DISTURBANCES OF AZOIC BEDS. . 143 



ore region of Marquette, in Michigan, has been referred to the Huronian. 

 Should these Huronian rocks be found hereafter to contain any fossils, they 

 would form the first member of the Silurian. 



According to Hunt, no talcose or chloritic schists occur among the Lauren- 

 tian rocks. 



Original condition of the Azoic beds. — The alternations of argil- 

 laceous, chloritic, and other schists with quartzites, limestone, 

 gneiss, and the other Azoic rocks, prove that all were once sedi- 

 mentary beds, — beds formed by the action of moving water, like 

 the sandstones, argillaceous beds, and limestones of later times. 

 They have no resemblance to lavas or igneous ejections. The 

 schists graduate into true slates, and the quartzites into unmistak- 

 able sandstones and conglomerates; so that there is direct proof in 

 the gradations as well as the arrangement in alternating layers 

 that all the schistose and siliceous rocks are parts of one series 

 of sedimentary beds which by some process have been hardened 

 and crystallized. Moreover, from the gneiss there is as direct a 

 passage to the gneissoid granite, and thence to true granite and 

 syenite ; so that even the most highly crystalline rocks cannot, as 

 a general thing, if at all; be separated from this series. These 

 Azoic rocks, therefore, are made out of the ruins of older Azoic, — 

 that is, of the sands, clays, and stones gathered and deposited by 

 the ocean as it washed over the earliest-formed crust of the globe. 

 Whenever the ocean took its place upon the cooling globe, the 

 conflict began, and sedimentary beds were the result ; and the 

 original crust is now so disguised amid these later crystallized depo- 

 sits, which are here called Azoic, or is so buried beneath them, that 

 geology can hardly expect to identify any portion of it. The loose 

 material transported by the currents and waves was piled into 

 layers, as subsequently in the Silurian, Devonian, and Carboni- 

 ferous ages, and vast accumulations were formed ; for no one esti- 

 mates the thickness of the recognized Azoic beds as below fifteen 

 or twenty thousand feet. Limestone strata occurred among the 

 alternations ; and argillaceous iron-ores, like the beds of the Coal 

 measures, though vastly more extensive, were a part of the forma- 

 tions in the deposits. 



The beds, moreover, were spread out horizontally, or nearly so ; 

 for this is the usual condition with sediments and limestones when 

 first accumulated. The original condition, then, of the Azoic rocks 

 was the same as that of ordinary sediments, — in horizontal beds 

 and strata. 



Disturbances and Foldings. — But, from the sections and de- 

 scriptions on the preceding pages, it is apparent that horizontal 



