沉积环境对雅浦海沟沉积颗粒物组成和分布的影响     

吴彬  李栋  赵军  刘诚刚  孙承君  陈建芳  潘建明  韩正兵  胡佶 《海洋学报》2018,40(10):167-179

通过对西太平洋雅浦海沟不同水深沉积物中总有机碳（TOC）、总氮（TN）、碳稳定同位素（δ13C）、粒度组成和比表面积（SSA）等参数的分析，探讨了雅浦海沟不同水深沉积颗粒物来源、分布及其影响因素的异同。结果表明，雅浦海沟沉积物TOC含量和δ13C平均值分别为（0.34%±0.14%）和（-20.8‰±0.7‰），其中海洋浮游植物、陆源土壤和维管植物来源有机碳（OC）的贡献分别为（70%±3%）、（22%±3%）和（8%±2%），且不同水深差异不大，海沟内沉积物的横向输运可能是深部沉积OC的重要输入途径。由于水深更深站位沉积颗粒物中具有更强的微生物活动和在水柱中更长的保留时间，导致其TOC和TN含量较低，但δ13C无明显差异。水深较浅站位TN含量、SSA、粒径组成和中值粒径等参数垂向变化波动较更深站位更为显著，表明海沟沟壁水深较浅处物源输入和沉积环境的不稳定。同时，由于低OC含量、低SSA以及高密度的海底火山喷出岩在海沟水深较浅的沟壁坡折处的广泛分布，导致该区域粒径组成与TOC含量无显著相关性，而较深站位中TOC含量与粉砂呈正相关，与砂和黏土含量呈负相关。整体而言，雅浦海沟沉积物中粉砂粒级颗粒物是OC的主要载体，而SSA是影响海沟沉积OC剖面分布的最重要因素。  相似文献   

Modeling touchdown point oscillation and its relationship with fatigue response of steel catenary risers     

《Applied Ocean Research》2019

The riser-seabed interaction resulting in a trench formed in the touchdown zone (TDZ) of steel catenary risers (SCR) has a significant influence on accumulated fatigue damage. Several studies have used different trench modeling approaches to investigate the trench effect on fatigue. However, contradictory observations have been reported with no coherent agreement on the beneficial or detrimental effect of the trench on fatigue. In this study, the significance of trench geometry in fatigue damage evaluation was investigated. Using analytical and numerical approaches, a meaningful relationship was observed between the trench slope in different zones and the peak fatigue damage. A new set of rules was proposed for the qualitative assessment of the overall trend of trench effect on the variation of fatigue damage. The proposed assessment rules were validated by performing comprehensive numerical fatigue analysis. A comparison with samples of published experimental and numerical studies was also completed. It was observed that depending on the direction of the low-frequency vessel excursions, the peak fatigue damage may increase towards the near offsets and decrease towards the far vessel offset. This implied that the case dependency of the trench effect on fatigue response in different geographical locations with various environmental loads was a potential source for the contradictory results reported in previously published studies.  相似文献   

罗山东麓断裂全新世古地震研究   总被引：5，自引：0，他引：5  

闵伟  柴炽章  王萍  杨平 《高原地震》1993,(4)

罗山东麓断裂全新世活动强烈,古地震现象丰富。探槽揭露出晚更新世末或全新世初以来,已发生过5次7级左右的古地震事件,除最早的一次时间不明外,其它4次分别发生在距今约8400年、5400—5020年、3900年和2260年。全新世早期古地震重复间隔在3000年左右,晚期为1500年左右。  相似文献   

Resolving slip vector azimuths and plate motion along the southern boundary of the South Bismarck Plate,Papua New Guinea     

