Bascom Formation, and undifferentiated Luke Hill, Naylor Ledge and Hastings Creek Limestones (VTOb;0)

State	Vermont
Name	Bascom Formation, and undifferentiated Luke Hill, Naylor Ledge and Hastings Creek Limestones
Geologic age	Ordovician
Original map label	Ob
Comments	Part of Champlain and Vermont Valleys, Beekmantown Group Secondary unit desription per VT012: Bascom Subgroup is defined as the entire carbonate clastic succession of the Beekmantown, representing the core of the group. This sequence was referred to as "Calciferous sand-rock" by Eaton (1824). Bascom name is appropriate since Bascom Ledges consist of various portions of this sequence. Included within this Subgroup are (ascending) Cutting Hill Formation (Cutting Formation redefined and renamed), Lemon Fair Formation (named), and Fort Cassin Formation. Unit overlies Whitehall Dolostone and underlies Providence Island Formation, both of Beekmantown Group. Age is Early Ordovician. [Rank of subgroup is not recognized in the NACSN.] (Washington and Chisick, 1988).
Primary rock type	dolostone (dolomite)
Secondary rock type	limestone
Other rock types	marble; sandstone; quartzite; sedimentary breccia
Lithologic constituents	Minor Metamorphic > Metasedimentary > Metaclastic > Quartzite Sedimentary > Clastic > Sandstone (Calcareous) Metamorphic > Metasedimentary > Metacarbonate > Marble (Bed)irregular dolomitic layers, thin sandy laminae, and slaty or phyllitic partings characterize limestone and marble of lower, middle, and upper parts of the Bascom, respectively Sedimentary > Carbonate > Limestone (Bed)irregular dolomitic layers, thin sandy laminae, and slaty or phyllitic partings characterize limestone and marble of lower, middle, and upper parts of the Bascom, respectively Sedimentary > Carbonate > Dolostone (Bed)irregular dolomitic layers, thin sandy laminae, and slaty or phyllitic partings characterize limestone and marble of lower, middle, and upper parts of the Bascom, respectively Incidental Sedimentary > Clastic > Sedimentary-breccia (Bed)limestone breccia
Map references	Nicholson, S.W., Dicken, C.L., Horton, J.D., Foose, M.P., Mueller, J.A.L., and Hon, Rudi, 2006, Preliminary integrated geologic map databases for the United States: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, Rhode Island, and Vermont: U.S. Geological Survey Open-File Report 2006-1272. [http://pubs.er.usgs.gov/publication/ofr20061272]
Unit references	Doll, C.G., Cady, W.M., Thompson, J.B., Jr., and Billings, M.P., 1961, Centennial Geologic Map of Vermont: Vermont Geological Survey, Miscellaneous Map MISCMAP-01, scale 1:250,000. Ratcliffe, N.M., 1994, Changes in stratigraphic nomenclature in the eastern cover sequence in the Green Mountain massif from Ludlow to West Bridgewater, Vermont, IN Stratigraphic notes, 1992: U.S. Geological Survey Bulletin, 2060, p. 1-10. [http://pubs.er.usgs.gov/publication/b2060]
Geographic coverage	Addison - Bennington - Chittenden - Franklin - Grand Isle - Rutland