Direct correlation of radiolarian <Emphasis Type="Italic">Kilinora spiralis</Emphasis> Zone with the Late Jurassic ammonite faunal succession in the Kurisaka Formation,Kurosegawa Terrane,SW Japan

The last appearance datum of the radiolarian Kilinora spiralis is recorded above the first appearance datum of the ammonite Ataxioceras (A.) kurisakense in the Todoro Section of the Kurisaka Formation, Southern Kurosegawa Terrane, Shikoku, SW Japan. The constraint by ammonite age prolongs the range of the Kilinora spiralis Zone, a remarkable Jurassic radiolarian zone in Japan-NW Pacific region, into the lower Kimmeridgian. The direct correlation of the Kilinora spiralis zone with the Late Jurassic ammonite faunal succession in the Kurisaka Formation will provide a clue to the still pending chronological difference between European and North American radiolarian zones.     

Magnetostratigraphy across the Berriasian-Valanginian stage boundary (Early Cretaceous), at Cehegin (Murcia Province, southern Spain)

The Berriasian-Valanginian stage boundary near the town of Cehegin in the eastern Subbetic Cordillera of Spain is documented by a detailed ammonite zonation in pelagic limestones. Two magnetostratigraphic sections spanning the uppermost ammonite subzone of the Berriasian and the lower two zones of the Valanginian yielded identical magnetic polarity patterns. Remanent magnetization is predominantly carried by magnetite, and characteristic directions were obtained by thermal demagnetization. The mean characteristic directions from both sites have an inclination of 48°; however, the site declinations are divergent (030° and 074°) due to the tectonic disturbance of the region. The Cehegin polarity pattern can be correlated by means of ammonite and calpionellid zonation to the magnetostratigraphies of the Berriasian stratotype and several Italian sections, thereby enabling a unique correlation to the M-sequence magnetic polarity time scale. The Berriasian-Valanginian stage boundary is in the middle of normal-polarity chron M15n.     

Jurassic magnetostratigraphy, 3. Bathonian-Bajocian of Carcabuey, Sierra Harana and Campillo de Arenas (Subbetic Cordillera, southern Spain)

Four sections in Majocian-Bathonian (Middle Jurassic) pelagic limestone with standard ammonite zonation have yielded magnetic polarity sequences. Magnetic directions in these red to white limestones were obtained by thermal demagnetization and were stable from about 300°C to in excess of 450°C. The polarity patterns indicate that the majority of the Bajocian and Bathonian is characterized by quite frequent reversals of the magnetic field. Lengthy periods of constant polarity, particularly constant normal polarity, were not observed. The average frequency of reversals is about 6 per ammonite zone, which roughly may be interpreted as a frequency of a reversal every 260,000 years, a rate comparable to that of the Miocene-Pliocene. Paleolatitudes of these sites (25–28°) are about 10° south of their present positions; variable clockwise block rotations within the Subbectic region have rotated these sites relative to stable Iberia.     

Magnetostratigraphic correlation of the Oxfordian–Kimmeridgian boundary

A magnetic polarity pattern for Boreal and Sub-Boreal ammonite zones of the Upper Oxfordian to Lower Kimmeridgian was established and confirmed in four British sections, including the proposed Global Boundary Stratotype Section and Point (GSSP) on the Isle of Skye (Scotland) to define the base of the international Kimmeridgian Stage. A coeval pattern for Sub-Mediterranean ammonite zones was compiled from seven sections in Poland, one German section and multi-section composites from France and Spain. The mean paleopole for the European Craton (excluding Spain) at the Oxfordian–Kimmeridgian boundary is 74.2°N, 181.3°E (Α₉₅ = 3.8°). The common magnetic polarity scale enables inter-correlation of ammonite subzones among these three faunal provinces and to the marine magnetic-anomaly M-Sequence. The proposed GSSP at the base of the Pictonia baylei Zone is near the base of an extended interval dominated by reversed polarity, which is interpreted to be Chron M26r. This GSSP level projects to the lower to middle part of the Epipeltoceras bimammatum Subzone, which is the middle subzone of this E. bimammatum Zone in the Sub-Mediterranean standard zonation. In contrast, the traditional placement of the Oxfordian–Kimmeridgian boundary in that Sub-Mediterranean standard zonation (base of Sutneria platynota Zone) is at the base of Chron M25r, or nearly 1 million years younger.     

