Precambrian of Minnesota
Thick fluvial sequence of sandstones, mudstones, and paleosols preserved between massive basalt flows near the west coast of Lake Superior in
Minnesota. These units represent a massive floodplain environment that existed during times of quiescence in the rifting that lead to the emplacement of the
Keweenawen Province preserved in Minnesota, Wisconsin, and Michigan. While most of the exposures in Michigan and Wisconsin have experienced pervasive
copper mineralization, the Minnesota sections are free from both ore deposition and metamorphism, making them an ideal place to study the paleosols for use
in paleoatmospheric reconstruction.|
This exposure, on the shore of Lake Superior, preserves clastic dikes that formed when sediments derived from the underlying basalt were deposited
in large cracks at the top of the 'a'a flows.
Near the base of the sequence in the first picture above, there are siltstones that preserve ripples. Perhaps these sediments were also sticky due
to the presence of microbiota.