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The rupture of continents and creation of new oceans is a fundamental yet primitively understood aspect of the plate tectonic cycle. Building upon past achievements by ocean drilling and geophysical and geologic studies, we propose “The Continental Breakup and Birth of Oceans Mission (COBBOOM)” as the next major phase of discovery, for which sampling by drilling will be essential.In September 2006, fifty-one scientists from six continents gathered in Pontresina, Switzerland to discuss current knowledge of continental breakup and sedimentary basin formation and how the Integrated Ocean Drilling Program (IODP) can deepen that knowledge Coffin et al., 2006). Workshop participants discussed a global array of rifted margins (Fig. 1), formulated the critical problems to beaddressed by future drilling and related investigations, and identified key rift systems poised for IODP investigations.

To show the structure of oceanic crust and Moho around the eastern Ogasawara Plateau, we have analyzed industry-standard two-dimensional multichannel seismic reflection data. To obtain improved velocity models, phase information of seismic signals was used for velocity analysis and velocity models for oceanic crust above Moho were determined. We apply this velocity analysis technique to seismic reflection data around the eastern Ogasawara Plateau, with the result of clear images of structures within oceanic crust and Moho. South of the Ogasawara Plateau, Moho deepens proximal to the Plateau. Moho distal to the Plateau is ca 7 km below sea floor (bsf), whereas it is ca 10 km bsf near the Plateau. The characters of oceanic crust and Moho differ significantly north and south of the Plateau. To the north, the structure of oceanic crust is ambiguous, the sea floor is shallower and less smooth, and Moho is discontinuous. To the south, structures within oceanic crust and Moho are imaged clearly, and the sea floor is deeper. A strong Moho reflection south of the Plateau might represent a sharp boundary between layered gabbro and peridotite. However, discontinuous Moho reflections north of the Plateau might represent rough topography because of intensive magmatism or a gradual downward increase in velocity within a thick Moho transition zone. A fracture zone north of the Plateau also appears to separate oceanic crust and Moho of different characters, suggesting vigorous magmatism between the Plateau and the fracture zone, and that the Ogasawara Plateau and the fracture zone influenced the genesis of oceanic crust and upper mantle. Differences in acoustic characteristics to the north and south of the Plateau are apparent in profiles illuminated by seismic attributes.

The application of the elliptic balance method to the solution of undamped, two degree of freedom homogeneous nonlinear systems is described. This method uses Jacobian elliptic functions in the balance and is based on the concept of averaging with respect to complete elliptic integrals of the first kind. To assess the accuracy of the approximate solution thus obtained, we consider the motion of a linear vibration absorber attached to a rigid body that is supported symmetrically by incompressible, homogeneous and isotropic hyperelastic shear blocks. It is shown that the amplitude–time response of the model system is well predicted by the elliptic balance method solution even for relatively large parameter values.

Dedicated to Professor Cornelius O. Horgan in esteem and friendship, with highest regard. Abstract: The response function for a general class of elastic molecular based materials characterized by their limiting molecular chain extensibility and depending on only the first principal in - variant of the Cauchy-Green deformation tensor together with a certain molecular based limiting extensibility parameter is introduced. The constitutive response function for the Gent material is then derived inversely as the (0/1) Pade approximant of this class, a re- sult that leads naturally to an infinite geometric series representation of its response func - tion. Truncation of this series function characterizes a familiar class of quadratic materials now having physically relevant material constants. It is shown that the (0/2) approximant of the response function for the general class of restricted elastic materials leads inversely to a new constitutive model and its series representation. Of course, many familiar limited elastic material models are members of the general class. The Pade approximants for some response functions are not, and empirical modifications that admit these as members of the general class are described. Examples of two limited elastic models in the class that are not Pade approximants are noted. The strain energy functions for a few of the restricted elastic models described are presented.

Oceanic Anoxic Events (OAEs) are geological time intervals characterized by extremely high burial rates of organic carbon that led to deposition of organic-rich “black shales” in the global ocean. It has been proposed that oceanic anoxic events are ultimately caused by massive volcanism associated with formation of large igneous provinces (LIPs) because of chronological similarities, but no general consensus has developed yet. To investigate the possibility of LIP volcanism instigating OAEs, we measured stable isotopic compositions of bulk organic carbon (δ13Corg) and lead (Pb) isotopic compositions in the silicate sediment fraction across the Bonarelli black shale (Italy), a type stratigraphic section for the end-Cenomanian OAE (OAE-2; 94 Ma). Ultra-high-resolution δ13Corg records determined every 1.5 mm capture a 3‰ sharp negative shift at the base of the Bonarelli. At the same stratigraphic level, Pb isotopic compositions in the silicate sediment fraction exhibit significant shifts toward characteristic values of volcanic rocks from contemporaneous LIPs (Caribbean and Madagascar flood basalts). These data suggest a rapid, substantial increase in the relative supply of silicate minerals from the two LIPs. Massive subaerial volcanism associated with LIP formation provides a simple explanation for these two isotopic geochemical signals via release of a huge amount of carbon dioxide (∼ 105 Gt CO2) and particulate materials into the atmosphere, which resulted in a rapid negative shift of δ13C in sea water and changes in Pb isotopic compositions in the silicate sediment fraction, respectively. We interpret that massive volcanism triggered significant climatic changes, inducing biotic crises and oceanic anoxia.