Magnetostratigraphy of the Toarcian stratotype sections at Thouars and Airvault (Deux-Sèvres, France)

Magnetostratigraphic study of the Toarcian type sections of Thouars and Airvault (Deux-Sèvres, France) has yielded two reliable magnetic polarity sequences. Most samples were treated by mixed cleaning: thermal demagnetization (250°, 300° or 350°C) and subsequent alternating field demagnetization. Polarity intervals are easily identified and correlate well between the two sections using the biostratigraphic data provided by the detailed standard ammonite zonation of the Toarcian stage. The polarity sequence extends from ammonite horizon V (Pseudoserpentinum horizon,Serpentinus zone) to horizon XXV (Subcompta horizon,Aalensis zone); it shows 5 reversed and 5 normal polarity magnetozones.     

Oxfordian magnetostratigraphy of Poland and its correlation to Sub-Mediterranean ammonite zones and marine magnetic anomalies

A nearly continuous magnetostratigraphic polarity pattern was compiled from several ammonite-zoned carbonate successions of southern Poland and from a composite magnetostratigraphy from the Iberian Range of Spain. The array of sections spans the middle two-thirds of the Oxfordian within the Sub-Mediterranean Province (Cordatum through Bifurcatus ammonite zones). The average paleopole calculated from eight of these Polish sections is at 78.5°N, 184.9°E (δp = 2.6°, δm = 3.5°). The Sub-Mediterranean polarity pattern is consistent with an independent polarity pattern derived from the Boreal-realm sections of the British Isles, and improves the inter-correlation between these faunal realms. Cycle stratigraphy published for these ammonite subzones from southern France enabled temporal scaling of the polarity pattern, thereby facilitating correlation to marine magnetic anomalies M28 through M33 as modeled from deep-tow magnetometer surveys in the Western Pacific. The bases of the Middle and Upper Oxfordian substages as defined in the Sub-Mediterranean zonation in Poland correspond approximately to chrons M33 and M29 of that Pacific M-sequence model.     

Discovery of agglutinated foraminifers from the Longzhaogou Group in eastern Heilongjiang Province

The low diversity agglutinated foraminifers are recovered from the Qihulin Formation of the Longzhaogou Group in eastern Heilongjiang, China. The foraminiferal fauna consists of 9 species of 5 genera. The common members are Cribrostomoides nonioninoides (Reuss), Haplophragmoides concavus (Chapman), H. gigas minor Nauss. Although the diagnostic zonal taxa are absent in the agglutinated fauna, according to the global stratigraphic distribution of the above-mentioned species, and the associated Pseudohaploceras ammonite fauna, the foraminiferal fauna may be of a Barremian-Aptian (Early Cretaceous) age.     

Oxfordian magnetostratigraphy of Britain and its correlation to Tethyan regions and Pacific marine magnetic anomalies

A suite of 11 sections through the Oxfordian (Upper Jurassic) strata in the Dorset and Yorkshire regions of England and the Isle of Skye in Scotland yielded magnetic polarity patterns directly calibrated to the ammonite biostratigraphy of the Boreal and the Subboreal faunal provinces. The sections include the leading candidate for the global stratotype (GSSP) for the Callovian–Oxfordian stage boundary. The mean Oxfordian paleomagnetic pole derived from the Dorset and Yorkshire sections is 71.3°N, 172.6°E (δp = 4.2°, δm = 6.1°). The integrated magneto-biostratigraphic scale is consistent with results from the Sub-Mediterranean faunal province and extends the polarity pattern to the base of the Oxfordian. After adjusting for the estimated durations of ammonite subzones from cycle stratigraphy, the magnetostratigraphy confirms models for marine magnetic anomalies M30 through to M37, including some of the short-duration features recorded by deep-tow magnetic surveys in the western Pacific. The Callovian–Oxfordian boundary (base of Quenstedtoceras mariae Zone) occurs in a normal-polarity zone that is correlated to the youngest part of polarity chron M37n of this extension to the M-sequence.     

