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Geosource>BobMcIntosh at 10:33, 27 June 2015

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== Sellafield Member [http://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=SELF (SELF)]==

=== Previous nomenclature ===
* Kirklinton Sandstone (Dixon et al., 1926)
* Ormskirk Sandstone Formation (Institute of Geological Sciences, 1977)

=== Parent unit ===
[[Helsby Sandstone Formation]]

=== Derivation of name ===
From the Sellafield area of Cumbria

=== Type section ===
NY 04506 00184: Sellafield Borehole 13B, Cumbria. BGS Registered No. NY00SW/42, 0 to 176.42 m.

=== Reference sections ===
* NY 0280 0310 to 0255 0274: River Calder, Cumbria (Barnes et al., 1994).
* NY 034 012: Seascale Scar, Cumbria (Gregory, 1915).

=== Extant exposures/sections ===
Very scarce exposures in the Sellafield–Seascale–Drigg area, west Cumbria.

=== Lithology ===
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.

=== Lower boundary ===
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.

=== Upper boundary ===
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]].

=== Thickness ===
The thickest known sequence is 176.42 m, in the Sellafield 13B Borehole.

=== Age ===
Anisian (early Mid Triassic)

=== Equivalent unit ===
Helsby Sandstone Formation (pars.)
=== Geographical extent ===
The member only crops out between Drigg and Sellafield on the Cumbrian coast.
=== Subdivisions ===
None

== References ==
<references/>
[[Category:Triassic lithostratigraphical nomenclature]]

Sellafield Member - Revision history

Dbk: 1 revision imported

Geosource>BobMcIntosh at 10:33, 27 June 2015