著者

梶田 真

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.127, no.1, pp.53-72, 2018-02-25 (Released:2018-04-14)

参考文献数

37

被引用文献数

1

---

Because of limitations regarding available statistical data for units of year and enumeration, studies on socio-spatial patterns of Tokyo have not responded sufficiently to the dynamics of the so-called “doughnut phenomenon” period—a combination of urban sprawl and inner city decay—from the late 1960s to the early 1990s. Social maps for 1965 at the cho scale are created using statistics produced separately by the Tokyo Metropolitan Government. These maps are compared to those for 1980, because only the population censuses for 1965 and 1980 enumerate occupation data at this geographical scale. Subsequently, the dynamics of socio-spatial patterns in Tokyo for this period are examined. There were significant changes to names and territories of cho following enactment of the Addressing System Act of 1964. This was a serious problem for creating a social map on the cho scale, which was overcome by allocating either the 1961 cho territory or the current one according to cho name and date of statistics. The results of the analysis demonstrate that, in 1965, white-collar areas were formed as buffers around radial commuting train lines in western Tokyo, and areas between these in outer western Tokyo were not white-collar. Therefore, a star-shaped model, rather than a sector one, is suitable for representing socio-spatial patterns of the inhabitants of Tokyo in 1965. In 1980, the white-collar occupation ratio of these “between” areas rose rapidly, and a sectoral pattern clearly emerged. In eastern Tokyo, almost all areas were blue-collar in 1965, and moderate white-collar areas emerged along radial commuting train lines. The four main reasons for these changes are: 1) housing complex development at the sites of large plants; 2) abolishment of green belt policy; 3) new construction and expansion of radial train lines, especially subway lines; and, 4) expansion of sewage service areas. In western Tokyo, the culvertization of medium and small rivers, around which were former industrial areas, also made an important contribution to transforming blue-collar areas into white-collar areas. These results show the importance of infrastructure development in bringing about socio-spatial changes in Tokyo during this period.

著者

鈴木 敏

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.2, no.5, pp.224-233, 1890-05-25 (Released:2010-10-13)

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.2, no.4, pp.197a-198, 1890-04-25 (Released:2010-12-22)

著者

山崎 晴雄

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.1, pp.220-220, 1991-02-25 (Released:2009-11-12)

著者

小池 敏夫

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.1, pp.201, 1991-02-25 (Released:2009-11-12)

著者

小出 仁

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.2, pp.294-296, 2007-04-25 (Released:2009-11-12)

参考文献数

11

被引用文献数

1

著者

遠藤 毅

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.115, no.4, pp.500-507, 2006-08-25 (Released:2009-11-12)

参考文献数

19

被引用文献数

1 1

---

Modern manufacturing factories in the Tokyo Lowland-the developing eastern part of Tokyo Metropolis-were originally constructed by the national government at the beginning of the Meiji era in about 1870. Subsequently, the area developed as one of the important industrial areas in Japan. In particular, industrial development was remarkable during the period from about 1950 to about 1960. However, this extreme industrial development brought overpopulation and public nuisances such as air and noise pollution and vibration from plants and manufacturing sites in the Lowland. To ease this serious situation, the national government and the Tokyo metropolitan government took measures such as restricting construction of new factories and strengthening regulations on the operation of factories.Through these measurements, the increase of manufactories in the area stopped in about 1955, and many have disappeared since about 1960 because of their transfer to other cities or manufacturing operations shutting down.According to this investigation, many sites of factories and warehouses had their use diverted by citizens to facilities such as condominiums, general residential areas, parking lots, schools, and parks. In particular, conversion to residential use has been remarkable.

