Computer Code: |
FLH |
Preferred Map Code: |
FlH |
Status Code: |
Full |
Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
Lithological Description: |
Andesitic tuff and lapilli-tuff (eutaxitic to parataxitic). At least three welded ignimbrite sheets, locally separated by thin beds of sandstone. Side Farm Member comprises poorly sorted beds of lapilli-tuff and pyroclastic breccia. |
Definition of Lower Boundary: |
Taken at the base of the sequence of homogeneous, thick, generally lithic - poorly welded tuffs, above the Brown Bank Ignimbrite Formation, which is composed of thinner sheets of lithic-rich andesite and rhyolitic lapilli tuff. Locally a coarse lithic-rich lag-breccia occurs at the base of the lowest member. |
Definition of Upper Boundary: |
Not seen, but mapped at the change from densely welded tuff to a mixed sequence of lithic-rich tuff and parataxitic tuff of the Loweray Formation. |
Thickness: |
403m in type section; 506m in Sellafield BH No.4 (NY00SE/29). Thicknesses are incomplete and uncorrected for dip, as boreholes deviated from vertical. |
Geographical Limits: |
Crops out east of Gosforth, Cumbria, as far as the Thistleton Fault (Lake District Boundary Fault). Also proved in Sellafield boreholes 2 (NY 00SE/28), 4 (NY00SE/29), 5 (NY00SE/30), 10A (NY00SW/38), 11A (NY00SE/34), 12A (NY00SW/39); RCF1 (NY00SE/35), RCF2 (NY00SE/36), RCF3 (NY00SE/37), RCM3 (NY00SE/39), PRZ1 (NY00SE/45), PRZ2 (NY00SE/44) and PRZ3 (NY00SE/42). |
Parent Unit: |
Borrowdale Volcanic Group (BVG)
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Previous Name(s): |
Fleming Hall Formation [Obsolete Name and Code: Use FLH]
(-3406)
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Alternative Name(s): |
none recorded or not applicable
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Stratotypes: |
Reference Section |
Sellafield Borehole No. 5, (BGS No. NY00SE/30), 489.83-892.42m beneath Rotary Table, 404.20m-806.79m below OD. |
Type Area |
Type area on Table Rock, 1.8km east of Gosforth, Cumbria. |
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. |
Beddoe-Stephens, B, and Millward, D. 2000. Very densely welded, rheomorphic ignimbrites of homogeneous intermediate calc-alkaline composition from the English Lake District. Geological Magazine, Vol. 137, 155-173. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E037
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