Main differences between thrust belts     

Carlo Doglioni 《地学学报》1992,4(2):152-164

It is useful to differentiate between thrust belts that are related to east(E)-dipping or west(W)-dipping subduction. More precisely, these either follow or resist the overall ‘eastward’ mantle flow detected by the hot-spot reference frame. Because of the overall ‘westward’ drift of the lithosphere we find in E-dipping subduction that the basal decollement underlying the eastern plate reaches the surface and involves deep crustal rocks. With W-dipping subduction, however, we find that the basal decollement of the eastern plate is warped as well as subducted. Consequently thrust belts related to E- (or NE-) dipping subduction show conspicuous structural and morphologic relief, involve deep crustal rocks, and are associated with shallow foredeeps. On the other hand, thrust belts related to W- (or SW-) dipping subduction show relatively low structural and morphological relief, involve only shallow upper crustal rocks and are associated with deep foredeeps as well as back-arc extension. The accretionary wedge-foredeep-back-arc basin association is visualized as an overall eastward propagating tectonic wave. The accretionary wedge forms in the frontal parts and generally below sea-level. This is followed by forward migrating extension that cuts the earlier accretionary wedge. Typically such a system occurs in the context of overall W-dipping subduction and is characterized by an arcuate shape (e.g. Carpathians, Apennines, Barbados, etc.). Along the branches of the arc external transpression and internal transtension co-exist but with different sense (i.e. sinistral transpression contrasting with dextral transtension). We also observe that with W-dipping subduction the tangent to a pre- deformation marker is descending into the foredeep at an angle in the range of 1–10° while with E-(or NE-)dipping subduction the same marker would rise towards the hinterland with typical angles of about 5–10°. Foredeep subsidence is mainly controlled by the load of the thrust sheets in thrust belts due to E-(or NE-)dipping subduction and by the roll-back of the subduction hinge in accretionary wedges due to W-dipping subduction. Subsidence or uplift rates in the foredeeps and accretionary wedges related to the two different types of subduction are very different, providing different P-T-t paths in the two geodynamic realms. The present shape and structure of the thrust belts belonging to one of these two general types may help us in reconstructing the location of thinned lithosphere and basin evolution in the past.  相似文献   

Paleomagnetic evidence for a diachronic clockwise rotation of the Coastal Range, eastern Taiwan     

Teh-Quei Lee  Catherine Kissel  Eric Barrier  Carlo Laj  Wen-Rong Chi 《Earth and Planetary Science Letters》1991,104(2-4)

Paleomagnetic results obtained from over 2100 cores sampled at 132 early Pliocene to late Pleistocene sites in the Coastal Range of eastern Taiwan indicate that, since the late Pliocene, the margin of the Philippine Sea plate has undergone a clockwise rotation of about 30° as a direct consequence of the Plio-Pleistocene collision of this plate with the Chinese Continental plate. The rotation is diachronic and started between 3 and 4 Ma ago in the northern Coastal Range then propagated southward at an average speed of the order of 70 ± 10 km/Ma. This value is in very good agreement with estimates of the southward propagation of the collision between the Philippine Sea plate and the Eurasian margin in Taiwan. It is suggested that the rotation reflects the deformation of the Philippine Sea plate at depth and does not results from the shallow deformations involved in the building of the Coastal Range orogen.  相似文献   

Very hot,very shallow hydrothermal dolomitization: An example from the Maritime Alps (north‐west Italy–south‐east France)          下载免费PDF全文

Luca Barale  Carlo Bertok  Namam Salih Talabani  Anna d'Atri  Luca Martire  Fabrizio Piana  Alain Préat 《Sedimentology》2016,63(7):2037-2065

In the Maritime Alps (north‐west Italy – south‐east France), the Middle Triassic–lowermost Cretaceous platform carbonates of the Provençal Domain locally show an intense dolomitization. Dolomitized bodies, irregularly shaped and variable in size from some metres to hundreds of metres, are associated with tabular bodies of dolomite‐cemented breccias, cutting the bedding at a high angle, and networks of dolomite veins. Field and petrographic observations indicate that dolomitization was a polyphase process, in which episodes of hydrofracturing and host‐rock dissolution, related to episodic expulsion of overpressured fluids through faults and fracture systems, were associated with phases of host‐rock dolomitization and void cementation. Fluid inclusion analysis indicates that dolomitizing fluids were relatively hot (170 to 260°C). The case study represents an outstanding example of a fossil hydrothermal system, which significantly contributes to the knowledge of such dolomitization systems in continental margin settings. The unusually favourable stratigraphic framework allows precise constraint of the timing of dolomitization (earliest Cretaceous) and, consequently, direct evaluation of the burial setting of dolomitization which, for the upper part of the dolomitized succession, was very shallow or even close to the surface. The described large‐scale hydrothermal system was probably related to deep‐rooted faults, and provides indirect evidence of a significant earliest Cretaceous fault activity in this part of the Alpine Tethys European palaeomargin.  相似文献   

