The Upper Jurassic–Lower Cretaceous of eastern Heilongjiang, northeast China: stratigraphy and regional basin history

In eastern Heilongjiang, the Upper Jurassic is marine and restricted to the Suibin and Dong’an areas, where it is characterized faunally by Callovian–Volgian (Tithonian) bivalves and florally by dinoflagellates. The Lower Cretaceous is widely distributed in eastern Heilongjiang, and characterized faunally by Berriasian–Valanginian bivalves, Barremian–Albian ammonites and Aucellina, and florally by dinoflagellates. To the west, the marine facies grade into non-marine beds. Thus, in the east, for example in the Dong’an and Dajiashan areas, near the northwestern Palaeo-Pacific, the Lower Cretaceous is marine; westward, in the Yunshan, Longzhaogou, Peide, and Zhushan areas, marine and non-marine deposits alternate, whereas further west still, e.g. in the Jixi Basin, non-marine facies are intercalated with marine beds. This regional distribution is indicative of a large, shallow embayment opening eastwards to the Palaeo-Pacific; during the Early Cretaceous successive transgressive-regressive events influenced the climate and biota of eastern Heilongjiang and northeastern China. Many of the Lower Cretaceous sections contain abundant coals, demonstrating that in this region the Early Cretaceous was an important coal-forming period. Some non-marine bivalve species are common to the Lower Cretaceous Jixi Group of eastern Heilongjiang, the Jehol Group of western Liaoning and the Transbaikalian Group of Siberia, suggesting that these groups are of comparable Early Cretaceous age.     

The examination of fracturing process subjected to triaxial compression test in Inada granite

The behavior of a granite subject to a triaxial compression test ranging from the prefailure stage to the postfailure stage was studied using a fluorescent technique from the geological point of view. Microscopic observations of the specimens at different stages showed changes in the failure process. The start of formation of new microcracks paralleled the compression direction through their propagation until the onset of faulting and ended with the failure of shear zones after the strength failure point. Pores chiefly identified in the feldspar increased in length and width in the early stages, but not in number. It seems that the effect of pore spaces did not have any effect of failure. The microcracks generated on angular edges of quartz or feldspar grains and around biotite grains with increasing compression force. The phenomenon appearing on the crystal boundaries among biotite and quartz or feldspar agrees with the result calculated based on the theory on stress fields with ellipsoidal inhomogeneity suggested by Eshelby.     

Study of background aerosols in the Antarctic troposphere

Systematic year-round observations of submicron aerosols were carried out at Syowa Station (69°00'S, 39°35'E) in 1978. On the basis of the results of these observations, it is concluded that two types of aerosols originating from different sources are present in the Antarctic croposphere. With the intrusion of maritime air, mostly in the polar night months, sea salt particles and ammonium sulfate particles contained originally in the clean maritime air are dominant. The size distribution of such aerosols is monomodal, having a single mode at around 0.03 m in radii. On the other hand, in the sunlit months, sulfuric acid droplets are predominant and the size distribution is bimodal, having an additional mode at around 0.005 m in radii. Those sulfuric acid particles seem to be formed photochemically within a specific layer in the mid to lower troposphere over Antarctica. Most Antarctic submicron particles are of tropospheric origin, not of stratospheric nor anthropogenic origin.     

Oxygen- and strontium-isotopic investigations of subduction zone volcanism: the case of the Volcano Arc and the Marianas Island Arc

Recent, fresh, volcanic rocks of the intra-oceanic Mariana and Volcano Arcs were analyzed for O and Sr isotopic compositions in order to determine the source of these magmas. Fresh, non-arc, volcanic rocks from the regions surrounding the Mariana-Volcano Arcs and some DSDP sediments were also analyzed for comparison. The oxygen isotopic ratios of the arc lavas (5.5–6.8‰) exhibited a small inter-island variation that cannot be entirely explained by fractional crystallization. The Sr isotopic composition of the arc lavas is remarkably uniform (0.70332–0.70394 for the Marianas). Three models are considered in order to explain the observed isotopic characteristics: (1) bulk mixing and melting of MORB-type mantle with (a) subducted sediments, and (b) subducted oceanic crust (excluding sediments); (2) melting of a mixture of sediment-derived fluids and MORB-type mantle; and (3) melting of a mixture of sediment-derived fluids and oceanic island or “hot-spot” type mantle. The last model fits the data best. The conclusion that very small, and variable, amounts of sediment-derived fluid ( 1%) are required to explain the observed inter-island O isotopic variation, is consistent with that of other workers who used different isotopic and trace element methods. The generation of magmas in the Mariana-Volcano Arcs involves very little sediment and the source region of Mariana lavas is isotopically indistinguishable from that of hot-spot basalts.     

