Figure 4. Portion of surficial geology map of the Gray 7.5-minute quadrangle. Topography is an important characteristic of surficial landforms. A marine delta (unit Pmdsp) is identified by its extremely flat surface in this example. In coastal Maine, elevation is another important variable. Marine clay (unit Pp) was deposited up to specific elevations across coastal portions of the state. This fact allows the mapper to interpret the contact based on elevation as shown in the lower portion of the figure. The till unit (Pt - upper right) is mapped above the elevation of the delta and marine clay.

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Last updated on October 6, 2005

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