THE MINNESOTA COAST. 263 
porphyry. In the gap between this gabbro and the slate on the Saint Louis, 
the base of the Keweenaw Series lies concealed. 
The Saint Louis River slates at Thompson, eight miles west of Fond du 
Lac, trend N. 85° E., and have a dip of some 30° to 40° southward. Far- 
ther down stream, towards the junction with the overlying sandstone, they 
trend somewhat more to the northeast. The gabbro does not exhibit any 
sign of bedding. However, the trend of the hills which it forms in the 
southeast part of T. 49, R. 15 W., is about N. 46° E., and near Duluth still 
more to the north. Eighteen miles north of Duluth, on the Cloquet River, 
in the southern part of T. 53, R. 14 W., the same gabbro reappears. It 
seems to form a belt running at first northeast and then more and more to 
the north until it finally takes a nearly northerly course. So far as these 
facts go there is no definite evidence of unconformity between the gabbro 
and the Saint Louis slates. The appearance is rather the other way. 
In the eastern part of the city of Duluth we begin to find plainly bed- 
ded rocks flanking the coarse gabbro on the east, and for the entire dis- 
tance to Grand Portage Bay these bedded rocks prevail, as also back in 
the country for many miles. They are diabases of several kinds; amyg- 
daloids; typical luster-mottled melaphyrs, or fine-grained olivine-diabases; 
coarse-grained gabbros, belonging chiefly to the orthoclase-free kinds, but 
including also orthoclase-gabbros; anorthite-rock; felsites; quartz-porphy- 
ries; granitic porphyries; porphyry-conglomerates; and red sandstones 
and shales. In other words, we find here precisely the same rocks that 
characterize the Keweenaw Series on the South Shore. Detrital beds are 
here relatively rare, and the layers thin, as compared with those of the Ke- 
weenaw Point series, but we have here to do with quite low horizons which 
are in general comparatively free from detrital layers. 
At Duluth, as already said, the trend of the layers in sight on the coast 
is at first even slightly west of north, with an easterly dip of 45°. These 
are rapidly changed for a due northerly trend, and 25° easterly dip, and 
these again, by the time the mouth of the Lester River, which is 54 miles 
below Duluth, is reached, for a N. 30° E. trend, and a 15° S.E. dip. Be- 
tween Lester and French rivers, the strike directions make more and more 
easting, becoming finally, on French River, 124 miles below Duluth, N.50° E., 
