Crustal and Lithospheric Structure across the Boundary of the East European Craton from Receiver Functions

Abstract:

The Trans-European Suture Zone (TESZ), which extends from the North Sea to the Black Sea, marks a fundamental lithospheric boundary in Europe. It separates the East European Craton to the north-east, which has been stable for at least 1.45 Ga, from the younger lithosphere of Phanerozoic Europe to the south-west. In this study we use a large dataset of more than 40,000 teleseismic P- and S-receiver functions from almost 500 seismological stations to image crustal and lithospheric structure across central and eastern Europe between the Benelux and the Baltic countries. An important data source is the PASSEQ project, which deployed close to 200 temporary stations between Germany and Lithuania for two years with the aim to obtain detailed, 3D information on the upper mantle structure across the TESZ. Combining P and S observations, we find a stepwise transition in crustal thickness, spread over 200 km laterally, from on average of 30 km in Phanerozoic Europe to more than 45 km beneath the East European Craton. Individual Paleoproterozoic terranes in Lithuania can also be distinguished based on crustal thickness. Crustal layering is not resolved with the receiver functions, but a high Poisson's ratio of 0.27 is obtained for the craton, compared to 0.25 for Phanerozoic Europe, which is consistent with a thick mafic lower crust. Moho depth results show an excellent correlation with the interpretation of a seismic line in the area, lending confidence to the interpretation of deeper structures. The lithosphere-asthenosphere boundary (LAB), as mapped by S-receiver functions, is located at an average depth of 90 km beneath Phanerozoic Europe. Towards the east, the LAB is dipping to about 125 km depth beneath the Elbe Line. Below the craton, a mid-lithospheric discontinuity is found at about 80 km depth, whereas weak indications of the LAB are found at an average depth of 260 km.