A new historical review is presented on the progress of the geological sciences in Japan since the Meiji revolution in 1868. Geological knowledge, particularly studies of the geotectonic evolution and orogenic aspects, of the Japanese Islands has progressed through three distinct phases; (1) non-science stage, (2) colonial science stage, and (3) independent science stage, as modeled by Basalla (1967), who demonstrated a general pattern of transplanting cutting-edge scientific / technological knowledge from western Europe to the rest of the world. During the "non-science" stage from the 1860s to the 1890s, major geological aspects of the Japanese Islands, together with discoveries of unusual rocks, fossils etc., were initially described by foreign geologists (e.g. E. Naumann). In contrast, almost nothing was contributed by domestic geologists. During the "colonial science" stage, from the 1900s to the 1980s, research and education systems were transplanted effectively from western European countries. For example, applying the purely imported concept of geosyncline, the geotectonic history of the Japanese Islands was summarized for the first time by domestic geologists (e.g., Kobayashi, 1941; Minato et al., 1965 etc.). The almost unidirectional acceptance of plate tectonics also followed at this stage, with the exception of the rare but outstanding contribution of A. Miyashiro during the 1960s-1970s. During the "independent science" stage from the 1980s, various new ideas and original techniques in geology were proposed by Japanese geologists with lesser help from the western countries than before; i.e., practical criteria for identifying ancient accretionary complex, exhumation tectonic of ultrahigh to high-P/T metamorphic rocks, and subhorizontal growth framework of subduction-related orogens. Furthermore, in the first decade of the 21st century, the geological science in Japan entered stage of (4),"exporting science" with the introduction of new paradigms, such as the application of detrital zircon chronology to subduction-related orogens, which efficiently recognizes new geotectonic subdivisions and allows paleogeographical reconstruction with much higher resolution than before. These new paradigms (ideas, techniques) from Japan are now on sale for applying to the rest of the world.
The Hitoegane Formation, with the Middle Ordovician conodont, in the Hida marginal belt, Southwest Japan, represents the oldest sedimentary unit in Japan. In order to date the lowest part of the formation, U-Pb age of igneous zircon from tuff beds was measured by LA-ICP-MS. A felsic tuff bed from the lower part of the Hitoegane Fm was newly dated 472 Ma (latest Early Ordovician) that marks the oldest age for sedimentary unit hitherto reported from Japan. This result suggests that the basement of proto-Japan was probably older than the Ordovician. The Iwatsubodani Formation, an apparently underlying unit below the Hitoegane Fm, however, yielded U-Pb zircon age of 280 Ma (Early Permian). Thus this unit is too young to be the sedimentary basement of the Hitoegane Fm. Newly added also were some pieces of information on the U-Pb ages and stratigraphy of the Paleozoic-Mesozoic sedimentary units of the Hida marginal belt.
Food producers have increasing concerns about geographical brands as an efficient instrument for gaining market competitiveness. In the case of the Spanish wine industry, denominations of origin (DO) for wine have nearly trebled in number since the mid-1980s.DO is expected to allow producers to acquire market recognition not merely by specifying the places where products originate (origin appeal), but also by ensuring the unique quality associated with the place identified by a geographical term (quality appeal). These points of appeal, when combined, would generate added value for products and promote their sales in the market. However, the proliferation of DOs in recent years makes us reconsider if all of these DOs, with different features in terms of geographical scale or type of products, might assume equally their function of linking the origin and quality of a product. This article analyzes how DOs in the Spanish wine industry achieve product differentiation through a comparative study on three cases of DOs (DO Penedes, DO Cava, and DO Catalunya) overlaid on the Penedes Region in Catalonia.After examining the reason justifying the coexistence of the three DOs in the Penedes Region, the author analyzes in some detail how wine producers registered in different DOs make use of those geographical brands in their product strategies. An empirical study reveals that, although none of the three DOs in the Penedes region enjoy a reputation of prestigious geographical brand, they work efficiently for products as a distinctive sign in the market to be differentiated from generic products or other competing products made elsewhere.