著者

久田 英子

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.110, no.1, pp.1-16, 2001-02-25 (Released:2009-11-12)

参考文献数

103

---

The Vredefort Dome, located in the central part of the Witwatersrand Basin in South Africa, is the type locality for pseudotachylite. Pseudotachylite at the Vredefort Dome is generally regarded to be of impact origin. Pseudotachylites which are closely associated with faults are, however, also known to be common along the northern and northwestern edges of the Witwatersrand Basin. In order to compare pseudotachylites from the Vredefort Dome and from the surrounding Witwatersrand Basin, different studies were undertaken in the past. Mode of occurrence, microscopic textures, geochemical analyses and chronological measurements of pseudotachylites are briefly reviewed in this paper.In the Vredefrot Dome, pseudotachylites are commonly observed except in the central part of its core. In the surrounding Witwatersrand Basin, they are reported from drill core sections and in underground workings. The matrix in pseudotachylite from the Vredefort Dome is mostly a recrystallized melt phase, while those from the surrounding Witwatersrand Basin seem to be composed of clastic material. Pseudotachylites both from the Vredefort Dome and the surrounding Witwatersrand Basin are geochemically closely related to their host rocks. Although evidence for more than one generation of pseudotachylite has been presented, both in the Vredefort Dome and the surrounding Witwatersrand Basin, it is widely believed that most of them were formed as a result of the Vredefort impact event (ca. 2.0 Ga). Other fault rocks reported from the surrounding Witwatersrand Basin are older than the pseudotachylites and therefore not related to their formation.

著者

武永 健一郎

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.77, no.1, pp.37-55, 1968-02-25 (Released:2009-11-12)

参考文献数

63

被引用文献数

2

---

The purpose of this paper is to classify low-altitude erosional surfaces in Japan and also to investigate the characteristic features of the granite mountains.Mt. Suzugamine at the western part of Hiroshima city is consisting only of granite. The geomorphic surfaces of Mt. Suzugamine are classified roughly into two, Higher-Setouchi surfaces and Lower-Setouchi surfaces. Yamada surface of the Plio-Pleistocene in origin and Piedmonttreppen belong to the former and gentle slope remnants of early-middle Pleistocene and “Kannon surface” of middle-late Pleistocene belong to the latter. Neither marine terraces nor tephra are found in this area. As a result, it is difficult to correlate these with the geomorphological surfaces elsewhere which have already been well examined.The gentle slopes were formed by the removal of deeply weathered granitic top soils about 50 m in thickness and the climatic change seemed to be less active.Landforms were modified even in Würm glacial period as was seen in the “Kannon surface”. The agencies which formed the initial gentle slope is similar to one which formed “Kannon surface”.Suzugamine mountains, which consists of granite, is characterized by gentle slope, box valley, earth fall, block stream, wide-opening valley and inward-opening valley. I should like to propose to term such geomorphology “granite topography”. It may be seemed that downwarping movement toward the Inland Sea (Setonaikai) has lasted down to the Pleistocene period, on the ground that the upper streams running down northward were captured by the ones running down southward.

著者

栗谷 豪

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.116, no.1, pp.133-153, 2007-02-25 (Released:2010-02-25)

参考文献数

103

被引用文献数

1 2

---

Water has been continuously degassed from the Earth's interior by magmatism throughout evolution, and can significantly affect dynamic processes of its carrier, i.e., magmas, during their transport from the mantle to the Earth's surface. This paper summarizes the effects of water on the physical and thermodynamic properties of magmas, and their roles in magmatic processes. Magmas commonly contain at least 0.2 wt.% of water, and some magmas can have up to 6 wt. %. Despite the fact that water is a minor component in silicate liquids, the effects of dis-solved water on the properties of silicate melt are significant because it has a much lower molecular weight at 18.0 than those of the other components (SiO2. 60.1, for example). Dissolved water greatly affects the density and the viscosity of silicate melts, thereby controlling rates of dynamic processes of magmas, such as segregation of primary melts in the mantle, transport of magmas from the mantle to the crust, convections and crystal-melt separation in crustal magma chambers, and ascent of magmas in volcanic conduits. Water also influences solid-melt thermodynamic equilibrium relationships, and this affects the chemical differentiation paths of magmas, in addition to the amount of melt production in the mantle by changing solidus temperatures. The eruptive behavior of volcanoes is driven by the exsolution of magmatic water, and as such depends on the water solubility of magmas mainly as a function of pressure. Water has also played important roles in the evolution of the Earth. Magma generation has been induced by water in the Earth's interior, and magmas have carried materials and energy from the interior to the surface of the Earth. In particular, water transport beneath an island arc is important in the global water cycle, and has greatly affected the environment of the Earth's surface.

