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

Geologic units in New Hampshire (state in United States)

[Additional scientific data in this geographic area]

Gile Mountain Formation, undivided (Lower Devonian) at surface, covers 0.4 % of this area

Gile Mountain Formation, undivided - Gray to tan metawacke and schist or phyllite; gradational into Meetinghouse Slate Member but more thickly bedded and less pelitic than the member. Includes minor metavolcanic lentils.

Lithology: schist; metasedimentary rock; phyllite; slate; metavolcanic rock

Augite monzodiorite (Jurassic) at surface, covers < 0.1 % of this area

Augite monzodiorite.

Lithology: monzodiorite

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

Devonian - Silurian Rindgemere Formation upper member

Lithology: mudstone; sandstone

Ordovician gabbro/diorite/ultramafic rocks (Ordovician) at surface, covers < 0.1 % of this area

Ordovician gabbro/diorite/ultramafic rocks

Lithology: gabbro; diorite; ultramafic intrusive rock

Fine-grained granite (Jurassic) at surface, covers < 0.1 % of this area

Fine-grained granite - Commonly contains alkalic amphibole and mesoperthite.

Lithology: granite

Upper part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 6 % 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

Merrimack Group, Eliot Formation, Calef Member (Ordovician? - Silurian?) at surface, covers < 0.1 % of this area

Merrimack Group, Eliot Formation, Calef Member - Black phyllite at western contact of the Eliot Formation.

Lithology: phyllite

Granite, granodiorite, and trondhjemite (Late Ordovician) at surface, covers 0.3 % of this area

Granite, granodiorite, and trondhjemite.

Lithology: granite; granodiorite; trondhjemite

Gabbro and diabase (Middle Ordovician) at surface, covers 0.1 % of this area

Gabbro and diabase - Foliated to nonfoliated and coarse- to fine-grained; includes mafic dikes tentatively correlated with Chickwolnepy intrusions.

Lithology: gabbro; diabase

Rangeley Formation, Felsic metavolcanic rocks (Lower Silurian (Llandoverian)) at surface, covers < 0.1 % of this area

Rangeley Formation, Felsic metavolcanic rocks - Found in south-central New Hampshire.

Lithology: felsic metavolcanic rock

Ammonoosuc Volcanics (Ordovician) at surface, covers < 0.1 % of this area

Ammonoosuc Volcanics - Fine-grained chloritic and biotitic gneiss and greenstone in areas north of Bellows Falls; biotite gneiss and amphibolite south of Bellows Falls. (Southeastern Vermont).

Lithology: biotite gneiss; greenstone; amphibolite

Exeter Diorite (Early Devonian) at surface, covers 0.6 % of this area

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

Lithology: diorite; gabbro; granodiorite; granite

Hornblende granodiorite (Late Ordovician) at surface, covers < 0.1 % of this area

Hornblende granodiorite.

Lithology: granodiorite

Merrimack Group, Berwick Formation, Unnamed member (Ordovician? - Silurian?) at surface, covers 1 % of this area

Merrimack Group, Berwick Formation, Unnamed member - Contains more calc-silicate (15 percent) than does the remainder of the formation (5 percent).

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

Ammonoosuc Volcanics, Bimodal volcanic rocks (Middle - Upper Ordovician) at surface, covers 0.2 % of this area

Ammonoosuc Volcanics, Bimodal volcanic rocks.

Lithology: bimodal suite

Concord Granite (Late Devonian ) at surface, covers 5 % of this area

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

Lithology: granite; tonalite

Hornblende granodiorite of Highlandcroft pluton (Late Ordovician) at surface, covers < 0.1 % of this area

Hornblende granodiorite of Highlandcroft pluton - Contains minor tonalite and diorite.

Lithology: granodiorite; tonalite; diorite

Mesoperthitic biotite granite (Early Cretaceous) at surface, covers 0.7 % of this area

Mesoperthitic biotite granite - Pink Conway-type granite of Kingsley (1931).

Lithology: granite

Littleton Formation, Lower unnamed member (Lower Devonian) at surface, covers 1 % 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

Dead River Formation, Graded-bedded metapelite (Upper Cambrian? - Lower Ordovician?) at surface, covers 0.2 % of this area

Dead River Formation, Graded-bedded metapelite - Found in Percy quadrangle of northern New Hampshire.

Lithology: meta-argillite

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

Silurian - Precambrian Z Kittery Formation

Lithology: metasedimentary rock; phyllite

Porphyritic (alkalic feldspar) biotite granite (Late Ordovician) at surface, covers 0.2 % of this area

Porphyritic (alkalic feldspar) biotite granite.

Lithology: granite

Granite porphyry (Early Jurassic) at surface, covers 0.5 % of this area

Granite porphyry - Granite containing phenocrysts of smoky quartz and microperthite; alkalic amphibole, hornblende, and hedenbergite or fayalite may be present. "Mount Lafayette" type granite porphyry of Billings (1955).

Lithology: granite

Littleton Formation (Devonian) at surface, covers < 0.1 % of this area

Littleton Formation - Gray slate and phyllite containing interbeds of gray schistose quartzite 1/4 inch to 6 inches thick. West of Guildhall are lustrous, light to dark gray biotite-garnet phyllite and schist, some slate, and subordinate quartzite and impure quartzite. South of Bellows Falls gray phyllite passes eastward into gray mica schist containing porphyroblasts of biotite, garnet, and staurolite.

Lithology: slate; phyllite; quartzite; schist; mica schist

Madrid Formation (Upper Silurian? ) at surface, covers 0.6 % 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

Merrimack Group, Berwick Formation, Gove Member (Ordovician? - Silurian?) at surface, covers 0.1 % of this area

Merrimack Group, Berwick Formation, Gove Member - White muscovite schist. Equivalent to the Gonic Formation of Hussey (1962).

Lithology: mica schist

Merrimack Group, Berwick Formation (Ordovician? - Silurian?) at surface, covers 3 % 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

Ammonoosuc Volcanics, Volcaniclastic metagraywackes (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Ammonoosuc Volcanics, Volcaniclastic metagraywackes.

Lithology: metasedimentary rock

Littleton Formation, Volcanic lentils (Lower Devonian) at surface, covers < 0.1 % of this area

Littleton Formation, Volcanic lentils - Both mafic and felsic

Lithology: mafic metavolcanic rock; felsic metavolcanic rock

Mount Osceola Granite, Granite containing hornblende and, locally, hastingsite, ferrohedenbergite, or fayalite (Early - Middle Jurassic) at surface, covers 1 % of this area

Mount Osceola Granite, Granite containing hornblende and, locally, hastingsite, ferrohedenbergite, or fayalite.

Lithology: granite

Perry Mountain Formation, undivided (Lower? - Middle? Silurian) at surface, covers 3 % 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

Kinsman Granodiorite (Early Devonian ) at surface, covers 9 % 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

Newburyport Complex (early Late Silurian) at surface, covers < 0.1 % of this area

Newburyport Complex - Gray, medium-grained tonalite and granodiorite.

Lithology: tonalite; granodiorite

Lower part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 5 % 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

Conway Granite (Middle - Late? Jurassic) at surface, covers 4 % of this area

Conway Granite - Typically pink, coarse-grained mesoperthitic biotite (amphibole-free) granite; locally fine-grained or porphyritic.

