INTERESTING LOCALITIES OF MESNAKD QUAUTZITE. 237 



These exposure^! here are less mashed than at Mount Mesnard, and at many 

 pkces beautifully show ripple marks, especially in the slaty phases. The 

 rocks are vertical or have a dip of 80° to the south. The only indication 

 of the direction in which they have been upturned is given by the ripple 

 marks. An examination of these shows the south faces of the quartzites to 

 have the normal form of the ripple marks and the north faces their casts.' 

 This furnishes e\'idence in support of the statement first made, that these 

 quartzites are on the south side of the fold and are a continuation of the 

 southern part of the quartzite of Mount Mesnard. 



Mount chocoiay.— On Mouut ChocoUy (Atlas Sheet XXXIX), about 3 miles 

 south of i\Iarquette, are the extreme eastern exposures of the Marquette 

 series. This prominent bluff rises about 150 feet above the sand plans of 

 the Chocoiay River, to the soutli and east. The eastern abrupt face of the 

 bluff gives beautiful exposures of the Mesnard quartzite, of the Kona 

 dolomite, and of the imderlying green schists of the Archean. The major 

 part of the bluff' is a simple syncline, the dips of the quartzite being 

 about 60° N. on the south side and 85° to 90° S. on the north side. The 

 quartzite exhibits nearly all phases of the formation, including the slaty 

 and novaculitic phases, cherty quartzite, and the ordinary massive forms. 

 The Kona dolomite c(institutes the center of the syncline and the toi) of the 

 bluff. As usual, between the quartzite and dolomite is a thin bed of slate. 

 A ravine separates the Mesnard quartzite from the green schist of the Base- 

 ment Complex to the south. The two, however, dip in opposite directions, 

 the quartzite about 60° to the north and the schistose structure of the green 

 schists about 45° to the south. 



On the western end of j\Iount Chocoiay the quartzite formation is found 

 to pass entirely around the dolomite. In passing from the north to the south 

 side the strike varies from west to southwest, then to south, and finally to 

 southeast, thus showing that the whole is an eastward-plunging syncline. 

 Superimposed upon this major fold are beautifully exposed minor anticlines 

 and svnclines. Near the base of the formation on the southwestern part of 

 the mountain is found a thin belt of conglomerate, very similar to that on 



'Principles of North American pre-Cambrian geology, by C. R. Van Hise. Sixteenth Ann. Kept. 

 U. S. Geol. Survey, Part I, 1896. pp. 720-721. 



