bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composition and morphogenesis of the tubes of vestimentiferan worms
Authors: Shillito Bruce , Lechaire Jean-Pierre , Goffinet Gérard , Gaill Francoise 
Published: April 2008

Abstract

The structure and chitin-protein content of the tubes of different vestimentiferan species are compared.
Riftia pachyptila
and
Tevnia jerichonana
were collected at a hydrothermal vent site at 13°N on the East Pacific Rise;
Ridgeia piscesae
was from a hydrothermal vent site on the Juan de Fuca Ridge and
Lamellibrachia
sp. came from a cold seep on the Louisiana continental slope in the Gulf of Mexico. The tube ultrastructure shows chitin microfibrils organized in parallel bundles with various orientations. The chitin content varies considerably between species and is unrelated to seep or vent origin, whereas the protein content is much higher in the cold seep species than the hydrothermal vent species. All the species have specialized chitin secreting glands, as described for
R. pachyptila
. Based on this investigation, a tentative model of tube morphogenesis under cell control is proposed.
Geochemistry of the Snake Pit vent field and its implications for vent and non-vent fauna
Authors: Sudarikov S. M. , Galkin S. V. 
Published: April 2008

Abstract

Observations made during a cruise of the R/V
Professor Logachev
at the Snake Pit hydrothermal vent field provide a large database with which to examine the relationships between the geochemical characteristics of the hydrothermal sediments and the fauna that inhabit the area. Correlations between the nature and geochemistry of sediments, the distribution of hydrothermal and peripheral fauna and the hydrothermal activity are established. Three geochemical zones in the Snake Pit area are distinguished. (i) The Central Zone, located within 10–100 m of black smoker chimneys, consisting mainly of hydroxide-sulphide sediments with Fe sulphides predominant. Barite is found only in this zone and vent-associated organisms distinctly predominate over non-vent fauna. (ii) The Intermediate Zone encompasses high-temperature springs at a distance from 50 to 150 m. Sediments are chiefly sulphide-hydroxide composition and are dominated by Fe hydroxide and sulphide minerals in an oxide envelope. The non-vent specific fauna show maximum concentrations. (iii) The Outer Zone is located within a radius of 150–500 m from the smokers. The sediment composition is characterized by a predominance of sulphide-hydroxide transitional differences with notably varying compositions of oxide and sulphide minerals. Minor sestonophages prevail in the fauna, which is typical of communities with a pronounced oligotrophic structure. From the Central Zone towards the Outer Zone, the frequency of the bacterial mats seen on photographs decreases and the hydrothermal sediments show a similar trend. Analysis of the hydrothermal sediment obtained from the cores shows: (i) Mn is absent; (ii) barite is found only in the Central Zone; and (iii) chalcopyrite and pyrrhotite concentrations decrease and opal and quartz concentrations increase with increasing distance from the nearest smoker. Comparisons between the Mid-Atlantic Ridge hydrothermal fields of TAG, Snake Pit and 15°N indicate a decrease in the hydrothermal and biological activities with latitude (TAG, Snake Pit, 15°N), which might be due to their evolutionary history.
The molecular identification of early life-history stages of hydrothermal vent organisms
Authors: Dixon D. R. , Jollivet D. A. S. B. , Dixon L. R. J. , Nott J. A. , Holland P. W. H. 
Published: April 2008

Abstract
Amplification of diagnostic genomic DNA sequences using the highly sensitive polymerase chain reaction (PCR) technique provides a fast, sensitive and relatively inexpensive approach to species identification where there is a lack of diagnostic morphological characters. This applies particularly to the early life-history stages of marine invertebrates. Using PCR primers designed to amplify diagnostic length variants within phylogenetically widespread genes (in this case an expansion segment within the 28S rRNA gene), a first attempt is presented to produce a DNA database for use in the identification of hydrothermal vent larvae. In addition, a scanning electron microscopy study of particulates recovered from the neutrally buoyant plumes of hydrothermal vents on the Mid-Atlantic Ridge revealed evidence of biological material derived both from the vent environment and from the sea surface as marine ‘snow’. This investigation represents the first stage in the development of a bottom-mounted recorder to study the spatial and temporal aspects of larval dispersal in the hydrothermal vent environment. Larval dispersal processes are fundamental to the biogeography, genetics and evolution of the hydrothermal vent fauna.
Hydrothermal plumes: a review of flow and fluxes
Authors: Speer Kevin G. , Helfrich Karl R. 
Published: April 2008

