818 research outputs found

    Tectonostratigraphic Terranes of the Circum‐Pacific Region

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95212/1/eost7043.pd

    Paleomagnetic evidence for crustal and thin‐skinned rotations in the European Hercynides

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94849/1/grl3086.pd

    Too-low magnetic inclinations in central Asia: an indication of a long-term Tertiary non-dipole field?

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72802/1/j.1365-3121.2001.00383.x.pd

    Drilling-induced remanence in carbonate rocks: occurrence, stability and grain-size dependence

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    A strong grouping of the directions of natural remanent magnetization in a collection of Ordovician limestones and dolomites, prior to correction for the in situ orientation of the samples, led us to suspect the presence of a substantial spurious magnetization acquired during sample collection and preparation. A close correspondence between the directions of the remanence vectors and the direction of the ambient magnetic field during sawing and drilling of the samples suggested that the remanence was dominated by a component acquired during cutting of the samples. Ten specimens of the Camp Nelson Limestone and Shakopee Dolomite were demagnetized to 100 mT, given an anhysteretic remanence along their axes, and then sawed again. A substantial magnetization parallel to the ambient field during cutting was acquired by all of the specimens, and the resultant directions deviated by 7-70d from the direction of the anhysteretic magnetization. Stepwise alternating-field and thermal cleaning to 60 mT and 400dC respectively failed to remove preferentially the cutting-induced magnetic contamination. Since the fraction of magnetite grains cut during drilling and sawing must be a linear function of grain size, modified Lowrie-Fuller tests were carried out and the results are interpreted to indicate the presence of a multidomain magnetite fraction in the Shakopee Dolomite, Camp Nelson Limestone and Oregon Dolomite. Ratios of initial to anhysteretic susceptibility ( X / X ARM) correlate well with the angular deviation of magnetic directions produced by sawing. This indicates that acquisition of drilling-induced remanence is a function of magnetite grain size, compatible with the notion that the drilling-induced component resides in large magnetite grains which have been cut.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72460/1/j.1365-246X.1985.tb01351.x.pd

    Fennoscandia Paleomagnetics Meeting

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95029/1/eost8757.pd

    A short note on early Cambrian palaeomagnetism from Normandy, France

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72870/1/j.1365-246X.1982.tb06975.x.pd

    Global paleopoles

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95147/1/eost7942.pd

    Ordovician paleomagnetism of eastern Yunnan, China

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95476/1/grl4830.pd

    The reliability of paleomagnetic data

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    A set of seven reliability criteria has been applied to a previously published Phanerozoic paleopole database for Europe and North America and a Late Precambrian data set for Africa. A quality factor (0 [les] Q [les] 7) is assigned to a result, based on the number of criteria satisfied. Three criteria, dealing with age reliability, structural control and laboratory demagnetization analysis are deemed the most important; for the Phanerozoic results these are satisfied by a large majority of the results, whereas for the majority (up to 80%) of the African Late Precambrian results such criteria are not met. Criteria based on tests that constrain the age of the magnetization, such as those dealing with folds, conglomerates, contacts or reversals, enhance the reliability of a result; for the Phanerozoic, they are generally satisfied by about one third of the data, but for the Precambrian only a few results incorporate such tests.The assertion is made in this study that these criteria indeed qualitatively describe the reliability of results in broad terms, so that a data set satisfying on average most of the criteria (Q [ges] 4) can be described as more robust than a data set with average Q = 2. Statistical evaluations illustrate the difference in robustness of paleopole data sets between the well-studied Phanerozoic Era and the much more uncertain Late Precambrian.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28314/1/0000070.pd

    Paleomagnetism of the Dunn Point Formation (Nova Scotia): High paleolatitudes for the Avalon Terrane in the Late Ordovician

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95265/1/grl2910.pd
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