bluuebunny/crossref_metadata_2025 huggingface dataset:
Review: Stratigraphy, meta‐stratigraphy and chaos
Authors: Bailey R.J.
Published: March 2003

An alternative approach to stratigraphic analysis is proposed. It takes as its starting point the simple general characteristics of the stratigraphic record and the complex, chaotic behaviours of the systems that combine to generate this record. In this context, Smith’s Stratigraphy Machine (SM) concept is developed. The SM is a chaotic global system, combining the operations of the atmosphere, hydrosphere, lithosphere and asthenosphere, which everywhere tends to self‐organize towards a critical state in which continuous loading of the system with rock waste, over time, is balanced by the unloading that creates the record. The outputs of the SM are simple and nonscale dependent in character, with residence times in the record ranging from a second, or less, to 1 billion years. However, only those long‐lived in the human time‐frame are judged to be of stratigraphic significance; and the range of residence times entails that the stratigraphic record embraces a similar range of hiatuses, or gaps.

 The value of the SM, as developed here, is that it can be regarded as a meta‐stratigraphic concept that transcends the usual frameworks of stratigraphic classification and interpretation and thus allows a reappraisal of significant features of the record such as its perceived cycles and sequences. There are three outcomes of this meta‐stratigraphic analysis. First, the geometric units employed in sequence stratigraphy are components of a self‐similar series of essentially lenticular bodies, with no fundamental characteristics to distinguish them from larger and smaller bodies in the generally self‐similar series. Secondly, the interactions and feedbacks within the SM are so complex, and its outputs so repetitive in general character, that it is dangerous to assume that any perceived cyclicity provides an unambiguous chronicle of process cyclicity, whether eustatic, climatic or tectonic. The classic coarsening upward cyclicity of shallow marine facies can, for example, be viewed solely as the outcome of the lack of phasing between the chaotic behaviours tending to unload the SM and those creating accommodation space. Finally, the meta‐stratigraphic approach reinforces the view that, in the absence of demonstrable stratal continuity, chronostratigraphic correlation must continue to rely on sample‐based, mainly biostratigraphical, methods, rather than sequence stratigraphy.
Did Yemeni Tertiary granites intrude neck zones of a stretched continental upper crust?
Authors: Geoffroy L. , Huchon P. , Khanbari K.
Published: March 2003

We demonstrate that the Miocene alkali granites of Yemen which emplaced along the Great Escarpment are contemporaneous with the stretching of the southern Red Sea continental crust. There is a gradient of Miocene extension towards the granites as well as a change of the geometry of tilted blocks around them. Geometrically, most of these granites seem to be emplaced passively in the necked areas of a stretched continental crust. These necked areas correspond to previous syn‐plume Oligocene NNW–SSE to N–S trending areas of localized extension marked by basaltic dyke swarms. These early extensional areas were associated with the emplacement of the flood basalt volcanic pile and were probably localized over large basement discontinuities.
Formation of the Trimouns talc‐chlorite deposit (Pyrenees) from persistent hydrothermal activity between 112 and 97 Ma
Authors: Schärer  , De Parseval  , Polvé  , De Saint Blanquat
Published: March 2003

For many economically important deposits, precise duration and age of hydrothermal ore‐formation are poorly known. We tackle these questions for the large Trimouns talc‐chlorite deposit by U–Pb analyses of xenotime and monazite, which crystallized within cm‐size geodes in the hanging wall dolostones. Formation of geodes and REE‐minerals occurred in relation to 300–350°C/0.2–0.3 GPa metasomatism along a host shear zone. Sixteen xenotime fragments, broken off from four single euhedral grains, define an age‐range from 112 to 97 Myr, and a monazite age of 99 Myr. Some ages of individual fragments are grain‐specific, whereas others show the same range of dates. Given the analytical uncertainties on individual fragments (about ± 1 Myr), the absence of inherited components, and the fact that no thermal event has affected these crystals after their formation, these ages are interpreted to record continuous crystallization between 112 and 97 Ma. This means that the Trimouns deposit was produced by hydrothermal activity lasting for at least 16 million years, occurring along a shear zone through which fluids continuously (or episodically) circulated to allow ion transport from the country gneisses to the deposit locality. Persistent deformation and high heat flow, related to the transtensional regime that opened the Bay of Biscay, seems to be the most likely tectonic scenario to explain this activity.
Early Ordovician terne‐linkages between oceanic and continental ternes in the central Scandinavian Caledonides
Authors: Sturt B.A. , Ramsay D.M.
Published: March 2003

The presence of a first‐order unconformity in the central part of the Scandinavian Caledonides, linking together early Ordovician/late Cambrian outboard oceanic ternes and the continental margin of Baltic, is of considerable importance for interpreting the geodynamic framework of the orogen. This and other criteria for terne linkage are described, together with implications for the regional tectonostratigraphic development in this segment of the Caledonides.
The crustal tongue melting model and the origin of massive anorthosites
Authors: Duchesne J.C. , Liégeois J.P. , Vander Auwera J. , Longhi J.
Published: March 2003