Abstract
The physics of high-temperature hydrothermal venting and in particular the effects of the buoyancy flux on the background oceanic circulation are reviewed. The central theme is that the venting is dynamically active and forces oceanic flows on a variety of spatial and temporal scales. Vent fluid is not simply advected by the prevailing currents, but can actively set the scales of the flow. The cascade of scales (from fast to slow and small to large) discussed is: the buoyant plume, lateral spreading and mesoscale geostrophic vortices and the basin-scale plume. The focus is on models and observations relevant to the last two phases for which the Earth’s rotation plays a significant part. Some discussion of the observational requirements for the resolution of these flows is given. The fact that small-scale buoyant convection can drive flows on scales many orders of magnitude larger can have important effects on the dispersal of vent fluid, estimates of hydrothermal heat flux and the establishment and maintenance of vent field biological communities.
The link between sedimentary basin inversion and igneous underplating
Authors: Brodie James , White Nicky 
Published: April 2008

Abstract
There is now general agreement that many sedimentary basins on the northwest continental shelf of Europe underwent permanent exhumation during the Tertiary. The most dramatic indicator of this process is the present-day absence of up to 3 km of anticipated post-rift subsidence in the midlands of Britain and in the East Irish Sea. Any explanation must take into account the fact that the entire shelf has very small, long wavelength, free-air gravity anomalies. This constraint is of fundamental importance and implies either that the crust has been thickened, that phase changes have occurred within the lithosphere, or that low density material has been added to the lithosphere. Tertiary epeirogenic uplift and exhumation is often attributed to horizontal shortening which is assumed to be related in a general sense to Alpine mountain building. However, the removal of 3 km of sediment from a basin, which was originally 100 km wide, requires 20–30 km of shortening. Whilst minor Tertiary shortening is observed all over the continental shelf, nowhere is it sufficient to account for the inferred amount of denudation. More significantly, exhumation is thought to have commenced in the Early Tertiary and dramatically increases from south to north. Shortening is generally younger (mid-Tertiary) and decreases in intensity from south to north. Here we argue that Tertiary uplift and denudation are a consequence of regional igneous underplating. At the beginning of the Tertiary, rifting associated with the initiation of the Iceland plume generated substantial volumes of melt. Petrological arguments and the results from inversion of rare earth element concentrations of MgO-rich igneous rocks suggest that a minimum of 2–5 km of melt were produced beneath a substantial part of the continental shelf. We infer that much of this melt was trapped within the lithosphere, presumably close to the Moho, which would have acted as a density filter. Such underplating will have caused rapid surface uplift whilst maintaining isostatic equilibrium. Simple calculations based on deep seismic reflection data and the high P-wave velocities observed beneath Scotland are consistent with the petrological arguments.
The geometries and kinematics of inverted fault systems: a review of analogue model studies
Authors: McClay K. R. 
Published: April 2008

Abstract
The geometries and kinematics of 2D inverted extensional fault systems are reviewed using the results of scaled physical models together with case histories from inverted basin fault systems. 2D analogue models of detached terranes, listric, planar, ramp/flat listric and domino arrays of planar faults were constructed from homogeneous sandpacks and from anisotropic sand/mica layers. The models were first extended and then subjected to horizontal compression in order to reactivate the extensional fault systems. Upon extension simple listric faults produce a characteristic roll-over anticline and crestal collapse graben. Inversion of this system produces reactivation of the main detachment with the development of a fault-bounded wedge of syn-extensional strata elevated above regional together with tightening of the crestal collapse graben. New thrust faults initiate from the tips of the crestal collapse extensional faults. Characteristic ‘harpoon’ structures develop associated with the reactivation of the main detachment. Similar inversion architectures were also produced for the planar fault systems. Extension of ramp-flat listric fault systems produces an upper roll-over and crestal collapse graben together with a ramp syncline and lower roll-over and crestal collapse graben. Inversion of this system only reactivates a part of the main detachment producing a hangingwall shortcut fault that bypasses the upper roll-over system. Inversion of domino fault arrays produced characteristic harpoon geometries of the syn-rift wedge together with shortcut faults in the footwalls of the main domino faults.
Analysis of the progressive deformation during both extension and inversion has been carried out using marker points embedded in the models. In the analogue models of detached terranes hangingwall collapse during extension occurs along planar to curved shear surfaces, whereas upon inversion, different, lower angle shear trajectories are utilized. In the domino fault arrays more complicated shear paths are observed as a result of the footwall shortcut faults developed during inversion. These results have important implications for the analysis of extensional and inverted terranes and for fault reconstruction and section balancing techniques.
The architecture of inverted fault systems developed in the analogue models show striking similarities to the inverted basin geometries found in natural fault systems such as those in the North Sea and South East Asia. Examples from these terranes are compared and contrasted with the results of the analogue models. Conceptual models for inversion kinematics and fault system architectures are presented.
Estimating inversion: results from clay models
Authors: Eisenstadt Gloria , Withjack Martha Oliver 
Published: April 2008

