The Tokyo Lowland situated in the eastern part of Tokyo Metropolis was composed of extensive paddy fields until the end of the Edo era in 1868, then became a major industrial area from the beginning of the Meiji era due to the industrialization project of the early Meiji Government. The purpose of this paper is to clarify the changes in the industrial area in the Lowland since the beginning of the Meiji era, and to investigate the recent use of former factory sites following the relocation and closing of factories since around 1960. In the early part of the Meiji era, the industrial area only occupied the western part of the Lowland, the estuary of the Sumida River, and the junction of the Shakujii River and the Sumida River, and the main factories belonged to the shipbuilding and military industries. Then, over the period of two major wars, Shino-Japanese War (1894-1895) and Russio-Japanese War (1904-1905), the industrial area continued to be enlarged. At the end of the Meiji era, in 1912, many factories were developed along canals throughout the Kohtoh Area. Furthermore, the industrial area was developed throughout the Lowland during the period straddling World War I (1914-1918) and World War II (1941-1945). Although the industrial activity in the Lowland stopped for a several years from the end of the World War II in 1945, it started again with the outbreak of the Korean War, in 1950, and advanced remarkably mainly in the heavy and chemical sectors. However, this extreme industrial development brought to the Lowland the overpopulation and the public nuisances such as air-pollution, noise, and vibration from plants and manufacturing sites. To reduce these problems, the National Government and the Tokyo Metropolitan Government took such measurements as restricting the construction of new factories and strengthening regulations on the operations of factories. The regulations to prevent public nuisances were very costly to factory operators. As a result, the number of factories in the Lowland stopped increasing around 1960, and the number decreased rapidly from 1961 to 1975 because of relocation to other countries or ceasing manufacturing operations. Many former factory sites have been converted to other uses, mainly facilities for citizens such as condominiums, general residential areas, parking lots, schools, and parks. In particular, mainly at the sites of former metal industry, timber, and chemical industries, conversion to residential quarters has been remarkable. Among the new uses changed from former factory sites, the residential use occupies more than 50%. However, the change in land use from former factory sites to a residential quarter has brought problems throughout the Lowland area such the blocking of sunlight to existing houses due to the construction of housing complexes, and soil pollution caused by past industry activity. To reduce the problem of the blocking of sunlight to existing houses, each ward government has regulated the construction of housing complexes, and to reduce the problem of soil pollution, the National Government has promulgated the Soil Contamination Countermeasures Law. In addition to these problems, the extension of the subway network to the Lowland area in recent years has promoted an expansion of the residential quarter. This rapid expansion has led to a shortage of public institutions such as elementary and junior high schools. Furthermore, most of the Lowland area is permanently below sea level due to land subsidence, although the land is protected by extensive dikes and drainage systems to prevent disasters related to high tides and flooding. It is essential to solve these problems related to land use in this Lowland area.
The author studied the alluvial lowland in the lower reaches of the Hino and the Echi Rivers, to clarify landform development of the Kotoh plain to the east shore of Lake Biwa, central Japan, during the middle and late Pleistocene. Four major litho-stratigraphic units (A-D) and five tephra layers (Sakate, AT, DNP, hpm2, Ng-1) were detected from standard penetration test samples of Kominami borehole site cores from the lower reaches of the Hino River. Judging from the facies of the borehole samples and a geological cross-section through the Kominami site in the lower reaches of the Hino and the Echi Rivers, coarse sediments were deposited at least 4 or 5 times during the last 300 ka and the distribution of gravel deposits was much larger especially during the period from ca. 80 to 27 ka than at present. The appearance and shrinkage of the area where gravels were deposited seem to be related to interglacial-glacial or the interstadial-stadial cycles.
