CLIMATES OP GEOLOGIC TIME. 283 



stocks. This well-known fact is clearly brought out by Walther in his interesting book, 

 "Geschichte der Erde und des Lebens" (1908), in Chapter 26, entitled "Cretaceous time 

 and its great mortaUty." Entire stocks of specialized forms vanished, just as did other 

 stocks at the close of the Paleozoic. In late Cretacic time it was the ammonites, belemnites, 

 the rudistids that began to develop in great numbers in the Lower Cretacic, and the other 

 thick-shelled large bivalves (Inoceramus) that perished. In addition, there was a great 

 reduction among the reef corals, the replacing of the dominant ganoids by the teleosts or 

 bony fishes, and, finally, the complete dying out of the various stocks of marine saurians. 



On the land, with the further rise of the Angiosperm floras, we see the vanishing of the 

 reptilian dragons known as pterodactyls, and, at the very close of the Cretacic, the last of 

 the large and small dinosaurs and the birds with teeth. "We thus see the reptiles displaced 

 from the seas by the fishes; on the land they are restricted by the rise of the mammals, in 

 the air after a short struggle by the more finely organized birds — in short, the reptilian 

 dominance is destroyed with the end of the Mesozoic era, in which entire time they were 

 the characteristic feature " (Koken, 1893: 436). 



The Upper Cretacic was therefore a time of great mortality among animals, "here 

 sooner, there later; although numerous relict faunas are preserved for a time and last into 

 the Cenozoic, still there never was so great a mortahty as that taking place toward the 

 close of the Cretacic" (Walther, 1908: 449). 



During the Upper Cretacic, but more especially toward the close of the period, mountain- 

 maldng on a vast scale went on, along with exceptional outpourings of lavas and ashes. 

 These movements, though of less intensity, were repeated in early Tertiary times, and 

 while they were equaled only by those of the closing period of the Paleozoic, they were 

 exceeded by the crustal deformation of late Tertiary time; they form the Laramide revo- 

 lution of Dana, embracing the mountains of western North and South America from 

 Cape Horn to Alaska and the reelevation of the Appalachian and Antillean Mountains. 

 Throughout the Eocene in the Rocky Mountains there were many volcanoes throwing 

 out immense quantities of ashes in which is entombed a remarkable vertebrate fauna. 

 Then in late Cretacic time in peninsular India occurred the Deccan lava flow^s, the most 

 stupendous eruptions known to geologists, covering an area of 200,000 square miles, in 

 thickness an;yT\'here up to a mile or more. 



Although there were these great crustal movements toward the close of the Upper 

 Cretacic, nevertheless they seem to have had no marked effect on the climates of the 

 world, for nowhere has anyone shown the presence of unmistakable glacial tills of this age.* 

 Then, too, the floras of early Tertiary times are said to be of about the same character as 

 those of the late Cretacic and they indicate that the climates were warm with slight 

 latitudinal variation, so slight that even in Greenland and Spitzbergen the early Tertiary 

 floras were those of a moist and mild climate. 



Tertiary. — We have seen that there was no marked climatic change in the time from 

 the Cretacic to the Eocene, but that there was a reduction in temperature is admitted by 

 paleobotanists and students of marine life. Berry states that the Middle Eocene floras of 

 Europe "show many tropical characters absent in the earlier Eocene" (1910: 205). The 

 Oligocene marine faunas were prolific in species, and the largest of all foraminifers, the num- 

 muhtes, although still present at this time, had their widest distribution and largest species 

 in the Middle Eocene and especially in the Tethyian Sea of the Old World, extending from 

 20° S. to 20° N. latitude (Stromer, 1909: 42). 



In IVIiocene time on Spitzbergen (Cape Staratschin) lived the swamp cypress {Taxodium 

 distichum miocenum), a leafy sequoia, pines and firs, besides various hardwood trees, such 



*At the Princeton meeting of the Geological Society of America, December 29, 1913, Professor W. W. Atwood 

 announced the discovery of a tillite about 90 feet thick in the San Juan Mountains of southwestern Colorado. 

 The age of these glacial deposits is somewhere between late Cretacic and late Eocene. We therefore are now on 

 the road to finding the physical evidence of a reduced climate during or following the close of the Laramide 

 revolution. 