Recent detailed field studies in several anorthosite complexes have shown that anorthosites are frequently associated with weakness zones in the crust which may have favoured their emplacement at mid‐crust levels. Recent experimental data have shown that the parent magma compositions of various anorthosite massifs lie on thermal highs in the relevant phase diagrams at 10–13 kbar, indicating that these magmas cannot be derived by fractionation of peridotitic mantle melts but by melting of gabbronoritic sources in the lower crust at 40–50 km depths. In the Sveconorwegian Province terne boundaries have been traced in deep seismic profiles to Moho offsets or to tongues of lower crustal material underthrust to depths higher than 40 km. In Southern Norway, we suggest that a lithospheric‐scale weakness zone (the Feda transition zone?) has channelled the Rogaland anorthosites through linear delamination, asthenospheric uprise and melting of a mafic lower crustal tongue.
On the origin of fore‐arc basins: new evidence of formation by rifting from the Jurassic of Alexander Island, Antarctica
Authors: Macdonald  , Leat  , Doubleday  , Kelly
Published: March 2003

The Middle Jurassic–Lower Cretaceous Fossil Bluff Group of Alexander Island, Antarctica represents the fill of a fore‐arc basin unconformably overlying an accretionary complex. Like most fore‐arc basins, this example had been considered to have a passive origin, as a topographic hollow between the arc and the trench‐slope break. Recent discoveries of igneous rock coeval with sedimentation have altered this view. Oxfordian–Kimmeridgian basaltic and rhyolitic sills and lava flows are found in a restricted area at the north of the basin, within a single formation. Chemically, most basalts are high‐Nb types, which cannot have originated in a supra‐subduction zone setting. Since the age of emplacement of these rocks coincides with a gap in the record of plutonism in the Antarctic Peninsula volcanic arc, it is concluded that a late Jurassic pause in subduction led to active rifting to form the fore‐arc basin.
Depth of active bio‐alteration in the ocean crust: Costa Rica Rift (Hole 504B)
Authors: Furnes  , Muehlenbachs  , Tumyr  , Torsvik  , Thorseth
Published: March 2003

Bio‐alteration of basaltic glass in the oceanic crust has lately attained much attention. One of the many questions related to this topic is the depth at which bio‐alteration presently takes place in the oceanic crust. For this purpose we have investigated samples from the deepest drill hole, i.e. Hole 540B at the Costa Rica Rift in the eastern equatorial Pacific. The glassy rim of pillow lava samples show alteration textures and δ13C values compatible with microbial activity throughout the upper 500 m part of the volcanic succession. The concentration and distribution patterns of carbon and potassium within the microbially altered parts, however, indicate that microbes presently interact with the fresh glass to depths of about 380 m into the volcanic basement, at temperatures up to ≈100 °C.
The Early Cretaceous drowning unconformities of the Apulia carbonate platform (Gargano Promontory, southern Italy): local fingerprints of global palaeoceanographic events.
Authors: Graziano R.
Published: March 2003

Drowning successions which cap carbonate platforms and flanks bear palaeoenvironmental information which is useful for genetic stratigraphy; they constitute predictive key‐markers in regional to global correlations. An Early Cretaceous platform‐to‐basin transition has been investigated in Apulia (southern Italy) and two drowning unconformities, dated as early Valanginian and late early Aptian, have been documented. They occur at the base of thick pelagic tongues wedging toward the platform and mark the base of two depositional sequences showing distinct transgressive–regressive cycles. Timing of drowning processes, based on biostratigraphy and dynamic stratigraphy, allows the correlation of unconformities with global‐scale palae‐ oceanographic events marked, among others, by positive spikes of well‐established δ13C curves. Drowning signatures in the Apulia carbonates fit the stratigraphic, palaeoecological and possibly geochemical evidence found in global records at the same stratigraphic levels. Moreover, it is proposed that the observed drowning events were caused by palaeoceanographic crises affecting factory productivity.
Late Cretaceous India–Madagascar fit and timing of break‐up related magmatism
Authors: Torsvik T.H. , Tucker R.D. , Ashwal L.D. , Carter L.M. , Jamtveit B. , Vidyadharan K.T. , Venkataramana P.
Published: March 2003

A U–Pb zircon age of 91.2 ± 0.2 Myr from western India (St. Mary islands) confidently links India with the Late Cretaceous magmatic province in Madagascar (≈ 84–92 Ma), and the U–Pb age is within analytical error of the U–Pb age of the Analalava gabbro pluton (91.6 ± 0.3 Myr) in northeastern Madagascar. Palaeomagnetic data from India and Madagascar allow us to postulate a new India–Madagascar fit (Euler latitude = 14.24°, longitude = 38.8° and rotation angle = –69.2°). This fit is applicable to the Late Cretaceous, directly prior to and during the early phase of Madagascar–India separation. In our Late Cretaceous reconstruction, south‐west India runs roughly subparallel with the first known break‐up related magnetic anomaly (A34); it maintains a close connection between Mada‐gascar and India, but places India slightly rotated compared to the eastern margin of Madagascar and more northerly compared with some reconstructions. St. Mary magmatism is linked to the initial break‐up between India and Madagascar, and magmatism probably resulted from rift‐related extensional processes initially induced by the Marion hotspot underlying southern Madagascar during the Late Cretaceous.
Making ends meet in Gondwana: retracing the transforms of the Indian Ocean and reconnecting continental shear zones
Authors: Reeves Colin , De Wit Maarten
Published: March 2003

Interpretation of the detailed patterns of ocean‐floor transforms revealed by satellite altimetry enables the creation of the Indian Ocean to be described quantitatively as four consecutive plate‐tectonic regimes separated at 200, 136, 89 and 43 Ma. Each regime is reversed in turn by keeping transform termini coincident and colinear until conjugate points on the margins of pre‐existing plates regain their pre‐regime integrity. Progressive elimination of the Indian Ocean, demonstrable as a smooth computer animation (http://www.kartoweb.itc.nl/gondwana), leads to a refined re‐assembly of the continental fragments of central Gondwana that is substantiated by new geological data. A sequence of Euler interval poles that describes the dispersal of the Gondwana fragments, time‐calibrated against available magnetic anomaly data, is given. The model requires a mid‐Cretaceous position for India’s southern tip about 1000 km south of Madagascar, prior to India’s rapid northward migration.
Why Mt Etna?
Authors: Doglioni C. , Innocenti F. , Mariotti G.
Published: March 2003

