606 Scientific Proceedings^ Royal Dublin Society. 



and many other facts go to show that there is a slow upheaval going on at 

 present. So then, to sum up, we have evidence in the region we are dealing 

 with of a sequence of events as follows during late Tertiary and (Quaternary 

 times : — 



1. A period, probably late Pliocene, when the superficial pampa deposits 

 were formed. These deposits consist to a large extent of fine shingle, clays, 

 and sands, and the climate of the period must have been of a nature 

 unfavourable to life, as the writer has never known of any fossils, either 

 marine or terrestrial, having been found in the superficial pampas of the 

 district in question. 



2. A period of great glaciation, when an ice-sheet came from the south 

 or south-west, carrying large granite boulders, and depositing them on the 

 surface of the aforementioned pampa formation, even on the tops of the 

 highest hills. 



3. Recession of the ice-sheet and outburst of volcanic activity ; large lava 

 sheets were poured out ; periods of quiescence and subsequent outpourings 

 lasted a long time. 



4. Period of elevation with local minor glaciation ; extension of ice and 

 snow down from the Cordillera in the west into the plains ; considerable 

 erosion of basaltic and pampean formations. 



5. Period of subsidence for a short time ; the sea encroached on lower 

 pampas. 



6. A period of elevation, which is still going on. 



Now all these subsidences and elevations must have been very gradual, 

 and must have extended over prolonged periods, since in all the formations 

 observed by the writer in this district, even right up to the outpourings of 

 lava, the strata exhibit wonderfully even horizoutality, and show practically 

 no evidence of curving or distortion. This evenness is as well marked in the 

 Santa Cruz formation, which is supposed to be of Miocene age, as in the most 

 recent rocks. To conclude, I would suggest that the evidence which I have 

 brought forward tends to prove that the great or general Ice Period which 

 deposited the large erratic boulders on the top of the pampa must have 

 occurred at a very remote period, probably many hundreds of thousands of 

 yeai's ago. Dr. Nordenskiold and Prof. Steinmann believe that it was 

 contemporaneous with the greatest of the Ice Periods which occurred in 

 Pleistocene times in the northern hemisphere; however, if it was, it would 

 place tlie latter also at a more remote period than some recent writers would 

 allow, 



