The Weald–Artois Anticline , or Wealden Anticline , is a large anticline , a geological structure running between the regions of the Weald in southern England and Artois in northern France . The fold formed during the Alpine orogeny , from the late Oligocene to middle Miocene as an uplifted form of the Weald basin through inversion of the basin. The folding resulted in uplift of about 180 metres (590 ft), though concurrent erosion may have substantially reduced the actual height of the resulting chalk ridges.
7-534: As is the case with all anticlines, older rock strata are found in the core of the structure. These are in this case Upper Jurassic and Lower Cretaceous strata. The western part of the ridge (the Weald of Kent , Sussex and Surrey in England) has been greatly eroded, with the presumed chalk surface removed to expose older, Lower Cretaceous rocks ( Wealden Group ) and a small area of Upper Jurassic Purbeck Beds . On
14-697: The Anglian Glaciation ( MIS 12). It did not fully destroy the anticline although there was sporadic connection between the English Channel and the North Sea during periods of high sea level. The second megaflood occurred around 160,000 years ago during the Wolstonian / Saalian glaciation (MIS 6), after which Britain would be an island during periods of high sea level. During the most recent glacial period , lowering of sea levels joined
21-584: The White Cliffs of Dover . The Strait of Dover is geologically speaking a very young feature, which cuts through the much older Weald–Artois Anticline. The anticline continues uninterrupted in the subsurface of the Strait of Dover and English Channel. Gupta et al. argue that the section of the anticline between Britain and France was destroyed by two megafloods caused by the breaching of proglacial lakes . The first occurred around 450,000 years ago during
28-635: The British Isles once more to the continental mainland of Europe via Doggerland , until about 6500–6200 BCE. Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata . In European lithostratigraphy , the name " Malm " indicates rocks of Late Jurassic age. In
35-539: The French side of the English Channel more Upper Jurassic rocks crop out in a small area around Boulogne-sur-Mer and Desvres . At the flanks of the anticline outcrops of the (younger) Upper Cretaceous Chalk occur. The chalk survives as a rim of inward-facing escarpments , forming the North Downs and South Downs . The Chalk forms characteristic white cliffs on both sides of the English Channel, an example being
42-534: The north, and Gondwana to the south. The result of this break-up was the spawning of the Atlantic Ocean . However, at this time, the Atlantic Ocean was relatively narrow. This epoch is well known for many famous types of dinosaurs , such as the sauropods , the theropods , the thyreophorans , and the ornithopods . Other animals, such as some crocodylomorphs and the first birds , appeared in
49-493: The past, Malm was also used to indicate the unit of geological time, but this usage is now discouraged to make a clear distinction between lithostratigraphic and geochronologic/chronostratigraphic units. The Late Jurassic is divided into three ages, which correspond with the three (faunal) stages of Upper Jurassic rock: During the Late Jurassic Epoch, Pangaea broke up into two supercontinents , Laurasia to
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