Core samples taken in northwestern Lake Huron, from present depths ranging from 110 to 436 feet, show a sequence of deep-water lake clays which is cut by an unconformity extending down to a present depth of 230 feet. The unconformity is marked by a thin layer of sand and shallow-water fossils, and these are overlain by clay. Allowing for an estimated 160 feet of uplift since the zones below the unconformity were truncated, the unconformity is interpreted as evidence of a low-level lake stage at 190 feet above present sea level. This is the extreme low stage of Lake Huron, inferred by Stanley (1936) and named the Stanley Stage by Hough (1955). A conformable zone of silt occurring within the lake clays and extending from 230 to 338 feet (present depths) is considered a shallow water deposit of the Stanley Stage. Deep-water clays, in depths below the Stanley level, have grain size variations which may correlate with changing depths of water resulting from the combination of changes in lake level and elevation of the bottom.

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