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1.
Integrated geological and geophysical analysis of the anomalous magnetic field along with the previously unpublished profiles of Spanish expeditions onboard the R/V Hesperides and international databases of geomagnetic data processed in the context of the global tectonics concepts made it possible to identify paleomagnetic anomalies C11–C15 and compile the first map of the bottom geochronology of the Scan Basin. Unlike in earlier known publications, the paleoaxis of spreading does extend northeast, but approximately at an angle of 345°. According to calculations, spreading began 35.294?35.706 Ma ago during chron C15r, and the spreading paleoaxis was abandoned 29.527?29.970 Ma ago during chron C11n.2n. Thus, the destruction of the American–Antarctic bridge in the region joining the Bruce and Discovery banks with formation of oceanic crust in the Scan Basin started about 36 Ma ago. Regular spreading of the bottom has been continuing for about 6 Ma at a average rate close to 1.8 cm/year. 相似文献
2.
Chan Hong Park Jeong Woo Kim Nobuhiro Isezaki Daniel R. Roman Ralph R. B. von Frese 《Marine Geophysical Researches》2006,27(4):253-266
To facilitate geological analyses of the Ulleung Basin in the East Sea (Japan Sea) between Korea and Japan, shipborne and satellite altimetry-derived gravity data are combined to derive a regionally coherent anomaly field. The 2-min gridded satellite altimetry-based gravity predicted by Sandwell and Smith [Sandwell DT, Smith WHF (1997) J Geophys Res 102(B5):10,039–10,054] are used for making cross-over adjustments that reduce the errors between track segments and at the cross-over points of shipborne gravity profiles. Relative to the regionally more homogeneous satellite gravity anomalies, the longer wavelength components of the shipborne anomalies are significantly improved with minimal distortion of their shorter wavelength components. The resulting free-air gravity anomaly map yields a more coherent integration of short and long wavelength anomalies compared to that obtained from either the shipborne or satellite data sets separately. The derived free-air anomalies range over about 140 mGals or more in amplitude and regionally correspond with bathymetric undulations in the Ulleung Basin. The gravity lows and highs along the basin’s margin indicate the transition from continental to oceanic crust. However, in the northeastern and central Ulleung Basin, the negative regional correlation between the central gravity high and bathymetric low suggests the presence of shallow denser mantle beneath thinned oceanic crust. A series of gravity highs mark seamounts or volcanic terranes from the Korean Plateau to Oki Island. Gravity modeling suggests underplating by mafic igneous rocks of the northwestern margin of the Ulleung Basin and the transition between continental and oceanic crust. The crust of the central Ulleung Basin is about a 14–15 km thick with a 4–5 km thick sediment cover. It may also include a relatively weakly developed buried fossil spreading ridge with approximately 2 km of relief. 相似文献
3.
4.
New Bathymetry and Magnetic Lineations Identifications in the Northernmost South China Sea and their Tectonic Implications 总被引：12，自引：1，他引：12
Shu-Kun Hsu Yi-ching Yeh Wen-Bin Doo Ching-Hui Tsai 《Marine Geophysical Researches》2004,25(1-2):29-44
The seafloor spreading of the South China Sea (SCS) was previously believed to take place between ca. 32 and 15 Ma (magnetic anomaly C11 to C5c). New magnetic data acquired in the northernmost SCS however suggests the existence of E–W trending magnetic polarity reversal patterns. Magnetic modeling demonstrates that the oldest SCS oceanic crust could be Late Eocene (as old as 37 Ma, magnetic anomaly C17), with a half-spreading rate of 44 mm/yr. The new identified continent–ocean boundary (COB) in the northern SCS generally follows the base of the continental slope. The COB is also marked by the presence of a relatively low magnetization zone, corresponding to the thinned portion of the continental crust. We suggest that the northern extension of the SCS oceanic crust is terminated by an inactive NW–SE trending trench-trench transform fault, called the Luzon–Ryukyu Transform Plate Boundary (LRTPB). The LRTPB is suggested to be a left-lateral transform fault connecting the former southeast-dipping Manila Trench in the south and the northwest-dipping Ryukyu Trench in the north. The existence of the LRTPB is demonstrated by the different patterns of the magnetic anomalies as well as the different seafloor morphology and basement relief on both sides of the LRTPB. Particularly, the northwestern portion of the LRTPB is marked by a steep northeast-dipping escarpment, along which the Formosa Canyon has developed. The LRTPB probably became inactive at ca. 20 Ma while the former Manila Trench prolonged northeastwards and connected to the former Ryukyu Trench by another transform fault. This reorganization of the plate boundaries might cause the southwestern portion of the former Ryukyu Trench to become extinct and a piece of the Philippine Sea Plate was therefore trapped amongst the LRTPB, the Manila Trench and the continental margin. 相似文献
5.
