Constraining paleo-latitude of a biogeographic boundary in mid-Panthalassa: Fusuline province shift on the Late Guadalupian (Permian) migrating seamount

The Guadalupian paleo-atoll limestone (Iwato Formation) in SW Japan was primarily formed in low-latitude mid-Panthalassa and was later tectonically accreted to South China (Japan) margin during the Jurassic. The present biostratigraphic study clarified that the Iwato Formation consists of 5 biostratigraphical intervals; i.e. four fusuline assemblage zones (Assemblage zones 1 to 4) and a barren interval on the top. Assemblage zones 1 to 4 correspond to the Neoschwagerina craticulifera Zone, N. margaritae Zone, Yabeina globosa Zone, and Lepidolina multiseptata Zone of the conventional Tethyan fusuline stratigraphy, respectively. The present study newly clarified the following significant aspects of paleobiogeography of the Permian fusulines as to the extinction of large-tested taxa in the latest Guadalupian. 1) The long unknown stratigraphic relationship was documented for the first time between the Yabeina-dominant interval and the overlying Lepidolina-dominant one within a single limestone unit. 2) The occurrence of Lepidolina cf. kumaensis Kanmera, the unique last runner of large-tested fusuine, was detected for the first time in mid-oceanic paleo-atoll limestones. 3) With respect to the northbound migration history of the paleo-seamount capped by the Iwato Formation, the development of the two coeval fusuline biogeographic territories in the low-latitude Panthalassa, i.e., the Yabeina territory on the south and the Lepidolina territory on the north, was confirmed. 4) The paleo-latitude of the biogeographic boundary between the Yabeina and Lepidolina territories is constrained around 12° in the southern hemisphere on the basis of the latest geomagnetic data from the same limestone. This new approach utilizing biostratigraphy on ancient migrating seamounts coupled with geomagnetic paleo-latitude data is applicable to other cases in different time-space co-ordinates and of other fossil groups for constraining position of ancient biogeographic boundaries within lost oceanic domains of deep past.     

Volatiles in the cometary nuclei

The argument for the similarity of the composition of cometary volatiles to that of interstellar molecules has been strengthened by the analysis of CO⁺ and CO ₂ ⁺ emission of the comet West. The strong 6300 Å emission of oxygen atoms can be interpreted in terms of photodissociation of OH by the solar Lyman-alpha radiation, and not as being due to photo-dissociation of CO₂ of speculatively large amount.     

The Hinode (Solar-B) Mission: An Overview

The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency’s Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy gets transferred from the photosphere to the upper atmosphere and results in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the X-Ray Telescope (XRT). This paper provides an overview of the mission, detailing the satellite, the scientific payload, and operations. It will conclude with discussions on how the international science community can participate in the analysis of the mission data. T. Kosugi deceased 26 November 2006.     

Interannual variability of subsurface temperature in summer induced by the Kuroshio over Bungo Channel,Tosa Bay,and Kii Channel,south of Japan

Using historical in situ temperature record, we investigate interannual variability of temperature in summer over Bungo Channel, Tosa Bay, and Kii Channel (hereafter “BTK”), south of Japan. This study aims to reveal the interregional relation of the subsurface temperature variability between the shelf and slope as well as between BTK, and specify the primary cause of the temperature variability in terms of the Kuroshio path. It is shown that 100-m temperature on the slope of BTK is synchronous with each other and highly correlated with coastal sea levels from Kyushu to Kii Peninsula, suggesting that subsurface temperature over the slope varies simultaneously on spatial scales of 400–500 km in the along-slope direction. The 100-m temperature on the slope is also correlated with the near-bottom temperature on the shelf, implying that the near-bottom temperature is determined mainly by the larger-scale variability over the slope. The Kuroshio state in summer of each year is classified into the large meander (LM), non-large meander (NLM), and intermittent larger meander (IM) propagating eastward along the slope. It is found that remarkable temperature increases are accompanied by the IM propagations south of BTK. Temperatures during the IM and LM period are significantly different, the means of which are the highest and lowest, respectively. Temperature during the NLM period with the second highest mean value exhibits the largest variance. Statistical analysis suggests that this variance is related to the Kuroshio axis shift over Izu Ridge between the nearshore and offshore NLM paths.     

Tracking flux melting and melt percolation in supra-subduction peridotites (Josephine ophiolite,USA)

Here, we investigate the scale and nature of melting and melt percolation processes recorded by 17 supra-subduction peridotites collected in a ~70 km² area in the northern portion of the Josephine ophiolite (Western USA). We present major and trace element variations in whole rocks; major elements in olivine, orthopyroxene, clinopyroxene and spinel; and trace elements [including rare earth element (REE)] in clinopyroxene and orthopyroxene. In the Josephine peridotites, compositional variability occurs at different scales. On the one hand, large systematic changes from depleted to fertile peridotites occur on large kilometer scales. Field, petrological and geochemical data can be consistently explained if the Josephine mantle experienced variable degrees of hydrous flux melting (10 to >20–23 %), and we argue that small fractions of subduction-derived fluids (0.015–0.1 wt%) were pervasive in the ~70 km² studied area, and continuously supplied during wedge melting. Fluid localization probably led to increased extent of flux melting in the harzburgitic areas. On the other hand, in single outcrops, sharp transitions from dunite to harzburgite to lherzolite and olivine websterite can be found on meter to centimeter scales. Thus, some fertile samples may reflect limited degrees of refertilization at the outcrop scale. In addition, clinopyroxene and orthopyroxene in ultra-depleted harzburgites (Spinel Cr# > 58) show variable degrees of LREE enrichment, which reflect percolation of and partial re-equilibration with, small fractions of boninite melt. Because the enriched samples also show the highest spinel Cr#, we argue that these enrichments are local features connected to the presence of dunite channels nearby. Lastly, trace element concentrations of pyroxenes in Josephine harzburgites show that they are one of the most depleted harzburgites among worldwide ophiolitic peridotites, indicating particularly high degrees of melting, potentially past the exhaustion of clinopyroxene.     