Lithology: granite

Ordovician - Cambrian unnamed volcanic rocks (Ordovician - Cambrian) at surface, covers < 0.1 % of this area

Ordovician - Cambrian unnamed volcanic rocks

Lithology: mafic volcanic rock; felsic volcanic rock

Rye Complex, Breakfast Hill Granite of Novotny (1964). (Ordovician? - Late Proterozoic? ) at surface, covers 0.1 % of this area

Breakfast Hill Granite of Novotny (1964) - Blastomylonitic quartz-feldspar granitic gneiss and pegmatite intruded the Rye Complex and formed a migmatite.

Lithology: granitic gneiss; pegmatite; migmatite

Ammonoosuc Volcanics, White quartz-kyanite rock and silicate iron-formation (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Ammonoosuc Volcanics, White quartz-kyanite rock and silicate iron-formation.

Lithology: schist; iron formation

Biotite granite (Middle Ordovician) at surface, covers < 0.1 % of this area

Biotite granite - Contains minor muscovite. Makes up Cambridge Black pluton.

Lithology: granite

Ironbound Mountain Formation, Metarhyolite and microgranite intrusions (Lower Devonian) at surface, covers < 0.1 % of this area

Ironbound Mountain Formation, Metarhyolite and microgranite intrusions.

Lithology: meta-rhyolite; granite

Winnipesaukee Tonalite (Early Devonian) at surface, covers 3 % of this area

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

Lithology: tonalite; quartz diorite; granodiorite; granite

Quartz syenite (Jurassic) at surface, covers < 0.1 % of this area

Quartz syenite - Commonly porphyritic and mesoperthitic; contains biotite and, locally, fayalite, hastingsite, hornblende, or ferrohedenbergite.

Lithology: quartz syenite

Two-mica granite of the Sebago batholith and Effingham pluton of eastern New Hampshire (Mississippian - Pennsylvanian) at surface, covers 2 % of this area

Two-mica granite of the Sebago batholith and Effingham pluton of eastern New Hampshire.

Lithology: granite

Hornblende gabbro (Late Ordovician) at surface, covers < 0.1 % of this area

Hornblende gabbro.

Lithology: gabbro

Undifferentiated Granitic Rocks (Ordovician) at surface, covers < 0.1 % of this area

Undifferentiated granitic rocks.

Lithology: granite

Fitch Formation (Upper Silurian; Pridolian and Ludlovian) (Upper Silurian - (Pridolian and Ludlovian)) at surface, covers 0.2 % 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

Littleton Formation, Metaconglomerate and quartzite (Lower Devonian) at surface, covers < 0.1 % of this area

Littleton Formation, Metaconglomerate and quartzite - Locally fossiliferous in Whitefield quadrangle.

Lithology: meta-conglomerate; quartzite

Two-mica granite (Devonian - Mississippian) at surface, covers 0.9 % of this area

Two-mica granite - Found in northern New Hampshire.

Lithology: granite

Frontenac Formation, Proximal bimodal volcanic facies (Silurian?) at surface, covers 0.3 % of this area

Frontenac Formation, Proximal bimodal volcanic facies.

Lithology: metavolcanic rock

Ironbound Mountain Formation, Euxinic metashale member (Lower Devonian) at surface, covers < 0.1 % of this area

Ironbound Mountain Formation, Euxinic metashale member.

Lithology: metasedimentary rock

Oakdale Formation (Silurian) at surface, covers < 0.1 % of this area

Oakdale Formation - Metamorphosed thin-bedded, pelitic and calcareous siltstone and muscovite schist, probably low-grade equivalent of Paxton Formation. The Oakdale Formation is here revised to include strata previously mapped in CT and adjacent MA as the Hebron Formation and the Scotland Schist. The Scotland Member (Pease, 1980) is renamed the Scotland Schist Member of the Oakdale. The Oakdale is a homogeneous, calcareous metasiltstone at the base of a thick stratigraphic sequence in a geosyncline terrane and extends from NH to the Honey Hill fault in eastern CT. In central eastern CT it underlies the Hebron Formation; in northeast CT and adjacent MA it underlies conformably the Dudley Formation of the Paxton Group; in central MA it underlies the Paxton Group undivided. The lower part of the Oakdale is cut out along the Clinton-Newbury fault zone. Thickness in type area is about 1500 m. Correlative with the Gove Member of the Berwick Formation in NH and the Gonic Formation in ME. Age is Late Proterozoic(?) based on intrusion of 440 Ma Hedgehog Hill gneiss in the upper part of the Brimfield Group at the top of the stratigraphic sequence, and an age of 1188 Ma for detrital zircons from the Paxton in north-central MA (Pease, 1989).

Lithology: metasedimentary rock; mica schist

Ayer Granodiorite (Early Silurian) at surface, covers < 0.1 % of this area

Ayer Granodiorite - Gneissic granite to tonalite, locally coarsely porphyritic and muscovitic, southeastern New Hampshire.

Lithology: granodiorite; granite; tonalite

Newburyport Complex (Silurian) at surface, covers < 0.1 % of this area

Newburyport Complex - Gray, medium-grained porphyritic granite with microcline phenocrysts; intrudes SOk. Newburyport Complex was divided into two facies, tonalitic granodiorite and granite, by Shride (1971). Tonalitic facies was originally termed Newburyport Quartz Diorite and included dioritic rocks north of Clinton-Newbury fault zone that are now called Sharpners Pond Diorite in Nashoba zone, and Topsfield Granodiorite in Milford-Dedham zone. These correlations are no longer tenable due to differences in age and composition. Therefore, Newburyport Complex is restricted to the two facies present in Newburyport area. Rocks formerly mapped as Newburyport Quartz Diorite and Salem Gabbro-Diorite, except for gabbros at Salem Neck, MA, are included in undifferentiated diorite and gabbro unit (Zdigb) on MA State Geologic Map (Zen and others, 1983), largely because they could not be mapped separately at 1:250,000 scale. Unit Zdigb also includes mafic dikes and sills that are probably younger or contemporaneous. Most of the dioritic rocks northeast of Boston previously assigned to Newburyport Quartz Diorite are now assigned to an undifferentiated diorite unit (Zdi) on MA State Geologic Map. Newburyport Complex forms a large mass near Newburyport and a small one to its west, both truncated by Clinton-Newbury fault. Tonalite and granodiorite facies occupies core of Newburyport Complex at Newburyport and is intruded to the north by granite facies; described as medium to dark gray in fresh rock, weathering to both green and red, fine to medium grained, and highly variable in mineralogy. A U-Pb zircon age of 455 +/-15 Ma was determined by Zartman and Naylor (1984) for the tonalite. Granite facies intrudes both the Kittery Formation and the tonalite and granodiorite facies and covers an area of about 45 sq km. Described as light gray to dark gray, buff weathering, and porphyritic. No radiometric ages available for granite facies, but it is conceivable that the two facies are different in age. [Papers presented as chapters in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to MA State bedrock geologic map of Zen and others (1983) at scale of 1:250,000.] (Wones and Goldsmith, 1991).

