186 LAMPLUGH : NOTES ON THE WHITE CHALK OF YORKSHIRE. 
its westerly extension thinned off towards a shore-line where deposits 
of detrital matter like those of various parts of the European Continent 
marked the original limits of the Upper Cretaceous Sea. 
However this may be, one thing is certain, that the Chalk has 
originally extended much farther to the northward and westward in 
Yorkshire than it does nowadays, and that over wide areas it has been 
entirely removed by denudation. There are in the North of England 
no "solid" beds above the Upper Chalk, the whole of the Tertiary 
sediments being unrepresented. We have, therefore, no indications 
within the area to guide us in framing an idea of the progress of 
events between the close of the Cretaceous Period and the begmning 
of Glacial conditions. By looking farther afield, however, to the South 
of England and to the opposite shores of the North Sea, we may gain 
sufficient information to speculate upon the probable sequence of 
conditions during this great interval. 
While the uppermost layers of the Chalk were in the process of 
deposition a slow elevating movement seems to have set in, which 
either before or in very early Eocene times quietly brought up the 
area above sea-level. The erosion of the Cretaceous strata then com- 
menced, and went on with increasing rapidity as the land gained 
gradually in elevation. Minor fluctuations of level occurred during 
the later stages of the Eocene and the earlier Oligocene, but these 
were not of sufficient importance to alter the general character of the 
period so far as this area is concerned, and the wasting of the land 
continued. The culmination of these geocratic movements occurred 
in Miocene times, when the district participated to some extent in 
those vast disturbances which affected the whole of the Eurasian 
continent. 
The earth-pressure in some regions built up high mountain- 
chains, and in others caused outburst of volcanic activity of extreme 
magnitude. In the south of England it threw the Secondary rocks 
into broad folds, and locally into sharp contortions ; and such dis- 
disturbances of the Chalk in the north of England as are revealed 
in the Staple Nook and other sections, may with every probability be 
referred to the same series of forces. From the character of the 
contortions we gather that they must have been formed under a great 
