A new high‐resolution geomagnetic relative paleointensity record for the North American Holocene: A comparison of sedimentary and absolute intensity data

Abstract

Abstract. A new high-resolution paleointensity record for North America has been constructed using Holocene sediments from Lake Pepin, Minnesota. Lake Pepin sediments yield the same Holocene paleosecular variation curve as nearby Lake St. Croix and satisfy all of the criteria recommended for paleointensity studies. Absolute paleointensity data for North America recorded by Holocene volcanic and archeomagnetic samples provide an independent record of geomagnetic field paleointensity against which the relative intensity records from Lake Pepin and Lake St. Croix can be compared. Since the absolute field paleointensity is known a priori, the effects of the magnetic recording assemblage can be isolated. Anhysteretic remanent magnetization (ARM) is the best choice among normalization parameters for the Lake Pepin sediments as the natural remanent magnetization (NRM) normalized by ARM shows no coherence with magnetic grain size proxies and yields a record of relative paleointensity peaks and troughs whose amplitudes are very similar to those in the archeomagnetic (ARCMAG) and Lake St. Croix data sets. Features with a wavelength of 1000 years are correlative between the three paleointensity records. NRM normalized by saturation isothermal remanent magnetization (SIRM) and by susceptibility (Z) shows grain-size dependences that cause errors in the amplitudes of paleointensity features. NRM/SIRM and NRM/z are not coherent with their normalizers but are both strongly coherent with independent grain size proxies such as the median destructive field of the NRM and HcR. We successfully removed the grain size dependences from NRM/SIRM by applying a correction function based on the linear relationship between normalized intensity and the median destructive field of the NRM.

Propriétés magnétiques et sédimentologiques de séquences holocènes de l'estuaire du St-Laurent et du fjord du Saguenay, Canada /

“…Figure 11 shows how the RPI record from core 2220 compares with similar records from Lake Pepin [33] and Lake St. Croix [43], Minnesota (USA) and from Lake LeBoeuf [38], Pennsylvania (USA).…”

“…9). Figure 7 shows the inclination and declination records of core 2220 on the 14 C age model presented in EPSL Online Background Dataset Figure 9 along with North American paleomagnetic secular variation (PSV) records from Lake St. Croix [32] and Lake Pepin (Minnesota, USA) [33], Fish Lake (Oregon, USA) [34] and with a recent compilation of lava flows from the western United States [35]. Comparable inclination and declination patterns are observed in all records suggesting that core 2220 preserves Holocene PSV.…”

“…Dated material at depths marked with an asterisk are considered invalid and were not used to construct the age models. [32], Lake Pepin [33] and Fish Lake records [34], and a compilation of lava flows from the western United States transformed into directional space at the Fish Lake location (diamonds) [35].…”

Environmental influence on relative palaeointensity estimates from Holocene varved lake sediments in Finland

“…Despite the rather strict constraints, relative palaeointensity records have been proposed in several recent studies, which have encouraged further investigations on relative palaeointensity using high-resolution sedimentary records (St-Onge et al, 2003;Richter et al, 2006;. In some cases, the reliability of relative palaeointensity reconstructions has been questioned due to unremoved climatic and/or environmental imprint (Weeks et al, 1995;Schwarz et al, 1996;Lund and Schwarz, 1999;Kok, 1999;Brachfeld and Banerjee, 2000;Nowaczyk et al, 2001;Frank et al, 2002).…”

How does Chinese loess become magnetized?

“…In the past two decades, numerous relative geomagnetic paleointensity studies have been made on marine sediments (Tauxe and Valet, 1989;Valet et al, 1994;Yamazaki et al, 1995;Guyodo and Valet, 1996;Channell et al, 1997;Roberts et al, 1997;Brachfeld and Banerjee, 2000;Horng et al, 2003;Suganuma et al, 2008).…”