Holocene environmental changes and vegetation history are constructed using phytolith and macroscopic-charcoal analyses of a 23-m-deep drilling core obtained at the Senchomuta marsh in Asodani Valley, northern part of Aso caldera, SW Japan. An intra-caldera lake existed in the Asodani Valley prior to approximately 9 cal ka (calibrated 14C age). Multiple large flood events occurred during the period 8.9-8.1 cal ka and emplaced thick sandy deposits in the valley basin. Thereafter, the center of the Asodani Valley (northern part of caldera floor) changed to swampy and fluvial environments. sasa (cool-temperature dwarf bamboo) grasslands and/or forests with understory sasa covered slopes of the Asodani Valley basin between 11 and 9 cal ka. sasa phytoliths significantly increased at ca. 7.3-6.5 cal ka, but thereafter decreased. Miscanthus (Japanese pampas grass) grasslands existed continuously on the slopes. Macroscopic-charcoal particles were abundant during the last 6000 years, and the peak (6.1 cal ka) amount of charcoal particles is consistent with that of Miscanthus phytoliths. This indicates that the existence of Miscanthus grassland might be related to fire events. Inside the Asodani Valley, Phragmites (reed) became established continuously along the shore of the intra-caldera lake (prior to ca. 9 cal ka) and in subsequent marshes. Gramineae phytoliths were detected predominately through all horizons of the drilling core, whereas a small amount of arboreal phytolith was observed at most horizons. We, therefore, believe that forests existed on steep slopes such as the caldera wall where human impacts were small, although sasa and Miscanthus grasslands were maintained by human activity outside Aso caldera.
The study investigates the past 1 Ma tephrostratigrapy of the Miyazaki plain in southern Japan. There are over 50 tephra layers, 80% of which originate from Kirishima volcano 25 km west of the plain. Several widely spread marker tephra layers in the layers and fission-track dating are used to establish tephrochronology. The explosive eruptive history of the volcano was reconstructed on the basis of tephrostratigraphy and tephrochronology. The history has two volcano groups: Pre-Kirishima 900-600 ka and Kirishima 600-0 ka. Pre-Kirishima volcanoes are unknown in detail.Kirishima volcano is divided into the Older Kirishima volcano, 600-330 ka, and the Younger Kirishima volcano, 330-0 ka.The Older Kirishima is characterized by calder-forming eruptions and large-scale pyroclastic flows, > 100 km(3) in volume. Older Kirishima consists of four stages: O1 (600-530 ka), O2 (530-520 ka), O3 (520-340 ka), and O4 (340-330 ka). The tephra of O1 includes over five crystal-enriched ash fall layers, which indicate that vulcanian and phreatomagmatic eruptions occurred intermittently at that stage. O2 is the first calder-forming stage, in which the Kobayashi-Kasamori pumice fall and pyroclastic flows and Kobayashi caldera were formed. The pumice falls and a co-ignimbrite ash fall of the pyroclastic flow were dispersed over 1000 km east of the source, and covered the western half of the main island of Japan. O3 tephra layers are composed of over ten tephra layers formed by intermittent plinian and phreatomagmatic eruptions. The latter indicates that lakes emerged in the caldera. O4 stage is a large-scale eruption with the Kakuto pyroclasatic flow and Kakuto caldera forming. The Kakuto pyroclastic flow was accompanied by a pumice fall and a scoria fall. They were small-scale scatterings near the source from small-scale eruptions, while the co-ignimbrite ash fall reached Kanto, which is 1000 km east of the source.The Younger Kirishima began with intermittent pumice and scoria falls soon after the O4 stage. The Younger Kirishima forms the main landform in the Kirishima volcano. Most of the Younger Kirishima tephra layers of more than twenty scoria and pumice falls were caused by plinian and sub-plinian eruptions accompanied by lava flows. The activity of the Younger Kirishima volcano is subdivided into four stages: Y1 (330-130 ka), Y2 (130-50 ka), Y3 (50-30 ka), and Y4 (30-0 ka) on the basis of thick soil and erosive horizon, which suggest quiet volcanic activity with no eruptions or only lava flow eruptions. Y1 includes over five tephra layers from sub-plinian eruptions in the western part of Kirishima volcano. There is a long quiet period between 240 ka and 130 ka. Y2 has six scoria falls, which show sub-plinian eruptions in the western part of the volcano. Y3 tephra is composed of Uchiyama pumice fall, Iwaokoshi pumice fall, and Awaokoshi scoria fall. Iwaokoshi from Onaminoike 40 ka old and Awaokoshi from Hinamoridake 30 ka old, were much larger eruptions than other tephra of the Younger Kirishima volcano. Forming stratovolcano at the source, they reach the Pacific Ocean and Miyazaki plain 50 km east of the source, while most of the Younger Kirishima tephra are distributed near Kirishima volcano. Y4 has more than ten pumice, scoria, and ash falls, which include historically recorded tephra layers. Of them, the Kirishima-Kobayashi pumice fall from Karakuni-dake 16.7 ka spread over the widest area, covering half of the Miyazaki plain and reaching the Pacific Ocean.
