Tectonic accretion of the Rheno-Hercynian foreland, documented by detrital zircons in the Carboniferous flysch of the Rheinisches Schiefergebirge (Variscides, Germany)

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The active, southern margin of the Rheno-Hercynian Orogen has accreted, at least from the Namurian C onwards, Devonian clastic shelf sediments with zircons derived from the Caledonides and the East European Platform. In Tournaisian to mid-Viséan greywacke turbidites from the Rheno-hercynian allochthons (Hörre, Kellerwald), these zircons are not yet detectable.Laser-ICP-MS dating of zircons from synorogenic turbidites of the missing interval (late Viséan to Namurian B of the autochthon) is expected to reveal the onset of accretion and erosion of north-derived Devonian clastic sediments. Zircon data will be controlled by K/Ar dating of slates from potential source rocks.Previous studies on the mineral composition of Rheno-Hercynian synorogenic clastic sediments permits to estimate the proportion of recycled shelf deposits. Since contours and isopachs of the foreland basin are well-known, the above findings can be used to balance the volume and section of the recycled sediments. That section must be added to the passive margin of Laurussia + Avalonia in order to achieve an improved palispastic reconstruction.