Abstract
Physical models using wet clay show that, although both fold and fault geometries change with increasing amounts of inversion, it is difficult to estimate the magnitude of inversion. During extension, a listric main normal fault and a rollover fold cut by secondary normal faults developed above two diverging, basal plates. With 50 0nversion (4 cm extension, 2 cm shortening), the main normal fault underwent reverse displacement, and an asymmetric syncline formed in the pre-growth layers in the hangingwall. Secondary antithetic and synthetic normal faults passively rotated. Faults on the synclinal limb near the main normal fault rotated away from the fault, whereas those on the opposing limb rotated towards the fault. A broad anticline formed at shallow levels above the original half graben. Compressional reactivation of the main normal fault ceased between 50% and 100 0nversion (4 cm extension, 4 cm shortening). Instead, low-angle thrust faults with small displacements accommodated most shortening. The shallow anticline above the original half graben expanded laterally and vertically. With 200 0nversion (4 cm extension, 8 cm shortening), low-angle thrust faults with large displacements deformed the hangingwall and footwall of the main normal fault. Thrust faults cut the main normal fault and many of the secondary normal faults. The geometry of the hangingwall fold varied with depth. A broad anticline deformed the upper growth layers, changing to a syncline in the lower growth layers and an anticline in the pre-growth layers.
Estimates of inversion from null point analysis, amount of uplift above regional datum, or line length balancing, grossly underestimate the amount of shortening in the models. In addition, both the 50% and 100 0nversion models lack the large-scale deformation features typically associated with compression. These results suggest that both quantitative and qualitative techniques used to calculate inversion magnitude can significantly underestimate the amount of shortening. Furthermore, if the inversion uplift is eroded or if many small-scale deformation features are not imaged seismically, then inversion may go unrecognized.
A comparison of inverted basins of the Southern North Sea and inverted structures of the external Alps
Authors: Huyghe Pascale , Mugnier Jean-Louis 
Published: April 2008

Abstract
For several years, the relationships between extensional and contractional features have been studied in detail by numerous authors, and structural rules suggested regardless of the size and the geodynamic context of the inverted structures. Examples from the external part of the Western Alps and its foreland follow these rules (oblique-slip reactivation, buttress effect of normal faults, short-cuts, preserved half-grabens beneath decollement, forced folds, etc.), but are not controlled by the same geodynamic conditions as intra-plate inverted basins. The Jura platform, which is not controlled by extensional tectonics, shows fault reactivation, buttress effects and preserved structures beneath the decollement. Inverted structures are nicely illustrated in the Dauphinois domain of the stretched western Tethyan margin, but the effect of lithospheric weakening inherited from the stretching was reduced at the time of the Neogene shortening, and the maximum burial is induced by nappe loading. Therefore the relative timing of inversion tectonics, maximum burial and maximum temperature are very different in the Bourg-d’Oisans half-graben of the Dauphinois domain than for intra-plate inverted basins of the Southern North Sea, e.g. the Broad Fourteens Basin. Nonetheless, fold structures overlapped by major unconformities developed during early deformation events in restricted areas of the Western Alps. The example of structures in the Devoluy is linked to the inversion of the Vocontian basin, and is followed by a renewal of subsidence prior to the later Alpine shortening. Therefore, the Alps provide geometrical field examples of the interaction between stretching and shortening events, and may give some insight into the geometry of structures on the seismic scale. Intra-plate inverted basins provide examples of folded and faulted structures overlapped by sediments and provide a means of explaining the early shortening events that occurred in the Western Alps which were not related to the alpine evolution.
Structural analysis of the inverted Bristol Channel Basin: implications for the geometry and timing of fracture porosity
Authors: Nemčok Michal , Gayer Rod , Miliorizos Marios 
Published: April 2008