This paper examines the early stage of the geotectonic history of the Japanese Islands on the basis of finding hydrothermal jadeitite including zircons of ca. 520 Ma in serpentinite melange of the Itoigawa-Omi area of the Hida-Gaien belt, Central Japan. Hydrothermal jadeitite contains euhedral jadeite in natrolite veins and patches, and consists of jadeite-albite and jadeite-natrolite without quartz. These minerals were crystallized from an aqueous fluid phase at the low-pressure and high-temperature side of the reaction boundary of albite = jadeite + quartz in the system NaAlSiO4-SiO2-H2O. The occurrence of rounded relict hornblende mantled by omphacite rimmed by fine-grained aggregates of jadeite in the matrix of jadeite and albite suggests a pervasive hydrothermal fluid flow, through which metabasite was extensively replaced by jadeitite.This rather high-temperature hydrothermal activity of ca. 520 Ma did not occur in an ordinary subduction zone but in a newly-formed mantle wedge suffering severe hydration from a subducting slab. Recently accumulated U-Pb ages of zircon of ca. 450-500 Ma from paleozoic sediments and granitic rocks of the Hida-Gaien belt were due to initiation of subduction followed by subduction zone magmatism.Protolith of serpentinite in the Hida-Gaien belt includes highly depleted harzburgite, thus requiring tectonic setting of a high-temperature-rift zone rather than a low-temperature-slow spreading ridge. Subduction was initiated at ca. 520 Ma along the boundary between lowdensity harzburgitic rift zone peridotite and lherzolitic spreading ridge peridotite with a slightly higher density, resulting in the common occurrence of harzburgitic serpentinite in the oldest part of the accretionary complex of Southwest Japan.An area including the Japanese Islands was born around the Yangtze block by the breaking up of the Rodinia supercontinent, because the oldest K-Ar age of biotite actinolit rock of 672 Ma (Matsumoto et al., 1981) and the subduction initiation of ca. 520 Ma are in accord with the paleogeographic history of the Yangtze block, and because ca. 300 Ma Renge schists of the HidaGaien belt did not suffer the ca. 280-200 Ma collision-type metamorphism of the Hida metamorphic belt that is an eastern extension of the suture between the Sino-Korea and Yangtze blocks.
