4A: Geology, Soils, and Topograph

Lenox has mountains and steep slopes on its east and west and a hilly, rare marble and limestone valley through its center. Opportunities for development are dictated by this topography. Development is easier in the marble valley due to more modest slopes and a deeper depth to bedrock than the mountainous regions. However, many rare plant and animal species rely on this valley, creating conflicts between conservation and development.

Topography

Differential erosion has created a striking contrast between the valley and bordering mountains in Lenox. Broad floodplains of the Housatonic and the rolling hills of the valley, ranging in elevation from 1000 to 1500 feet above sea level, stretch from north to south in the central portion of town. The LenoxStockbridge Range and October Mountain parallel one another on the western and eastern borders of town (Map 4A.1.) Elevations in Lenox range from approximately 950 feet above sea level at the Housatonic River to 2,124 feet above sea level atop the Lenox-Stockbridge Range.

Geologic Features

Bedrock in the Lenox-Stockbridge range and October Mountain consists primarily of quartzite, gneiss schist and is harder than and more resistant to physical and chemical weathering than other areas of Lenox. In the valley, the bedrock consists of less resistant marble (Map 4A.1). Due to the predominance of calcium-based marble and limestone at lower elevations, Lenox's valley soils tend to be very alkaline. Marble bedrock is very rare in New England and supports a unique environment filled with alkaline-loving plants and animals. Alkaline soils also partially offset the negative effects of acid rain.

Slopes

Lenox is nestled between two mountainous areas dominated by steep slopes (Map 4A.2). The steepest slopes (greater than 25 percent) are concentrated in the Lenox-Stockbridge Mountain Range to the west and October Mountain on the eastern side of the Housatonic River in the northeast corner, where the land rises steeply to the Berkshire plateau.

The soil on these steep slopes has a high potential for erosion and surface water runoff.

There is also a shallow depth to bedrock on these steep slopes resulting in a slow percolation rate. This means these areas do not drain well and so are not good locations for septic systems, significantly limiting development. The shallow depth to bedrock also creates an impractical foundation for houses. Steep slopes also limit development, but with today's technology and development pressures, such steep slopes are often not a complete deterrent, although they are still more costly to build on. Extensive grading, vegetation clearing and blasting would be needed to accommodate development on the steep slopes. These activities are detrimental to the ecosystem as well as water quality at lower elevations. The removal of vegetation and/or alteration of the soil increases potential for erosion and surface water run-off, causing potential problems to downstream and lower elevation areas. Much of the steepest land is protected from development as town conservation land or as privately held land with conservation restrictions (see Chapter 5). Slopes of less than 15 percent dominate the central portion of town. This is where most development has already occurred and where slopes make future development more appropriate.

Soils

Fine sandy loams and patches of standard loam are the most prevalent types of soil on steeper slopes (greater than 25 percent) (Map 4A.3). These soils are well-drained; however, a shallow depth to bedrock and a high water table create considerable limitations for septic systems and other development.

Despite these limitations, current septic and building technologies make building on these marginal soils possible. Throughout the valley there is predominately a mix of loam and silt loam, which are moderately well-drained. Muck soils often surround water bodies in town and are very poorly drained. Development is most suitable in places where the soil is well-drained, but in the case of Lenox, the well-drained soils occur on steep slopes with shallow depth to bedrock. Development in these areas would be difficult, costly, and could disturb plant and animal species that rely on these areas.

The United States Department of Agriculture (USDA) defines three types of important agricultural soils, all of which exist in Lenox (Map 4A.4). First is prime farmland, which exists in patches throughout the valley. T he USDA defines prime farmlands as “those that have the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops, and are also available for these uses.” However, some of this land is already developed, making it effectively unavailable for farming.

Second, the USDA designates farmland of statewide importance, which is “nearly prime farmland that economically produces high yields of crops when treated and managed according to acceptable farming methods.”

Lastly, farmland of unique importance is land that could be used to produce specific high-value crops such as tree nuts, fruits, and vegetables. Much of the farmland of unique importance in Lenox is located in wetlands. Except for certain crops such as cranberries, it would most likely be illegal to farm on these lands if they have not been continuously farmed historically.

Prime farmland and farmland of statewide importance should be a priority in locating potential community gardens, which some residents have expressed an interest in.