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Middlebury and Chazy Limestone, Undifferentiated Youngman and Carman Formations, Day Point Member

Middlebury and Chazy Limestone, Undifferentiated Youngman and Carman Formations, Day Point Member - Calcareous quartz sandstone, and calcarenite; orange-weathered dolomitic siltstones are common in eastern areas.
NameMiddlebury and Chazy Limestone, Undifferentiated Youngman and Carman Formations, Day Point Member
Geologic ageOrdovician
Original map labelOmid
CommentsPart of Champlain and Vermont Valleys, Chazy Group Secondary unit description per VT006:Stratigraphy of the Middle Ordovician Day Point Formation of the Chazy Group is complex. Lateral changes in lithology produce sequences that are unique at different localities around the Champlain Valley of NY and VT. The formation comprises seven lithologies: Highly bioturbated sandstone; bioturbated, brachiopod-rich wackestone; planar cross-bedded, interlayered sandstone and sandy packstone; interlayered sandstone and shale grading into interlayered sandstone and limestone; grainstone with mound-shaped bryozoan reefs or thin, non-reefal, layers of bryozoa and planar laminated and cross-stratified beds; fine-grained calcareous sandstone with planar and herringbone cross-bedding; and planar cross-bedded packstone with bryozoan reefs or thin non-reefal layers of bryozoa. This study has revealed more sandstone units in the lower portion of the Day Point than have been previously noted. The sandstone units are followed by deeper water carbonates (Falkenberg and Mehrtens, 1993).
Primary rock typesandstone
Secondary rock typecalcarenite
Other rock typessiltstone
Lithologic constituents
Sedimentary > Clastic > Sandstone > Arenite > Calcarenite
Sedimentary > Clastic > Sandstone (Calcareous)calcareous quartz sandstone
Sedimentary > Clastic > Siltstoneorange-weathered dolomitic siltstones
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.
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.
Falkenberg, Jessica and Mehrtens, C.J., 1993, A re-evaluation of the stratigraphy and sedimentology of the Day Point Formation (Chazy Group) [abs]: The Green Mountain Geologist, v. 20, no. 1, p. 6-7.
Geographic coverageAddison - Chittenden - Grand Isle

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