rocks along the Keweenawan region. Medium
to fine grain rock. Appearance is generally brown, red or
tan. Freda Sandstone is also found
along the southwest border of Lake Superior in the Upper Peninsula of
Michigan, near the Presque Isle River.
similar to sandstone shale. Numerous rounded pebbles joined together by
finer materials. Pebbles generally are durable igneous rocks similar to
rhyolite and granite.
Copper Harbor Sandstone:
rock, with ripples and mud cracks. These are markings from water that
flowed in the Porcupines nearly one billion years ago.
and gray volcanic rock. Oldest rock found in the Porcupine Mountains,
near Summit Peak.
of gray and black shale with siltstone and sandstone. Found along the
Presque Isle River.
found to cap the Escarpment Ridge along the Porcupine Mountains.
along the Upper Carp River near Trap Falls. Andesite and Rhyolite are
often grouped together called felsite.
(all above images
courtesy of Michigan Department of Natural Resources)