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The geologic structure of the Carboniferous Hina Limestone exposed at Hina, near Nariwa, Okayama Prefecture, is described with the aid of subsurface data obtained from boring cores, and the geological age is discussed from the standpoint of brachiopod fauna. The Hina limestone forms a complicated folding structure for the most part overturned towards the south, and is marked off by thrust-faults from the northern non-calcareous Permian rocks and the southern Upper Triassic strata. The axial planes of folding, as well as the thrust-planes, seem to incline steeply in a deeper part and then become nearly horizontal upwards. The writers are inclined to consider that the limestone is not a "Klippe" but a mass squeezed out or injected from the deep-seated autochthonous complex. Brachiopods from the Hina limestone and the neighbouring Shodera limestone are classified into two faunal types: the one is characterized by Spirifer sp. aff. S. besnossovae ABRAMOV, Schizophoria sp. aff. S. re-supinata (MARTIN), Syringothyris sp., etc., of which the first is most predominant, and the other by the abun-dance of Striatifera striata (FISCHER), with Schizophoria sp. aff. S. resupinata (MARTIN), Phricodothyris insolita GEORGE, etc. The former is distributed in the Endothyra zone, the lowest foraminiferal zone of the limestone, and the latter in the overlying Eostaffella—Millerella zone. It may be concluded that the Spirifer sp. aff. S. besnossovae fauna is assigned to the early Visean in age and the Striatifera striata fauna to the late Visean.

The stratigraphy of the Permian Karita formation exposed near Hiroshima City is described and its correlation with the Maizuru group in the Maizuru belt is discussed, with special reference to the stratigraphic relationship among the Lepidolina toriyamai, the Colaniella cf. minima and the Leptodus richthofeni horizon. Paleontological descriptions of some important foraminiferal species are presented as an appendix.

It has well been known that in the Inner Zone of Southwest Japan there are several isolated large masses of the Carboniferous-Permian limestone, surrounded by contem-poraneous thick series of sandstone, shale and chert. An example is in and around Taishaku-dai, a part of the Kibi plateau, Central Chugoku. Two distinctive facies, the central and the marginal, can be recognized in the limestones and the overlying clastic rocks of Taishaku-dai. The stratigraphy is as follows in ascending order. Central facies Dangyokei formation (Endothyra zone), 150 m. thick: Characterized by the predominance of basic volcanic and pyroclastic rocks, with some intercalation of limestone. Eimyoji formation (Millerella, Profusulinella, Fusulinella and Fusulina zones), 150m. thick: Composed exclusively of massive limestone. Uyamano formation (Pseudoschwagerina, Parafusulina, Neoschwagerina and Yabeina zones), 400～500 m. thick: Massive limestone. An unconformity is at the base, and a hiatus, of smaller scale is also inserted between the Parafusulina and Neoschwagerina zones. Oshigatani formation (Yabeina zone), 100～300 m. thick: Massive black shale, containing lenses of limestone. An ill-sorted, heterogeneous conglomerate occurs locally. Marginal facies Lower Idaniyama formation (Endothyra zone), 200m. thick: Chert with intercalation of limestone and basic volcanic rocks. Upper Idaniyama formation (Millerella, Profusulinella and Fusulinella zones), 200～250 m. thick: Chert and limestone repeated in various thickness, often showing a graded bedding as in the Lower Idaniyama. Zenbutsujidani formation (Pseudoschwagerina and Parafusulina zones) and Arita formation (Neoschwagerina and Yabeina zones), 400～500 m. thick: Massive limestone with a small amount of chert. An unconformity is at the base of each formation. Maedani formation (Yabeina zone), 1000 m.± thick: Sandstone and shale in graded alternation, succeeded by thick sandstone with a conglomerate at the top. Small lenses of limestone are included in places, and layers of basic volcanics and acid tuffite are also intercalated. Notabiyama formation: Chert and the succeeding siliceous shale, with intercalation of acid tuffite. The microscopic examination of limestones from more than 600 localities shows that the two facics have their respective suites of rock-types concerning the sedimentary petrographic features. The limestones of the central facies are mostly sparry; oo-sparrudite and -sparite are dominant in Carboniferous and biosparrudite (especially fusuline biosparruditc) in Permian. An autochthonous biolithite is also characteristic of this facies, though the occurrence is rather limited. Most of the Carboniferous limestones of the marginal facies are, on the contrary, micritic; bio-micrudite and -micrite rich in fragments of crinoid, bryozoa etc. are common. In the Permian marginal facies develops a calclithite, which consists of pebbles of contemporaneous limestones as well as those of older ones, cemented by biomicritic matrix. Judging from the distribution of macro- and micro-facies mentioned above, it may be concluded that the central facies represents sediments on reef proper (probably like a table reef) and the marginal facies those on fore-reef slope to near-reef basin. They are combined to form an organic reef complex on the submarine volcanic mound. The facies-development and the sedimentary history arc diagrammatically shown on Plate V.