Lithology: granite

Rhyolite and fine-grained granite (Cretaceous) at surface, covers 0.2 % of this area

Rhyolite and fine-grained granite - 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.

Lithology: rhyolite; granite; ignimbrite; porphyry

Smalls Falls Formation, Felsic metavolcanic member (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers < 0.1 % of this area

Smalls Falls Formation, Felsic metavolcanic member.

Lithology: felsic metavolcanic rock

Dead River Formation, undivided (Upper Cambrian? - Lower Ordovician?) at surface, covers 2 % of this area

Dead River Formation, undivided - Thinly laminated, "pin-striped" gray, green, or tan metapelite and quartzite.

Lithology: meta-argillite; quartzite

Silurian - Ordovician Frontenac Formation (Silurian - Ordovician) at surface, covers < 0.1 % of this area

Silurian - Ordovician Frontenac Formation

Lithology: graywacke; slate

Silurian granite (Silurian) at surface, covers < 0.1 % of this area

Silurian granite

Lithology: granite

Porphyritic syenite (Jurassic) at surface, covers 0.1 % of this area

Porphyritic syenite - Hastingsite or hornblende and (or) hedenbergite are present.

Lithology: syenite

Rangeley Formation, Ribbon-banded calc-silicate of eastern New Hampshire (Lower Silurian (Llandoverian)) at surface, covers 0.2 % of this area

Rangeley Formation, Ribbon-banded calc-silicate of eastern New Hampshire - Probably equivalent to Patch Mountain Member of the Sangerville Formation (Llandoverian and Wenlockian) of central Maine.

Lithology: calc-silicate rock

Augite-hornblende-biotite gabbro (Cretaceous) at surface, covers < 0.1 % of this area

Augite-hornblende-biotite gabbro - Fine- to coarse-grained.

Lithology: gabbro

Perry Mountain Formation, Volcanic facies in Piermont allochthon (Lower? - Middle? Silurian) at surface, covers < 0.1 % of this area

Perry Mountain Formation, Volcanic facies in Piermont allochthon.

Lithology: felsic volcanic rock; mafic volcanic rock

Ammonoosuc Volcanics, Metasedimentary rocks (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Ammonoosuc Volcanics, Metasedimentary rocks.

Lithology: metasedimentary rock

Porphyritic biotite granodiorite (Early - Late Devonian) at surface, covers < 0.1 % of this area

Porphyritic biotite granodiorite - Found in Mt. Cube quadrangle.

Lithology: granodiorite

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

Devonian - Silurian Towow Formation

Lithology: mudstone

Hurricane Mountain Formation (Upper Cambrian?) at surface, covers < 0.1 % of this area

Hurricane Mountain Formation - Rusty-weathered, dark siliceous scaly slate or schist of flaser structure, polymictic fragments from a few mm to (in Maine) several hundred meters. A melange consisting of metasedimentary, felsic/mafic metavolcanics, and ultramafic rocks..

Lithology: slate; schist; metasedimentary rock; metavolcanic rock; ultramafic intrusive rock

Pink equigranular biotite granite (Late Devonian) at surface, covers 0.3 % of this area

Pink equigranular biotite granite - Found in Woodsville and Whitefield quadrangles and in small intrusive units in northern and southeastern New Hampshire.

Lithology: granite

Trondhjemite and abundant pegmatite (Devonian - Mississippian) at surface, covers 0.1 % of this area

Trondhjemite and abundant pegmatite - Gray and fine-grained; possibly belonging to the Sebago batholith.

Lithology: trondhjemite; pegmatite

Smalls Falls Formation, Metaconglomerate member (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers < 0.1 % of this area

Smalls Falls Formation, Metaconglomerate member - Found in Errol quadrangle in northern New Hampshire.

Lithology: meta-conglomerate

Granite, granodiorite, and tonalite (Late Ordovician) at surface, covers 1 % of this area

Granite, granodiorite, and tonalite.

Lithology: granite; granodiorite; tonalite

Gile Mountain Formation (Devonian) at surface, covers < 0.1 % of this area

Gile Mountain Formation - Gray quartz-muscovite phyllite or schist, interbedded and intergradational with gray micaceous quartzite (graywacke northeast of Nulhegan River), calcareous mica schist, and, locally, quartzose and micaceous crystalline limestone like that of the Waits River formation. The phyllite and schist commonly contain porphyroblasts of biotite, garnet, or staurolite, and locally kyanite, andalusite, or sillimanite. Used as Early Devonian Gile Mountain Formation. Generally consists of gray to tan metawacke and schist or phyllite, gradational into its Meetinghouse Slate Member, but much more thickly bedded and less pelitic. Contains minor metavolcanic lentils. Unnamed metavolcanic member is possibly equivalent to Putney Volcanics of southeastern VT. Separately mapped interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone, and minor marble and quartzite, resembles Waits River Formation of VT. Meetinghouse Slate Member consists of gray to black phyllite and silty metasandstone turbidite. Report includes geologic map, cross sections, correlation chart, and four 1:500,000-scale derivative maps (Lyons and others, 1997).

Lithology: phyllite; mica schist; quartzite; limestone; graywacke

Orfordville Formation (Ordovician) at surface, covers < 0.1 % of this area

Orfordville Formation - Carbonaceous phyllite; minor quartzite.

Lithology: phyllite; quartzite

Madrid and Smalls Falls Formations, undivided (Silurian) at surface, covers 0.4 % of this area

Madrid and Smalls Falls Formations, undivided.

Lithology: granofels; schist; calc-silicate schist; pelitic schist

Hornblende-biotite quartz monzodiorite (Jurassic) at surface, covers < 0.1 % of this area

Hornblende-biotite quartz monzodiorite - Composition ranges from quartz monzonite to diorite.

Lithology: quartz monzodiorite; quartz monzonite; diorite

Spaulding Tonalite (Early Devonian) at surface, covers 3 % 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

Porphyritic hornblende diorite (Jurassic) at surface, covers < 0.1 % of this area

Porphyritic hornblende diorite - Found in northwestern New Hampshire.

Lithology: diorite

Littleton Formation, Metabasaltic greenstone or amphibolite (Lower Devonian) at surface, covers < 0.1 % of this area

Littleton Formation, Metabasaltic greenstone or amphibolite.

Lithology: greenstone; amphibolite

Mesoperthitic granite (Jurassic) at surface, covers 0.2 % of this area

Mesoperthitic granite - Contains riebeckite and (or) hastingsite.

Lithology: granite

Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon (Lower?- Middle? Silurian) at surface, covers 2 % of this area

Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon.

Lithology: metasedimentary rock; felsic metavolcanic rock; mafic metavolcanic rock

Ammonoosuc Volcanics, Bimodal volcanic rocks (Middle - Upper Ordovician) at surface, covers 3 % of this area

Ammonoosuc Volcanics, Bimodal volcanic rocks - Locally includes unmapped Oals.

Lithology: bimodal suite

Metavolcanic and metasedimentary rocks of the lower part of Ammonoosuc Volcanics, undivided (Middle Ordovician) at surface, covers 0.3 % of this area

Metavolcanic and metasedimentary rocks of the lower part of Ammonoosuc Volcanics, undivided.

