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 …show more content…
The Sugarloaf Arkose makes up the basal unit and reveals a fluvial and alluvial arkose environmental deposition. The dominant sandstone grain size is evidence of a fluvial depositional environment at Stop 2. The Late-Triassic age alluvial and fluvial arkose of the Deerfield Basin makes up the main strata sequence. Stop 3 reveals the Deerfield Basalt followed by lava flow in the strata column. The transition between Fall River Beds and Sugarloaf Arkose is at the Triassic and Jurassic boundary (Figure 5). The Fall River Beds at stop 4 and Sugarloaf Arkose show a sequence of grey and red lacustrine sandstone, siltstone, and pebbly sandstone. The lower portion of this sequence is interbedded with basalt (Olsen et al.,