Chapter 18 Tertiary uplift

Abstract

Abstract It is one thing to tell the story of the idea about how the rocks of the lake District were formed, but what happened to them after they came into being? In this chapter, I shall say something about this important issue. One might think that the mountains that we see in the Central Fells have been there ever since the Ordovician, and we are simply observing their eroded remnants. In a sense this is true. The volcanologists do think that we are able to examine, in the field, the eroded interiors of volcanoes. Are we able to do so because erosion has proceeded to such an extent that their very 'guts' are now visible? Presumably that is so, but why, then, are the 'guts' 'up in the air' for our inspection? Uplift can be expected because of the buoyancy of the underlying granites, but is that the whole story? And, presuming there was substantial uplift at some stage, when did that uplift occur, and are there causes other than isostatic forces? These issues will be considered in the present chapter, which covers the geological history of the Lakes subsequent to the 'big crunch', which is thought to have occurred in the Devonian, through to the glacial epoch of the Pleistocene. A review of matters relating to the presumed former sedimentary cover of Lakeland and the techniques for estimating its thickness has been given by Douglas Holliday in his Presidential Address to the Yorkshire Geological Society at York on 5