Paleointensity of the Geomagnetic Field During the Last 80,000 Years

Emmanuel Tric (1) , Jean-Pierre Valet (1, 2) , Piotr Tucholka (3) , Martine Paterne (1) , Laurent Labeyrie (1) , Francois Guichard (1) , Lisa Tauxe (4) , Michel Fontugne (1) , $ean-Pierre Valet

1 Centre des Faibles Radioactivités
2 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
3 Laboratoire de Géophysique [Orsay]
4 The Scripps Research Institute [La Jolla, San Diego]

High-resolution records of the relative paleointensity of the geomagnetic field have been obtained from five marine cores. Three duplicate records were used to estimate the regional coherency of the data within a single area (Tyrrhrenian Sea) while the two others document the field variations in the eastern Mediterranean and the southern Indian Ocean. Careful investigations of distinct rock magnetic parameters have established the downcore unifornfity of the sediments in terms of magnetic nfineralogy and grain sizes. The time-depth control was provided by oxygen isotopes, and small-scale variations in the deposition rates were constrained by means of tephrachronology. The synthetic curve calculated from the Mediterranean records provides a continuous record of the intensity variations during the last 80,000 years (80 kyr), which correlates well with the sparse volcanic data available for the period 0-40 kyr. The fact that identical behavior is seen in both data sets and that they also compare quite well with results from a core collected in the Pacific Ocean establishes the truly dipolar character of these variations. The dipole field moment is characterized by large-scale changes as shown by the existence of pronounced drops (at 39 and 60 kyr) alternating with periods of higher intensity. The record suggests a periodic nature for these intensity variations; however, the period studied is not sufficiently long to state this conclusively. These results demonstrate the potential of sediments for such studies and constitute a first step towards obtaining a global paleointensity record over a long period of time.

Domaines: Océan, Atmosphère; Interfaces continentales, environnement

Emmanuel Tric, Jean-Pierre Valet, Piotr Tucholka, Martine Paterne, Laurent Labeyrie, et al.. Paleointensity of the Geomagnetic Field During the Last 80,000 Years. Journal of Geophysical Research, 1992, 97 (B6), pp.9337. ⟨10.1029/91JB01620⟩. ⟨hal-03543415⟩