Masato Joshima Yoshihisa Okuda Fumitoshi Murakami Kiyoyuki Kishimoto Eiichi Honza 《Geo-Marine Letters》1987,6(4):229-234
Magnetic anomalies measured in the central to western half of the Solomon Sea, when considered with other magnetic data, reveal the existence of linear patterns. Magnetic lineation anomaly models of the Cenozoic, 65 to 0 Ma, suggest that an age between 34 and 28 Ma and a half-rate spreading speed of 5.8 cm/yr for the northern flank of a former spreading center best fits our present magnetic data in the Solomon Sea Basin. Heat flow and bathymetry data support this preferred model. 相似文献
6.
Masato Joshima Yoshihisa Okuda Fumitoshi Murakami Kiyoyuki Kishimoto Eiichi Honza 《Geo-Marine Letters》1986,6(4):229-234
Magnetic anomalies measured in the central to western half of the Solomon Sea, when considered with other magnetic data, reveal the existence of linear patterns. Magnetic lineation anomaly models of the Cenozoic, 65 to 0 Ma, suggest that an age between 34 and 28 Ma and a half-rate spreading speed of 5.8 cm/yr for the northern flank of a former spreading center best fits our present magnetic data in the Solomon Sea Basin. Heat flow and bathymetry data support this preferred model. 相似文献
7.
Lodolo Emanuele Coren Franco Schreider Anatoly A. Ceccone Giulio 《Marine Geophysical Researches》1997,19(5):439-450
The southwestern part of the Scotia Sea, at the corner of the Shackleton Fracture Zone with the South Scotia Ridge has been investigated, combining marine magnetic profiles, multichannel seismic reflection data, and satellite-derived gravity anomaly data. From the integrated analysis of data, we identified the presence of the oldest part of the crust in this sector, which tentative age is older than anomaly C10 (28.7 Ma). The area is surrounded by structural features clearly imaged by seismic data, which correspond to gravity lows in the satellite-derived map, and presents a rhomboid-shaped geometry. Along its southern boundary, structural features related to convergence and possible incipient subduction beneath the continental South Scotia Ridge have been evidenced from the seismic profile. We interpret this area, now located at the edge of the south-western Scotia Sea, as a relict of ocean-like crust formed during an earlier, possibly diffuse and disorganized episode of spreading at the first onset of the Drake Passage opening. The successive episode of organized seafloor spreading responsible for the opening of the Drake Passage that definitively separated southern South America from the Antarctic Peninsula, instigated ridge-push forces that can account for the subduction-related structures found along the western part of the South Scotia Ridge. This seafloor accretion phase occurred from 27 to about 10 Ma, when spreading stopped in the western Scotia Sea Ridge, as resulted from the identification of the marine magnetic anomalies. 相似文献
8.
We present previously unreported depth anomalies in the Arabian Basin, northwest Indian Ocean, to provide constraints on the
evolution of the oceanic lithosphere of that basin. The depth anomaly reported in this study was calculated as the difference
between the observed depth to oceanic basement (corrected for sediment load) and the calculated depth to oceanic basement
of the same age. The results indicate an anomalous depth to basement of oceanic crust in the Arabian Basin in the age bracket
of 63–42 Ma, suggesting that subsidence in this basin does not follow the age–depth relationship of normal oceanic crust.
The depth anomalies in the basin vary from +501 to −905 m. A negative depth anomaly zone, mapped in the eastern part of the
basin near the Laccadive Ridge, indicates that here the basement depth is shallower than predicted. By contrast, a positive
depth anomaly zone, mapped in the western part of the basin, indicates a deeper basement depth than expected. We propose that
the excess subsidence of basement of the western part of the basin is probably caused by a relatively cold mantle, compared
to the nearby eastern part of the basin which is affected by the intense thermal field of the former Reunion hotspot. Here,
the rise in oceanic basement is caused by the vertical upwelling of oceanic crust due to convection, followed by a lateral
across-axis flow facilitated by the Reunion hotspot at the time of spreading in early Tertiary times. This interpretation
is in good agreement with spreading-ridge propagation and ridge-hotspot interaction reported earlier for the basin. 相似文献
9.
