Rocks of Shelburne
Most of Shelburne is underlain by a series of sedimentary rocks, first formed 400-500 million years ago along the shore of a warm, shallow ocean (see Geologic History for more information). The physical features of these rocks hold clues to their original environment, which helps geologists interpret their history. This page gives an overview of Shelburne geology, with a closer look at a few important or interesting rocks and features. (Images taken by Eric Butler & Jens Hilke)
Specific formations: a closer look
Iberville Shale
Danby Formation
The Iberville Shale is a grey, thinly layered rock that was deposited in deep ocean waters, capping the sedimentary sequence of the Champlain Valley. Although it is much younger than most other sedimentary rocks in the area, it is usually found below them because of the Champlain Thrust, the great fault which shoved thousands of feet of rock over the Shale. Because of this, the shale appears greatly deformed, with folds, faults, and cracks prevalent throughout the formation. It forms much of the Shelburne lakeshore. The Danby consists of a sandstone containing a great deal of the mineral dolomite. The rocks preserve many sedimentary features that provide clues to their environment of deposition, such as wave ripples (top) and worm burrows (below). These sandstones probably formed in a shallow beach environment where waves continually worked the sandy sediments and primitive organisms burrowed through the sediment. The best exposures of these features can be found at Shelburne Falls.
Monkton Quartzite
Marble/Dolostones
A thick deposit of red sandstone, the Monkton is one of the most distinctive formations in the Champlain Valley. It contains a wealth of preserved sedimentary features, including wave ripples (top), rain-drop imprints, old river channels, trilobite tracks, worm burrows, and more. The Monkton is very resistant and tends to form the tops of ridges, where it often preserves glacial features like striations (grooves cut by rocks in the glaciers, below). Several formations around Shelburne are composed of old marine limestones that have since been altered to form marbles or dolostones. These rocks were valuable sources of lime for early settlers, and produce nutrient-rich soils for natural communities and farming. The marbles are also quite susceptible to the natural acids in rainwater, and so tend to dissolve quite easily into large cracks and sinkholes (below) which produce some very unique terrain.
Local Rocks