A dense nationwide seismic network recently constructed in Japan has been yielding large volumes of high-quality data that have made it possible to investigate the seismic structure in the Japanese subduction zone with unprecedented resolution. We introduce a precise configuration of the Philippine Sea and Pacific plates subducting beneath the Japanese Islands, which was recently obtained by seismic tomographic imaging, precise earthquake hypocenter determinations, and focal mechanism studies. Seismic tomographic studies show that the Philippine Sea plate subducting beneath southwest Japan is continuous throughout the entire region, from Kanto to Kyushu, without disruption or splitting even beneath the area north of the Izu Peninsula. The estimated geometry of the subducted Pacific and Philippine Sea slabs shows a broad contact zone between the two slabs located directly beneath the Kanto plain. It further shows the wavy configuration of the Philippine Sea slab subducting beneath the entire region of southwestern Japan. Contact between the Philippine Sea plate and the Pacific plate causes anomalously deep interplate and intraslab earthquake activity in Kanto. Moreover, the interplate coupling coefficient estimated from repeating earthquake data shows a distinct change across the northeastern edge of this slab contact zone, suggesting that the overlying plate controls large-scale interplate coupling. High-resolution studies of spatial variations of intraslab seismicity and the seismic velocity structure of the slab crust strongly support the dehydration embrittlement hypothesis for the generation of intraslab earthquakes.
Cenozoic western Pacific is characterized by numerous subduction volcanisms, opening of back arc basins, and within-plate volcanisms in backarc regions. These phenomena suggest that thermal disturbances induced by mantle flow caused mantle melting and eruption of magmas in back-arc regions, although diverse modes have been proposed for the mantle condition. To constrain the origin of the magmatism, it is important to clarify both the geodynamics and physicochemical conditions of the mantle in the arc-back arc system. Cenozoic back-arc volcanisms and tectonics in northern Kyushu are key objectives. This paper focuses on the dynamics of the upper mantle in relation to the tectonics of the area.Cenozoic volcanism of the northern Kyushu district is characterized by eruptions of a number of alkaline volcanisms. This volcanic province extends some one hundred kilometers along the Japan Sea coast and includes the Chugoku area. Although the volcanism has been regarded as a large single volcanic province, the northern Kyushu activity is distinguishable from that in Chugoku by geochemical characteristics.Cenozoic basalt volcanism in northern Kyushu occurred mainly in the Tertiary sedimentary basins, which is common to Cenozoic volcanism in the Japan Sea Basin. The sedimentary basin deposits underwent intensive folding with extensive inversion tectonics occurring mainly around the end of Miocene. Studies on dykes and thrust faults also indicate a compressional stress field dominated in northwestern Kyushu during the late Miocene. Initiation of the basaltic activity took place in Kita-Matsuura area and expanded outwards. Basaltic rocks from the Kita-Matsuura are mostly hypersthene-normative and sub-alkalic, whereas rocks from peripheries, such as North Kyushu and Goto Islands, are predominantly less normative-hypersthene and thus are alkalic. From spatial and temporal variations and genetic conditions of basalt magmas, a most plausible source was a small-scale mantle diapir with a potential temperature of more than 1400 degrees C.Combined with an inversion tectonic background after the Japan Sea opening event, the origin of the back-arc magmatism was unrelated to large-scale mantle upwelling. Fluid-fluxed melting of the mantle is not supported by the chemistry. My proposal is active upwelling of a small-scale mantle diapir, probably from the depth of stagnant slab or mantle transition zone.
Quantitatively estimating denudation is generally difficult because it essentially involves the removal and loss of materials in situ. The denudation rate of mountainous areas in Japan has commonly been studied from the volume of sediment in a basin or catchment. Nonetheless, the availability of these methods is constrained spatially by upstream area and temporally by depositional age. In the last few decades, thermochronometric methods that evaluate thermal history using radiometric-dating methods have been used to evaluate the denudation and tectonic history of orogenic belts around the world. The advantages of thermochronometric methods are that we can calculate the denudation rate at each sampling point and that combining multiple methods and/or target minerals enables us to calculate denudation rates in multiple periods. However, thermochronometric methods have been applied to areas with extraordinarily high denudation rates in island arc areas such as Japan. Thus, the effectiveness of thermochronometric methods for estimating denudation rates in island arc areas has not been demonstrated. We applied apatite and zircon fission-track thermochronometry to granitic rock samples collected from outcrops and a borehole to estimate the tectonic history of the Rokko area, southwest Japan. Previous studies suggested that the Rokko Mountains have been uplifted by active faulting along their northern and southern margins during the Rokko movements, a Quaternary tectonic movement in the Kinki district. However, the tectonic history of the Rokko area prior to 1 Ma has not been revealed due to a lack of prevalent geologic markers. We estimated average denudation rates in various periods based on apatite and zircon FT ages and previously reported radiometric ages. We obtained denudation rates at about 0.04-0.10 mm/yr after about 30 Ma, 0.05-0.7 mm/yr during 50-30 Ma, 0.7-4.0 mm/yr during 70-50 Ma. The denudation rate after the deposition of the Kobe Group (36.9-30.4 Ma) is estimated to be in the 0.01-0.1 mm/yr order, while bedrock uplift rate after about 1 Ma is estimated to be about 0.5 mm/yr. Thus, the tectonic activity of the Rokko Mountains area prior to 1 Ma has been relatively low.