The Upper Valanginian (Early Cretaceous) positive carbon-isotope event recorded in terrestrial plants

Our understanding of the ancient ocean-atmosphere system has focused on oceanic proxies. However, the study of terrestrial proxies is equally necessary to constrain our understanding of ancient climates and linkages between the terrestrial and oceanic carbon reservoirs. We have analyzed carbon-isotope ratios from fossil plant material through the Valanginian and Lower Hauterivian from a shallow-marine, ammonite-constrained succession in the Crimean Peninsula of the southern Ukraine in order to determine if the Upper Valanginian positive carbon-isotope excursion is expressed in the atmosphere. δ¹³C_plant values fluctuate around − 23‰ to − 22‰ for the Valanginian-Hauterivian, except during the Upper Valanginian where δ¹³C_plant values record a positive excursion to ∼− 18‰. Based upon ammonite biostratigraphy from Crimea, and in conjunction with a composite Tethyan marine δ¹³C_carb curve, several conclusions can be drawn: (1) the δ¹³C_plant record indicates that the atmospheric carbon reservoir was affected; (2) the defined ammonite correlations between Europe and Crimea are synchronous; and (3) a change in photosynthetic carbon-isotope fractionation, caused by a decrease in atmospheric pCO₂, occurred during the Upper Valanginian positive δ¹³C excursion. Our new data, combined with other paleoenvironmental and paleoclimatic information, indicate that the Upper Valanginian was a cool period (icehouse) and highlights that the Cretaceous period was interrupted by periods of cooling and was not an equable climate as previously thought.     

A Comparison of Growth Biomarkers for Assessing Sublethal Effects of Cadmium on a Marine Gastropod, Nassarius festivus

The effect of cadmium on the growth of an intertidal marine gastropod, Nassarius festivus, was investigated using a number of biomarkers namely conventional measurements in terms of increase in shell length or body weight, scope for growth (SfG) and RNA/DNA ratio. After eight days of cadmium exposure, the no observable effect concentration (NOEC) and lowest observable effect concentration (LOEC) for the rate of increase in wet weight were 1.00 and 1.38 mg/l, respectively, while those for shell length did not show any significant difference from the control until day 16. After 16 days of cadmium exposure, the LOEC for both shell length and wet weight measurements was 0.22 mg/l. The 8-day SfG test was sensitive to cadmium stress, showing a significant decrease at 0.16 mg/l cadmium when compared to the control. The NOEC and LOEC of RNA/DNA ratio determination were 0.52 and 0.93 mg/l, respectively. An assessment based on sensitivity and technical complexity suggests that Scope for Growth is the most sensitive growth biomarker, followed by the RNA/DNA ratio, and then the conventional growth measurement based on shell size and body weight.     

Integrated Upper Carnian to Lower Norian biochronology and implications for the Upper Triassic magnetic polarity time scale

We summarize the ammonoid, conodont and halobiid biochronology of the Upper Carnian to Lower Norian, based on a discussion of data in the Alps, Sicily, Balkans, Turkey, Himalayas and Timor. With this integrated biostratigraphic scale, the Pizzo Mondello section (Sicily) can be recalibrated and the Carnian-Norian boundary more precisely located there. As a result, the magnetostratigraphy of this section is now in good agreement with previous results from Turkey, although the latter series are more condensed. Cross-correlation of available magnetostratigraphic data from marine Tethyan sections allow us to construct a composite Upper Carnian to Upper Norian geomagnetic polarity time scale (GPTS). This GPTS leads us to question previously proposed magnetobiostratigraphic and chronostratigraphic correlations within the Upper Triassic Newark non-marine sedimentary sequence.     

