Formations of Merrimack Group recognized as valid units in northeastern MA. Kittery Quartzite is revised to Kittery Formation following usage of Novotny (1963) and Hussey (1968). Age of Kittery is Silurian or Ordovician because it is intruded by granodiorite of Newburyport Complex (name revised) dated as Silurian and Ordovician (R.E. Zartman and R.S. Naylor, written commun., 1981). Eliot and Berwick Formations remain as probable Silurian age on basis of tentative correlation with similar rocks in central ME (Osberg, 1968). Stratigraphic order within Merrimack Group is uncertain, but it appears that Kittery is basal unit. [GNC records indicate that the names Merrimack Formation or Merrimack Quartzite are no longer valid anywhere.]

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

Kittery, Eliot, and Berwick Formations are shown, but they are not assigned to Merrimack Group. [No explanation as to why. Merrimack still good usage.]

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

Used as Merrimack Group, consisting of Berwick, Eliot, and Kittery Formations. Ordovician(?) to Silurian(?) age is based on isotopic age determinations of approx 440 and 420 Ma from detrital zircons from the Berwick by J.N. Aleinikoff (oral commun., 1994). Report includes geologic map, cross sections, correlation chart, and four 1:500,000-scale derivative maps.

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