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Mineral Resources > Online Spatial Data > Geology > by state > New Hampshire Geology

Geologic units in Merrimack county, New Hampshire

[Additional scientific data in this geographic area]

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

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

Lithology: granofels; quartz-feldspar schist; meta-argillite

Lower part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 19 % of this area

Lower part of Rangeley Formation - 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.

Lithology: meta-argillite; meta-conglomerate; calc-silicate rock

Perry Mountain Formation, undivided (Lower? - Middle? Silurian) at surface, covers 5 % of this area

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

Lithology: quartzite; meta-argillite; metasedimentary rock

Biotite tonalite (Early - Late Devonian) at surface, covers < 0.1 % of this area

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

Lithology: tonalite

Massabesic Gneiss Complex (Late Proterozoic) at surface, covers 0.6 % of this area

Massabesic Gneiss Complex - Migmatite consisting of pink, foliated biotite granite intruding gneissic and granulose metasedimentary and metavolcanic rocks in southeastern New Hampshire.

Lithology: migmatite; granite; metasedimentary rock; metavolcanic rock

Smalls Falls Formation, undivided (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers 3 % of this area

Smalls Falls Formation, undivided -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.

Lithology: schist; granofels

Two-mica tonalite (Early - Late Devonian) at surface, covers 0.5 % of this area

Two-mica tonalite - Similar to Concord Granite; found in south-central New Hampshire.

Lithology: tonalite

Littleton Formation, Upper unnamed member (Lower Devonian) at surface, covers 2 % of this area

Littleton Formation, Upper unnamed member - Light-gray metaturbidite, lithologically identical to, and probably correlative with, the Seboomook Formation of Maine. Coticule layers common.

Lithology: metasedimentary rock

Bethlehem Granodiorite (Early Devonian) at surface, covers < 0.1 % of this area

Bethlehem Granodiorite (Bethlehem Gneiss of Billings, 1955) - Gray, strongly foliated biotite-muscovite granodiorite and associated tonalite and granite.

Lithology: granodiorite; tonalite; granite

Littleton Formation, undivided (Lower Devonian; Siegenian) at surface, covers 2 % of this area

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

Lithology: metasedimentary rock; metavolcanic rock

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

Concord Granite - Gray two-mica granite, locally grading to tonalite.

Lithology: granite; tonalite

Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro (Early Devonian - Late Devonian) at surface, covers 0.3 % of this area

Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro - Spatially associated with Spaulding Tonalite plutons.

Lithology: quartz diorite; diorite; gabbro

Fitch Formation (Upper Silurian; Pridolian and Ludlovian) (Upper Silurian - (Pridolian and Ludlovian)) at surface, covers < 0.1 % of this area

Fitch Formation - Metamorphosed limestone, calcareous sandstone, siltstone, and dark pelitic schist; lower contact is disconformable on the Clough Quartzite. Fossiliferous.

Lithology: marble; quartzite; phyllite; pelitic schist

Kinsman Granodiorite (Early Devonian ) at surface, covers 25 % of this area

Kinsman Granodiorite - (Kinsman Quartz Monzonite of Billings, 1955) - Foliated granite, granodiorite, tonalite, and minor quartz diorite; large megacrysts of potassium feldspar characteristic; garnet locally abundant.

Lithology: granite; granodiorite; tonalite; quartz diorite

Littleton Formation, Lower unnamed member (Lower Devonian) at surface, covers 2 % of this area

Littleton Formation, Lower unnamed member - Thinly or poorly bedded aluminous lower part, somewhat rusty. Rare quartzite lentils. Carrabassett Formation in northwestern Maine is probably correlative.

Lithology: metasedimentary rock; metavolcanic rock; quartzite

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

Upper part of Rangeley Formation - 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.

Lithology: pelitic schist; metasedimentary rock; calc-silicate rock

Madrid Formation (Upper Silurian? ) at surface, covers 2 % of this area

Madrid Formation - 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.

Lithology: granofels; calc-silicate schist; pelitic schist

Spaulding Tonalite (Early Devonian) at surface, covers 9 % of this area

Spaulding Tonalite (Spaulding Quartz Diorite of Fowler-Billings, 1949) - Weakly foliated to nonfoliated, spotted biotite quartz diorite, tonalite, granodiorite, and granite; garnet and muscovite may or may not be present.

Lithology: quartz diorite; tonalite; granodiorite; granite