Lithology: metavolcanic rock; metasedimentary rock

Smalls Falls Formation, Mixed metavolcanic rocks and metavolcanic sediments (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers < 0.1 % of this area

Smalls Falls Formation, Mixed metavolcanic rocks and metavolcanic sediments.

Lithology: metavolcanic rock

Hypersthene-biotite quartz diorite and hornblende or actinolite diorite or gabbro (Early Devonian - Late Devonian) at surface, covers < 0.1 % 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

Ironbound Mountain Formation, undivided (Lower Devonian) at surface, covers 0.6 % of this area

Ironbound Mountain Formation, undivided - Interbedded gray phyllite, in places containing feldspathic clasts, and feldspathic metasandstone, variably graded.

Lithology: phyllite; metasedimentary rock

Mount Osceola Granite, Green biotite mesoperthitic granite (Early - Middle Jurassic) at surface, covers < 0.1 % of this area

Mount Osceola Granite, Green biotite mesoperthitic granite.

Lithology: granite

Frontenac Formation, undivided (Silurian?) at surface, covers 3 % of this area

Frontenac Formation, undivided - Interbedded thick feldspathic wackes, tan and green slates, and minor calcareous lenses.

Lithology: metasedimentary rock; slate

Gile Mountain Formation, Hall Stream Member (Devonian) at surface, covers < 0.1 % of this area

Gile Mountain Formation, Hall Stream Member - Highly feldspathic grit, probably volcanic; feldspathic chlorite-ankerite schist and amphibolite; all northeast of Nulhegan River.

Lithology: schist; amphibolite

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

Bethlehem Gneiss - Two-mica granodiorite gneiss. Revised as the Bethlehem Granodiorite to emphasize its average granodiorite composition. Mapped as the Haverhill, Mount Clough, Indian Pond, and Fairlee plutons. Consists of strongly metamorphosed, foliated, gray, medium-grained biotite granodiorite and local tonalite and granite. Age is Devonian based on isotopic age of 410+/-5 Ma (J.N. Aleinikoff, this report, from Fairlee pluton), which is also consistent with age of 409+/-5 Ma reported by Kohn and others (1992) from Indian Pond pluton and Bellows Falls pluton (the latter is outside of map area in southwestern NH) (Moench and others, 1995).

Lithology: granitic gneiss

Biotite granite stock and dikes (Early - Late Silurian) at surface, covers 0.1 % of this area

Biotite granite stock and dikes - Northernmost New Hampshire.

Lithology: granite

Biotite tonalite (Early - Late Devonian) at surface, covers 0.2 % of this area

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

Lithology: tonalite

Augite-hornblende diorite and gabbro (Cretaceous ) at surface, covers < 0.1 % of this area

Augite-hornblende diorite and gabbro - Gray to black, coarse-grained, porphyritic. Found in Mt. Pawtuckaway quadrangle.

Lithology: diorite; gabbro

Littleton Formation, undivided (Lower Devonian; Siegenian) at surface, covers 4 % 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

Massabesic Gneiss Complex (Late Proterozoic) at surface, covers 2 % 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

Frontenac Formation, Metabasalt interbeds (Silurian?) at surface, covers 0.5 % of this area

Metabasalt interbeds.

Lithology: meta-basalt

Devonian quartz monzodiorite - quartz diorite (pyroxene plus hornblende accessory mineral) (Devonian) at surface, covers < 0.1 % of this area

Devonian quartz monzodiorite - quartz diorite (pyroxene plus hornblende accessory mineral) - Devonian pyroxene-hornblende quartz monzodiorite and quartz diorite - pyroxene-hornblende-biotite quartz monzodiorite, and pyroxene-hornblende-biotite quartz diorite

Lithology: quartz monzodiorite; quartz diorite

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

Silurian - Precambrian Z Eliot Formation

Lithology: phyllite; quartzite; schist; calc-silicate rock

Ammonoosuc Volcanics, Metabasalt (Middle - Upper Ordovician) at surface, covers 0.6 % of this area

Ammonoosuc Volcanics, Metabasalt.

Lithology: meta-basalt

Frontenac Formation, Mixed volcanic and sedimentary facies (Silurian?) at surface, covers 0.1 % of this area

Frontenac Formation, Mixed volcanic and sedimentary facies.

Lithology: metavolcanic rock; metasedimentary rock

Albee Formation (Ordovician) at surface, covers < 0.1 % of this area

Albee Formation - Massive, gray, white-weathered quartzite and feldspathic quartzite interbedded with greenish-gray slate, phyllite, feldspthic phyllite and quartzose argillaceous phyllite. Micaceous quartzite, quartz-mica schist, mica schist and hornfels contining porphyroblasts of biotite, garnet, staurolite and sillimanite in the vicinity of granitic plutons. Soda-rhyolite tuff occurs locally. Micaceous quartzite characterized by thin, schistose "pinstripe" partings is common in many areas.

Lithology: quartzite; slate; phyllite; mica schist; hornfels; tuff

Granodiorite to tonalite (Late Ordovician) at surface, covers 0.8 % of this area

Granodiorite to tonalite.

Lithology: granodiorite; tonalite

Hornblende (or alkalic amphibole) syenite (Jurassic) at surface, covers 0.4 % of this area

Hornblende (or alkalic amphibole) syenite.

Lithology: syenite

Nepheline-sodalite-hastingsite syenite (Jurassic) at surface, covers < 0.1 % of this area

Nepheline-sodalite-hastingsite syenite - Found at Red Hill in Mt. Chocorua quadrangle (see index accompanying "Sources of Map Data").

Lithology: syenite

Smalls Falls Formation, undivided (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers 2 % 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

Rangeley Formation, Pink to green calc-silicate and purple biotite granofels (Lower Silurian (Llandoverian)) at surface, covers < 0.1 % of this area

Rangeley Formation, Pink to green calc-silicate and purple biotite granofels - Thinly bedded. Close to transition from lower to upper parts of the Rangeley Formation. Probably equivalent to part of Paxton Formation of Zen and others (1983) in Massachusetts.

Lithology: calc-silicate rock; granofels

Medium-grained mesoperthitic granite containing riebeckite and (or) hastingsite (Cretaceous) at surface, covers < 0.1 % of this area

Medium-grained mesoperthitic granite containing riebeckite and (or) hastingsite.

Lithology: granite

Metamorphosed gabbro, diorite, and intrusive basalt dikes (Devonian? - Silurian?) at surface, covers < 0.1 % of this area

Metamorphosed gabbro, diorite, and intrusive basalt dikes - Chiefly in northern New Hampshire.

Lithology: metavolcanic rock

Ammonoosuc Volcanics, Metasedimentary rocks (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Ammonoosuc Volcanics, Metasedimentary rocks - Contains mafic metavolcanic lenses.

Lithology: metasedimentary rock; mafic metavolcanic rock

Rangeley Formation, undivided (Lower Silurian (Llandoverian)) at surface, covers 2 % of this area

Rangeley Formation, undivided.

Lithology: metasedimentary rock; calc-silicate rock; meta-argillite; quartzite; pelitic schist; granofels; felsic metavolcanic rock

Hornblende or alkalic amphibole quartz syenite (Jurassic) at surface, covers 0.2 % of this area

Hornblende or alkalic amphibole quartz syenite.

