Abstract So we turn to the work done in the twentieth century on the elucidation of the sequence and structure of the rocks of Jonathan Otley’s third major subdivision of the Lakeland rocks – up to the time of the establishment of the ‘Lakeland Project’ in 1982, and with a preliminary forward glance to the end of the century. The rocks of ‘Otley III’ consist of limestones, mudstones, shales, slates, grits and conglomerates, with one substantial igneous unit, the Yarlside (or Stockdale) Rhyolite, which runs westwards from the Shap district, parallel with the strike of other rocks low in ‘Mr Otley’s third great physical subdivision’ as Sedgwick (1852 b , p. 137) called the unit. The ‘Otley III’ rocks are of generally quite low relief, but, as mentioned previously, many are highly cleaved, the cleavage frequently being more pronounced than the bedding. As we have seen, some of the beds are highly fossiliferous (or were so before they became the subject of close attention by generations of amateur and professional geologists, dealers, or even historians of geology). There is (or once was) a rich fauna of graptolites, molluscs, corals, cystoids and trilobites, and in the past more exotic types like starfish were reported by Sedgwick. As we have seen, the lowest part of ’Otley III’ was formerly called the Coniston Limestone (Series) and was initially likened (by Sedgwick) to the Bala Limestone in Wales. Later it was placed in the Caradoc subdivision of the Ordovician; and still later it was subdivided and the

Abstract We have already seen in Chapter 13 how the stratigraphic divisions of the Windermere Group or Supergroup were elaborated in the latter part of the twentieth century, but there are still major questions to be asked about this large basin of sediments, its structure and its tectonic history. In particular, why is there the strange contact with the Borrowdale Volcanics, with the Windermere sediments evidently unconformable thereto, but also reared up against it, as at Timley Knott (see Fig. 13.1 ), with other parts of the contact also displaying significant faulting. How did this come about? Also, did the Windermeres 1 formerly go right over the BVG (which they seem, from Timley Knott, to have been trying to do)? Perhaps they did, given the evidence of the Drygill Shales or the occurrence of Coniston Grits in the Mell Fell Conglomerate of the northern Lakes. Or did they ‘go round’ the mountains only? If they went over the Volcanics, were they folded over, or were they deposited in such a thick sequence that they smothered them entirely? Or were the Volcanics largely eroded away before the deposition of the Windermeres? The ‘Otley III’ sediments are evidently thick. But how thick? And what were the reasons, in terms of the tectonic history of northern England, for the formation of a basin such as could accommodate the large mass of sediments? Where did these sediments originate? And then what caused the subsequent inversion of the basin so as to bring the