The finite amplitude, free radial oscillations of a thick-walled circular cylindrical tube are studied for an arbitrary incompressible, isotropic and homogeneous rubber-like material having limiting molecular chain extensibility. First, based on classical results for hyperelastic tubes, some results for thick-walled Mooney-Rivlin tubes are described graphically in the phase plane. Then the periodicity of the finite amplitude, free oscillations of a general limited elastic, thick-walled tube is studied; and some analytical results for the Gent model are illustrated in several numerical examples. Results for thick-walled Gent tubes are compared with those for corresponding Mooney-Rivlin tubes; and the motion of thin-walled Gent tubes is illustrated in the phase plane. Physical conclusions are presented. The period of small amplitude oscillations of an arbitrary elastic or limited elastic tube is derived from relations obtained by a linearization of a general class of equations of which the tube problem is a special case. Classical results of the linear theory are thereby recovered and compared with results for Mooney-Rivlin and Gent tubes.

The Manihiki Plateau in the western equatorial Pacific Ocean is a Cretaceous Large Igneous Province. Several studies have proposed that the Manihiki Plateau was formed by the same mantle plume that formed the Ontong Java and Hikurangi plateaus ca. 125 Ma. Recent multibeam bathymetric surveys of the Manihiki Plateau reveal the morphology of the Danger Islands Troughs (DIT), Suvarov Trough, which are systems of deep troughs within the plateau. The troughs divide the Manihiki Plateau into three distinct provinces, the North Plateau, the Western Plateaus, and the High Plateau. The DIT between the High Plateau and Western Plateaus comprises four en echelon troughs. With one exception, all segments of the DIT are bordered by steep escarpments, to 1500 m high. The basins of the DIT are smooth. Elongated northeast-southwest–striking scarps are common in the southernmost DIT and at the junction between the DIT and Suvarov Trough. The features revealed by the new bathymetric data indicate that a sinistral strike-slip tectonic environment formed the DIT during the break-up into the Manihiki and Hikurangi plateaus, whereas the Suvarov Trough developed after the formation of the DIT.

A rich mosaic of disparate crustal types characterizes the Earth beneath the sea. Although “normal” oceanic crust approximately 7-km thick is by far the most prevalent, abnormally thick oceanic-type crust of large igneous provinces (LIPs) also forms a signifi cant component of the marine realm (e.g., Coffi n and Eldholm, 1994; Mahoney and Coffin, 1997; Saunders, 2005). Scientific ocean drilling has significantly advanced understanding of LIPs. Herein we focus on significant outcomes of ten LIP-dedicated expeditions between 1985 and 2000 and also highlight prospects for future drilling efforts. The ten expeditions include three to the volcanic margins of the North Atlantic Tertiary Igneous Province, four to the Kerguelen Plateau/Broken Ridge LIP in the Indian Ocean, two to the Ontong Java Plateau in the western equatorial Pacifi c Ocean, and one to the Chagos-Maldive-Laccadive Ridge and Mascarene Plateau in the Indian Ocean (Table 1). Complementary geophysical and/or onshore geological investigations have added signifi cant value to all of these expeditions.

To better understand the effects of varying head movement frequencies on human balance control, 12 healthy adult humans were studied during static and dynamic (0.14, 0.33, 0.6 Hz) head tilts of +/- 30 degrees in the pitch and roll planes. Postural sway was measured during upright stance with eyes closed and altered somatosensory inputs provided by a computerized dynamic posturography (CDP) system. Subjects were able to maintain upright stance with static head tilts, although postural sway was increased during neck extension. Postural stability was decreased during dynamic head tilts, and the degree of destabilization varied directly with increasing frequency of head tilt. In the absence of vision and accurate foot support surface inputs, postural stability may be compromised during dynamic head tilts due to a decreased ability of the vestibular system to discern the orientation of gravity. This instability may compound the risk of falling following recovery from balance disorders or adaptation to altered gravity conditions such as space flight. Thus, dynamic head tilts may improve the diagnostic sensitivity of computerized dynamic posturography, particularly for healthy subjects recovering from temporary balance control deficits.

Constitutive equations for the back stress in amorphous glassy polymers based on extended forms of the non-Gaussian James—Guth 3-chain and Arruda—Boyce 8-chain models of rubber elasticity are derived from the extended Wu and van der Giessen non-Gaussian full-network model. A simple and invariant constitutive equation for the back stress tensor is then derived from the Wu and van der Giessen model by an average-stretch approximation. Although the average-stretch model of the full-network amorphous microstructure is more general than other chain cell models, the constitutive equation is the same as the 8-chain back stress relation. Back stress equations for a class of extended phenomenological models, including the Gent material model, are described.

We studied the effects of change of head position in the pitch plane on the ability to hold horizontal eccentric gaze in five patients with cerebellar disorders. All patient showed a change in the time constant of horizontal centripetal drift when the head was pitched forward or back. This result suggests that otolithic inputs can influence the neural integrator for horizontal eye movements and indicates the value of testing horizontal gaze holding in different head positions.