Hitachi metamorphic rocks located in the southern part of the Abukuma Mountains, Northeast Japan, distinctively contain meta-volcanic rocks and meta/sheared granitoids. The igneous ages of meta-granite and meta-porphyry from the Hitachi metamorphic rocks were determined by the SHRIMP zircon method. In this paper, we describe occurrence, petrography, and petrochemical characteristics of these studied rocks. Meta-porphyry, with an igneous age of 506 Ma, intrudes into the meta-volcanic rocks of the Akazawa Formation of the Hitachi metamorphic rocks and has a micrographic texture and a spherulitic texture of an igneous origin. Previous studies have already reported an igneous age of 491 Ma for meta/sheared granitoids using the SHRIMP zircon method. Cambrian meta/sheared granitoid samples occur widely as a granitic body in the northeastern part of the Hitachi metamorphic rocks. (A) Meta-granite of the same age (498 Ma) as the sample used for the above dating is found as boulders in meta-conglomerates. The meta-conglomerate, which is found in the Daioin Formation of the Hitachi metamorphic rocks, lies unconformably on a Cambrian meta-granite body. Both meta-volcanic rocks and meta/ sheared granitoids have chemical characteristics commonly associated with island arc volcanism. As such, the Akazawa Formation is likely to have originated in the Cambrian era, although we have no SHRIMP age for meta-volcanic rocks of the Akazawa Formation.
This study attempts to estimate the source craters of the Yatsugatake-Kawakami Tephra Bed (Yt-Kw), one of the Yatsugatake Younger Tephra Beds (Yt-Kw, Yt-Pm1, Yt-Pm2, Yt-Pm3, and Yt-Pm4, in ascending order), using the refractive indices of orthopyroxene and plagioclase phenocrysts, for the purpose of constructing an eruptive history of the Yatsugatake Volcanic Chain in central Japan. Previous studies have already clarified that the source of the youngest Yt-Pm4 bed is located around the summit of Yokodake, north of the Yatsugatake Volcanic Chain, whereas the craters of the four other tephra beds have not been identified. Therefore, this study tries to find a correlation between distal tephras and proximal deposits, such as welded tuffs, to estimate the sources of the Yatsugatake Younger Tephra Beds. In addition, the lavas distributed in the proximal area are analyzed to examine whether they have any common refractive indices according to the area.Based on the results, the proximal deposits are classified into four groups: those from around Ioudake (group (1)), from around Tengudake (group (2)), from craters between Mugikusa Pass and Nakayama Pass (group (3)), and others. These results suggest that the Yt-Kw bed erupted from around Ioudake, and the Yt-Pm1, Yt-Pm2, and Yt-Pm3 beds from around Tengudake. Furthermore, the Yt-Kw bed is estimated to correlate with the Ioudake welded tuff because both pyroclastic products contain olivine phenocryst, and the refractive indices of the orthopyroxene and plagioclase phenocrysts are similar. The distribution pattern of the Yt-Kw bed also supports this correlation. Based on the similarity of refractive indices of phenocrysts, Mikaburiyama welded tuff may correlate with one of Yt-Pm1-3. These tephras may erupt in the near ages of Tengudake lower lava, Tengudake middle lava, and Tengudake upper lava.
