TERTIARY AGE. 523 



litic beds of the Middle Eocene were forming over so large a part of 

 Europe, Africa, and Asia, even over regions which are now occupied 

 by the lofty mountains of these continents. At this epoch, Europe 

 was again an archipelago, as in the Cretaceous period. The Paris 

 basin was one of its great estuaries, varying between fresh and marine 

 waters, with changes of level and changing barriers. 



After the Eocene, in Europe (as well as in America), the marine 

 deposits had much smaller extent ; and the continent was mostly dr5 

 land. But the ocean-border, instead of having the American sim- 

 plicity, had numerous deep indentations and winding estuaries. 



But the geographical conditions here described were brought about, 

 in connection with mountain-making on a vast scale, at different epochs 

 in the course of the Tertiary. 



3. Disturbances during the progress of the Tertiary Age. — In 

 the Tertiary age, nearly all the great mountain chains of the world 

 either were made or received additions of many thousands of feet 

 to their heights, and hundreds of thousands of square miles to their 

 areas ; and, besides, far the larger part of igneous eruptions then took 

 place. 



(1.) The first epoch of disturbance in North America was one clos- 

 ing the Lignitic era. As has been stated, the Lignitic group in the 

 Rocky Mountain region is upturned at all angles, to vertically, be- 

 neath the fresh-water Tertiary of the Middle and Later Eocene. Its 

 deposition followed on after that of the 10,000 feet of Cretaceous 

 strata without interruption, and added several thousands of feet to the 

 conformable beds, the whole indicating the progress of a geosynclinal 

 of remarkable de'pth. So, again, in California, some hundreds of feet 

 were added, above the Cretaceous series. Apparently simultaneously, 

 in these two regions, 500 miles apart, one west of the Sierra Nevada, 

 and the other east of the Wahsatch, an upturning began which made 

 mountains now 3,000 to 4,000 feet high in California, consisting mainly 

 of Cretaceous rocks, and also elevations of considerable extent in the 

 Rocky Mountain region. 



(2.) The second epoch of disturbance was that closing the Alabama 

 period, or the Eocene era. At this time, the borders of the Mexican 

 Gulf, which had been under the sea, emerged, so that the later Ter- 

 tiary beds — the Miocene — are confined to the Atlantic Border. The 

 Rocky Mountain region, in Wyoming, Utah, and Colorado, may have 

 also been lifted to some small extent. # 



(3.) The third epoch of disturbance closed the Miocene era. At 

 this time, the Tertiary of California, which had accumulated to a thick- 

 ness of 4,000 or 5,000 feet, over the tilted Lignitic beds and Creta- 

 ceous strata, and in a more westerly trough or geosynclinal than the 