P. Tregoning  H. McQueen 《Australian Journal of Earth Sciences》2013,60(5):745-750

The interaction of the Australian, South Bismarck and Solomon Sea Plates in Papua New Guinea is the source of frequent earthquakes that occur as a result of subduction and arc continent collision. Previous investigators have drawn attention to a discontinuity in the horizontal azimuth of slip vectors along the southern boundary of the South Bismarck Plate, with those to the west of 148°E being systematically rotated 20ndash;30° clockwise compared to those located east of 148°E. This has led to the suggestion that relative motion may be occurring between the Huon Peninsula and New Britain or that more than two plates are acting south of the South Bismarck Plate. Global positioning system (GPS) measurements since 1991 indicate that there is no internal deformation occurring within the South Bismark Plate and that at least two distinct plates are in contact with the southern edge of the South Bismarck Plate. We show from a study of a recent earthquake dataset that the change in slip vector azimuth can be modelled by the interaction of the overriding South Bismarck Plate with the underthrusting Australian and Solomon Sea Plates, consistent with the GPS observations, while maintaining the South Bismarck Plate as a rigid entity. We found that a transition zone exists between 147°E and 148°E where the underlying plate changes from the Australian Plate to the Solomon Sea Plate. There are insufficient data at present to indicate whether or not a third plate, the Woodlark Plate, is also interacting directly with the South Bismarck Plate in this transition zone. Slip vector azimuths were used to estimate an Euler pole (6.74°S, 144.64°E), which describes the relative motion of the South Bismarck and Solomon Sea Plates along the New Britain Trench.  相似文献   

Control of paleoshorelines by trench forebulge uplift,Loyalty Islands     

William R. Dickinson 《Quaternary Research》2013

Unlike most tropical Pacific islands, which lie along island arcs or hotspot chains, the Loyalty Islands between New Caledonia and Vanuatu owe their existence and morphology to the uplift of pre-existing atolls on the flexural forebulge of the New Hebrides Trench. The configuration and topography of each island is a function of distance from the crest of the uplifted forebulge. Both Maré and Lifou are fully emergent paleoatolls upon which ancient barrier reefs form highstanding annular ridges that enclose interior plateaus representing paleolagoon floors, whereas the partially emergent Ouvea paleoatoll rim flanks a drowned remnant lagoon. Emergent paleoshoreline features exposed by island uplift include paleoreef flats constructed as ancient fringing reefs built to past low tide levels and emergent tidal notches incised at past high tide levels. Present paleoshoreline elevations record uplift rates of the islands since last-interglacial and mid-Holocene highstands in global and regional sea levels, respectively, and paleoreef stratigraphy reflects net Quaternary island emergence. The empirical uplift rates vary in harmony with theoretical uplift rates inferred from the different positions of the islands in transit across the trench forebulge at the trench subduction rate. The Loyalty Islands provide a case study of island environments controlled primarily by neotectonics.  相似文献   

Geodynamics of the Amirante Ridge and Trench Complex,Western Indian Ocean     

《International Geology Review》2012,54(1):81-92

The formation and evolution of the ～600 km long arcuate Amirante Ridge and Trench Complex (ARTC) is a significant geomorphic–structural feature in the Western Indian Ocean (WIO). The WIO contains evidence of at least two major magmatic episodes followed by continental rifting within the span of a little more than 20 million years. This involved the splitting of Madagascar from India at around 85 Ma and then separation between India and the Seychelles at 64–63 Ma as a possible consequence of two powerful volcanic eruptions from the Marion and Reunion hot spots, respectively. Formation and evolution of the ARTC represents this tumultuous period in the Indian Ocean, approximately between 85 and 60 Ma (Late Cretaceous–Early Tertiary).

We integrated geophysical, palaeomagnetical, and petrological data to examine three existing models that attempt to explain the formation of ARTC. In contrast, our study hints at several stages of extension and compression responsible for its formation. Our integrated data also suggest that the Carlsberg Ridge may have played a prominent role in the evolution of the ARTC that seems to have formed through a ridge-jump process after the conjugate spreading centres – Mascarene and Palitana ridges formed earlier during the India–Madagascar separation – ceased spreading because of violent eruption of the Reunion hot spot at around 65 Ma. The eruption disturbed the plumbing system of magma ascent, resulting in cessation of spreading along the conjugate spreading centres, forcing a ridge jump.

