Sugarloaf Formation

Reddish-brown to pale red arkose, and gray sandstone, gray siltstone, and black shale interpreted as lake beds.
State Massachusetts
Name Sugarloaf Formation
Geologic age Lower Jurassic
Lithologic constituents
Major
Sedimentary > Clastic > Sandstone > Arkose (Bed)
Sedimentary > Clastic > Sandstone (Bed)
Minor
Sedimentary > Clastic > Siltstone (Bed)
Sedimentary > Clastic > Mudstone > Shale > Black-shale (Bed)
Comments Part of Mesozoic Basins (Jurassic and Triassic Rocks); Sedimentary and Volcanic Rocks of Deerfield and Northfield Basins. Secondary unit description per MA003 as reported in USGS Geologic Names lexicon (ref. MA024): Assigned to Newark Supergroup and revised to include all sedimentary strata in the Deerfield basin below the Deerfield Basalt or its projected horizon. The Late Triassic-Early Jurassic boundary is arbitrarily drawn through clastic rocks consisting of coarse-grained, locally conglomeratic arkose interbedded with sandstone and siltstone below a Lower Jurassic palynofloral zone in gray mudstone just below the base of the Deerfield Basalt. The Sugarloaf is continuous with and lithologically similar to the New Haven Arkose in the Hartford basin (Robinson and Luttrell, 1985).
References
NGMDB product
Counties Franklin