A fossil landslide preserved offshore at Lyme Regis, Dorset, UK

摘要: Multidisciplinary studies carried out in advance of site investigations the areas at Lyme Regis, Dorset most threatened by a combination landslides and marine erosion included sidescan-sonar, bathymetric seismic-reflection surveys adjacent offshore area. These revealed a large area (over 1500 m long x 700 wide) 500 to offshore from present-day coastline in which an irregular sea bed is strewn with rock debris. This underlain layer heterogeneous material up 30 m thick traces disturbed bedding shear planes. Comparison stratigraphy structure underlying situ beds, as determined surveys, suggests that residue single large (> 10 million tonnes) landslide resulted failure seaward-dipping mudstones lower part Jurassic Charmouth Mudstone Formation. A reconstruction geology immediately prior indicates failure occurred time when cliff line was c. 350 south its present position, possibly mid Holocene 5000 6000 year ago level sufficiently high re-erode Pleistocene line.