Various characteristics of podiform chromitites, an enigmatic mantle rock member, are reviewed in this article. Chromitites are composed of chromian spinel, with the general formula (Mg, Fe2+) (Cr, Al, Fe3+)(2)O-4, and silicates (mainly olivine). The Fe3+ content is generally very low, being less than 0.1 to all trivalent cations, in mantle chromian spinels. The Mg/(Mg + Fe2+) ratio (= Mg#) changes inversely with the Cr/(Cr + Al) ratio (= Cr#), which increases with an increase of degree of partial melting of mantle peridotites. The Cr# of chromian spinel is generally higher than 0.4 (generally 0.6 to 0.8) in podiform chromitites, varying widely from 0.1 to 0.9 in the mantle peridotite. The podiform chromitite forms pod-like bodies (dimensions of up to 1.5 km x 150 m for an individual pod) with a dunite envelope, totally set within mantle harzburgite. In well-preserved ophiolites, they occur in the uppermost mantle, especially in and beneath the Moho transition zone, which is dominated by dunite. The Cr# of chromian spinel is relatively low (0.4 to 0.6) around the Moho transition zone, and high (> 0.6) at deeper levels in the mantle section. Chromitites are denser and less anisotropic in V-p than peridotites, and the V-p is 8.5 to 9 km/sec depending on the proportion of chromian spinel, and higher in the former than in the latter.The podiform chromitite has been interpreted to be one of melt /rock interaction products within the uppermost mantle harzburgite; hybridization of relatively Si-rich melt formed by the breakdown of orthopyroxenes of the wall harzburgite and subsequently supplied primitive melt cause oversaturation in chromian spinel, giving rise to formation of chromitite with a dunite envelope. The fractionated melt leaving high-Cr# podiform chromitite is possibly of arc-magma affinity. Chromitites with low-Cr# (0.4 to 0.6) chromian spinel can be in equilibrium with MORB. Recently found ultra-high pressure minerals, such as diamond, moissanite, Fe-silicides and Ni-Fe-Cr-C alloys, within chromian spinel of podiform chromitites make the genetical history of chromitites highly enigmatic. A new story, which incorporates the genesis and involvement of these highly reducing, ultra-high pressure minerals, is required.
図1の写真（撮影：中野 俊）は，表紙とほぼ同位置の13年前の状況を示す．撮影角度がやや異なるが，13年間の氷帽の変化を観察することができる．なお，Thompson et al.（2009）によれば，キリマンジャロ頂上の氷帽の面積は1912～1953年には約1%/yearの割合で減少していたが，1989～2007年には約2.5%/yearと変化し，減少速度を速めた．過去のデータ（Thompson et al., 2002）から外挿して今後を推測すると，2015年には氷河はほぼ消滅するとみられる（岩田・小森, 2010）．
Annual sea-surface temperatures (SSTs) (degrees C) were derived from a regression analysis between the ratio of warm-and cold-water diatoms (Td' ratio) in 123 surface sediment samples around the Japanese Islands and measured mean annual SSTs (degrees C) at the core sites. The cross spectra between the atmospheric residual C-14(%(0)), and annual SSTs (degrees C) of cores DGC-6 (Japan Sea) and MD01-2421 (off Kashima), respectively, consist of five dominant periods: 6000, 2400, 1600, 950, and 700 years.The amplitude of fluctuations of annual SSTs (degrees C) in the millennial time scale during the Holocene after the Younger Dryas is within 6-10 degrees C. Periodic variations of annual SSTs (degrees C) can be correlated within error to abrupt climatic events reported from different paleoclimatic proxy records in many regions of the Northern Hemisphere. The cooling time of annual SSTs (degrees C) also corresponds to the triple events of high C-14 values in the atmospheric residual C-14 records, as well as the Bond events in the North Atlantic.
