CHAPTER
TWO: PHYSICAL LANDSCAPE FEATURES
GEOLOGY
The geology of Branford is dominated by basalt and shale deposits
towards the northern and western portions of the Town and granite
and gneiss deposits along the central and eastern portions of the
Town (Figure 1: Geology).
Most of these deposits are of Mesozoic Era origins and were formed
between 225 million to 65 million years ago. Much of the geology
runs in a diagonal from northeast to southwest and can be divided
into sections based on fault line scarps and rock contacts.
In the northwestern portion of the Town, there is a prominent high
angle fault (Eastern Border Fault of the Totoket Mountain Range)
that cuts across the area on a diagonal (Figure
1: Geology). This land feature most probably was formed during
the mid Mesozoic Era, in the period known as the Jurassic. It is
a fault line that contains the Town's highest natural elevations
and much of the Saltonstall watershed and is most evident as one
travels along Brushy Plain Road. The elevations in this area are
steep and highly contoured and the bedrock in this section is dominated
by basalt (volcanic in origin) and sandstones with some shales (sedimentary
rock) mixed throughout. Other bedrocks here include hornblendes
(ferromagnesian silicates), arkose brownstones (sandstones) and
dolerite (ophidic diabase).
Just south of the Eastern Border Fault, there are a series of smaller faults and a sandstone (Portland Arkose) outcrop that extends from the high angled fault. The southern-most portion of the Town's western flank is a gneissic deposit that is probably continental in origin.
Along much of the central and eastern portions of the Town, the bedrock is dominated by gneisses and granites including the Branford Gneiss in the center of Town and the Stony Creek granites and gneisses along the eastern portions of Town. The latter, the Stony Creek granite, is one of the most famous granites because of its use in building materials of such places as Grand Central Terminal in New York City.
The geology of the region has had an impact on land-use and economics of the Town. Besides the Stony Creek Granite noted above, trap rock has also been mined in the area (e.g., the south end of Beacon Hill). Trap rock is rock that was laid down by magma flows as lava dikes and/or flow rocks. These materials are cut and broken into pieces of various sizes and used for road-beds and other construction activities (e.g., stone armor at outfall pipes). Glacial erratic and till (together are referred to as glacial debris) have been quarried as well and make up a significant portion of the Tilcon mining in the area. This glacial debris is also used for road-beds, foundations and other activities where adequate drainage and compaction are important.
SOILS
Due to the impact of glaciers during the Pleistocene, many areas of Branford were scraped clean of their soils, and bedrock is still exposed in many places. In areas where soil has developed they tend to be fairly young when compared to more southerly regions of the country.
The soils of Branford (Figure
2; Soils) are the result of extensive weathering and reworking
of glacial till material, exposed bedrock and some fluvial or sedimentary
deposits. Much of the soil varies between sandy loams and loams
with mucky peats locally important, particularly along the coastal
portions and larger river systems. Large sections of soil are now
classified as udorthents or soils that have been disturbed by human
activity. These are most prominent in the downtown area and along
industrial and commercial developments that follow Route 1 and Interstate
95, in particular.
Although there are dozens of soil types within the Town, the soils in Town can be divided into six main variants; Wethersfield-Wilbraham-Ludlow, Hollis-Charleton, Cheshire-Yalesville, Holyoke-Cheshire, Cheshire-Holyoke and the Branford-Manchester. The Wethersfield (well drained sandy loam)-Ludlow (course loam and well drained with acidic sublayers)-Wilbraham (poorly drained course loams) variant is a course loamy mix found in level to steep grades on till uplands with a fragipan prominent in the subsoil layers. These soils tend to be poor to well drained and are found along the western and eastern portions of the Town. The Hollis-Charlton-Rock Outcrop variant is found mainly along the eastern flank of the high angle fault and is a course loamy soil found on steeper grades. The Charleton Series soils are brown to olivine in color on slopes of 3-35% and acidic sublayers while the Hollis Series is a fine sandy dark brown loam with strongly acidic sublayers over unweathered schist, gneiss, basalt and granite bedrock. The Cheshire-Yalesville variant is a well drained (3-35% slopes) course loam overlying till found primarily along the northern portions of the high angle fault. The Cheshire Series soils tend to be brown towards the surface and reddish brown in color with depth and strongly acidic in the subsurface. The Yalesville Series are course loams with a reddish brown color and more common on hillsides and only moderately acidic in subsurface layers. The Holyoke-Cheshire and the Cheshire-Holyoke variants are prominent along the northern and eastern boundaries of Town. Both types are loam to course loam soils with the Cheshire-Holyoke more common on till and exposed bedrock and the Holyoke-Cheshire typical of the broader till plains. The Holyoke Series soils are dark gray to reddish brown with depth and tend to be found in more shallow areas. Like the Cheshire soils, it tends to be strongly acidic in the subsurface layers. The Branford-Manchester variant is common through the central portion of Town and is a well drained course loam to sandy loam located over outwash plains and terraces (0-8% slopes). The Branford Series soils are the result of weathered arkose and other sandstones, shale and conglomerate and are typically reddish brown in color and loamy to course loam in texture. The Manchester Series soils are sandy and excessively drained and tend to be yellowish red gravelly mixtures. Both the Branford and the Manchester Series are strongly acidic in the subsurface layers. All of these soils can support agriculture (many are excellent for growing orchards) depending on the crop and the texture, slope and acidity of the soil.
Other soils types worth noting include the udorthents, urban and mucks. Udorthents are soils that have been disturbed by human activity, commonly development. These soils are characterized by cut or borrow areas, filled areas or some combination of both. The natural soil pedon (footprint) has been disturbed and soil permeability will vary depending on source, compaction, and use. Urban soils are those that have been disturbed and paved or built upon. They no longer are capable of supporting woodlands and subsurface layers are no longer important. Mucks are a designation that includes wetland soils ranging from poorly drained floodplain deposits to peats (e.g., Westbrook mucky peat). In Branford these soils are common along the coastal marshes and swamps associated with river and ponds. They are very dark brown to black in color and have a high percentage of organic material in the soil matrix (both decomposed and macro-organics). They are always wetland soils and are therefore, subject to both inland and coastal wetland regulations. These soils are typically poorly drained and friable in structure that renders these soils inadequate for most agriculture (too wet) and construction projects (compaction).
TOPOGRAPHY
In general, the Town of Branford slopes from the northwest to the
southeast with the highest natural land elevations associated with
the high angle Jurassic fault (sometimes referred to locally as
East Rock) (Figure 3: Topography).
As expected, there is also a general slope from the north to the
south as one approaches the coast. The highest elevations in Town
are about 320 feet above sea level and the lowest are just below
sea level (negative 2 ft) in the rivers and mud flats exposed to
tides. Much of the Town (particularly the central portion of the
Town) lies at about 50 to 70 ft above sea level except in those
areas in proximity to the major rivers (i.e., Branford River). The
topography also delineates the watersheds in town with the Branford
River making up the largest drainage way (see Water
Resources Chapter).
Topography and elevations will often help determine the value of a parcel of land. If the parcel is too steep, building and farming cannot be accomplished and the land value declines. The proper relief on the landscape assures drainage and often helps dictate soil properties. A more gradual slope also requires less engineering and fewer expenses to develop. Lower elevations often denote proximity to water. Although many people prefer lands at these lower elevations for the amenities they offer (e.g., boating, coastal views), they also are problematic because of the danger they pose to flooding. Some of Branford's most expensive parcels of land are also some of the most exposed areas to potential storm damage and flooding. Except for controlling building in a wetland or watercourse, there is presently no plan to reduce or eliminate development in these areas.
|
