Testing corrections for paleomagnetic inclination error in sedimentary rocks: A comparative approach

Abstract

Paleomagnetic inclinations in sedimentary formations are frequently suspected of being too shallow. Recognition and correction of shallow bias is therefore critical for paleogeographical reconstructions. This paper tests the reliability of the elongation/inclination (E/I) correction method in several ways. First we consider the E/I trends predicted by various PSV models. We explored the role of sample size on the reliability of the E/I estimates and found that for data sets smaller than ∼100-150, the results were less reliable. The Giant Gaussian Process-type paleosecular variation models were all constrained by paleomagnetic data from lava flows of the last five million years. Therefore, to test whether the method can be used in more ancient times, we compare model predictions of E/I trends with observations from five Large Igneous Provinces since the early Cretaceous (Yemen, Kerguelen, Faroe Islands, Deccan and Paraná basalts). All data are consistent at the 95% level of confidence with the E/I trends predicted by the paleosecular variation models. The Paraná data set also illustrated the effect of unrecognized tilting and combining data over a large latitudinal spread on the E/I estimates underscoring the necessity of adhering to the two principle assumptions of the method. Then we discuss the geological implications of various applications of the E/I method. In general the E/I corrected data are more consistent with data from contemporaneous lavas, with predictions from the well constrained synthetic apparent polar wander paths, and other geological constraints. Finally, we compare the E/I corrections with corrections from an entirely different method of inclination correction: the anisotropy of remanence method of Jackson et al.

A new grand mean palaeomagnetic pole for the 1.11 Ga Umkondo large igneous province with implications for palaeogeography and the geomagnetic field

“…Statistical secular variation models predict a relationship wherein elongation is higher at lower inclination (Tauxe et al (2008); Fig. 5).…”

“…5). It is preferable to have as many unique readings for the field as possible to determine elongation (Tauxe et al, 2008). According to our compilation, 49 VGPs are available for this analysis (applying the α 95 < 15°filter) and hopefully more can be added in the future to make the estimate more robust.…”

“…3) ). According to our compilation, 49 VGPs are available for this analysis (applying the α 95 < 15°filter) and hopefully more can be added in the future to make the estimate more robust.The uncertainty of the elongation determination using the current dataset can be estimated through a bootstrap method as described in Tauxe et al (2008). Through this analysis, we find an elongation value of 2.7 that corresponds with the predicted elongation/inclination behavior of the TK03.GAD model, developed by Tauxe and Kent (2004) to represent the secular variation of a time-averaged geocentric axial dipole (GAD) field, with the caveat that the 95% bootstrapped confidence bounds are large, as they are for data from the other LIPs that are compiled in Fig.…”

Rotation history of Chios Island, Greece since the Middle Miocene

“…The average direction and cones of confidence were determined using Fisher (1953) statistics applied on virtual geomagnetic poles (VGP), because these are more Fisherian (i.e. a Gaussian dispersion on a sphere) than directions, which have a (latitude dependent) elongated distribution (Tauxe and Kent, 2004;Tauxe et al, 2008;Deenen et al, submitted for publication). Errors in declination and inclination are given separately, as Dx and Ix, following Butler (1992) and Deenen et al (submitted for publication) (Table 1).…”

The Magnetic Field of Planet Earth

“…Gilder et al 2003). Elegant methods developed by Kodama and Sun (1992) and Tauxe and Kent (2004) to detect and correct for such inclination flattening tend to confirm this interpretation (Tauxe 2005;Tauxe et al 2008). But it should be emphasized that no such explanation can account for shallow inclinations observed in igneous rocks (e.g.…”