跨断层隔震管道管端与土体相互作用分析

断层错动是造成埋地管道破坏的重要因素之一,因此,跨断层埋地管道在断层错动下的破坏机制、模型设计与参数分析和管道抗断层措施一直是生命线工程的前沿问题。对跨断层管道内力分析取得的成果较多,比较经典的是Newm ark-Hall方法、Kennedy方法和王汝梁方法,后来又出现基于壳模型的有限元分析方法。现有的管道抗断层措施具有其优点的同时亦有其不足。本文基于壳模型的有限元动力数值模拟,对一种管道跨断层隔震措施进一步研究,考虑管端与土体相互作用计算隔震管段的断层错动响应。计算结果表明拉应变容易在土中的管段传递,相比较而言,压应变不容易在土中的管段传递;最大拉应变降低比较多,最大压应变降低比较少。根据分析结果,对跨断层隔震管段边界条件的选取提出建议。     

Ion drift in the earth’s inner plasmasphere during magnetospheric disturbances and proton temperature dynamics

Based on the thermal plasma measurements in the Earth’s inner plasmasphere on the INTER-BALL-2 and MAGION-5 satellites it has been indicated that the plasmaspheric ion temperature as a rule decreases during the main phase of magnetic storms; in this case the plasma density increases or remains at the level typical of undisturbed conditions. The physical mechanism by which the ion drift during a magnetic storm results in a temperature decrease is described. It is shown that the third adiabatic invariant also remains in processes with a characteristic time shorter than the period of charged particle drift around the Earth for cold equatorial plasma. The constructed model of the drift shell displacement from the Earth caused by a decrease in the magnetic field in the inner magnetosphere during the development of a magnetic storm satisfactorily describes the decrease in the proton temperature near the equatorial plane.     

Evolution of Heterogeneous Mixed Siliciclastic/Carbonate Aquifers Containing Metastable Sediments

Mixed carbonate and siliciclastic marine sediments commonly become freshwater aquifers in eastern coastal regions of the United States and many other global locations. As these deposits age, the carbonate fraction of the sediment is commonly removed by dissolution and the aquifer can become a solely siliciclastic system or contain zones or beds of pure quartz sand. During aquifer evolution, the sediment grain size characteristics, hydraulic conductivity, and porosity change. An investigation of these changes using mixed carbonate/siliciclastic sediment samples collected from a modern barrier island beach in southern Florida showed that the average mean grain diameter decreased with removal of the carbonate fraction, but the average hydraulic conductivity and porosity increased slightly, but not to statistical significance. This counterintuitive result occurs because of the change in the pore types from a combined shelter and intergranular pore system producing a dual porosity system in the mixed sediments to a single intergranular pore system in the siliciclastic sediment fraction. Within the mixed carbonate/siliciclastic sediment, in the pure carbonate fraction, large shell fractions form grain‐supported large pores, which become filled with sand‐sized quartz as the shell fragments decrease in size or as the sediment becomes compacted. The hydraulic conductivity increases because the shell fragments that were oriented perpendicular to flow caused an increase in the length of the flow path, or a larger scale tortuosity, compared with the flow through pure quartz sand.     

Ammonite- and bivalve-based biostratigraphy and Panboreal correlation of the Volgian Stage

The current ammonite- and buchiid-based biostratigraphical successions of the Volgian Stage are outlined, with an analysis of the most important data that support correlation throughout the Panboreal Superrealm. Updated ammonite zonal schemes were proposed for the Volgian of the type region (the Russian Platform) and Svalbard. The lower Volgian successions in all areas except the Russian Platform, with its eudemic virgatitid lineage and Submediterranean faunal elements, were dominated by Pectinatites and Eosphinctoceras-Subdichotomoceras. The last two genera were especially common eastwards from the Ural Mountains. During the middle Volgian, provincialism developed quickly within the ammonites, and unified assemblages with early Palvovia and Dorsoplanites at the base of the substage were replaced by numerous local eudemic faunas. Despite this, migrations of species of Crendonites, Laugeites, Epivirgatites Epipallasiceras, Epilaugeites, and Taimyrosphinctes occurred at regular intervals and these enable precise correlations between the faunal sub-provinces. The zonation of the upper Volgian is mainly based upon the succession of Craspedites (on Subcraspedites in England and North Sea), and can be traced throughout the Arctic. Zonation based on the bivalve Buchia enables correlations to be made between the successions over much of the Northern Hemisphere, including Northern California, British Columbia, Arctic areas, and the Russian Platform. Each substage of the Volgian is characterized by buchiids with different types of the ontogenetic development. Research on the infrazonal subdivision of the Volgian Stage based on buchiids is currently in progress. Our analyses of the ammonite and buchiid successions of the Panboreal Superrealm lead us to conclude that there are no major faunal gaps in Volgian successions of the Russian Platform and Northern Siberia.     

