Does the pattern of the rock boundaries tell anything about the geologic history of the quad?
The distribution of rock types and rocks of different ages shown on a bedrock map together with the interpretation of the 3-dimensional structure of the bedrock are the key elements in deducing the geologic history of a region. As mentioned above, the bedrock preserves a record of the geologic events that created and modified the geologic units we see (and map) today. They may tell us about a long period of sediment deposition on the floor of ancient ocean, followed by a period of mountain building and erosion, or massive volcanic eruptions and the intrusion of masses of molten igeous rock. By “reading the rocks” to identify these events and their relative ages, the geologist can piece together the geologic history of a region. With the aid of techniques used to determine the absolute ages of geologic units, the geologist can construct the type of geologic history described in the Bedrock Geologic History of Maine.
