Bathymetry and Canyons of the western Solomon Sea

The floor of the western Solomon Sea (for new bathymetric map see inside back cover of this issue) is dominated by the arched and ridged basement of the Solomon Sea Basin, the partly-sediment-filled New Britain Trench, and a more completely filled trench, the Trobriand Trough. There is a deep basin where the trenches join (149° Embayment), and a silled basin west of the New Britain Trench (Finsch Deep). Submarine canyons descend from the west and south to the 149° Embayment. Abyssal fans and plains are structurally defined and locally disturbed by young faults. Probable submerged pinnacle reefs stand in water depths as great as 1,200 m.     

Regional setting and structure of the western Solomon Sea

The western Solomon Sea is bounded by the Paleogene collision complex of the Papuan Peninsula to the south, and land masses constructed by Cainozoic volcanism to the north and cast. Oblique collision of two trenches in the western Solomon Sea, and concomitant collision of upper plates, have produced structural complexities that may include the local doubling of crustal thickness, coincident with a strong negative gravity anomaly west of 149°E. Lateral flexing of the subducted plate in the New Britain Trench may have caused flexure of the upper plate; this flexure is expressed in the gravity field, faults, dip-slopes, exposure of basement, and alignment of volcanoes.     

Tertiary foraminiferal rock samples from the western Solomon Sea

Rock fragments dredged from four R/VNatsushima stations contain Tertiary foraminifera. The oldest sample is an upper bathyal biomicrite of Early Eocene age (52 to 53.5 Ma) from the the Trobriand Platform. Upper Oligocene-Lower Miocene neritic limestones were located off the Trobriand Platform and on the inner wall of the New Britain Trench. Miocene bathyal sediments come from the Trobriand Platform; similar Pliocene rocks were recovered here as well as from the inner wall of the New Britain Trench and the central part of the Solomon Sea Basin. No reworked pre-Tertiary foraminifera are present in any sample.     

Tertiary foraminiferal rock samples from the western Solomon Sea

Rock fragments dredged from four R/VNatsushima stations contain Tertiary foraminifera. The oldest sample is an upper bathyal biomicrite of Early Eocene age (52 to 53.5 Ma) from the the Trobriand Platform. Upper Oligocene-Lower Miocene neritic limestones were located off the Trobriand Platform and on the inner wall of the New Britain Trench. Miocene bathyal sediments come from the Trobriand Platform; similar Pliocene rocks were recovered here as well as from the inner wall of the New Britain Trench and the central part of the Solomon Sea Basin. No reworked pre-Tertiary foraminifera are present in any sample.     

A multi-national,multi-parameter marine study of the western Solomon Sea and Region

A geological /geophysical survey of the western Solomon Sea and Manus Basin, northeastern Bismarck Sea, was carried out in 1983-84. The results of the survey and associated studies are reported in this issue and a later issue ofGeo-Marine Letters.     

A multi-national, multi-parameter marine study of the western Solomon Sea and Region

A geological /geophysical survey of the western Solomon Sea and Manus Basin, northeastern Bismarck Sea, was carried out in 1983-84. The results of the survey and associated studies are reported in this issue and a later issue ofGeo-Marine Letters.     

Sedimentary evolution and control factors of the Rizhao Canyons in the Zhongjiannan Basin,western South China Sea

Submarine canyon is an important channel for long-distance sediment transport, and an important part of deepwater sedimentary system. The large-scale Rizhao Canyons have been discovered for the first time in 2015 in the continental slope area of the western South China Sea. Based on the interpretation and analysis of multi-beam bathymetry and two-dimensional multi-channel seismic data, the geology of the canyons has however not been studied yet. In this paper, the morphology and distribution cha...     

Plate boundaries and evolution of the Solomon Sea region

The Solomon Sea Plate was widely developed during late Oligocene, separating the proto-West Melanesian Arc from the proto-Trobriand Arc. Spreading in the Bismarck Sea and in the Woodlark Basin resulted from interaction between the Pacific and Australian Plates, specifically from the collision of the proto-West Melanesian Arc with north New Guinea, which occurred after arc reversal. This model explains the extensive Miocene, Pliocene, and Quaternary volcanism of the Papua New Guinea mainland as it related to southward subduction of the Trobriand Trough. Our interpreted plate motions are concordant with the geological evidence onshore and also with complex tectonic features in the Solomon Sea Basin Region.     

Age of the Solomon Sea Basin from magnetic lineations

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.     

Age of the Solomon Sea Basin from magnetic lineations

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.     

The Trobriand Subduction System in the Western Solomon Sea

A south-dipping Subduction system which underlies the Trobriand Trough and 149° Embayment, on the southern margin of the Solomon Sea, is active or was recently active. Oceanic basement is overlain by 2.5 s, two-way travel time (TWTT), of sediment that shows at least two stages of deformation: early thrusts (inner wall) and normal faults (outer wall), and later normal faults that have elevated the outer trench margin. Thrust anticlines and slope basins are developed on the inner wall. The floor of the Solomon Sea Basin arches upward between the Trobriand Trough and the New Britain Trench to form isolated peaks and ridges in the east (152° Peaks) and an east-west Central Ridge in the west. Structures in the subduction system, and in the Solomon Sea Basin, plunge westward towards the point of collision with the New Britain Trench.     

