Detection of a new sub-lithospheric discontinuity in Central Europe with S-receiver functions Rainer Kind a,b, ⁎, Mark R. Handy b , Xiaohui Yuan a , Thomas Meier c , Horst Kämpf a , Riaz Soomro d a GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany b Freie Universität, Institut für Geologische Wissenschaften, Malteserstrasse 74-100, 12249 Berlin, Germany c Christian-Albrechts Universität, Institut für Geowissenschaften, Otto-Hahn-Platz 1, 24118 Kiel, Germany d Seismic Studies Programme, Nilore, Islamabad 44000, Pakistan abstract article info Article history: Received 10 September 2016 Received in revised form 30 January 2017 Accepted 6 February 2017 Available online 13 February 2017 We used S-receiver functions (i.e. S-to-P converted signals) to study seismic discontinuities in the upper mantle between the Moho and the 410 km discontinuity beneath central Europe. This was done by using c. 49,000 S-re- ceiver functions from c. 700 permanent and temporary broadband stations made available by the open EIDA Archives. Below Phanerozoic Europe we observed expected discontinuities like the Moho, the lithosphere-as- thenosphere boundary (LAB), the Lehmann discontinuity and the 410 km discontinuity with an additional over- lying low velocity zone. Below the East European Craton (EEC), we observed the Mid-Lithospheric Discontinuity (MLD) at c. 100 km depth as well as the controversial cratonic LAB at c. 200 km depth. At the boundary of the EEC but still below the Phanerozoic surface, we observed downward velocity reductions below the LAB in the follow- ing regions: the North German-Polish Plain at about 200 km depth; the Bohemian Massive, north-west dipping from 200 to 300 km depth; the Pannonian Basin, north-east dipping from 150 to 200 km depth underneath the western Carpathians and the EEC. We named this newly observed structure Sub-Lithospheric Discontinuity (SLD). At the northern edge of the Bohemian Massive, we see a sharp vertical step of about 100 km between the SLD below the Bohemian Massive and the North German-Polish Plain. This step follows the surface trace of the Rheic Suture between the continental Saxo-Thuringian and Rheno-Herzynian zones of the Variscan orogen. A preliminary interpretation of these features is that a prong of the cratonic mantle lithosphere penetrated the Phanerozoic asthenosphere during the continental collision at the western and south-western edges of the EEC. © 2017 Elsevier B.V. All rights reserved. Keywords: Lithosphere-asthenosphere boundary (LAB) Mid-lithospheric discontinuity (MLD) Sub-lithospheric discontinuity (SLD) S-receiver functions East European Craton Bohemian Massif Pannonian Basin 1. Introduction The basic geology of central Europe north of the Alps is highly complex and determined by the Caledonian and Variscan orogenies which resulted from the collision of the plates of Gondwana and Laurussia, and numerous Peri-Gondwanan related microterranes which lay in between. Especially the closing of the Rheic Ocean in the Paleozoic (e.g. Linnemann, 2007; Nance and Linnemann, 2008; Zeh and Gerdes, 2010; Kroner and Romer, 2013) caused subduction, volca- nisms and accretion of a number of terrains (e.g. Bohemian Massif or Rhenish Massif). The geology of the Mediterranean area is determined by the Alpine orogeny which is caused by the collision of the African plate with the European plate and several microplates (Adria, Iberia, Anatolia) since the late Mesozoic (e.g. Faccenna et al., 2014). The Alps, the Apennines, the Dinarides and Carpathians are expressions of this collision (see Fig. 1 for location of tectonic boundaries). The Tornquist- Teisseyre Zone (TTZ) is the most significant structure in Europe which separates the East European Craton (EEC) from Phanerozoic Europe. Finding the cause of this dynamics of the lithospheric plates requires in- tegrating images of deep structures with surface geology which pre- serves the records of motion back in time. Here we are studying the deep structure. There are numerous seismic techniques used for study- ing discontinuities in the upper mantle. The oldest technique is wide angle seismics where the horizontal ray path is much longer than the vertical one. Gutenberg (1926) found with this technique the downward velocity reduction in the oceanic upper mantle at 60–80 km depth which bears his name. He concluded that the mantle was crystalized to that depth. There are many wide and steep angle controlled source profiles which sample the structure of the continental mantle below the Moho in northern Europe, North America and other regions. North of the Alps and beneath Paleozoic Europe, the Moho is relatively flat at a depth of about 30 km and shows no significant lateral variations (Grad et al., 2009). Geology indicates a complex history of accretion and subduction, followed by late- to post-Variscan magmatism and oblique-slip tectonics (e.g., Matte, 1998; Franke, 2000, 2014). Accordingly, the overall laterally continuity of the European Moho is attributed to this post-Variscan Tectonophysics 700–701 (2017) 19–31 ⁎ Corresponding author at: GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany. E-mail addresses: kind@gfz-potsdam.de (R. Kind), mark.handy@fu-berlin.de (M.R. Handy), yuan@gfz-potsdam.de (X. Yuan), meier@geophysik.uni-kiel.de (T. Meier), kaempf@gfz-potsdam.de (H. Kämpf), riaz_soomro@yahoo.com (R. Soomro). http://dx.doi.org/10.1016/j.tecto.2017.02.002 0040-1951/© 2017 Elsevier B.V. All rights reserved. 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