Discovery of Late Jurassic rudist bivalves from the Torinosu-type limestone blocks in the Oriai Formation of the Imaidani Group in the Shirokawa area, Ehime Prefecture, Southwest Japan

The Triassic Taho Formation crops out in Taho, Shirokawa Town, Seiyo City, Ehime Prefecture, Southwest Japan. The formation is newly divided into the Tahogawa and Sakuragatouge members. The Tahogawa Member consists mainly of partly dolomitized light-, dark-, brownish-gray and black bedded limestones, and yields abundant Early to Middle Triassic conodonts, ammonoids, gastropods, bivalves, brachiopods and fish remains. The Sakuragatouge Member is dominated by brownish gray lenticular conglomeratic limestone and massive gray and white limestones that contain Middle to Late Triassic conodonts, gastropods, bivalves, echinoids and fish remains. In the Tahogawa Member, conodont assemblages are composed of 13 genera and 45 species, including three new species: Neospathodus arcus Maekawa sp. nov., Novispathodus shirokawai Maekawa sp. nov., and Nv. tahoensis Maekawa sp. nov. The member is divided into five conodont zones in ascending order: the Ns. dieneri Zone, the Ns. cristagalli Zone, the Nv. ex gr. waageni Zone, the Nv. pingdingshanensis Zone and the Nv. brevissimus Zone. The Nv. ex gr. waageni Zone contains three conodont subzones (the Eurygnathodus costatus Subzone, the Guangxidella bransoni Subzone and the Scythogondolella milleri Subzone), and the Nv. brevissimus Zone includes the Icriospathodus collinsoni Subzone. The conodont biostratigraphy of the member indicates a late Dienerian to early Spathian age, and correlates with that of Tethyan and Panthalassean sections. The Induan-Olenekian boundary is indicated by the first occurrence of Nv. ex gr. waageni. The Smithian-Spathian boundary is immediately below or intercalated within the Nv. pingdingshanensis Zone.

Abstract. Late Early Carboniferous (late Visean) to late Middle Permian (Capitanian) foraminifers have been recovered from limestone blocks and fragments contained in the Tsunemori Formation in Yamaguchi Prefecture, Southwest Japan, which is unconformably overlain by the Upper Triassic Mine Group. An analysis of the Tsunemori fauna shows an almost identical composition with that of the Akiyoshi Limestone Group. The ages of the limestone clasts of the Tsunemori Formation nearly completely coincide with those of the strata of the Akiyoshi Limestone Group. The Akiyoshi Limestone Group is subdivided into 28 foraminiferal zones, and faunal elements corresponding to 24 of these 28 zones are recognized in limestone blocks and fragments of the Tsunemori Formation. Species from the remaining four zones (late Visean Endothyra sp. Zone, the late Moscovian Fusulinella bocki Zone, early Asselian Sphaeroschwagerina fusiformis Zone, and Bolorian Misellina dyhrenfurthi Zone) in the Akiyoshi Limestone Group have not been ...

A late Jurassic carbon-isotope record from the Qiangtang Basin (Tibet), eastern Tethys, and its palaeoceanographic implications

Carbon isotope stratigraphy of the Late Jurassic and earliest Cretaceous was revealed from Torinosu‐type limestone, which was deposited in a shallow‐marine setting in the western Paleo‐Pacific, in Japan. Two sections were examined; the Nakanosawa section of the late Kimmeridgian to early Tithonian age (Fukushima Prefecture, Northeast Japan), and the Furuichi section of the late Kimmeridgian to early Berriasian age (Ehime Prefecture, Southwest Japan). The age‐model was established using Sr isotope ratio and fossil occurrence. The limestone samples have a low Mn/Sr ratio (mostly <0.5) and lack a distinct correlation between δ13C and δ18O, indicating a low degree of diagenetic alteration. Our composite δ13C profile from the two limestone sections shows three stratigraphic correlation points that can be correlated with the profiles of relevant ages from the Alpine Tethyan region: a large‐amplitude fluctuation (the lower upper Kimmeridgian, ∼152 Ma), a positive anomaly (above the Kimmeridgian/Tithonian boundary, ∼150 Ma), and a negative anomaly (the upper lower Tithonian, ∼148 Ma). In addition, we found that δ13C values of the Torinosu‐type limestone are ∼1‰ lower than the Tethyan values in the late Kimmeridgian. This inter‐regional difference in δ13C values is likely to have resulted from a higher productivity and/or an organic burial in the Tethyan region. The difference gradually reduces and disappears in the late Tithonian, where the Tethyan and our δ13C records show similar stable values of 1.5–2.0‰. This isotopic homogenization is probably due to changes in the continental distribution and the global ocean circulation, which propagated the 13C‐depleted signature from the larger Paleo‐Pacific to the smaller Tethys Ocean during this time.

