TECTONIC UNITS AND EVOLUTION IN THE NORTH-WEST EUROPE OFFSHORE AND NEIGHBOURING AREAS

Four first order tectonic units, i.e the Laurentia plate, Avalonia plate, Baltica plate and Gongwana plate, are recognized in the North-West Europe offshore and neighbouring areas. There are seven second order units, incuding two units, the Laurentia block and Laurentia Caledonian orogenic belt in the Laurentia plate,two units, the Avalonia Caledonian orogenic belt and Avalonia Variscan orogenic belt in the Avalonia plate, two units, the Baltica block and Baltica Caledonian orogenic belt in the Baltica plate, and one unit, the Gongwana Variscan orogenic belt in the Gongwana palte.In the North-West Europe, Palaeozoic orogeny can be divided into two separate events, the Caledonian and the Variscan, The Caledonian collision involved three plates, the Laurentia plate, Avalonia plate and Baltica plate. Prior to the collision, the Tornquist Ocean separated the Baltica plate from Avalonia plate, and the Iaptus Ocean separated the Laurentia plate from the two opposite plates. The Caledonian collision resulted in the Caledonian orogeny. During the Mid to Late Carboniferous,the Variscan orogency closed the Iaptus Ocean among Laurentia plate, Avalonia plate and Baltica plate.The Mesozoic continental rifting tectonic movement represented a process to rework or break the preexisting Precambrian-Palaeozoic accretionary structures, and formed a series of rift basins in North-West Europe. During the Early Cretaceous, oceanic spreading broke through the Gibraltar Transform to initiate separation between North America and Iberia. During the Paleocene and Eocene, the North Atlantic was affected by a mantle plume that weakened the lithosphere and allowed the renewed spreading. Oceanic crust formed after only a slight amount of Eocene extension, leading to the separation of Greenland from Europe and ocean-ridge propagation into the Arctic.