Lithology: quartz syenite

Leucocratic granite to quartz syenite (Jurassic) at surface, covers < 0.1 % of this area

Leucocratic granite to quartz syenite.

Lithology: granite; quartz syenite

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

Berwick Formation - Thin- to thick-bedded metamorphosed calcareous sandstone, siltstone, and minor muscovite schist. In New Hampshire: Used as Berwick Formation of Merrimack Group. Consists of purple biotite-feldspar granofels or schist. Contains interbeds of calcsilicate granofels and minor metapelites. Includes Gove Member, mapped separately. Stratigraphic sequence with respect to Eliot Formation is uncertain. Age of all formations in Merrimack Group changed to Ordovician(?) to Silurian(?) based on isotopic age determinations of approx 440 and 420 Ma from detrital zircons from Berwick by J.N. Aleinikoff (oral commun., 1994) (Lyons and others, 1997).

Lithology: metasedimentary rock; mica schist

Partridge Formation, Interstratified metavolcanic rocks (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Partridge Formation, Interstratified metavolcanic rocks - Chiefly amphibolites, found in southwestern New Hampshire.

Lithology: amphibolite; metavolcanic rock

Hornblende-biotite granite (Late Ordovician) at surface, covers 0.3 % of this area

Hornblende-biotite granite.

Lithology: granite

Chelmsford Granite (Lower Devonian) at surface, covers < 0.1 % of this area

Chelmsford Granite - Light-gray, even and medium-grained, muscovite-bearing granite; locally foliated; intrudes Sb.

Lithology: granite

Ordovician unnamed volcanic and sedimentary rocks (Ordovician) at surface, covers < 0.1 % of this area

Ordovician unnamed volcanic and sedimentary rocks

Lithology: mafic volcanic rock; felsic volcanic rock; sedimentary rock

Biotite Quartz Diorite Gneiss (Devonian) at surface, covers < 0.1 % of this area

Biotite quartz diorite gneiss.

Lithology: granitic gneiss

Biotite granite (Late Ordovician) at surface, covers 2 % of this area

Biotite granite - Pink, moderately to weakly foliated.

Lithology: granite

Migmatitic rocks (Devonian - Silurian) at surface, covers 0.5 % of this area

Migmatitic rocks - Formations unidentifiable owing to obliteration of original sedimentary or volcanic characteristics by anatexis or by numerous intrusions.

Lithology: migmatite

Rye Complex (Ordovician? - Late Proterozoic?) at surface, covers 0.3 % of this area

Rye Complex - Migmatite of gray, foliated, sheared or mylonitized two-mica granite and pegmatite, minor hornblende-biotite diorite, intruding metapelites and metavolcanic rocks in southeastern New Hampshire.

Lithology: migmatite; granite; pegmatite; diorite; meta-argillite; metavolcanic rock

Gray biotite granite (Permian) at surface, covers 0.5 % of this area

Gray biotite granite - Contains minor muscovite. Found in Milford quadrangle.

Lithology: granite

Hastingsite granite (Jurassic) at surface, covers < 0.1 % of this area

Hastingsite granite - Leucocratic, pink or light-brown, and mesoperthitic.

Lithology: granite

Two-mica granite of northern and southeastern New Hampshire (Early - Late Devonian) at surface, covers 1.0 % of this area

Two-mica granite of northern and southeastern New Hampshire - Similar to Concord Granite.

Lithology: granite

Diorite and tonalite (Devonian and Silurian) at surface, covers < 0.1 % of this area

Diorite and tonalite - Includes Dracut Diorite, tonalite near the Ayer Granite, and equivalents of the Exeter Diorite of New Hampshire; intrudes Sb.

Lithology: diorite; tonalite

Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire (Lower Silurian (Llandoverian)) at surface, covers 0.1 % of this area

Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire - Quartz-pebble conglomerate overlain by rusty metapelite and feldspathic quartzite.

Lithology: conglomerate; meta-argillite; quartzite

Hornblende-biotite tonalite (Middle Ordovician) at surface, covers < 0.1 % of this area

Hornblende-biotite tonalite.

Lithology: tonalite

Gabbro (Jurassic) at surface, covers < 0.1 % of this area

Gabbro - Has varying amounts of olivine, augite, and hornblende.

Lithology: gabbro

Biotite granodiorite (Late Ordovician) at surface, covers 0.4 % of this area

Biotite granodiorite.

Lithology: granodiorite

Ammonoosuc Volcanics, Felsic metavolcanic rocks (Middle - Upper Ordovician) at surface, covers 0.2 % of this area

Ammonoosuc Volcanics, Felsic metavolcanic rocks.

Lithology: felsic metavolcanic rock

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

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

Lithology: tonalite

Hornblende granite to granodiorite (Late Ordovician) at surface, covers 0.1 % of this area

Hornblende granite to granodiorite - Part of Lost Nation pluton of northwestern New Hampshire.

Lithology: granite; granodiorite

Perry Mountain and Rangeley Formations, undivided (Silurian) at surface, covers 0.5 % of this area

Perry Mountain and Rangeley Formations, undivided.

Lithology: quartzite; calc-silicate rock; felsic metavolcanic rock; meta-argillite; granofels; metasedimentary rock; conglomerate; pelitic schist

Jurassic granite (Jurassic) at surface, covers < 0.1 % of this area

Jurassic granite - Jurassic biotite granite undivided

Lithology: granite

Ordovician - Cambrian Aziscohos Formation (Ordovician - Cambrian) at surface, covers < 0.1 % of this area

Ordovician - Cambrian Aziscohos Formation

Lithology: shale; quartzite; siltstone

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

Silurian - Precambrian Z Berwick Formation

Lithology: gneiss; quartzite; schist; slate

Jim Pond Formation (Upper Cambrian) at surface, covers < 0.1 % of this area

Jim Pond Formation - Pillow metabasalt member. Lenses within the Hurricane Mountain Formation of northern New Hampshire interpreted as tectonic rafts of Jim Pond Formation.

Lithology: meta-basalt

Quimby Formation (Upper Ordovician?) at surface, covers < 0.1 % of this area

Quimby Formation - Black graphitic-sulfidic rusty-weathering schist and thickly bedded metagraywacke.

Lithology: schist; metasedimentary rock

Littleton Formation, Upper unnamed member (Lower Devonian) at surface, covers 1 % 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 4 % 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

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

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

Lithology: phyllite; quartzite; mica schist; calc-silicate rock

Devonian - Silurian undifferentiated sedimentary rocks in areas of extreme migmatization (Devonian - Silurian) at surface, covers < 0.1 % of this area

Devonian - Silurian undifferentiated sedimentary rocks in areas of extreme migmatization

Lithology: migmatite

Porphyritic biotite granite (Cretaceous) at surface, covers < 0.1 % of this area

Porphyritic biotite granite - Pink to gray; hastingsite or riebeckite in some varieties.

Lithology: granite

Devonian granite (Devonian) at surface, covers < 0.1 % of this area

Devonian granite

Lithology: granite

Moat Volcanics (Middle Jurassic?) at surface, covers 0.2 % of this area

Moat Volcanics - Bedded and ignimbritic tuffs, flows, and breccias; also porphyritic rhyolite and minor trachyte.

