GEOLOGICAL SURVEY OF THE ' TERKITOEIES. 441 



section have been worked oat with the degree of precision attainable 

 by instrumental observation, the main object in constructing it being 

 merely to illustrate a{)proximately the position and vertical range of 

 fossils with relation to tlie coal-beds, and to give a general idea of the 

 lithological characters of the series. It should be stated, however, that 

 the dip and estimated distance across the strike of the strata would 

 indicate even a greater thickness than the sum of the individual beds 

 observed. 



The dip of the be<ls, including the main coal (5) toward the lower 

 part of the section, seemed not to differ much from about 8° to 10° below 

 the horizon, to the northwestward ; but it increases gradually in that 

 direction, so that at the fourth ridge it is about 25°. .Between this 

 ridge and the mouth of tlie caiion we observed no marked change of 

 dip, though there ai)peared to be a slight unconformability between the 

 conglomerate and the lighter colored beds below at this place; and this 

 unconformity is more obvious at other points near here; while farther 

 np, near the head of the caiion, it is very strongly marked, the discord-, 

 ance being, according to Mr. Emmons, as much as 25°. 



Unfortunately, we have no means of ascertaining the precise distance 

 by an air-line traversed by the section, the linear survey of the Coal- 

 ville township not yet being completed. If we estimate the distance at 

 three miles, and the mean dip at 17°, however, it would give a thick- 

 ness not materially greater than the aggregate of beds noted in the 

 section. If tbe distance shonld be as much as three and a half to four 

 iniles, however, the difference would be so great as to warrant the con- 

 clusion that we have overestimated the dip, or, what is much more 

 probable, underestimated the breadth of some of the valleys between 

 the ridges, and consequently the thickness of strata hidden beneath the 

 same. As evidences of horizontal displacements of some of the ridges, 

 however, were observed, it is possible that the discrepancy may be, in 

 part at least, accounted for in that way.* 



Mr. Emmons gives in Mr. King's report about 0,000 feet as the entire 

 thickness of the Cretaceous series here, exclusive of the Echo Caiiou 

 conglomerate, which is apparently Tertiary. But I infer that he includes 

 in this estimate a considerable thickness of lower strata farther up , 

 Weber liiver than our examinations extended. 



All of the lower beds forming divisions 1 to 6, inclusive, of this section 

 are seen in a low hill, or rising space, directly on the southeastern mar- 

 gin of Coalville, flexed around so as not to conform to the general dip 

 and strike of the strata between this vicinity and Echo Canon ; their 

 strike being nearly north and south, and their dip nearly westward, 

 some 14° below the horizon. About two miles to the northeastward, 

 however, and at a higher elevation, coal-mines have been opened on the 

 main bed forming ]!so. o of the section, that show this bed and the over- 

 lying sandstone and other strata, conforming there with the general dip 

 and strike of the beds between theie and Echo Caiion. Between these 

 mines and Coalville, the highly fossiliferous strata forming the division 

 No. 3, which we know properly holds a position below the main coal- 

 bed, occur some hundreds of feet north of a right line between these 

 mines and the coal-mine directly at Coalville, in the same bed; thus 



*• Along Grass Creek we observed some curious iudications of lateral dis])laceiuents. 

 This crei-k cuts very obliquely through some of the ridges, wliich do not i'orrespoud on 

 opposite sides. That is, the ends of the ridges on opposite sides of the creek do not 

 coincide exactly, those on one side ending opposite intervening valleys between those 

 on the other, as if there had been a fracture along the course of the creek, and a lateral 

 displacement of tbe strata on one or both sides of the same. 



