THE MOXA SCHISTS. 153 



composed of f^TOups of these knoljs, i-aised high above the valleys between 

 them. Their sides are ragged and rough, or smooth and vertical, and their 

 tops are rounded knolls 



The streams flowing over tlie schists have not yet succeeded in trenching 

 their channels to any considerable depth. Tlieir courses are marked by 

 rapids and cascades, over which the waters tumble in a series of low falls. 

 The rocks in the beds of the streams and along their sides are usually rough 

 surfaced, in consequence of tlieir highly developed schistosity. As a resixlt, 

 we find the di-ainage channels through the greenstone-schists presenting an 

 entirely different aspect from those through the granite areas or through 

 the areas underlain by the Algonkian rocks. The view shown in PL IV, 

 fig. 2", is tvpical for the larger streams through this district, 



EKLATIONS TO AD.JACBNT FORMATIONS. 



It has already been stated that the green schists pass graduallv into 

 the gneissoid granites to the north through the intrusion of the former by 

 apophyses of the latter. In referring to this contact Williams writes:^ 



There is no such sharp line of contact us is represented on Roininger's map, but, 

 on the contrary, as Roniinger himself explains, there is a complete interpenetration 

 of the two rock masses. The granite has intruded itself into the schistose greenstones, 

 for the most part follo\ying their bedding and forcing apart their strata. The amount 

 of the acid rock gradually diminishes as we go soutliward. 



At a greater or less distance from the contact the granite is completely 

 absent, and the green schists occur alone, except for the dikes of aplite and 

 diabase that everywhere cut through them, as well as through all other 

 members of the Basement Complex, and the narrow l)ands of acid schists 

 with which they are interlaminated. 



The stratigraphic separation of the Mona schists from the Kitchi 

 formation to the west has not yet been possible. In passing from the former 

 area into the latter, beds of the conglomeratic schists are found more and 

 more frequently between those of the nonconglomeratic kinds. As Ave 

 shall see later, many of the Mona schists are probably altered tuffs, while 



' The greenstone-schist areas of the Menominee and Marquette regions of Michigan, by G. H. 

 Williams : Bull. U. S. Geol. Survey No. 62, 1890, p. 146. 



