536 PRINCIPLES OF STRATIGRAPHY 



upon the final recession a climate favoring a luxuriant growth of 

 plant life succeeded, as testified to by the coals of the overlying 

 Ecca formation. "Demonstrably marine deposits are nowhere asso- 

 ciated with the Dwyka," not even where it "repeatedly reaches the 

 shore of the Indian Ocean" ; but marine Devonic fossils occur in 

 the Bokkeveld series 2,500 feet or more below the basal member of 

 the Dwyka in the Karoo district, while between them lies the con- 

 formable Witteberg series, forming the transition from marine to 

 glacial continental. The structural evidence shows that mountains 

 were absent at this time, though high lands existed which supplied 

 the material of the Karoo formation. 



Davis has presented the facts which show that neither great 

 elevation nor changes in land area or land form were able to produce 

 a glacial climate in subtropical South Africa, nor could any conceiv- 

 able arrangement of ocean currents produce it. General refrigeration 

 alone, either by a decrease of solar radiation or by a change in the 

 constitution of our atmosphere, without shifting of wind belts, 

 would have to be so extreme as to reduce the summer temperature 

 of South Africa to such an extent that the summer rains would be- 

 come summer snows, while the winters would still be dry, and ex- 

 tremely cold. Such a refrigeration would freeze up all the tem- 

 perate lands of the globe and would hardly be in harmony with 

 the rich marine and land life of the Permic deposits found in these 

 regions, nor with the evidence of warm climate furnished by arid 

 deposits of this period in other regions. A shitting of the pole, as 

 elsewhere suggested, to such an extent that it would lie somewhere 

 in the Indian Ocean would account satisfactorily not only for the 

 Dwyka conglomerate, but also for the Talchir glacial formation 

 of northwestern India, the movement of the glaciers forming 

 this being, like those which formed the Dwyka, away from the 

 equator, but in the opposite direction. It would also account for 

 the Muree glacial formation of southeastern Australia. 



Koken (17a) has discussed this question at length, with special 

 reference to India, and he gives a map of the world showing the 

 possible position of the poles at that time under the theory of 

 polar displacement. He places the North Pole near Tultenango, 

 Mexico (lat. 20° N.. long. 100° W., of to-day), and the South Pole 

 in the middle of the Indian Ocean (lat. 20° S., long. 80° E., of 

 to-day). 



Endolithic Brecciation. 



Endolithic brecciation. or the shattering of the strata by forces 

 at work within the rock mass itself, is best shown in formations 



