bluuebunny/crossref_metadata_2025 huggingface dataset:
The initiation of Waulsortian buildups in Western Ireland
Authors: Devuyst François‐Xavier , Lees Alan
Published: March 2003

The contact zone at the base of the Waulsortian (Upper Tournaisian) carbonate mud‐bank complex in western Ireland has been investigated at four localities spaced over a distance of 120 km. At all localities, a transition facies up to 3 m thick, characterized by several types of grumous (clotted and/or peloidal) carbonate muds, immediately underlies the Waulsortian facies. These muds show a developmental sequence provisionally interpreted as a necessary precursor to the formation of Waulsortian polymuds. Such pre‐bank precursors produced thin (a few decimetres) units of transition facies. The same mud types also persisted as an aureole around growing banks (mud‐mounds). Migration of the aureole during bank progradation produced thicker units of transition facies. The distribution of skeletal grain types in the Waulsortian banks, the transition facies and the ‘background’ argillaceous bioclastic limestones show two trends: one regional and one local. The regional trend is expressed by progressive north–south attenuation and, in some cases (for example, plurilocular foraminifera), the disappearance of organism groups. It parallels changes in Waulsortian Phases (defined by skeletal grain‐type assemblages) and is thought to indicate a southerly increase in water depth. The local trend, which occurs only in the two southern localities (deeper water), expresses differences between the skeletal grain content of the various lithofacies. These differences result partly from increased sensitivity to substrate texture by organism groups suffering southward attenuation (notably gastropods, hyalosteliid sponges, aoujgaliids, Earlandia and kirkbyacean ostracods) and partly from selective colonization, particularly of the transition facies, by tabulate corals and stick/ramose bryozoans. However, the developmental sequence of precursor carbonate muds is the same at all localities, indicating that the mud‐making process (probably microbial) was independent of water depth.
Slump‐initiated and controlled syndepositional sandstone remobilization: an example from the Namurian of County Clare, Ireland
Authors: Strachan Lorna J.
Published: March 2003

Remobilization of sandstones can dramatically reconfigure original depositional geometries and results in very unusually shaped sandstones, which resemble little, if any, of the original geometry. A number of deformational sandstone bodies, dykes and volcanoes from the upper part of the Carboniferous Ross Formation are described, which offer the opportunity to examine a suite of field‐scale reconfigured sandstones. These structures are located in close proximity to the Ross Slide, which outcrops along a 2‐km section on the northern coast of the Loop Head Peninsula, County Clare, Ireland. Dome‐ and ridge‐shaped deformational sandstone bodies, dykes and volcanoes are interpreted to be the product of remobilization of a turbiditic sandstone. Liquification and remobilization were triggered by translation, cessation and loading of the underlying turbiditic sandstone by the Ross Slide. Deformational sand body, dyke and volcano development occurred in an asynchronous fashion with deformational sand bodies formed during slump translation. Sand dykes and volcanoes developed after the cessation of slump movement. During slump translation, the minimum principal stress (σ3) was orientated vertically and the slump behaved in a `ductile' manner. After slump arrest, the minimum principal stress was oriented horizontally, and the unit regained shear strength to behave in a `brittle' manner. The relative change in rheological states with changing applied shear stress is indicative of thixotropic‐like behaviour within the slump mass. Ridge‐shaped deformational sand bodies are aligned parallel to slump folds, and their morphology is inferred to be controlled by compressional slump deformation associated with heterogeneous cessation of slump movement that was initiated by frontal arrest of the translating mass.
Stratigraphic evolution and preservation of aeolian dune and damp/wet interdune strata: an example from the Triassic Helsby Sandstone Formation, Cheshire Basin, UK
Authors: Mountney Nigel P. , Thompson David B.
Published: March 2003

Abstract New and previously published models of wet aeolian system evolution form a spectrum of types that may be explained in terms of aeolian dune dynamics, rate of water table rise and/or periodicity of interdune flooding. This is illustrated with an example from the Mid‐Triassic (Anisian) Helsby Sandstone Formation, Cheshire, UK. Lenses of damp and wet interdune strata exhibit an intertonguing, transitional relationship with the toe‐sets of overlying aeolian dune units. This signifies dune migration that was contemporaneous with water table‐controlled accumulation in adjacent interdunes. Downwind changes in the geometry and facies of the interdune units indicate periodic expansion and contraction of the interdunes in response to changes in the elevation of the groundwater table and episodic flooding, during which accumulation of dune strata continued relatively uninterrupted. This contrasts with other models for accumulation in wet aeolian systems where interdune flooding is associated with a cessation in aeolian bedform climbing and the formation of a bypass or erosional supersurface. Architectural panels document the detailed stratigraphy in orientations both parallel and perpendicular to aeolian transport direction, enabling a quantitative three‐dimensional reconstruction of genetically related aeolian dune and interdune elements. Sets of aeolian dune strata are composed of grainflow and translatent wind‐ripple strata and are divided by a hierarchy of bounding surfaces originating from oblique migration of superimposed dunes over slipfaceless, sinuous‐crested parent bedforms, together with lee‐slope reactivation under non‐equilibrium flow conditions. Silty‐mudstone and sandstone interdune units are characterized by wind ripple‐, wavy‐ and subaqueous wave ripple‐laminae, desiccation cracks, mud flakes, raindrop imprints, load casts, flutes, intraformational rip‐up clasts and vertebrate and invertebrate footprint impressions and trackways. These units result from accumulation on a substrate that varied from dry‐ through damp‐ to wet‐surface conditions. Interdune ponds were flooded by either fluvial incursions or rises in groundwater table and were periodically subject to gradual desiccation and reflooding. Red silty‐mudstone beds of subaqueous origin pass laterally into horizontally laminated wind‐ripple beds indicating a progressive transition from wet‐ through damp‐ to dry‐surface conditions within a single interdune.
Preservation of cross‐strata due to the migration of subaqueous dunes: an experimental investigation
Authors: Leclair Suzanne F.
Published: March 2003

