The Tornquist Sea or Tornquist Ocean was a sea located between the palaeocontinents Avalonia and Baltica about . The remains of the sea today form a suture stretching across northern Europe (Tornquist Zone).
It probably formed at the same time (c. 600 Ma) as the Iapetus Ocean. Gondwana, including Avalonia until Early Ordovician, was separate from Baltica throughout the Cambrian. It probably closed during the Late Ordovician at the time of the Shelveian Orogeny of western England.
The Baltica-Avalonia collision also resulted in that the Rheic Ocean ceased to expand south of Avalonia around 450 Ma, in huge magmatism in Avalonia, gigantic ash fall in Baltica, and metamorphism in present-day northern Germany.
The suture resulting from closure of the Tornquist Sea may be seen in eastern England and the Lake District as an arc of igneous rocks belonging to the Ordovician. The volcanic series in eastern England, the Ardennes and the Northern Phyllite Belt originated between the Tornquist Sea and the Rheic Ocean during the Ordovician and Silurian.
Where Baltica and Avalonia finally collided is now a suture known as the Teisseyre-Tornquist Line or Zone; named after its discoverer, Polish geologist Wawrzyniec Teisseyre and German geologist Alexander Tornquist. This lineament still marks the transition between, on one hand, the East and North European Pre-Cambrian Craton and, on the other hand, the West European and Mediterranean Palaeozoic Orogenes. It is part of a wider deformation zone running across Europe, from the British Isles to the Black Sea, known as the Trans-European Suture Zone (TESZ).
- McKerrow et al. 2000, p. 12
- Torsvik et al. 1993, Summary; Torsvik & Rehnström 2003, 8. Avalonia and Baltica convergence and the tale of K-bentonites, pp. 77–80. Torsvik et al. 1993 proposed a "pre-Wenlock (Early Silurian) collision" but (e.g.) Torsvik & Rehnström 2003 modified the timing to Late Ordovician.
- Nance et al. 2010, 3.2. Closure and collision, pp. 7–8
- Teisseyre & Teisseyre 2002, p. 841; Tornquist erroneously identified as a "Swedish magnetologist"
- Grad, Guterch & Polkowska-Purys 2005
- Grad, M.; Guterch, A.; Polkowska-Purys, A. (2005). "Crustal structure of the Trans-European Suture Zone in Central Poland— reinterpretation of the LT-2, LT-4 and LT-5 deep seismic sounding profiles" (PDF). Geological Quarterly 49 (3): 243–252. Retrieved November 2015.
- McKerrow, W. S.; Mac Niocaill, C.; Ahlberg, P. E.; Clayton, G.; Cleal, C. J.; Eagar, R. M. C. (2000). "The late Palaeozoic relations between Gondwana and Laurussia" (PDF). Geological Society, London, Special Publications 179 (1): 9–20. doi:10.1144/GSL.SP.2000.179.01.03. Retrieved November 2015.
- Nance, R. D.; Gutiérrez-Alonso, G.; Keppie, J. D.; Linnemann, U.; Murphy, J. B.; Quesada, C.; Strachan, R. A.; Woodcock, N. H. (2010). "Evolution of the Rheic ocean" (PDF). Gondwana Research 17 (2): 194–222. doi:10.1016/j.gr.2009.08.001. Retrieved November 2015.
- Teisseyre, R.; Teisseyre, B. (2002). "Wawrzyniec Karol de Teisseyre: A Pioneer in the Study of "Cryptotectonics"". Eos 83 (47): 841–556. Retrieved November 2015.
- Torsvik, T. H.; Smethurst, M. A.; Van der Voo, R.; Trench, A.; Abrahamsen, N.; Halvorsen, E. (1993). "Baltica. A synopsis of Vendian-Permian palaeomagnetic data and their palaeotectonic implications" (PDF). Earth-Science Reviews 33 (2): 133–152. Retrieved November 2015.
- Torsvik, T. H.; Rehnström, E. F. (2003). "The Tornquist Sea and Baltica–Avalonia docking" (PDF). Tectonophysics 362 (1): 67–82. doi:10.1016/S0040-1951(02)00631-5. Retrieved November 2015.