Systematic analysis of a grid of 3450 km of multichannel seismic reflection lines from the Solomon Islands constrains the late Tertiary sedimentary and tectonic history of the Solomon Island arc and its convergent interaction with the Cretaceous Ontong Java oceanic plateau (OJP). The OJP, the largest oceanic plateau on Earth, subducted beneath the northern edge of the Solomon arc in the late Neogene, but the timing and consequences of this obliquely convergent event and its role in the subduction polarity reversal process remain poorly constrained. The Central Solomon intra-arc basin (CSB), which developed in Oligocene to Recent time above the Solomon arc, provides a valuable record of the tectonic environment prior to and accompanying the OJP convergent event and the subsequent arc polarity reversal. Recognition of regionally extensive stratigraphic sequences—whose ages can be inferred from marine sedimentary sections exposed onland in the Solomon Islands—indicate four distinct tectonic phases affecting the Solomon Island arc. Phase 1: Late Oligocene–Late Miocene rifting of the northeast-facing Solomon Island arc produced basal, normal-fault-controlled, asymmetrical sequences of the CSB; the proto-North Solomon trench was probably much closer to the CSB and is inferred to coincide with the trace of the present-day Kia-Kaipito-Korigole (KKK) fault zone; this protracted period of intra-arc extension shows no evidence for interruption by an early Miocene period of convergent “soft docking” of the Ontong Java Plateau as proposed by previous workers. Phase 2: Late Miocene–Pliocene oblique convergence of the Ontong Java Plateau at the proto-North Solomon trench (KKK fault zone) and folding of the CSB and formation of the Malaita accretionary prism (MAP); the highly oblique and diachronous convergence between the Ontong Java plateau and the Solomon arc terminates intra-arc extension first in the southeast (Russell subbasin of the CSB) during the Late Miocene and later during the Pliocene in the northwest (Shortland subbasin of the CSB); folds in the CSB form by inversion of normal faults formed during Phase 1; Phinney et al. [Sequence stratigraphy, structural style, and age of deformation of the Malaita accretionary prism (Solomon arc-Ontong Java Plateau convergent zone)] show a coeval pattern of southeast to northwest younging in folding and faulting of the MAP. Phase 3: Late Pliocene–early Pleistocene arc polarity reversal and subduction initiation at the San Cristobal trench. Effects of this event in the CSB include the formation of a chain of volcanoes above the subducting Australia plate at the San Cristobal trench, the formation of the broad synclinal structure of the CSB with evidence for truncation at the uplifted flanks, and widespread occurrence of slides and “seismites” (deposits formed by seismic shaking). Phase 4: Pleistocene to Recent continued shortening and synclinal subsidence of the CSB. Continued Australia-Pacific oblique plate convergence has led to deepening of the submarine, elongate basin axis of the synclinal CSB and uplift of the dual chain of the islands on its flanks.

Possibilities for the fate of oceanic plateaus at subduction zones range from complete subduction of the plateau beneath the arc to complete plateau–arc accretion and resulting collisional orogenesis. Deep penetration, multi-channel seismic reflection (MCS) data from the northern flank of the Solomon Islands reveal the sequence stratigraphy, structural style, and age of deformation of an accretionary prism formed during late Neogene (5–0 Ma) convergence between the 33-km-thick crust of the Ontong Java oceanic plateau and the 15-km-thick Solomon island arc. Correlation of MCS data with the satellite-derived, free-air gravity field defines the tectonic boundaries and internal structure of the 800-km-long, 140-km-wide accretionary prism. We name this prism the “Malaita accretionary prism” or “MAP” after Malaita, the largest and best-studied island exposure of the accretionary prism in the Solomon Islands. MCS data, gravity data, and stratigraphic correlations to islands and ODP sites on the Ontong Java Plateau (OJP) reveal that the offshore MAP is composed of folded and thrust faulted sedimentary rocks and upper crystalline crust offscraped from the Solomon the subducting Ontong Java Plateau (Pacific plate) and transferred to the Solomon arc. With the exception of an upper, sequence of Quaternary? island-derived terrigenous sediments, the deformed stratigraphy of the MAP is identical to that of the incoming Ontong Java Plateau in the North Solomon trench.

The Integrated Ocean Drilling Program, an international collaboration of Earth, ocean, and life scientists, commenced on 1 October 2003 (IODP; www.iodp.org). Building on the successes of previous scientific ocean drilling programs, the IODP offers scientists worldwide unprecedented opportunities to address a vast array of scientific problems in all submarine settings.The scientific advisory structure of the proposal-driven IODP recently planned the inaugural drilling expeditions, targeting critical scientific problems in the eastern Pacific, central Arctic, and north Atlantic Oceans in 2004 and 2005 (Figure 1, Table 1). Co-led by Japan and the United States, with initial, significant contributions from the European Consortium for Ocean Research Drilling (ECORD),the IODP is guided by an initial science plan, “Earth, Oceans, and Life” (wwwiodp.org/isp.html), developed with broad input from the international geoscientific community. For the first time, scientists will have permanent riser and non-riser drilling vessels and mission-specific capabilities such as drilling barges, and jack-up rigs for shallow water and Arctic drilling at their disposal. Japan is providing the new riser vessel, Chikyu,i the IODP beginning in 2006; the United States is supplying the non-riser drilling vessel, currently ,JOIDES Resolution,, beginning in 2004; and the ECORD is furnishing mission-specific platforms, also beginning in 2004.