Lithology: ignimbrite; ash-flow tuff; volcanic breccia (agglomerate); rhyolite; trachyte

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

Hornblende diorite - Coarse-grained to porphyritic.

Lithology: diorite

Ayer Granite (Lower Silurian) at surface, covers < 0.1 % of this area

Ayer Granite - Granite to tonalite, partly porphyritic; locally gneissic, locally muscovitic; may include rocks older than Silurian; intrudes Sb and So. Ayer Granite is divided into the Clinton facies and the Devens-Long Pond facies (Gore, 1976). In addition, there are some masses not assigned to either facies that intrude Berwick Formation west and northwest of Lawrence, and that intrude Paxton and Oakdale Formations south of Worcester and west of probable southern continuation of Wekepeke fault. Radiometric ages obtained for facies of Ayer pose problems in assigning ages to unfossiliferous sedimentary rocks they intrude. Clinton facies has a well-defined U-Pb zircon age of 433 +/-5 Ma (Zartman and Naylor, 1984) that authors cite as Early Silurian; Devens-Long Pond facies has a similar age. This age greatly compresses the time available for deposition, burial, deformation, and metamorphism of Berwick and Paxton if these units are truly Silurian. Some of the Ayer not assigned to a facies may have been more properly correlated with Early Devonian Chelmsford Granite and muscovite-biotite granite at Millstone Hill. Bodies south of Worcester may be more properly correlated with Canterbury Gneiss of CT, which lies on strike with Ayer and has Early Devonian age of 329 +/-9 Ma (Zartman and Naylor, 1984). Zartman and Naylor (1984) believe Ayer Granite has same age range as Newburyport Complex. It is quite possible, based on textural and mineralogical differences that the two facies should be separate units, representing different magmatic events (Wones and Goldsmith, 1991).

Lithology: granite; tonalite

Devonian granite (muscovite accessory mineral) (Devonian) at surface, covers < 0.1 % of this area

Devonian granite (muscovite accessory mineral); muscovite-biotite granite

Lithology: granite

Littleton Formation, Calc-silicate rock (Lower Devonian) at surface, covers < 0.1 % of this area

Littleton Formation, Calc-silicate rock - Possibly equivalent in part to Hildreths Formation of Maine but not restricted to one horizon. Locally fossiliferous, as in Moosilauke quadrangle.

Lithology: calc-silicate rock

Partridge Formation, undivided (Middle - Upper Ordovician) at surface, covers 2 % of this area

Partridge Formation, undivided - Black, rusty-weathering sulfidic-graphitic slate or schist and sparse to abundant metagraywacke. Lies stratigraphically between upper and lower parts of the Ammonoosuc Volcanics.

Lithology: slate; schist; metasedimentary rock

Ordovician - Cambrian Dead River formation (Ordovician - Cambrian) at surface, covers < 0.1 % of this area

Ordovician - Cambrian Dead River formation

Lithology: slate; quartzite; phyllite

Syenite (Permian-Triassic) at surface, covers < 0.1 % of this area

Syenite - Hornblende, biotite, quartz and augite syenites.

Lithology: syenite; quartz syenite

Fitch and Clough Formations, undivided (Silurian) at surface, covers 0.3 % of this area

Fitch and Clough Formations, undivided.

Lithology: quartzite; marble; meta-conglomerate; sandstone; mica schist; siltstone; pelitic schist; marble

Ironbound Mountain Formation, Basaltic to andesitic member (Lower Devonian) at surface, covers < 0.1 % of this area

Ironbound Mountain Formation, Basaltic to andesitic member.

Lithology: basalt; andesite

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

Basalt - Black, chiefly massive to porphyritic. Includes minor rhyolitic ignimbrite and andesitic tuff. Part of Ossipee Mountain Complex of Kingsley (1931)

Lithology: basalt; ignimbrite; tuff

Metadiorite (Devonian) at surface, covers < 0.1 % of this area

Metadiorite - Dikes and sills of metagabbro, metadiabase and meta-andesite too small to show are chiefly in the Missisquoi, Albee, and Orfodville formations.

Lithology: metavolcanic rock

Porphyritic granite (Jurassic) at surface, covers < 0.1 % of this area

Porphyritic granite.

Lithology: granite

Aziscohos Formation, Lower unnamed member (Upper Cambrian? - Lower Ordovician?) at surface, covers 0.2 % of this area

Aziscohos Formation, Lower unnamed member - Rusty, dark metapelite containing thin coticule laminations, feldspathic metatuff, and vein quartz lenses.

Lithology: meta-argillite; metavolcanic rock

Porphyritic phase of hornblende-biotite tonalite (Middle Ordovician) at surface, covers < 0.1 % of this area

Porphyritic phase of hornblende-biotite tonalite.

Lithology: tonalite

Clough Quartzite (Lower Silurian (upper Llandoverian)) at surface, covers 0.3 % of this area

Clough Quartzite - Orthoquartzite, quartz metaconglomerate, muscovite schist, minor polymictic metaconglomerate. Disconformable below Fitch Formation and unconformable on Ordovician formations. Equivalent, in part, to member C of Rangeley Formation of Maine. Fossiliferous.

Lithology: quartzite; meta-conglomerate; mica schist

Newburyport Complex (Late Silurian) at surface, covers < 0.1 % of this area

Newburyport Complex - Medium-grained porphyritic granite.

Lithology: granite

Newburyport Complex (Silurian or Ordovician) at surface, covers < 0.1 % of this area

Newburyport Complex - Gray, medium-grained tonalite and granodiorite. Newburyport Complex was divided into two facies, tonalitic granodiorite and granite, by Shride (1971). Tonalitic facies was originally termed Newburyport Quartz Diorite and included dioritic rocks north of Clinton-Newbury fault zone that are now called Sharpners Pond Diorite in Nashoba zone, and Topsfield Granodiorite in Milford-Dedham zone. These correlations are no longer tenable due to differences in age and composition. Therefore, Newburyport Complex is restricted to the two facies present in Newburyport area. Rocks formerly mapped as Newburyport Quartz Diorite and Salem Gabbro-Diorite, except for gabbros at Salem Neck, MA, are included in undifferentiated diorite and gabbro unit (Zdigb) on MA State Geologic Map (Zen and others, 1983), largely because they could not be mapped separately at 1:250,000 scale. Unit Zdigb also includes mafic dikes and sills that are probably younger or contemporaneous. Most of the dioritic rocks northeast of Boston previously assigned to Newburyport Quartz Diorite are now assigned to an undifferentiated diorite unit (Zdi) on MA State Geologic Map. Newburyport Complex forms a large mass near Newburyport and a small one to its west, both truncated by Clinton-Newbury fault. Tonalite and granodiorite facies occupies core of Newburyport Complex at Newburyport and is intruded to the north by granite facies; described as medium to dark gray in fresh rock, weathering to both green and red, fine to medium grained, and highly variable in mineralogy. A U-Pb zircon age of 455 +/-15 Ma was determined by Zartman and Naylor (1984) for the tonalite. Granite facies intrudes both the Kittery Formation and the tonalite and granodiorite facies and covers an area of about 45 sq km. Described as light gray to dark gray, buff weathering, and porphyritic. No radiometric ages available for granite facies, but it is conceivable that the two facies are different in age. [Papers presented as chapters in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to MA State bedrock geologic map of Zen and others (1983) at scale of 1:250,000.] (Wones and Goldsmith, 1991).

