Devon County Geological Sites or Regionally Important Geological / Geomorphological Sites - RIGS Site reference no. SS50SE 1 Name: River Okement District: West Devon Parish: Exbourne National grid ref: 592 018 - 588 027 OS sheets: 1:50k 191 1:25k 1293 1:10k SS50 SE GS 1:50k 324 GridRef x y Lat Long SS591 022 259100 102200 50.80218 -4.000892 Locality description(address): River Okement west of Exbourne, from Jacobstowe Bridge to Cadham. Nature of site : River section with its associated river valley geomorphological features. Geological / Geomorphological features: The River Okement is deeply incised in Terrace deposits. The underlying rocks cropping out in the river are Permian conglomeratic sandstone dipping south. The dip steepens towards the northern end of the section where the Permian rocks are faulted against steeply dipping sandstone and shale of the Upper Carboniferous Crackington Formation. This E - W trending normal fault crosses the river [5883 0250] just south of the footbridge to Cadham Farm . The third and fourth river terraces can be seen in places above the river, also the remains of former river bluffs. The material of the terraces consisting granite cobbles , chert etc., carried from the flanks of Dartmoor to the south, is seen where fields are ploughed. At the northern end of the section a sharp bend in the Okement produces a river bluff and slip off slope. Reasons for registration as a Regionally Important Geological / Geomorphological Site : A readily accessible section along the valley of the Okement, showing good examples of geomorphological features, and the northern boundary fault of the Permian deposits filling the Crediton Trough. Site sensitivity: None. The observance of the countryside code is necessary on farm land. Safety: Generally safe for all. Access to rock outcrops along the river is difficult, and probably dangerous in conditions of high flow. Interest groups: Schools. Primary - Secondary - 6th Form . University. Undergraduate - Research Professional geologists - Amateur geologists - General public. Access and Parking: Parking for cars and minibuses on the bye-passed section of road at Jacobstowe Bridge. Signposted footpath northwards along the top of the river bank. The top of the Bank is fenced but 'fishing gates' give access in places. Date of assessment (V = visited) : V 12th November 1994 . R T Taylor. Site owner : 'Tarka Trail' public footpath. Other comments: References: Edmonds, E A. et al., 1968. Geology of the Country around Okehampton. Memoirs of the Geological Survey of Great Britain. HMSO. London. .