The Etna volcano is located in an apparently anomalous position on the hinge zone of the Apennines subduction and its Na‐alkaline geochemistry does not favour a magma source from the deep slab as indicated for the Aeolian K‐alkaline magmatism. The steeper dip of the regional foreland monocline at the front of the Apennines in the Ionian Sea than in Sicily, implies a larger rollback of the subduction hinge in the Ionian Sea. Moreover, the lengthening of the Apennines arc needs extension parallel to the arc. Therefore, the larger southeastward subduction rollback of the Ionian lithosphere with respect to the Hyblean plateau in Sicily, should kinematically produce right‐lateral transtension and a sort of vertical ‘slab window’ which might explain (i) the Plio‐Pleistocene alkaline magmatism of eastern Sicily (e.g. the Etna volcano) and (ii) the late Pliocene to present right lateral transtensional tectonics and seismicity of eastern Sicily. The area of transfer of different dip and rollback occurs along the inherited Mesozoic passive continental margin between Sicily and the oceanic Ionian Sea, i.e. the Malta escarpment.
Timing and magnitude of displacement on the Altyn Tagh fault: constraints from stratigraphic correlation of adjoining Tarim and Qaidam basins, NW China
Authors: Meng Qing‐Ren , Hu Jian‐Min , Yang Fu‐Zhong
Published: March 2003

The Altyn Tagh fault plays an important role in growth of the north‐western Tibetan plateau, but the timing of its inception and magnitude of left‐lateral displacement are not well constrained. This study provides new independent constraints by correlating stratigraphic development and spatial distribution of the neighbouring Tarim and Qaidam basins. It is shown that the Tarim and Qaidam basins experienced quite similar stratigraphic and sedimentary evolution from late Sinian to early Palaeogene times. This fact indicates that the Tarim and Qaidam basins were a single block, at least until Oligocene time, which was then offset by the Altyn Tagh fault. Early Palaeozoic and Late Triassic suture zones within the East and West Kunlun and pinch‐outs of Mesozoic strata are chosen as piercing lines. Restoration of these lines gives total offset estimates of ˜ 350–400 km across the south‐western and central segments of the Altyn Tagh fault.
The Iberian Pyrite Belt: a mineralized system dismembered by voluminous high‐level sills
Authors: Boulter Clive A. , Soriano Carles , Zimman Pascale
Published: March 2003

The Iberian Pyrite Belt is a world‐ranking massive sulphide province in which a reassessment of the palaeovolcanology has dramatically changed understanding of the source of metals and mechanism of ore formation. In the northern sector, the deposits are hosted by a sill–sediment complex in which more than 90% of the sills post‐date the sulphide sheets. Because of a very high sill/sediment ratio, these late intrusions dominate the host succession and have severely disrupted the post‐mineralization configuration thus obscuring the true genetic relationships. For example, some oxide deposits have been separated by hectometric sills from sulphide deposits they originally capped, creating seemingly totally independent mineralizing systems. In addition, stratiform sulphide sheets without underlying stockworks are not necessarily allochthonous. An early timing for the mineralization with respect to volcanism means that metals had to be predominantly sourced from the sedimentary basin and the continental crust below the volcanogenic sequence.
The Variscan collage and orogeny (480–290 Ma) and the tectonic definition of the Armorica microplate: a review
Authors: Matte P.
Published: March 2003

The Variscan belt of western Europe is part of a large Palaeozoic mountain system, 1000 km broad and 8000 km long, which extended from the Caucasus to the Appalachian and Ouachita mountains of northern America at the end of the Carboniferous. This system, built between 480 and 250 Ma, resulted from the diachronic collision of two continents: Laurentia–Baltica to the NW and Gondwana to the SE. Between these two continents, small, intermediate continental plates separated by oceanic sutures mainly have been defined (based on palaeomagnetism) as Avalonia and Armorica. They are generally assumed to have been detached from Gondwana during the early Ordovician and docked to Laurentia and Baltica before the Carboniferous collision between Gondwana and Laurentia–Baltica. Palaeomagnetic and palaeobiostratigraphic methods allow two main oceanic basins to be distinguished: the Iapetus ocean between Avalonia and Laurentia and between Laurentia and Baltica, with a lateral branch (Tornquist ocean) between Avalonia and Baltica, and the Rheic ocean between Avalonia and the so‐called Armorica microplate. Closure of the Iapetus ocean led to the Caledonian orogeny: a belt resulting from collision between Laurentia and Baltica, and from softer collisions between Avalonia and Laurentia and between Avalonia and Baltica. Closure of the Rheic ocean led to the Variscan orogeny by collision of Avalonia plus Armorica with Gondwana. A tectonic approach allows this scenario to be further refined. Another important oceanic suture is defined: the Galicia–Southern Brittany suture, running through France and Iberia and separating the Armorica microplate into North Armorica and South Armorica. Its closure by northward (or/and westward?) oceanic and then continental subduction led to early Variscan (430–370 Ma) tectonism and metamorphism in the internal parts of the Variscan belt. As no Palaeozoic suture can be detected south of South Armorica, this latter microplate should be considered as part of Gondwana since early Palaeozoic times and during its Palaeozoic north‐westward drift. Thus, the name Armorica should be restricted to the microplate included between the Rheic and the Galicia–Southern Brittany sutures.
Tertiary compressional deformation of the Iberian plate
Authors: Sainz A. M. Casas , Faccenna C.
Published: March 2003

