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21.
Active oceanic spreading in the northern North Fiji Basin: Results of the NOFI cruise of R/V L'Atalante (newstarmer project) 总被引：1，自引：0，他引：1
Yves Lagabrielle Etienne Ruellan Manabu Tanahashi Jacques Bourgois Georges Buffet Giovanni de Alteriis Jérôme Dyment Jean Goslin Eulàlia Gràcia-Mont Yo Iwabushi Philip Jarvis Masato Joshima Anne-Marie Karpoff Takeshi Matsumoto Hélène Ondréas Bernard Pelletier Olivier Sardou 《Marine Geophysical Researches》1996,18(2-4):225-247
The South Pandora and the Tripartite Ridges are active spreading centers located in the northern part of the North Fiji Basin. These spreading centers were surveyed over a distance of 750 km during the NOFI cruise of R/V L'Atalante (August–September 1994) which was conducted in the frame of the french-japanese Newstarmer cooperation project. SIMRAD EM12-dual full coverage swath bathymetric and imagery data as well as airgun 6-channel seismic, magnetics and gravity profiles were recorded along and offaxis from 170°40 E to 178° E. Dredging and piston coring were also performed along and off-axis. The axial domain of the South Pandora Ridge is divided into 5 first-order segments characterized by contrasted morphologies. The average width of the active domain is 20 km and corresponds either to bathymetric highs or to deep elongated grabens. The bathymetric highs are volcanic constructions, locally faulted and rifted, which can obstruct totally the axial valley. The grabens show the typical morphology of slow spreading axes, with two steep walls flanking a deep axial valley. Elongated lateral ridges may be present on both sides of the grabens. Numerous volcanoes, up to several kilometers in diameter, occur on both flanks of the South Pandora Ridge. The Tripartite Ridge consists of three main segments showing a sigmoid shape. Major changes in the direction of the active zones are observed at the segment discontinuities. These discontinuities show various geometrical patterns which suggest complex transform relay zones. Preliminary analysis of seismic reflection profiles suggest that the Tripartite Ridge is a very young feature which propagates into an older oceanic domain characterized by a significant sedimentary cover. By contrast, a very thin to absent sedimentary cover is observed about 100 km on both flanks of the South Pandora Ridge active axis. The magnetic anomaly profiles give evidence of long and continuous lineations, parallel to the South Pandora Ridge spreading axis. According to our preliminary interpretation, the spreading rate would have been very low (8 km/m.y. half rate) during the last 7 Ma. The South Pandora and Tripartite Ridges exhibit characteristics typical of active oceanic ridges: (1) a segmented pattern, with segments ranging from 80 to 100 km in length; (2) an axial tectonic and volcanic zone, 10 to 20 km wide; (3) well-organized magnetic lineations, parallel to the active axis; (4) clear signature on the free-air gravity anomaly map. However, no typical transform fault is observed; instead, complex relay zones are separating first-order segments. 相似文献
22.
John Connell 《New Zealand geographer》2018,74(2):92-100
In this century, sport has steadily become a more visible and marketable part of everyday life and of global political significance. States have consequently used sport as a means of soft power in order to develop a positive international presence and, usually to a lesser extent, affirm national identity. Sport diplomacy is usually associated with mega‐events and large states, but Fiji has used its prowess in rugby, and its Sevens victory in the 2016 Olympic Games, to promote itself globally, strengthen its national image and support government claims to legitimacy. The government emphasised Fijian values to construct a banal nationalism, in the face of ethnic divisions, and external concerns over repression of civil society. At least ephemerally, Fiji acquired new international recognition, and the government gained national legitimacy, indicating the expanding role of sport in geopolitics. 相似文献
23.
Geologie en Mijnbouw - Pteropoda (Mollusca, Gastropoda, Euthecosomata) described by Beets (1943, 1950, 1953) from the alleged Late Miocene/Early Pliocene asphaltic deposits of Buton (SE Sulawesi,... 相似文献
24.
A. B. Stephenson 《新西兰海洋与淡水研究杂志》2013,47(3):299-304
The composition and apparent social structure of a harem school of sperm whales Physeter catodon (Linnaeus 1758) is described from a mass stranding at Muriwai Beach, New Zealand, 29 October 1974. This school contained a total of 54 female whales accompanied by 17 immature males and a solitary full‐grown bull. Evidence is provided which supports the contention that sperm whales in this region of the Pacific reach the same lengths at sexual maturity and follow a similar breeding cycle to those found elsewhere in the southern hemisphere. 相似文献
25.
Takeshi Matsumoto 《Marine Geodesy》2013,36(3-4):265-272
Abstract Quantitative and objective trend analysis of bottom topography in order to detect the tectonic structures has become available by use of the processed Seabeam data. The following two procedures of trend analysis are introduced. (1) Edge detection procedures in digital image processing are applicable to the analysis of topography for extraction of the lineament of tectonic structures and prediction of the existence of faults based on the digital bathymetric data. (2) Automatic calculation of water flow using the topographic grid data is used for estimation of not only water flow pattern and volume but also the construction of the ridge or trough axis by calculating the accumulated water volume. This method was also applied to the Seabeam bathymetric data. This is quite useful for detection of offset structures and hidden faults. These two methods are applied to the topographic data obtained in the North Fiji Basin, which is characterized by active spreading ridges. The regional tectonic structure of the North Fiji Basin was found to be expressed by the topographic trend of the central axis. 相似文献
26.
