UNCONFORMITY IN LARAMIE OF RATON COAL FIELD 717 



companying clay, it is one of the best keys of the series. While there are 

 many changes and local variations in the sandstones and shales, caused in 

 many cases by distinct erosion intervals, this coal, while not always workable, 

 is uniformly found over a large area. It is not marked by distinct foldings 

 or distortions, but by parallelism with both the under and overlying strata. 

 At the site of Dam No. 5, on the Ohio River, on the eastern edge of the Beaver 

 Quadrangle, between the towns of Rochester and Freedom, a recent railroad 

 cut exposes, in a distance of some 600 feet, a series of foldings involving the 

 strata between the base of the Lower Kittanning clay and the horizon of the 

 Middle (Upper) Kittanning coal (about 35 feet), in no way involving the 

 underlying strata or those above the horizon of the Middle Kittanning coal. 



FURTHER EVIDENCE OF AN UNCONFORMITY IN THE SO-CALLED LARAMIE 

 OF THE RATON COAL FIELD, NEW MEXICO 



BY WILLIS THOMAS LEE 



(Abstract) 



During the summer of 1910 a critical examination was made of the uncon- 

 formity in the coal-bearing rocks of the Raton coal field. New Mexico, which 

 was announced in a paper read before the Geological Society of America two 

 years ago, and the investigation was extended throughout the Raton Mesa 

 region. The line of unconformity was followed, and the structural relations 

 of the two coal-bearing formations were examined at points separated by 

 short distances. Additional evidence was obtained of a time break between 

 these formations. The lower one is variable in thickness, and in order to 

 show this variation columnar sections were measured along the outcrop in the 

 steep sides of the mesas. These indicate that the ancient surface represented 

 by the unconformity was an undulating plain, and an inspection of the bed- 

 ding, together with the character of the basal conglomerate of the upper 

 formation, proves that this plain was one of erosion. Data were collected 

 that indicate in a general way the amount of this erosion, and fossils were 

 collected that will establish the geologic age of the two coal-bearing forma- 

 tions. 



REPEATING PATTERNS IN THE RELIEF AND IN THE STRUCTURE OF THE 



LAND 



BY WILLIAM HERBERT HOBBS 



Published as pages 123-176 of this volume. 



Discussion 



Prof. W. M. Davis presented some objections to the sweeping jipplication of 

 the control of drainage courses by joint systems, and suggested that chance 

 agreements may have a larger value than is given to them by Professor Hobbs. 

 The structure is always recognized by physiographers as in one way or an- 

 other exerting control on processes of surface sculpture, and if physiographers 

 have given small value to joints as guides to stream courses, it is because 

 they believe that joints are in many cases not of much importance in that 

 connection, although in special localities their importance is undeniable. 