南海海底地形的卫星测高数据反演

深入讨论了重力异常与海深的关系 ,在考虑地壳均衡补偿效应影响的基础上 ,推导了由重力异常用FFT技术计算海深的模型。最后 ,利用推导的模型联合测高卫星数据和海洋重力资料反演了中国南海 2 5′× 2 5′海底地形     

Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan)

The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s (SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density contrast of 10.25 g/cm³ between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry. As a final result, we present an enhanced GGM bathymetry model by integrating all available data.     

Petrology and mineral chemistry of sedimentary rocks from the Western Solomon Sea

Sedimentary rocks from the northern margin of the Trobriand Platform, the north wall of the New Britain Trench, and the floor of the Solomon Sea Basin are volcaniclastics, mudrocks, and neritic and bathyal limestones. Arc-volcanic debris from calc-alkaline or high-K magmatic sources is present at each locality. A minor metamorphic component occurs at one site on the Trobriand Platform which yielded Early Eocene to Middle Miocene material, and at the New Britain Trench site, which yielded Miocene or older and post-Miocene samples. Solomon Sea Basin samples are mudrocks which are apparently no older than Late Pliocene.     

Petrology and mineral chemistry of sedimentary rocks from the Western Solomon Sea

Multichannel seismic reflection profiles recorded in the northern Red Sea show structures that we interpret to be a result of the intrusion of uppermost Miocene salt. We believe that the evaporites are underlaid by attenuated continental crust and the flow of salt is due to renewed faulting of basement in the Pliocene when sea floor spreading began between latitudes 21°N and 15°30°N.     

东海陆坡不同类型海底峡谷的分布构造响应

利用1997-2001年在东海海域获得的多波束全覆盖测深数据和收集的部分高分辨率单道地震剖面,对东海陆坡海底峡谷的地形要素,如长度、弯曲度、平均坡度、剖面特征、头部和末端的水深等进行了详细的分析和统计.根据平面形态将海底峡谷划分为3种类型:直线型、蛇曲型和树枝型.海底峡谷主要分布于中段和南段的东海陆坡之上,平面形态特征总体上自北向南趋于复杂(直线型→蛇曲型→树枝型),规模逐渐增大,不同平面类型代表了峡谷不同的演化阶段.峡谷的分布格局和变化趋势主要受控于冲绳海槽扩张背景下的构造活动.     

Age estimation of the Solomon Sea based on heat flow data

Several heat flow measurements were made during the NAT83 cruise in the central part of the Solomon Sea Basin. The average value of 87 mW/m² (2.08 HFU) calculated from these and other data indicates that the age of the Solomon Sea Basin may range from 24 to 44 Ma. This is supported by the water depth, of approximately 4,500 m, versus age relationship. There is a possibility that the Solomon Sea Basin is not a back-arc basin associated with an arc but was formerly a relatively large oceanic plate. The agreement in age from both heat flow and water depth data favors the latter hypothesis.     

Age estimation of the Solomon Sea based on heat flow data

Several heat flow measurements were made during the NAT83 cruise in the central part of the Solomon Sea Basin. The average value of 87 mW/m² (2.08 HFU) calculated from these and other data indicates that the age of the Solomon Sea Basin may range from 24 to 44 Ma. This is supported by the water depth, of approximately 4,500 m, versus age relationship. There is a possibility that the Solomon Sea Basin is not a back-arc basin associated with an arc but was formerly a relatively large oceanic plate. The agreement in age from both heat flow and water depth data favors the latter hypothesis.     

Gravity, Mean Sea Surface, and Bathymetry Models Comparison in the Canary Islands

In geodetic and oceanographic studies generally, some reference surfaces are needed. These surfaces must represent as much as possible the gravity field of the Earth and the height/bathymetry systems. In the last years, several gravimetric, bathymetric, and mean sea surface models have appeared. Analyzing them it is possible to see that there are significant discrepancies between the models provided by different authors or organizations; there are also differences between the models and data obtained by independent measurements. We present the analysis of such differences and determine the most representative choice of models, in our opinion, for the Canary Islands region.     

Evolution of the western Barents Sea

Information from multichannel seismic reflection data complemented by seismic refraction, gravity and magnetics forms the basis for a regional structural and evolutionary model of the western Barents Sea during post-Caledonian times. The western Barents Sea contains a thick succession, locally > 10 km, of Upper Paleozoic to Cenozoic sedimentary rocks covering a basement of probably Caledonian origin. The area is divided into three regional geological provinces: (1) an east-west trending basinal province between 74°N and the coast of Norway; (2) an elevated platform area to the north towards Svalbard; and (3) the western continental margin. Several structural elements of different origin and age have been mapped within each of these provinces. The main stratigraphic sequence boundaries have been tentatively dated from available well information, correlation with the geology of adjacent areas, and correlation with the interregional unconformities caused by relative changes of sea level. The main structural elements were developed during three major post-Caledonian tectonic phases: the Svalbardian phase in Late Devonian to Early Carboniferous times, the Mid and Late Kimmerian phase in Mid Jurassic to Early Cretaceous times and Cenozoic tectonism related to the progressive northward opening of the Norwegian-Greenland Sea. The sediments are predicted to be of mainly clastic origin except for a thick sequence of Middle Carboniferous — Lower Permian carbonates and evaporites. Salt diapirs have developed in several sub-basins, especially in the Nordkapp Basin where they form continuous salt walls that have pierced through > 7 km of sediments.