Correlations between oxygen-isotopic composition and petrologic setting in a coarse-grained Ca, Al-rich inclusion

Oxygen-isotopic compositions in conjunction with petrologic investigation have been determined for a coarse-grained type B2 Ca, Al-rich inclusion (CAI) from the reduced CV3 Vigarano using secondary ion mass spectrometry. The oxygen-isotopic compositions of minerals are distributed along the carbonaceous chondrite anhydrous mineral line indicating mixing between ¹⁶O-rich and ¹⁶O-poor nebular components. The O-isotopic heterogeneities among and within minerals in the CAI interior indicate that CAI formation started in an ¹⁶O-rich nebula and subsequently continued in an ¹⁶O-poor nebula. ¹⁶O-rich signatures of melilite and fassaite in the Wark-Lovering rim and of olivine of the accretionary rim indicate that the nebular environment during formation of the CAI returned to an ¹⁶O-rich composition after processing in an ¹⁶O-poor nebula. These O-isotopic variations in the CAI support multiple heating events in the solar nebula and indicate that the nebular environments fluctuated from ¹⁶O-rich to ¹⁶O-poor and back to ¹⁶O-rich compositions during the formation of a single CAI.     

Optical imaging of impact sites of Comet Shoemaker-Levy 9 at Bisei Astronomical Observatory

The impact sites of the Comet Shoemaker-Levy 9 are observed with the 101-cm telescope at Bisei Astronomical Observatory until the end of August with B, V, R, I, and methane-band (0.89m) filters. The outline of the observation is briefly described.     

Variation in noble gas isotopic composition of gas samples from the Aegean arc, Greece

In contrast to most other arcs with oceanic plate subduction, the Aegean arc is characterized by continent–continent subduction. Noble gas abundances and isotopic compositions of 45 gas samples have been determined from 6 volcanoes along the arc, 2 islands in the back-arc region and 7 sites in the surrounding areas. The ³He/⁴He ratios of the samples ranged from 0.027R_A to 6.2R_A (R_A denotes the atmospheric ³He/⁴He ratio of 1.4×10⁻⁶), demonstrating that even the maximum ³He/⁴He ratio in the region is significantly lower than the maximum ratios of most oceanic subduction systems, which are equal to the MORB value of 8±1 R_A. Regional variations in the ³He/⁴He ratio were observed both along and across the arc. The maximum ³He/⁴He ratio was obtained from Nisyros volcano located in the eastern end of the arc, and the ratio decreased westward possibly reflecting the difference in potential degree of crustal assimilation or the present magmatic activity in each volcano. Across the volcanic arc, the ³He/⁴He ratio decreased with an increasing distance from the arc front, reaching a low ratio of 0.063R_A in Macedonia, which suggested a major contribution of radiogenic helium derived from the continental crust. At Nisyros, a temporal increase in ³He/⁴He ratio due to ascending subsurface magma was observed after the seismic crisis of 1995–1998 and mantle neon was possibly detected. The maximum ³He/⁴He ratio (6.2R_A) in the Aegean region, which is significantly lower than the MORB value, is not probably due to crustal assimilation at shallow depth or addition of slab-derived helium to MORB-like mantle wedge, but inherent characteristics of the subcontinental lithospheric mantle (SCLM) beneath the Aegean arc.     

A 10-Year Study on Techniques for Vegetation Restoration in a Desertified Salt Lake Area

Vegetation restoration is one of the most common and effective ways to combat desertification and prevent adjacent areas from sand encroachment in many of the desertified regions of the world. However, vegetation restoration in desertified regions is very difficult because of low rainfall, the mobile ground surface, and cost. An effective, low-cost method of afforestation is urgently required. To determine such a method, a 10-year study was carried out in the Jilantai Salt Lake area. Five different afforestation areas were established: a ‘comparison area,’ a ‘land enclosure area,’ a ‘land enclosure + irrigation area,’ a ‘leveled-afforestation area’ (the dune areas were leveled and then planted with seedlings with added irrigation), and a ‘protected afforestation area’ (the dune areas were planted with seedlings, and the surviving natural vegetation was protected as much as possible). Vegetation-related parameters (survival rate, height, trunk diameter, coverage, canopy size, and density) and environment-related factors (relative humidity, wind velocity, and amount of sand encroachment) were measured by standard methods. Results show that the protected afforestation method had the following advantages: (1) the survival rate was higher for seedlings planted in the protected afforestation area than in the leveled afforestation area; (2) vigor (height, trunk diameter, coverage, and canopy size) was better in seedlings planted in the protected afforestation area than in the leveled afforestation area, especially in the beginning period of revegetation; (3) coverage (of individual species, of all planted vegetation, and of all vegetation) was larger in the protected afforestation area than in the leveled afforestation area; (4) density of naturally germinated plant species was higher in the protected afforestation area than in the other areas, showing that the protected afforestation method provided a suitable growing environment not only for planted species but also for naturally growing species; (5) in the protected vegetation area, relative humidity of air increased and wind velocity was greatly reduced; (6) after the establishment of vegetation by the protected afforestation method, sand encroachment into the salt lake area was significantly reduced. These results suggest that protected afforestation is an effective method of vegetation rehabilitation that has the potential not only to be applied to arid lands in China but also to desertified areas throughout the world; (7) cost-effective calculation shows that the leveled afforestation area costs much more than other areas.