Blue Lias Floor Names

William Smith, the Father of Stratigraphy, was a poor son of the yeomanry, and could not be admitted to the genteel Geological Society. When he published his geological map of 1801, rather than use the Latin and Greek favoured by academics, he gave various formations names learned from quarry men - "a system of names almost barbarous to ears polite", they said.

One of these was the Lias. Dictionaries explain this name as derived from Old French "liois" or "liais" meaning lees or dregs, or even Old Celtic "lech" meaning slabby stone, but more probably it is just a south Mercian dialect pronunciation of "layers", reflecting the obvious nature of this part of the Lower Jurassic in Britain. Notwithstanding their barbarous nature, many of Smith's formation names became established in British geology and continue in use today.

The lowest part of the Lias, called in many places the "Blue Lias" usually consists of alternations of shale and limestone. The limestone was quarried for building stone, paving slabs and lime. Taking a leaf out of Smith's book, various geologists researching the detailed lithology of the Blue Lias noted that quarrymen gave names to the individual limestone layers or "floors", and faithfully reproduced these in their descriptions of the succession.

The names of these limestone strata are intriguing terms often of difficult etymology, and are somewhat localised but have a definite geographical reach that indicate the mobility of quarry men, and also perhaps some cultural diffusion. The names were passed on through the generations as long as the "floors" were selectively quarried. In cement manufacture, in later years, the expensive process of hand extraction of individual layers has been abandoned in favour of an indiscriminate mixing of the layers, usually by blasting, and in these circumstances, the folk memory of floor names has faded away.

I have tried to assemble as many of these names as I can. As elsewhere in this website, there are some huge lacunae, which I hope, somewhat unrealistically, to fill, so the page will grow. I have put them in geographical order along the Lias outcrop, proceeding from Dorset to Nottinghamshire. The names are arranged from the topmost (youngest) stratum, moving downwards.

Lyme Regis

On the coast near the Devon/Dorset border, the Blue Lias near Lyme Regis has been extensively studied, because the whole sequence is exposed in cliffs and on the beaches. The bed names are very well known, because the area has been the subject of a succession of academic studies, and most authors have used the old names for ready identification of the beds. The most significant and definitive early studies were by Lang (note 1). Named strata most exploited were restricted to the Bucklandi and Angulata zones. The limestone layers were named:

Bridgwater District

Many lime and cement plants operated in the Bridgwater area, mostly taking raw material from the Polden Hills to the north. Cement was made from a few selected beds, with little or no chemical control. The quarry of John Board &Co. at Puriton was described and the limestone layers were named:

Aberthaw and Rhoose Point

The famous Blue Lias deposits to the west of Barry, although often compared with other locations (note 2), are actually quite distinct from all other Blue Lias limestones, possessing particularly favourable properties (note 3). Unfortunately, no bed names have come to light, although they certainly existed in the context of lime production. The cement plants used the limestone beds indiscriminately, so were unlikely to retain names.

Penarth

The range of lower Blue Lias beds were used selectively before the 1920s, and were probably named, but the names have not come to light.

Wilmcote

Cement was not made at Wilmcote, but the selected beds were used for different grades of lime, by various manufacturers including Greaves, who made cement at Harbury. The Wilmcote beds are absent further north.

Harbury, Southam and Stockton

Rugby and Newbold

The Lias at Rugby was originally selectively quarried for various lime grades and cement. The Victoria Quarry, to the northeast of the Rugby plant, was remarked upon by many writers as a spectacular section, with a 22 m face showing more than 35 limestone beds. The Newbold quarry showed more than 30 in a face up to 16 m high. The beds were all named. Woodward mentions "Knotty Rock", "Big Jumbler" and "Cat Heads", but I have yet to find a comprehensive sequential list.

Barrow

The basal Lias at Barrow on Soar and Sileby has been used for hydraulic lime for centuries. It consisted of comparitively few limestone beds, and was often mined underground from below the overlying shale beds. Barrow is at the southern extreme of the Northern Province of the Lower Lias, where it is called the Scunthorpe Mudstone member, rather than the Blue Lias. The quarry at Kilby Bridge, south of Leicester, used by Barrow in its later years, was in the Southern Province and was more similar to the Rugby Lias. At Barrow, the limestone layers were named:

Barnstone

The Barnstone quarry has floor names very similar to those at Barrow. The quarry was opened by people with family connections in Barrow. The deposit was extracted open-cast and was worked to the bottom of the formation. The limestone layers were named:

NOTES

Note 1. W. D. Lang, "The Blue Lias of the Devon and Dorset Coasts", Proc. Geol. Assoc., 35, pp 169-184, 1924. The names were recorded earlier in Wright, Quart. J. Geol. Soc., 16, pp 401-.

Note 2. For instance, according to de la Beche (1839), Smeaton, when he built the Eddystone Ligfhthouse, "sent round the Land's End to Aberthaw for limestone, whereas he could have procured equally good material from Lyme Regis." This was in fact very far from the case.

Note 3. The Lias here has a much higher limestone/shale ratio than elsewhere, and has a high silica ratio, which confers superior durability.