This experimental investigation examined the controls on the geometry of cross‐sets formed by subaqueous dunes. A range of steady, unidirectional flow conditions spanning the field of dune existence was investigated, and aggradation rate ranged from 0 mm s−1 to 0·014 mm s−1. Data from an ultrasonic depth profiler consist of high‐resolution temporal and spatial series of bed profiles from which dune height and length, migration rate and the depth of trough scour were measured. Cross‐set thickness and length were measured from sediment peels. The size and shape of dunes from an equilibrium assemblage change continuously. Individual dunes commonly increase in height by trough scouring and, occasionally, by being caught‐up by the upstream dune. Both types of behaviour occur suddenly and irregularly in time and, hence, do not appear to depend on dunes further upstream. However, dune climbing or flattening is a typical response of dunes that disappear under the influence of the upstream dune. All types of behaviour occur at any flow velocity or aggradation rate. Successive dune‐trough trajectories, defined by dunes showing various behaviours, affect the geometry of the preserved cross‐sets. Mean cross‐set thickness/mean dune height averages 0·33 (±0·7), and mean cross‐set length/mean dune length averages 0·49 (±0·08), and both show no systematic variation with aggradation rate or flow velocity. Mean cross‐set thickness/mean cross‐set length tends to decrease with increasing flow velocity and Froude number, therefore allowing a qualitative estimation of flow conditions. Quantitative analysis of the temporal changes in the geometry and migration rate of individual dunes allows the development of a two‐dimensional stochastic model of dune migration and formation of cross‐sets. Computer realizations produced stacks of cross‐sets of comparable shape and thickness to laboratory flume observations, indicating a good empirical understanding of the variability of dune‐trough trajectories. However, interactions among dunes and aggradation rates of the order of 10−2 mm s−1 should be considered in future improved models.
Transport and deposition of pyroclastic density currents over an inhabited area: the deposits of the AD 79 eruption of Vesuvius at Herculaneum, Italy
Authors: Gurioli L. , Cioni R. , Sbrana A. , Zanella E.
Published: March 2003

Geological and volcanological studies were performed in the Herculaneum excavations, 7 km west of Vesuvius, Italy, to reconstruct the main features of the pyroclastic density currents and the temporal sequence of thead 79 eruptive events that destroyed and buried the town. The identification of two distinctive marker beds allows correlation of these deposits with the better‐known sequences to the south of Vesuvius, along the dispersal axis of the Plinian fall deposit. Detailed observations from stratigraphic sections show that the pyroclastic density current deposits are characterized by several sedimentary facies, each recording different depositional and emplacement mechanisms. Facies analysis reveals both lateral and vertical variations from massive to stratified deposits, which can be related to the combined effects of flow dynamics and local irregularities of the substratum at centimetre or metre scales. These topographic irregularities enhanced turbulence and allowed rapid transition from non‐turbulent to turbulent transport within the flow. Fabric data from these deposits, both from roof tile orientations and anisotropy magnetic susceptibility (AMS) analyses carried out on some of the pyroclastic deposits, suggest that the pyroclastic density currents were strongly affected by the presence of buildings. These obstacles probably caused deflection and separation of flows into multiple lobes that moved in different directions.
Cytotaxonomy of four species in the Simulium perflavum species group (Diptera: Simuliidae) from Brazilian Amazonia
Authors: Hamada Neusa , Adler Peter H.
Published: March 2003

Polytene chromosomes of four members of the Simulium perflavum species group in Brazil are described, and a standard map for the species group is presented. Simulium rorotaense Floch & Abonnenc, S. perflavum Roubaud and an undescribed species (S.‘X’) are chromosomally conservative, each representing a single species with a unique preimaginal habitat. Chromosomal, morphological and ecological evidence indicates that S. maroniense Floch & Abonnenc, previously considered synonymous with S. rorotaense, is a good species. Independent morphological and chromosomal analyses yielded 99.4% agreement in separating larvae of S. rorotaense and S. maroniense. The two species can be distinguished by gill morphology or by a subterminal inversion on the long arm of chromosome III. Simulium maroniense consists of at least four cytotypes, each with different sex chromosomes and autosomal polymorphism profiles and associated with a particular landscape type, altitude, temperature regime or geographical location. Simulium rorotaense and S. maroniense share one unique inversion, as do S. perflavum and S. ‘X’, indicating two pairs of sister species. The anthropogenic S. perflavum probably dispersed into Central Amazonia sometime after the mid‐1970s.
Molecular phylogeny of cockroaches (Blattaria) based on mitochondrial COII gene sequences
Authors: Maekawa Kiyoto , Matsumoto Tadao
Published: March 2003