We report briefly the fossilized chemosynthetic molluscan assemblages found along the coastal area of Tabango and Villaba municipalities, northwestern Leyte, Philippines. This is the first discovery of fossil cold-seep assemblages in Southeast Asia. The geology of the study area is tentatively divided here into four formations ; namely, Formations A (locs. 11-13, upper Miocene), B (loc. 10, upper Miocene to lower Pliocene), C (locs. 1-9, lower Pliocene), and D (loc. 2, upper Pliocene or lower Pleistocene) from older to younger, based on lithology and calcareous nannofossil biostratigraphy. Among these formations, Formations A, B, and C yield fossil cold-seep assemblages. The assemblages show considerable variations in their modes of fossil occurrence. At location 4, several huge indurated carbonate blocks (ca. 5 meters in maximum diameter ; δ13C =-42.03‰ and δ18O = 0.91%o vs. PDB), lags of weathered sediments, contain beautifully preserved, large vesicomyid, lucinid, thyasirid, and mytilid bivalves. Inarticulated valves of vesicomyds and lucinids are dispersed within a slump bed at location 5. Densely packed, articulated lucinids are in massive authigenic carbonates at locations 2 and 7. Large articulated solemyid valves, attaining 20 cm in maximum shell length, show sporadic occurrences in massive siltstone (loc. 10). A swarm of articulate and inarticulate lucinid valves are found together with conglomerates of calcareous gravels within asphalt sands (loc. 12). The importance of this discovery is : (1) it provides the first record from the barren area of fossil cold-seep assemblages in Southeast Asia; (2) beautifully preserved fossil material that might contribute to the systematics of fossil cold-seep bivalves ; and, (3) greater number of variations of modes of fossil occurrence in a limited area and horizon than anywhere else so far documented.
Towada volcano is an active caldera volcano located at the northern part of the Northeast Japan arc. We re-examined the tephra stratigraphy of the post-caldera stage (15 ka to present) of Towada volcano, and carried out AMS radiocarbon dating of six soil samples taken from directly below the tephra layers. The most suitable ages of eruptive episodes A, B, C, D, D', E, F, G and Ninokura Scoria are estimated to be 1.1, 2.8, 6.2, 7.6, 8.3, 9.4, 10.1, 10.6, and 11-15 ka, respectively, on the basis of the thickness of soil layers between tephras and the radiocarbon ages determined by present and previous studies. This result shows that the eruption intervals have become longer with time, and the frequency of eruptions has decreased with time. Although the cause of this change is not known as yet, these are important data for predicting long-term eruptive activity of Towada volcano.
The longshore variation of the relative sea-level history in the southern half of the Kujukurihama strand plain, eastern coast of the Boso Peninsula, is reported and discussed in terms of differing rates of uplift. The central part of the plain has experienced a 5 m fall of relative sea level during the last 6, 000 years. The relative sea-level fall is marked by the seaward lowering of the facies boundary within the subsurface beach deposits, which is recognized in drill core sections and ground-penetrating radar profiles. A ground-penetrating radar survey was performed to reconstruct relative sea-level curves at the southern and southernmost parts of the strand plain. The relative sea-level history during the last 6, 000 years varies alongshore with the net sea-level fall being larger southward. The difference in the relative sea-level curve between the central and south parts temporally decreases from 2.4 m at 5.7 ka, through 1.6 m at 3.5 ka, to 0.9 m at 1.7 ka, becoming zero at present. The trend was caused by the uplift of the southern part relative to the central part, of which the average rate is 0.42 mika. The rate is equivalent to that inferred from the distribution of the last interglacial marine terrace surrounding the Kujukurihama strand plain.
Topography and geology of wild stands of endangered plants, Magnolia tomentosa (M. t.), Acer pycnanthum (A. p.), and Chionanthus retusus (Ch. r.) are studied. These three trees, which belong to the Tokai hilly land element, are mainly distributed in wetlands of the Tokai region in Japan. The habitats of M. t., A. p., and Ch. r. are analyzed on the basis of various field survey data such as on location, altitude, topography, geology, and water level. The results are as follows. 1. The habitats of the three species have slightly different characteristics in terms of altitude, and relations to topography, geology, and water level. 1) altitude : M. t. (low) → A. p. · Ch. r. (high) 2) inclination : M. it (small) → A. p. · Ch. r. (large) 3) height above water level : M. t. (small) →A. p. · Ch. r. (large) 2. Each habitat consists of various rocks and strata such as gravels of the Tokai group, Mesozoic rocks, and granites and so on, contrary to opinions that habitats are closely related to the Toki gravel bed of the Tokai group.
