They consist of ophitic gabbro and layered troctolite with cross-cutting pyroxenite. The contact with the North Shore Volcanic Group is exposed at the far west side of the stop. Stop 4 . Lief Erickson Park, Duluth . Basalts, dikes, and interflow sedimentary rocks of the North Shore Volcanic Group.
Basalts vary from porphyritic to massive, non-porphyritic.
Flow bottoms are massive and may contain pipe vesicles. In several places flows are separated by interflow sedimentary sandstone which varies from less than two inches thick to one unit that is 116 feet thick. Dikes tend to be massive and very fine-grained and weather out in positive relief. Stop 5 . 42nd Avenue East, Lakeshore Lutheran Home.