J, P. Kimbail on Iron Ores of Marquette, Michigan. 291 
ite rocks, as laid down by the federal geologists, is presented in 
_ their map of the district between Keweenaw Bay and Chocolate 
_ fiver, to which reference can readily be had without encum- 
_ bering these pages with a verbal recital. 
The metamorphic or Azoic rocks, consisting of gneiss, horn- 
Ulendic, talcose and chloritic slates, and beds of argillite, no- 
vaculite, quartzite, conglomerate, saccharoidal marble and ecrys- 
talline limestone, were described as existing under conditions of 
great displacement, and displaying evidences of metamorphism, 
particularly in vicinity to the line of contact with the granite 
origneous outburst. ‘The occurrence of granite within the area 
of their distribution was recognized in the form of intrusive 
masses, while the greenstones and some of the schists, both fol- 
owing the general stratification, were regarded as trappean 
overflows, the former as an igneous product, the latter as pul- 
hot meant to be extended to beds of specular and magnetic 
as of iron included within metamorphic strata, with a con- 
ge and dip, which indeed the federal geologists ex- 
tly state their disposition to regard as the result of aqueous 
Position, 
vy: chigan, to. be developed in two distinct ranges or spurs, 0 
h the northern, including the Huron Mountains, forms the 
between Presqu’isle and Granite Point, and expands west- 
‘le ‘ 
en 
belt, the present iron industry of the region, from the southern 
«9 Which is of very irregular outline, though nearly parallel 
Pe distance of 36 miles along its northern intersection with 
oe tamorphic belt. The large expanse of crystalline rocks 
ing the undeveloped tract of the northern part of Wis- 
Stretching across the head waters of the Mississippi to 
* Foster & Whitney, ibid, 68. 
