| Computer Code: |
SYCM |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Bajocian Age (JB)
— Bajocian Age (JB) |
| Lithological Description: |
Grey mudstone, yellow-grey siltstone and yellow weathering, fine- to coarse-grained, (fluvial, fluvio-deltaic and paralic lithofacies). Sandstones are commonly cross-bedded with sharp erosional bases and channel-fill bedforms. Thin coal seams, seatearth mudstone and nodular sideritic ironstone beds are present locally. Plant fragments and plant rootlets are common in some beds. |
| Definition of Lower Boundary: |
The lower boundary is conformable, or disconformable, at the abrupt upward transition from fossiliferous (marine) mudstone and ripple cross-laminated sandstone of the Eller Beck Formation to to cross-stratified, plant debris-rich sandstone, siltstone and mudstone of the Sycarham Member (Cloughton Formation). |
| Definition of Upper Boundary: |
The upper boundary is conformable, taken at the abrupt transition from sandstone, siltstone and mudstone with plant remains (Sycarham Member) to marine (Lebberston Member) strata comprising pale grey, shelly ooidal limestone ("Whitwell Oolite" facies; Howardian Hills [SE 72 65]) or yellow, shelly calcareous sandstone with bivalves ("Millepore Bed" facies; Yons Nab [TA 084 844], south of Scarborough). |
| Thickness: |
About 50m on the North Yorkshire coast between Whitby and Cloughton Wyke [TA 020 950]; 20 to 30m (thinning southwards) on the western margin of the North Yorks Moors and Hambleton Hills (Powell et al., 1992; Frost, 1998). |
| Geographical Limits: |
North York Moors and Howardian Hills; well exposed in several coastal cliff sections between Whitby [NZ 890 115] and Saltwick Bay [NZ 917 108] and south from Blea Wyke Point [NZ 995 010], near Ravenscar, to Hayburn Wyke [TA 010 971] and Sycarham Cliff [TA 021 957]. Offshore, the formation is equivalent, in part, to the Wroot Formation of the West Sole Group (Lott and Knox, 1994). Where the marine Lebberston Member (Cloughton Formation) is absent (generally in the north of the Cleveland Basin) the non-marine strata (Sycarham and Gristhorpe members) are termed Cloughton Formation (undivided). |
| Parent Unit: |
Cloughton Formation (CLH)
|
| Previous Name(s): |
Lower Estuarine "Series" [Obsolete Name And Code: See CLH, GRF, SWK And EBB]
(LET)
|
| Alternative Name(s): |
Middle Deltaic Series [Obsolete: use CLH, GRPE]
|
| Stratotypes: |
| Type Section |
The section at Sycarham Cliff, also known as Roger Trod [TA 021 957] (Hemingway and Knox, 1973). Yellow weathering, bioturbated, fine- to medium-grained sandstone and siltstone of the underlying Eller Beck Formation are overlain by yellow-grey weathering, cross-bedded, medium-grained sandstone and siltstone with scattered plant fragments and rootlets. Laterally impersistent channel sandstone bedforms are common, together with level-bedded mudstone and ripple cross-laminated siltstone. The term "Hawsker Member" (Hemingway and Knox, 1974) was proposed by these authors for the non-marine strata (c.f. Cloughton Formation) where the marine Lebberston Member is absent (generally in the north of the Cleveland Basin). The term "Hawsker Member" is redundant because the non-marine strata (Sycarham and Gristhorpe members) are represented by the Cloughton Formation (undivided). |
| Reference(s): |
| Hemingway, J E. 1974. Jurassic. 161-233 in Rayner, D H and Hemingway, J E (eds), The geology and mineral resources of Yorkshire. (Leeds: Yorkshire Geological Society.) |
| Lott, G K and Humphreys, B. 1992. The stratigraphy and petrology of Middle Jurassic (Ravenscar Group) sediments in cored boreholes from the North Yorkshire coast. Proceedings of the Yorkshire Geological Society, Vol.49, 23-40. |
| Rawson, P F and Wright, J K. 2000. The Yorkshire Coast. Geologists' Association Guide No.34. (London: The Geologists' Association.) 130pp. 3rd Edition. |
| Cope, J C W, Duff, K L, Parsons, C F, Torrens, H S, Wimbledon, W A and Wright, J K. 1980. A correlation of Jurassic rocks in the British Isles. Part 2: Middle and Upper Jurassic. Geological Society of London Special Report, 15, 73pp. |
| Hemingway, J E and Knox, R W O'B. 1973. Lithostratigraphical nomenclature of the Middle Jurassic strata of the Yorkshire Basin of north-east England. Proceedings of the Yorkshire Geological Society, Vol.39, 527-535. |
| Butler, N, Charnock, M A, Hager, K O, and Watkins, C A. 2005. The Ravenscar Group: a coeval analogue for the Middle Jurassic reservoirs of the North Sea and offshore Mid-Norway. 43-53 in Recent Developments in Applied Biostratigraphy. Powell, A J, and Riding, J B (editors). The Micropalaeontological Society, Special Publications. |
| Rawson, P F and Wright, J K. 1995. Jurassic of the Cleveland Basin, North Yorkshire. 173-208 in Taylor, P D (Ed.) Field Geology of the British Jurassic. (London: Geological Society.) |
| Frost, D V. 1998. Geology of the country around Northallerton. Memoir of the British Geological Survey, Sheet 42 (England and Wales). |
| Lott, G K and Knox, R W O'B. 1994. 7. Post-Triassic of the Southern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. British Geological Survey, Nottingham. |
| Powell, J H, Cooper, A H C and Benfield, A C. 1992. Geology of the country around Thirsk. Memoir of the British Geological Survey, Sheet 52 (England and Wales). |
| Kantorowicz, J D. 1985. Petrology and diagenesis of Middle Jurassic clastic sediments, Ravenscar Group, Yorkshire. Sedimentology, Vol.32, 833-853. |
| Knox, R W O'B, Howard, A S, Powell, J H and van Buchem, F S P. 1991. Lower and Middle Jurassic sediments of the Cleveland Basin N.E. England: Shallow marine and paralic facies seen in their sequence stratigraphic context. Field Excursion Guide, No.5; 13th International Sedimentological Congress, Nottingham, UK. 1990. 66pp. |
| Fox-Strangways, C. 1892. Jurassic rocks of Britain, Vols 1 and 2, Yorkshire. Memoir of the Geological Survey of Great Britain. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E035
E044
E052
E053
E054
E063
|
