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Map showing publication footprint
  • Usage in publication:
    • Mackworth slate*
  • Modifications:
    • Named
  • Dominant lithology:
    • Slate
    • Quartzite
  • AAPG geologic province:
    • New England province
Publication:

Katz, F.J., 1917, Stratigraphy in southwestern Maine and southeastern New Hampshire, IN Shorter contributions to general geology, 1917: U.S. Geological Survey Professional Paper, 108-I, p. 165-177.


Summary:

Named Mackworth slate for Mackworth Island, Casco Bay, ME. Consists of quartzite and quartz-chlorite-mica slate, in beds less than an inch to 2 or 3 feet thick. Rocks dominantly siliceous and laminated and characterized by abrupt alternations from flinty to chloritic slate. Range from white through drabs and light grays to dark grays and browns. Estimated thickness is 100 feet. Top of formation is unknown. Unit is uppermost formation of Casco Bay group. Probably overlies Jewell phyllite. Age is Pennsylvanian(?).

Source: GNU records (USGS DDS-6; Reston GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Macworth Formation
  • Modifications:
    • Revised
    • Age modified
  • AAPG geologic province:
    • New England province
Publication:

Hussey, A.M., II, 1988, Lithotectonic stratigraphy, deformation, plutonism, and metamorphism, greater Casco Bay region, southwestern Maine, IN Tucker, R.D., and Marvinney, T.G., eds., Studies in Maine geology; igneous and metamorphic geology; Volume 1: Maine Geological Survey, p. 17-34.


Summary:

Macworth [Mackworth] Formation is the uppermost unit of the Casco Bay Group. It is interpreted to be either the equivalent of the Vassalboro Formation of the Kearsarge-central Maine sequence or the Berwick Formation of the Merrimack Group. On the north end of Great Chebeague Island in Casco Bay, grayish brown phyllite conformably overlying the Jewell Formation is mapped and correlated as part of the Macworth, thus establishing its stratigraphic position as the highest of the Casco Bay units. The author favors its correlation with the lower part of the Vassalboro, which would establish the age of the Macworth as Middle to Late Ordovician.

Source: GNU records (USGS DDS-6; Reston GNULEX).


For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

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