The Tertiary deformation of the Iberian plate is here interpreted as the result of changes in the coupling between the Iberian–African plates. During the early stages of the Africa/Iberia subduction (Palaeocene), deformation was confined at the Betic plate boundary. From the Eocene, during the collision in the southern plate margin, compressional deformation delocalized and distributed throughout the Iberian plate. First, in the Pyrenees, where the main stage of thrusting occurred during the Late Eocene – Early Oligocene. Then (mainly Oligocene – Late Miocene), in the inner part of the Iberian plate, forming basement uplifts in the Iberian Chain and the Central System, in correspondence of pre‐existing (Mesozoic and Variscan) structures. Finally, during the decay of compression inside the Iberian plate, extension took place the Mediterranean margin and the Alboran Sea.
Role of the backstop‐to‐cover thickness ratio on vergence partitioning in experimental thrust wedges
Authors: Storti Fabrizio , Marin Ruth Soto , Faccenna Claudio , Sainz Antonio Casas
Published: March 2003

The ratio between the thickness of the sedimentary sequences offscraped from the subducting plate (Hc) and the average thickness of the backstop (Hb) is expected to significantly influence vergence partitioning in thrust wedges. A series of simple sandbox experiments was performed to study the role of the Hc/Hb ratio in model thrust wedges. The results obtained show that thrust wedges with Hc/Hb values lower than 1 are essentially pro‐ward verging, with minor retro‐ward faulting; Hc/Hb values greater than 1 imply an increase of vergence partitioning. When a threshold value is exceeded, fully partitioned, doubly vergent thrust wedges develop. Comparison with natural submarine thrust wedges suggests that these experimental results may provide useful insights on the evolution of structural architecture at convergent margins.
Evolutionary cycles during the Andean orogeny: repeated slab breakoff and flat subduction?
Authors: Haschke M. R. , Scheuber E. , Günther A. , Reutter K.‐J.
Published: March 2003

Tectonomagmatic similarities between the modern Chilean flat‐slab region and pre‐Neogene magmatic episodes suggest that they represent analogues to flat subduction. Evolutionary patterns in each magmatic suite include (i) increasing La/Yb ratios and Sr‐and Nd‐isotopic enrichment through time, (ii) eastward‐migration of magmatism after periods of transpressional/transtensional intra‐arc deformation, and (iii) subsequent termination and virtual absence of main‐arc activity for 5–10 Myr. These patterns may reflect slab shallowing followed by flat subduction and thickening of the overlying crust. If repeated, they require interchanging episodes of slab steepening. Increasing convergence rates force slab kinking and eventual failure of the oversteepened slab, followed by rebound of the slab tip (owing to lack of further slab pull), flat subduction and termination of subduction‐related magmatism. Rapid subduction leads to shallow overriding of the detached slab fragment. Eclogitization of the gradually steepening slab tip at depth and subsequent slab pull permits asthenospheric corner flow and subduction‐related magmatism.
Imaging downward granitic magma transport in the Rogaland Igneous Complex, SW Norway
Authors: Bolle Olivier , Trindade Ricardo I. F. , Luc Bouchez Jean , Duchesne Jean‐Clair
Published: March 2003

Combining geological mapping and petrological, structural and geophysical (gravity and seismic) data already available for the late Proterozoic Rogaland Igneous Complex of Norway allows the 3D shape of the Bjerkreim–Sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks. Using the latter data, along with the spectacular convergent linear flow pattern that covers both the cumulates and the felsic rocks of this chamber, evidence is presented to show that the granitic material was down‐dragged through the sinking of its high‐density mafic floor into lower density anorthosites and granulitic gneisses. This example illustrates that downward gravity‐driven flows of rocks were active, in addition to upward flows, in the building of the early crust up to late‐Proterozoic times, helping to explain the geochemical and structural complexities of the old crust.
`Molar‐tooth microspar': a chemical explanation for its disappearance ∼ 750 Ma
Authors: Shields Graham A.
Published: March 2003

Molar‐tooth structures are intricately crumpled, microsparry calcite fissure fills that formed during the Precambrian. Strontium isotope stratigraphy constrains the last occurrence of volumetrically significant molar‐tooth structure (MT) in the geological record to ∼ 750 Ma. Although the disappearance of MT is commonly ascribed to the influence of metazoans on sediment cohesion, this now seems less plausible because there is no evidence for significant sediment disruption by metazoans before ∼ 550 Ma. It is proposed here that the most likely alternative explanation for MT disappearance is a change in ocean chemistry. A decrease in CaCO3saturation and/or an increase in the concentration of precipitation inhibitors in mid‐Neoproterozoic seawater may have contributed to MT disappearance, and might also help to explain the approximately contemporaneous decline in stromatolite diversity.
Asymmetric slip partitioning in the Sea of Marmara pull‐apart: a clue to propagation processes of the North Anatolian Fault?
Authors: Armijo Rolando , Meyer Bertrand , Navarro Sébastien , King Geoffrey , Barka Aykut
Published: March 2003

