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1.
Aruba, Bonaire, and Curaçao are islands aligned along the crest of a 200-km-long segment of the east-west-trending Leeward Antilles ridge within the broad Caribbean-South America plate boundary zone presently characterized by east-west, right-lateral strike-slip motion. The crust of the Leeward Antilles ridge represents the western segment of the Cretaceous-early Cenozoic Great Arc of the Caribbean, which obliquely collided, with the continental margin of northern South America in early Cenozoic time. Following the collision, the ridge was affected by folding and was segmented by oblique, northwest-striking normal faults that have produced steep-sided, northwest-trending, elongate islands and narrow shelves separated by deepwater, sediment-filled and fault-controlled basins. In this paper, we present the first fault slip observations on the Neogene carbonate rocks that cover large areas of all three islands. Our main objective is to quantify the timing and nature of Neogene to Quaternary phases of faulting and folding that have affected the structure and topography of this area including offshore sedimentary basins that are being explored for their petroleum potential. These data constrain three fault phases that have affected Aruba, Bonaire, and Curaçao and likely the adjacent offshore areas: 1) NW-SE-directed late Paleogene compression; 2) middle Miocene syndepositional NNW-SSE to NNE-SSW extension that produced deep rift basins transverse to the east-west-trending Leeward Antilles ridge; and 3) Pliocene-Quaternary NNE-trending compression that produced NW-SE-trending anticlines present on Aruba, Curaçao and Bonaire islands. Our new observations - that include detailed relationships between striated fault planes, paleostress tensors, and bedding planes - show that prominent bedding dips of Neogene limestone on Aruba, Bonaire and Curaçao were produced by regional tectonic shortening across the entire Leeward Antilles ridge rather than by localized, syndepositional effects as proposed by previous workers. We interpret Pliocene-Quaternary NNE-directed shortening effects on the Leeward Antilles ridge as the result of northeastward extrusion or “tectonic escape” of continental areas of western Venezuela combined with southeastward shallow subduction of the Caribbean plate beneath the ridge. 相似文献
2.
Julien Berger Renaud Caby Jean-Paul Liégeois Jean-Claude C. Mercier Daniel Demaiffe 《Contributions to Mineralogy and Petrology》2011,162(4):773-796
We show here that the Amalaoulaou complex, in the Pan-African belt of West Africa (Gourma, Mali), corresponds to the lower
and middle sections of a Neoproterozoic intra-oceanic arc. This complex records a 90–130-Ma-long evolution of magmatic inputs
and differentiation above a subducting oceanic slab. Early c. 793 Ma-old metagabbros crystallised at lower crustal or uppermost
mantle depths (25–30 km) and have geochemical characteristic of high-alumina basalts extracted from a depleted mantle source
slightly enriched by slab-derived sedimentary components ((La/Sm)N < 1; εNd: +5.4–6.2; 87Sr/86Sr: 0.7027–0.7029). In response to crustal thickening, these mafic rocks were recrystallised into garnet-granulites (850–1,000°C;
10–12 kbar) and subject to local dehydration–melting reactions, forming trondhjemititic leucosomes with garnet–clinopyroxene–rutile
residues. Slightly after the granulitic event, the arc root was subject to strong HT shearing during partial exhumation (detachment
faults/rifting or thrusting), coeval with the emplacement of spinel- and garnet-pyroxenite dykes crystallised from a high-Mg
andesitic parental magma. Quartz and hornblende-gabbros (700–660 Ma) with composition typical of hydrous volcanic rocks from
mature arcs ((La/Sm)N: 0.9–1.8; εNd: +4.6 to +5.2; 87Sr/86Sr: 0.7028–0.7031) were subsequently emplaced at mid-arc crust levels (~15 km). Trace element and isotopic data indicate that
magmas tapped a depleted mantle source significantly more enriched in oceanic sedimentary components (0.2%). Exhumation occurred
either in two stages (700–660 and 623 Ma) or in one stage (623 Ma) with a final exhumation of the arc root along cold P-T
path (550°C, 6–9 kbar; epidote–amphibolite and greenschist facies conditions) during the main Pan-African collision event
(620–580 Ma). The composition of magmas forming the Cryogenian Amalaoulaou arc and the processes leading to intra-arc differentiation
are strikingly comparable to those observed in the deep section of exposed Mezosoic oceanic arcs, namely the Kohistan and
Talkeetna complex. This evolution of the Amalaoulaou oceanic arc and its accretion towards the West African craton belong
to the life and closure of the Pharusian Ocean that eventually led to the formation of the Greater Gondwana supercontinent,
a similar story having occurred on the other side of the Sahara with the Mozambique Ocean. 相似文献
3.
