The Journal of the Geological Society of Japan
Online ISSN : 1349-9963
Print ISSN : 0016-7630
ISSN-L : 0016-7630
Volume 54 , Issue 631-633
Showing 1-5 articles out of 5 articles from the selected issue
  • Keiichi OMORI
    1948 Volume 54 Issue 631-633 Pages 33-38
    Published: July 20, 1948
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    The following work was undertaken by the writer to ascertain th ecause of the colours of pearl., While several investigators have studied this problems, their studies have largely been based on interference or diffraction of liget on sarface of pearl., As a result of the present investigation, quantitative data on interference of light especially by the inner laminae are presented., Whereas the nacreous matter appears homegeneous to the naked eyes, it consists of numerous layers, which may be detected on a plane polished nearly tangential to the surface, as shown in Fig., 2., It was so polished as the thickness or width of laminae appears broader than on the section through a center, as shown in Fig., 1., The intervals between these layers are measured on this figure, by means of a comparator as 1 in table 1, and the true thickness of laminae are calculated as r(diff., ) in the same table., The mean value of thickness thus obtained is 0., 00036mm., When a section of pearl is observed under the polarised microscope, it is obvious that a refractive index of pearl directed parallel to the polariser is nearly same as that of Canada balsam, while that perpendicular to the polariser is higher than that of balsam., The refractive indices of the pearl determined by measureing the minimum deviation angle of the prism made of the pearl, are : α=1., 5300, β=1., 6814, γ=1., 6854, γ-α=0., 1554., From the optical and physical properties of the pearl, associated with the optical orientation a//nβb//nγ and c//nα, which correspond to those of aragonite, it might be said that pearl consists of numerous concentric laminae, composed of radial aggregates or extremely minute aragonite crystals, of which c-axis, is perpendicular to the surface of laminae., When the pearl is ground on the surface with fine-grained carborundum, its colour nearly disappears, while brilliant iridescence alone hardly remains., The colour thus seems to be due to the interference of light by the parallel lam nae near the surface., In Fig., 4 the parallel layers of aragon to separated by extremely thin films of conchlolin are shown., Inc, dental beams of light are reflected at the sarface of the successive layers, each beam being retarded behind its predecessor by 2dnm cosθ=λ/2n, where d is thickness of layer, nm is reflactive index, θ is the angle or refraction, λ is wave-length of light, and n is an even on an odd number., It is obvious by this equation that the interference colours depend on the shickness and the angle of refraction., An instance of calculated results is given in the Table 2., When the light passes through the parallel laminae the interference might be produced by the reflection between the planes of neighboering laminae as shown in Fig., 6., In this case the equation for the interference is 2dn cosθ=λ/2n where θ is the angle of reflection and the calculated results are as shown in Table 3., The pearl seems to owe its colour mainly to the two causes above mentioned., The luster is caused by the reflection of light on the surface and varies according to the nature of the surface.,
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  • Sadakatu TANEDA
    1948 Volume 54 Issue 631-633 Pages 39-40
    Published: July 20, 1948
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    In his previous paper, ("Studies on the volcanoes in Japan - The spreading of the activity" in this Journal, 1948) the writer pointed out that the volcanic activity in Japan spread towards N from S, but in another paper (Jour., Jap., Assoc, Petrol., Min., & Eco., Geol., XXXII, 1944) he had stated that the most volcanoes in Japan had a tendency that the centre of activity (eruption) migrated from W∼N to E∼S., It is apparently incompatible, but these two facts may be interpretated without self-contradiction as follows: 1) The activity in a period of volcanic action of Japan spreads towards N from the initial point of the action., 2) The point of action in a later period migrates towards E from that in the earlier period., 3) Sequently, at a volcano with an active line (fissure) in the E-W direction the centre of eruption migrates towards E from W through the history of the volcanic action, and at a volcano with an active line in the N∼W - S∼E direction it migrates toward S∼E.,
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  • Eiju YATSU, Yanosuke OTUKA
    1948 Volume 54 Issue 631-633 Pages 41-43
    Published: July 20, 1948
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    In this paper, river deposits in the lower course of the Tama are descrilled., The results of measurements offered by us are given in table 1., Fig., 1 shows the relation between grain sizes of the river deposits and the gradient of the river-floor., Fig., 2 shows the distribution curve of φ value represented by a new scheme., The prephitic deposits of the Tama gradually decrease their grain sizes in the uppercourse from Oome to Marukotamagawa, gravels quickly disappear and fine materials are predominated., This quick change of grain size in the deposits of the Tama seems tobe caused by the sea tide., Marukotamagawa is the uppermost locality at which the sea side affects the voice of current of the Tama river., In the last paragraph grain sizes of some Diravial gravels overlain by the Kwanto loam are compared with those of the Tama., Results of this comparison shows negative evidence for the hypothesis of the Cheat Rainly age during the Japanese Quaternary.,