Cd concentration in the soft tissue vs. the nacreous layer of Mytilus californianus

The soft tissue of Mytilus californianus has the capacity to decrease its Cd concentration in the order of days. However, for medium-term (months) pollution surveys it is necessary to find alternative structures capable of integrating Cd concentrations during longer periods of time. The recently deposited nacreous layer of the shell of M. californianus is proposed as such a structure. Daily variability of Cd concentration in the soft tissue and in the recently deposited nacreous layer of a natural population of mussels was compared during a period of 26 days in organisms collected from an upwelling zone of British Columbia. Statistical analysis of the Cd concentrations indicated that the nacreous layer presented less significant differences between days than the associated soft tissue. Only one shell sample showed significant differences in Cd concentrations, probably related to environmental conditions and stress arising from mussel population density. Experimental results carried out in the laboratory confirmed that the recently deposited nacreous layer of M. californianus is a better medium-term indicator of Cd in seawater, especially at low concentration exposures of this element, those similar to the ones encountered in natural environments.     

穿越克孜尔逆冲断层的输气管道抗震分析

输气管道作为1种薄壁壳体结构,逆冲断层引起的管道压缩变形容易使其破坏。本文以大北南疆输气管道工程为例,探讨了穿越克孜尔逆冲断层的输气管道地震安全问题。在确定管道穿越处的断层倾角、设防断层位错量、表征管土相互作用的土弹簧参数以及钢管容许应变等参数后,采用壳有限元方法,分析了穿越克孜尔逆冲断层的输气管道变形反应。分析结果显示,管道在逆冲断层作用下以压缩应变为主,管道内的最大轴向压缩应变的幅值随着交角的减小而减小。在通过探槽等方法确定断层活动位置后,该管道若以小于或等于11°的交角通过克孜尔断裂,断层引起的最大轴向压缩应变和拉伸应变均在管道相应的容许应变范围内,满足相关规范的抗震要求。     

多点冲击荷载作用下K6型单层球面网壳结构失效机理分析

为研究单层球面网壳结构在多点冲击荷载作用下的失效机理,在ANSYS/LS-DYNA中建立了60m跨度的Kiewitt 6型单层球面网壳结构的有限元模型,将整个网壳结构沿肋杆分成6个不同扇区,沿环杆分成5个不同环区,分别对网壳结构在同一环区和同一扇区受到多点冲击时的动力响应及冲击全过程能量传递的规律进行了分析研究。基于网壳结构失效变形特点,定义了多点冲击荷载作用下单层球面网壳结构的4类失效模式;根据整个冲击过程中能量的传递特点,揭示了单层球面网壳结构每类失效模式所对应的失效机理。     

Turam response of a permeable inhomogeneous cylindrical conductor surrounded by a thin shell

Summary Electromagnetic response characteristics of an inhomogeneous permeable cylinder surrounded by a thin insulated concentric dissipative shell is obtained in presence of a line-source of current. The 3-layer boundary value problem is solved by assuming the thickness of the shell to be much smaller than the skin-depth in the shell. Numerically computed results are presented in the form of argand diagrams to examine the influence of the shell parameters (conductivity and its proximity with the core) and magnetic contrast. The multi-frequency response of the system is also given which resolves the two conducting layers and analyzes the frequency dependence of screening behavior of the shell.N.G.R.I. Contribution No. 282.     

Seismic response of a cylindrical shell embedded in a layered viscoelastic half-space. I: Formulation

A method to obtain the three-dimensional harmonic response of a infinitely long cylindrical shell of circular cross-section embedded in a layered viscoelastic half-space and subjected to harmonic plane waves impinging at an oblique angle with respect to the axis of the shell is presented. The procedure combines an indirect integral representation for the field in the exterior half-space with a model of the pipeline or tunnel based on Donnell shell theory. The integral representation for the soil is based on the use of moving Green's functions for the layered viscoelastic half-space. The accuracy of the formulation is tested by comparison of results obtained by using different discretizations. Extensive comparisons with previous two- and three-dimensional results for the case of a shell embedded in a uniform half-space and some new numerical results for a shell embedded in a multilayered half-space are presented in a companion paper.