In an area of about 1 500 square miles, ten parent material classes were recognized on the basis of texture (grain-size) and petrography (base in rock fragments and carbonate content relate to nutrients available to plants). The distribution of materials in various landforms was related to mode, direction, and distance of transport from their bedrock sources by glaciation and by subsequent inundation by the post-glacial Champlain Sea.An ancient shoreline in the Ottawa Valley at 500 to 520 ft probably marks an important stage of the Champlain Sea.An improved basis for mapping soil series comes from such an understanding of the geologic events responsible for the distribution of parent materials.

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