Pumice Bed Research Articles

^<14>C ages of the Kamou pumice flow and the Younger volcanic ash and pumice beds in the Kagoshima City, Kagoshima Prefecture

^<14>C ages of the Kamou pumice flow and the Younger volcanic ash and pumice beds in the Kagoshima City, Kagoshima Prefecture

The Alteration Sequence of the Ontake Volcanic Ashes

The Ontake pyroclastic fall deposits, which have been accumulated in Pleistocene time, show widespread occurrence in the eastern areas of the Ontake volcano in Honshu. In this study, the weathering sequence of these deposits was given, and it was concluded that the alteration followed the sequence of volcanic ash→allophane→halloysite in the order of progressive alteration.In view of the sedimentary environments, the pyroclastic fall deposits may be divided into water-laid, sea-laid and air-laid sediments.In the case of “Pm I” pumice fall bed which served as a key bed in these pyroclastic fall deposits, the degree of alteration is reflected by the delicate shade of different environmental conditions. That is to say, in air-laid sediment argillization is remakable, where as, in water-laid and sea-laid sediments, the volcanic glasses are usually prevented from conspicuous alteration, and only small amount of allophane is recognized. These facts suggest that the sufficient water supply and the retaining of dead water in the sediments might be essential factors in progressive alteration.In general, during the course of weathering, alkalies and alkaline-earth metals might be removed by slightly acid water. The fact that iron and manganese are concentrated as hydroxide at the base of pumice bed may be explained by more alkaline conditions at this site. Under these physicochemical environments, silica and alumina might be leached out as colloidal forms and precipitate as gels. The usual occurrence of allophane, α-cristobalite and gibbsite in the weathering profile will support this view.The features of alteration mentioned above, may indicate that the hydrogen ion concentration and the redox potential as a function of it, are the dominant factor to controll the mineral species which were formed in the course of weathering of these pyroclastic fall deposits.

Tephrochronogical Study in South Kanto

It is well known that the pyroclastic-fall (tephra) layers are the best key beds for regional geologic chronology. South Kanto is a good field for Quaternary tephrochronology in Japan, since there exists a vast amount of tephra mainly supplied from the two volcanoes, Mt. Hakone and Mt. Fuji to the east, covering upon and interbedding wihtin Quaternary sediments.There exists a considerable number of literature on the tephrochronology around Tokyo and Yokohama about 100 kilometers away from the source volcanoes. However, so many tephra beds there consisting of weathered and yet thinner fine ashes with similar brown loamy appearance make it extremely difficult to discriminate some definite time-markers of tephra.As one goes nearer to the source volcanoes, coarser and thicker tephras are expected. In this connection, the best type field is placed in the Ooiso hills, adjacent to the Hakone volcano, where a great number of time-markers is easily distinguished even to the naked eyes and several Quaternary sediments are developed.In this study, each sheet of time-markers which fell after the marine Shimosueyoshi or Kissawa formation was constructed, is precisely discriminated at the type field, Kissawa, eastern part of the Ooiso hills. And then each is traced and correlated eastward along the main axis of distribution to the environs of Tokyo which have been a standard Quaternary succession in Japan (Fig. 1, 2, 4, Table 1, 2, 3).As the first part of this study, the stratigraphy of tephra and absolute ages of several time-markers are discussed in this paper together with the history of the source volcanoes. Former interpretations as to the development of the volcanoes and the marine terraces in this area would be improved considerably.1) The tephra layers of South Kanto were formerly divided into four groups; Tama, Shimosueyoshi (Kissawa), Musashino, Tachikawa tephras. Time gaps during the accumulation of each group were estimated by soil profiles and unconformable relations to about 10, 000 years or more in length. But few data concerning large breaks of tephra falls are found at every boundary in the Ooiso hills and its neighbourhood. A buried soil profile and unconformity are inferred not to indicate a great stratigraphic hiatus but possibly to show a slow accumulation and to be apparent features revealed in the air-laid tephra deposits upon slopes and at the scarps of terraces. In addition, some absolute ages measured by Carbon-14 and Fission track datings indicate that the tephra was supplied rather successively through the late Quaternary (Fig. 10). The longest break of tephra accumulation might be less than several thousand years.2) The Younger tephra groups consisting of the Musashino and the Tachikawa tephra are roughly estimated to have successively accumulated from about 60, 000 years to about 10, 000 years B. P. This estimation is based upon the Fission track age of the Tokyo pumice (TP) and the C-14 ages of the several horizons of the Tachikawa loam (Fig. 10). And the underlying Shimosueyoshi or Kissawa tephra layers are estimated to have successively fallen from about 130, 000 or 120, 000 years B. P. to about 60, 000 years B. P. based upon the Fission track datings of obsidian and zircon included in the several pumice beds (Fig. 10). This result seems to coincide the stratigraphic facts that the total volume of the Shimosueyoshi tephra is about the same as that of the Younger one (Fig. 2) and that some short stratigraphic hiatuses are found at several horizons such as the boundaries of the three subgroups (K1; the lower Kissawa tephras, Km; the middle Kissawa tephras, Ku; the upper Kissawa tephras, Fig. 6A, B). The above age of the lower limit of the Shimosueyoshi tephra layers must suggest that the Shimosueyoshi transgression was dated back to the past a little older than the former concept.

