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Episodes 2005年第3期28卷 197-200页

作者： Kenitiro Suguio alethéea ernandes martins sallun Emilio A. A. Soares Centro de Pós-Graduacāo Pesquisa e Extensāo （CEPPE） Universidade Guarulhos （UnG） Praca Tereza Cristina 01-Guarulhos-SP-Brazil-07023-070 Programa de Pós-Graduacāo em Geologia Sedimentar-Instituto de Geociencias Universidade de Sāo Paulo Rua do Lago 562-Sāo Paulo-SP-Brazil-05508-080 Departamento de Geociencias Universidade Federal do Amazonas Av. Gal. Rodrigo O.J. Ramos 3000 Manaus-AM-Brazil-69077-000

The Quaternary, like the long-abandoned terms Primary, Secondary and Tertiary, is a very ambiguous word, whose chronological meaning is not very well defined. Its usage spread very quickly, perhaps due to its more-or-less close relationship with the human history and with the latest glaciations. However, the oldest of human fossil record, according to recent discoveries in Africa （Djourab Desert in Tchad）, is about 7 million years old, rather than 2 million years as suggested by fossils at OlduvaL Moreover, for some time now, it has been known that the first Quaternary-type glaciations occurred in several regions of the earth between 2.5 and 3 million years ago, that is prior to the Pliocene-Pleistocene limit at 1.81 million years ago, as determined by the GSSP. These facts have led some researchers, mostly from the International Union of Geological Sciences （lUGS）, and from the International Association for Quaternary Research （INQUA）, to suggest changes in the subdivision of the Neocenozoic. Certainly, discussions on this subject will be raised at many scientific meetings in the near future until almost unanimous agreement can be attained. Some additional suggestions are presented here, as a contribution to resolution of these nomenclatorial issues.

关键词：冰河作用化石非洲更新世上新世冰川

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Columnar joints in the Patino Formation sandstones, eastern Paraguay： a dynamic interaction between dyke intrusion, quartz dissolution and cooling-induced fractures

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Episodes 2008年第3期31卷 302-308页

作者： Victor Fernandez Velazquez Paulo Cesar Fonseca Giannini Claudio Riccomini alethea ernandes martins sallun Jorge Hachiro Celso de Barros Gomes Eseola de Artes Ciencias e Humanidades Universidade de Sao Paulo Rua Arlindo Betio 1000 03828-080 Sao Paulo Brasil Instituto de Geociencias Universidade de Sao Paulo Rua do Lago 562 05508-080 Sao Paulo Brasil Insfituto Geolegico Secretaria do Meio Ambiente Av. Miguel Estefano 3900 04301-903 Sao Paulo Brasil.

The Patiho Formation sandstones, which crop out in Aregud neighborhood in eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high pro- portion of syntaxial quartz overgrowth and a porosity originated from different processes, initially by dissolu- tion and later by partial filling and fracturing. Features like the presence of floating grains in the syntaxial cement, the transitional interpenetrative contact between the silica-rich cement and grains as well as the intense fracture porosity are strong indications that the cement has been formed by dissolution and reprecipita- tion of quartz from the framework under the effect of thermal expansion followed by rapid contraction. The increase of the silica-rich cement towards the dyke in association with the orthogonal disposition of the columns relative to dyke walls are indicative that the igneous body may represent the main heat source for the interstitial aqueous solutions previously existing in the sediments. At macroscopic scale, the increasing of inter- nal tensions in the sandstones is responsible for the nucleation of polygons, leading to the individualization of prisms, which are interconnected by a system of joints, formed firstly on isotherm surfaces of low tem- perature and later on successive adjacent planes towards the dyke heat source.

关键词：柱状连接砂岩巴拉圭南美洲动力学

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Evidence of Shock Metamorphism Effects in Allochthonous Breccia Deposits from the Colonia Crater,Sao Paulo,Brazil

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International Journal of Geosciences 2013年第1期4卷 274-282页

作者： Victor F.Velazquez Claudio Riccomini Jose M.Azevedo Sobrinho Mikhaela A.J.S.Pletsch alethea E.martins sallun William sallun Filho Jorge Hachiro Escola de Artes Ciencias e HumanidadesUniversidade de Sao PauloSao PauloBrasil Instituto de Geociencias Universidade de Sao PauloSao PauloBrasil Instituto Geologico Secretaria do Meio AmbienteSao PauloBrasil

The 3.6 km-diameter Colonia impact crater, centred at 2352'03"S and 4642'27"W,?lies 40 km to the south-west of the S?o Paulo city. The structure was formed on the crystalline basement rocks and displays a bowl-shaped with steeper slope near the top that decreases gently toward the centre of the crater. Over recent years were drilled two boreholes inside the crater, which reached a maximum depth of 142 m and 197 m. Geological profile suggests four different lithological associations: 1) unshocked crystalline basement rocks (197 - 140 m);2) fractured/brecciated basement rocks (140 - 110 m);3) polymictic allochthonous breccia deposits (110 - 40 m);and 4) post-impact deposits (40 - 0 m). Petrographic characterisation of the polymictic allochthonous breccia reveals a series of distinctive shock-metamorphic features, including, among others, planar deformation features in quartz, feldspar and mica, ballen silica, granular texture in zircon and melt-bearing impact rocks. The occurrence of melt particles and very high-pressure phase transformation in suevite breccia suggest a shock pressure regime higher than 60 GPa.

关键词： Colonia Crater Polymictic Allochthonous Breccia Shock Metamorphism Effects

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