344 DESOEIPTIVE GEOLOGY. 



having a strike of north 20° west, and dipping 65° to the west. On the 

 east of the axis, these beds dip still more steeply, and soon disappear under 

 gently-sloping sandstones of red and gray colors, which lie imconformably 

 on the eastern flanks of the range, and are said to belong to the Tertiary 

 formation. The rocks exposed on the western sptir of the peak and in the 

 canon below are mostly blue and gray limestones, with some interstratified 

 siliceous slates and argillites. Fossils of well-recognized Carboniferous 

 types are abundant, the lowest found being Spirifer opimus. The dip of 

 the western fold, although becoming somewhat less steep toward the west- 

 ern foot-hills, was nowhere observed to be less than 45°, so that a thickness 

 of nearly 10,000 feet of strata is shown here in section, unless faulting 

 shall have caused a reduplication of the beds. The observations of this 

 region were made at an early period in the work, when the subdivisions now 

 adopted had not been clearly recognized, and were necessarily of somewhat 

 hasty character, as they did not come within the province of the survey, so 

 that, while it can confidently be asserted that those strata which form the 

 main mass of the peak belong to the group called the Wahsatch limestone, 

 and in age to the Lower Coal-Measures, it is uncertain whether the higher 

 members of the Coal-Measures can be found here or not.* 



From Mount Nebo to Utah Lake, the range bends gradually to the 

 eastward, assuming opposite the southern end of the lake a position some 

 twelve miles farther east than this peak, and, with a trend a little west of 

 north, extends in a high narrow ridge to the granite body forming the mass 

 of Lone Peak. Though once a continuous ridge, this portion is now cut 

 through to its very base by the deep narrow canon-gorges of Spanish Fork, 

 Hobble's Creek, Provo River, and American Fork, which divide it into the 

 separate groups of Spanish Peak, Provo Peaks, and Timpauogos Peak. 

 The former of these does not come within the limits of the map, and will 

 therefore not be described, though of the same general structure with the 

 others. In this ridge is shown, in a most striking manner, the abruptness 

 with which the range rises above the almost level valleys which border it 



J Dr. C. A. White, in his report (Expl. W. of 100th Meridian, Lieut. G. M. Wheeler, 

 vol. iv, part i), describes a Produchis Frattcnianus from the top and a Hemipronites 

 crinistria from the east side of Mount Nebo. 