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  • Kiyoshi ASANO
    1948 Volume 54 Issue 631-633 Pages 44-49
    Published: July 20, 1948
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    It was previously reported that the Wakimoto and Shibikawa formations of Oga Peninnania Akita Prefecture, afford the most saitable conditions for the establishment of a standard subdivision of the Jopanese Pliocene of the borderland of the Japan Sea, This extensive region is one of the two large palaeo-zoological provinces distinguished in the Japanese Pliocene deposits., (Jour., Geol., Soc., Japan, Vol., 46(547 & 551), 1939)., Continued research has shown (refer to table) that the massive, bluish gray sandy shale of the Wakimoto formation can be subdivided into zones by means of foraminiferal guide species., The three xones E, D and C are now recognized from the older to the younger, in the Wakimoto formation., The Shibikawa formation, by the same procedure, can be subdivided into the two zones B and A, the former being separated from the latter by a ligniteibed in the lower part of the formation., The E-zone, which is characterized by Globobulimina cf., pacifica CHSHMAN, Uvigerina cf., bifurcata d' ORWIGNY and Cassidulina yabei ASANO & NAKAMURA, is a neritic deposit., In this zone planktonic Globigerinidae are abundant while shallow water foraminifers are seldom found., Bluish gray sandy shale which characterizes this zone is litologically distinguished from the D-zone, which mainly consists of sandstone., D-zone is characterized by abundant Miliolidae and Nonionidae, but no Globigerinidae., The characteristic species is Uvigerina yabei ASANO., This zone was deposited in a sea shallower than that of E-zone., C-zone consists of materials similar to the E-zone, and from the abundant occurrence of Globigerinidae it is evidently a neritic deposit., Although the material and conditions of deposition of this zone is much similar to that of E-zone, the guide species readily serve to distinguish one from the other., Thus, the zones E, D and C were distinguished in the Wakimoto formation at Oibana-zaki, Wakimoto-mura, where the foraminifers are distributed from the lower to upper part of the formation., There appears to be no remarkable change in the lithological character of the sediments in which the zones were distinguished., Among the five zones distinguished with in the Wakimoto and Shibikawa formations, B-zone is most outstanding., It is characterized by such guide species as Gaudryina yabei ASANO, Gaudryna oga ASANO, Polystomellina discorbinoides YAEE & HANZAWA, and Eiphidium yabei ASANO., The majority of these species are evidently restracted to this zone thus rendering easily the disinction of this zone from the others., The sandy shale underlying the lignite bed exposed in the sea-cliff at Anden and hitherto refered to the Shibikawa formation by many authors, corresponds to this zone., The lithological characters of this zone is similar to the sediments of the Wakimoto formation., The sediments above the aforementioned lignite bed consists of loose sandstone., Typical exposures of this loose sandstone of the Shibikawa formation are the sea-criff at Anden, Iriai-mura, and the road cutting at ayazawa and Tominaga both in Wakimoto-mura., This loose andstone which builds up the greater part of the Shibikawa formation is A-zone., A-zone is characterized by Elphidium hanzawai ASANO, a guide species which is very seldom found in any of the other zones., Although A-zone includes the greater part of the Shibikawa formation, further subdivision by means of foraminifers is at present difficult owinug to overwhelming number of living species., The abundant occurrence of Miliolidae, Nonionidae and Polymorphinidae in this zone and indicates that deposition took place in a shallow sea., The five zones A to E, as previously reported can be recognized extensively in the oil-fields of the borderland of the Japan Sea and also in southwestern Hokkaido., However of particular importance is the occurrence of Polystomellina discorlinsides YABE & HANZAWA., The occurrence of this particular fossil from B zone suggests that its corre
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  • KOITI SUZUKI, MINORU HOSONO, KYOSUKE KUBO
    1948 Volume 54 Issue 631-633 Pages 50-55
    Published: July 20, 1948
    Released: April 11, 2008
    JOURNALS FREE ACCESS
    The coal-beainq Tertiary in the area is the Suzuka group which includes two formations, the lower, the Kabuto and the upper, the Akira., TheKabuto formation may be divided into the following members in ascending order: Hudesute conglomerate (300m), Kannonyama complex of conglomerate and sandstone (500m), Hagiwara alternation of sandstone and mudstone (350m+) - Hamaebayama boulder conglomerate (180m?, an especiallized facies in the Hagiwara alternation)., It seems to be deposited in freshwaters as indicated by the occurrence of many freshwater shells and plant leaves in the Hagiwara alternation., Among these shells, two species, Arconaia hosonoi Suzuki et OYAMA and Crislaria kuboi, SUZUKI ET OYAMA are determined., Whereas the Akira formation, which is subdivided into two members, the lower, the Isiyama sandstone and the upper, the Himetani complex of sandstone and mudstone may be marine deposits, because many shallow sea shells such as Volsella akanedaensis (KURODA), Brachidontes n., sp., and Katelysia n., sp., are found from the Himetani member., These fossils indicate most probably the Early Miocene (F1) age of the Suzuka group.,
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