南海东北部陆缘构造演化信息丰富,对于理解南海的演化过程至关重要。本文收集了南海东北部的深反射地震和海底广角地震成果剖面,提取地壳和下地壳高速层的厚度结果,并结合水深、重磁异常和岩石圈的流变学等地质地球物理资料,对南海东北部的地壳减薄特征、吕宋-琉球转换板块边界的性质和下地壳高速层的分布及成因进行了分析和讨论。南海东北部的地壳减薄在横向和垂向上都存在不均匀性,以下地壳减薄为主,在台西南盆地存在极端减薄地壳;南海北缘的白云凹陷、西沙海槽和西缘的中建南盆地也存在类似的极端减薄地壳,且都与刚性地块共轭或邻近,推测刚性地块的存在导致地壳初始破裂时下地壳流动和地幔上隆是局部出现地壳极端减薄的主要原因。吕宋-琉球转换板块边界两侧在海底地形、新生代反射和重磁异常等方面均存在差异,与中生代岛弧引起的高磁异常大角度相交,其可能是中生代古特提斯构造域向太平洋构造域转换的边界断裂。下地壳高速层在南海东北部广泛发育,结合其分布特征和波速比Vp/Vs的分布区间,认为其是多期次岩浆底侵形成的铁镁质基性岩。 相似文献
10.
《Marine and Petroleum Geology》1988,5(4):306-323
A detailed aeromagnetic survey carried out across the northeast Newfoundland margin clearly shows the presence of sea floor spreading anomalies 25 to 34. Correlation of these anomalies with synthetic profiles shows an increase in the rate of spreading soon after anomaly 27 time. Three fracture zones can be identified by dislocations in the magnetic anomalies; their positions are confirmed on the depth to basement map of this region. An eastward extension of the southernmost fracture zone at latitude 49 N matches well with the Faraday Fracture Zone across the Mid Atlantic Ridge, and with a basement ridge known as Pastouret Ridge mapped off Goban Spur. By combining the present survey data with the previously collected shipborne measurements, we have also traced the westward continuation of the Charlie-Gibbs Fracture Zone under the Newfoundland shelf.A large amplitude magnetic anomaly lies along the margin and separates two zones with different magnetic characteristics: long wavelength small amplitude anomalies on the landward side, and quasi lineated anomalies on the seaward side. Seismic data compilations show that this large anomaly coincides with the ocean-continent boundary at most places north of Flemish Cap. Modelling of the magnetic anomalies indicate that the large amplitude anomaly is caused by the juxtaposition of highly magnetized oceanic crust against weakly magnetized continental crust; this situation is similar to that observed across the Goban Spur margin, which is a conjugate of the Flemish Cap margin. The presence of highly magnetized oceanic crust landward of anomaly 34 and within the Cretaceous Magnetic Quiet Zone is attested to by the presence of similar large amplitude anomalies south of the Flemish Cap and Goban Spur regions, but these do not mark the ocean-continent transition. 相似文献
11.
G. Leitchenkov J. Guseva V. Gandyukhin G. Grikurov Y. Kristoffersen M. Sand A. Golynsky N. Aleshkova 《Marine Geophysical Researches》2008,29(2):135-158
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
12.
Geophysical investigations of crust-scale structural model of the Qiongdongnan Basin, Northern South China Sea 总被引：2，自引：0，他引：2
Ning Qiu Zhenfeng Wang Hui Xie Zhipeng Sun Zhangwen Wang Zhen Sun Di Zhou 《Marine Geophysical Researches》2013,34(3-4):259-279
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
13.
