The _Ottauquechee formation_, next above the Pinney Hollow formation and therefore younger in age, was named for the Ottauquechee River along which this formation is well exposed and was first studied in detail. The Ottauquechee River is located just north of Calvin Coolidge State Forest Park where it flows through the towns of Bridgewater and Bridgewater Corners. You can see this formation along State Highway 100A approximately nine-tenths of a mile north of the Park entrance road. Here, the formation crops out on the west side of the road, or on your left if traveling toward Bridgewater Corners (See photograph, Fig. 4). A hike along the recently diamond-blazed Coolidge Forest trail, which leads from behind the Ranger’s cabin to the Picnic area, affords an almost continuous view of this formation. The highly resistant quartzite layers within the Ottauquechee formation are very conspicuous features along this trail as they form several ridges trending across the footpath. The Ottauquechee formation, estimated to be 3,000 feet thick, contains rocks which contrast sharply with the underlying pale-green schists. The formation consists of alternating black phyllite and layers, up to several feet thick, of dark- to light-colored quartzite. 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. Pinney Hollow shallow marine water conditions remained, but for some reason, such as a barrier of islands or shallow water sand bars, the circulation of ocean waters was hindered, leading to the accumulation of stagnant organic matter on the ocean bottom. This organic matter gives the Ottauquechee phyllite and some quartzites a dark to black color. No fossils have been found in the Ottauquechee formation of the Coolidge Forest Park, but, as with the Pinney Hollow formation, evidence from other areas indicates a Cambrian or perhaps Ordovician age for this formation. [Illustration: Figure 4. The Ottauquechee formation as exposed approximately nine-tenths of a mile north of the Park entrance road and on the west side of State Highway 100A. Note the massive quartzite layers above, the black phyllite below.]