Phylogenetic relationships among five cockroach families (Cryptocercidae, Polyphagidae, Blattidae, Blattellidae and Blaberidae) using seventeen species, were estimated based on the DNA sequences of the mitochondrial cytochrome oxidase subunit II (COII) gene. A cladogram inferred using the neighbour‐joining method indicated that Polyphagidae and Cryptocercidae are closely related to each other, and that these two groups are a sister group to the remaining cockroach families. The monophyly of this clade, however, was not strongly supported in terms of bootstrap percentages. Blaberidae and Blattellidae were shown to be sister groups as previously proposed, with Blattidae as a sister group to that clade. Non‐weighted and weighted parsimony analyses were also performed following analyses of nucleotide substitution patterns that indicated saturation of the COII gene among these taxa had occurred. These parsimonious cladograms suggested that Polyphagidae was the basal family, and Polyphaginae, including Cryptocercus as proposed by Grandcolas 1994a), was not monophyletic. The inferred relationships among cockroach families (Polyphagidae, Cryptocercidae + (Blattidae + (Blattellidae + Blaberidae))) is partly in agreement with some previously published analyses. Additionally, based on molecular data, Asian and American Cryptocercus are suggested to have diverged from one another before the Oligocene (∼20 mya).
Phylogenetic analysis of paraneopteran orders (Insecta: Neoptera) based on forewing base structure, with comments on monophyly of Auchenorrhyncha (Hemiptera)
Authors: Yoshizawa Kazunori , Saigusa Toyohei
Published: March 2003

Phylogenetic relationships among three paraneopteran clades (Psocodea, Hemiptera and Thysanoptera) were analysed based on the morphology of forewing base structure. Monophyly of Paraneoptera was supported by nine autapomorphies, monophyly of Condylognatha (= Thysanoptera + Hemiptera) by two autapo‐ morphies, monophyly of Thysanoptera by five autapomorphies and monophyly of Hemiptera by one autapomorphy. Thus, (Psocodea + (Thysanoptera + Hemiptera)) were proposed to be the phylogenetic relationships within Paraneoptera. A homoplastic similarity of the third axillary sclerite was observed between Thysanoptera and Heteroptera, and a possible evolutionary factor providing this homoplasy was discussed. The present analysis also suggested a monophyletic Auchenorrhyncha, and reduction of the proximal median plate was considered as an autapomorphy of this clade.
Morphology‐based phylogeny of the treehopper family Membracidae (Hemiptera: Cicadomorpha: Membracoidea)
Authors: Dietrich C. H. , Mckamey S. H. , Deitz L. L.
Published: March 2003

A parsimony‐based phylogenetic analysis of eighty‐three morphological characters of adults and immatures of seventy representatives of the tribes and subfamilies of Membracidae and two outgroup taxa was conducted to evaluate the status and relationships of these taxa. Centrotinae apparently gave rise to Nessorhinini and Oxyrhachini (both formerly treated as subfamilies, now syn.n. and syn.reinst., respectively, of Centrotinae). In contrast to previous analyses, a clade comprising Nicomiinae, Centronodinae, Centrodontinae, and the unplaced genera Holdgatiella Evans, Euwalkeria Goding and Antillotolania Ramos was recovered, but relationships within this clade were not well resolved. Nodonica bispinigera, gen.n. and sp.n., is described and placed in Centrodontini based on its sister‐group relationship to a clade comprising previously described genera of this tribe. Membracinae and Heteronotinae were consistently monophyletic. Neither Darninae nor Smiliinae, as previously defined, was monophyletic on the maximally parsimonious cladograms, but constraining both as monophyletic groups required only one additional step. The monophyly of Stegaspidinae, including Deiroderes Ramos (unplaced in Membracidae), was supported on some but not all equally parsimonious cladograms. More detailed analyses of individual subfamilies, as well as morphological data on the undescribed immatures of several membracid tribes and genera, will be needed to elucidate relationships among tribes and genera. A key to the subfamilies and tribes is provided.
Cave volume computed on the behaviour of a blowing well (Tournai basin, W. Belgium)
Authors: Massen  , Dusar  , Loy  , Vandenberghe
Published: March 2003

It is difficult to measure karst volume but important to do so to assess risk of sinkhole formation. Measurements of airflow and atmospheric pressure pattern on a water well in buried karst of the overexploited Tournai hydrogeological basin (Belgium) show that inflow and outflow are highly correlated to atmospheric pressure and the differences of external and internal air densities. The volume of natural voids in connection with the well within the vadose zone can best be estimated by a calculation based on outflow under constant atmospheric pressure, which suggests a possible cavity volume of 700 000 m3 indicating likelihood of sinkhole formation.
Recent intraplate stress field in the eastern Duero Basin (N Spain)
Authors: Cortés  , Maestro
Published: March 2003

Palaeostresses inferred from brittle mesostructures in the eastern Duero Basin show a recent stress field characterized by an extensional regime, with local strike‐slip and compressional stress states. Orientations of the maximum horizontal stress (
SHmax) show a relative scattering with two main modes: NNE to NE–SW and NW–SE. These orientations suggest the existence of two stress sources responsible for the dominant directions of the maximum horizontal stress in northeastern Iberia. Extensional structures within a broad‐scale compressional stress field can be related to both the decrease in relative stress magnitudes from active margins to intraplate regions and rifting proccesses ocurring in eastern Iberia. Stress states with NW–SE‐trending
SHmax are compatible with the dominant pattern established for western Europe. NE–SW orientations of
SHmax suggest the occurrence of tectonic forces coming from the Pyrenean zone. Geological and geophysical data indicate the existence of both orientations from the upper Miocene to the present‐day in NE Iberia.
Depth and modes of Pliocene–Pleistocene crustal extension of the Apennines (Italy)
Authors: Ghisetti F. , Vezzani L.
Published: March 2003