Olivier Cuisinier Jean-Claude Auriol Tangi Le Borgne Dimitri Deneele 《Engineering Geology》2011,(3):187
Under a given compaction energy and procedure, it is known that maximum dry density of a soil is lowered due to lime addition. This modification of maximum dry density could alter the hydraulic conductivity of the soil. The main object of this study was to assess the impact of lime-stabilization on a silt soil microstructure and then on saturated hydraulic conductivity. An investigation at the microscopic level with mercury intrusion porosimetry showed that lime treatment induced the formation of a new small class, with a diameter lower than 3 × 103 Å in the compacted soil. This class is responsible for the difference in dry density between the treated and the untreated sample after compaction. It is shown that this small pores class was not altered by the compaction water content, the compaction procedure or the dry density. As in untreated soils, only the larger pores were modified by the compaction water content and the compaction procedure in the lime treated samples. The hydraulic conductivity appeared to be only related to the largest pores volume of the tested silt, regardless of lime treatment. Therefore, this study demonstrated that even if addition of lime resulted in a dramatic change of the maximum dry density of the tested silty soil, its effect on hydraulic conductivity is limited. 相似文献
4.
5.
Jean-Claude Dauvin Sandrine Alizier Carole Vallet Thierry Ruellet 《Estuarine, Coastal and Shelf Science》2010
Using a Before/During/After protocol, the effects of Port 2000 (the Le Havre harbour extension) on the suprabenthic communities in the Northern Channel of the Seine estuary (English Channel) were examined from March 2001 to March 2009. Since the beginning of Port 2000 construction in 2002, there have been several changes in the hydrological and sedimentary characteristics in the North Channel, including changes in current velocity, bottoms salinity and sand accumulation, as well as in the benthic communities themselves, moving from mud to medium and coarse sand communities. For the suprabenthos, changes were moderate, corresponding to an increase in species richness in the upper-part of the North Channel and a decrease in species density in the dominant mysids species (i.e., mainly Mesopodospsis slabberi) over time. Due to hydrological changes since the beginning of the Port 2000 project (several years of low freshwater input) it has been difficult to attribute the biological changes to Port 2000 construction only. In the future, the results obtained for the suprabenthos will have to be compared to those obtained for the macrobenthos. Similarly, since the suprabenthos is known to play an important role in the estuarine trophic chain, it will also be essential to estimate the fish distribution in the North Channel and to examine their stomach contents to evaluate the probable changes since the Port 2000 project began. 相似文献
6.
Jean-Marie Auzende Eiichi Honza Xavier Boespflug Satendra Deo Jean-Philippe Eissen Jun Hashimoto Philippe Huchon Junichiro Ishibashi Yo Iwabuchi Philip Jarvis Masato Joshima Kiyoyuki Kisimoto Yasuto Kuwahara Yves Lafoy Tsuyoshi Matsumoto Jean-Pierre Maze Kiyohiko Mitsuzawa Hiroyasu Monma Takeshi Naganuma Yukihiro Nojiri Suguru Ohta Kiyoshi Otsuka Yoshihisa Okuda Hélène Ondreas Akira Otsuki Etienne Ruellan Myriam Sibuet Manabu Tanahashi Takeo Tanaka Tetsuro Urabe 《Marine Geophysical Researches》1990,12(4):269-283
The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A
Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and
22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the
spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of
16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture
zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information
concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living
communities confirms this activity. 相似文献
7.