Compared to the northern South China Sea continental margin, the deep structures and tectonic evolution of the Palawan and Sulu Sea and ambient regions are not well understood so far. However, this part of the southern continental margin and adjacent areas embed critical information on the opening of the South China Sea (SCS). In this paper, we carry out geophysical investigations using regional magnetic, gravity and reflection seismic data. Analytical signal amplitudes (ASA) of magnetic anomalies are calculated to depict the boundaries of different tectonic units. Curie-point depths are estimated from magnetic anomalies using a windowed wavenumber-domain algorithm. Application of the Parker–Oldenburg algorithm to Bouguer gravity anomalies yields a 3D Moho topography. The Palawan Continental Block (PCB) is defined by quiet magnetic anomalies, low ASA, moderate depths to the top and bottom of the magnetic layer, and its northern boundary is further constrained by reflection seismic data and Moho interpretation. The PCB is found to be a favorable area for hydrocarbon exploration. However, the continent–ocean transition zone between the PCB and the SCS is characterized by hyper-extended continental crust intruded with magmatic bodies. The NW Sulu Sea is interpreted as a relict oceanic slice and the geometry and position of extinct trench of the Proto South China Sea (PSCS) is further constrained. With additional age constraints from inverted Moho and Curie-point depths, we confirm that the spreading of the SE Sulu Sea started in the Early Oligocene/Late Eocene due to the subduction of the PSCS, and terminated in the Middle Miocene by the obduction of the NW Sulu Sea onto the PCB. 相似文献
14.
珠江口盆地白云凹陷裂后异常沉降研究及成因分析 总被引：1，自引：0，他引：1
南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉张模型计算的理论裂后沉降值进行对比,发现白云主凹中心的裂后异常沉降量最大超过2.6 km,白云南凹最大异常沉降量接近2 km,高于白云凹陷北部边缘的异常沉降。凹陷东部的裂后沉降作用强于凹陷西部。对沉降曲线的研究发现,白云凹陷在中中新世(16.5～10.5 Ma)期间有一段沉降明显加速的过程,白云南凹尤为明显,可能与南海扩张停止事件有关。白云凹陷发育了巨厚的沉积,并且呈韧性伸展状态,本文认为下地壳流可能是导致白云凹陷裂后异常沉降最主要的因素。 相似文献
15.
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
16.
Large Amplitude Magnetic Anomalies in the Northern Sector of the Powell Basin,NE Antarctic Peninsula
Suri/ntildeach E. Galindo-Zaldivar J. Maldonado A. Livermore R. 《Marine Geophysical Researches》1997,19(1):65-80
Magnetic profiles obtained during the Hesant 92/93 cruise with the R/V Hesperides show large amplitude anomalies (up to 1000 nT) along a 100 km wide band in the northern margin of the Powell Basin. The anomalies, which are also locally identified in the eastern and western margins, are attributed to the continuation of the two branches of the Antarctic Peninsula Pacific Margin Anomaly (PMA). Interactive modelling of two-dimensional bodies in four profiles oriented NNW-SSE allows us to determine the main features of the magnetic source bodies within the continental crust. These are elongated in a N60/degE trend, and their base is located at a depth exceeding 15 km. Equivalent magnetic susceptibilities mostly between 0.07 and 0.1 (SI) are obtained. These values are consistent with the hypothesis that remanent magnetisation of the magnetic source bodies is sub-parallel to the present geomagnetic field (norÍmally magnetised). The general trends of the bathymetry a nd the geometry of the acoustic basement on multichannel seismic profiles are consistent with the upper surface of magnetic bodies. In order to match the observed anomalies it is also necessary to consider a second tabular shaped body with induced magnetisation in almost all the profiles, which could represent layers 2 and 3 of the oceanic crust of the Powell Basin. Three different geometries of connection between the anomalies in the Powell Basin margins and the PMA branches are discussed. The most plausible one is the occurrence of two branches, although they are closer together than in the Bransfield Strait. The northern branch would continue along the fragments of continental crust of the South Scotia Ridge located at the northern boundary of the Powell Basin, whereas the southern branch would be located only in the eastern and western passive margins of the Powell Basin. The apparent splitting of the southern branch of the anomalous body indicates that it was emplaced before Oligo cene times, when the opening of this basin occurred, and that it was subsequently fragmented during the Cenozoic. A possible time of formation of the PMA body would be during the long Cretaceous normal polarity interval, which also coincides with a peak in magmatic activity along the Antarctic Peninsula. 相似文献
17.
