A GEOLOGICAL RECONNAISSANCE OF BERNA- 



LILLO, VALENCIA AND McKINLEY COUNTIES 



DIVISION OF GEOLOGY, J. A. PYNCH, CHIEF 



INTRODUCTORY 



New Mexico is not built after the plan of the states of the 

 Mississippi valley, for nature has used here a unique type of 

 architecture. The straight skylines and the acute angles 

 of every back-ground are architectural effects common and 

 peculiarly New Mexican. 



In the Geological ages of the past there was one Era during 

 which this part ot our continent saw its greatest growth. It 

 is known a as the Mesozoic Era. Following this came the 

 Cenozoic, in which nature, with broad swoops and splashes, 

 put the finishing touches, on a broad scale, to the present 

 landscape. The first part of this latter era is known as the 

 Tertiary period. During this time Mt. Taylor, the Colorado 

 Canyons, the vast lava flows, the ennumerable slips and 

 faults had their day, and so grand was their effect upon the 

 surface features of this locality that the landscape is still 

 predominated by volcanic cones, lava flows, and fault scarps. 



New Mexico is a part of a great uplifted earth block. As 

 the Grand Canyon of the Colorado is due to this uplift by the 

 subsequent incisement of the Colorado River, so are the 

 lesser canyons and the many valleys which flute the length 

 of the state due likewise to the upward movement which 

 proceeded, accompanied, and also succeeded the volcanic 

 activity, which, as Geologically reckoned, has so recently 

 ended here. 



It has been stated that the major valleys run lengthwise of 

 the state, governed probably by two main causes in one 

 case by a roughly parallel, north and south system of fault- 

 ing, and, in the other case by a natural slope southward due 

 to the fact that the highest part of the uplift occured in the 

 northern part and diminished toward the south. The Rio 

 Grande holds the title, Rio Grande del Norte (Great River of 

 t he North) thus conveying by its name not only the idea of 



