| Computer Code: |
REDF |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Ludfordian Age (SD)
— Ludfordian Age (SD) |
| Lithological Description: |
Mainly red mudstones and sandstones exposed on the cliffs and rocky foreshore at the northern end of Albion Sands [SM 771 077]. The formation comprises red to purple mudstones/siltstones and red, purple and greyish pink, typically fine-grained sandstones.
Dryland alluvial environments with deposition in low-sinuosity ephemeral sand-bed channels, point bar lateral accretion and unconfined sheetfloods. The mudstones represent floodplain deposits subjected to pedogenic vertisol development as well as fluvial deposition of mud aggregates (Hillier and Williams, 2004).
Hillier and Williams (2004) reported a late Ludfordian age based on a trilete spore assemblage. |
| Definition of Lower Boundary: |
At the type section, the lower boundary is conformable, where the basal red mudstones of the Red Cliff Formation rest on grey deltaic deposits of the Gray Sandstone Formation (Hillier, 2000; Hillier and Williams, 2004). At Red Cliff, calcretised red mudstones interdigitate with grey sandstones with inclined heterolithic stratification of the Gray Sandstone Formation (Hillier, 2000). |
| Definition of Upper Boundary: |
The upper boundary is placed at the top of red mudstones, where they are overlain by pale quartz-rich sandstones of the Albion Sands Formation. |
| Thickness: |
Thicknesses range from 17 m at Lindsway Bay and 50 m at Albion Sands to 55 m at the type section of Red Cliff (Hillier and Williams, 2004). |
| Geographical Limits: |
Pembrokeshire, north of the Ritec Fault. |
| Parent Unit: |
Milford Haven Subgroup (MIH)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Albion Sands [SM 771 077], to the north of Gateholm Island west-south-west of Marloes. |
| Reference Section |
Northern side of the embayment of Red Cliff [SM 789 068] 2 km south-east of Albion Sands. |
| Reference Section |
Lindsway Bay [SM 8425 0665–8445 0640]. |
| Reference(s): |
| Barclay, W J, Davies, J R, Hillier, R D, and Waters, R A. 2015. Lithostratigraphy of the Old Red Sandstone successions of the Anglo-Welsh Basin. British Geological Survey Research Report, RR/14/02. 96pp. |
| Allen, J R L, and Williams, B P J. 1978. The sequence of the earlier Lower Old Red Sandstone (Siluro - Devonian) north of Milford Haven, southwest Dyfed (Wales). Geological Journal, Vol. 13, 113-136. |
| Hillier, R D. 2000. Silurian marginal marine sedimentation and the anatomy of the marine-Old Red Sandstone transition in Pembrokeshire, SW Wales. 343-354 in New perspectives on the Old Red Sandstone. Friend, P F, and Williams, B P J (editors). Geological Society of London Special Publication, No. 180. |
| Hillier, R D, and Williams, B J P. 2004. Sedimentation and tectonics: the marine Silurian-basal Old Red Sandstone transition in southern Pembrokeshire, UK. Geological Journal, Vol. 39, 237-256. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