A collage of seismic refraction and reflection, free-air gravity, magnetic anomaly data, and Ar dating of rocks indicates that as the Carlsberg Ridge swept the Seychelles towards south, the crust between Madagascar and the Seychelles was increasingly compressed, with the abandoned northern Mascarene spreading centre absorbing the maximum stress. With continued compression, the western limb of the abandoned spreading ridge was thrust below the eastern limb to a limited degree. This partial subduction agrees with the gravity and seismic results. Our new study also accounts for the anomalous presence of 14 km-thick oceanic crust beneath the ARTC and its characteristic difference in petrology with other established subduction zones in the world.  相似文献   

雅浦海沟深海沉积物可培养真菌多样性及其反硝化能力研究          下载免费PDF全文

何高阳  徐炜  郭双双  刘文华  骆祝华 《应用海洋学学报》2018,37(2):229-240

自雅浦海沟4个站位的12个沉积物样品中分离得到38株真菌菌株,基于形态观察和ITS序列信息对所得菌株进行分类鉴定,发现它们分别属于青霉属(Penicillium,17株)、曲霉属(Aspergillus,7株)、篮状菌属(Talaromyces,1株)、枝孢属(Cladosporium,6株)、赭霉属(Ochroconis,1株)、Meyerozyma属(1株)、梅拉菌属(Meira,1株)、Cystobasidium属(2株)、Wallemia属(1株)和红酵母属(Rhodotorula,1株)等10个属.其中青霉属、曲霉属和枝孢属菌株为优势菌株,分别占分离菌株总数的44.7%、18.4%和15.8%;而Wallemia属(节担菌纲)菌株是首次从深海环境中分离到.利用PCR技术在分离的深海真菌菌株中检测nir K和P450nor两种反硝化关键酶基因,结果显示nir K基因可在黄曲霉(Aspergillus flavus)、黑曲霉(Aspergillus niger)、杂色曲霉(Aspergillus versicolor)、枝孢菌(Cladosporium sp.)、枝状枝孢(Cladosporium cladosporioides)和产黄青霉(Penicillium chrysogenum)等6种真菌菌株中检测到,而P450nor基因仅在黄曲霉菌株中检测到.同时还通过富集培养方法从上述沉积物样品中分离获得两株反硝化枝孢菌.结果表明,雅浦海沟深海沉积物环境中存在着丰富的真菌资源,它们在深海环境氮循环中起着一定作用,这将增强人们对深海环境可培养真菌多样性及其生态作用的认识.  相似文献   

马里亚纳海沟“挑战者深渊”最深点水深探测   总被引：1，自引：0，他引：1  

刘方兰  杨胜雄  邓希光  曲佳 《海洋测绘》2013,33(5):49-52

2011²012年,海洋六号船采用EM122多波束测深系统在马里亚纳海沟最深海域"挑战者深渊"进行的多波束水深测量,通过对测深资料进行分析处理,获得了高精度海底地形图,揭示了马里亚纳海沟挑战者深渊附近海底地形呈近东西向延伸,有西部、中部和东部三个洼地,它们由10800m等深线圈闭,长轴方向与海沟方向一致。洼地底部水深大于10900m,地形较为平坦。三个洼地最深区域分别由10916m、10904m和10915m等深线圈闭。三个洼地最大水深为10917m(误差小于20m),位于西部洼地内,中心位置为142°12.14'E,11°19.92'N。该处也是马里亚纳海沟最深点。  相似文献   

Speculations on the petroleum geology of the accretionary body: an example from the central Aleutians     

Jill McCarthy  Andrew J. Stevenson  David W. Scholl  Tracy L. Vallier 《Marine and Petroleum Geology》1984,1(2):151-167