The Himalayan orogen represents a fold-and-thrust belt characterized by a series of foreland-propagating thrust systems with an out-of-sequence thrust (OST). Geological and geomorphological evidence implies that the Himalayan upheaval started from the north and shifted gradually southward with time. The uplift seems to have been accelerated in the Higher Himalaya since the Pliocene. To investigate the role of OST in recent uplifts of the Higher Himalaya and to estimate the denudation rate of the latter, we carried out fission track (FT) dating on zircon and apatite of high-grade pelitic and granitic gneisses from both sides of an inferred OST north of the Kathmandu nappe and along a traverse across Gosainkund Lekh in the northern root zone of the Kathmandu nappe. Nine zircon FT ages of sites in the Gosainkund Lekh area range from 1.5 Ma (at 1525 m) to 2.8 Ma (at 5045 m). Ages of four samples from the northern slope of the area increase linearly with elevation, and yield an average denudation rate of 2.4 mm/y. On the other hand, six samples from the southern slope yield identical ages (2.5-2.8 Ma) regardless of their sample elevations (1150-5045 m). The zircon ages of the area suggest that rocks on the southern slope passed evenly the depth of closure temperature of zircon at around 2.6 Ma. Following this, the northern part of the southern slope (the highest part of Gosainkund Lekh) and the northern slope were uplifted more rapidly than the southern slope. Eight zircon FT ages and seven apatite FT ages from rocks around the Sheopuri zone range from 4.4 Ma to 6.9 Ma and 4.3 Ma to 5.5 Ma, respectively. These ages vary irrespective of their sample elevations (1200-2400 m). Furthermore, zircons and apatites from both sides of the OST (Trisuli-Likhu fault) yield almost the same FT ages, suggesting that the OST has been inactive since the latest Miocene. It is noteworthy that zircon FT ages from the sample elevations between 1200 m and 1800 m in the present area together with zircon FT ages (ca. 9 Ma) reported from early Paleozoic granites in the southern part of the Kathmandu nappe suggest a general trend of younging towards the north between 9 Ma and 1.5 Ma. On the basis of such a trend, two possible uplift mechanisms of the Kathmandu nappe and its northern root zone in the Higher Himalaya are presented. Both mechanisms might be related to crustal ramp due to northward wedging of Indian mid-crust beneath the Himalaya.
Landslides triggered by the 2004 earthquake in Niigata formed dams and lakes along the Imokawa River. These lakes were rapidly buried with sediment, which was primarily composed of fine to medium sand derived from unconsolidated sedimentary rocks (Shiraiwa and Uono Formation), transported by the Imokawa River. Similar very fine sand deposits were observed in a river terrace situated 70 m above the Imokawa river bed. The objectives of the survey were : i) to compare present lake deposits behind landslide dams with terrace deposits distributed along the Imokawa River, and ii) to consider the effects of sediment load increases after the earthquake on river terrace-forming processes. Three types of sedimentary facies were observed in the landslide dam deposits : i) fairly wellsorted and obscurely stratified fine to medium sand deposit, with evidence of upward fining and a lack of silt and clay, ii) laminated deposit of silt and very fine sand, and iii) parallel bedding sand deposit with gravel particle lenses. Sedimentary facies i) and ii) are related to lake-enlarging stages, while facies iii) is related to Imokawa riverbed deposits after the lake filled with sediment. Eight terraces along the Imokawa River, divided into three groups (H1-H2, M1-M2, L1-L4), were classified and mapped. Their longitudinal profiles illustrated that terraces along the Imokawa River are consistent with those along the main stream, the Uono River. Most of these terraces are erosional, however, at three sites (Loc. 1, Loc. 4, Loc. 5) we observed well-sorted and obscurely stratified fine to coarse sand deposits of 2-3 m in thickness, with upward fining and a lack of silt and clay, that continued at times to laminated deposits of silt and very fine sand. At the top, coarser sand layers with gravel particle lenses were found. These facies are very similar to the present lake deposits behind landslide dams. Moreover, Carbon-14 dating for Loc. 4 and Loc. 5 deposits on a lower terrace plain estimated the occurrence of a landslide dam at ca. 2900 yBP. It is possible that this landslide event was triggered by a former large earthquake in Yamakoshi. Every few thousand years, well-sorted massive sand deposits behind landslide dams, which are triggered possibly by earthquakes, must have been formed along the Imokawa River; however, almost all of these deposits have been eroded away. We expected that the increasing sediment loads caused by earthquakes would have caused the river floodplain to widen, but such a river channel metamorphosis has not occurred along the Imokawa River as small amounts of gravel particles were supplied in the geological setting of the Shiraiwa Formation. Fluvial terraces along the Imokawa River have developed every few ten thousand years, while the riverbed height of the main stream, the Uono River, has remained almost constant.
