Geologic units in Strafford county, New Hampshire

Additional scientific data in this geographic area

Concord Granite (Late Devonian) at surface, covers 19 % of this area

Gray two-mica granite, locally grading to tonalite.

Perry Mountain Formation, undivided (Lower? - Middle? Silurian) at surface, covers 16 % of this area

Sharply interbedded quartzites, light-gray nongraphitic metapelite, and "fast-graded" meta-turbidites. Coticule layers common.

Merrimack Group, Berwick Formation (Ordovician? - Silurian?) at surface, covers 13 % of this area

Purple biotite-quartz-feldspar granofels or schist and interbeds of calc-silicate granofels and minor metapelites. Stratigraphic sequence with respect to Eliot Formation uncertain

Upper part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 10 % of this area

Rusty-weathering, pelitic schist, metasandstone, and local coarse-grained metasandstone lentils; calc-silicate pods common; minor coticule. Probably equivalent to member C of Rangeley Formation of Maine.

Merrimack Group, Eliot Formation (Ordovician? - Silurian?) at surface, covers 7 % of this area

Gray to green phyllite, calcareous quartzite, quartz-mica schist, and well-bedded calc-silicate.

Exeter Diorite (Early Devonian) at surface, covers 7 % of this area

Includes associated intrusive rocks of southeastern New Hampshire; pyroxene and pyroxene-hornblende diorite and gabbro, along with minor granodiorite and granite.

Lower part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 7 % of this area

Gray, thinly laminated (5-25 mm) metapelite with local lentils of turbidites and thin quartz conglomerates in western New Hampshire. Sparse calc-silicate pods and coticule. Probably equivalent to member B of Rangeley Formation of Maine.

Littleton Formation, undivided (Lower Devonian; Siegenian) at surface, covers 7 % of this area

Gray metapelite and metawacke and subordinate metavolcanic rocks; generally, but not everywhere, conformable with underlying Fitch or Madrid Formations. Fossiliferous in western New Hampshire.

Mesoperthitic biotite granite (Early Cretaceous) at surface, covers 6 % of this area

Pink Conway-type granite of Kingsley (1931).

Biotite tonalite (Early - Late Devonian) at surface, covers 3 % of this area

Dark-gray; found in southeastern and western New Hampshire.

Merrimack Group, Kittery Formation (Ordovician? - Silurian?) at surface, covers 2 % of this area

Tan, graded-bedded, calcareous metasandstone and purple and green phyllite. Grades into the Eliot formation but facing direction is uncertain.

Smalls Falls Formation, undivided (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers 1 % of this area

Very rusty weathering, thinly bedded sulfidic-graphitic schist and pyrrhotitic calc-silicate granofels. Eastern facies equivalent to lower part of the Fitch Formation. Locally mapped as Francestown Formation of Nielson (1981) in southern New Hampshire.

Two-mica granite of northern and southeastern New Hampshire (Early - Late Devonian) at surface, covers 0.7 % of this area

Similar to Concord Granite.

Merrimack Group, Berwick Formation, Gove Member (Ordovician? - Silurian?) at surface, covers 0.5 % of this area

White muscovite schist. Equivalent to the Gonic Formation of Hussey (1962).

Madrid Formation (Upper Silurian?) at surface, covers 0.3 % of this area

Massive to weakly foliated, purple biotite-feldspar granofels, layered calc-silicate, and dark pelitic-sulfidic schist containing calc-silicate pods in upper member; an eastern facies equivalent to the upper part of the Fitch Formation. Locally mapped as the Warner Formation of Nielson (1981) in southern New Hampshire.

Porphyritic biotite granite (Cretaceous) at surface, covers 0.3 % of this area

Pink to gray; hastingsite or riebeckite in some varieties.

Merrimack Group, Eliot Formation, Calef Member (Ordovician? - Silurian?) at surface, covers 0.3 % of this area

Black phyllite at western contact of the Eliot Formation.

Augite-hornblende-biotite gabbro (Cretaceous) at surface, covers 0.2 % of this area

Fine- to coarse-grained.

Winnipesaukee Tonalite (Early Devonian) at surface, covers 0.1 % of this area

(Winnipesaukee Quartz Diorite of Billings, 1955) - Gray, massive to foliated tonalite and minor quartz diorite, granodiorite, and granite. Probably coeval with Spaulding Tonalite.

Devonian - Silurian Rindgemere Formation lower member (Devonian - Silurian) at surface, covers < 0.1 % of this area

Devonian - Silurian Rindgemere Formation lower member

Devonian - Silurian Rindgemere Formation upper member (Devonian - Silurian) at surface, covers < 0.1 % of this area

Devonian - Silurian Rindgemere Formation upper member

Hornblende diorite (Cretaceous) at surface, covers < 0.1 % of this area

Coarse-grained to porphyritic.

Devonian - Precambrian Z Gonic Formation (Devonian - Precambrian Z) at surface, covers < 0.1 % of this area

Devonian - Precambrian Z Gonic Formation

Rhyolite and fine-grained granite (Cretaceous) at surface, covers < 0.1 % of this area

Includes some ignimbritic caldera-fill and minor intrusive rocks (part of Ossipee Mountain Complex of Kingsley, 1931); also some aphanitic gray, black, or tan quartz-feldspar porphyry.

Silurian - Precambrian Z Kittery Formation (Silurian - Precambrian Z) at surface, covers < 0.1 % of this area

Silurian - Precambrian Z Kittery Formation

Devonian - Silurian Towow Formation, conglomerate (Devonian - Silurian) at surface, covers < 0.1 % of this area

Devonian - Silurian Towow Formation conglomerate

Silurian - Precambrian Z Eliot Formation (Silurian - Precambrian Z) at surface, covers < 0.1 % of this area

Silurian - Precambrian Z Eliot Formation

Silurian - Precambrian Z Berwick Formation (Silurian - Precambrian Z) at surface, covers < 0.1 % of this area

Silurian - Precambrian Z Berwick Formation

Devonian - Silurian Towow Formation (Devonian - Silurian) at surface, covers < 0.1 % of this area

Devonian - Silurian Towow Formation

Rangeley Formation, Ribbon-banded calc-silicate of eastern New Hampshire (Lower Silurian (Llandoverian)) at surface, covers < 0.1 % of this area

Probably equivalent to Patch Mountain Member of the Sangerville Formation (Llandoverian and Wenlockian) of central Maine.