A 17,000 yr paleomagnetic secular variation record from the southeast Alaskan margin: Regional and global correlations

Abstract

High-resolution sedimentary records from two cores from the Gulf of Alaska margin allow development of a ~17,400 year reconstruction of paleomagnetic secular variation informing on regional and global variability. General agreement between the two records on their independent chronologies confirms that local PSV is recorded, demonstrating that such archives, notwithstanding complexities due to variable sedimentary regimes, deposition rates, and diagenetic conditions, can provide meaningful information on the past changes of the geomagnetic field. Comparisons with other independently-dated sedimentary paleomagnetic records from the greater Northeast Pacific indicate largely coherent inclination records that can be used to produce a regional inclination anomaly stack (NEPSIAS) capturing the common signal over an area spanning >30° longitude and latitude from Alaska through Oregon to Hawaii. Comparison of NEPSIAS with high quality declination records from the northern North Atlantic show significant similarity. Negative (shallow) anomalies in NEPSIAS inclination are associated with eastward NNA declination while positive (steep) anomalies in NEPSIAS inclination are associated with NNA westward declinations. The directional records can be compared to regional geomagnetic intensity over the past ~3000 years in North America and back nearly 9000 years in the Euro/Mediterranean region, suggesting oscillations in the relative strength of the North American flux lobe and Euro/Mediterranean extension of the Siberian flux lobe. This implicates a long-lived organizing structure imposed on the geomagnetic field, perhaps controlled by lower mantle and/or inner core heterogeneities, and supports the potential for stratigraphic correlation of directional PSV as a dating tool throughout the Holocene and perhaps beyond.

Dynamic time warping of palaeomagnetic secular variation data

“…(ii) MD99-2269 and MD99-2322 have already been shown to record high fidelity PSV via supervised correlations consistent with the cores' radiocarbon constraints and comparison to other records on regional and hemispheric spatial scales (Ólafsdóttir et al 2013, 2019Stoner et al 2013;Walczak et al 2017;Reilly et al 2019).…”

“…However, records could be compared over greater distances if systematic relationships within regional PSV data are understood, as has been suggested for centennial to millennial timescale variations (e.g. Valet et al 2008;Nilsson et al 2010Nilsson et al , 2011Stoner et al 2013;Walczak et al 2017).…”

Holocene chronostratigraphy of northeastern Baffin Bay based on radiocarbon and palaeomagnetic data

“…; Walczak et al . ). We therefore choose to exclude the geomagnetic model outputs as chronostratigraphical markers and focus the comparison on independently radiocarbon‐dated records (Table ).…”

SedCT: MATLAB™ tools for standardized and quantitative processing of sediment core computed tomography (CT) data collected using a medical CT scanner

“…In recent years, medical computed tomography (CT) scanners have become common in the nondestructive analysis of sediment cores [St-Onge et al, 2007], including high-resolution reconstructions of relative or calibrated density for paleoenvironmental interpretation [Boespflug et al, 1995;Ashi, 1997;Lis e-Pronovost et al, 2009;St-Onge and Long, 2009;Støren et al, 2010;Davies et al, 2011;Dorfman et al, 2015], assessment of coring deformation [Ashi, 1997;Barletta et al, 2010;Walczak et al, 2017], and variations in sedimentological structures or components [Michaud et al, 2003;Gagnoud et al, 2009;Goldfinger et al, 2013;Mena et al, 2015;Patton et al, 2015]. Medical CT scanners measure the attenuation of X-rays, a function of density and atomic number, and store these values in pixels as relative gray scale values or Hounsfield units (HU), achieving resolution around 0.5 3 0.5 3 0.5 mm [Hounsfield, 1973].…”