Geomagnetic secular variations at the Mesozoic-Cenozoic boundary
Abstract
Study of changes in geomagnetic secular variations through geological time is essential to document the Earth's magnetic field evolution and provides an important constraint for geodynamo modeling. Moreover, knowledge of the secular variations value for any specific geological epoch (paleosecular variations - PSV) may give an additional tool to constrain the duration of emplacement and cooling of various magmatic bodies including flows, dykes and sills. In order to obtain a reliable estimate of value of PSV at the Paleozoic-Mezozoic boundary we have undertaken a paleomagnetic study of several important volcanic sections of the Siberian Permo-Triassic (P-T) traps from the Noril'sk and Maymecha-Kotuy areas. In total we have studied 80 flows from the Maymecha-Kotuy region and 54 flows from the Noril'sk region. In 116 of them we have isolated high temperature component, which we interpret to be primary. These data have been combined with results obtained earlier by Heunemann et al, 2004 from 76 volcanic flows from other trap sections of the Noril'sk region. Then, according to approach described in Chenet et al. (2008) we have identified directional groups (DG) and individual directions (ID) corresponding to brief volcanic pulses and individual eruptions. The mean directions of these DGs and IDs have been considered as snapshots of the changing P-T geomagnetic field and used for calculation of the scatter of virtual geomagnetic poles, which is commonly accepted to be a measure of paleosecular variations. Obtained result (17+1.9-2.2)° taken together with nearly coeval data from East Kazakhstan (Lyons et al., 2001) and South-Western China (Liu et al., 2012) fits well with values expected from latitude dependence compiled by McElhinny and McFadden (1997) from data for last 5 million years and from latitude dependence predicted from model TK03 (Tauxe and Kent, 2004). Thus these results suggest that geomagnetic field variations at the Permo-Triassic boundary were the about the same as during the Latest Cenozoic.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2013
- Bibcode:
- 2013AGUSMGP23C..04P
- Keywords:
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- 1522 GEOMAGNETISM AND PALEOMAGNETISM / Paleomagnetic secular variation