We measured the Pb-206/U-288 age distribution of detrital zircons in five psammitic schist samples from the Sanbagawa Belt in east-central Shikoku and the western Kii Peninsula to constrain their depositional age. The age-distribution diagrams for the five psammitic schist samples all show that detrital zircons of 100 to 90 Ma are most abundant and the age of the youngest zircon in each sample is less than 80 Ma. Considering the age of the retrogressive metamorphism of these psammitic schists, ca. 80-60 Ma, the protoliths age of the psammitic schists is constrained to 75-70 Ma, correlative to the age of the sandstone of the Middle Shimanto Belt (Yanai, 1984). A similar age-distribution has already been reported for two psammitic schist samples from the Central Unit of the Sanbagawa Belt in the Kanto Mountains (Tsutsumi et al., 2009). Thus the Sanbagawa Belt is most widely occupied by metamorphic rocks originating from rocks of the Middle Shimanto Belt.We also measured the Pb-206/U-258 age distribution of detrital zircons in Turonian sandstone from the Northern Shimanto Belt in the central Kii Peninsula. The age-distribution diagram shows that detrital zircons of around 128 Ma are most abundant and the age of the youngest zircon in the sample is about 100 Ma. A similar age-distribution has already been reported from a psammitic schist sample from the Southern Unit of the Sanbagawa Belt in the Kanto Mountains, overlying the Central Unit (Tsutsumi et al., 2009) . The protolith age is still younger than the metamorphic age of the eclogites in central Shikoku, ca. 120-110 Ma (Okamoto et al., 2004), which occupy the uppermost portion of the Sanbagawa Belt.Although some previous studies suggested that the Sanbagawa Belt consists of metamorphosed Late Jurassic to Early Cretaceous accretionary complex, the present study shows that the belt is largely occupied by metamorphosed Late Cretaceous rocks: the Shimanto Metamorphic Rocks of Aoki et al. (2007). As a result, the Sanbagawa Belt consists of the following three units with different protolith ages: (1) Lower Unit of Shimanto Metamorphic Rocks with protoliths ages of 75-70 Ma and metamorphic ages of 70-60 Ma, (2) Upper Unit of Shimanto Metamorphic Rocks with protoliths ages of 95-85 Ma and metamorphic ages of 85-75 Ma, and (3) Sanbagawa Metamorphic Rocks (s.s.) with protoliths ages of Late Jurassic to Early Cretaceous and metamorphic ages of 120-110 Ma. The protoliths of the Upper and Lower units of the Shimanto Metamorphic Rocks are most likely rocks of the Northern Shimanto and Middle Shimanto belts, respectively.
The importance of Holocene sea-level change has long been a central theme of Quaternary Science. Holocene sea-level records provide direct evidence of the progress of the melting of the ice sheet during the Holocene. Although the correlation between ice and ocean volumes is incontrovertible, casual links are commonly obscured. Some regional studies of coral-reef sites based on analyses of boring cores have been carried out from reef flat to reef slope at present-day reefs, demonstrating a long-term (1000-10000 years) and large-amplitude (10-100 m) melt-water history. However, short-term (< 100 years) and small-scale (< 1 m) sea-level changes that detail past sea-level records and play a major role in predicting sea-level fluctuations in the near future are not observed from reef cores. This paper is based principally on a re-examination of sea-level records from the literature and presents the following suggestions to reconstruct high-resolution Holocene sea-level records: (1) Identifying species from boring core samples is effective to reconstruct sea-level changes more precisely during the Holocene. (2) Relative abundance of data for each species is essential to determine position and course of sea-level curve within the envelope of their living depths. (3) The accuracy of reconstructing the sea-level record depends on the distribution pattern of corals; the vertical distribution in a present-day reef obtained from a site close to a given boring site is all that is required. The sea-level curve based on agreement with the above requirement is characterized by smaller fluctuations (±0.5 - ±2.5 m) during the Holocene, thus studies on the high-resolution sea-level record will provide predictions for research on the spatial and temporal histories of sea-level change to Holocene sciences and management of conservation of land in the near future.
The present situation of studies on accretionary wedge formation and related phenomena is briefly summarized from various perspectives, ranging from theories, model experiments, observations on land and submarine, exhumation of high-pressure metamorphic rocks, fluid seepage, stress field, and asperity. Future perspectives are also considered from such recent results with potential areas of study. Gravity acts ubiquitously-everywhere and at all times-on the Earth's materials, so the role of gravity is also accounted for in the wedge development.
