436 F. B. WEEKS STRATIGRAPHY OF THE UNITA RANGE 



were favorably exposed. In stratigraphic position and litliologic char- 

 acter the beds are very similar to the Tonto shales. Their position 

 above the "Uinta" quartzite corresponds to that of the shales above the 

 quartzite series in Big Cottonwood canyon in the Wasatch mountains. 

 The latter, however, are only 150 feet thick, contain the Olenellus fauna, 

 and are overlaid by Cambro-Ordovician strata. According to the avail- 

 able evidence, it is believed that the Lodore shales represent the deposits 

 of Cambrian time in the Uinta region. This formation was not differ- 

 entiated by the 40th Parallel geologists. 



Description. — The Lodore shales constitute a series of argillaceous and 

 sandy green, red, and purple shales overlying the greenish sandstones 

 which form the upper part of the "Uinta" quartzite. In some parts of 

 the series lamination is not well developed and they resemble mud beds. 

 Many nodules and a marked tendency to nodular structures characterize 

 the green shales wherever exposed. The formation is well exposed on 

 Kamas creek, Provo river, and upper Duchesne canyon. In this region 

 the formation in its upper part varies considerably from fine to coarse 

 sandy or conglomerate beds (plate 45), and the transition to the suc- 

 ceeding formation is through beds of finer grain, altered into quartzite. 

 The thickness varies from a maximum of 1,200 feet on Duchesne river to 

 500 feet on Green river. In passing eastward the beds become thinner 

 by the disappearance of the sandy beds at the top. Along the northern 

 slope of the range the formation is mainlyshale from 400 to 500 feet thick 

 and well exposed on Green river and its tributaries. On Carter creek, 

 a few miles east of the point where it empties into Green river, there is a 

 fault of considerable displacement which brings the "Uinta" quartzite 

 against the Weber formation. To the west the formation is nearly every- 

 where covered by glacial debris as far as Weber river, where it is well 

 exposed in Smith and Moorehouse and South Pork creeks. Throughout 

 the Uinta region the Mississippian series overlaps the Lodore shales and 

 Ogden quartzite, but appears to overlie them in conformable position. 



ORDOVICIAN OaDEN QUARTZITE 



Nomenclature and correlation. — This formation was named and defined 

 by the geologists of the 40th Parallel Survey, and considered by them 

 to be Devonian in age. In its typical locality, Ogden canyon, and in sec- 

 tions east of Cache valley, Utah, the writer in 1906 found fossils above 

 and below this formation and also in interbedded limestones in the lower 

 part of this formation, determined by Mr E. 0. Ulrich, which show that 

 this quartzite is of Upper Ordovician age. In the Wasatch mountains 

 the quartzite varies from 800 to 1,200 feet in thickness and rests upon 



