The history of remagnetization of sedimentary rocks: deceptions, developments and discoveries

Abstract

Remagnetizations have been recognized ever since magnetizations in rocks were demonstrably shown to have been acquired at a much later time than the formation or deposition of the rocks themselves. There was mention of remagnetizations as early as the 1950s, and in the 1960s the concept was frequently hypothesized as an explanation for repetitions and loops in apparent polar wander paths. In this paper, remagnetization features and processes are organized by magnetic carrier: hematite, magnetite, Fe-sulphides and goethite. Selected case histories are presented which are chosen in order to reveal important diagnostics, although many origins of remagnetizations are still obscure or incompletely known.

Magnetic mineral diagenesis

“…Application of modern paleomagnetic analysis, with detailed stepwise demagnetization and principal component analysis to identify characteristic remanent magnetization components, can be used to resolve these issues because pigmentary and specular hematite produce contrasting unblocking temperature spectra (van der Voo and Torsvik, 2012). Pigmentary hematite typically undergoes gradual unblocking and specular hematite tends to undergo sharper unblocking at the Néel temperature of hematite, 680°C (Collinson, 1974;van der Voo and Torsvik, 2012). Red beds can record paleomagnetic signals due to both a DRM and a CRM, and later hematite growth can cause remagnetization of a primary DRM.…”

“…Remagnetizations can occur in any environment in which secondary magnetic minerals form, including oxic (e.g., van der Voo and Torsvik, 2012), sulphidic (e.g., Roberts and Weaver, 2005), and methanic environments (e.g., Weaver et al, 2002;Larrasoaña et al, 2007), or at moderate (e.g., Aubourg and Pozzi, 2010;Kars et al, 2012Kars et al, , 2014 carbonates, together with stable SD particles, produces characteristic wasp-waisted hysteresis behaviour (Jackson 1990;Roberts et al, 1995;Tauxe et al, 1996) that contrasts with that of nonremagnetized carbonates (e.g., Roberts et al, 2013a). Such hysteresis signatures have been argued to provide a fingerprint for carbonate remagnetization (Jackson, 1990;McCabe and Channell, 1994;Channell and McCabe, 1994;Jackson and Swanson-Hysell, 2012;van der Voo and Torsvik, 2012).…”

Remagnetization and chemical alteration of sedimentary rocks

“…The reader is referred to Van der Voo & Torsvik (2012) for a summary of the history of the red bed debate. Some Mesozoic red beds contain a detrital remanent magnetization (DRM; e.g.…”

“…In addition to several case studies, the book includes a paper on the history of remagnetization studies (Van der Voo & Torsvik 2012) as well as a number of review articles on various aspects of remagnetization. This introductory paper provides a general overview and reviews our current knowledge of chemical remagnetization mechanisms.…”

Acquisition of chemical remanent magnetization during experimental ferrihydrite–hematite conversion in Earth-like magnetic field—implications for paleomagnetic studies of red beds

“…The detrital hematite is usually the dominant and faithful magnetization carrier in red beds (Collinson, 1966(Collinson, , 1974Tauxe et al, 1980). However, paleomagnetic records of red beds are often affected by chemical remanent magnetization (CRM) acquired after deposition residing in authigenic hematite (Kent et al, 1987;McCabe and Elmore, 1989;Wang and Van der Voo, 1993;Elmore et al, 2006; Van der Voo and Torsvik, 2012). CRM usually overprints the primary remanent magnetization of red beds -a detrital remanent magnetization (DRM) either partially or completely, and thus complicates paleomagnetic interpretations (Stearns and Van der Voo, 1987;Huang and Opdyke, 1996;Deng et al, 2007;Dekkers, 2012).…”