The ∼120 Ma Ontong Java Plateau and neighboring, contemporaneous Nauru, East Mariana, and (probably) Pigafetta basin flood basalts in the western equatorial Pacific Ocean comprise the Earth’s largest flood basalt province. Geophysical, geochemical, and geodynamic evidence from the province are difficult to reconcile with mantle plume models; absence of an obvious hotspot source or track, minor crustal uplift associated with emplacement, minor total subsidence compared with normal oceanic crust or other oceanic plateaus and submarine ridges, high degrees of melting at shallow, upper mantle depths, low water contents of basalts, enrichment of platinum group elements in basalts, and a ∼300 km deep, seismically slow mantle root are more consistent with the consequences of an impacting bolide. An object ∼20 km in diameter impacting relatively young (∼20 Myr) Pacific lithosphere and penetrating into the uppermost asthenosphere would have initiated massive decompression melting in the upper mantle, and may have resulted in emplacement of the greater Ontong Java Plateau.

A unit cube of compressible isotropic elastic material undergoes a homogeneous dilatation by dead loading forces applied to its faces. Conditions are obtained for stability of the resulting equilibrium state. The physical nature of these conditions is described and the results are illustrated for a compressible Blatz-Ko foamed rubber material.

The Mullins effect in the small amplitude transverse vibration of a stretched rubber membrane is investigated. The fundamental frequency, which decreases with increasing softening, is determined for a specific class of stress-softening materials. Analytical relations for the membrane vibration frequency are illustrated graphically for three phenomenological models and two kinds of non-Gaussian molecular network models for rubber elasticity. The results demonstrate the role of the material parameters and, although no experimental data for the vibration of a rubber membrane currently are known, the theoretical predictions are characteristic of the frequency-stretch response reported in vibration experiments on rubber cords.

The effect of stress-softening on the small amplitude transverse vibrational frequency of a stretched rubber membrane is investigated. The fundamental frequency is determined for a general incompressible and isotropic stress-softening material. It is shown that for each fixed value of the stretch λ ε (1,Λ), the fundamental frequency of the virgin material membrane is greater than the corresponding frequency of the same membrane preconditioned to a maximum previous stretch Λ. Moreover, the stress-softened membrane frequency for the same stretch decreases further with the degree of softening damage incurred upon increasing the maximum previous stretch. A specific damage function is introduced and explicit results are illustrated for three material models.

The Mullins effect in the small amplitude transverse vibration of a rubber cord is investigated. The fundamental frequency is determined for a specific class of stress-softening materials. Analytical relations for the cord vibration frequency are illustrated graphically for three phenomenological models. These results demonstrate the role of the material parameters and exhibit response characteristic of those reported in experiments by others and subsequently described here in new experiments. Frequency versus stretch results for two kinds of non-Gaussian molecular network models for rubber elasticity are compared with experimental data for four varieties of rubber cords, for each of which only three experimentally determined material constants are needed. It is shown that the theoretical predictions stand in excellent agreement with test data.

The equilibrium (EQ) score commonly used in computerized dynamic posturography is normalized between 0 and 100, with falls assigned a score of 0. The resulting mixed discrete-continuous distribution limits certain statistical analyses and treats all trials with falls equally. We propose a simple modification of the formula in which peak-to-peak sway data from trials with falls is scaled according the percent of the trial completed to derive a continuous equilibrium (cEQ) score. The cEQ scores for trials without falls remain unchanged from the original methodology. The cEQ factors in the time before a fall and results in a continuous variable retaining the central tendencies of the original EQ distribution. A random set of 5315 Sensory Organization Test trials were pooled that included 81 falls. A comparison of the original and cEQ distributions and their rank ordering demonstrated that trials with falls continue to constitute the lower range of scores with the cEQ methodology. The area under the receiver operating characteristic curve (0.997) demonstrates that the cEQ retained near-perfect discrimination between trials with and without falls. We conclude that the cEQ score provides the ability to discriminate between ballistic falls from falls that occur later in the trial. This approach of incorporating time and sway magnitude can be easily extended to enhance other balance tests that include fall data or incomplete trials.

Large igneous provinces (LIPs) represent huge volumes of erupted and intruded magma and are exceptional volcanic events in Earth history. They were erupted over a brief period of geologic time. The volume of magma emitted during each individual eruption that makes up an LIP (frequently 103 to perhaps 104 km3) is also exceptional, and these form Earth's largest eruptions. LIPs occur on continental crust (flood basalt provinces) and in ocean basins (oceanic plateaus), and at the transition between continents and oceans (“volcanic-”divergent margins). Basaltic LIPs usually form within a geologically brief period of time, especially the climax, or peak, of volcanic output, which may be less than 1 million years in duration. The eruptions that form flood basalt provinces have been proposed as a cause of major environmental perturbations throughout much of Earth history, including mass extinctions. Pāhoehoe-type lavas dominate in flood basalt provinces, and eruptions are thought to have durations of decades to perhaps centuries. The huge flow fields of pāhoehoe lavas are dominated by sheet lobes in many provinces, as well as alternations with flow fields dominated by smaller inflated lava lobes. Vents are poorly known, but some, at least, were long fissure-type systems.

