Abstract Quarrying Companies were a new type of unit first raised within the Royal Engineers in World War I. Thirteen served in northern France, on the Western Front: two from late 1916 (198 and 199 Quarrying Companies) and 11 more from 1917 (320–329 and 348 Quarrying Companies). Recruited from Great Britain, Ireland and the Channel Island of Guernsey, each consisted of four officers and 264 soldiers; over 3000 men in total, assisted by c . 4000 less skilled labourers. They were used to support the British Expeditionary Force by providing ‘stone’, mostly from existing quarries near Marquise, NE of the port of Boulogne. There they excavated Devonian and Carboniferous ‘limestones’ in the Ferques Inlier, relatively strong rocks within a region of wide Mesozoic and Cenozoic outcrop. As the British Expeditionary Force expanded to a peak of five armies and c . 1.5 million troops, ‘stone’ was required for the enhancement or repair of the roads, railways and associated facilities that formed a crucial element of its infrastructure, essential for the efficient movement of soldiers and their copious supplies of food, stores and ammunition. The requirement ceased soon after the end of hostilities and all Quarrying Companies Royal Engineers were disbanded in 1919.

The late Precambrian/early Cambrian Monian basement to the lower Paleozoic cover in Anglesey does not form one coherent stratigraphic unit but is divisible into at least three separate suspect terranes. Where they are exposed, the boundaries to these terranes range from ductile shear zones to brittle faults, all of which have an undetermined amount of displacement. Terrane 1 is represented by the Monian Supergroup: a thick sequence of marine sedimentary rocks with subordinate basic volcanic rocks, gabbros, and serpentinites, overlain by olistostromic mélange. Terrane 2 is identified as the Coedana Complex of central Anglesey: high-grade gneisses and the ca. 600-Ma Coedana Granite with an associated hornfels. Terrane 3 is represented by the southeast Anglesey schist belt and includes the ca. 550 to 560-Ma Anglesey blueschists. These suspect terranes are bounded to the southeast by the Menai Strait Fault System, to the southeast of which rocks of the Sarn Complex are placed within a separate terrane which may represent the northwest margin of the Avalon terrane in Britain. Terrane 1 and possibly terrane 2 are traceable into southeast Ireland (Cullenstown Formation and Rosslare Complex). Monian terranes are not known from elsewhere within the British Isles, although broadly coeval rocks occur in different terranes as the Avalonian/Cadomian rocks of southern Britain and the Channel Islands, and the Dalradian Supergroup of Scotland and northwest Ireland. No Monian rocks have yet been identified from the Tornquist line in the east, whereas several attempts at correlation have been made between Anglesey and the eastern seaboard of North America. Such attempts have failed to appreciate that there is not one “Mona Complex,” but a collage of disparate terranes, some of which are juxtaposed by shear zones comparable in scale to major crustal shears developed along transcurrent plate boundaries.