Field evidence shows that the lower Fujina member distributed along the southern side of Shinji Lake and the Furue mudstone member bordering the northern side are obviously contemporaneous and equivalent in their stratigraphic positions., Although both lithologic units consist of very fine-grained sediments, their areas of deposition within the same sedimentary basin are not the same as proved by their contained foraminiferal faunas., The lower Fujina member is characterized by such calcareous foraminiferal genera as, Uvigerina, Cibicides, Cassidulina, and Epistominella., On the other hand, the Furue mudstone member is represented by such arenaceous foraminiferal genera as, Cyclammina, Haplophragmoides, Martinottiella, Goesella, and Plectina., This dissimilar microfauna is quite contrary to what would be expected from a lithologically similar facies., The contrasting microfauna can be explained by referring to the depositional and ecological environments of the two similar lithological units by their contained elements., The lower Fujina member may be regarded to have been deposited in the outer neritic zone and the Furue member in the outer bathyal zone., Structurally the Fujina and Furue members occupy the southern and northern wings of the same syncline., By reconstructing the two members to their original positions and referring them to one sedimentary basin, it becomes evident that the basin configuration must have had a characteristic contour, such as a "graben-trough"., Further data upholding the view of a special environment are now progressively accumulating.,

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The stratigraphy of the Osaka Group in the Senriyama Hills, is summarized in the following table., Groups Formations Members Western Part Eastern Part Characteristics Osaka Basin Terraces Toyonaka Terrace Onohara Terrace Sinodayama Group Sakurai Gravels 10m± Hozumi Gravels 10m± Butunenziyama Fault Onohara Faults J₂ Osaka Group 300m+ Ibaraki Formation 100m+ Mituike Alternations of sands and clays 90m+ Hattyoike Alternations of sands and clays 95m+ Marine clay rich Hattyoike Tuff Azuki Tuff Yamada Tuff The upper part of the Osaka Group I₂∼J₁ Senriyama Formation 200m+ Simakumayama Gravels 70m+ Sinden Sands 147m+ Metasequoia Jugrans megacinerea The lower part of the Osaka Group I₁ Basement Kobe Group

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The geology of Tobishima island, Yamagata Prefecture, which is closely related with the so-called "Green Tuffs" of the oil-field along the Japan Sea Coast, was clarified as follows:1) The stratigraphic succession of the formations in Tobishima island, from the upper to the lower are as follows: Hatimanzaki formation (:320 m, -1- in thickness) : consists mainly of basic black tuff clinao-uncomformity Katsuura formation (100 m., -4- in thickness) : alternation of green Cuff and scoria tuff conformity Arasaki formation (130 m., -I- in thickness) : consists mainly of acidic green tuff(containing ligruite and silicified woods) 2) The intense igneous activity of acidic andesite which consists chiefly of dacite, isrecognized in both the Arasaki and Katsuura formations., An intense activity of basic andesite-basalt which consist chiefly of basalt, is recognized in the Hatimanzaki formation., 3) It appears that the geologic structure of Tobisluiuna island which is fundamentally controlled by the faulted structure of NW-SE din-ection and the folded structure of E-W crend, is closely related with the uplift of the island., The folded structure of E-V7 trend in the island exhibits a striking contrast to the N-Strend of the conterrtporarteous strata in the, eXkita oil-field., 4) From the rock facies, silicified woods, igneous activities and unconformaity observed, It appears that the Arasaki and Katsuura f01'1Il2Lt1O11S may correspond aj'proxurnately t0 tl18Daizima and Nishikurosawa stames, and the Hatimanzaki formation to the Onragawzt stage.,

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The stratigraphic succession of the rocks of the Nakatu district is as follows: (9) Alluvium (8) Kanto volcanic ash (7) Terrace deposite (6) Sioda pumiceous sandstone and mudstone (5) Otuka tuffaceous siltstone (4) Takadabasi sandstone and conglomerate (3) Kanzawa alternation of sandstone and siltstone (2) Kosawa sandstone and conglomerate (1) Kobotoke group Nakatu super-formation 1) Many fossil shells are allochthonous in the Kosawa and Kanzawa formations, but only a few are so in the other formations., 2) The Kosawa, Kanzawa and Takadabasi formations were deposited in the euneritic zones, but the Otuka and Sioda formations were formed in the mesoneritic or subneritic zones., 3) During the deposition of the Nakatu super-formation, the Kurosio current was more predominant than the Oyasio, except at several horizons., 4) At the beginning of the deposition of the Nakatu super-formation, the bottom-current were strong and at the end it became weak., The direction of the current is interpreted as S, SW, W, or WNW.,

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