New constitutive equations based on an amended form of the Kuhn–Grun probability distribution function due to Jernigan and Flory are derived from the standard James–Guth (JG) 3-chain and Arruda–Boyce (AB) 8-chain non-Gaussian molecular network models. The kinematics describing the stretch of a 1-chain model in an affine deformation shows that the relative stretch of a single molecular chain initially oriented along the diagonal of a cube is determined by the first principal invariant of the Cauchy–Green deformation tensor. The Kuhn–Grun probability distribution for a randomly oriented chain and its more general amended form due to Wang and Guth, are functions of only the relative chain stretch. Hence, any non-Gaussian network model for which the configurational entropy of all chains may be uniform is characterized by an elastic response function that depends on only the first principal invariant of the Cauchy–Green deformation tensor. Both the regular and amended AB 8-chain models are characterized by specific response functions in this class; the regular and amended JG 3-chain models, however, are not. An amended form of the phenomenological composite 3-chain/8-chain model suggested by Wu and van der Giessen is introduced. Analytical relations for several kinds of homogeneous deformations of the standard and amended models are compared with a variety of experimental data by others. It is found that results for the amended 3-chain and 8-chain models do not vary significantly from results for the corresponding regular models. The composite model, on the other hand, shows excellent overall agreement with the diverse data, including equibiaxial deformations for which other models show greater variance; but it offers no improvement in comparison with data for plane strain compression. Some remarks relating the chain parameters of the 3-chain and 8-chain network models, and the limiting chain and continuum stretches for these models are discussed in an appendix.

The motion of a homogeneous, thin rigid plate or shell subject to Stokes damping over its entire surface and to any additional system of workless forces, including those that are equipollent to zero, is studied. It is shown that the equation for the single-degree of freedom motion of every thin body having the same mass density per unit area is universal; the result, except for sufficient mathematical smoothness essential to integration over the body, is independent of any other physical features or dimensions of the body. A few examples illustrate the general problem and the universal nature of the equation of motion for thin plates and shells.

A new phenomenological model for stress-softening of isotropic, incompressible hyperelastic rubberlike materials is presented. For any specified virgin material constitutive equation, the stress-softened material response due to microstructural damage is characterized by an exponential softening function that depends on the current magnitude of strain and its maximum previous value in a deformation of the virgin material. The theory is illustrated for a neo-Hookean material; and it is shown that results derived for two non-Gaussian molecular network material models compare most favorably with uniaxial extension data provided by others.

The Kerguelen hotspot (Indian Ocean) has produced basalt for …130 Myr, among the longest known volcanic records from a single source. New and published 40Ar/39Ar age determinations from the Kerguelen Plateau, Broken Ridge, Rajmahal Traps, and Bunbury basalts, and of Indian and Antarctic dikes help to document the hotspot’s history. Using radiometric dates and crustal structure determined from geophysical data and drilling results, we calculate the magmatic output of the Kerguelen hotspot through time. Output rates have varied in ways not predicted by current geodynamic models; maximum eruption volumes postdate the initial surface manifestation of the hotspot as well as break-up between Antarctica and India by ∶15 Myr, and magma output rates were high, as well as geographically diverse, over an interval of 25 Myr, from …120 to …95 Ma. We propose two alternatives to the standard mantle plume paradigm, one involving multiple plume sources, and another consisting of a single, but dismembered plume source.

Large igneous provinces (LIPs) are constructed when Two objectives of ODP Leg 183 were to sample the copious amounts of mantle-derived magma enter the submarine LIP in as many locations as possible to: (1) Earth’s crust in localized regions. Although the Kerguelen determine the temporal variation in magma production; Plateau and Broken Ridge are now submarine, they (2) constrain the origin and evolution of the volcanic formed as a contiguous, largely subaerial LIP during rocks forming the LIP. Studies of igneous basement Cretaceous time in the eastern Indian Ocean. Subrecovered during Leg 183 complement continuing studies sequently, they were separated by sea-floor spreading of the Cenozoic subaerial lavas that form the Kerguelen beginning in Middle Eocene time along the Southeast Archipelago. This volume includes a collection of papers Indian Ridge (SEIR; Fig. 1). The Kerguelen Archipelago that address these objectives by using data for lavas is a Cenozoic feature constructed on the Northern Kerforming the Kerguelen Plateau, Broken Ridge and Kerguelen Plateau (NKP; Fig. 1). Together with the guelen Archipelago. >82–38 Ma hotspot track formed by the Ninetyeast High-quality radiometric age determinations are critRidge, the Kerguelen Plateau, Broken Ridge and Kerical for understanding rates of LIP formation, their causguelen Archipelago represent >119 Myr of volcanism ative dynamic mantle processes, and their temporal that has been attributed to the Kerguelen mantle plume. relationships to potentially related environmental Although the igneous basement of the Kerguelen Plateau changes. Duncan employs the Ar/Ar technique to had been sampled at Sites 738, 747, 749 and 750 (Fig. determine ages at all of the ODP Leg 183 igneous 1) by Ocean Drilling Program (ODP) Legs 119 and 120, basement drill sites (Fig. 1). In general, ages young Leg 183 was the first leg dedicated to understanding the northwards on the Kerguelen Plateau, from >119 Ma origin and evolution of an oceanic LIP. Five sites (1136, at Site 1136 in the south to >34 Ma at Site 1140 in the 1137, 1138, 1139, 1140) penetrated igneous basement north. Emplacement of the conjugate Central Kerguelen of the Kerguelen Plateau, and at two sites (1141, 1142) Plateau (CKP) and Broken Ridge falls within an >5 Myr the first basement samples were obtained from Broken Ridge (Fig. 1). window from >100 to >95 Ma. An unanticipated result

