GEOLOGY OF THE CONNECTICUT VALLEY DISTRICT. 459 



IX. Hornblendic rock, diorite, and dia- Clay slate, quartzite, mica schist, 

 base. 



VIII. Ferruginous quartzose flags ; clay Hornblende schist, 



slate and quartzite. 



VII. Hornblendic rocks. Hydrous magnesian schist and probably 



ferruginous clay slate. 

 VI. Ferruginous quartzose schist, clay VI. Hematite schist and siliceous flag 

 and chloritic slates. ore ; ferruginous clay slates ; hydrous mag- 



nesian schist; rarely granite dykes. 

 V. Quartzite verging into protogene ; V. Dolomitic marble ; rare beds of 



beds of dolomitic marble ; novaculite ; quartzite and hydrous magnesian schist. 

 rare chlorite and mica schist ; sienite, di- IV. Arenaceous magnetic mica schist. 

 orite, diabase, hornblende schist, con- III. Soft schist, not made out. 



glomeratic quartzite and quartzose iron II. Ouartzites, arenaceous, micaceous, 



ores ; talc schist. and actinolitic. Ripple-marked. 



I. Protogene gneiss ; hydrous magnesian 

 schist ; schistose conglomerate ; quartzite 

 and diorite. 



Major Brooks devotes much attention to Nos. XIX and XX of the Huronian as they 

 occur in Wisconsin, just over the Michigan line.* Though the rocks resemble the 

 Laurentian, he is satisfied they occur above all the other eighteen Huronian members, 

 while lying unconformably beneath the copper-bearing series, which he calls Keiveiiaw- 

 ian. Readers of our New Hampshire geology will recognize the resemblance between 

 these youngest Huronian rocks and our Coos or possibly the Montalban series. The 

 position at the summit of the Huronian is in exact agreement with the place of our Cods 

 group. This resemblance is sufficient to attract the attention of observers, and to give 

 new interest to the determination of the New England groups. 



Brooks estimates the thickness of the Menominee groups (exclusive of XX) at 12,000 

 feet, and only half that amount in the Marquette region. Steatite and serpentine are 

 rare in these Michigan rocks. 



The Huronian in New Brunswick. 



Under the name of Coldbrook, Messrs. Matthew and Bailey describe rocks of this 

 age near St. John, in New Brunswick. They are the following : 



Upper Coldbrook. 



b. Red and greenish-gray argillites, 170 feet. 



a. Red sandstones and conglomerate. 



6. Gray feldspathic sandstone, beds chloritic schists, conglomerate. 



* Amer. your. Sci., iii, vol. xi, p. 206; also vol. xii, p. 194. 



