- 1 Sellafield Member (SELF)
- 2 References
- Kirklinton Sandstone (Dixon et al., 1926)
- Ormskirk Sandstone Formation (Institute of Geological Sciences, 1977)
Derivation of name
From the Sellafield area of Cumbria
NY 04506 00184: Sellafield Borehole 13B, Cumbria. BGS Registered No. NY00SW/42, 0 to 176.42 m.
- NY 0280 0310 to 0255 0274: River Calder, Cumbria (Barnes et al., 1994).
- NY 034 012: Seascale Scar, Cumbria (Gregory, 1915).
Very scarce exposures in the Sellafield–Seascale–Drigg area, west Cumbria.
The dominant lithology is a red-brown, weathering to orange-brown, fine-grained, well-sorted sandstone with well-rounded grains of aeolian origin. It is commonly cross-bedded. This aeolian dune facies is interbedded with an interdune facies comprising well-cemented, fine-to medium-grained, poorly sorted sandstone with common wavy silty laminae. Small-scale convolutions, loading and dewatering structures are common.
The lower boundary is taken at the sharp upward change from fine-to coarse-grained fluvial sandstone in the underlying part of the Helsby Sandstone Formation to medium-grained, aeolian sandstone. In borehole geophysical logs it is marked by an upward decrease in gamma-ray values and an upward decrease in sonic velocity. Both log signatures are more serrated than in the underlying part of the Helsby Sandstone Formation.
The upper boundary is not seen but will be marked by the incoming of dominantly red-brown mudstones and siltstones of the Mercia Mudstone Group.
The thickest known sequence is 176.42 m, in the Sellafield 13B Borehole.
Anisian (early Mid Triassic)
Helsby Sandstone Formation (pars.)
The member only crops out between Drigg and Sellafield on the Cumbrian coast.