Two general universal relations for both compressible and incompressible, isotropic elastic materials reinforced by a single field of inextensible fibers are derived as components of an axial vector condition. The constitutive equations comprise a system of six scalar equations linear in four constraint and material response functions. It is known from the manifold method applied to this linear system that, in general, at least two universal relations exist. Hence, depending on the rank of a coefficient matrix, the two axial vector component equations comprise the complete set of universal relations for the fiber-reinforced material. These equations are valid for all deformations, and they hold independently of the balance equations and boundary conditions. The results are illustrated for a homogeneous simple shear with triaxial stretch of a material having various single fiber arrangements. For the homogeneous shear and two kinds of nonhomogeneous deformations, the balance equations and/or boundary conditions lead to an additional equation relating the constraint reaction and material response functions. Use of this condition together with the scalar constitutive equations has the effect of reducing the rank of the coefficient matrix, and hence additional universal relations are known to exist. Thus, besides the aforementioned pair of general universal relations, for the homogeneous shear and two specific nonhomogeneous deformations studied here, we deduce from the constitutive equations additional new universal relations.

Qualitative Behaviour Assessment (QBA) is a method that relies on the ability of human observers to integrate perceived details of behaviour, posture, and context into descriptions of an animal’s style of behaving, or ‘body language’, using descriptors such as ‘relaxed’, ‘tense’, ‘frustrated’ or ‘content’. Such terms have an expressive, emotional connotation, and provide information that is directly relevant to animal welfare and could be a useful addition to information obtained from quantitative indicators. Previous research with pigs, cattle, sheep and poultry consistently showed QBA to have high inter- and intra-observer reliability and to be coherent with quantitative behavioural and physiological measures, both when animals were assessed individually and at group level. Previous QBA work however was based on a Free-Choice-Profiling methodology that asks observers to develop their own descriptive terminologies, and is unsuitable for on-farm inspection. The aim of this study therefore was to design, and test the inter-observer reliability of, a fixed rating scale for QBA of cattle expression. This work was carried out with beef cattle, dairy cattle and veal calves. On the basis of previous QBA research with cattle and consultation with cattle experts, we designed a rating scale of 29 descriptors (32 for beef cattle). The rating scales were tested by three cohorts of four assessors, on 22 groups of veal calves and 22 groups of dairy cattle in Northern and Southern Italy, and on 21 groups of beef cattle in Southern Scotland. Assessors were given detailed instructions on the procedures of assessment and the use of the rating scale. The inter-observer reliability of the QBA scores attributed to the different cattle groups was tested using Kendall Correlation Coefficient W, and for beef cattle showed satisfactory reliability (W ≥ 0.70) for 20 out of 32 descriptors. For dairy cattle and calves this criterion was reached with only a few descriptors. However, comparison of Principal Component Analyses (PCA) of assessor scores within the three cattle groups showed remarkably similar emergent patterns of cattle expression, in which the first principal component (PC1) distinguished between positive and negative mood, and the second (PC2) differentiated these moods in low and high levels of arousal. These patterns were reproduced when descriptors with low loadings, low apparent welfare relevance, or with synonyms on the list, were removed from the assessor data sets (leaving 20 descriptors for each cattle group). For beef cattle, PC1 of the ‘reduced’ PCAs showed satisfactory inter-observer reliability (Kendall W=0.73; p

We use multichannel seismic data, gravity, and subsidence modeling, in conjunction with plate reconstructions, to evaluate the crustal origin and composition of the Kerguelen Plateau. Predominantly oceanic crust of the southern and parts of the central Kerguelen Plateau appears to include continental fragments related to the breakup of India and Antarctica; these fragments may have been metamorphosed during emplacement of the main plateau. The upper crust is basaltic, the middle crust is intrusive mafic rock and intruded continental crust, and the lower crust is a plagioclase-rich metamorphic rock. The Labuan Basin crust is predominantly oceanic with stranded Kerguelen Plateau fault blocks. High-density lower crust in the Labuan Basin is probably composed of serpentinized peridotites formed during slow rifting and spreading. Plate reconstruction models indicate opening between eastern Broken Ridge and southern Kerguelen Plateau at ∼90 Ma, heralding the formation of the Labuan Basin and Diamantina Zone; crustal attenuation and slow accretion of oceanic crust continued until the Australian and Antarctic plates separated at CI8 time (∼40 Ma). Plate reconstructions of the free-air gravity field indicate that the Naturaliste Plateau fits against Antarctica and that Elan Bank and India were juxtaposed until ∼110 Ma. Both Naturaliste Plateau and Elan Bank are probable microcontinents. A ∼1 km positive residual depth anomaly in the oceanic basins adjacent to the plateau, along with the positive geoid anomaly centered beneath the northern Kerguelen Plateau, imply that the lithosphere is partially dynamically supported by an upwelling hot asthenosphere of the Kerguelen hot spot.