In the 300 km wide Adak-Amlia sector of the central Aleutian Trench ≈ 36 000 km³ of offscraped trench fill makes up the wedge-shaped mass of the Aleutian accretionary body. Within this wedge, seismic reflection profiles reveal an abundance of potential hydrocarbon-trapping structures. These structures include antiforms, thrust and normal faults, and stratigraphic pinchouts. Maximum closure on these features is 2 km. In addition, the silt and possibly sand size sediment within the offscraped turbidite deposits, and the porous diatomaceous pelagic deposits interbedded with and at the base of the wedge, may define suitable reservoirs for the entrapment of hydrocarbons. Potential seals for these reservoirs include diagenetically-altered and -produced siliceous and carbonate sediment. The organic carbon input into the central Aleutian Trench, based on carbon analyses of DSDP Legs 18 and 19 core samples, suggests that the average organic carbon content within the accretionary body is approximately 0.3–0.6%. Heat flow across the Aleutian Terrace indicates that at present the oil generation window lies at a depth of 3–6.5 km. At depths of 8 km (which corresponds to the maximum depth the offscraped sediment has been seismically resolved beneath the lower trench slope), the probable high (170–180°C) temperatures prohibit all but gas generation. The dewatering of trench sediment and subducted oceanic crust should produce an abundance of fluids circulating within the accretionary body. These fluids and gases can conduct hydrocarbons to any of the abundant trapping geometries or be lost from the system through sea floor seepage. In the Aleutian accretionary body all the conditions necessary for the formation of oil and gas deposits exist. The size and ultimate preservation of these deposits, however, are dependent on the deformational history of the prism both during accretion and after the accretion process has been superceded by subsequent tectonic regimes.  相似文献   

Geometry and structure of the Vitiaz Trench Lineament (SW Pacific)     

Bernard Pelletier  Jean-Marie Auzende 《Marine Geophysical Researches》1996,18(2-4):305-335

Swath bathymetric, sonar imagery and seismic reflection data collected during the SOPACMAPS cruise Leg 3 over segments of the Vitiaz Trench Lineament and adjacent areas provide new insights on the geometry and the stuctural evolution of this seismically inactive lineament. The Vitiaz Trench Lineament, although largely unknown, is one of the most important tectonic feature in the SW Pacific because it separates the Cretaceous crust of the Pacific Plate to the north from the Cenozoic lithosphere of the North Fiji and Lau Basins to the south. The lineament is considered to be the convergent plate boundary between the Pacific and Australian Plates during midde to late Tertiary time when the Vitiaz Arc was a continuous east-facing are from the Tonga to the Solomon Islands before the development of the North Fiji and Lau Basins. Progressive reversal and cessation of subduction from west to east in the Late Miocene-Lower Plioene have been also proposed. However, precise structures and age of initiation and cessation of deformation along the Vitiaz Trench Lineament are unknown.The lineament consists of the Vitiaz Trench and three discontinuous and elongated troughs (Alexa, Rotuma and Horne Troughs) which connect the Vitiaz Trench to the northern end of the Tonga Trench. Our survey of the Alexa and Rotuma Troughs reveals that the lineament is composed of a series of WNW-ESE and ENE-WSW trending segments in front of large volcanic massifs belonging to the Melanesian Border Plateau, a WNW trending volcanic belt of seamounts and ridges on Pacific crust. The Plateau and Pacific plate lying immediately north of the lineament have been affected by intense normal faulting, collapse, and volcanism as evidenced by a series of tilted blocks, grabens, horsts and ridges trending N 120° to N100° and N60°–70°. This tectonism includes several normal faulting episodes, the latest being very recent and possibly still active. The trend of the fault scarps and volcanic ridges parallels the different segments of the Vitiaz Trench Lineament, suggesting that tectonics and volcanism are related to crustal motion along the lineament.Although the superficial observed features are mainly extensional, they are interpreted as the result of shortening along the Vitiaz Trench Lineament. The fabric north of the lineament would result from subduction-induced normal faulting on the outer wall of the trench and the zig-zag geometry of the Vitiaz Trench Lineament might be due to collision of large volcanic edifices of the Melanesian Border Plateau with the trench, provoking trench segmentation along left-lateral ENE-WSW trending transform zones. The newly acquired bathymetric and seismic data suggest that crustal motion (tectonism associated with volcanism) continued up to recent times along the Vitiaz Trench Lineament and was active during the development of the North Fiji Basin.  相似文献