Essay on The Deerfield Basin Of The Connecticut River Valley
On September 12, and October 3, 2016, we stopped at 6 locations north of Northampton in the Deerfield Basin of the Connecticut River Valley (Figure 1). The purpose of these stops is to examine rocks, interpret depositional environments for each rock formation, and discuss the geologic history of the Deerfield Basin based on observations and interpretations. Early Mesozoic lithospheric extension led to the development of a long sequence of rift basins. The Deerfield basin is the erosional remnant of one of these rifts exposed in North America after Pangaea separated during the Carnian (Olsen et al., 1992). Today, the valley formations include Pre-Triassic basement, Late-Triassic Sugarloaf Arkose, Early-Jurassic Fall River Beds, Jurassic Deerfield Basalt, Jurassic Turner Falls Sandstone, and Jurassic Mt. Toby Conglomerate.
Stop 1, located on Rt. 2 West at the Longview Gift Shop, the Gile Mountain Formation is exposed alongside the road. The Devonian Gile Mountain Formation is a dark grey phyllite, with abundant muscovite revealing a glossy sheen micaceous matrix. The formation also contains subangular oxidized garnets, approximately pebble sized. The formation exhibits poor bedding and platy cleavage (Table 1).
Stop 2, located on Country Club Road, the Sugarloaf Arkose is exposed underneath the route 91 overpass. The Sugarloaf Arkose is 2000 m thick, and varies from arkose, sand, to basalt, with a fine-grained glassy matrix. The angular to round…