The great lignite hunt

• Main Author: Muir-Wood, Robert
• Format: Book Part
• Language: English
• Published: Oxford University PressOxford 2024
• Subjects: Norwegian Sea
• Online Access: http://dx.doi.org/10.1093/oso/9780198871620.003.0007; https://academic.oup.com/book/chapter-pdf/58292295/oso-9780198871620-chapter-7.pdf

Abstract Starting towards the end of the Eocene, a great NNE oriented crack began to open and turn into a broad rift valley, around the modern course of the River Rhine where it forms the France-Germany border. This rifting and extension by around 5km continued through the Oligocene. To accommodate this opening in the plate the extension passed to the southwest along a series of rifted basins in south central France into the Mediterranean. To the northwest through the Netherlands, displacement was carried along WNW strike-slip faults and NNW trending extensional faults. This tectonic pattern continued offshore East Anglia and into northern England. While the whole of Britain and Ireland remained a thickly forested landmass, by the end of the Oligocene around 25 million years ago, the combination of two sets of strike-slip faults oriented NE-SW and NNW-SSE created a series of lake basins running from Brittany to the Hebrides, with their locations influenced by the sites of the former volcanoes. The most distinctive feature of the geology of these basins is the presence of thick deposits of lignite reflecting anaerobic conditions. The tectonics of this 800km line of lake basins is linked with what was happening beneath the Norwegian Sea where a rotation in the spreading direction had caused the transform fault located to the west of the Shetlands to become jammed, forcing up two ranges of seafloor mountain ranges absorbing 4km of collision. By the end of the Oligocene this brought seafloor spreading almost to a halt and led to a reconfiguration of spreading ridges and transform faults that could bypass the blocked transform.