE thinned-continental and N–S oceanic segments of the New Caledonia Basin. We can thus propose the following pattern for the formation of the study area. The end of continental stretching within the Fairway and West Caledonia Basins ( 65–62 Ma) is interpreted as contemporaneous with the onset of emplacement of oceanic crust within the New Caledonia Basin’s central segment. Spreading occurred during the Paleocene (62–56 Ma), and isolated the Gondwanaland block to the west from the Norfolk block to the east. Finally, our geophysical synthesis enables us to extend the structural Fairway Basin down to the structural Taranaki Basin, with the structural New Caledonia Basin lying east of the Fairway Basin and ending further north than previously thought, within the Reinga Basin northwest of New Zealand.  相似文献   

19.
About 16,000 km of multichannel seismic (MCS), gravity and magnetic data and 28 sonobuoys were acquired in the Riiser-Larsen Sea Basin and across the Gunnerus and Astrid Ridges, to study their crustal structure. The study area has contrasting basement morphologies and crustal thicknesses. The crust ranges in thickness from about 35 km under the Riiser-Larsen Sea shelf, 26–28 km under the Gunnerus Ridge, 12–17 km under the Astrid Ridge, and 9.5–10 km under the deep-water basin. A 50-km-wide block with increased density and magnetization is modeled from potential field data in the upper crust of the inshore zone and is interpreted as associated with emplacement of mafic intrusions into the continental margin of the southern Riiser-Larsen Sea. In addition to previously mapped seafloor spreading magnetic anomalies in the western Riiser-Larsen Sea, a linear succession from M2 to M16 is identified in the eastern Riiser-Larsen Sea. In the southwestern Riiser-Larsen Sea, a symmetric succession from M24B to 24n with the central anomaly M23 is recognized. This succession is obliquely truncated by younger lineation M22–M22n. It is proposed that seafloor spreading stopped at about M23 time and reoriented to the M22 opening direction. The seismic stratigraphy model of the Riiser-Larsen Sea includes five reflecting horizons that bound six seismic units. Ages of seismic units are determined from onlap geometry to magnetically dated oceanic basement and from tracing horizons to other parts of the southern Indian Ocean. The seaward edge of stretched and attenuated continental crust in the southern Riiser-Larsen Sea and the landward edge of unequivocal oceanic crust are mapped based on structural and geophysical characteristics. In the eastern Riiser-Larsen Sea the boundary between oceanic and stretched continental crust is better defined and is interpreted as a strike-slip fault lying along a sheared margin.  相似文献   

20.
A key consideration in tectonic models for SE Asia and opening of the South China Sea is the role that the West Baram and Tinjar Lines of NW Borneo may have played in accommodating the motion of crustal blocks displaced from Asia following India's collision. There are few studies that focus on these “lines”. Using onshore geological studies and offshore seismic data to address the origin and tectonic significance of these, this paper concludes that rather than a major transform boundary between Luconia and the Dangerous Grounds, the West Baram Line marks the boundary between domains of continental crust that underwent differential extension in the Eocene. The Baram Basin is underlain by hyperextended continental crust on the NE side of the Baram Line. The strong contrast in the geological features across the Tinjar and West Baram Lines likely reflects ancient differences in crustal rheology with Luconia being the more rigid block. Although lack of significant strike slip faulting along the West Baram Line poses problems for tectonic models in which a wide proto-South China Sea is subducted beneath NW Borneo, intra-plate deformation, such as partial inversion of the Dangerous Grounds rift, offers a potential mechanism to mass balance blocks displaced from Asia with the reduced strike slip motion along the West Baram Line.  相似文献   

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