Since early Pliocene times the Apenninic chain has been dissected by normal faults propagating towards the Adriatic foreland. In the Tyrrhenian Sea extension involved deep crustal sections, whereas in the ‘Central Apennines Downfaulted Area’ it affected the shallow crust. The Tyrrhenian back‐arc domain is connected to the overall flexural retreat of the Adriatic–Apulia plate in front of the Apenninic collisional wedge. In the outer Apenninic belt thin‐skinned delamination and gravitational collapse occurred in the hanging wall of a thickened wedge, overthrusting the uplifted, buoyant crust of the Apulia foreland. Differential sinking velocity of the foreland plate results from the inherited competence contrast between the rigid Gargano–Apulia carbonate platform to the south, and the low‐competence lithology of the pelagic sequence of the Adriatic basin to the north. During late Messinian–early Pliocene times this palaeogeographical boundary acted as a lithospheric tear, separating segments of the Apulia plate subjected to different subduction modes.
Marine Sr (Ca) input in Quaternary volcanic rock weathering profiles from the Mediterranean coast of Morocco: Sr isotopic approach
Authors: Hamidi  , Nahon  , McKenzie  , Michard  , Colin  , Kamel
Published: March 2003

Carbonate commonly accumulates in weathering profiles developed on noncalcareous parent material under arid and semiarid climatic conditions. Such weathering profile types are widespread in Morocco, making it critical to know the sources of the calcium in order to understand the genesis of carbonate‐rich soils. In this study, we use 87Sr/86Sr as a geochemical tracer of the Ca sources in weathering profiles developed on volcanic rocks (basalt, tuff, andesite and latite) in the Mediterranean coast of Morocco. The results show that the most of the Sr, and hence Ca, is of an external origin, derived from (i) sea‐water for the profiles located near to the coast or (ii) sea‐water plus Liassic carbonate outcropping in the catchment for the profiles more distant from the coastline. The contribution of the host rock is small, being less than 25%. The ratio of the Sr (Ca) from the parent material to that from the external sources is controlled by the degree of porosity developed in the profile.
Sveconorwegian and Caledonian foreland basins in the Baltic Shield revealed by fission‐track thermochronology
Authors: Larson  , Tullborg  , Cederbom  , Stiberg
Published: March 2003

Fission‐track thermochronology has been applied to apatite, zircon and titanite from various depths of the Baltic Shield. Burial due to Sveconorwegian (Grenville) and Caledonian foreland sedimentation is revealed.

Titanite and zircon fission‐track ages from surface samples (from eastern Sweden) do not vary significantly and average ∼ 850 Myr. It is suggested that Sveconorwegian sediments reached a thickness of at least 8 km in eastern Sweden. Exhumation of these sediments was succeeded by deposition of Lower Palaeozoic cover rocks. Apatite fission‐track ages along a transect from SW to NE across the shield, increase from ∼ 300 Myr to ∼ 900 Myr and yield the Phanerozoic history of subsidence and exhumation. Apatite fission tracks, in the basement of the thickest parts of the foreland basin, were totally annealed. These results suggest a > 600 km wide Caledonian foreland basin filled by Devonian sediments that were > 2.5 km thick in southern and western Sweden, thinning to the east (in Finland).
Late Proterozoic tectonic events in southern Finland, constrained by 40Ar/39Ar incremental heating and single spot fusion experiments on K‐feldspars
Authors: Heeremans  , Wijbrans
Published: March 2003

The post‐Svecofennian tectonic development of southern Finland is controlled by intrusion of rapakivi granites (and associated rocks), reactivation of Svecofennian wrench zones, formation of sedimentary basins and successive intrusion of olivine dolerite dykes and sills. Relative age determinations have revealed that fault reactivation acted before, simultaneously and after intrusion of the rapakivi granites. Results of 40Ar/39Ar geochronometry of the Porkkala–Mäntsälä fault (30 km west of Helsinki) reveal ages predominantly in the range 950–1300 Myr. These ages are all significantly younger than the intrusion age of the rapakivi granites. It is suggested that these ages represent tectonic events related to the intrusion of olivine dolerite dykes and sills in SW Finland and the Sveconorwegian Orogeny active further west. 40Ar/39Ar ages of a sample taken from the Obbnäs granite (U–Pb zircon ages of 1645 ± 5 Myr) show ages predom‐inantly in the range of 1400–1550 Myr. These ages are suggested to represent either cooling ages of the granite or ages associated with the formation of the sedimentary grabens.
Early Palaeozoic rift‐related magmatism in Variscan Europe: fragmentation of the Armorican Terrane Assemblage
Authors: Crowley Q.G. , Floyd P.A. , Winchester J.A. , Franke W. , Holland J.G.
Published: March 2003

