THE CAMBRIAN PERIOD. 



265 



Section in Massachusetts. 1 



Names of Formations. 



Thickness 

 in Feet. 



Characteristics. 



73 .o 



s g 1 Braintree section , 



Discontinuity. 



North Attleboro 

 (belongs below 

 Braintree section) . 



1000- 

 500 to 1000 



2000 ± 



Unconformity 

 Archean. 



Conglomerate of quartzite pebbles and sand- 

 stone. 



Greenish-gray, fine-grained, siliceous slates; 

 Middle Cambrain fossils. 



Thin-bedded shales "which occasionally pass 

 into fine-grained greenish and reddish slates; 

 a few beds of conglomerate varying from 

 200 to 300 feet in thickness; some beds con- 

 tain Lower Cambrian fossils; little meta- 

 morphosed. 



Strata dip at high angles. 



Section in Northern New Jersey. 2 



Names of Formations. 



Thickness 

 in Feet. 



Characteristics. 



Trenton formation. 

 Unconformity. 



~ f Upper part = 



2 c - I Lower Ordovician 



2700 to 3000 



c3 c 

 0,^ 



Kittat in ny limestone. 



(Lower part = 

 Lower Cambrian.) 



|.S \ Hardiston quartzite. 

 J I 



to 185 



Blue or gray, sometimes nearly black lime- 

 stone, variable in texture, composition- 

 and color: arenaceous at base. 



Sandstone, quartzite, locally arkose; inter- 

 calated beds of shale and dolomitic 

 limestone; Lower Cambrian fossils. 



Unconformity. 

 Pre-Cambrian. 



Strata gently folded. 



The published sections of the Cambrian of Texas are not altogether in accord. 3 

 The Middle and Upper Cambrian series are represented by sandstone and lime- 



l Ibid., pp. 268-73; and 10th Ann. Rept. U. S. Geol. Surv., p. 567. 



2 Kiimmel and AYeller, Bull. Geol. Soc. Am., Vol. XII, pp. 147-154. 



3 Walcott, Bull. Geol. Soc. Am., Vol. X, p. 218; 10th Ann. Rept. U. S. Geol. Surv., 

 p. 552; Bull. 81, U. S. Geol. Surv.; and Am. Jour. Sci., Vol. 28 (1884), pp. 431-33; 

 and Comstock, First Ann. Rept., Geol. Surv. of Texas, 1889, pp. 285-292. 