Sull'analisi periodale dei diagrammi     

Dr. Carlo Bernasconi 《Pure and Applied Geophysics》1950,16(3-4):181-187

Riassunto Dopo aver indicato un nuovo artificio per rendere più rapida la formazione di combinazioni selettive nella analisi periodale, si illustra un modello di analizzatore armonico che traduce con mezzi fotoelettrici gli schemi diLabrouste e diVercelli. Infine, si propone una variante costruttiva dell'analizzatore elettrico progettato dalLovera.

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Summary After having showed a new way by which the process for making the selective combinations used for periodical analysis is hastened, an harmonic analysing device which traducts with photoelectric means the schemes ofLabrouste andVercelli is illustrated. Further, a change in the construction ofLovera's electric analyser is proposed.

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Proiezioni cartografiche di carattere speciale     

Dr. Carlo Bernasconi 《Pure and Applied Geophysics》1953,24(1):5-10

Riassunto Si espone, attraverso la risoluzione di due problemi, un procedimento di carattere generale per la determinazione di proiezioni cartografiche della sfera, secondo il principio che a determinate linee sulla sfera corrispondano linee di prefissata equazione sulla carta. I problemi trattati sono i seguenti: 1) Determinare l'equazione di una carta a meridiani rettilinei e convergenti in cui le lossodromie siano rappresentate con linee rette. 2) Ricercare se esistono altre proiezioni, oltre la centrografica prospettica, che trasformano i cerchi massimi in rette.

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Summary Here is explained, through the solution of two problems, a procedure for the determination of the cartographic projections of the sphere, according to the principle that lines of a forfixed equation on paper correspond to determined lines on the sphere. Here are the problems in question: 1) To determine the equation of a rectilineal and convergent meridian lined paper in which the loxodromies are represented by straight lines. 2) To point out if there are other projections, besides the perspective centrographic one, turning maximum circles into straight lines.

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Monitoring meiobenthos using cm-, m- and km-scales in the Southern Bight of the North Sea     

Jian Li  Magda Vincx  Peter M.J. Herman  Carlo Heip 《Marine environmental research》1997,43(4):265-278

Meiobenthos at the mouth of the Grevelingen and Oosterschelde Estuaries in the Southern Bight of the North Sea was monitored using meiobenthic abundance and nematode community structure. Hierarchical sampling included 54 subsamples nested within 18 cores within six stations within two transects. The spatial patterns of the meiofaunal populations and communities are presented in cm-scale (among subsamples), m-scale (among cores), km-scale (among stations) and 10 km-scale (between transects). The variance components analysis of meiofaunal abundances showed that km-scale and 10 km-scale represented 63–90% of total variance while m-scale and cm-scale provided only 10–37%. Different communities were found among stations rather than among cores or subsamples by detrended correspondence analysis ordination and clustering analysis. The main assemblage of meiofauna occurred at the km-scale. Nematode diversity was more powerful than meiofaunal abundance in detecting spatial variation at all scales. However, at least two replicates are required for monitoring when sampling using a 10 cm² subsampling core.  相似文献   

The Meiobenthos Along a Mediterranean Deep-Sea Transect off Calvi (Corsica) and in an Adjacent Canyon     

Karline  Soetaert  Carlo  Heip Magda  Vincx 《Marine Ecology》1991,12(3):227-242

Abstract. Meiobenthos densities (excluding hard-shcllcd foraminifcrans) were compared along a Mediterranean deep-sea transect off Calvi (Corsica) and in an adjacent canyon. Chloroplastic Pigment Equivalent values (CPE) provided an estimate of the amount of primary production reaching the bottom.
The stations along the transect were characterized by a low CPE content of the sediment, decreasing with increasing station depth. CPE values in the canyon were much higher, which probably resulted from import of material from the adjacent bay of Calvi. Similarly, meiobenthos densities along the transect were much lower than at comparable depths along the canyon.
Meiobenthos density was significantly and positively correlated with CPE values.
Nematodes were the most abundant taxon at all stations, followed by copepods + nauplii and the soft-shelled foraminiferans. The meiobenthos was most abundant in the upper half centimeter. Nematode and foraminiferan densities tended to decline less rapidly with increasing depth into the sediment. Specimens belonging to the recently described phylum Loricifera, larvae of the parasitic crustacean class Tantulocarida, and fragments of an infaunal Xenophyophoria (large protozoans) are reported for the first time from the Mediterranean.  相似文献   

