196 A. J. TIEJE 



ing pace with the disintegration of the granite under semiarid 

 climatic conditions. The rock fragments were so rapidly buried in 

 a constantly subsiding trough that they were little rounded or 

 comminuted. Violent currents in the shallow sea produced the 

 cross-bedding.^ 



Interpretation: the writer's river hypothesis. — Behind the marine 

 hypothesis is the weight of tradition. Yet the hypothesis seems to 

 have serious defects. Scarcely one characteristic of the beds sug- 

 gests to a modem sedimentationist marine conditions; taken 

 together, the characteristics almost irresistibly point to a conti- 

 nental origin. The lack of a marine rhythm; the thickness of the 

 conglomerate or arkose; the lateral variation; the unsorted, 

 unsized, angular material, the red color; the freshness of the feld- 

 spar; the type of cross-bedding — this combination emphatically 

 indicates deposition by a river in a semiarid climate. The presence 

 of Lingulodiscina at Colorado Springs can be harmonized with 

 such a point of view. 



Nor is such a point of view entirely a matter of theory. It Has 

 been checked by studies both of the Pliocene Nussbaum formation 

 of eastern Colorado, admittedly of river origin, and of the sediments 

 now being left in alluvial fans and on flood plains by Boulder, Clear, 

 Big Thompson, Fountain, and other "creeks" debouching from the 

 Front Range. The correspondence, except for color (a matter 

 easily explained), is well-nigh perfect. Photographs were taken of 

 Fountain sediments newly revealed in cuts at Golden and of modern 

 flood beds exposed at Boulder in diggings. Pennsylvanian and mod- 

 ern sediments can scarcely be distinguished from each other. 



By these studies, the origin of the cross-bedding in the Fountain, 

 e.g., becomes manifest. In flood time, if not restrained by man, the 

 present "creeks" would wander far from their channels, trespassing 

 on each other's territory and confusing coarse and fine sediments. 

 In fact, the Nussbaum "creeks" did so wander. The result, as 



' N. M. Fenneman, op. cit., pp. 54-57. Occasionally the suggestion is stiU met 

 that the entire present Rocky Mountain area was submerged, the Fountain thus being 

 an eastward extension of West Slope formations like the Maroon conglomerate. But 

 the Maroon conglomerate is finer than the Fountain material, and surely such large 

 bowlders as are common in the Fountain could not have been transported far. 



J 



