Minnesota Mollisol
Minnesota Mollisol This soil has an A horizon 16 inches thick over a thin Bt horizon. The arrows mark the top and bottom of the Bt where clay has accumulated. Below the Bt is the C horizon. The lowest arrow points to a spot of carbonate. The glacial till from which this soil formed was rich in calcium carbonate. Over time, the carbonate has been removed from the upper part of the profile by water leaching through the soil. In a humid climate such as Minnesota, where carbonate is found in the subsoil, weathering has not progressed sufficiently for the horizon to be called a B horizon. This is designated the C horizon.

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