Matías Soto Ethel MoralesGerardo Veroslavsky Héctor de Santa AnaNelson Ucha Pablo Rodríguez 《Marine and Petroleum Geology》2011,28(9):1676-1689
The Uruguayan continental margin comprises three sedimentary basins: the Punta del Este, Pelotas and Oriental del Plata basins, the genesis of which is related to the break-up of Gondwana and the opening of the Atlantic Ocean. Herein the continental margin of Uruguay is studied on the basis of 2D multichannel reflection seismic data, as well as gravity and magnetic surveys. As is typical of South Atlantic margins, the Uruguayan continental margin is of the volcanic rifted type. Large wedges of seaward-dipping reflectors (SDRs) are clearly recognizable in seismic sections. SDRs, flat-lying basalt flows, and a high-velocity lower crust (HVLC) form part of the transitional crust. The SDR sequence (subdivided into two wedges) has a maximum width of 85 km and is not continuous parallel to the margin, but is interrupted at the central portion of the Uruguayan margin. The oceanic crust is highly dissected by faults, which affect post-rift sediments. A depocenter over oceanic crust is reported (deepwater Pelotas Basin), and volcanic cones are observed in a few sections. The structure of continental crust-SDRs-flat flows-oceanic crust is reflected in the magnetic anomaly map. The positive free-air gravity anomaly is related to the shelf-break, while the most prominent positive magnetic anomaly is undoubtedly correlated to the landward edge of the SDR sequence. Given the attenuation, interruption and/or sinistral displacement of several features (most notably SDR sequence, magnetic anomalies and depocenters), we recognize a system of NW-SE trending transfer faults, here named Río de la Plata Transfer System (RPTS). Two tectono-structural segments separated by the RPTS can therefore be recognized in the Uruguayan continental margin: Segment I to the south and Segment II to the north. 相似文献
18.
The initial configuration of the Arctida Craton was reconstructed from a complex geological-geophysical analysis of the anomalous magnetic field of the Canadian Basin in the Arctic Ocean. The modern version of the bottom geochronology indicates that the first stage of the formation of the Canadian Basin in the Arctic Ocean was related to extension and rifting in the Arctida Craton in the Kimmeridgian. The transformation of rifting into spreading presumably occurred during chron M22Ar (151 Ma). The second stage was related to the opening of the Canadian Basin within chrons M22Ar-M19 (151–145 Ma). The next stage of the opening of the basin was marked by a 100-km jump of the spreading axis to the east. This stage ended after chron M5 (130 Ma ago). At the fourth (Late Cretaceous) stage, extension spanned the Southern Canadian Basin with the formation of large igneous province. 相似文献
19.
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
20.
Cuimei Zhang Zhenfeng Wang Zhipeng Sun Zhen Sun Jianbao Liu Zhangwen Wang 《Marine Geophysical Researches》2013,34(3-4):309-323
Located at the intersection between a NW-trending slip system and NE-trending rift system in the northern South China Sea, the Qiongdongnan Basin provides key clues for us to understand the proposed extrusion of the Indochina Block along with Red River Fault Zone and extensional margins. In this paper we for the first time systematically reveal the striking structural differences between the western and eastern sector of the Qiongdongnan Basin. Influenced by the NW-trending slip faults, the western Qiongdongnan Basin developed E–W-trending faults, and was subsequently inverted at 30–21 Ma. The eastern sector was dominated by faults with NE orientation before 30 Ma, and thereafter with various orientations from NE, to EW and NW during the period 30–21 Ma; rifting display composite symmetric graben instead of the composite half graben or asymmetric graben in the west. The deep and thermal structures in turn are invoked to account for such deformation differences. The lithosphere of the eastern Qiongdongnan Basin is very hot and thinned because of mantle upwelling and heating, composite symmetric grabens formed and the faults varied with the basal plate boundary. However, the Southern and Northern Uplift area and middle of the central depression is located on normal lithosphere and formed half grabens or simple grabens. The lithosphere in the western sector is transitional from very hot to normal. Eventually, the Paleogene tectonic development of the Qiongdongnan Basin may be summarized into three stages with dominating influences, the retreat of the West Pacific subduction zone (44–36 Ma), slow Indochina block extrusion together with slab-pull of the Proto-South China Sea (36–30 Ma), rapid Indochina block extrusion together with the South China Sea seafloor spreading (30–21 Ma). 相似文献