Ficopomatus'Reefs' in the Po River Delta (Northern Adriatic): Their Constructional Dynamics, Biology, and Influences on the Brackish-water Biota     

Carlo Nike  Bianchi Carla  Morri 《Marine Ecology》1996,17(1-3):51-66

Abstract. The serpulid polychaete Ficopomatus enigmaticus (F auvel , 1923) builds huge aggregates in the "Sacca del Canarin", a brackish inlet of the Po River Delta (Italy). Distribution, structure and development of these 'reefs'. together with their associated biota, were studied by field observations and settlement panels from 1977 to 1979. Some aspects of the serpulid biology (settlement periods, tube growth, life strategy) were also taken into account. Ficopomatus reefs influence in many ways the brackish-water ecosystem: they form the main hard substrate; are major sediment source; help in regulating the trophic status of the lagoon; and act as refuge for many invertebrate species.  相似文献   

Meiofauna and macrofauna community structure in relation to sediment composition at the Iberian margin compared to the Goban Spur (NE Atlantic)     

Els Flach  Agnes Muthumbi  Carlo Heip 《Progress in Oceanography》2002,52(2-4)

Meiofauna and macrofauna communities and several sediment characteristics were compared between a slope situated far from the coast (Goban Spur) and two transects across the Iberian Margin with steep slopes and close to the shore. The northern Galician transect (off La Coruña) was situated in an area subjected to wind-induced upwelling events. The western Galician transect was also subjected to upwelling, was additionally influenced by outflows of water rich in organic matter from the Rías Bajas. This transect also included the Galicia Bank. Macrofauna density decreased exponentially from the shelf edge (154 m) to the abyssal plain (4951 m) and different communities occurred on the shelf, the upper- and lower slope and on the abyssal plain. Apart from two extremely low-density stations on the Iberian Margin, there were no significant differences in the meiofauna between the Goban Spur and the Iberian Margin. Along the La Coruña-transect a station where meiofaunal densities were low occurred at a depth of 1522 m, where the sediment was characterised by having a high median-grain size, ripple structures, a low C_org and total N content. There were relatively high numbers of macrofaunal filter-feeders but low numbers of crustaceans, indicating a high current velocity regime. On top of the Galicia Bank (˜770 m) the sediment consisted mainly of shells of pelagic foraminifers, and had low contents of C_org and N. The macrofauna was dominated by filter-feeding and carnivorous taxa. At both these stations meiofauna densities were low. Meiofauna densities and community structure differed between the Goban Spur and the Iberian Margin. Meiofauna densities on the Galician shelf were more than double those on the Goban Spur shelf. The two deep stations on the La Coruña transect and the deepest station on the Galicia Bank transect all contained meiofaunal densities that were higher than found at similar depths off the Goban Spur. The meiofaunal densities were inversely correlated with %CaCO₃ content and, excluding the shelf stations, were positively correlated with both %C_org and total N at the Iberian Margin. Neither upwelling nor the enriched outflows from the rias affected the macrofauna, but meiofaunal densities were greatly enhanced.  相似文献   

The economic sustainability of artisanal fisheries: the case of the trawl ban in the Gulf of Castellammare, NW Sicily     

David Whitmarsh  Carlo Pipitone  Fabio Badalamenti  Giovanni D&#x;Anna 《Marine Policy》2003,27(6):489-497

Small-scale fisheries and the communities they support are often given the protection of designated fishing zones from which non-artisanal vessels are excluded. This paper looks at one example of this approach, the trawl ban introduced in the Gulf of Castellammare (NW Sicily), focussing on the economic sustainability of the artisanal fishery currently operating within the protected area. The consequences of lifting the trawl ban and how far this would jeopardise the sustainability of the artisanal fishery are explored via an analysis of the financial viability of trammel net vessels under alternative assumptions concerning catch rates. The paper also investigates fishermen's attitudes towards the trawl ban and their predisposition either to remain in the fishery or to quit in the event of the ban being removed.  相似文献