Nongeocentric axial dipole field behavior during the Mono Lake excursion

Abstract

A new record of the Mono Lake excursion (MLE) is reported from the Summer Lake Basin of Oregon, USA. Sediment magnetic properties indicate magnetite as the magnetization carrier and imply suitability of the sediments as accurate recorders of the magnetic field including relative paleointensity (RPI) variations. The magnitudes and phases of the declination, inclination, and RPI components of the new record correlate well with other coeval but lower resolution records from western North America including records from the Wilson Creek Formation exposed around Mono Lake. The virtual geomagnetic pole (VGP) path of the new record is similar to that from another high‐resolution record of the MLE from Ocean Drilling Program (ODP) Site 919 in the Irminger Basin between Iceland and Greenland but different from the VGP path for the Laschamp excursion (LE), including that found lower in the ODP‐919 core. Thus, the prominent excursion recorded at Mono Lake, California, is not the LE but rather one that is several thousands of years younger. The MLE VGP path contains clusters, the locations of which coincide with nonaxial dipole features found in the Holocene geomagnetic field. The clusters are occupied in the same time progression by VGPs from Summer Lake and the Irminger Basin, but the phase of occupation is offset, a behavior that suggests time‐transgressive decay and return of the principal field components at the beginning and end of the MLE, respectively, leaving the nonaxial dipole features associated with the clusters dominant during the excursion.

The Role of Geomagnetic Field Intensity in Late Quaternary Evolution of Humans and Large Mammals

“…The Mono Lake excursion at~34 ka has been recorded in both deep-sea sediments and lava flows (Cassata et al, 2008;Channell, 2006;Kissel et al, 2011;Laj et al, 2014;Negrini et al, 2014) as well as at Mono Lake in California (e.g., Benson et al, 2003), although the age at the Mono Lake type-location is controversial (e.g., Cassata et al, 2010;Kent et al, 2002). The age of a RPI minimum associated with the Mono Lake excursion can be estimated from a cosmogenic-isotope flux maximum in Greenland ice cores (Muscheler et al, 2005;Wagner et al, 2000).…”

Global and Regional Assessments of Paleosecular Variation Activity Over the Past 100 ka

“…The Mono Lake excursion is not visible in the PSV index stacks (Figure ). Individually, the highest P i for the Mono Lake excursion are obtained for Lake Pupuke, New Zealand (Nilsson et al, ) ( P i = 2.2 at 31.9 ka); ded8707, Mediterranean Sea (Tric et al, ) ( P i = 1.1 at 35.13 ka); ODP919, Irminger Basin (Channell, ) ( P i = 0.9 at 32.72 ka); ps2644‐5, Iceland Basin (Laj et al, ) ( P i = 0.8 at 34.28 ka); ph05, Philippine Sea (Meng et al, ) ( P i = 0.7 at 34.11 ka); Summer Lake, Oregon (Negrini et al, ) ( P i = 0.6 at 34.17 ka); and 4‐pc03, South Atlantic (Channell et al, ) ( P i = 0.6 at 34.34 ka). These P i values are considerably lower than the P i values for the Laschamp excursion (supporting information Table S3).…”

Constraining the Early Eruptive History of the Mono Craters Rhyolites, California, Based on 238U‐230Th Isochron Dating of Their Explosive and Effusive Products

“…We constrain the timing and episodicity of early rhyolitic volcanism at Mono Craters by linking several Wilson Creek tephras to their dome equivalents in the Mono Craters using combined zircon‐allanite geochronology and titanomagnetite geochemistry. Our new detailed chronology resolves lingering uncertainties regarding the age and stratigraphic position of the controversial Laschamp geomagnetic excursion recorded in the Wilson Creek formation (e.g., Cassata et al, ; Kent et al, ; Lund et al, ; Negrini et al, ; Zimmerman et al, ) and allows for an assessment of evolving magmatic conditions at Mono Craters. In addition, a well‐resolved eruption chronology of early Mono Craters volcanism can be used (by others) for accurate determinations of long‐term hazard probabilities for this young and potentially active rhyolitic system (e.g., Bevilacqua et al, , ; Hill et al, ; Miller, ; Miller et al, ).…”