Sébastien Bailly
Ohhh, sunny day... Mr. S. Bailly

July 2000 - July 2001

Presently in Strasbourg

Poster at the 
VMSG Symposium 2000 [PDF]

Project Outline

The recognition of pervasive remagnetization of the natural remanent magnetization (NRM) is essential for a correct interpretation of paleomagnetic data and has, for instance, important geodynamical implications. It has only recently become apparent that this ‘remagnetization syndrome’ may be much more widespread than previously thought, particularly in sedimentary rocks of forelands and outer margins of orogenic zones. These rocks are often considered to deliver ‘ideal’ high-quality paleomagnetic data, an assumption that needs serious reconsideration.

The research aimed to address the mechanisms that are responsible for remagnetization by comparing remagnetized and non-remagnetized areas. The target is to develop the simplest possible criteria that are diagnostic of remagnetization that are independent of paleomagnetic directional data. The research strategy involves optimizing a blend of mineral-magnetic, paleomagnetic and non-magnetic methods. The latter methods include classical thin section analysis, SEM/TEM microscopy on magnetic concentrates, determination of smectite/illite ratios, as well as determination of the trace element and 87Sr/86Sr ratios in carbonates to detect modifications by basinal orogenic fluids. 

Fieldwork was planned in Paleozoic rocks in the Ardennes (remagnetized) and in Brittany (claimed to be non- remagnetized). A transect comprising remagnetized and non-remagnetized marly rocks of Cretaceous age in the Pyrenees will serve as a testcase for the criteria to be developed.