The weakly metamorphosed Paleozoic rocks distributed in the vicinity of Ibara City, Okayama Prefecture, Southwest Japan, are classified lithostratigraphically as follows. Komachi formation Main part (Km, 1000～4500 m. in approximate thickness): Composed mainly of pelitic rock and basic volcanic and pyroclastic rocks, with subordinate acid pyroclastics. Thin layers of psammitic rock and siliceous rock are intercalated and small lenses of limestone are also included. Upper part (Ku, 400～500 m. thick): Composed almost exclusively of pelitic and psammitic rocks. They are often alternated rhythmically, showing a graded bedding. A conglomerate occurs locally. Sabara formation Main part (Sm, 2000～3000 m. in approximate thickness): Similar in lithofacies to the main part of the Komachi formation, but there is no lens of limestone. Upper part (Su, 700～800 m. thick): Similar to the upper part of the Komachi formation, but the psammitic rock is less developed. From the occurrence of Yabeina shiraiwensis OZAWA the upper part of the Sabara formation can be correlated to the Upper Permian. The main part may possibly range from the Middle to the Lower Permian, though no fossil has yet been found. It is questionable whether the Komachi formation is contemporaneous with or older than the Sabara. Metagabbro-metadiabase and mylonitic granite-felsite, which have been grouped under the name of the Yakuno complex, occur closely associated with basic volcanic and acid volcanic rocks, respectively. These volcano-plutonic associations are considered to be a product of the geosynclinal igneous activity preceding the deposition of flysch facies, and are traceable along the boundary between the Central non-metamorphic zone and the Sangun metamorphic zone. Based on the distribution of metamorphic minerals in basic rocks, the surveyed area is divided into three zones, I, II and III. The zone I is characterized by the assemblage of prehnite-pumpellyite, and is represented by rocks of the Sabara formation. Schistosity is scarcely observed and recrystallization is weak. The zone II is characterized by the assemblage of pumpellyite-actinolite, and is represented by rocks of the Komachi formation. Schistosity and lineation are in general well developed and recrystallization is more advanced. These two zones are probably correlative with the weakly metamorphosed upper part of the Sangun complex. As for the zone III, the assemblage of actinolite-epidote is common, and furthermore, hornblende appears in some cases. This zone occupies the limited areas adjacent to the Cretaceous granite and granodiorite, and therefore is undoubtedly related to the later contact metamorphism. Both the Komachi and Sabara formations take a general strike of E-W direction and dip usually to the north with low to moderate angle. The structure is, however, by no means simple. The Komachi formation exposed in the northern part of the surveyed area is, as a whole, overturned, and is in contact by a tectonic slide with the gently folded Sabara formation on the south.

The late Mesozoic formations developed in the western Chûgoku and northern Kyûshû districts are, in descending order, classified as follows. [Original table is skipped. For more details, please refer to the full text.] Annexing geological maps, profiles, columnar sections and lists of fossils, the writer describes the stratigraphy and structure in each of the several areas where the late Mesozoic formations are well exposed, and thereby summarizes the correlation and geologic evolution of them.

This paper treats of the problems concerning the stratigraphy and fossil faunas of the non-marine late Mesozoic formations developed in the province of West Chugoku and North Kyushu. On the basis of the data from the principal outcropping areas I summarize the stratigraphic classification and correlation of the formations, the distribution of the faunas and the geologic structure. In conclusion I discuss the geologic history of the province. The paleontologic descriptions of some new or important molluscan species are given in the sixth chapter.

As to the Carboniferous and Permian strata in the Inner Zone of Southwest Japan, there is a striking contrast between calcareous and non-calcareous facies. Surrounded by thick series of sandstone and shale (sometimes with chert), large masses of limestone with some schal-stein at the base are developed in several isolated areas. An example is in and around the Taishaku limestone plateau, a part of the Kibi plateau, Central Chugoku. The non-calcareous group distributed to the south of the Taishaku plateau is a northwestern extension of the Yoshii group (YOSHIMURA, 1961), and is divided into the following two parts. Lower formation (more than 800m. thick): Mainly composed of black shale, with rather small amount of sandstone and chert. Thin layers of schalstein are intercalated and a small lens of limestone is included. Upper formation (1500-2000m. thick): Composed of sandstone and shale repeated in various thickness, containing conglomerate, schalstein and limestone as thin layers or lenses. From the fossil evidence, which is however insufficient, this group may range in age from Middle Permian to Upper Permian. The limestone groups ranging from upper Lower Carboniferous to Middle Permian thrust up the Yoshii group from both the northeastern and southwestern sides. The thrust-faults run in a direction of WNW-ESE or NW-SE, and dip generally with a high angle. Dikes of por-phyrite of Cretaceous age outcropping along the thrust planes are cut by the re-acted faults., 今村外治教授退官記念特集号

The weakly metamorphosed Paleozoic rocks distributed in the eastern part of Hiroshima Prefecture are classified as follows in ascending order. Subgroup A (more than 700m. thick): Mainly composed of black slate, with a small amount of sandstone, siliceous rock and geeen rock. Subgroup B (2500-3000m. thick): Characterized by the predominance of green rock of volcanic and pyroclastic origin and, black slate to phyllitic slate. Layers of sandstone and siliceous rock occur at horizons. Subgroup C (1500-2000m. thick): Mainly composed of phyllitic slate, with subordinate schistose sandstone and green rock. Thin layers of siliceous rock and acid lava or tuff are intercalated and lenses of conglomerate and limestone are included. Metagabbro, serpentinite and mylonitic granite. From the occurrence of Yabeina shiraiwensis and its allies the subgroup C may range up to the Upper Permian and is possibly correlated to the main part of the Maizuru group in Western Honshu. Geotectonically the surveyed area belongs to the so-called Sanyo branch of the Sangun metamorphic zone, and the stratigraphy described above seems to correspond to that of some parts of the Sangun metamorphic complex in Chugoku and North Kyushu. The limestones of uppermost Mississippian and Lower Pennsylvanian ages (partly of Middle Permian age) outcrop along the northeastern border of the surveyed area. They are cut off from the subgroup C by a marked thrust-fault., 木野崎吉郎教授退官記念特集号