Combining indicator trends to assess ongoing changes in exploited fish communities: diagnostic of communities off the coasts of France 总被引:1,自引:1,他引:1
8.
Myriam Sibuet Luc Floury Anne-Marie Alayse-Danet Andr Echardour Tanguy LeMoign Roger Perron 《Progress in Oceanography》1990,24(1-4)
In order to make progress in the study of processes in deep-sea ecosystems, we have developed a strategy for the use of submersibles in conjunction with free vehicles. The BIOCYAN programme, which was conducted by French oceanographers at a permanent station in the Bay of Biscay, involved the use of submersibles for benthic ecological studies. It lead to the development of a variety of equipment for sampling and experimental studies. The submersible Cyana has a limited equipment workload, so the initial step was to develop a free vehicle which could function as a shuttle to act as an independent transport for equipment to be used from the submersible. Two other devices have been developed for sampling with precision the surficial layers of the sediment, one of which can be used in conjunction with an injection module to measure rates of processes in situ by incubations, following injection with labelled substrates. These devices, the free-lift shuttle, tube corers, a blade box corer and the associated injection module are described. 相似文献
9.
Nicolas Mazzella Josiane Molinet Agung Dhamar Syakti Jean-Claude Bertrand Pierre Doumenq 《Marine Chemistry》2007,103(3-4):304-317
This in situ study reports on the relevance of intact phospholipids as new biomarkers and highlights the limits of the classical fatty acid analysis after the hydrolysis of the polar lipid fraction. The analysis of polar lipid fractions revealed significant contributions of marine macrophytes with either non-phospholipid compounds (sulfoquinovosyl diacylglycerol) or with both non-bacterial phospholipid classes (phosphatidylcholine) and non-bacterial phospholipid molecular species (some molecular species of phosphatidylglycerol). The analysis of intact phospholipids showed also the predominance of gram-negative bacteria in sediments whereas the analysis of fatty acids alone cannot confirm such information. Lastly, as regard to the effects of petroleum hydrocarbons on the sedimentary bacterial communities, we observed a higher degree of saturation of the fatty acyl chains of the phospholipids extracted from sediment exposed to a massive and chronic crude oil contamination. Such a result was interpreted as an adaptive response resulting in higher membrane rigidity of the bacterial communities. 相似文献
10.
Since the beginning of formation of Proto-Taiwan, the subducting Philippine (PH) Sea plate has moved continuously through
time in the N307° direction with respect to Eurasia (EU), tearing the EU plate. The subducting EU plate includes a continental
part in the north and an oceanic part in the south. The boundary B between these two domains corresponds to the eastern prolongation
of the northeastern South China Sea ocean-continent transition zone. In the Huatung Basin (east of Taiwan), the Taitung Canyon
is N065° oriented and is close and parallel to B. Seismic profiles show that the southern flank of the canyon corresponds
to a fault with a normal component of a few tens of meters in the sediments and possible dextral shearing. Several crustal
earthquakes of magnitude >%6 are located beneath the trend of the Taitung Canyon and focal mechanisms suggest that the motion
is right-lateral. Thus, faulting within the sedimentary sequence beneath the Taitung Canyon is a consequence of underlying
dextral strike-slip crustal motions. As the continental part of the EU slab located north of B has been recently detached,
some subsequent dextral strike-slip motion might be expected within the EU slab, along the ocean-continent transition zone,
which is a potential zone of weakness. We suggest that the dextral strike-slip motion along the ocean-continent boundary of
the EU slab might trigger the observed dextral strike-slip motion within the overlying PH Sea crust and the associated faulting
within the sediments of the Huatung Basin, beneath the Taitung Canyon.
An erratum to this article is available at . 相似文献