USGS Visual Identifier
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Geologic Unit: Merrimack

Usage:
Merrimack Group (MA*,ME*,NH*)

Age:
Ordovician(?)*
Silurian(?)*

Geologic Province:
New England province*


Areal Extent:
MA*
ME*
NH*

Type Locality:
Exposures on both sides of Merrimack River and near town of Merrimack, northeastern MA (Hitchcock, 1870).

Subunits:
Kittery, Eliot, and Berwick Formations

Unit Name History:
[Please note: only these references listed below include synopses here.]
Age modified; Overview of nomenclature (Goldsmith and others, 1982).
Not used on MA State Geol. Map (Zen and others, 1983).
NH State Geol. Map usage; Age modified; Isotopic dating (Lyons and others, 1997).
[Please note: the references listed below are taken from US geologic names lexicons, USGS Bull. 896, 1200; synopses not included here.]
Named Merrimack group, credited father with first use (C.H. Hitchcock, 1870, New Hampshire Geol. and Mineral Survey 2nd Ann. Rpt., geol. map and p. 34).
Used as Merrimac schists (C.H. Hitchcock, 1871, Official Topo. Atlas Massachusetts).
Used as Merrimack group (C.H. Hitchcock, 1873a, Boston Soc. Nat. Hist. Proc., v. 15, p. 304-309; 1873b, New Hampshire Geol. Survey Rpt. 1872, p. 14; 1874, Geology of New Hampshire, pt. 1, 508-545; 1877, Geology of New Hampshire, pt. 2, p. 588-591, 621, 658-675).
Used as Merrimack quartzite and schist; Age modified (C.H. Hitchcock, 1879, Macfarlane's Geol. Ry. Guide, p. 56-59).
Age modified (W.O. Crosby, 1880, Boston Soc. Nat. Hist. Occ. Paper, no. 3; C.H. Clapp, 1910, Igneous rocks of Essex Co., MA).
Rank reduced to Merrimack Quartzite; Age modified (B.K. Emerson, 1917, USGS Bull. 597, p. 58, corr. tbl., map).
Age modified (E.E. Fairbanks, 1927, Boston Soc. Nat. Hist., v. 38, no. 8, p. 405).
Group term used, formations assigned; Age modified (M.P. Billings, 1955, Geol. Map of New Hampshire, scale 1:250,000).
Overview; Age modified (M.P. Billings, 1956, Geology of New Hampshire, pt. 2, bedrock geology: Concord, New Hampshire State Plan. Devel. Comm., p. 43-44, 99-105).
[Please note: the following references have yet to be added from the GNC index card files. Until then, feel free to contact us if you would like complete bibliographic citations.]
Areal limits (Castle, 1965).
Extended into ME (Moench, 1970).
Age modified (Castle and others, 1975).
Merrimack Formation used; Age modified (Robinson, 1978).

Note: If you need more information, please contact Nancy Stamm (nstamm@usgs.gov).
Asterisks (*) indicate usage by the U.S. Geological Survey. Other usages by state geological surveys.

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

Slashes (/) indicate unit name usage violates the 1983 North American Stratigraphic Code. This violation may be explained within brackets ([ ]).






U.S. Department of the Interior, U.S. Geological Survey, Reston, VA, USA
URL http://ngmdb.usgs.gov/ngmdb/ngm_catalog.ora.html
Database project personnel
Last modified: 15-Jan-2013