Katayamalite occurs as a fine-grained accessory mineral amounting to 0.3–0.5 percent by volume in the aegirine syenite from Iwagi Islet, Ehime Prefecture, Southwest Japan. It coexists usually with albite, aegirine and pectolite. To the naked eye, katayamalite is white in color and phosphorescent to the ultraviolet rays. Striation white, luster vitreous. Hardness (Mohs) 3.5–4.0. Specific gravity 2.899 (calc), 2.91 (meas.). (001) cleavage is perfect. In thin section it is colorless with strong absorption. α=1.670, β=1.671, γ=1.677, γ−α=0.007, 2V(+)=ca. 32°.Chemical analysis shows SiO2 52.31, TiO2 10.99, Fe2O3 0.29, MnO 0.22, Li2O 3.25, CaO 28.25, Na2O 0.22, K2O 2.89, H2O 1.21, F 0.34, –O=F2 0.14, total 99.83%, corresponding ideally to (K, Na)Li3Ca7(Ti, Fe+3, Mn)2[Si6O18]2(0H, F)2 with Z=4.Katayamalite is triclinic with a0=9.721, b0=16.923, c0=19.942A, α=91.43°, β=104.15°, γ=89.94°, Space group C1. The strongest lines in X-ray powder data are 3.23 (100) (006·0-44), 3.06 (30) (2-43), 2.943 (30) (-3-14·3-11·-153), 2.898 (30) (-2-44·2-42), 2.417 (30) (008), 1.933 (40) (00.10).Katayamalite resembles baratovite (Dusmatov et al., 1975) both structurally and also chemically, but it is distinguished from the latter by the difference in crystal system and unit cell parameters. Dominance of OH over F and lacking of Zr replacing Ti are another chemical features of katayamalite.The name katayamalite is given for the mineralogist, Emeritus Professor Nobuo Katayama.

Gross morphology and internal texture of tufa deposits in Shirokawa Town, Ehime Prefecture, vary due to local environments (including flow condition, substrate topography, and associated biota) within the tufa-bearing stream. Variations in gross morphologies of the tufa deposits include 1) tufa encrusting boulders, 2) plane slope, 3) mound, 4) terraces, and 5) cascade. These types are basically related to variations in the original topography although they share similarities in a local environment of strong water flow which is an essential condition for active tufa deposition. Laminated internal texture, the most striking feature of the Shirokawa tufa, normally develops in tufas colonized by cyanobacteria inhabiting the surface. Regular lamination is most commonly developed along the narrow water passage of the lower stream where strong water flow continues throughout the year. The laminated tufas consist of repetition of dense lighter-colored laminae and porous darker-colored laminae, which correspond to the summer and winter deposits, respectively. The lighter laminae are characterized by thick calcite encrustation on upward-growing filamentous cyanobacteria. The darker laminae also mainly consist of calcite encrustation of cyanobacterial filaments, but the porosity largely remains. The annual rhythm seen in the laminated texture can be explained by seasonal variation in abiotic calcite precipitation rate (large in summer and small in winter) which increases with water temperature, Ca2+ contents, and flow strength. Because of the well-defined chronological constrains, continuous deposits of laminated tufas can be excellent material for reconstructing terrestrial climates.

Bottom environmental changes during the past 200 years in Mishou Bay, Ehime Prefecture, South west Japan

Blocks of cherty rocks and Aptychus Limestone embedded into ophiolite melange south of Avala Gora (Serbia) contain radiolarians of different ages. We distinguished here Late Jurassic (middle Oxfordianearly Tithonian), Middle-Late Jurassic (Bathonian-early Tithonian), and Middle Triassic (early Ladinian) radiolarian assemblages. The respective stratigraphic data suggest that the ophiolite melange was formed after the early Tithonian.

