On the nonexistence of a Saxo-Thuringian Ocean – a review

As demonstrated by the Saxo-Thuringian Ocean, some regional geological models originated prior the advent of plate tectonics and evolved little since. Despite the abundance of facts that neither prove nor need the existence of such an ocean, this plate tectonic scenario is still widely used. The Saxo-Thuringian and Moldanubian zones represent classical areas of the Central European Variscides. The Saxo-Thuringian Zone originally was defined as a narrow marine basin with Paleozoic lithologies overlying a Precambrian basement. Early mobilistic models proposed an allochthonous origin of the Münchberg Massif, representing remnants of the Moldanubian Zone, thrusted onto a southeastern ramp of the autochthonous Saxo-Thuringian Basin. With the advent of plate tectonics, the Saxo-Thuringian Zone was reinterpreted as an independent microplate that is surrounded by oceanic lithosphere. In such a view, the subduction of a so-called Saxo-Thuringian Ocean beneath a Moldanubian microplate is necessary to transport Moldanubian crust onto the autochthonous Precambrian / Paleozoic units of the Saxo-Thuringian microplate. Over the last decades abundant new geoscientific data, including the results of the continental deep drill hole (KTB), challenged the Saxo-Thuringian Ocean hypothesis. Today there exist ample evidence (i) that the allochthonous units of the Saxon Granulite Massif and the Fichtelgebirge-Erzgebirge nappe pile experienced pervasive and prolonged Variscan tectono-metamorphic overprint and do not represent an older Precambrian ramp and (ii) that early Paleozoic Saxo-Thuringian marine lithologies were deposited on a vast contiguous Peri-Gondwana shelf. Incomplete recycling of extended continental crust during prolonged Gondwana Laurussia collision can explain the geological record of the Saxo-Thuringian Zone.