Palermo
There are two different rock types found at this location. These two different rock types help to define the clear fault that is present. On the western side of the fault zone a low-grade metamorphic rock, phyllite is present. This rock has clay minerals that have recrystallized into microscopic micas thus giving the rock a non-banded, shiny, silky appearance. On the eastern side of this fault zone, a high-grade metamorphic rock, gneiss is located. This rock is elongated and more granular. The most common mineral found in gneiss is quartz and feldspar. This rock has a banded appearance due to the segregation of light and dark silicate minerals that have developed in gneiss. The phyllite has experienced drag folding along the contact zone of the fault.
The Norumbega Fault Zone: There is no one version surrounding what happened at this particular geological site, what you are about to read is a well-known theory.
This is a rather large fault zone that has regional faults running off it those cross-different sections through out southern and southeastern Maine. This fault line is thought to be the dividing zone between two different sub-continents, the North American plate and the Avalon plate. This location in Palermo displays a location where two sub-continents collided over 44 million years ago. As mentioned before, the two different rock types present at Palermo show which sub-continent is present. The phyllite dominant side represents the Avalon sub-continent. The Norumbega fault zone is a thrust fault. A thrust fault happens when horizontal compressional forces caused by a shortening or contraction of the earth's crust. When one rock slips past another one in faulting, the upper or overlaying block along the fault plane is called the hanging wall or headwall, the block below is called the footwall. Rocks in the hanging wall (above the fault) represent the rocks that reached a higher temperature (gneiss) over lie the rocks of lower temperature (phyllite). Thus indicating that metamorphic temperatures decreased with depth at the fault. This fault has been dormant for millions of years with little seismic activity. This fault poses little threat to humans or human activities in Maine, for example buildings, roads, and bridges.
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