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hurled out 12(» feet of iminic-e.ons tuff. These inoiintains were still Islands 

 in Cretuceous times, Imt their area then was mneh fireater. than foruievly. 

 In this period the mountains seem to liave been .liradually risinsi' until in 

 the Fort Fnion eiioeh ureat swamps covered the entire country, the sea 

 beiuK oi)iiterated lor a tinu\ In thesi> swamps vegetation was-hixuriaut. 

 and the ve^etaltle matter laid down in them forms today the coal fields 

 of nortli western New ^lexico. At the close of the Fort Union epocli^ there 

 w;is a slow sulisich nee. The I'uerco was deposited on the Fort Union, 

 and then the Focene on that, the whole series being conformal>le. Then 



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there came a violent change. The whole country was elevated al)Ove the 

 sea, much faulted and broken up, and blocked basins on a grand scale 

 resulted. Tiiese depressions were the lakes of Pliocene times. One large 

 lake existed in the vicinity of .Temez. and another in the liio Grand Valley. 

 The lake at .Temez was lilled up with the Temez marls by the tril)utaries 

 of the .Temez Itiver: and tlie Rio (irande Lakt' was silted up with the 

 Albuquerque marls, pro'iably liy the trii)utaries of the river which at 

 present occupies that valley. When tliese lakes were almost filled, tlun-e 

 was a further re-elevation of the country, and the rivers at once com- 

 menced to cut down their respective channels: but tliis deepening of their 