Early Palaeozoic bimodal rift‐related magmatism is widespread throughout much of the Variscides of Europe. It is traceable from the Polish Sudetes to NW Iberia. Granitic plutonism generally predates Cambro–Ordovician bimodal magmatism. In the N Bohemian Massif this early Palaeozoic granitic plutonism was generated by partial melting of Cadomian basement, whereas contemporaneous alkali granites with a mantle component are typical of the NW Iberian Massif. Silurian‐Devonian mafic magmatism in the N Bohemian Massif, Massif Central and NW Iberian Massif is partly preserved as obducted ophiolites. Compositional diversity displayed by Cambro‐Ordovician mafic magmatism can be accounted for by interaction between a spreading centre and an upwelling mantle plume. This indicates that combined tensional forces and mantle plume convection assisted the early Palaeozoic dispersal of terranes from the N Gondwana margin. Continued fragmentation resulted in development of an archipelago of related terranes separated by a network of seaways and formation of oceanic crust.
Observed correlations between aftershock spatial distribution and earthquake fault lengths
Authors: Nanjo K. , Nagahama H.
Published: March 2003

We observe the spatial distributions of the magnitude of aftershocks following the six earthquakes of focal depth shallower than 20 km with magnitude more than 5.0 from 1983 to 1987 in Japan. The upper limit of the aftershock magnitude is examined as a function of the distance from mainshock hypocentre. The observed spatial distributions of the upper limit are bimodal, with a tendency of the upper limit to decrease as the distance from mainshock hypocentre increases. Moreover, we observe the correlations between the aftershock spatial distribution and earthquake fault length. We focus on the largest aftershocks in each of two aftershock sequences constituting the bimodal distribution. The distances of the two largest aftershocks from the mainshock hypocentre are equal to the fault lengths of shallow earthquakes in Japan and to the maximum earthquake fault lengths.
Rodinia connections between Australia and Laurentia: no SWEAT, no AUSWUS?
Authors: Wingate Michael T. D. , Pisarevsky Sergei A. , Evans David A. D.
Published: March 2003

Although geological comparisons between Australia and North America have provided a basis for various Neoproterozoic Rodinia reconstructions, quantitative support from precisely dated palaeomagnetic poles has so far been lacking. We report U–Pb ages and palaeomagnetic results for two suites of mafic sills within the intracratonic Bangemall Basin of Western Australia, one of which is dated at 1070 ± 6 Ma and carries a high‐stability palaeomagnetic remanence. Comparison of the Bangemall palaeopole with Laurentian data suggests that previous reconstructions of eastern Australia against either western Canada (SWEAT) or the western United States (AUSWUS) are not viable at 1070 Ma. This implies that the Pacific Ocean did not form by separation of Australia–Antarctica from Laurentia, and that up to 10 000 km of late Neoproterozoic passive margins need to be matched with other continental blocks within any proposed Rodinia supercontinent. Our results permit a reconstruction (AUSMEX) that closely aligns late Mesoproterozoic orogenic belts in north‐east Australia and southernmost Laurentia.
Resolving Cambrian, Carboniferous, Permian and Alpine monazite generations in the polymetamorphic basement of eastern Crete (Greece) by means of the electron microprobe
Authors: Finger F. , Krenn E. , Riegler G. , Romano S. , Zulauf G.
Published: March 2003

The electron‐microprobe‐based investigation of accessory monazites in polished thin sections is a helpful tool in resolving the geochronology of a polymetamorphic basement. The method was applied to variably altered gneisses and micaschists from the retrogressed, originally amphibolite‐facies basement in eastern Crete (Greece). The presented data indicate that most monazite formed or recrystallized in response to high fluid activity during Alpine low‐temperature metamorphism. This low‐temperature monazite is characterized by distinctly low yttrium, uranium and thorium contents. However, older grains were able to survive in less retrogressed samples and have been traced with the electron microprobe, using microstructural and compositional criteria. In‐situ chemical Th–U–Pb dating of these pre‐Alpine monazites provides evidence for an igneous event in the Cambrian, and two different metamorphic events in the Carboniferous and Permian.
Short‐term environmental changes in the Cretaceous Tethyan Ocean: micropalaeontological evidence from the Early Albian Oceanic Anoxic Event 1b
Authors: Herrle J. O. , Pross J. , Friedrich O. , Hemleben Ch.
Published: March 2003

ABSTRACT To better understand the linkage between climate and ocean circulation under greenhouse conditions we have studied calcareous nannofossils, palynomorphs and benthic foraminifera from the Early Albian Oceanic Anoxic Event 1b black shale (OAE 1b) in the Vocontian Basin (SE France). We propose that monsoonal activity resulting from precessional forcing and modulated by eccentricity‐driven temperature changes represents the driving factor of OAE 1b formation in low latitudes. With the onset of OAE 1b, increasingly warm and humid conditions, stronger winds and enhanced terrestrial input led to higher surface water productivity. Therefore, increased productivity is an important factor for OAE 1b formation in the Vocontian Basin. However, monsoonally forced productivity changes are a regional climate signal only. The supraregional occurrence of the OAE 1b is probably due to a reduction of deep water formation in the low latitudes under extremely warm and humid conditions, leading to enhanced preservation of organic matter.
Characterization of the auxin‐regulated par gene from tobacco mesophyll protoplasts.
Authors: Takahashi Y , Kusaba M , Hiraoka Y , Nagata T
Published: March 2003