Between 1939 and 1999 the North Anatolian fault (NAF) experienced a westward progression of eight large earthquakes over 800 km of its morphological trace. The 2000‐km‐long North Anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale (∼10 Myr). The Sea of Marmara is a large pull‐apart that appears to have been a geometrical/mechanical obstacle encountered by the NAF during its propagation. The present paper focuses on new high‐resolution data on the submarine fault system that forms a smaller pull‐apart beneath the Northern Sea of Marmara, between two well‐known strike‐slip faults on land (Izmit and Ganos faults). The outstandingly clear submarine morphology reveals a segmented fault system including pull‐apart features at a range of scales, which indicate a dominant transtensional tectonic regime. There is no evidence for a single, continuous, purely strike‐slip fault. This result is critical to understanding of the seismic behaviour of this region of the NAF, close to Istanbul. Additionally, morphological and geological evidence is found for a stable kinematics consistent both with the long‐term displacement field determined for the past 5 Myr and with present‐day Anatolia/Eurasia motion determined with GPS. However, within the Sea of Marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull‐apart. The loading associated with the westward propagation process of the NAF may have provided a favourable initial geometry for such a slip separation.
Jurassic planktonic foraminifera from the United Kingdom
Authors: Oxford Melissa J. , Gregory F. John , Hart Malcolm B. , Henderson Andrew S. , Simmons Michael D. , Watkinson Matthew P.
Published: March 2003

Unequivocal planktonic foraminifera have been discovered in Oxfordian strata from Dorset and Scotland. These assemblages are, in part, coeval with previously reported occurrences of planktonic taxa in the Oxfordian of Normandy and Seine Maritime (France). Three species are now reported from the United Kingdom for the first time: Globuligerina oxfordiana (Grigelis, 1958), Haeuslerina helvetojurassica (Haeusler, 1881) and Compactogerina sp. cf. C. stellapolaris (Grigelis, 1977). There appears to be a close relationship between the distribution of these planktonic taxa in the UK and a marked sea‐level highstand.
Methane hydrate in the global organic carbon cycle
Authors: Kvenvolden Keith A.
Published: March 2003

The global occurrence of methane hydrate in outer continental margins and in polar regions, and the magnitude of the amount of methane sequestered in methane hydrate suggest that methane hydrate is an important component in the global organic carbon cycle. Various versions of this cycle have emphasized the importance of methane hydrate, and in the latest version the role of methane hydrate is considered to be analogous to the workings of an electrical circuit. In this circuit the methane hydrate is a condenser and the consequences of methane hydrate dissociation are depicted as a resistor and inductor, reflecting temperature change and changes in earth surface history. These consequences may have implications for global change including global climate change.

Terra Nova, 14, 302–306, 2002
Active continental subduction and crustal exhumation: the Taiwan orogeny
Authors: Lin Cheng‐Horng
Published: March 2003

ABSTRACT A tectonic model of active continental subduction followed by crustal exhumation is proposed to explain the orogeny in Taiwan. The subducted crust is represented by a low‐velocity zone dipping eastwards beneath the major part of Taiwan, while the exhumed crust is marked by a high‐velocity bulge, high heat flow and absence of seismicity beneath the eastern Central Range. The boundary between the subducted and exhumed crust has been identified from surface geology and analyses of thermal history across the Central Range. The dynamic force that has been driving the exhumed crust is identified by results from focal mechanisms, structural geology and geodetic survey in the eastern Central Range. Such a tectonic model may provide a good explanation for the evolution of the Taiwan Orogeny, as well as an active case for studying other long‐extinct systems of continental subduction and exhumation.
A reappraisal of the 1950 (Mw 6.9) Mondy earthquake, Siberia, and its relationship to the strain pattern at the south‐western end of the Baikal rift zone
Authors: Delouis B. , Déverchère J. , Melnikova V. , Radziminovitch N. , Loncke L. , Larroque C. , Ritz J. F. , San'kov V.
Published: March 2003

ABSTRACT The precise nature of the transition between the present‐day compressional tectonics in central Mongolia and extensional deformation in the central Baikal rift has still to be determined. For that purpose we have built a comprehensive earthquake focal mechanism data base for the Mongolia – southern Siberia area, from which we map the variations of the stress field. We focus our detailed investigations on the largest seismic event in the transition zone, the 1950 (Mw 6.9) Mondy earthquake, for which several discordant focal mechanisms have been proposed. Using a new approach in source inversion, we resolve the focal mechanism (left‐lateral strike slip type on a steep south‐dipping fault) and depth (14 ± 3 km) of the Mondy earthquake with a satisfactory accuracy. This seismological information, combined with the geological observations, allows us to decipher the connections between the 1950 mainshock, the local stress tensor and the active faults, which strongly suggest a partitioning of the deformation between two faults, namely the Mondy and Ikhe–Ukghun faults.
Terrestrial carbon‐isotope records from coastal deposits (Algarve, Portugal): a tool for chemostratigraphic correlation on an intrabasinal and global scale
Authors: Heimhofer Ulrich , Hochuli Peter A. , Burla Stefan , Andersen Nils , Weissert Helmut
Published: March 2003