Lithology: tonalite; granodiorite

Paxton Formation (Silurian) at surface, covers < 0.1 % of this area

Paxton Formation - Undifferentiated biotite granofels, calc-silicate granofels, and sulfidic schist. The Paxton, here of group rank, includes strata formerly mapped in CT as the Hebron Formation and in MA as the Paxton Formation. It conformably overlies the Oakdale Formation and structurally and conformably underlies the Brimfield Group. It is undivided in central MA; in northeast CT and adjacent MA it is divided into the Dudley and Southbridge Formations. Age is Late Proterozoic(?) based on the intrusion of 440 m.y. Hedgehog Hill gneiss into the overlying Brimfield Group and an age of 1188 m.y. for detrital zircons from the Paxton (Pease, 1989).

Lithology: granofels; schist

Gile Mountain Formation, Meetinghouse Slate Member (Lower Devonian ) at surface, covers < 0.1 % of this area

Meetinghouse Slate Member - Gray to black phyllite and silty metasandstone turbidite.

Lithology: phyllite; metasedimentary rock

Gray augite-hornblende-biotite monzonite (Cretaceous) at surface, covers < 0.1 % of this area

Gray augite-hornblende-biotite monzonite.

Lithology: monzonite

Biotite quartz diorite in northeastern New Hampshire (Early - Late Devonian) at surface, covers 0.2 % of this area

Biotite quartz diorite in northeastern New Hampshire

Lithology: quartz diorite

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

Berwick Formation - Mica schist. In New Hampshire: Used as Berwick Formation of Merrimack Group. Consists of purple biotite-feldspar granofels or schist. Contains interbeds of calcsilicate granofels and minor metapelites. Includes Gove Member, mapped separately. Stratigraphic sequence with respect to Eliot Formation is uncertain. Age of all formations in Merrimack Group changed to Ordovician(?) to Silurian(?) based on isotopic age determinations of approx 440 and 420 Ma from detrital zircons from Berwick by J.N. Aleinikoff (oral commun., 1994) (Lyons and others, 1997).

Lithology: mica schist

Cambrian Jim Pond Formation graywacke (Cambrian) at surface, covers < 0.1 % of this area

Cambrian Jim Pond Formation graywacke

Lithology: graywacke

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

Eliot Formation - Phyllite and calcareous phyllite. In New Hampshire: Used as Eliot Formation of Merrimack Group. Consists of gray to green phyllite, calcareous quartzite, quartz-mica schist, and well-bedded calc-silicate. Includes Calef Member, mapped separately. Age of all formations in Merrimack Group changed to Ordovician(?) to Silurian(?) based on isotopic age determinations of approx 440 and 420 Ma from detrital zircons from Berwick Formation (of Merrimack Group) by J.N. Aleinikoff (oral commun., 1994) (Lyons and others, 1997).

Lithology: phyllite

Gile Mountain Formation, Interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone (Lower Devonian) at surface, covers < 0.1 % of this area

Interbedded gray slate or phyllite and brown-weathering calcite-ankerite metasiltstone - Contains minor marble and quartzite. Resembles Waits River Formation in Vermont.

Lithology: slate; phyllite; metasedimentary rock; marble; quartzite

Biotite trondhjemite in Rumney quadrangle (Early - Late Devonian) at surface, covers < 0.1 % of this area

Biotite trondhjemite in Rumney quadrangle.

Lithology: trondhjemite

Undifferentiated Granitic Gneiss (Devonian) at surface, covers < 0.1 % of this area

Undifferentiated Granitic Gneiss - Small dikes and sills do not show.

Lithology: granitic gneiss

Smalls Falls Formation, Metabasalt member (Upper to Middle Silurian (Ludlovian and Wenlockian)) at surface, covers 0.2 % of this area

Smalls Falls Formation, Metabasalt member.

Lithology: meta-basalt

Porphyritic biotite granodiorite in northern Jefferson dome in Milan quadrangle (Late Ordovician ) at surface, covers 0.1 % of this area

Porphyritic biotite granodiorite in northern Jefferson dome in Milan quadrangle.

Lithology: granodiorite

Clough Formation (Silurian) at surface, covers < 0.1 % of this area

Clough Formation - Quartzite, quartz-conglomerate, and mica schist; lenses of fossiliferous calcareous quartzite in upper part. (Southeastern Vermont).

Lithology: conglomerate; quartzite; mica schist

Orfordville Formation, Post Pond Volcanics (Ordovician) at surface, covers < 0.1 % of this area

Orfordville Formation, Post Pond Volcanics - Greenstone, green chloritic schist interbedded with schistose felsite, quartz-feldspar-sericite schist; fine-grained chloritic, biotitic gneiss, all west of Ammonoosuc fault; mainly amphibolite east of the Ammonoosuc fault.

Lithology: greenstone; greenschist; mica schist; biotite gneiss; amphibolite

Fitch Formation (Silurian) at surface, covers < 0.1 % of this area

Fitch Formation - Quartz-plagioclase-biotite granulite; actinolite-diopside granulite; impure limestone and dolomite; mica schist; the carbonate-rich beds are typically an inch or two thick and segmented so as to give the weathered outcrop a characteristic pitted appearance. (Southeastern Vermont).

Lithology: granulite; limestone; dolostone (dolomite); mica schist

Greenvale Cove Formation (Lower Silurian? ) at surface, covers < 0.1 % of this area

Greenvale Cove Formation - Grayish-violet interlaminated metashale, feldspathic metasandstone, and calc-silicate rock of the Piermont allochthon in western New Hampshire.

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

Gile Mountain Formation, Mafic metavolcanic member (Lower Devonian ) at surface, covers < 0.1 % of this area

Mafic metavolcanic member - Possibly equivalent to Putney Volcanics of southeastern Vermont.

Lithology: mafic metavolcanic rock

Trondhjemite (Late Ordovician) at surface, covers 0.2 % of this area

Trondhjemite - Contains biotite and hornblende.

Lithology: trondhjemite

Massive to weakly foliated, pink and gray, fine- to medium-grained biotite granite (Pennsylvanian) at surface, covers < 0.1 % of this area

Massive to weakly foliated, pink and gray, fine- to medium-grained biotite granite - In the Townsend area; commonly contains pink magnetite-bearing pegmatite identical to granite of Milford, New Hampshire; intrudes OZma and Sp.

Lithology: granite; pegmatite

Tonalite (Middle Ordovician) at surface, covers < 0.1 % of this area

Tonalite - Extended from Joslin Turn, Vermont.

Lithology: tonalite

Cambrian Hurricane Mountain Formation (Cambrian) at surface, covers < 0.1 % of this area

Cambrian Hurricane Mountain Formation

Lithology: melange

Merrimack Group, Kittery Formation (Ordovician? - Silurian?) at surface, covers 0.6 % of this area

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

Lithology: metasedimentary rock; phyllite

Biotite-hornblende granodiorite (Cretaceous) at surface, covers < 0.1 % of this area

Biotite-hornblende granodiorite.

