Harry W. Dodge

“ When igneous or sedimentary rocks are subjected to metamorphism they tend to lose their original appearance as some minerals are completely changed or altered into new minerals and most of the original minerals are oriented in one or more preferred directions. ”

“ Each summer hundreds of eager campers, picnickers, hikers and sportsmen visit the Pinney Hollow-Bradley Hill recreational area of the Calvin Coolidge State Forest Park. This area is located a few miles north of Plymouth, Vermont, and is easily reached via State Route 100A from either Plymouth or Bridgewater Corners (See index map of Vermont, geological map) . The excellent camping and recreational facilities coupled with the natural scenic beauty of this region provide many visitors with an irresistible urge to return, summer after summer, to this same spot. ”

“ Fossils can be seen in some of the varieties of marble, which demonstrates that under certain conditions recognizable fossils do occur in metamorphic rocks. Most of the marble seen in this exhibit is quarried nearby; however, for safety reasons visitors are not allowed to enter the quarries. It is interesting to note that these marbles are about the same age as the rocks seen in Coolidge State Forest Park.
Footnotes
[1] A rock, for those desiring a more technical definition, is any relatively hard, naturally occurring, combination of minerals which form an essential part of the earth. ”

“ Since plants and animals changed through time and because their remains are found throughout the world, it is possible to erect a worldwide time scale based upon animal and plant evolution. In short, the fossils found in particular rock are characteristic representatives of the life at the time that rock originated and the fossils 6 found could have been entombed only at that time. One stratum, therefore, would have a total fossil assemblage quite different from the stratum above or below. ”

“ The black carbonaceous color of the phyllites and dark quartzites indicate the presence of life, either animal or plant, during the original deposition of the sediments forming these rocks. The phyllite was, before metamorphism, a black shale which formed from black muds rich in organic matter. From studies done in areas where black muds are accumulating today it seems quite probable that the ocean waters of Ottauquechee time were of a restricted nature, that is to say, the waters were stagnant due to the lack of oxygen. ”

“ Metamorphism has since converted many of the shale minerals into mica flakes and some of the sandy shales produced crystals of the mineral garnet. The pale-green color of the Pinney Hollow schist is caused by the presence of the green mica-like mineral, chlorite, which developed during the process of metamorphism.
Figure 3. The Pinney Hollow Historical Monument embedded in the Pinney Hollow formation. The darker rock consists of pale-green schist and the white areas are quartz layers and lenses. ”

“ Then, you are invited to travel back through 550 million years of time to see just why Coolidge State Forest Park is as it is today and what it was like in the distant past.
4 BASIC PRINCIPLES AND “TOOLS”
To many of you rocks are just “rocks” and very little thought has been given to any history which might be gained from their study. Probably even fewer of you realize that literally billions of years of Earth history can be derived directly from the rock record. Most geologists consider the Earth to be nearly four billion years old with man entering the picture a mere million or so years ago. ”

“ The layered appearance of sedimentary rocks is one of their most characteristic features and these rocks are said to be bedded or composed of many individual beds of sedimentary rock. Sandstone, composed of sand size particles; shale, originally mud; and limestone, once lime-rich mud, are examples of sedimentary rocks.
7
Metamorphic rocks result when igneous or sedimentary rocks are subjected to abnormal heat and pressure. Folding or faulting [2] of rocks within the earth’s crust or deep burial beneath overlying rocks or sediments commonly produce metamorphism. ”

“ Since the formations trend in a north-north-west direction, the hills and valleys are also oriented in this general direction, as the different resistive qualities of the rocks are presented in this pattern. ”