P-264 Bottom environmental changes during the last 150 years in Mishou Bay, Ehime Prefecture, Southwest Japan

Invited] (entry) Granitic magma processes during the Cretaceous flare-ups recorded in Cretaceous plutonic rocks from Kajishima Island, Ehime Prefecture, southwest Japan.

Murakamiite, LiCa2Si3O8(OH), a Li-analogue of pectolite, from the Iwagi Islet, southwest Japan

The effect of nineteenth century reclamation to seafloor environment in Mishou Bay, Ehime Prefecture, Southwest Japan.

Sugilite occurs as an essential mineral amounting to 3–8 percent by volume in aegirine syenite from Iwagi Islet, Ehime Prefecture. It is associated with albite, aegirine, pectolite and a Ca-K-Ti silicate (a still to be identified mineral). Sugilite is light brownish yellow, luster vitreous, streak white. Symmetry hexagonal. Cleavage 0001 weak. Hardness 6–61/2. Specific gravity 2.802 (calc.), 2.74 (meas.).Under the microscope, it is uniaxial negative with e=1.607, ω=1.610, ω−e=0.003, and colorless.Estimated chemical composition is SiO2 71.38, TiO2 0.51, A12O3 2.97, Fe2O3 12.76, FeO 0.19, Li2O 3.14, Na2O 4.37, K2O 3.76, H2O(+) 0.81, H2O(−) 0.12, total 100.01%, corresponding ideally to (K, Na)((H2O), Na)2(Fe3+, Na, Ti, Fe2+)2(Li, Al, Fe3+)3(Si12O30) with Z=2.The unit cell dimensions are a0=10.007(2), c0=14.000(2)A. Space group D26h−P6⁄mcc. X-ray powder data resemble those for sodgianite, milarite, osumilite, merrihueite, roedderite and brannockite.It is clear from the above-cited data that sugilite has milarite-type structure and resembles sodgianite and brannockite in containing lithium in tetrahedral site, but it is distinguished by a high content of ferric iron in 6-coordination.The name is given in honour of the late Professor Ken-ichi Sugi (1901-1948), who first found the occurrence of this mineral with Mr. M. Kutsuna.

Late Silurian halysitid corals from the Okanaro Group in Ehime Prefecture, Southwest Japan

Terrace profiles along rivers based on accurate correlations of terraces and geochronological examination are needed to reveal regional crustal deformation from the distribution of river terrace surfaces. Tephra beds, which are intercalated or cover terrace sediments, are used as beneficial information to correlate terrace surfaces accurately. On the other hand, in cases lacking tephric sediments, the correlation of terrace surfaces is mainly based on geomorphic characteristics, such as degree of dissection, relative elevation, and geologic properties, such as facies of sediments and weathered degree of terrace gravels. A terrace surface correlation based on qualitative indicators may cause uncertainty or variability depending on the criteria defined in each study. In this research, weathered degree of gravels in terrace sediments is introduced as another quantitative indicator to validate or compensate for the terrace surface correlation. The examination process is as follows. The research target is the Hiji-kawa River in western Shikoku, along which many terrace surfaces (P, HH, H, M, and L) are distributed. Few tephric sediments exist in terrace sediments. The 0.6 Ma tephra is intercalated at the upper part of P Surface deposits. 0.3 Ma tephra is intercalated at the upper part of Hf1 Surface deposits. An analysis of volcanic ash grains suggests that M surfaces are covered with Aso-4 tephra (85 to 90 ka). First, the ages of other non-aged-terrace surfaces are estimated based on height differences from aged-terraces. Second, real density values are measured for several gravels collected from 15 stages of terrace sediments. Finally, measured real density values are normalized by measured values of current riverbed gravels. Relative density values (RDV) show a negative correlation with ages of terrace surfaces. The research results suggest that RDV is very useful for estimating the ages of terrace surfaces without tephric sediments. The average uplift rates of the middle stream and downstream along the Hiji-kawa River are calculated to be 0.17-0.18 mm/yr. There are no nick points in the current riverbed slope and the spatial distribution of each terrace surface. These results indicate that there is no local topographic deformation due to faulting and folding around the Hiji-kawa River valley.