《自然地理学》2013,34(5):418-426
The Navua River on the main island of Fiji displays anomalous drainage features and associated fluvial forms. The River course makes a right-angled bend approximately halfway along its course, beyond which it flows through a narrow gorge cut into hard volcanic rocks. Several tributaries enter the gorge as high cascades from hanging valleys. It is proposed that the former course of the palaeo-Navua River flowed east in a straight line along the modern Waidina River, and eventually discharged into Fiji's Rewa River system. Evidence for this is the presence of a spectacular dry gorge (a wind gap) at the head of the Waidina River. Previous ideas of river capture fail to explain the evolution of the local fluvial geomorphology. Instead, tectonic uplift probably dammed the palaeo-Navua and diverted it to its present short course to the sea. This new hypothesis provides a more plausible, simultaneous account for all the major fluvial geomorphic features, their geographical distribution and their relationship with geology in the Navua region. 相似文献
27.
Takayuki Tanaka Akira Imai Saori Egashira Sachihiro Sakomoto Kentaro Yasunaga Katsuhiko Maeda 《Resource Geology》2010,60(1):35-51
In the Namosi district, of Viti Levu Island, Republic of the Fiji Islands, we conducted chemical analysis on intrusive rocks and attempted to clarify the relationship between petrological characteristics and mineralization. Samples were collected from the Waisoi copper deposit, Waivaka corridor, Waisomo, Wailutelevu and Wainabama Southwest localities. The intrusive rocks in the district show the overall characteristics of calc-alkaline magnetite series. Using the normative composition diagram for granite classification, most of the intrusive rocks plot in the tonalite, granodiorite, quartz monzodiorite and quartz diorite fields. Rare earth element (REE) analysis revealed that at Waisoi the intrusive rocks tend towards an Eu positive anomaly, whereas most of those at Waisomo tend to have a negative anomaly. The (Cecn /Ybcn )/Ybcn ratio shows that the intrusive rocks in the Namosi district may be derived from a mantle origin magma possibly contaminated by crustal materials. Waisoi rocks have less contamination with continental crust and show higher gold content compared to those of the Waivaka corridor. The observed differences between Waisoi and Waivaka corridor in the Cu/Au ratio might also be caused by varying amounts of contamination by crustal materials. There is no clear correlation between the La/Yb ratio and K–Ar ages, however, the La/Yb ratio of the Waivaka corridor rocks has a wide range, suggesting a variable amount of crustal contamination of the magma from 7 to 5 Ma. The less crustal contamination and generation of relatively high silica contents under relatively oxidized conditions in the Waisoi magmas is correlated with Au-rich porphyry copper mineralization and in contrast more crustal contamination produced Au-poor porphyry copper mineralization at the Waivaka Corridor in the Namosi district. 相似文献
28.
29.
Geomorphological characteristics of slope failures in northeast Viti Levu island,Fiji, triggered by Tropical Cyclone Winston in February 2016 
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下载免费PDF全文 The highways circumnavigating Viti Levu play a pivotal role in Fiji's socioeconomic development, and are a crucial link to transport aid during disasters. Slope failures triggered by heavy rainfall and tropical cyclones have led to considerable damage and fatalities along Viti Levu's main roads in the past. Knowledge of slope instability mechanisms is key for the successful identification and management of slope failure hazards, however, there is a paucity of such information for Fiji's main roads. Severe Tropical Cyclone (STC) Winston was the strongest cyclone on record to make landfall in Fiji and affected the Fiji Islands from the early hours of 20 February until 3 am, 21 February, 2016. We present a field reconnaissance examining the characteristics and mechanisms of slope failures induced by STC Winston along a 35 km stretch of the northern part of the Viti Levu's ring road, “Kings Road”. Approximately 61 distinct shallow, small‐scale slope failures were identified most of which were of a complex type and included earth and debris slides (planar and rotational) with a minor flow component. The trigger for the slope failures was the ~258 mm of rainfall in 24 hours after 30‐days of antecedent rainfall totalling 482 mm. This caused rapid increases in porewater pressures, especially at the contact of residual soils and the underlying weathered basement rock. Evidence of recurring slips along Kings Road indicates that contemporary slope instability is likely caused by elevated porewater pressure during high intensity rainfall events in clay‐dominated soils. 相似文献
30.
Y. Lafoy J. M. Auzende E. Ruellan P. Huchon E. Honza 《Marine Geophysical Researches》1990,12(4):285-296
During the last three years, the North Fiji Basin (SW Pacific) has been intensively studied on three oceanographic cruises
carried out by French, American and Japanese ships. One of the main goals of these cruises was to study by means of precise
SeaBeam, SEAMARC II, seismic and magnetic surveys, the active spreading system and its associated hydrothermal processes.
The North Fiji basin, bounded by the major Pacific and Indo-Australian plates, shows a complex polyphased tectonic evolution.
One of the last phases of this evolution is the functioning since 3 Ma of a NS spreading center in the axial part of the basin.
The tectonic instability of the area resulted in a permanent rearrangement of the ridge axis. Among others, the 16°40′ S triple
junction is one of the major manifestations of such an instability. Sinistral strike-slip motion 1 Ma ago, along the North
Fiji Fracture Zone induced the change in direction of two segments of the axis from NS to N15 and N160. The first segment
is characterized by a typical spreading ridge similar to various parts of the EPR, while the second shows an atypical ‘en
echelon’ fan-shape opening. The N15 and N160 ridges converging with the North Fiji Fracture Zone constitute the 16°40′ S Ridge-Ridge-Fracture
Zone triple junction. The detailed morphologic and kinematic study of this junction allows us to understand one of the mechanisms
of the deformation in the North Fiji basin. 相似文献