An electrical resistivity crustal section from the Alps to the Baltic Sea (central segment of the EGT)

Abstract

Electrical resistivity models derived from magnetotelluric and magnetovariational measurements in the past 10 years have been compiled along the Central Segment of the European Geotraverse. Along the profile low-resistivity structures exist particularly in the middle and upper crust and probably mask deeper low-resistivity zones. These structures can be related to different tectonic units along the profile. The prominent features are the two-dimensional low-resistivity structures at the transition from the Moldanubian to the Saxothuringian and from the Saxothuringian to the Rhenohercynian unit of the Variscan belt, the depth correlation of the low-resistivity horizon in the Rhenish Massif with a seismic low-reflectivity band, the very high conductance of an upper to middle crustal layer in the North German Lowlands and its cessation at the river Elbe towards the Baltic Sea. The reduction in the resistivity of these zones is very likely due to graphite at mid-crustal depths. It is obvious that there exists a general increase of electrical conductance in the upper half of the crust from south to north of the Central Segment which may be due to increasing accumulation of graphite and successive tectonically controlled ordering processes. This phenomenon may, by relating it to the growing crustal age from south to north, be the indicator of a maturing continental crust.