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.