The auxin‐regulated par gene from tobacco mesophyll protoplasts was characterized in detail to deduce its possible function. An homology search of the par gene in the NBRF databases revealed that the par gene has homology to the stringent starvation protein (ssp) gene of Escherichia coli, which is induced under starved conditions and binds in an equimolar ratio to a holoenzyme of RNA polymerase. Hence, it is supposed that the par gene product could play a similar role to that of ssp. Although sequence homology of the par gene to the Gmhsp 26‐A gene from soybean was observed, both genes were shown to respond differently to plant hormones and stresses. Gmhsp 26‐A is induced by heat shock, 2,4‐dichlorophenoxyacetic acid (2,4‐D), cytokinin and abscisic acid (ABA), whereas the par gene was induced only by auxins. Furthermore, cycloheximide treatment prevents 2,4‐D‐mediated accumulation of Gmhsp 26‐A mRNA, but not that of par mRNA. Both par and Gmhsp 26‐A respond to CdCl2, but splicing of the par pre‐mRNA proceeded in a normal way, whereas splicing off the Gmhsp 26‐A pre‐mRNA was inhibited. Hence, the par and Gmhsp 26‐A genes should have a common ancestor, but have evolved in different directions. Detailed time‐course experiments confirmed that the par gene was induced immediately after the addition of auxin and expressed upon the initiation of meristematic activity in tobacco mesophyll protoplasts. As the par gene was induced by the sole treatment of cycloheximide, it was proposed that the par gene belongs to a category of 'superinduction' genes.(ABSTRACT TRUNCATED AT 250 WORDS)
A pathogen‐induced gene of barley encodes a protein showing high similarity to a protein kinase regulator.
Authors: Brandt J , Thordal‐Christensen H , Vad K , Gregersen PL , Collinge DB
Published: March 2003

A full length cDNA of a barley leaf messenger, found to increase in amount during infection attempts by the powdery mildew fungus (Erysiphe graminis), is characterized. The messenger encodes a polypeptide of 261 amino acid residues with a calculated mass of 29.2 kDa and a pI of 4.6. Sequence comparisons as well as serological studies demonstrate that the encoded protein is closely related to a family of mammalian proteins believed to have functions associated with the multifunctional Ca(2+)‐dependent protein kinases.
Hierarchical regulation of organ differentiation during embryogenesis in rice
Authors: Kitano Hidemi , Tamura Yasuaki , Satoh Hikaru , Nagato Yasuo
Published: March 2003

In plants, genetic mechanisms leading to shoot and root formation are almost unknown. Because basic body organization of such organisms is established during embryogenesis, induction and isolation of embryonic mutants is a promising approach to the study of plant development. The study of available embryonic mutants of rice indicates the existence of three major developmental processes taking place during embryogenesis before morphogenetic events start: determination of organ differentiation, positional regulation of organs and size regulation of the embryo. The consideration of specific rice mutants supports the existence of two types of mutations in each regulatory process, one affecting the embryo as a whole and the second concerning more restricted embryonal regions. A hierarchical type of control of rice embryogenesis is suggested.
A protein phosphatase 1 from Arabidopsis thaliana restores temperature sensitivity of a Schizosaccharomyces pombe cdc25ts/wee1− double mutant
Authors: Ferreira Paulo C.G. , Hemerty Adriana S. , Van Montagu Marc , Inzé Dirk
Published: March 2003

There is increasing evidence that the mechanisms controlling the eukaryotic cell cycle are regulated by protein phosphorylation/dephosphorylation cascades. The catalytic subunit of the protein phosphatase 1 is implicated genetically and biochemically in the complex network that regulates mitosis. To investigate further the cell division in plants, we have isolated and characterized two full‐length cDNAs from Arabidopsis thaliana, PP1A‐At1 and PP1A‐At2, encoding polypeptides highly homologous to known protein phosphatase 1 (PP1). DNA gel blot analysis suggests that the protein phosphatases 1 might form a small gene family in Arabidopsis. Northern analysis shows that transcripts are present in all plant organs. In cell cultures, the PP1 mRNA levels are differentially affected by treatment with drugs that block cell division. The expression of PP1A‐At1 in a Schizosaccharomyces pombe cdc25ts/wee1− double‐mutant strain restores temperature sensitivity, showing that the Arabidopsis phosphatase gene is capable of interacting with genes that regulate the fission yeast mitotic apparatus. However, the dis2‐11 S. pombe strain, which has a cold‐sensitive allele of the phosphatase 1 gene, is not rescued by expression of the PP1A‐At1 gene, suggesting that the plant cDNA is not a functional homolog of the fission yeast gene.
Tissue‐specific and wound‐inducible pattern of expression of the mannopine synthase promoter is determined by the interaction between positive and negative cis‐regulatory elements
Authors: Guevara‐García Arturo , Mosqueda‐Cano Gilberto , Argüello‐Astorga Gerardo , Simpson June , Herrera‐Estrella Luis
Published: March 2003

In transgenic tobacco plants the regulatory region of the Agrobacterium genes involved in mannopine synthesis (pmas) directs expression in vascular tissues and is induced upon wounding. To identify cis‐acting sequences required for the cell‐type‐specific and wound‐inducible expression of this regulatory region, the expression pattern of chimeric genes in which 5′ upstream deletions of the pmas1′ promoter direct the expression of the β‐glucuronidase coding sequence, was analyzed in transgenic tobacco plants. It was found that the pmas1′ promoter is specifically expressed in phloem cells and that this tissue‐specific pattern of expression is the result of the interaction of at least two negative regulatory elements with a positive element that directs expression in many cell types. It was also found that wound induction is mediated by two different mechanisms, one of them involving a dramatic change in tissue‐specific expression.
Limited proteolysis of (1,3)‐β‐glucan (callose) synthase from Beta vulgaris L: topology of protease‐sensitive sites and polypeptide identification using Pronase E
Authors: Wu Ayong , Wasserman Bruce P.
Published: March 2003