The non-homogeneous deformation of combined torsion, extension and inflation of a stress-softening cylindrical tube is discussed within the framework of a theory of isotropic stress-softening in incompressible isotropic materials. The theory is based on the idea that the stress-softening material is an inelastic material that remembers only the maximum previous deformation to which it has been subjected. This selective memory dependence is incorporated within general material response functions that are monotone decreasing functions of a stress-softening variable; the latter is a monotone increasing function of the maximum previous strain experienced by the material. Results demonstrating the effects of stress-softening are obtained for general stress-softening materials in combined torsion, extension and inflation. A special analytical model is used to illustrate some general results as well as to provide graphical examples. By deforming a cylinder successively, first in simple torsion and then in uniaxial extension, the concept of deformation-induced inhomogeneity is presented. Finally, it is shown that the overall effects of stress-softening in pure torsion are much smaller than the corresponding effects in uniaxial extension.

Common experience teaches that the pressure required to inflate a balloon is noticeably reduced by prestretching it several times prior to its primary inflation. This preconditioning phenomenon is known as stress-softening and often is called the Mullins effect. A theory of stress-softening in incompressible isotropic materials is applied to study this effect in an equibiaxial extension for which some general results are presented. It is shown, for example, that effects of stress-softening in a simple uniaxial compression can be adduced from those demonstrated for equibiaxial extension under plane stress. The general equibiaxial results are applied to study the Mullins effect in the inflation of a spherical membrane. The stress-softening phenomenon in cyclic inflation and deflation of the balloon is investigated for Mooney-Rivlin and biotissue parent material models. It is shown analytically that the effect of preconditioning in uniaxial extension is to significantly reduce the pressure required to first inflate a balloon to an equivalent strain intensity. This result characterizes the familiar softening phenomenon associated with balloon inflation.

A general constitutive theory of stress-softening in isotropic, compressible materials based on a two phase microstructural damage model is presented. Stress-softening induced by an uniaxial stretch of the material is analyzed, and some general analytical results consonant with experimental observations are obtained. It is shown for compressible stress-softening materials that the Poisson function for the elastic stress-softened material generally will differ from that for the virgin material. Some general characteristics of the physical response of equi-Poisson materials are described, and an example of a general class of these materials is presented. It is shown that the physical response of isotropic, compressible stress-softening materials parallels that described in earlier papers on its incompressible counterpart. For illustration, a special subclass of stress-softening hyperelastic parent materials and an exponential softening function are introduced. The general results are then described graphically for uniaxial tension and compression of a special class of Blatz–Ko parent material models developed from experiments on polyurethane foamed rubbers.

In a series of papers by Hill and co-workers, a number of exact integrals are derived for plane strain, plane stress, and axially symmetric deformations of an isotropic, incompressible Varga elastic material. Here we show for more general plane strain deformations with transverse stretch that the angle ψ appearing in these integrals is, in fact, the local rigid-body rotation angle in the polar decomposition of the deformation gradient. The result is independent of any internal constraint and of the particular constitutive description of the material response for which the general first integrals were obtained. This physical identification of ψ will greatly assist in terms of exploiting these integrals for the subsequent solution of practical problems. It is also shown that the general integrals do not include a non-homogeneous, local simple shear deformation.

A general theory of isotropic stress-softening in incompressible isotropic materials is developed. The principal idea is that a stress-softening material is an inelastic material that has selective memory of only the maximum previous deformation to which it is subjected. This memory dependence is incorporated within general material response functions that are monotone decreasing functions of a stress-softening variable, which is a monotone increasing function of the maximum previous strain experienced by the material. A loading criterion is introduced to identify when the material is loaded along its virgin deformation path where the maximum previous strain is its current value, and to identify when it is unloaded to deform subsequently as an ideal isotropic elastic material in both elastic loading and unloading, so long as the maximum previous strain is not exceeded. The effect of loading from a configuration of maximum previous strain is to further stress-soften the material. Results demonstrating the effects of stress-softening are obtained for general isotropic stress-softening materials in simple uniaxial extension and in simple shear. A simplified analytical model together with a special softening function are introduced to illustrate some general results and to provide specific analytical and graphical examples. Both general and model-specific analytical results obtained for simple uniaxial extension are shown to be consistent with the overall ideal phenomenological behavior exhibited in experiments by others on stress-softening in simple tension and compression. Similar but totally new results for simple shear are derived, and their relation to effects in simple tension are discussed. It is demonstrated that the larger effect of softening occurs in the simple uniaxial extension, the effect in even a gross equivalent simple shear being small. All results are obtained from general three-dimensional constitutive equations.