Lithic Artifact-Bearing Layers in the Kanto Loam in North Kanto, Japan

Since the first finding of the famous Iwajuku site, many Preceramic remains have been collected from various places in North Kanto districts, Japan. All these remains are discovered in the “Kanto Loam” which consists mainly of Late Pleistocene tephra layers, and their stratigraphical positions are mostly well documental. Today, as the result of archaeological and geological researches, most of these remains are considered to be the Late-Palaeolithic.This paper deals with some stratigraphical descriptions and discussions on the so-called Early Palaeolithic layers which some archaeologists (Serizawa: 1970 etc.) have recently reported to have found in the lower part of the Kanto Loam at Hoshino, Iwajuku and other sites in the North Kanto.The tephro-stratigraphic positions of the layers at there Preceramic sites are shown in Fig. 9 in the text.Stratigraphically is out of question, that the so-called artifacts were discovered from the deposits evidently below the Hassaki pumice bed (HP, 40, 500±3, 500 years B.P.). According to Serizawa's definition that the culture prior to 30, 000 years B.P. in the Early Palaeolithic, the so-called artifacts belong to the Early Palaeolithic. It is very doubtful, however, whether the specimens which those archaeologists believe to be the Early Palaeolithic are actually artifacts or not. They may rather be regarded as mere clastic breccias which were formed by natural agencies in relation to talus, earthflow or volcanic mudflow depositions.Therefore, it is very precarious to assume that these specimens are the Early Palaeolithic artifacts without taking into goodaccount of the complicated geological and geomorphological factors at each site.

Occurrence of imogolite as gel film in the pumice and scoria deds of western and central Honshu and Hokkaido

Abstract Since its first discovery in 1962 (24, 25), imogolite has been known to occur widely in ando-sols from subfrigid to temperate to tropical regions(1, 2, 3, 6, 7, 9, 14) and, peculiarly as gel films, in certain weathered pumice beds of Japan (11, 23). Its morphology and chemical and mineralogical properties have been investigated fairly well and the investigations have reached the 'stage where its structural models can be hypothesized (13, 16, 19, 20, 26). Relatively little attention has been paid, however, to the mechanism of its formation and to its genetic relationship to other clay minerals(18). Elucidation of these points will be very important in establishing imogolite as a member of weathering sequence in soils, and for this to be done will be needed much more extensive study of its distribution, clay mineral suits associated, environmental conditions in soils, etc.

