457 research outputs found

    Gradational development of slaty cleavage to schistosity -an example from the Iberian Pyrite Belt, Spain-

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    The Iberian Pyrite Belt is an Upper Paleozoic succession which has been divided into the Phyllite-Quartzite Group, the Volcanic-Sliceous Complex and the Culm Group in ascending order from base to the top. The contacts among them are conformable. These Groups are tightly folded and metamorphosed un-der low-grade conditions during Hercynian times. The first stage folds of the Volcanic-Siliceous Complex and the Culm Group are associate with slaty cleavages (S1), while the Phyllite-Quartzite Group is asso-ciate with schistosities (S1). Fold analysis using cleavages and minoe folds has been utilized in the analysis of the stratigraphy. This led to systematic horizontal collection of specimens (pelitic rocks). S1 texture is defined by paralled alignment of secondary platy minerals which tend to grow larger and together, forming zonal domains toward the Phyllite-Quartzite Group. The clay matrices change to recrystallized quartz toward the Phyllite Quartzite Group. Textural modifications are evidenced by gradational changes from slaty cleavages to schistosities. This shows that recrystallization is the important deformation mecha-nism responsible for S1 development. It also reflects that the deformation was contemporaneous with metamorphism

    Microscopic observations of the recent soils: a step for understanding the paleosols

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    The microscopic observations of the recent soil horizons were conducted in Okayama, Japan (moderate climate). The several soil horizons, including two surface (epipedon) and three subsurface horizons, were recognized in the forest, poorly vegetated hill, and riverside around the Okayama University. The umbric epipedon can be segregated from the organic-rich subsurface horizons by the scattered organic materials in thin sections. The ochrich epipedon shows the sandy matrix without any cements and the illuviation of clay minerals. The subsurface horizons identified in the study area are as follows: albic, argillic, and cambic horizons. Each subsurface horizon shows the specific structures in thin sections. The albic horizon is characterized by the absence of the illuviation. The argillic horizon definitely shows the clayey matrix and the illuviation of clay minerals. The primary structures may be retained in the cambic horizon. The microscopic examination of the Miocene paleosols from the Ukan-cho, Okayama, was attempted. By comparing the recent soils, the cambic horizon and spodic horizon, which is characterized by the concentration of sesquioxides, are identified in the paleosols. This attempt suggests that the microscopic observations of the recent soils is a useful guide to understanding the paleosol

    Computations in formal symplectic geometry and characteristic classes of moduli spaces

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    We make explicit computations in the formal symplectic geometry of Kontsevich and determine the Euler characteristics of the three cases, namely commutative, Lie and associative ones, up to certain weights.From these, we obtain some non-triviality results in each case. In particular, we determine the integral Euler characteristics of the outer automorphism groups Out F_n of free groups for all n <= 10 and prove the existence of plenty of rational cohomology classes of odd degrees. We also clarify the relationship of the commutative graph homology with finite type invariants of homology 3-spheres as well as the leaf cohomology classes for transversely symplectic foliations. Furthermore we prove the existence of several new non-trivalent graph homology classes of odd degrees. Based on these computations, we propose a few conjectures and problems on the graph homology and the characteristic classes of the moduli spaces of graphs as well as curves.Comment: 33 pages, final version, to appear in Quantum Topolog

    Holocene environmental and sea-level changes of the Okayama Plain – evidence from peat beds –

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    Quaternary peat beds from bore-hole samples deliver information to reconstruct paleoenvironment. Altitudes of dated non-marine peat beds and marine beds allow to be created a sea-level curve. 4 peat beds (A to D) are identified from the uppermost Pleistocene to Holocene deposits of the Okayama Plain. They thought to be deposited at stable events during sea-level change

    Paleogene talus deposits, Okayama City, Southwest Japan

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    In eastern Chugoku area, Paleogene deposits have not been recognized until fission-track dating of so called "Mountain Gravels" was carried out (Suzuki et al. 1995). Two sedimentation events in Paleogene time (27Ma and 34-35Ma) are inferred by the F-T dating Major lithology of the Paleogene deposits in the study area is graved which is mainly composed of subrounded to rounded cobbles. The "Mountain Gravels" were previously thought to be lower Quaternary deposits. The "Mountain Gravels" is associsted with coal bearing mud, sand, gravel and breccia deposits. The breccia deposits is distributed sporadically between the "Mountain Gravels" and basement rocks. The deposits are mainly composed of poorly sorted breccia and associated granitic sands. It is inferred that the breccia deposits are talus deposits

    The first Japanese word "chishitsu-gaku" for the "geology" was proposed by Genpo Mitsukuri (1799-1863)

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    The first Japanese word "chishitsu-gaku" for the "geology" was proposed by Genpo Mitsukuri, a scientific contributor in the Tokugawa regime in the 19th century, who was born in 1799 in Tsuyama in Western Honshu, Japan and had worked for scientific activities of the Tokugawa government from 1839 to 1863. His major works for the first making of the "chishitsu-gaku" for the "geology" have been presented in this paper, also showing his contribution to Japanese sciences

    Paleoparadoxia from the middle Miocene of Obara, Misaki-cho, Okayama Prefecture, Japan

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     The partially preserved left humerus of the Desmostylia (Mammalia) has been collected from the riverbed in Obara, Misaki-cho, Okayama Prefecture in the western Japan. This specimen can be classified to the genus Paleoparadoxia by the following features: the absence of the supratrochlear foramen; the curved disto-lateral border of the shaft in the antero-posterior view; the medio-laterally expanded flat trochlea of humerus. Moreover, this specimen can be referred to cf. P. media on the basis of its middle-sized dimensions. This is the second occurrence of Palaeoparadoxia from Okayama Prefecture
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