New marine geophysical data along the Macquarie Ridge Complex, the Australia-Pacific plate boundary south of New Zealand, illuminate regional neotectonics. We identify tectonic spreading fabric and fracture zones and precisely locate the Australia-Pacific plate boundary along the Macquarie Ridge Complex. We interpret a ∼5–10 km wide Macquarie Fault Zone between the two plates along a bathymetrie high that extends nearly the entire length of the Australia-Pacific plate boundary south of New Zealand. We conclude that this is the active Australia-Pacific strike-slip plate boundary. Arcuate fracture zones become asymptotic as they approach the plate boundary. A broad zone of less intense deformation associated with the plate boundary extends ∼50 km on either side of the Macquarie Fault Zone. Marine geophysical data suggest that distinct segments of the plate boundary have experienced convergence and strike-slip deformation, although teleseismic evidence overwhelmingly indicates strike-slip motion along the entire surveyed boundary today. The McDougall and southernmost Puysegur segments show no evidence for past underthrusting, whereas data from the Macquarie and Hjort segments strongly suggest past convergence. The present-day strike-slip plate boundary along the Macquarie Ridge Complex coincides with the relict spreading center responsible for Australia-Pacific crust in the region. Our conceptual model for the transition from seafloor spreading to strike-slip motion along the Macquarie Ridge Complex addresses the decreasing length of spreading center segments and spacing between fracture zones, as well as the arcuate bend of the fracture zones that become asymptotic to the current transform plate boundary.

Postural instability (relative to pre-flight) has been observed in all shuttle astronauts studied upon return from orbital missions. Postural stability was more closely examined in four shuttle astronaut subjects before and after an 8 day orbital mission. Results of the pre- and post- flight postural stability studies were compared with a larger ( n = 34) study of astronauts returning from shuttle missions of similar duration. Results from both studies indicated that inadequate vestibular feedback was the most significant sensory deficit contributing to the postural instability observed post flight. For two of the four IML-1 astronauts, post-flight postural instability and rate of recovery toward their earth-normal performance matched the performance of the larger sample. However, post-flight postural control in one returning astronaut was substantially below mean performance. This individual, who was within normal limits with respect to postural control before the mission, indicated that recovery to pre-flight postural stability was also interrupted by a post-flight pitch plane rotation test. A similar, though less extreme departure from the mean recovery trajectory was present in another astronaut following the same post-flight rotation test. The pitch plane rotation stimuli included otolith stimuli in the form of both transient tangential and constant centripetal linear acceleration components. We inferred from these findings that adaptation on orbit and re-adaptation on earth involved a change in sensorimotor integration of vestibular signals most likely from the otolith organs.

The Ontong Java Plateau (OJP) is the largest and thickest oceanic plateau on Earth and one of the few oceanic plateaus actively converging on an island arc. We present velocity determinations and geologic interpretation of 2000 km of two-dimensional, multi-channel seismic data from the southwestern Ontong Java Plateau, North Solomon Trench, and northern Solomon Islands. We recognize three megasequences, ranging in age from early Cretaceous to Quaternary, on the basis of distinct interval velocities and seismic stratigraphic facies. Megasequence OJ1 is early Cretaceous, upper igneous crust of the OJP and correlates with basalt outcrops dated at 122–125 Ma on the island of Malaita. The top of the overlying megasequence OJ2, a late Cretaceous mudstone unit, had been identified by previous workers as the top of igneous basement. Seismic facies and correlation to distant Deep Sea Drilling Project/Ocean Drilling Program sites indicate that OJ2 was deposited in a moderately low-energy, marine environment near a fluctuating carbonate compensation depth that resulted in multiple periods of dissolution. OJ2 thins south of the Stewart Arch onto the Solomon Islands where it is correlated with the Kwaraae Mudstone Formation. Megasequence OJ3 is late Cretaceous through Quaternary pelagic cover which caps the Ontong Java Plateau; it thickens into the North Solomon Trench, and seismic facies suggest that OJ3 was deposited in a low-energy marine environment. We use seismic facies analysis, sediment thickness, structural observations, and quantitative plate reconstructions of the position of the OJP and Solomon Islands to propose a tectonic, magmatic, and sedimentary history of the southwestern Ontong Java Plateau. Prior to 125 Ma late Jurassic and early Cretaceous oceanic crust formed. From 125 to 122 Ma, the first mantle plume formed igneous crust (OJ1). Between 122 and 92 Ma, marine mudstone (OJ2 and Kwaraae mudstone of Malaita, Solomon Islands) was deposited on Ontong Java Plateau. At 92 Ma a second mantle plume caused widespread volcanism on the plateau. From 92 to 15 Ma, pelagic carbonate sediment (OJ3) was deposited. At ∼15 Ma the southern Ontong Java Plateau was deformed by normal faults during its approach toward the North Solomon Trench. Finally, from 4 to 0 Ma, the Malaita Accretionary Prism formed during collision between a substantially thicker portion of the Ontong Java Plateau and the Solomon Islands arc. Flexure of the Ontong Java Plateau near the trench caused coeval normal faulting.