The story is not complete without mention of the last modifying influence to affect this region. Approximately one million years ago the first of perhaps three glacial advances began. These large glacial masses, termed continental glaciers, slowly advanced southward over the northern sections of the United States and covered a vast region with a thick sheet of ice. As these ice masses rode over the Coolidge Park region they tended to round-off irregular features of the landscape and to fill in certain low regions with their transported rock debris. The rather smooth outlines of the hills in Coolidge Forest Park and the sand and gravel deposits so apparent adjacent to nearby streams tell the story of these glacial advances and subsequent withdrawals. Other evidence of the overriding ice is seen in the presence of scratch marks, termed glacial striae, which were produced by fragments of rock as they were dragged by the moving ice across the underlying rocks. Along the east bank of Broad Brook and approximately two hundred yards south of the bridge at Five Corners, abundant glacial striae are clearly displayed. The orientation of these striae indicates that the glacier producing them moved from north north-west to the south south-east.
Since the recession of the last ice sheet, which took place several thousand years ago, the general appearance of the Coolidge Park region has changed very little. The streams have cut their valleys somewhat deeper and some of the glacial sands and gravels have been redistributed. A few thousand years ago Coolidge State Forest Park looked quite the same as it does today (See cross section C, [Fig. 5]).
SIDE TRIPS OF GEOLOGICAL INTEREST
Gold Panning
There are several locations immediately adjacent to the Calvin Coolidge State Forest Park where some gold can still be obtained from stream sands and gravels. The abandoned town of Five Corners offers the park visitor ample chance to “try his luck.” In fact, several local people still obtain small gold nuggets and a good deal of gold dust from the streams in the vicinity of Five Corners (See [geologic map] for geographic location). Other possible “panning” locations would include Reading Pond Brook, Buffalo Brook and Kingdom Brook. The gold which is found is probably derived from nearby gold-bearing quartz veins.
The equipment needed for an afternoon of panning is relatively simple to obtain. A wide, rather shallow pan with gently sloping sides is really all that is needed. Gravel and sand, which you find concentrated on the upstream side of natural rock riffles in the stream bed should be placed together with water in your pan. Then the pan should be rotated and the lighter rock materials decanted. The heavy gold will be concentrated in the bottom of the pan.
Asbestos and Talc
For you who might be interested in mineral collecting it is suggested that a trip to an old pit near Five Corners might prove rewarding. Walk down Broad Brook from the bridge at Five Corners until you locate the first small tributary entering on your left. Turn left up this tributary and continue to walk for approximately one hundred yards. On your left you will see the remains of a pit dug into the side of the stream bank which, at this location, is lined with rocks of the Ottauquechee formation. You will quickly note the fibrous asbestos in the walls of this pit; however, if you wish to collect specimens of this mineral be extremely careful and avoid standing beneath any overhanging rock material. Talc, which feels “soapy” to the touch, is also abundant in this immediate area. This asbestos and talc occur in a lenticular-shaped body which is perhaps eight hundred feet wide and of an undetermined length. It is not certain when these minerals formed; however, it was probably in the early history of the region.
Garnet
Good specimens of garnet can be found in the rocks of the Bethel formation. These garnets are not of gem quality but still offer good collecting for the amateur mineralogist. Good collecting localities exist along State Highway 100A and at several different spots within the Park itself. A hike along the northern boundary of the Park would intersect several excellent collecting spots.