A high‐velocity layer in the lower crust of the North German Basin

Abstract

A network of deep seismic refraction profiles in Northern Germany consisting of parts of the European Geotraverse (EGT) and additional new Unes is interpreted. The most striking result is the proof of an approximately 10 km thick high‐velocity layer in the lower crust. Its P‐wave velocity of 6.9‐7.5 km s−1 is typical for shield crusts or lower crust in extensional environments intruded by mafic magma. The layer is observed in an area of roughly 150 × 180 km north of the Elbe river and seems to continue north‐east, at least up to the Caledonian deformation front at the southern edge of the Ringkøbing‐Fyn High. It correlates spatially with an area of high positive gravity anomalies. Here, a Moho topography of several kilometres, which had already been postulated on the basis of gravity inversions and sporadic near‐vertical PMP reflections, could be confirmed by the interpretation of seismic wide‐angle records. The termination of the high‐velocity lower crust at the Lower Elbe Lineament, which strikes parallel to the Teisseyre‐Tornquist Zone, contributes to its definition as a major lineament in the context of central European tectonics.

The Trans-European Fault: a critical reassessment

“…However, in the text, Hoffman, Stiewe & Pasternak (1996) somewhat puzzlingly suggest that the significant differences in Moho depth reported by Thybo et al (1990) across the TransEuropean Fault are not confirmed by their study, although their figure 5 and supporting data would appear to contradict this statement. Rabbel et al (1995) reported an area of increased crustal thickness in the region of the Ringkøbing-Fyn High which corresponds to a c. 7 km deepening of the Moho. They suggest that the southern boundary of this Moho low corresponds with the postulated Trans-European Fault trend.…”

“…Such evidence includes the increased crustal velocities in the area extending from the Baltic Shield to the Elbe Lineament (Rabbel et al 1995). There is a sharp velocity contrast in the lower crust between the regions southwest and northeast of the Elbe Lineament (Rabbel et al 1995;Thybo, 1990). To the southwest the velocities range from 5.9-6.6 km/sec, and increase in the northeast up to 6.9-7.5 km/sec.…”

Style and evolution of salt pillows and related structures in the northern part of the Northeast German Basin

“…This fault system is part of the Elbe Lineament (Fig. 1), a regionally important structure which separates crustal domains of differing physical properties (Rabbel et al 1995;Tanner and Meissner 1996). Along the Elbe Lineament strike-slip movements during the Variscan orogeny were followed by oblique thrusting culminating in the Upper Cretaceous related to collisional processes in the Alps (Schretzenmayr 1993;Ziegler 1990).…”

Geophysical and petrological modeling of the lower crust and uppermost mantle in the Variscan and Proterozoic surroundings of the Trans-European Suture Zone in Central Europe

“…Seismic data indicate a high-velocity lower part of the crust in the TESZ in Germany, interpreted to be due to abundant mafic intrusions (Rabbel et al, 1995;Bayer et al, 2002;Thybo, 1997Thybo, , 2000. The SW limitation of this crust is the Elbe line (Aichroth et al, 1992).…”

“…The The lower crust of the P1 profile is seismically a continuation of that of the EEC (Guterch et al, 1994;Rabbel et al, 1995;Jensen et al, 1999;Grad et al, 2002Grad et al, , 2003. However, the heat flow in the area of the TESZ and adjoining parts of the Variscan Orogen is significantly higher.…”