PUBLICATIONS. as 
In chronological order the Keweenawan of the north shore of Lake 
Superior can be divided into gabbro, diabase, red rocks and later 
dikes. 
Grant,* in 1894, describes the lowest beds of Grand Portage Island, 
north coast of Lake Superior, as consisting of arenaceous slates, sand- 
stones and conglomerates, the fragments of the latter being quartz, 
quartzite, siliceous slate, a dark flinty rock, red quartz-porphyry and red 
granite. These arein part clearly waterworn. All of the pebbles of the 
conglomerate can be matched in the Animikie strata near by. These 
beds are regarded as the lowest of the Keweenawan in this locality, and 
the material in the conglomerate shows that the Animikie clastics had 
been subjected to metamorphosing forces before Keweenawan time, and, 
as agreed by all Lake Superior geologists, that there was an erosion 
interval between the two. As the red quartz porphyry and the granite 
_ have been shown to be intrusive in the Animikie, and also in the gab- 
bro and diabase of Pigeon Point and Grand Portage, it is concluded 
that these intrusions occurred at a date later than the Keweenawan. 
COMMENTS. 
It is to be presumed that this last statement applies only to the 
Keweenawan of the locality discussed. 
Lawson,” in 1893, describes a multiple diabase dike near the mouth 
of White Gravel River on the northeast coast of Lake Superior, where 
occur in a breadth of fourteen feet no less than twenty-eight vertically 
intrusive sheets of diabase, ranging in thickness from one inch to six and 
one-half inches, separated by twenty-seven sheets of granite, ranging 
in thickness from a quarter of an inch to eight inches. The dikes 
anastomose and are connected at various places, showing that they are 
due toasingleintrusion. The granite isseemingly homogeneous, there 
being no differentiation of structure or of mineral composition. It is 
believed that the splitting of the granite was due directly to the 
invasion of the diabase magma. This occurrence is comparable to the 
complex parallel invasion of the schistose rocks of the Ontarian 
system by granite. 
* Note on the Keweenawan Rocks of Grand Portage Island, North Coast of Lake 
Superior, by U.S. Grant. Am. Geol., Vol. XIII., No. 6, pp. 437-438, 1894. 
? Multiple Diabase Dike, by A. C. Lawson. Am. Geol., Vol. XIII., No. 5, pp- 
293-296, May, 1894. 