Identification of imogolite in the filmy gel materials in the imaichi and shichihonzakura purlice beds

Abstract In this paper are described the properties of filmy gel substances occurring in the Imaichi (Imaichi-tsuchi) and Shichihonzakura (formerly called Jobukanuma-tsuchi (2,5)) pumice beds. The properties of such filmy materials from the Kanuma (Kanuma-tsuchi) , Imaichi, and Kitakami pumice beds have been described by many investigators (1,8, 9, 10,12, 13, 14, 15, 19, ). KANNO et al. (9) concluded that they were a mixture of poorly crystalline montmorillonite, allophane, and free sesquioxides. However, the presence of montmorillonite as an important constituent has been disproved by MIYAUCHIA nd AOMINE (12), ho concluded that the gel films from the Kitakami and Kanuma pumice beds consist principally of imogolite.

THE DEVELOPMENT OF MT. FUJI AND MT. HAKONE VOLCANOES ANALYSED FROM THE TEPHROCHRONOLOGICAL STUDY IN THE OOISO HILLS

Mt. Fuji and Mt. Hakone volcanoes lie in the south-west of the Kanto plain and supplied a vast amount of tephras (pyroclastic-fall deposits) through late Quaternary times. The tephras deposited are thicker near the volcanoes and are considered as useful key beds for analysing the history of the volcanoes and the development of terraces. The present paper is devoted primarily to a study of the history of the volcanic activities of Mt. Fuji and Mt. Hakone from the tephrochronological study in the Ooiso hills, where abundant tephra layers and Quaternary sediments are found. In the first place, the most important key bed, “Tokyo pumice”, about which we have as yet very little information in the studied area, has been discovered as a conspicuous pumice bed accompanied with the younger pumice flow deposit of Mt. Hakone volcano. As the Tokyo pumice is a useful horizon marker of the lower Musashino loam formation, the younger pumice flow deposit is placed stratlgraphlcally in this horizon, which is different from those which were reported before. In the next place, the Pleistocene tephra layers in the Ooiso hills are divided into three formations ; the Younger loam, the Kissawa loam and the Tsuchizawa loam. These results are obtained from the relation between tephras and geomorphic surfaces. An idealized geological section of the north-east of the Ooiso hills is shown in Fig. 7. The Kissawa loam, the Kissawa formation and the Kissawa surface are the new geological names. The latter two may have been formed under a remarkable transgression prior to the Holocene epoch, which can be correlated to the Sangamon interglacial. Fig. 8 shows the relationship between the thickness of a tephra and the geological age. The former is expressed by relative figures measured at a certain distance from the crater along the axis of distribution, because this is considered to represent the total volume of a fall unit which is in turn a function of explosivity of an eruption. The tephras of the two volcanoes are interbedded each other., but can be distinguished from the petrological point of view; those of Mt. Hakone are pumiceous deposits of two pyroxene andesitic compositions, and those of Mt. Fuji are scoriaceous of olivine basalt. As shown in this figure, the following results are to be found.1) The activity of Mt. Fuji started later than that of Mt. Hakone.2) Mt. Fuji successively erupted through the time of late Pleistocene until about the beginning of the Holocene. This period of activity was called the “Older Fuji I” as compared with the period of the “Older Fuji II”, the effluent time producing lava flows, and with the “Younger Fuji” of middle to late Holocene (Machida, 1967).3) The activity of Mt. Hakone volcano continued for a long time gradually decreasing in explosivity. From the precise interpretation, the several periods of activity are recognized; I, II (the Older Somma stage I and II), III (the Younger Somma stage) and IV (the Younger Pumice flow and the Central Cone stages accompanying the caldera depression in the younger stage). Those results are obtained from the correlation between the stratigraphy of tephra and the development of the volcanic edifice. And then it is clear that the three greatest explosions occurred after each long quiescent period of activity shown by the Tsuchizawa pumice, the Kissawa A-pumice and the Tokyo pumice. The volcanic activity became less explosive as well as less frequent in the IV stage, while several central cones were constructed.