Plasma membrane (PM) vesicles of defined sidedness were obtained from Beta vulgaris L. and subjected to limited proteolysis to investigate the topology and subunit composition of UDP‐glucose: (1,3)‐β‐glucan (callose) synthase (CalS). Latency experiments demonstrated that protease‐sensitive sites on the CalS complex are located primarily at the cytoplasmic face of the PM, with little or no CalS inactivation occurring as the result of proteolysis at the apoplastic face. In the PM‐bound form, CalS activity was resistant to inactivation by Pronase E, however at least four polypeptides previously implicated as possible CalS components (92, 83, 57 and 43 kDa) were extensively hydrolyzed. Polypeptides of 31, 29 and 27 kDa resisted Pronase E hydrolysis and were also enriched in CalS fractions purified by glycerol gradient centrifugation and product entrapment. In contrast to PM‐bound CalS, purified CalS was rapidly hydrolyzed by Pronase E, indicating that most Pronase E‐sensitive sites are deeply embedded within the PM. This study provides direct biochemical evidence that hydrophobic integral membrane proteins oriented primarily towards the cytoplasmic face of the PM are important for callose biosynthesis in Beta. Furthermore, these results form the basis of a biochemically derived working model largely consistent with morphologically derived models proposed for intramembrane PM‐bound, microfibril‐synthesizing complexes in higher plants.
Gametophytic and sporophytic expression of an antherspecific Arabidopsis thaliana gene
Authors: Roberts Michael R. , Foster Gary D. , Blundell Robert P. , Robinson Susan W. , Kumar Amar , Draper John , Scott Rod
Published: March 2003

Genomic and cDNA clones of the anther‐specific APG gene from Arabidopsis thaliana and Brassica napus1 which encodes a novel proline‐rich protein, were isolated and characterized. Southern blotting and Northern analysis of male fertile and cytoplasmic male sterile varieties of B. napus showed that the APG gene is present as a single copy in the Arabidopsis genome, and that the B. napus APG gene is a member of a small anther‐specific gene family. Analysis of developmentally staged B. napus flower buds indicated that APG transcript is confined to the anther during the period of microspore development. Reporter gene fusions established that the APG promoter directs expression in a number of cell types in anthers of transformed plants. This expression is consistent with the temporal pattern of mRNA accumulation in B. napus buds and follows a complex developmental pattern. Most significantly, the promoter is active in both sporophytic and gametophytic cell types, with activity of the transgene in each cell type being delineated by various cytological markers.
Transgenic complementation of the hy3 phytochrome B mutation and response to PHYB gene copy number in Arabidopsis
Authors: Wester Lynn , Somers David E. , Clack Ted , Sharrock Robert A.
Published: March 2003

A recombinant PHYB minigene (mPHYB) consisting of the complete Arabidopsis PHYB cDNA sequence fused to 2.3 kb of upstream PHYB promoter sequence has been introduced into wild‐type Arabidopsis and into a strain containing the Bo64 allele of the hy3 mutation. The Bo64 mutant has previously been shown to contain a nonsense mutation in the PHYB coding sequence. Transformation of this strain with the mPHYB gene results in complementation of all of the mutant phenotypic characteristics tested including hypocotyl length and hypocotyl cell size, response to end‐of‐day far‐red light, leaf morphology, chlorophyll level, and flowering time. Presence of the mPHYB transgene in a wild‐type genetic background causes exaggeration of this same set of phenotypic characteristics, indicating that these diverse photomorphogenic responses are sensitive to the copy number of the PHYB gene. The transgene inserts in the Bo64(mPHYB) and WT(mPHYB) lines are shown to be single locus and single copy and the immunologically detectable level of phytochrome B is shown to vary linearly with PHYB gene copy number. These results demonstrate a complex role for phytochrome B in Arabidopsis photomorphogenesis and suggest that the expression level of this phytochrome gene is an important determinant of the intensity of light‐induced plant responses.
Co‐suppression of the petunia homeotic gene fbp2 affects the identity of the generative meristem
Authors: Angenent Gerco C. , Franken John , Busscher Marco , Weiss David , Van Tunen Arjen J.
Published: March 2003

The function of the petunia MADS box gene fbp2 in the control of floral development has been investigated. Inhibition of fbp2 expression in transgenic plants by a co‐suppression approach resulted in the development of highly aberrant flowers with modified whorl two, three and four organs. This mutant flower phenotype inherited as a single Mendelian trait. The flowers possess a green corolla which is reduced in size. Furthermore, the stamens are replaced by green petaloid structures and the inner gynoecial whorl is dramatically reduced. No ovules or placenta are formed and instead two new inflorescences developed in the axils of the carpels. These homeotic transformations are accompanied by a complete down‐regulation of the petunia MADS box gene fbp6 which is highly homologous to the Arabidopsis and Antirrhinum genes agamous (ag) and plena (ple). In contrast to this, two other petunia MADS box genes, exclusively expressed in whorls two and three, are still transcribed. Our results indicate that the fbp2 gene belongs to a new class of morphogenesis genes involved in the determination of the central part of the generative meristem.
Complex spatial and temporal expression of lipoxygenase genes during Phaseolus vulgaris (L.) development
Authors: Georg Eiben Hans , Slusarenko Alan J.
Published: March 2003

A new member (Lox1) of the lipoxygenase (LOX) gene family in French bean was isolated and its specific expression compared to the general expression pattern of related LOX genes. LOX transcripts detected by a French bean cDNA LOX probe were generally abundant in young, developing tissues, and LOX protein, detected on immunoblots showed a similar distribution. Tissue prints showed that cell‐specific, locally high amounts of LOX protein were observed in some tissues, for example in parts of the starch sheath in the hypocotyl and a cell layer in the pericarp.