Lithology: granodiorite

Porphyritic biotite quartz syenite in central Jefferson dome in Mt. Washington quadrangle (Late Ordovician) at surface, covers < 0.1 % of this area

Porphyritic biotite quartz syenite in central Jefferson dome in Mt. Washington quadrangle.

Lithology: quartz syenite

Ordovician - Cambrian Dead River formation lower member (Ordovician - Cambrian) at surface, covers < 0.1 % of this area

Ordovician - Cambrian Dead River formation lower member

Lithology: quartzite; phyllite

Hornblende quartz monzonite (Late Ordovician) at surface, covers 0.1 % of this area

Hornblende quartz monzonite.

Lithology: quartz monzonite

Gile Mountain Formation, Meetinghouse Slate Member (Devonian) at surface, covers < 0.1 % of this area

Gile Mountain Formation, Meetinghouse Slate Member - Chiefly gray slate or phyllite characterized by beds of gray schistose quartzite 1/8 inch to 3 inches thick. Gile Mountain Formation and its Meetinghouse Slate Member were previously considered to be Early Devonian based on Emsian plant fossils from Compton Formation of QUE (Hueber and others, 1990; Hatch, 1991). Age assignment here changed to Early Devonian(?) because recent mapping indicates that Gile Mountain and Compton are not coextensive across VT-QUE border as formerly believed by Doll and others (1961, State map) and St. Julien and Slivitsky (1987). Instead, the formations are separated by Ironbound Mountain Formation. Ironbound Mountain Formation is conformably overlain by Compton, but it is not yet known whether Ironbound Mountain is overlain or underlain by Gile Mountain; this is shown by queried Ironbound Mountain-Gile Mountain contact in area of Averill 7.5-min quad, VT. Correlation of Gile Mountain and Compton is justified only if Gile Mountain in this area conclusively is shown to be underlain by Ironbound Mountain; otherwise, Gile Mountain (with possible exception of its Meetinghouse Slate Member) would be coeval with Silurian Frontenac Formation. Hatch (1988) proposed that Meetinghouse represents upper part of Gile Mountain on basis of graded bedding seen south of map area. This relationship is not proven, however, because Gile Mountain-Meetinghouse contact is difficult to define and graded beds are not always easily interpreted. On this map, Meetinghouse is tentatively shown to occur below main body of Gile Mountain on basis of remarkable similarity between it and Ironbound Mountain Formation. This relationship easily explains highly pelitic character of the Meetinghouse with upward-coarsening character of Lower Devonian sequences elsewhere in map area. Meetinghouse Slate Member includes volcanic facies (Moench and others, 1995).

Lithology: slate; phyllite; quartzite

Large mesoperthitic phenocrysts in a pink to gray quartz syenite porphyry of "Albany type" (Cretaceous) at surface, covers 0.1 % of this area

Large mesoperthitic phenocrysts in a pink to gray quartz syenite porphyry of "Albany type" - Alkalic amphibole or fayalite may be present. Part of Ossipee Mountain Complex of Kingsley (1931).

Lithology: quartz syenite

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

Devonian - Silurian Towow Formation conglomerate

Lithology: conglomerate

Frontenac Formation, Graded-bedded metagraywacke and subordinate gray phyllite (Silurian?) at surface, covers < 0.1 % of this area

Frontenac Formation, Graded-bedded metagraywacke and subordinate gray phyllite.

Lithology: metasedimentary rock; phyllite

Devonian Ironbound Mountain Formation (Devonian) at surface, covers < 0.1 % of this area

Devonian Ironbound Mountain Formation

Lithology: slate

Carboniferous alkali feldspar granite (muscovite accessory mineral) (Carboniferous) at surface, covers < 0.1 % of this area

Carboniferous alkali feldspar granite (muscovite accessory mineral) - muscovite-biotite granite

Lithology: granite

Diorite (Jurassic) at surface, covers < 0.1 % of this area

Diorite - Contains hornblende, biotite, and hedenbergite.

Lithology: diorite

Trondhjemite and quartz diorite in northern Jefferson dome in Gorham quadrangle (Late Ordovician) at surface, covers 0.3 % of this area

Trondhjemite and quartz diorite in northern Jefferson dome in Gorham quadrangle.

Lithology: trondhjemite; quartz diorite

Ironbound Mountain Formation, Grits at Halls Stream in northern New Hampshire (Lower Devonian) at surface, covers < 0.1 % of this area

Ironbound Mountain Formation, Grits at Halls Stream in northern New Hampshire - Thickly bedded feldspathic volcaniclastic grit and interbedded gray slate. Equivalent to Grenier Ponds Member of the Ironbound Mountain Formation in western Maine.

Lithology: metavolcanic rock; slate

Frontenac Formation, Massive tan- or brown-weathering calcite-ankerite-muscovite granofels and interbedded gray metapelite (Silurian?) at surface, covers 0.2 % of this area

Frontenac Formation, Massive tan- or brown-weathering calcite-ankerite-muscovite granofels and interbedded gray metapelite - Probably partly a facies equivalent to the Waits River Formation in Vermont.

Lithology: granofels; meta-argillite

Partridge Formation (Ordovician) at surface, covers < 0.1 % of this area

Partridge Formation - Rusty weathering carbonaceous mica schist locally containing porphyroblasts of biotite, garnet, or staurolite. (Southeastern Vermont).

Lithology: mica schist

Littleton Formation, Epiclastic metavolcanic sediments (Lower Devonian) at surface, covers < 0.1 % of this area

Littleton Formation, Epiclastic metavolcanic sediments.

Lithology: metavolcanic rock

Hornblende-biotite quartz syenite to syenite (Late Ordovician) at surface, covers 0.3 % of this area

Hornblende-biotite quartz syenite to syenite.

Lithology: quartz syenite; syenite

Ironbound Mountain Formation, Felsic volcanic member (Lower Devonian) at surface, covers 0.2 % of this area

Ironbound Mountain Formation, Felsic volcanic member.

Lithology: felsic volcanic rock

Porphyritic hornblende or alkalic amphibole quartz syenite (Jurassic) at surface, covers 0.3 % of this area

Porphyritic hornblende or alkalic amphibole quartz syenite.

Lithology: quartz syenite

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

Devonian - Precambrian Z Gonic Formation

Lithology: schist; phyllite

Aziscohos Formation, Upper unnamed member (Upper Cambrian? - Lower Ordovician?) at surface, covers 0.1 % of this area

Aziscohos Formation, Upper unnamed member - Gray metapelite containing sparse siltstone laminations and abundant lenses of vein quartz.

Lithology: meta-argillite; siltstone

Tonalite, diorite, granodiorite, and granite (Late Ordovician ) at surface, covers 0.4 % of this area

Tonalite, diorite, granodiorite, and granite - More mafic rocks have hornblende; part of Lost Nation pluton.

Lithology: tonalite; diorite; granodiorite; granite

Partridge Formation, White quartz-kyanite rock (Middle - Upper Ordovician) at surface, covers < 0.1 % of this area

Partridge Formation, White quartz-kyanite rock.

Lithology: schist

Devonian granodiorite (Devonian) at surface, covers < 0.1 % of this area

Devonian granodiorite - biotite granodiorite

Lithology: granodiorite