Sedimentological Study of the Iwaki Formation of the Joban Coal Field

The Joban coal field has been studied from the economic and academic points of view by many geologists, paleontologists and sedimentologists. The sedimentological studies on the Iwaki Formation had hitherto been concentrated to the condition of deposition of the coal beds and to the formation of the cyclothems whereas analysis of the rocks deposited in the sedimentary basin of the Iwaki Formation had remained untouched probably because of the difficulty in detail correlation of its laterally variable strata and also to the confusion in distinction from superjacent stratigraphic units. The Iwaki Formation was studied from the sedimentary petrographic side to clarify the characters of its sediments and to reconstruct the sedimentary basin in which it was deposited. The petrographic study was carried out on the conglomerate, sandstone, clay minerals, and on the assemblage, composition and distribution of the different lithofacies in both lateral and vertical sequence, and on the texture of the sediments such as grain size, grain shape and their distributions. From the analyses of the grains and their size distribution, the cumulative frequency curve for sandstone was classified into four types for the Iwaki and one for the superjacent Asagai Formation. Despite the change of the grain size in the sandstone that included much matrix, the distribution curve shows moderately -- poor sorted・fine skewed uniformly, and coincides with Visher\u27s (1969) curve indicating Recent delta-estuary sand. The relationship between sorting and skewness is that all samples belong to the group of river sand clan defined by Friedman (1961). The C-M pattern of the sandstone (Passega, 1957) shows that the samples fall in the R-Q and Q-P segments and therefore, the sedimentary environment may have been a river channel or a braided stream (Bull, 1962). The sandstones are composed of quartz, feldspar, mica, hornblende, pyroxene and other heavy minerals, and beside those minerals, there are also included many rock fragments of sandstone, slate, chert, green schist, porphyritic rocks and volcanic rock. The sandstone components were derived from many provenances. A noteworthy constituent is volcanic rock; under the microscope it is a hornblende-pyroxene andesite, but detail identification of the pyroxene was impossible because the material suffered intense weathering. The volcanics and chert are exotic constituents in the Iwaki Formation. The clay minerals identified by X-ray powder diffraction comprised mostly moutmorillonite, kaolin and chlorite. And in the diffraction peaks, calcite and dolomite are identified in the cementing material. It is an important fact that the diffraction of clinoptilolite of the zeolite group is found in the X-ray analysis. In the analysis of the compositional change in vertical sequence of the sand size minerals quartz and feldspars always occupy 20-30 percent of every samples, the percentage of the volcanic rock content is usually 10 percent but in three horizons its percentage increased. The horizons at which the volcanic rocks increase are observed throughout the area after the deposition of the main coal seam, especially in the post-Tochikubo conglomerate deposits and in the uppermost horizon. The occurrence of clinoptilolite coincides well with the horizons at which the volcanic rock fragments increased. From this fact, the existence of three volcanic activities during deposition of the Iwaki Formation was confirmed. The last volcanic activity found in the uppermost part of the Iwaki Formation seems to serve to separate the Asagai Formation from the Iwaki and to indicate the initial phase of the main marine transgression. From the three periods of volcanic activity the deposition of the Iwaki Formation can be divided into three periods of (I) Early, (II) Middle and (III) Late

Conglomerate of the Karaumedate Formation in the Kitakami Massif, Northeast Japan

The gravels contained in the Karaumedate Formation (Carboniferous) are described and discussed as to depositional environment and stratigraphical value

Sedimentary Petrographic Study of the Quartzose Sandstone of the Tomizawa Formation

The nearly 20 m thick quartzose sandstone developed in the lower part of the Jurassic Tomizawa Formation of the Somanakamura Group constitutes volumetrically more than 70 percent quartz grains and is inferred to have been deposited on an alluvial plain, because of the development of minor cyclothems, evidence of the sedimentary structure, grain size distribution and etcetra. The present study shows that the mineral composition is closely related with the texture, and the latter defines the rank of the sandstone in the classification of sandstone. The quartzose sandstones were classified into the orthoquartzite-subarkose-arkose range, and the majority into the subarkose clan in Folk\u27s classification (1954). These quartzose sandstones, having high mineralogical maturity, are not the product of only the environment of the sedimentary basin, because the weathering of the hinterland must have had great influence. It is reasonable to consider the provenance of the sediments based on the mineral composition in the classification of sandstone, in which should be included the textural parameter for interpretation of the sedimentary environment. Further, the end members of the triangle diagram of the classification of sandstone can be chosen to fit the sedimentary environment to reflect the regional sedimentary environment and tectonism

Multi-institutional retrospective study for the evaluation of ocular function-preservation rates in maxillary sinus squamous cell carcinomas with orbital invasion

Background. This study aimed to evaluate ocular function and survival rates among treatment modalities in patients with maxillary sinus cancer with orbital invasion. Methods. Eighty-seven patients were classified according to the main treatment modality. Ocular function preservation rates and survival rates were evaluated for each therapeutic modality. Results. The 5-year overall survival rate for the en bloc resection, conservative surgery, superselective intra-arterial chemotherapy and radiotherapy (RADPLAT), intra-venous chemoradiotherapy (IV-CRT) was 70%, 35%, 49%, and 31%, respectively. Ocular function preservation rate for each group was 15%, 27%, 30%, and 17%, respectively. In the en bloc resection group, there was no significant difference in the 5-year overall survival rate between patients with orbital exenteration and those without orbital exenteration (72% vs 71%, p=0.9321). Conclusions. The en bloc resection group showed a favorable survival rate, but a low preservation rate. Preservation of orbital contents did not reduce the survival rate