Petrological models of the oceanic lithosphere: Geophysical and geochemical tests

Petrological models of the oceanic lithosphere are tested to satisfy geophysical and geochemical constraints within the framework of plate tectonics. Quartz eclogite, olivine eclogite, peridotite and dunite are considered as the material of the lithosphere. The temperature at the base of the lithosphere is assumed to be the solidus temperature. This temperature, the thermal conductivity, and the heat flow and topography changes with age are used as the geophysical constraints. The compressional wave velocity-depth profile is used to select preferred models. Among geophysically successful models, high-temperature models are preferred to wet low-temperature models, because the low-temperature models have difficulties in explaining the mechanism of generation of oceanic basalt magmas. A preferred model is a two-layer model 70 km thick consisting of peridotite at the upper lithosphere and olivine eclogite at the lower lithosphere bounded at the base by the dry solidus.     

Towards a new view of earthquake phenomena

Recent advances in the theory of fracture and fragmentation are reviewed. Empirical laws in seismology are interpreted from a fractal perspective, and earthquakes are viewed as a self-organized critical phenomenon (SOC). Earthquakes occur as an energy dissipation process in the earth's crust to which the tectonic energy is continuously input. The crust self-organizes into the critical state and the temporal and spatial fractal structure emerges naturally. Power-law relations known in seismology are the expression of the critical state of the crust. An SOC model for earthquakes, which explains the Gutenberg-Richter relation, the Omori's formula of aftershocks and the fractal distribution of hypocenters, is presented. A new view of earthquake phenomena shares a common standpoint with other disciplines to study natural complex phenomena with a unified theory.     

Photographic monitoring system for observing heavy free-falling objects: Multi-stage design packages of radioactive waste

In the consideration of safety it is required that packages containing radioactive wastes when dumped at sea should keep their integrity and retain their contents until they reach the seabed. Packages containing simulated radioactive wastes (non-radioactive) were tested by a free-fall method at depthsca. 4,300 m in an area for dumping industrial waste off Shikoku Island. Since the weight of the largest package was 4,300 kg, special attention was paid to the connection of a buoyancy system with mooring rope. Descent and ascent velocities of the free-fall system were calculated prior to the experiment. A free-fall experiment with an extremely heavy object, heavier than ever previously reported, was accomplished without trouble by using the free-fall system. Recovery of a camera, flash-light, and other components was successful in each of the three experiments. Successive photographing of the package during descent was made and its integrity was observed using the photographs taken by the recovered camera. The packages remained intact during descent and at least for a short time after arrival on the seabed.     

Formation rate of water masses in the Japan sea

Water masses in the subsurface and the intermediate layer are actively formed due to strong winter convection in the Japan Sea. It is probable that some fraction of pollution is carried into the layer below the sea surface together with these water masses, so it is important to estimate the formation rate and turnover time of water masses to study the fate of pollutants. The present study estimates the annual formation rate and the turnover time of water masses using a three-dimensional ocean circulation model and a particle chasing method. The total annual formation rate of water masses below the sea surface amounted to about 3.53 ± 0.55 Sv in the Japan Sea. Regarding representative intermediate water masses, the annual formation rate of the Upper portion of the Japan Sea Proper Water (UJSPW) and the Japan Sea Intermediate Water (JSIW) were estimated to be about 0.38 ± 0.11 and 1.43 ± 0.16 Sv, respectively, although there was little evidence of the formation of deeper water masses below a depth of about 1500 m in a numerical experiment. An estimate of turnover time shows that the UJSPW and the JSIW circulate in the intermediate layer of the Japan Sea with timescales of about 22.1 and 2.2 years, respectively.     

Isotopic evolution and climate paleorecords: modeling boundary effects in groundwater-dominated lakes

We used an isotopic mass-balance model to examine how the hydrogeologic setting of lakes influences isotopic response of evaporating lake water to idealized hydroclimatic changes. The model uses a monthly water and isotope balance approach with simplified water-column structure and groundwater exchanges. The framework for comparative simulations is provided by lakes in a region of the Northern Rocky Mountains that display high interlake geochemical variability, thought to be controlled by groundwater hydraulics. Our analysis highlights several isotopic effects of flow between aquifers and lakes, leading to possible divergence of isotopic paleorecords formed under a common climate. Amplitude of isotopic variation resulting from simulated climate forcing was greatly damped when high groundwater fluxes and/or low lake volume resulted in low lake fluid residence time. Differing precipitation and evaporation scenarios that are equivalent in annual fluid balance (P−E) resulted in different isotopic signatures, interpreted as a result of evaporation kinetics. Concentrating low-δ groundwater inflow during spring months raised springtime lake δ values, a counterintuitive result of coincidence between times of high groundwater inflow and the evaporation season. Transient effects of reduced fluid balance caused excursions opposite in sign from eventual steady-state isotopic shifts resulting from enhanced groundwater inflow dominance. Lags in response between climate forcing and isotopic signals were shortened by high groundwater fluxes and resulting short lake residence times. Groundwater-lake exchange exerts control over patterns of lake isotopic response to evaporation through effects on lake residence time, inflow composition, and seasonal timing of inflow and outflow. Sediments from groundwater-linked lakes, often used for paleoenvironmental analysis, should be expected to reflect isotopic complexities of the type shown here. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.