Geology of the North Sea
The Iapetus suture was a major weakness creating a volcanic fault in the central North Sea during the later Jurassic period.
The Iapetus ocean was replaced with a suture line and mountain range when Laurentia, Baltica and Avalonia continents collided.
The elimination of the Rheic Ocean caused the formation of a massive mountain range through the border countries of the present day North Sea.
[1]: [52] Triassic and Jurassic volcanic rifting and graben fault systems created highs and lows in the North Sea area.
The final events affecting the North Sea coastline features and submarine topography occurred in the Cenozoic era.
[1] Plate tectonics and continental collisions (orogenies) brought the features together of the North Sea that we recognise presently.
[11] The Caledonian Orogeny caused the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided.
The basement formations of the North Sea were roughly formed during this Caledonian geosynclinal stage of the Cambrian – Devonian periods.
[13] The Caledonian mountains range helped create the 'Old Red Sandstone' continent at the joining of the tectonic plates.
These plate tectonic forces built up a mountain range extending from what is now termed the Adirondacks north through Nova Scotia, the British Isles, Norway and the eastern margin of Greenland.
[clarification needed] The area now comprising Greenland-Scandinavia-British Isles began drifting northward in the Late Carboniferous-Early Permian period.
They typically form during extension of the earth's crust with a distinct basement architecture made up of grabens and half-grabens segmented by transverse structures.
[21][22] Volcanism and a rift system developed in the central North Sea area where basaltic lavas were extruded.
[23] The mantle warped upwards creating a dome in the middle of the North Sea where the Iapetus Suture intersected the Tornquist-Teisseyre fault system.
[15]: [26] Major reservoirs were created in the North sea during this time as clastics and sands were deposited in paralic environments.
The formation of these has been influenced by the zig zag suture line of the Caledonian orogeny with its areas of crustal tension weakness.
[1]: [46] In the early Palaeogene period (Caenozoic Era) between 63 and 52 Ma, the North Sea formed, and Britain was uplifted.
[29] The Alpine Orogeny that occurred about 50 Ma was responsible for the shaping of the London Basin syncline and the Weald anticline to the south.
Plant and animal types developed into their modern forms, and by about 2 Ma the landscape would have been broadly recognisable today.
The Pleistocene saw the sea retreat from the basin as global sea-level fell due to accumulation of ice sheets.
This process can cause sudden shifts in coastlines and hydration systems resulting in newly submerged lands, emerging lands, collapsed ice dams resulting in salination of lakes, new ice dams creating vast areas of freshwater, and a general alteration in regional weather patterns on a large but temporary scale.
This type of chaotic pattern of rapidly changing land, ice, saltwater and freshwater has been proposed as the likely model for the Baltic and Scandinavian regions, as well as much of central North America at the end of the Last Glacial Maximum LGM, with the present-day coastlines only being achieved in the last few millennia of prehistory.
At one time there was land where the strait is now, a south-east extension of the Weald joining what is now Great Britain to continental Europe.
The Strait of Dover opened during the Ice Age, as described below; as a result the British Isles have now become islands not connected with continental Europe any longer.
The first was about 425,000 years ago, when an ice-dammed lake in the southern North Sea overflowed and broke the Weald-Artois chalk range in a catastrophic erosion and flood event.
In a second flood about 225,000 years ago the Meuse and Rhine were ice-dammed into a lake that broke catastrophically through a high weak barrier (perhaps chalk, or end-moraines left by the ice sheet).
As the sea levels fell in the Holocene epoch, Denmark's north coast gave way to raised spits, beach ridges and cliffs.
The area was a dry steppe landscape, overlain with rivers, where animals such as the elephant-like mastodon, scimitar cat, southern mammoth, hippopotamus, horses, bears and giant deer lived.
