| Computer Code: |
BLEA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Caradoc Series (O4)
— Caradoc Series (O4) |
| Lithological Description: |
Massive eutaxitic lapilli-tuffs containing abundant pumice and nonvesiculated juvenile clasts; zoned andesitic to rhyodacitic composition; thin rhyodacite at base; laminated/bedded sandstones separate some igneous units. |
| Definition of Lower Boundary: |
Placed at upward change from sandstone of the Broom Farm Formation to eutaxitic lapilli tuff. |
| Definition of Upper Boundary: |
At the reworked top of thick, massive welded tuffs at this change to thinner sheets of generally lithic rich lapilli tuffs of the Brown Bank Tuff Formation. |
| Thickness: |
c.416m (uncorrected for structural dip or borehole deviation from vertical). 201m, 322m, 200m proved but unbottomed in boreholes 4, 5 and 10A respectively. |
| Geographical Limits: |
Seen in Sellafield boreholes 2 (NY00SE/28), 4 (NY00SE/29), 5 (NY00SE/30), 10A (NY00SW/38). |
| Parent Unit: |
Borrowdale Volcanic Group (BVG)
|
| Previous Name(s): |
Bleawath Formation
(-64)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Sellafield Borehole No 2, BGS Registered No NY00SE/28, 1066.50m - 1482.37m below Rotary Table Elevation, 1001.30m - 1417.17m 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 |
