Computer Code: |
YOT |
Preferred Map Code: |
notEntered |
Status Code: |
Full |
Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
Lithological Description: |
Welded tuffs and lapilli-tuffs with intercalations of volcaniclastic sandstone; interpreted as two sheets of rhyolitic ignimbrite and one of dacitic ignimbrite. |
Definition of Lower Boundary: |
Taken at the base of the spherulitic, rhyolitic welded tuff that constitutes the Sella Park Member. This is a major change from dominantly volcaniclastic sandstones of the underlying Newton Manor Formation to the ignimbrite sequence of the Yottenfews Tuff Formation. |
Definition of Upper Boundary: |
Not seen in its original form as the formation is unconformably overlain by Carboniferous strata. |
Thickness: |
194m+ (uncorrected for structural dip or borehole deviation from the vertical). Thickness includes a 49.3m-thick sill. |
Geographical Limits: |
Sellafield borehole No.7A only. |
Parent Unit: |
Borrowdale Volcanic Group (BVG)
|
Previous Name(s): |
Yottenfews Formation [Obsolete Name and Code: Use YOT]
(-4990)
|
Alternative Name(s): |
none recorded or not applicable
|
Stratotypes: |
Partial Type Section |
Sellafield borehole No.7A, BGS Registered No. NY00SE/36, 577.83 - 718.15m below Rotary Table Elevation, 524.77 - 718.44m below OD. |
Reference(s): |
Millward, D, Beddoe-Stephens, B, Williamson, I T, Young, S R, and Petterson, M G. 1994. Lithostratigraphy of a concealed caldera-related ignimbrite sequence within the Borrowdale Volcanic Group of west Cumbria. Proceedings of the Yorkshire Geological Society, Vol.50, part 1, 25-36. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
none recorded or not applicable |