H. E. Gregory — Shinarump Conglomerate. 427 



feet.* Dutton gives it a thickness of rarely over fifty feet, a 

 conglomerate consisting of " fragments of silicified wood imbed- 

 ded in a matrix of sand and gravel " and occurring in the midst 

 of 550 to 750 feet of " transition shales." f The section at 

 Toquerville, Utah, measured by Huntington,;): shows fifty to 

 sixty feet of hard conglomerate and sandstone. Newberry 

 measured near Winslow, Arizona, a section containing twenty 

 feet " of coarse, light brown sandstone, with white, bluish, red 

 and black quartz pebbles varying in size from that of a pea to 

 an egg^ .-.'." quite indistinguishable from the Carbon- 

 iferous conglomerate of Ohio and Pennsylvania." § Gilbert | 

 mentions thirty feet of gray conglomerate with silicified wood. 



The writers quoted above speak of the Shinarump conglom- 

 erate as a single stratum, and at nearly all localities I have vis- 

 ited it appears as a distinct bed or set of beds maintaining its 

 individuality throughout. It is terminated below by an uncon- 

 formity, and continued above by shales containing beds of 

 limestone conglomerates. While its thickness is usually less 

 than one hundred feet, and occasionally less than twenty feet, 

 yet at Moses Rock it (Oljato sandstone member = Shinarump 

 conglomerate) forms a single massive bed 382 feet thick. T 



In contrast to the views expressed above, Ward** treats the 

 Shinarump conglomerate as a group consisting of beds of 

 diverse lithologic character. While recognizing clearly that 

 the conglomerate so abundantly exposed in the Adamana fossil 

 forest, near Winslow, at Red Butte, and on the Moencopie, is 

 the true equivalent of the Shinarump conglomerate of Powell, 

 Gilbert, and Dutton, and also that the conglomerate marks the 

 upper limit of chocolate-brown, argillaceous shales charged 

 with salt and gypsum, yet he considers this bed not as a single 

 stratum but as a series consisting of " conglomerate and cross- 

 bedded sandstone, often with pink and white striped, clay 

 lenses-, interstratified with gray argillaceous shales and varie- 

 gated marls, the latter locally much thickened, forming bril- 

 liantly banded cliffs. ft For this series, 800 feet in thickness, 

 Ward adopts the term " Shinarump conglomerate,"^ changing 

 it later §§ to u the Lithodendron member of his Shinarump for- 



* Geol. Surv. West of 100th Meridian, III, 283. 



■f Geology of the High Plateaus of Utah, p. 147. 



X Bull. Geol. Soc. Amer., vol. xviii, p. 385, 1907. 



§ Ives' Report upon the Colorado River of the West, 1857-58, Pt. Ill, p. 375. 



I Geology of the Henry Mountains, p. 6. 



^[Woodruff, E. G.: Geology of the San Juan Oil Field, U. S. Geol. Survey 

 Bull., No. 471, Pt. II, 1910, p. 183. 



** Ward, L. F. : U. S. Geol. Surv., Monograph XL VIII. p. 19 ff. Ibid., 

 p. 45. 



ft Ibid., p. 45. 



XX This Journal, xii, pp. 201-13, 1901. 



§§U. S Geol. Surv., Monograph XLVIIT, pp. 13-46. 