ON THE LAND FORM AND TEPHROCHRONOLOGY OF MT. SAMBE, SAN-IN DISTRICT, WESTERN JAPAN

The author intends in this paper to offer some contributions on the chronology of Japanese Pleistocene, of which informative data have been few in San-in District. He made the geomorphological map of Mt. Sambe (Fig. 1), surveyed the volcanic ash beds (Fig. 2), and concluded that the volcanic evolution occurred as follows : 1. Ohda pumice flow, 2. Mt. Hikage lava dome, 3. Ukinuno-ike pumice flow and fall, 4. Mt. Ohira pyroclastic cone, 5. Mt. Sambe lava domes, 6. Shigaku pyroclastic flow. The eruptions of Ohda and Ukinuno-ike pumice flows also scattered the fall deposits of ash and pumice which covered the terraces, sand dunes and mountain slopes on the eastward areas. On the other hand, Mt. Daisen erupted ash and pumice beds, some of which are resemble to those of Mt. Sambe. Both the fall deposits of Mt. Sambe and Daisen are found overlapped each other on the terraces (Nogi terrace etc.) around Matsue City. They are easily identified, for some of them have distinct facies. Through interpreting these ash and pumice beds, the process of eruption can be known, and at the same time, terraces covered by these beds can be correlated with it (Fig. 3). Some of the fall deposits covered the palaeo-sand dunes in San-in District. For instance, volcanic ash contemporaneous to Ohda pumice flow covered Izumo palaeo-sand dunes (central part of Shimane Pref.). Ash and pumice beds of Mt. Daisen covered Tottori palaeo-sand dunes (eastern part of San-in District). In conclusion, the evolutions of Mt. Sambe, Mt. Daisen, palaeo-sand dunes and Nogi terrace can be correlated with each other as shown in Table 1, in which the formation of Nogi terrace was probably done during Riss-Wurm Interglacial Epoch.

Mineralogy of gel-like substance in the pumice bed in Kanuma and Kitakami Districts

Abstract A characteristic gel-like substance has been noticed around weathered pumice grains in the pumice beds of Kanuma near Utsunomiya and of Kitakami, Iwate prefecture. This substance was first studied by SHIOIRI (6) in 1934, and reported as allophane according to its chemical composition, refractive index, and dye-adsorbing nature similar to the colloid of volcanic ash soils of the Onji-type. Recently, KUWANO and MATSUI (5) remarked that the colloidal film in the Kanuma and Imaichi pumice beds diffracted x-rays at about 8 and 33 A, and they presumed that this substance might be an early transitional material from allophane to some crystalline clay minerals. KANNO (2) and KANNO et al. (3) examined this gel-like substance from Imaichi and Kitakami districts precisely by the x-ray diffraction, differential thermal, infrared spectroscopical, electron microscopical, and chemical methods, and they concluded that the substance was a mixture of poorly crystallized montmorillonite, allophane in various weathe...

Geomorphological Study in the Takadate Hills, Miyagi Prefecture

In the course of study of hill landform, it seems necessary to investigate not only the initial surface of the hill which is shown as accordant-height summits and is conceived to indicate a baselevel of erosion in an earlier age, but the processes of destruction or modification from initial surface into the present relief, the processes suggested, in the shapes of present valleys and slopes.In the hilly land shown in Fig. 1, situated to the south of Sendai, there are two levels of accordant-height summits, HI and HII Levels. The Levels cut the Miocene Formation in the major part, and, in the minor part HI Level is underlain with weathered round gravel bed of the middle or lower Pleistocene. Above the summits of HI and HII Levels, protrude some peaks grouped into HI. Theose Levels are surrounded by a lowlying hill surface, HIII originated from the denudation surface formed prior to the fall of Yellow Pumice. Characteristic gentle slopes and shallow valleys were formed over whole area shown in Fig. 1, when the TI terrace formation proceeded. That terrace is correlated to the last low sea level by NAKAGAWA et al. (1960). Those slopes and valleys are in the surface forms continuous not only to TI but to the higher Levels especially to HI and they cut Yellow Pumice Bed, Such landforms, judged from their geological and morphological features, seem to be mainly formed with a kind of mass-movement on the valley-sides. Gentle slopes here may be Cryopediment by WAKO (1963). Through the formation of such geomorphological elements, Coarsetexthred landscape (COTTON, 1963) was arranged over the whole area, later some parts are reduced into Fine-textured landscape (COTTON, op. cit.) through the V-shaped valley formation. The Coarse-textured landscape is preserved better where the local baselevel is high. Throughout those processes, geological structure has continuously influenced the lartdform development and certain tectonic, movements took place even after the formation of TI surface.

