Testing the Reliability of Sedimentary Paleomagnetic Datasets for Paleogeographic Reconstructions

Abstract

Paleogeographic reconstructions largely rely on paleomagnetic data, mostly in the form of paleomagnetic poles. Compilations of poles are used to determine so called apparent polar wander paths (APWPs), which capture the motion through time of a particular location with respect to an absolute reference frame such as the Earth’s spin axis. Paleomagnetic datasets from sedimentary rocks are particularly relevant, because of their spatial distribution and temporal continuity. Several criteria have been proposed through the years to assess the reliability of paleomagnetic datasets. Among these, the latitudinal-dependent elongation of a given paleomagnetic directions distribution, predicted by a widely accepted paleosecular variations model, has been applied so far only to investigate inclination flattening commonly observed in sedimentary rocks. We show in this work that this concept can be generalized to detect “contamination” of paleomagnetic data derived from tectonic strain, which is not always detected by field observation only. After generating different sets of simulated geomagnetic directions at different latitudes, we monitored the variations in the shape of the distributions after applying deformation tensors that replicate the effect of increasing tectonic strain. We show that, in most cases, the “deformation” of the dataset can be detected by elongation vs. inclination ratios not conforming to the values predicted by the paleosecular variations model. Recently acquired paleomagnetic directions and anisotropy of magnetic susceptibility (AMS; a parameter very sensitive to tectonic strain) data from New Caledonia verifies the results of these simulations and highlights the importance of measuring AMS when using sedimentary paleomagnetic data for paleogeographic reconstruction. We suggest to include always AMS measurement and analysis of the distribution shape to assess sedimentary paleomagnetic data used for paleogeographic reconstructions.

Comment on “Paleomagnetism of the Late Cretaceous Red Beds From the Far Western Lhasa Terrane: Inclination Discrepancy and Tectonic Implications” by Bian et al.

“…Strain-related deflection of remanence was also subsequently recognized in detailed study of the redbeds from the Appalachians and marine marls from the Pyrenees (Larrasoaña et al, 2004;Stamatakos & Kodama, 1991a, 1991b. Recently, after applying deformation tensors on the generating geomagnetic directions at different latitudes, Dallanave and Kirscher (2020) highlight finite strain in sedimentary rocks can deviate primary paleomagnetic directions and the distribution shape of the directions.…”

Slowing Extrusion Tectonics and Accelerated Uplift of Northern Tibet Since the Mid‐Miocene

“…However, no further study has been conducted to investigate the variation of tectonic compression direction through time due partly to the debated chronological framework of the Cenozoic strata in the northern Qaidam Basin (Ji et al., 2017; Wang et al., 2017). The relatively clustered magnetic lineation direction is due to the observation that as the deformation evolves to the weak cleavage state, the principal K max axis becomes perpendicular to the shortening direction (e.g., Dallanave & Kirscher, 2020). Until now, two distinct tectonic processes are proposed to account for these changes, that is, the left‐lateral strike‐slip motion along the Kunlun fault or the eastward channel flow (Su et al., 2016; Yu, Huang, et al., 2014), and the propagation of strike‐slip faulting along the ATF into the northern Qaidam marginal thrust belt (B. Li et al., 2020; Su et al., 2016).…”

“…conceptual model of AMS development in mudrocks undergoing progressive deformation, the magnetic fabric in sedimentary rocks of the Dahonggou section can be referred to as a "weak cleavage" state (e.g., Dallanave & Kirscher, 2020;Parés et al, 1999Parés et al, , 2015. In summary, the Dahonggou AMS data record weak tectonic strain (Ji et al, 2017;Ke et al, 2013;Lu et al, 2022;Wang et al, 2017) from the Dahonggou locality which show distinctly different polarity zones for the Lulehe red bed deposits (marked in light yellow).…”

Absolute Paleolatitude of Northern Zealandia From the Middle Eocene to the Early Miocene

“…Paleolatitude estimates for northern Zealandia through the Cenozoic are uncertain because no autochthtonous paleomagnetic constraints exist, and the bordering Australian Plate has very limited data (Dallanave & Kirscher, 2020; Hansma & Tohver, 2019). At present, the paleogeographic position of Zealandia is determined via data from connected plates by means of absolute plate motion (APM) models.…”

“…While the first mainly arises from analyses of hotspot tracks, the spin axis reference frame derives from paleomagnetism (Torsvik et al, 2008(Torsvik et al, , 2012. Paleomagnetic directions measured at a given locality result in a paleomagnetic pole, which virtually coincides with the paleoposition of the Earth's spin axis relative to the sampling site (Dallanave & Kirscher, 2020;Tauxe, 2010;Vaes et al, 2021). Compilations of consecutive poles then are combined to establish an apparent polar wander path (APWP, called apparent because it rather reflects the changing orientation and distance of the plate with respect the geographic pole; Besse & Courtillot, 2002;Creer et al, 1954;Torsvik et al, 2008;Van der Voo, 1993).…”