著者

藤原 治 小松原 純子 高田 圭太 宍倉 正展 鎌滝 孝信

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.115, no.5, pp.569-581, 2006-12-25 (Released:2009-11-12)

参考文献数

36

被引用文献数

9 9

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The temporal development of a late Holocene strand plain system along the western Shizuoka Prefecture was reconstructed based on facies analyses and 14C dating for core samples excavated in a back marsh using a geo-slicer, 6.0-m-long, 0.35-m-wide, and 0.05- to 0.1-m-deep wedge-shaped stainless steel case. The strand plain system consists of beach, sand dune, and back marsh. Stratigraphic succession of the strand plain system, up to 4.4 m thick, is composed of upper shoreface sand, foreshore sand, backshore sand, and back marsh mud, in ascending order. The succession shows three development stages of the strand plain system.Stage 1 (before the 13th century) : The study area was under a wave-dominated beach environment. The beach system was developed by progradation of shoreface, foreshore, and backshore deposits in the later period of this stage.Stage 2 (from the 13th century to the 16th century) : Sand dune and back marsh developed, covering the beach deposit. Humic mud was thickly deposited in the back marsh with low sand supply from seaward across the dune.Stage 3 (after the 17th century) : The back marsh has been infilled mainly by washover sand and debris from the hinterland. The AD 1707 Hoei Earthquake Tsunami, which destroyed villages on the dune, possibly promoted reactivation of sand movement from ruined dune to the back marsh.

著者

長岡 信治

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.97, no.3, pp.156-169, 1988-06-25 (Released:2009-11-12)

参考文献数

28

被引用文献数

4 2

---

The Kikai caldera volcano located under water in East China Sea is one of the most gigantic calderas in southern Kyushu. At the caldera, a violent eruption occurred from the submarine vent, at ca. 70-80 ka. The eruption is interpreted to have been phreatomagmatic throughout. Each eruptive phase of the eruption sequence generated its own characteristic deposits. The sequence of the events can be summarized as fallows ; (1) a small phreatomagmatic eruption, which generated the fine grained ash including accretionary lapilli, (2) the catastrophic pyroclastic-flow eruption, which formed a large-scale pyroclastic flow (the Nagase pyroclastic flow), two pyroclastic surges (Nishinoomote-1 member : Ns-1, Nishinoomote-3 member : Ns-3), and a wide-spread co-ignimbrite ash fall (Nishinoomote-2 member : Ns-2).The Nagase pyroclastic flow came down from the rim of the caldera, and entered the sea. Then, the flow body, which included a large amount of large pumice blocks and heavy lithic fragments, was disintegrated as gas-particle flow by violent phreatomagmatic explosions, or continued subaqueously as water-supported mass flow. Dilute and fine-particle-rich pyroclastic surges, probably with a density much less than that of water, 1.0 g/cm3, generated off the top or head of subaerial Nagase pyroclastic flow. They could cross on the smooth surface of the sea, becoming water-cooled, vaporish and depleted in large clasts which dropped into the sea. Eventually, the cool and wet pyroclastic surges attacked the islands around the caldera, and deposited as Ns-1 and Ns-3.Ns-2 co-ignimbrite ash fall, composing of glass shards were generated from the upper convective part of the eruption column of the Nagase pyroclastic flow. Included accretionary lapilli indicate that the eruption column was very moisture because of much sea water flash-out subaerially for very violent explosions from the submarine vent. Ns-2 is probably correlated with the Kikai-Tozurahara ash which was found in central Japan more than 500 km off the source.

