Lyne Formation is part of the Border Group
The Lyne Formation is synonymous with the Cementstone Series of the Bewcastle district as defined by Garwood (1913). It equates with the Lower Border Group of Lumsden et al. (1967) and Day (1970), and is named after the River White Lyne at Bewcastle (Day, 1970). See also Lintern and Floyd (2000).
In the Northumberland Trough, the Lyne Formation comprises cyclical sequences of fine-grained subarkosic sandstone, siltstone, mudstone, and thin limestone in which thin oolitic pellet beds are characteristic components. In the Solway Basin, in the Easton 1 borehole (BGS Registration Number NY47SW/15) (NY 44124 71694) the formation is represented by the Easton Anhydrite Member, of grey or white anhydrite interbedded with limestone, shale, siltstone and sandstone.
The Lyne Formation limestones are typically peritidal, with the first incoming of marine limestones occurring later towards the north-east of the Northumberland Trough, north-east of Bewcastle. The sandstones were deposited from lobate deltas that migrated periodically along the basin axis from north-east to south-west (Leeder, 1974). In the Solway Basin, the Easton Anhydrite Member is predominantly of shallow water origin. The sediments were deposited in a rapidly subsiding basin, with restricted marine circulation, in which sedimentation and rapid burial is inferred to have kept pace with subsidence. Most of the anhydrite is likely to have had a subaqueous rather than a sabkha origin, the purer and thicker beds probably precipitating as gypsum in regionally extensive salinas.
Type sections of the constituent members include for the Easton Anhydrite Member, the Easton.1 borehole (see above) from 1054 to 2260 m depth (this is a partial type section since the base of the member is not proved); for the Southerness Limestone Member, the shore section at Southerness (NX 9690 5420 to 9740 5420); for the Lynebank Member, Ellery Sike (NY.5433.7584) to Nixontown (NY 5482 7550) on the River White Lyne; for the Cambeck Member, the River White Lyne (NY 5116 7300 to 5109 7322) at Bewcastle; for the Main Algal Member, Birky Cleuch (NY 5885 7540 to 5932 7538), Kirk Beck, Bewcastle; and for the Bewcastle Member, Ashy Cleuch (NY 5648 7698 to 5808 7665) upstream from Stockastead Quarry.
Lower and upper boundaries
The formation in the central part of the Northumberland Trough passes northward, by lateral facies change, into strata of the Ballagan Formation, Inverclyde Group (Figure.8, Column 11). In Annandale, the Hoddom No..2 Borehole (BGS Registration Number NY17SE/3) (NY 1641 7285) showed the Lyne Formation conformably overlying the Ballagan Formation at 139.84 m depth. The base of the Lyne Formation is not seen at Bewcastle (Figure.11, Column 2) or Kirkbean (Figure 10, Column 2) but it is presumed to rest conformably on the Ballagan Formation in these places. The base of the Easton Anhydrite Member is not seen, but seismic interpretation indicates the presence of ‘several thousands of feet’ of conformable strata below the succession in some parts of the Solway Basin (see Ward, 1997, p. 283).The upper boundary of the formation is locally unconformable and diachronous with the Fell Sandstone Formation in the central parts of the Northumberland Trough. At Bewcastle, the base of the latter is locally defined as the base of the Whitberry Band (WBB) (Figure 11, Column 2).
The top of the Easton Anhydrite Member is taken where numerous beds of anhydrite interbedded with limestones, shales, siltstones and sandstones give way to strata with variously algal, oolitic, peloidal, shelly, crinoidal and serpulid limestones, which may represent the Main Algal Member of the Lyne Formation. However, this has not been positively identified.
In the Bewcastle area, in the central part of the Northumberland Trough, the formation is at least 890.m thick. However, in Annandale, the Hoddom No..2 Borehole (see above) showed the Lyne Formation to be 37.22 m thick. In the Easton.1 borehole (see above) the Easton Anhydrite Member is more than 1153 m thick (base not seen).
Distribution and regional correlation
Northumberland Trough and Solway Basin: Langholm–Bewcastle, and Southerness. Seismic reflectors suggest that the top of the Easton Anhydrite Member extends at depth from west Cumbria eastwards to the flanks of the Bewcastle Anticline and beyond (see Ward, 1997, fig. 11).
Age and biostratigraphical characterisation
Late Tournaisian to Chadian (Waters et al., 2007, p..18). The limestones commonly contain stromatolites and vermetid gastropod bioherms and biostromes. In the west quasimarine shelly faunas contain abundant brachiopods (including Antiquatonia teres). Based on limited palynology, the Easton Anhydrite Member is considered to be early Visean in age.
- Garwood, E J.1913.The Lower Carboniferous succession in the north-west of England.Quarterly Journal of the Geological Society, Vol. 68, 449–596
- Lumsden, G I, Tulloch, W, Howells, M F, and Davies, A.1967.The geology of the neighbourhood of Langholm.Memoir of the Geological Survey of Great Britain, Sheet 11 (Scotland)
- Day, J B W.1970.Geology of the country around Bewcastle.Memoir of the Geological Survey of Great Britain, Sheet 12 (England and Wales)
- Lintern, B C, and Floyd, J D.2000.Geology of the Kirkcudbright–Dalbeattie district.Memoir of the British Geological Survey, Sheets 5W and 5E, part 6W (Scotland)
- Leeder, M R.1974.Lower Border Group (Tournaisian) fluviodeltaic sedimentation and palaeogeography of the Northumberland Basin.Proceedings of the Yorkshire Geological Society, Vol. 40, 129–180
- Ward, J.1997.Early Dinantian evaporites of the Easton-1 well, Solway Basin, onshore Cumbria, England. 277–296 in Petroleum geology of the Irish Sea and adjacent areas. Meadows, N S, Trueblood, S P, Hardman, M, and Cowan, G (editors).Geological Society of London Special Publication, No. 124.
- Waters, C N, Browne, M A E, Dean, M T, and Powell, J H.2007.Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore).British Geological Survey Research Report, RR/07/01