Simplification of the anisotropy-based inclination correction technique for magnetite- and haematite-bearing rocks: a case study for the Carboniferous Glenshaw and Mauch Chunk Formations, North America

Abstract

S U M M A R YAn anisotropy-based inclination correction was applied to the Carboniferous Glenshaw Formation from southwestern Pennsylvania. A combination of low-temperature thermal demagnetization followed by alternating field demagnetization isolated a palaeomagnetic remanence direction similar to that previously reported for these rocks. The inclination correction was conducted by fitting the samples' anisotropy of anhysteretic remanence (AAR) to the theoretical correction curves for a magnetite remanence that yielded a remanence individual magnetic particle anisotropy, the a γ factor, equal to 1.86. Direct measurement of individual particle anisotropy in magnetic grain extracts, yielded an a γ value of 2 in good agreement with the curve fitting technique. The inclination-corrected formation mean directions for these two a factors were statistically indistinguishable. This result shows that curve fitting is an easier, but accurate, method of applying an anisotropy-based inclination correction than direct measurement of the individual grain anisotropy in magnetic grain extracts. The corrected Glendale Formation magnetite-based palaeopole is very similar to haematite-based palaeopoles from the Carboniferous Canadian Maritimes. A new technique is described that extracts the detrital haematite grains from red sedimentary rocks. The measured haematite a γ factors from the Carboniferous Mauch Chunk and Cretaceous Kapusaliang Formations yield values consistent with susceptibility individual particle anisotropies, a χ , determined previously by curve fitting techniques, extending the use of curve fitting for individual particle anisotropy determination to haematite-bearing rocks. However, the corrected Mauch Chunk Formation palaeopole is significantly different from the corrected Glendale Formation palaeopole, calling the accuracy of the Mauch Chunk palaeopole into question. Tectonic strain during folding may have added to the compaction strain in the rocks, leading to an overcorrection of the inclination. A new, inclination-corrected palaeopole for the North American Carboniferous is reported for the Glenshaw Formation at 28.6˚N, 119.9˚E.

Remagnetization of carbonate rocks in southern Tibet: Perspectives from rock magnetic and petrographic investigations

“…The ChRM isolated from the volcaniclastic sandstones of the Wölong Formation has been interpreted to be primary and used to determine the Early Cretaceous latitude of the Tibetan Himalaya. The applied elongation/inclination correction [ Tauxe and Kent , ] suggests that inclination shallowing, as often observed in clastic rocks [ Kodama , ; Huang et al ., ], is negligible [ Huang et al ., ]. The calculated paleolatitude (pole 24 in Figure c and Table S1) is consistent with results reported from coeval volcaniclastic sandstones (pole 23 in Figure c) and lavas (poles 25 and 26) in southern Tibet [ Klootwijk and Bingham , ; Yang et al ., ; Ma et al ., ].…”

Apparent polar wander path for Adria extended by new Jurassic paleomagnetic results from its stable core: Tectonic implications

“…10), yet inclination flattening was unlikely because of the high angle between the AARM foliation plane and the bedding plane (Jackson et al, 1991, Kodama 2009). …”

New paleomagnetic results from Ordovician sedimentary rocks from NW Anatolia: Tectonic implications for the paleolatitudinal position of the Istanbul Terrane

“…Thus, hematite individual particle anisotropy has only been determined indirectly (Tan and Kodama, 2002;. We use the simplified method of Kodama (2009) to estimate the individual particle anisotropy of the magnetic carrier using the mean AMS parameters that are given in Table 1.…”

“…Another widely used method for assessing and correcting inclination biases in sedimentary rocks is defined by the method of Jackson et al (1991) (for magnetite) and (for hematite), using an anisotropy-based inclination correction (Bilardello and Kodama, 2009;Kodama, 2009Kodama, , 1997;Huang et al, 2013;Tan and Kodama, 2002;.…”

“…Anisotropy of magnetic susceptibility (AMS) measurements were collected from a total of 560 samples to obtain a mean correction factor for compaction-caused paleomagnetic inclination shallowing (Kodama, 2009;. The AMS measurements Vector plots of the characteristic remanent magnetization (ChRM) were determined by a principal component analysis (Kirschvink, 1980).…”