The Lox1 gene from Phaseolus vulgaris was shown in genomic Southerns to be present as a single copy per haploid genome. RNase protection studies showed that the gene is active and the transcription start site was mapped by cDNA primer extension. RNase protection studies showed that Lox1 mRNA was present only in flowers and embryonic primary leaves, in stems and most strongly, in young secondary leaves but not in any of the other organs tested (i.e. not in roots, nodules, hypocotyls, cotyledons, older secondary leaves, pericarp or seeds). Lox1 gene transcripts did not accumulate in leaves in response to methyl jasmonate or pathogen inoculation, even though these treatments caused the accumulation of other LOX transcripts. Thus, the various lipoxygenase genes are regulated differentially during French bean development and in response to different stress stimuli, and possible functions are discussed in view of the specific expression patterns observed.
Carbohydrate binding activities of Bradyrhizobium japonicum III. Lectin expression, bacterial binding, and nodulation efficiency
Authors: Ho Siu‐Cheong , Wang John L. , Schindler Melvin , Loh John T.
Published: March 2003

In previous studies, evidence that the Bradyrhizobium japonicum lectin, designated BJ38, mediated the observed carbohydrate‐specific binding activities of the bacteria, including the saccharide‐specific adhesion to soybean root cells was presented. In the present study, it is found that both B. japonicum, as well as the purified BJ38, bind predominantly to young emergent root hairs of soybean roots and, to a much lesser extent, to the root cap, mature root hairs, epicotyl or hypocotyl regions. Thus, the region of preferential binding for both the bacteria and the isolated lectin coincide with the region of the soybean root most susceptible to B. japonicum infection. The importance of bacterial binding for the nodulation process was studied by comparing the nodulation efficiency of binding‐deficient mutants N4 and N6 to the wild‐type. These mutants had been shown to be defective in carbohydrate recognition, as represented by their diminished ability to bind to soybean roots. BJ38 was immunolocalized to one pole of the cell surface of wild‐type B. japonicum, but no surface labeling could be detected on either mutant. Moreover, both N4 and N6 showed a substantial decrease in nodulation activity, relative to the wild‐type. These results provide additional evidence that the carbohydrate binding activity of B. japonicum, most probably mediated by BJ38, may play an important role(s) in the initial phases of the infection process.
Accumulation of plastid HSP 23 of Chenopodium rubrum is controlled post‐translationally by light
Authors: Debel Karsten , Knack Gaby , Kloppstech Klaus
Published: March 2003

The expression of the 23 kDa plastid heat‐shock protein (HSP) of Chenopodium rubrum has been studied at various light intensities at a temperature of 38°C where the 23 kDa protein accumulates to its highest levels. It was observed that the level of mRNA which is induced at this heat‐shock temperature is independent of the light intensity between 0 and 1000 W m−2. Labelling in vivo of all investigated HSP is also not dependent on the light fluxes applied. In clear contrast the accumulation of the mature chloroplast HSP 23 is light dependent: while almost no protein is detectable in the dark the level of the accumulated protein reaches a maximum at a light intensity of 300 W m−2. The accumulated levels of HSP 23 correlate well with resistance against photoinhibition; photoinhibitory effects are observed at a light intensity of 300 W m−2 or above as measured by the decline of PS II activity.

When high light intensities are applied during recovery from heat shock the amounts of HSP 23 stay elevated for a longer time and at a higher level than at the standard light intensity of 10 W m−2. This appears to be a peculiar property of the plastid HSP 23 as the accumulation of HSP 17 and 70, as analysed by Western blot, is not influenced by light. When under particular stress conditions the levels of HSP 23 remain low a protein of 31 kDa accumulates that reacts with the antibody to HSP 23 and might represent the precursor of HSP 23.
A carboxy‐terminal plant vacuolar targeting signal is not recognized by yeast
Authors: Gal Susannah , Raikhel Natasha V.
Published: March 2003

Three different classes of signals for plant vacuolar targeting have been defined. Previous work has demonstrated that the carboxyl‐terminal propeptide (CTPP) of barley lectin (BL) is a vacuolar targeting signal in tobacco plants. When a mutant BL protein lacking the CTPP is expressed in tobacco, the protein is secreted. In an effort to determine the universality of this signal, the CTPP was tested for its ability to target proteins to the vacuole of Saccharomyces cerevisiae. Genes encoding fusion proteins between the yeast secreted protein invertase and BL domains were synthesized and transformed into an invertase deletion mutant of yeast. Invertase assays on intact and detergent‐solubilized cells demonstrated that invertase+CTPP was secreted, while nearly 90% of the invertase::BL+CTPP (fusion protein between invertase and BL containing the CTPP) and invertase::BL‐CTPP proteins (fusion between invertase and BL lacking the CTPP) were retained intracellularly. These fusions were secreted in a mutant of yeast that normally secretes proteins targeted to the vacuole. With this and previous work, proteins representing all three classes of plant vacuolar targeting signals have now been tested in yeast, and in all cases, the experiments indicate that the plant proteins are directed to the yeast vacuole using signals other than those recognized by plants.