On the Obanazawa Pumice Bed

“Obanazawa pumice bed” is extensively distributed in Obanazawa basin and its vicinity along the middle-stream of the Mogami river. This deposit was first described by Prof. Y. Tomita as the deposit under the fluvial agency of the Niu river at the time of the explosion of Funagata volcano (in Ou mountains), at the source of this river.The writers exmained about 160 exposures and made the isopach map of the deposit. From this map, the volume of Obanazawa pumice was roughly estimated 0.19km. The deposit attains a maximum exposed thickness in the western border of its distribution area, namely in the vicinity of Hijiori spa. Further, Obanazawa pumcie bed is found on the surfaces of hill-land and higher-middle terraces (Sabane-Obanazawa surfaces).These observations about the distribution of Obanazawa pumcie and some other evidences indicate that Obanazawa pumcie was deposited as a fallen tephra originated from Hijiori cladera (Dewa range). In the writers' opinion taking the result of pollen analyses and archeological sruvey into consideration, Obanazawa pumice bed belongs to the upper Pleistocene or lowest Holocene age.

Hydro-geological Study of Springs in the North-west Area of Mt. Daisen Volcano

There are 64 springs in this area and they are found in following geologic members: Daisen'tuff-breccia, Nagata pumice bed, Nisiobara tuff-breccia of Daisen pyroclastic group, Tataradoyama andesite, Habeyama andesite, Tubogameyama andesite of Daisen andesite group and alluvium.For attempt to quantitative consideration about spring resource, trial calculations of discharge of spring are computed, and results are as follows:1) Discharge averages of spring in each geologic members belong to 4 class (discharge 1x102-1x101' l/sec).2) Apparent unit area discharges of spring in several geologic members are 103-104 M3/day/KM2. Moreover apparent unit area discharge of spring is ratio total discharge of springs in same geologic member to total area of that member.3) Both discharge average and apparent unit area discharge ranks following order: Spring in Tubogameyama andesite Spring in Nabeyama andesite Spring in Tataradoyama andesite.From above results, the writer conjectures that spring resource in Daisen andesite group is prominent quantitatively than in Daisen pyroclastic group.

The Division of Geographical Plains in the Middle Course Areas of River Kitakami from the view point of Surface-Geology

The writer studied the topography of the middle course area of B. Kitakami of northeasten Japan in 1955, and classified this area into several plains from the view-point of surface geology. They are La, Lb, P1, P2, P3, P4, F plains and alluvial fans and plains.La plain is a depositional plain composed of the clay, silt, sand, gravel, peat layers in its section (total thickness is more than 30 meters).Lb plain is the same as La plain, but is a little lower than La plain and is covered with a laminated pumice bed conformably.So he considers that here had been standing waters, and regression made La plain emerge. After the deposition of the pumice bed, regression took place again and Lb plain emerged.At the stage of standing waters, lateral planation had formed F plain, at the eastern foot of the Ôu Mountain-Range, and the succession of P1, P2, P3, plains lying from the south to the north between R. Koromo and R. Isawa. In these plains the thin bed on the bed rock is composed of silt, sand, gravel, on which the pumice bed is layered in P3 and F plains.So he considers that such surface geology shows that these plains were shaped lateral planation, or “panplanation” of Crickmay, or “Tieferschalten” of H. v. Wisstnann.Morphologically speaking, F plain has the same land form as the pediment or the eroded fan, and P1, P2, P3 plains resemble the rock terraces.As the lower part of P3 plain is the same as Lb plain in its surface geology, he considers that P3 plain was shaped by the braided or the free meandering stream that flowed into the standing waters in the stage of Lb plain by the pedimentation process.It seems that F plain had been shaped at the same time as the formation of P1, P2, P3, plains, judginedg from its height and surface geology.Moreover, he thinks that the regression of the standing waters in the stage of Lb plain took place at the end of the Diluvial age, and it began that the alluvial fans and plains, which contain P plain, were formed by the regression as well as by the slight crustal movement along the eastern border of F plain. So the pumice bed abutting on the alluvial fans or plains had been penecontemporaneously deformed by its cutting.