ABSTRACT The carbon‐isotope signature of terrestrial organic matter (OM) offers a valuable tool to develop stratigraphic correlations for near‐shore deposits. A mid‐Cretaceous coastal succession of the western Algarve Basin, Portugal, displays a marked negative δ13C excursion ranging from − 21.2‰ to − 27.8‰ in the Early Aptian followed by two shifts towards higher values (up to − 19.3‰) during the Early and Late Aptian, respectively. The dominance of cuticle and leaf debris in the bulk OM fraction is confirmed by optical studies, Rock‐Eval pyrolysis and by comparison with the δ13C signature of four different types of fossilized land‐plant particles. Correlation of two terrestrial δ13Cbulk OM records from different study sites leads to a significant enhancement of the intrabasinal stratigraphic correlation within the Algarve Basin. Three prominent excursions in the Portuguese records can be correlated with existing δ13C curves from pelagic and terrestrial environments. The general carbon‐isotope pattern is superimposed by small‐scale fluctuations which can be explained by compositional variations within the OM.
Quartz fabric evidence for early Pan‐African penetrative east‐directed shearing in the Itremo Supracrustal Group of central Madagascar
Authors: Nédélec Anne , Bouchez Jean‐Luc , Grégoire Vincent
Published: March 2003

ABSTRACT The Pan‐African orogeny left a strong imprint on the basement rocks of Madagascar, which were metamorphosed up to granulite facies conditions. The supracrustal Itremo Group of central Madagascar, comprising quartzites, schists and carbonates of lower metamorphic grade, has to date been described as a folded sedimentary sequence. Despite their fine‐grained ‘sugary’ appearance, most quartzites are plastically deformed tectonites. Quartzite microstructures are mainly of the elongate mosaic type, indicating significant grain boundary migration, and are compatible with dynamic recrystallization under lower amphibolite facies conditions. Consistent asymmetric quartz c‐axis fabrics indicate a dominant top‐to‐the‐east shear sense. Hence, the Itremo quartzites bear evidence for a major eastward‐directed tectonic event of Pan‐African age, possibly resulting from an early Pan‐African thrust motion. Younger deformational events, responsible for localized mylonites with top‐to‐the‐WSW sense of motion and N–S‐trending folds and shear zones, were superimposed on this first fabric.
Maize C4 photosynthesis involves differential regulation of phosphoenolpyruvate carboxylase genes
Authors: Schaffner Anton R. , Sheen Jen
Published: March 2003

Maize as a C4 plant partitions CO2 fixation in two consecutive, spatially separated steps, thus eliminating photorespiration. The crucial enzyme for primary CO2 fixation is a C4‐specific phosphoenolpyruvate carboxylase (PEPC). The differential expression of the unique C4‐specific gene pepcZml and two non‐specific genes, pepcZm2A and pepcZm3B, in leaf, root, and stem is reported here. It is shown, in a transient homologous system, that this tissue‐specific regulation is mainly controlled by their distinct promoters. The light induction of the C4‐specific pepcZml in illuminated etiolated (greening) leaves probably relies on light‐dependent developmental changes instead of an immediate responsiveness found for other maize genes. Analyses of deleted, mutated, and hybrid promoters revealed the redundant nature of a 14mer which is repeated four times and a decisive function of the TATA box‐like motif, TATTT, and the sequences directly preceding it. No consensus sequences to other photosynthetic gene promoters were uncovered. Although light induces the expression of C4 PEPC and other photosynthetic genes in maize, this co‐ordination is apparently mediated through different signal transduction pathways and distinct regulatory elements. This study indicates that the acquisition of a new promoter is at least partially responsible for the C4‐specific expression of pepcZml essential for C4 photosynthesis.
Characterization of GmENOD40, a gene showing novel patterns of cell‐specific expression during soybean nodule development
Authors: Yang Wei‐Cai , Katinakis Panagiotis , Hendriks Peter , Smolders Arie , de Vries Floris , Spee Johan , van Kammen Ab , Bisseling Ton , Franssen Henk
Published: March 2003

In this paper, the soybean ‘early nodulin’ clone pGmENOD40 is characterized. The GmENOD40 encoded protein does not contain methionine and does not show homology to proteins identified so far. In situ hybridizations showed that this gene has a complex expression pattern during development of determinate soybean nodules. At early stages of development transcription is induced in dividing root cortical cells, the nodule primordium and the pericycle of the root vascular bundle. In mature soybean nodules, the gene is expressed in the uninfected cells of the central tissue and in the pericycle of the nodule vascular bundles. Studies on nodules devoid of intracellular bacteria and infection threads, showed that the expression of the gene in the nodule primordium is induced in these empty nodules, while the induction of the GmENOD40 gene in the nodule vascular bundle requires the presence of intracellular bacteria or infection threads. A pea cDNA clone homologous to GmENOD40 was isolated to enable in situ hybridization studies on indeterminate nodules. The expression patterns in both determinate and indeterminate nodules suggests that the ENOD40 protein might have a transport function.
cdc2MsB, a cognate cdc2 gene from alfalfa, complements the G1/S but not the G2/M transition of budding yeast cdc28 mutants
Authors: Hirt Heribert , Páy Aniko , Bögre Laszlo , Meskiene Irute , Heberle‐Bors Erwin
Published: March 2003

The product of the cdc2 gene encodes the p34cdc2 protein kinase that controls entry of yeast cells into S phase and mitosis. In higher eukaryotes, at least two cdc2‐like genes appear to be involved in these processes. A cdc2 homologous gene has previously been isolated from alfalfa and shown to complement a fission yeast cdc2ts mutant. Here the isolation of cdc2MsB, a cognate cdc2 gene from alfalfa (Medicago sativa) is reported. Southern blot analysis shows that cdc2MsA and cdc2MsB are present as single copy genes in different tetraploid Medicago species. cdc2MsB encodes a slightly larger mRNA (1.5 kb) than cdc2MsA (1.4 kb). Both genes were found to be expressed at similar steady state levels in different alfalfa organs. Expression levels of both cdc2Ms genes correlate with the proliferative state of the organs. Complementation studies revealed that in contrast to cdc2MsA, cdc2MsB was not able to rescue a cdc2ts fission yeast mutant. cdc2MsB was also unable to rescue a G2/M‐arrested cdc28ts budding yeast mutant which could be rescued by expression of the cdc2MsA gene. Conversely, cdc2MsB but not cdc2MsA was found to complement the G1/S block of another cdc28ts budding yeast mutant. These results suggest that cdc2MsA and cdc2MsB function at different control points in the cell cycle.
Cytology of infection of 35S‐bean chitinase transgenic canola plants by Rhizoctonia solani: cytochemical aspects of chitin breakdown in vivo
Authors: Benhamou Nicole , Broglie Karen , Chet Ilan , Broglie Richard
Published: March 2003

