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Showing 1 to 20 of 195 for “"Precambrian"”.
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Subsurface Precambrian of Saskatchewan
… the basement, and regional geophysical maps, the Precambrian rocks of Saskatchewan which occur beneath the Palaeozoic and later rocks consist of predominantly northtrending belts ot granitic and metamorphic rocks. The rock assemblage found in the covered Precambrian Shield appears to be similar to …
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Paleolimnology of selected Precambrian Shield lakes /
The analysis of fossil diatoms and Mallomonas assemblages in a 2.85 m sediment core revealed that a series of distinct floristic changes have occurred in the development of Found Lake, a small Shield lake in southern Ontario. Climatic and vegetational changes in the lake's watershed were closely …
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The geochemistry of late Precambrian weathering profile northwest Scotland
… an attempt to understand the environment of the Precambrian weathering at Rispond, and compare it with weathering processes taking place at the present time, samples weathered to different degrees have been taken at various distances immediately below the Cambrian Unconformity. These samples have …
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Petrography of Precambrian iron formation, Pembina County, North Dakota
… interlayered with quartz-biotite schist of Precambrian age. The core recovered from the Akra site contained mineral assemblages of the greenschist and amphibolite facies of regional metamorphism, the metamorphic grade increasing with depth. The mineral assemblages of the Hensel core indicate …
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Canadian precambrian iron-formations: ages and trace element compositions,
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1971.
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Organic geochemistry and stable isotope constraints on Precambrian biogeochemical processes
… cycles and the dominant mechanisms present in Precambrian remain heavily debated topics. The events of the Late Proterozoic onset to glaciations and what types of early life existed in the Archean are two of the many provoking topics within the Precambrian. We set out to improve the …
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Sedimentological constraints on Precambrian crustal evolution in northern New Mexico
The Precambrian of northern New Mexico is part of an extensive 1,800 to 1,500 m.y. terrane stretching from Colorado through northern New Mexico into central Arizona. Three lithostratigraphic sequences are present in New Mexico. The oldest consists of 1,760 to 1,720 m.y. metamorphosed bimodal …
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Petrology and structure of the buried Precambrian basement of Colorado, The
Includes bibliographical references.
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The application of radio field intensity measurements to mapping Precambrian geological structures
Thesis (M.S.)--Michigan State University of Agriculture and Applied Science. Dept. of Geology, 1963
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Geochemistry of the Precambrian Iron Formation Near Atlantic City, Fremont County, Wyoming
Made available in DSpace on 2014-12-09T20:34:40Z (GMT). No. of bitstreams: 1 7013450.pdf: 2869166 bytes, checksum: 7a53d89444d766eaf6304f277b0fbeaa (MD5) Previous issue date: 1969
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Improved dating of Canadian Precambrian dikes and a revised polar wandering curve.
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1971.
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K-Metasomatism in Uppermost Precambrian Rocks in West-Central Wisconsin and Southeastern Missouri
K/Ar dating of different size fractions of I/S samples reveals three episodes of illitization in the alteration profiles: 432-424 Ma, 410-383 Ma, and ${\sim}{-}314$ Ma. Rb-Sr and oxygen isotopic data suggest I/S of the 432-424 episode may have formed from the same fluids that formed the …
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Melanges and Glaucophanic Schists of the Mona Complex (Precambrian), Southeast Anglesey, North Wales
Amphibole distribution and zoning patterns suggest metamorphism in a subduction complex above a northwesterly dipping subduction zone. These rocks were among the earliest accreted material and not exposed to the thermal conditions of the mature subduction complex.
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The rheology and dynamics of the Precambrian lithosphere – insights from the British Isles
… the properties, behaviour, and evolution of the Precambrian lithosphere. In Chapter One, I summarise some of the key open questions regarding lithospheric evolution and the development of strength contrasts, and how they will be addressed in this thesis. Chapter Two investigates the feasibility …
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Petrological study of a group of porphyroblastic rocks in the Precambrian of northeastern Alberta
Made available in DSpace on 2014-12-04T19:14:08Z (GMT). No. of bitstreams: 1 6104366.pdf: 6512225 bytes, checksum: 93f52e0933ed7981af614470d49bde45 (MD5) Previous issue date: 1961
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Potassic alteration of Cambrian-Ordovician sandstones and Precambrian basement rocks of the North American midcontinent
… zone, and a lowermost feldspar zone. Uppermost Precambrian basement exhibits potassic alteration similar to the overlying Mt. Simon Sandstone. Sericite in the basement rock was likely formed during the same episode as in the Mt. Simon Sandstone, based on similar $\delta\sp{18}$O values. A K/Ar …
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Kaolinitic weathering zone on Precambrian basement rocks, Red River Valley, eastern North Dakota and northwestern Minnesota
… Project has provided new information on the Precambrian basement of eastern North Dakota and northwestern Minnesota. Basement rocks in this area consist of intermediate to felsic coarse-grained massive or gneissic rocks, and intermediate to mafic metavolcanic and metasedimentary schists. The …
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