Structure(regime) of the global environmental system composed of atmosphere, oceans and marine ecosystems has repeatedly shifted from one state to the other on an interdecadal time-scale, which is called "regime shift"(RS). The RS was first discovered in 1983 with synchronous fluctuations in biomass of three distantly separated sardine populations in the Pacific, which were closely linked to the global air temperatures, and the synchronized occurrences of an alternation between the sardine and anchovy in different areas were also observed. Similar synchronized variations have been detected thereafter in a wide range of taxa and ecosystems. Since the late 1980s, the RS has been reported about the ocean climate in the North Pacific Ocean as well as in the Atlantic. Studies in these different areas have been merged, creating a new interdisciplinary study area. The concept of the RS has had an effect on the traditional management regime of marine living resources and the UN Convention on the Law of the Sea has to be re-examined. Global warming and overfishing could disrupt the normal processes of the RS.
Studies on geologic structures including some deformation microstructures in both areas along the Median Tectonic Line (MTL) in western Shikoku and of the South Fossa Magna indicate that N-S trending horizontal compression tectonics prevailed in these areas during the earliest Middle Miocene (ca. 15 Ma). Also, a review of structural development in Nankai province indicates that similar compression tectonics prevailed during the periods from the Early to earliest Middle Miocene (ca. 20-15 Ma). These periods are nearly coeval with the timing of the Japan Sea opening. Although there is uncertainty about the reactivation of the MTL around this time, south-dipping normal faults were formed in the Sambagawa belt truncating the MTL to produce the Kuma basin (18-16 Ma), which were later reactivated as thrusts (Tobe and Hanayama thrusts), indicating inversion tectonics. In the South Fossa Magna region, not only a large amount of shortening—as much as 40-50%—was caused in the Momonoki Subgroup (earliest Middle Miocence, 16-15 Ma) by folding strata, but also the constituent quartz grains were moderately plastically deformed and microcracked followed by healing (i.e. healed microcracks), indicating deformation under brittle-ductile transition conditions (ca. 300°C) at ca. 15 Ma. Furthermore, slaty cleavage caused by pressure solution developed in the strata constituting the Oligocene-Early Miocene (>20 Ma) Southern Shimanto belt, and forearc sediments (18-15 Ma) as thick as 4000 m overlying these sediments with angular unconformity (e.g. Tanabe and Kumano Groups in the Kii peninsula) were also deformed by folding with a shortening ratio of 10-20%. All these onland geological facts in the forearc region indicate that the forearc region was in a regime of compression, while the back-arc region was in a regime of extension at the same time during the Japan Sea opening. Similar tectonics also occurred in Italy, where the Tyrrhenian Sea (back-arc basin) has opened since the Pliocene (5 Ma), while shortening tectonics shown by the development of fold and thrust belts and deep (>7 km) basins occurred at the same time in the forearc region. Although these concurrent back-arc extension and forearc shortening are difficult to interpret, they may be caused by ridge push force (i.e. gravity tectonics) after back-arc spreading commences so that extensional force is no longer sustained in the arc.
In mid-November, 2009, a breach of the server of the Climatic Research Unit (CRU) of the University of East Anglia, UK, occurred, and more than 1,000 e-mails were copied and disseminated over the Internet. CRU is one of the leading climatology institutes, and has constructed a long-term world temperature database that was referenced in the assessment report of the Intergovernmental Panel on Climate Change (IPCC) as evidence of global warming. The words “trick” and “hide the decline” in an e-mail, which mentioned the process for preparing the temperature time series, generated the allegation; those words demonstrated that scientists at CRU intended to falsify data to exaggerate warming. However, it can be regarded that the allegation was a manufactured controversy originating from irrelevant interpretations of personal e-mails at CRU. Scientists are now being requested to ensure that scientific knowledge and understanding are convincing not only to scientists but also to the general public.