Abstract

The Bristol Channel basin was developed as an early Mesozoic half-graben, with the Bristol Channel fault zone (BCFZ) representing the principal down-to-the-south basin controlling structure. The basin was inverted during the Tertiary. This paper illustrates the application of structural analysis to the northern and southern margins of the Bristol Channel basin, where on shore medium- to small-scale structures provide analogues for the BCFZ. Throughout the outcrop four distinct structural mechanisms and associated fracture systems can be recognised. i) The oldest are normal faults, in many cases resulting from the reactivation of underlying WNW-ESE to NE-SW Late Palaeozoic Variscan thrusts. These are linked by N-S transfer faults and associated with WNW-ESE to ENE-WSW extensional veins. Evidence for synsedimentary development of both normal faults and extensional veins has been found in the Triassic and Lower Liassic sequences. Palaeostress analysis suggests an approximately NE-SW oriented σ
3
. ii) During inversion the normal faults acted as buttresses, forming WNW-ESE and younger NW-SE trending folds. Associated thrusts and oblique- to strike-slip faults reactivated the earlier transfer faults. The orientation of σ
1
was NE-SW during this deformation. iii) A regionally consistent system of NE-SW striking extensional veins formed at the close of the strike-slip inversion event. iv) Following primary inversion, lateral escape structures formed against the buttresses, with the development of oblique- and strike-slip faults in a variable and locally controlled stress field. Fracture porosity determined at sites throughout the outcrop show highest levels, up to 20%, formed in association with normal faults during the rifting event, but also significant amounts developed during the inversion event. Veins associated with strike-slip faulting of the latter give average porosities of 6.5%, whilst the later inversion-related extensional veins give average porosities of 0.8%. All these porosities show a high degree of directional permeability. It is argued that the oil generation window was reached during burial in the later stages of the rifting event, and that rapid polyphase fluid discharge from over-pressured fracture-bounded compartments allowed hydrocarbon migration into normal fault-related fracture porosity to form traps. The development of fracture porosity during inversion produced a long-lasting directed permeability and allowed many of the traps to drain. Only those traps associated with normal faults not directly affected by the inversion will have survived. A strategy to discover such a play requires a well targeted and detailed structural study.
3D analysis of inverted extensional fault systems, southern Bristol Channel basin, UK
Authors: Dart Chris J. , McClay Ken , Hollings Peter N. 
Published: April 2008

Abstract
East-West trending inverted extensional fault systems offset Triassic to Lower Jurassic strata close to the southern margin of the Bristol Channel basin along the north Somerset coast. Field mapping, using exceptionally detailed aerial photographs, has revealed a three phase tectonic evolution. (i) North South orientated stretching, resulting in a well developed extensional fault system. The faults are segmented, linked by relay ramps and horsetail toward their tips. (ii) North-South oriented compression, resulting in partial inversion of the extensional fault system, with the development of hangingwall buttress anticlines and zones of intense folding. (iii) North-South orientated compression, resulting in NW-SE trending dextral and NE-SW trending sinistral strike-slip faults. Comparison of hangingwall buttress anticlines exposed in North Somerset with similar larger scale structures observed on seismic profiles from the Bristol Channel shows that both are directly analogous. Correlation with regional data on the tectonic evolution southwest England, and the Bristol Channel, indicates that extension occurred during the Jurassic-Lower Cretaceous, and contractional inversion and strike-slip deformation during the Tertiary.
Inversion of an extensional-ramp basin by a newly formed thrust: the Cameros basin (N. Spain)
Authors: Guimerà Joan , Alonso Ángela , Mas José Ramón 
Published: April 2008

Abstract
The Cameros basin (Iberian Chain) was developed under a very subsident extensional regime during the latest Jurassic-Early Cretaceous. Its sedimentary fill constitutes a megasequence of more than 5000 m of vertical thickness which contains six depositional sequences. Most of the sediments are continental (alluvial and lacustrine) with only minor marine intercalations. A lateral accretionary geometry at the basin scale shows a SSW-NNE migration of the depocentre and an onlap to the north of the sedimentary sequences on the Mesozoic substratum of the northern boundary of the basin.
The overall Mesozoic structure of the basin, as seen from field studies and seismic profile interpretation, is a gentle WNW-ESE synclinorium 30–70 km wide and 150 km long. Extension in the pre-basin Mesozoic rocks is very small. The basin boundaries are defined by an unconformity of the basin filling rocks on the former Mesozoic substratum; it is bounded only locally by major faults at surface. The basin is interpreted as an extensional-ramp basin produced over an S-dipping ramp in a blind, flat-lying extensional fault some kilometres deep in the basement. The extensional displacement on the fault produced a synclinal basin which progressively widened with time. The depocentres of the successive depositional sequences were always located above the ramp and migrated to the north, inside the basin, as a result of the hangingwall displacement to the south. From a computer-modelled cross-section, we estimate the total displacement on the extensional fault to be about 33 km. This extension, in the hangingwall, would have taken place in the Pyrenean basin, north of the Cameros basin.
Tertiary compression (Palaeogene to Lower-Middle Miocene) inverted the basin by means of a newly formed E-W north-directed thrust. Overthrusting in the Tertiary Ebro basin fill, this new fault formed in the Keuper beds, in a weakness zone with uniform dip within the extensional hangingwall (about 30 km in cross-section). During the deformation it expanded to the north and south until it branched to the Iberian sole thrust, which might coincide with the Mesozoic extensional sole fault. Although this thrust produced a slight (2–3 km) inversion of the basement-Mesozoic cover unconformity, its maximum displacement was of about 28 km. Pre-basin Mesozoic rocks overlie the thrust surface and are overlain by the basin-filling rocks. A south-directed imbricate-fan thrust system developed in the southern margin. The total shortening was about 38 km, leading to the complete inversion of the basin.