74 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. ^0, 



With the Upper Zone of the Great Oolite, the earliest Secondary 

 formation which does not thin away south-eastward, our investiga- 

 tions cease on this head, and I now propose to inquire what are the 

 probable positions of the Palaeozoic rocks under this district. 



I can here avail myself of the opinions of other authors, which 

 will render it unnecessary to dwell to a great length on this part 

 of the subject. 



§ 4. Probable Extension of the Coal-measures from Warwickshire to 

 the Thames Valley. — This is a subject on which it is necessary to 

 exercise much caution, on account of the interests involved. Mr. 

 Godwin- Austen has already stated his opinion of the probable 

 extension of the Coal-measures from the Coal-fields of Stafford and 

 "Warwick, to join that band which he considers to stretch along the 

 Thames Valley under the Chalk. Even if this be the case, there 

 may be interruptions in the form of bosses of Silurian or Cambrian 

 rocks, and the measures themselves may be generally unproductive 

 of valuable coal-beds. 



In fact, there are evidences that the Coal-measures become at- 

 tenuated towards the S.E., from phaenomena observable in the 

 Warwickshire Coal-field. At the southern extremity of the Coal-field, 

 south of Bedworth, all the coal-beds, which towards Atherstone are 

 more or less widely separated by sandstones and shales, become 

 united into one mass 30 feet thick*. At the same time the south- 

 easterly strike of the Coal-measures and Permian rocks in the 

 Warwickshire district shows that they tend to underlie Oxford- 

 shire and part of Northamptonshire; and the strike of the coal- 

 beds has been proved to continue in the same direction for a con- 

 siderable distance underneath the New Eed Sandstone f. Further 

 to the south, near Coventry, the Permian Beds slightly change 

 their strike towards the east, and, if there be any conformity between 

 this formation and the Coal-measures, which seems to be the case in 

 this district, the dip of the Coal-measures must be in the direction 

 of Oxfordshire. Of course beyond this district we have no further 

 means of judging by actual observation whether this direction of the 

 beds continues ; but it is satisfactory to find, at the last place where 

 the Coal-formation can be seen to the S.E., the beds tending to 

 underlie a district where we know that the superimposed formations 

 have become greatly lessened in depth. 



§ 5. Physical Geography of the Trias. — A. Land on the North 

 Atlantic Area. — At the close of the Permian Period, those dis- 

 turbances accompanied by marine denudation ensued which 

 changed the distribution of land and sea, and produced a high 

 degree of unconformity between the Permian and Triassic Rocks. 

 Their general effect was to extend the area of sea, and to contract the 

 land-surface, so that the British Islands presented the appearance 

 of a small polynesia, in place of a more or less connected line of 



* Geol. Survey Map, Sheet 63, S.W., and Vertical Sections, Geol. Survey, 

 Sheet 20. 



t As I am informed by my colleague Mr. Howell. See Geol. Map, Sheets 

 53, N.W.-63, S.W. ; and " Geology of the Warwickshire Coal-field," 1859. 