著者

深畑 幸俊 大橋 聖和 高田 陽一郎 田中 明子

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.128, no.5, pp.685-687, 2019-10-25 (Released:2019-11-15)

参考文献数

9

被引用文献数

2

著者

米倉 伸之

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.77, no.1, pp.1-23, 1968-02-25 (Released:2009-11-12)

参考文献数

34

被引用文献数

14 11

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The Kii peninsula, located on the Pacific coast of central Honshu, is fringed with coastal terraces in its southern part, while its east and west coast are characterized by ria shorelines. The purposes of this paper are to clarify coastal development of the peninsula, especially the history of vertical changes in sea level in its coastal region, and secondly, to examine the relation between the mode of Quaternary crustal movement (especially its vertical component) and recent crustal movement associated with contemporary seismic activity.Coastal terraces and an interpretation of their developmentCoastal terraces, developing along the southern coast of the Kii peninsula (Fig. 2), are mostly rocky abraded terraces covered with thin marine beds. In the northern part of the east coast (north of Shingu) and at the mouths of some rivers, however, some marine terraces are composed of marine sediments overlying fluvial beds. The coastal terraces are classified into two levels of the high and low terraces in the surroundings of Shingu, where they are typically developing (Fig. 4). Both levels of the terraces are further subdivided into some sublevels which are dentoted by H1, H2, H3 and H4 in the high terraces and L1, L2 and L3 in the low terraces respectively in the descending order. The height of each sublevels at Shingu are 125, 113, 95, 61, 49 and 39 meters above sea level. The highest terraces H1 are dissected into narrow hill ridges, overlaid by round gravel beds more than 20 meters thick. The H2, H3 and H4 terraces are rocky abraded ones. The most extensively developing terraces Li are composed of marine sediments underlaid by fluvial beds more than 40 meters in thickness. The L2 and L3 terraces are marine or fluvial terraces which have been formed cutting down the L1 terraces. Alluvial plains (denoted by A) do not so extensively develop along the coast, except at the mouths of the rivers. Judging from some boring data, alluvial formations at the mouths of the rivers are more than 30 meters thick (Fig. 3). From these facts it is concluded that the Hi and Li terraces and alluvial plains are depositional surfaces composed of thick marine and fluvial deposits, which are filling submerged fluvial valleys and, therefore, that the coastal region, being interrupted by temporary submergence, has been emerged in precess of the formation of the coastal terraces. The other terraces H2, H3, H4, L2 and L3 have no feature indicating submergence and, therefore, are considered to have been formed in process of emergence. Judging from the thickness of deposits, amplitude of submergence during the later two periods is considered to be greater than that during the previous period.As to the process of formation of alluvial plains, rapid submergence of this period is regarded in another regions as being largely due to eustatic rise in sea level caused by world deglaciation from the results of the researches on submerged topography, marine topography, succession of alluvial formations, absolute age determination of alluvial marine beds, climatic changes and etc. The process of formation of alluvial plains in the Kii peninsula is inferred to be the same as in another regions from the submerged fluvial valleys and the thickness of alluvial formation and, therefore, the submergence during the last period was caused by eustatic rise in sea level.

著者

磯崎 行雄

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.108, no.5, pp.643-649, 1999-10-25 (Released:2009-11-12)

参考文献数

6

著者

田村 芳彦

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.4, pp.567-584, 2011-08-25 (Released:2011-11-10)