Transgenic canola plants containing high, constitutive levels of bean endochitinase have been shown to be more resistant to infection by the soil‐borne pathogen, Rhizoctonia solani, than are wild‐type plants that lack the chimeric chitinase gene. To determine whether the resistance of the 35S‐chitinase plants to Rhizoctonia infection results from an antimicrobial activity of the bean chitinase in planta, an ultrastructural and cyto‐chemical study was performed on infected control and transgenic canola plants. Analysis of root tissues of infected wild‐type canola plants revealed that R. solani was capable of extensive tissue colonization including the xylem vessels. Pathogen ingress towards the vascular system was associated with marked host cell wall alterations such as disruption of middle lamella matrices that occurred in advance of fungal penetration. Fungal hyphae colonizing these tissues appeared metabolically active as judged by their typical morphological features and their extensive multiplication. In infected transgenic plants, however, the pattern of fungal colonization was different to that observed in wild‐type plants. Penetration of the host cuticle and epidermis was frequently observed, but fungal colonization was usually restricted to the cortex although, in a few cases, some fungal cells could be seen in xylem vessels. In all samples examined, severe hyphal alterations ranging from increased vacuolization to cell lysis were seen. Hyphae occasionally seen in xylem vessels were markedly damaged and often reduced to convoluted wall fragments. Cytochemical labeling of chitin using the WGA/ovomucoid‐gold complex showed that hyphal alterations correlated with extensive chitin degradation. Thus, reduction in fungal biomass, increase in hyphal alterations leading to fungal lysis and chitin breakdown appear to be typical features observed in transgenic canola plants. Because these features were not seen in infected wild‐type plants, it is likely that constitutive expression of the bean endochitinase gene is, at least in part, responsible for the enhanced protection against fungal attack observed in these plants. It is not known, however, if other components of the host defense response contribute to the resistance phenotype.
Site‐directed mutagenesis of the organ‐specific element in the soybean leghemoglobin Ibc3 gene promoter
Authors: Ramlov Karsten Bak , Laursen Niels Bech , Stougaard Jens , Marcker Kjeld A.
Published: March 2003

The expression of a soybean leghemoglobin 5′Ibc3–GUS‐3′nos chimeric gene was analyzed in Lotus corniculatus after site‐specific mutagenesis of the nodulin consensus sequences, AAAGAT and CTCTT, present in the organ‐specific element (OSE) (−139 to −102). Full‐length promoters (−1956,+46) carrying clustered point mutations in the CTCTT sequence or in both the AAAGAT and the CTCTT sequences were inactive. Point mutations in the AAAGAT sequence had only minor effects on the expression level. Substitution of the ATTG sequence between the AAAGAT and the CTCTT sequences in the OSE reduced the activity in nodules to 10%. This, together with the conservation of the ATTGT sequence in the same position of leg‐hemoglobin genes from other legumes, indicates that these sequences, in addition to the nodulin consensus sequences of the OSE, are important for high‐level nodule‐specific expression. Substitution of the CTCTT sequences outside the OSE (−44,−40 and −79,−75) results in promoter activities of approximately 50%.
Structure and regulation of tobacco extensin
Authors: Memelink Johan , Swords Kathleen M.M. , de Kam Rolf J. , Schilperoort Rob A. , Hoge J. Harry C. , Staehelin L. Andrew
Published: March 2003

A tobacco cDNA clone (pCNT1) was characterized that encodes an extensin apoprotein almost entirely composed of the repeats Ser—Pro4(—Lys2), Pro—Tyr2—Pro2—His and Thr—Pro—Val—Tyr—Lys. In healthy plants extensin transcripts are abundant in the roots, less prevalent in the stem and rare in the leaves. In leaves extensin mRNA is induced by wounding, ethylene or virus infection. Tobacco was transformed with pCNT1 cDNA coupled in sense or antisense orientation to the CaMV 35S promoter. Analysis of transgenic plants that over‐ or underexpressed pCNT1 mRNA demonstrated that the encoded protein constituted the majority of hydroxyproline‐rich glycoproteins in roots, stems and leaves. The pCNT1‐encoded protein contained at least 50% of total hydroxyproline present in these organs and was abundant in the soluble protein fraction of stems and roots as well as in the cell wall of stem vascular bundles. Analysis of transgenic plants expressing sense or antisense extensin gene constructs showed no correlation between total hydroxyproline concentration or soluble HRGP content and plant development.
LAT52 protein is essential for tomato pollen development: pollen expressing antisense LAT52 RNA hydrates and germinates abnormally and cannot achieve fertilization
Authors: Muschietti Jorge , Dircks Lori , Vancanneyt Guy , McCormick Sheila
Published: March 2003