The 17th International Sedimentological Congress was held at the Fukuoka International Convention Center, Fukuoka, Japan, from August 28th through September 1st. The Congress, ISC 2006 Fukuoka, was the first Sedimentological Congress to be held in East Asia in its 46-year history. It was organized and prepared in cooperation with neighboring countries and districts. The congress opened with an address by the President, Judith MacKenzie. The total number of registrants was 736, including 331 from Japan and 405 from other countries. There were 240 students, or about 33% of all delegates. Among the 240 students, 34 were supported by ISC travel grants, and about 30 were supported by IAS grants. In addition to these grants, some of the sessions provided support to contributors. Thus, the main reasons for the large number of participants were extensive support given to students and young researchers from developing countries and territories, as well as a strong interest in the geology and culture of Japan. The large number of participants from East Asian countries also increased the total number of registrants. We believe that IAS has established a firm position in East Asia through ISC 2006 in Fukuoka, and the Sedimentological Society of Japan has also established its position in the earth science community as a very visible and mature community of scientists. We express our sincere gratitude to the Tokyo Geographical Society for its financial support.
The Society of Exploration Geophysicists of Japan (SEGJ) hosted the 8th SEGJ International Symposium on Imaging and Interpretation Technologies at Kyoto University Clock Tower Centennial Hall, Kyoto, Japan on November 26-28, 2006, following a tutorial course for young geoscientists and engineers on 24 and 25 at Kyotodaigaku Kaikan. A technical tour was also held on November 29. The symposium was co-sponsored by the Korean Society of Exploration Geophysicists (KSEG), the Australian Society of Exploration Geophysicists (ASEG), the Society of Exploration Geophysicists (SEG), European Association of Geoscientists and Engineers (EAGE), and the Environmental and Engineering Geophysical Society (EEGS), and Vietnam Association of Geophysicists (VAG). Discussions at the symposium focused on Imaging and Interpretation technologies that contribute to Interdisciplinary Integration of Geosciences for better understanding and modeling invisible underground structures and processes. In particular geophysical imaging technologies, such as seismic methods, electrical and electromagnetic methods, ground penetrating radar, gravity and geomagnetics in various applications in human activities, such as natural resource exploration, civil engineering, environmental applications, and natural hazard mitigation were discussed as a major theme of the symposium. Also, our discussions included theoretical developments in geophysical methods, laboratory measurements, various data-processing schemes, and modeling and inverse theories that help to understand geoscientific processes in the invisible underground. Geophysical data management and integrated geophysical technologies were recognized as indispensable tools for deepening our understandings of subsurface structures and focusing into survey objectives.
The distribution of living organisms extends deep into the Earth's interior, according to the results of studies that have identified microbial communities in samples from deep-sea and land boreholes. Microbial communities found in bore-hole rocks and water mainly consist of both chemoautotrophic and heterotrophic prokaryotes. Most prokaryotes are extremophiles that can survive or adapt to extreme subsurface environmental conditions. Heterotrophic eukaryotes such as fungi, ciliates, and yeast are also sometimes found. We collectively call such microbial communities “the deep subsurface biosphere”. This is an important component of the Earth's biosphere, because the biomass of the deep subsurface biosphere is considered to be generally similar to surface dwelling biotic communities. Almost nothing is known about the new organisms found in the deep subsurface biosphere in terms of phylogenic relations with deep subsurface organisms and surface dwelling organisms whether there are any relict organisms that are completely isolated from modern fauna and the roles the subsurface biosphere plays in the Earth's interior. Here, I review the current status of deep subsurface biosphere research. Research on the deep subsurface biosphere is link to wide variety of interdisciplinary topics such as the roles of global biogeochemical cycles, origin of life, and astrobiology. I heartily encourage any fields of geoscientists to join in this fascinating research field.