| Computer Code: |
DAUG |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Gorstian Age (SG)
— Emsian Age (DE) |
| Lithological Description: |
Mainly comprises a coarsening-upwards offlap dryland succession of, successively, coastal plain, alluvial floodplain and alluvial fan deposits.
The lower part of the group (Milford Haven Subgroup) records mainly successively coastal plain, alluvial floodplain and alluvial fan dryland deposition in a semi-arid climate. Earlier wetland shallow lake and debris-flow-dominated alluvial fans are represented by the Trichrug Formation. Most of the deposits were derived from the north, but the Ridgeway Conglomerate Formation was derived from the south. The Cosheston Subgroup represents fluvial deposition in sand- and gravel-bed, high-energy braided and meandering streams, as well as by sheet flooding and floodplain mud and silt deposition. |
| Definition of Lower Boundary: |
It is placed at the first appearance of red (or green) continental/terrestrial beds. In the Marloes Peninsula of south-west Pembrokeshire this is dated as late Ludlow (Hillier, 2000; Hillier and Williams, 2004) and placed at the conformable junction of the tidal/estuarine deposits of the Wenlockian Grey Sandstone Formation and the overlying red alluvial facies of the Red Cliff Formation. Locally, there is an unconformable base, as in Pembrokeshire south of the Ritec Fault, where red and green beds of the Freshwater East Formation overlie the Wenlockian Gray Sandstone Formation (formerly Gray Sandstone Group; Hillier and Morrissey, 2010). Elsewhere in south Wales and the Welsh Borderland, the base of the Old Red Sandstone has been traditionally placed at the base of the Ludlow Bone Bed Member of the Downton Castle Sandstone Formation. It is here placed at the base of the Temeside Mudstone Formation, or in its absence, at the base of the Raglan Mudstone Formation. In the Sawdde Gorge near Llandovery in south-central Wales, the base of the Trichrug Formation (Davies et al., 2008) is taken as the local base of the Daugleddau Group. |
| Definition of Upper Boundary: |
The upper boundary of the group is placed at the top of the highest beds below the Acadian unconformity. |
| Thickness: |
Up to about 4400 m. |
| Geographical Limits: |
Widely throughout south and central Wales, the Forest of Dean, the Bristol district, Mendips, Welsh Borderland, West Midlands and Anglesey. |
| Parent Unit: |
Old Red Sandstone Supergroup (ORS)
|
| Previous Name(s): |
Lower Old Red Sandstone Group
(LORS)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| 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. |
| Davies, J R, Hillier, R D, and Waters, R A. 2008. Ludlovian wetlands of Wales. Geoscientist, Vol. 18, No. 4, 24-25. |
| 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 Morrissey, L B. 2010. Process regime change on a Silurian siliciclastic shelf: controlling influences on deposition of the Gray Sandstone Formation, Pembrokeshire, UK. Geological Journal, Vol. 45, 26-58. |
| 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. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