参考文献数

73

被引用文献数

2 4

---

The tectonic setting of arc-arc collision and arc accretion in the Izu-collision zone is similar to that of the Archean orogenic belts (e.g., Taira et al., 1992). Understanding the petrological processes of granite formation in the Izu-collision zone, where geodynamic information is not modified by polyphase deformation and metamorphism, may contribute to an understanding of ancient orogenic belts, especially those related to collisional settings. The Pacific plate began subducting the Philippine Sea plate about 50 million years ago to produce the currently active Izu–Bonin–Mariana (IBM) arc. The collision between the northern IBM arc system and the Honshu arc of the Eurasia plate has been occurring since the middle Miocene (ca. 15 Ma) as a consequence of the northwestward migration of the Philippine Sea plate (e.g., Yamazaki et al., 2010). Neogene granite plutons are widely exhumed by tectonic uplifts associated with arc collision. Seismic imaging suggests that most of the present Izu-Bonin arc crust was created in the Eo-Oligocene (Kodaira et al., 2008; Kodaira et al., 2010). However, remnants of this older crust have not been found in the Izu collision zone. Tamura et al. (2010) integrated new geochemical results with recent geophysical imaging of the arc and concluded that Miocene plutonic rocks in the Izu collision zone are from the Eocene–Oligocene middle crust, which was partially melted, remobilized, and rejuvenated during the collision. Moreover, (1) the mafic arc lower crust is missing at the collision zone (Kitamura et al., 2003) and (2) the aseismic Philippine Sea plate, which is subducted at depths of 130-140 km without evidence of a tear or other gap, has been detected even beneath areas 120 km NW of the collision zone (Nakajima et al., 2009). These lines of evidence suggest that the down-dragged middle crust would partially melt and coalesce in the upper plate, but the mafic (high in iron and magnesium) lower crust would not melt and subduct into the deep mantle, resulting in delamination and separation of the middle crust from the lower crust. Both processes are inevitable at the collision and are necessary to yield continental crust. Thus, it is suggested that collisional orogeny plays an important role in the genesis of continental crust.

著者

日本地学史編纂委員会 東京地学協会

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.127, no.6, pp.835-860, 2018-12-25 (Released:2019-01-30)

参考文献数

260

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The development of geomorphology, human geography, history and methodology of geography, regional geography, and geographic education in Japan from 1945 to 1965 are described. Research objectives and methodologies of geomorphology diversified during this period. A series of natural disasters triggered by earthquakes and typhoons raised social demands for disaster prevention and national land-use management. Full-scale geomorphic studies, fused with geology and engineering, started. Historical geomorphology of lowland plains and process geomorphology began to develop, adding to traditional descriptive geomorphology. The Research Institute for Natural Resources and the Geographical Survey Institute contributed to the postwar reconstruction of geomorphology. Aerial photo interpretation and quantitative land surface analyses developed. A hierarchical landform classification for lowland plains was established and applied to many plains in Japan and developing countries, in order to predict areas subject to flooding and land use planning. The postwar education system increased the number of physical geographers. They contributed to the land classification of Japan as a whole and increased interest in Quaternary environmental changes such as climate and sea level changes, as well as crustal movements, which have produced landform diversity. In 1956, they established the Japan Association for Quaternary Research in cooperation with geologists, anthropologists, and archaeologists. Human geographical research in postwar Japan was far more active and diverse than in the prewar years. This was partly the result of an increase in academic posts devoted to human geography in relation to curriculum reforms in secondary and higher education. Initially, settlement geography was a major field of study. Subsequently, historical geography and economic geography were gradually popularized with the establishment of specialized academic societies, which were dedicated to both fields of study. Among the newly emerging fields were urban, social, and cultural geography. The history and methodology of geography were viewed as overarching fields connected to both physical and human geography. Despite ongoing diversification within geographical research, various topics in these fields were addressed by Japanese geographers. This reflected long-lasting debates concerning the disciplinary identity of geography itself. Regional geography and geographic education concerned both physical and human geography. These research fields were invigorated because of the relative importance of geography in Japan's secondary and higher education systems up to the early 1960s.

