{"@context":"http://iiif.io/api/presentation/2/context.json","@type":"sc:Manifest","@id":"https://iiif.quartexcollections.com/portland/iiif/426f8165-4782-4258-989c-57e56994c547/manifest","label":"The Effects of Noise Due to Random Undetected Tilts and Paleosecu","metadata":[{"label":"Title","value":"The Effects of Noise Due to Random Undetected Tilts and Paleosecular Variation on Regional Paleomagnetic Directions"},{"label":"Collection","value":["Environmental Studies Faculty Publications"]},{"label":"Relation","value":"env"},{"label":"Author","value":"Gary J. Calderone, Robert F. Butler"},{"label":"Journal Title","value":"Journal of Geophysical Research"},{"label":"Abstract","value":"Random tilting of a single paleomagnetic vector produces a distribution of vectors which is not rotationally symmetric about the original vector and therefore not Fisherian. Monte Carlo simulations were performed on two types of vector distributions: (1) distributions of vectors formed by perturbing a single original vector with a Fisher distribution of bedding poles (each defining a tilt correction) and (2) standard Fisher distributions. These simulations demonstrate that inclinations of vectors drawn from both distributions are biased toward shallow inclinations. There is a greater likelihood of statistically “drawing” a vector shallower than the true mean vector than of drawing one that is steeper. The estimated probability increases as a function of angular dispersion and inclination of the true mean vector. Consequently, the interpretation of inclination-only data from either type of distribution is not straightforward, especially when the expected paleolatitude is greater than about 50°. Because of the symmetry of the two distributions, declinations of vectors in each distribution are unbiased. The Fisher mean direction of the distribution of vectors formed by perturbing a single vector with random undetected tilts is biased toward shallow inclinations, but this bias is insignificant for angular dispersions of bedding poles less than 20°. This observation implies that the mean pole calculated from a large set of paleomagnetic directions obtained for coeval rocks over a region will be effectively unbiased by random undetected tilts of those rocks provided the angular dispersion of the undetected tilts is less than about 20°. However, the bias of the mean can be significant for large (>20°) angular dispersion of tilts. The amount of bias of the mean direction maximizes at about 10°–12° in mid-latitude regions but is usually less than 8°. Consequently, large (>12°) inclination discordances are probably not the result of random undetected tilts, even if the angular dispersion of the tilts exceeds 20°."},{"label":"DOI","value":"10.1029/90JB02457"},{"label":"Volume","value":"96"},{"label":"Publication Date","value":"D:03 M:10 Y:1991"},{"label":"Publication Information","value":"Copyright 1991 American Geophysical Union. The original published version of this article may be found at http://dx.doi.org/10.1029/90JB02457."}],"description":"The Effects of Noise Due to Random Undetected Tilts and Paleosecular Variation on Regional Paleomagnetic Directions","sequences":[{"@type":"sc:Sequence","canvases":[{"@id":"https://iiif.quartexcollections.com/portland/iiif/426f8165-4782-4258-989c-57e56994c547/canvas/_1","@type":"sc:Canvas","label":"The Effects of Noise Due to Random Undetected Tilts and 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