444 WARREN AND POWERS DIAMOND HILL-CUMBERLAND DISTRICT 



Woodworth.^^ The latter bases his opinion as to their age on the relative 

 degree of metamorphism between this series and the Lower Cambrian 

 fossiliferous series of Hoppin Hill, jSTorth Attleboro. He says: 



"The Olenellus fauna occurs in little-altered, red calcareous sliales and slates 

 at North Attleboro in close proximity to granite. Four miles west of this 

 inlier of the Carboniferous area occur the sediments involved in the Black- 

 stone series complex. These strata are highly altered sediments, now horn- 

 blendic and chloritic schists, mainly of a green color, altered sandstones or 

 quartzites, and crystalline limestones. . . . The criterion appealed to in this 

 case is embodied in the statement that where two sets of rocks coexist in the 

 same dynamic field, that group which has undergone movement more than the 

 other is the older. If this view is maintained, this series of rocks falls into 

 the pre-Cambrian." 



As no fossils have been found in these rocks, the only criteria for the 

 determination of age are the lithological resemblance of the series to the 

 rocks in near-by fossiliferous horizons and the relative degree of meta- 

 morphism. These will be discussed in this order. 



Any determination of age on purely lithologic evidence is of doubtful 

 value. In the district under consideration four fossiliferous Cambrian 

 localities have been found. ^^ Three of these are near Hoppin Hill, al- 

 ready referred to, and the other is at a place about two miles north of 

 the town of Diamond Hill, within a few hundred feet of the Massachu- 

 setts-Rhode Island line. The Cambrian 



"consists chiefly of reddish aud greenish shales and slates with whitish and 

 reddish layers and nodules of limestone. Sandstone beds are known at almost 

 all exposures, but form only a vei-y unimportant element of the Olenellus 

 Cambrian, so far as this horizon has been definitely recognized." " 



Emerson and Perry say of the Blackstone series : 



"The highly ferruginous and highly calcareous green schists must have been 

 derived from rocks exactly like the red calcareous shales of the 'Attleboro 

 series,' and the quartzites from rocks closely like the sandstones of the Brain- 

 tree Cambrian" (page 34). 



On the other hand, there is apparently no reason why the rocks of the 

 "Attleboro series" could not have been derived from the Blackstone 

 series, or why both could not have been derived from similar rocks. They 

 then attempt to compare with the Blackstone series the Cambrian quartz- 



" C. T. Jackson : Op. cit. 



W. O. Crosby : Geology of Eastern Massachusetts, 1880, p. 128. 



Shaler: Bull. Mus. Comp. Zool. Harvard College, vol. 16, 1888, p. 15. 



Woodworth : Monograph U. S. Geol. Survey No. 33, p. 105. 

 " A. F. Foerste : Monograph U. S. G^ol. Survey No. 33, pp. 386-393. 

 " A. F. Foerste : Op. clt, p. 393. 