著者

岩田 貴樹 吉田 圭佑 深畑 幸俊

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.128, no.5, pp.797-811, 2019-10-25 (Released:2019-11-15)

参考文献数

49

被引用文献数

10

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In order to understand crustal dynamics, including the occurrence of earthquakes and the development of mountain ranges, it is important to estimate the stress state in the Earth's crust from observed data. This paper reviews stress tensor inversion techniques using seismological data. The techniques were originally applied to a dataset of slip orientations taken from focal mechanisms. Subsequently, other techniques, which use P wave first-motion polarities or centroid moment tensor (CMT) solutions, were developed. This paper clarifies the principles and basic hypotheses, on which each technique is built. In the techniques using focal mechanisms and P wave first-motion data, the Wallace–Bott hypothesis that a fault slips in the direction of maximum resolved shear stress plays the principal role; basically, we search for a stress state that satisfies observed data on the basis of the Wallace–Bott hypothesis. On the other hand, the stress inversion technique using CMT data is not based on the Wallace–Bott hypothesis; instead, it is assumed that stress released by earthquakes is proportional to the stress tensor in the region surrounding the hypocenter. The characteristics and advantages of these techniques are also compared from physical and pragmatic viewpoints. It would be valuable to further improve these techniques, as well as to compare their performance using synthetic and actual data to clarify the differences and advantages of their characteristics in more detail.

著者

高木 圭介 青池 寛 小山 真人

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.102, no.3, pp.252-263, 1993-06-25 (Released:2010-10-13)

参考文献数

42

被引用文献数

2 3

---

A synthesis of geological, geomorphological, and petrological data was made to reconstruct the tectonic evolution of the collision zone between the Honshu and Izu-Bonin Arcs during the middle to late Miocene time. The collision zone is composed of four allochthonous terranes, which are overlaid by syn-collisional trough-filling deposits. The four terranes, Izu, Tanzawa, Misaka, and Koma Terranes, were originated in the Izu-Bonin volcanic arc and have in turn collided with and accreted into the Honshu Arc at about 1, 5-3, 11, and 15 Ma, respectively. The geomorphology of the northern part of the Izu-Bonin Arc is characterized by two N-S trending ridges, Shichito-Iwojima and Nishi-Shichito Ridges, and Nishinoshima Trough between the two ridges. We interpret the Nishi-Shichito Ridge as a remnant volcanic arc of early Miocene age. The Nishi-Shichito Ridge was left by backarc rifting, which occurred between the Nishi-Shichito and Shichito-Iwojima Ridges during 15-10 Ma. The backarc rifting resulted in the increase of downdip angle of the Pacific plate slab and the eastward migration of the Izu-Bonin volcanic front. The rifting also generated along-arc compressional strain, which caused the intraarc deformation of the Shichito-Iwojima Ridge at about 10 Ma. This interpretation well explains the geologic history of each allochthonous terrane in the collision zone between the Honshu and Izu-Bonin Arcs as well as the present distribution of the allochthonous terranes.

著者

安藤 寿男

出版者

Tokyo Geographical Society

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.99, no.3, pp.247-262, 1990-06-25 (Released:2009-11-12)

参考文献数

49

被引用文献数

1

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The depositional sequence concept was established in newly developed sequence stratigraphy, as an unconformity-bounded stratigraphic unit formed during one complete sea-level cycle. This paper reviews general meanings of “sequence”, the definition of depositional sequences, their hierarchial patterns and recognition, and sequence boundaries problems, from a viewpoint of sedimentary geology based on outcrops and bore-hole samples.Though the word, “sequence” has many meanings generally applied to successive geologic events and processes in chronologic order, a depositional sequence is defined in a special sense, as “a relatively conformable succession of genetically related strata bounded at its top and base by unconformities and their correlative conformities”. The depositional sequence as one of hierarchial transgressive and regressive units (T-R units), has the first- to forth-order operational units, that is, the megasequence, supersequence, sequence and parasequence in descending order. A sequence boundary with a significant hiatus (=unconformity) is formed by subaerial exposure, concurrent subaerial erosion and partly submarine erosion during eustatic falls or low-stand sea level.The latter half of this paper emphasizes the difference between sequence boundaries and ravinement surfaces. The ravinement surface formed as one of diastems or “transgressive surfaces”, is an erosional surface by shoreface retreat during the following transgression after a sea-level fall. In general, it is lithologically more distinct than the underlying sequence boundary. The right recognition of the difference leads correct reconstructions of sedimentary history.