The LAT52 gene of tomato is expressed in a pollen‐specific manner. It is shown that LAT52 encodes a heat‐stable, glycosylated protein that traverses the secretory pathway when expressed in a baculovirus expression system. The LAT52 protein shows some similarity with Kunitz trypsin inhibitors and with pollen proteins from maize, rice and olive, but the biological function of these pollen proteins is unknown. To test whether the LAT52 protein plays an important role during pollen development, tomato plants were transformed with an antisense LAT52 gene driven by the LAT52 promoter. Because the LAT52 gene is expressed gametophytically, only 50% of the pollen of the primary transformants would be expected to express the antisense construct. Self‐progeny of 19 of the primary transformants showed the predicted 3:1 segregation for a single locus insertion of the linked kanamycin‐resistance gene. However, the self‐progeny of the other 32 primary transformants showed a 1:1 segregation pattern and could not transmit the linked kanamycin‐resistance gene through the male. A subset of these 1:1 segre. gation class plants was examined in detail. The pollen showed lower levels of LAT52 mRNA and LAT52 protein when compared with wild‐type. In vitro, approximately 50% of the pollen grains appear to hydrate abnormally; this anomaly is not present when the same pollen grains are Incubated in a medium with higher water potential. In vivo pollination experiments showed that the growth of around 50% of the pollen tubes is arrested in the style. The 3:1 segregation class plants showed no significant differences from untransformed control plants. Taken together, the results show a direct correlation between the reduced expression of LAT52 protein and abnormal pollen function, and suggest that the LAT52 protein plays a role in pollen hydration and/or pollen germination.
Hypersensitive response in cucumber mosaic virus‐inoculated Arabidopsis thaliana
Authors: Takahashi Hideki , Goto Nobuharu , Ehara Yoshio
Published: March 2003

The responses of 12 Arabidopsis ecotypes to cucumber mosaic virus strain Y (CMV(Y)) or strain O (CMV(O)) were characterized. Except for ecotype C24, all ecotypes were susceptible to both strains of CMV. In C24, CMV(O) multiplied systemically, but CMV(Y) did not spread systemically and induced only local necrotic spots in virus‐inoculated leaves 21–27 h after inoculation. In CMV(Y)‐inoculated C24 leaves, virus was confined to the inoculated leaves, and the amount of the pathogenesis‐related‐1 protein increased during the progress of local necrotic spot formation. These results indicate that C24 mounts a hypersensitive response (HR) to CMV(Y). By genetic analysis of crosses between C24 and ecotype Columbia or Landsberg (erecta) which are susceptible to CMV(Y) infection, the HR to CMV(Y) in C24 was found to be determined by a single major dominant gene whose function was influenced by a modifier gene from the Landsberg ecotype. Comparison of the responses between C24 leaves inoculated with pseudorecombinants of both strains of CMV suggested that the HR was controlled by CMV RNA3. The molecular interaction between the single major gene and CMV(Y) RNA3 is likely to induce the HR in CMV(Y)‐inoculated C24.
The barley 60 kDa jasmonate‐induced protein (JIP60) is a novel ribosome‐inactivating protein
Authors: Chaudhry Bushra , Müller‐Uri Frieder , Cameron‐Mills Verena , Gough Simon , Simpson David , Skriver Karen , Mundy John
Published: March 2003

The N‐terminal region of a 60 kDa, jasmonate‐induced protein of barley leaves (JIP60) is shown to be homologous to the catalytic domains of plant ribosome‐inactivating proteins (RIP). Western blotting of leaf extracts and in vitro reconstitution experiments indicate that JIP60 is synthesized as a precursor which is processed in vivo. This is in keeping with in vitro translation experiments indicating that a deletion derivative of the N‐terminal region, but not the putative precursor, strongly inhibits protein synthesis on reticulocyte ribosomes. The inhibition of ribosome function is associated with depurination of 26S rRNA, characteristic of plant RIPs. This indicates that JIP60 is a novel ribosome‐inactivating protein requiring at least two processing events for full activation. JIP60 derivatives do not significantly inhibit in vitro protein synthesis on wheat germ ribosomes. These and other results suggest that JIP60 may be involved in plant defence.
The aspartate aminotransferase gene family of Arabidopsis encodes isoenzymes localized to three distinct subcellular compartments
Authors: Schultz Carolyn J. , Coruzzi Gloria M.
Published: March 2003

Here, a complete study is described of all the genes and isoenzymes for aspartate aminotransferase (AspAT) present in Arabidopsis thaliana. Four classes of cDNAs representing four distinct AspAT genes (ASP1—ASP4) have been cloned from Arabidopsis. Sequence analysis of the cDNAs suggests that the encoded proteins are targeted to different subcellular compartments. ASP1 encodes a mitochondrial form of AspAT, ASP3encodes a chloroplastic/plastidic form of AspAT, whereas ASP2 and ASP4 each encode cytosolic forms of AspAT. Three distinct AspAT holoenzymes (AAT1—AAT3) were resolved by activity gel analysis. Organelle isolation reveals that AAT1 is mitochondrial‐localized, AAT3 is plastid‐localized, and AAT2 is cytosolic. Gene‐specific Northern analysis reveals that each Asp mRNA accumulates differentially with respect to organ‐type. However, the individual Asp mRNAs show no dramatic fluctuations in response to environmental stimuli such as light. Southern analysis reveals that four distinct nuclear genes probably represent the entire AspAT gene family in Arabidopsis. These molecular studies shed light on the subcellular synthesis of aspartate in Arabidopsis and suggest that some of the AspAT isoenzymes may play overlapping roles in plant nitrogen metabolism.