From collision to collapse: phases of lithospheric evolution as monitored by seismic records

• Published in: Physics of the earth and planetary interiors Vol. 79; no. 1; pp. 75 - 86
• Main Authors: Meissner, Rolf, Tanner, Barbara
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01.08.1993; Amsterdam Elsevier Science; New York, NY
• Subjects: Applied geophysics; Earth sciences; Earth, ocean, space; Exact sciences and technology; Internal geophysics; Tectonics. Structural geology. Plate tectonics; Alps; Great Britain; Europe; Atlantic Ocean; North Atlantic; European Atlantic; France; Central Europe; Germany; Baltic Sea; Western Europe; brittle deformation; delamination; reflection methods; vertical seismic profiles; tectonic units; shear; reflection; underplating; collapse structures; Caledonides; creep; igneous rocks; lower crust; crustal shortening; stretching; deep seismic sounding; compression tectonics; intrusions; ductile deformation; granites; Variscides; plate collision; Baltic Shield; ocean closure
• ISSN: 0031-9201; 1872-7395
• DOI: 10.1016/0031-9201(93)90143-W

Deep seismic reflection profiles in Europe and elsewhere cover a range of different tectonic units. Specifically, in western and central Europe they cross structures relating to the Alpine, Variscan and Caledonian orogens with considerable crustal shortening, delamination, and interfingering. The Variscan mountain belts in France and Germany show collapsed structures from various collision events between 300 and 350 Ma ago. Still further north in middle England and the southwest Baltic Sea traces of the Caledonian collision around 400 Ma and associated collapse structures are visible. Here, the terrain East Avalonia (Cadomia) docked to the colliding continents of Baltica and Laurentia in a complex pattern with closing oceans and compressional boundaries, which can still be seen in today's seismic sections in Britain and the SW Baltic Sea. All the processes of crustal shortening, interfingering and delamination were certainly active during the compressional stages of these earlier orogens and have left their marks, which are still recognizable in today's seismic image of the crust. Crustal roots and high elevations have disappeared in the extensional collapse phase, thermal events have intruded, ‘underplated’ or otherwise modified the stretched lower crust. In the Variscan internides massif granite production started, and the lower crust assumed an especially strong and thick sheared, laminated structure with a plane Moho. The various tectonic stages are illuminated by a gross analysis of reflectivity patterns. We postulate that the fate of these patterns from their origin to their death is imbedded in thermally and rheologically varying creep processes, which always accompany the brittle and ductile deformation in the Earth's crust.