Page:VCH Surrey 1.djvu/55

 GEOLOGY It has been surmised that the buried Coal Measures may extend beneath some portion of the county, but the factors bearing on the question are so complex and the evidence at present in hand so scanty, that further deep boring can alone give proof or disproof to the supposition. Since the Richmond and Streatham borings are as yet the only instances in Surrey where rocks older than the Jurassic have been pierced, it is the more unfortunate that doubt should exist as to the age of these rocks in both places. No fossils were obtained from them in either case, so that we have only their general aspect on which to base an opinion, and this is not sufficiently distinctive to determine the point with any certainty. By some geologists they are thought to belong to the New Red or Triassic system that is to say, to a system newer than the Coal Measures : while other geologists have inclined to the view that they more nearly resemble the Old Red or Devonian rocks, in which case they will be older than the Coal Measures, a difference of opinion of course very seriously affecting the question as to the most likely quarter in which to search for Coal Measures. The main point has, however, been clearly established, that in the northern part of Surrey rocks unconformably underlying the Jurassics are within comparatively easy reach of exploration by borings ; and such exploration, at some time or other, will no doubt be undertaken. More might be said as to the bearing of the evidence from deep borings outside the county limits on the probable range of its concealed Jurassic rocks, but to enter more fully into the subject would be to transgress the bounds and scope of this article. We will now therefore ascend from the depths to follow the fortunes of the land-surface after the newest of its ' solid ' strata was laid down. ELEVATION AND DENUDATION We have seen that throughout the building up of its strata the area was now rising, now sinking, and probably never for long quite stationary. But from the Wealden onward to the close of the Eocene these movements were all of a simple character, elevating or depressing the whole tract without seriously disturbing its horizontality. Some slight tilting and sagging there doubtless was, by which during sub- mergence the waters became relatively deeper or shallower in one place than in another ; but this was never sufficiently sharp to destroy the general parallelism of the successive deposits in any particular spot, or, to use technical parlance, to develop strong unconformability between any of the separate formations. But subsequently, during the Miocene Period, there came a time of storm and stress in the earth's crust, which affected the British Islands in common with the greater part of the European continent : a time of mountain-building in some quarters, as for instance in the Alps : and of great volcanic eruptions and outpourings of lava in others, as in Scotland and Ireland. And during this time of disturbance the rocks of the south-east of England were forced by lateral pressure into broad waves 21