On copper ore deposit of Kagenosawa mine, Iburi province, Hokkaido. (I)

The Kaaenosawa mine is located about 5km northwest of Horobetsu station, Iburi province, Hokkido. The hollocrystalline rock, intruded into the Neogene formations, is found in the neighbourhood of this mine. Especially, the relationship between this plutonic rock and metallic ore deposit, which has been discussed, is clear at this mine. The geological complex, developed in the adjacent area of this mine, belong to the Neogene Tertiary, various kindes of volcanic, and Quarternary sediments. The Neogene Tertiary consists of the lower green tuff, quartz-diorite intrusived into the former rock (Fg. 3 showing its intruded relation), conglomerate and, upper green tuff in ascending order. The conglomerate is composed chiefy of chert and slate derived from the so-called Palaeozoic, and subordinately of diorite and green tuff derived from the Tertiary member. Its traced distance is very short, the thickness being about 60cm. Covering the Tertiary formations descrived above, the Quarternary sediments and volcanic, are widely developed through the elevated plateau of this district. They are mainly composed of the Noboribetsu mud lava and pumice bed in ascending order. The ore deposits are embraced in the lowei green tuff, diorite and upper green tuff. Especially, the deposits which are now under mining are a vein-like type in the fault zone striking in N 80°E and in the brecciated none of diorite striking N 10°E. On the other hand, the network type deposits, which had produced. the higher trade ore of Au, Ag in the earlier development of these mine, are embraced in the clayed zone of Lower green tuff. Furthermore, the deposits showing the same mineral assemblage as in diorite, also exsist in the upper green tuff, covering the dicrite and the lower green tuff. It is clear, accordingly, that the mineralization began after the deposition of the upper green tuff, and then the ore depcsiton here was. ultimately unrelated to the intrusion of quartz diorite. As covered by the Quarternary rocks, the accurate age of mineralization is unclear, but it is doubtlessly younger than the later Kunnui stage.

Studies of the Kwanto Loam

The patterns of sedimentation, grain size, and roundness, and mineralogical composition of the Kwanto loam in Shimosa terrace land, Chiba prefecture, Japan were studied., The Kwatno loam is stratified upon the sandy gravel bed which lies on the Narita formation, and mainly consists of rock fragments of weathered basic tuff., The Kwanto loam is classified into two groups, the upper and the lower A pumice bed lies about 20 cm above the bottom of the upper Kwanto loam (Fig., 1)., The mean grain size of the upper Kwanto loam by weight percentage is bout 3., 6∼3., 8 Phi in diameter while the lower Kwanto loam is 2., 8∼3., 2 Phi., The variation in grain size in the upper Kwanto loam is far less than in the lower (Table 2)., The frequency polygons in Fig., 3 show the difference between the upper and lower., The roundness in the upper Kwanto loam varies from 0., 20 to 0., 22 while in the lower from 0., 33 to 0., 37 (Fig., 5)., The two loams can be distinguished fairly well by their mineralogical composition., The upper Kwanto loam rich in mafic minerals, such as olivine and pyroxene, while the lower is rich in felsic minerals (Table 3)., From the evidence just mentioned, it may be inferred that the upper Kwanto loam is aeolian while the lower is aqueous, and there is a time interval of sedimentation between these two loams.,