Geologic units in New Hampshire (state in United States)

Additional scientific data in this geographic area

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

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

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

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

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

Gray two-mica granite, locally grading to tonalite.

Bethlehem Granodiorite (Early Devonian) at surface, covers 4 % of this area

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

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

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

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

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

(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.

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

Winnipesaukee Tonalite (Early Devonian) at surface, covers 3 % 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.

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

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

Frontenac Formation, undivided (Silurian?) at surface, covers 2 % of this area

Interbedded thick feldspathic wackes, tan and green slates, and minor calcareous lenses.

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

Pink, moderately to weakly foliated.

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.

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

Quartzose-feldspathic gneiss and biotite schists (locally rusty), granofels, and cal-silicate rocks closely intruded by, and grading into, a pink gneissic granite (623 Ma) that produced a migmatite.

Ammonoosuc Volcanics, Bimodal volcanic rocks (Middle - Upper Ordovician) at surface, covers 2 % of this area

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

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

Thinly laminated, "pin-striped" gray, green, or tan metapelite and quartzite.

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

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

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

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.

Rangeley Formation, undivided (Lower Silurian (Llandoverian)) at surface, covers 1 % of this area

Rangeley Formation, undivided.

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.

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

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

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

Contains more calc-silicate (15 percent) than does the remainder of the formation (5 percent).

Littleton Formation, Upper unnamed member (Lower Devonian) at surface, covers 1 % of this area

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

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

Granite, granodiorite, and tonalite.

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

Similar to Concord Granite.

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

Found in northern New Hampshire.

Partridge Formation, undivided (Middle - Upper Ordovician) at surface, covers 0.9 % of this area

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

Partridge Formation (Upper Ordovician) at surface, covers 0.8 % of this area

Dark-gray to grayish-black, rusty-weathering sulfidic slate and phyllite interlayered with felsic volcanic rocks and tuffs, and amphibolite (Opa). Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

Albee Formation (Ordovician and Cambrian) at surface, covers 0.8 % of this area

Light-gray to greenish-gray, white-weathering, fine-grained feldspathic metasandstone and metasiltstone, and light-gray to greenish-gray to dark-gray phyllite. Lesser amounts of quartzite. Rare calc-silicate nodules. Generally sharply bedded, but graded beds as well as slump structures are locally obvious. Tourmaline is a sporadic accessory mineral. May be sulfidic (either pyrite or pyrrhotite) and rusty weathering. “Pinstriping” is common. U-Pb zircon SHRIMP age of 492.5±7.8 Ma from a porphyritic tonalite sill about 2 km east of West Bath, N.H. (D.W. Rankin, USGS, unpub. data, 2011). Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

Granodiorite to tonalite (Late Ordovician) at surface, covers 0.7 % of this area

Granodiorite to tonalite.

Ammonoosuc Volcanics of Billings (1935) - undivided (Upper and Middle Ordovician) at surface, covers 0.7 % of this area

A heterogeneous unit of interlayered and interfingering metamorphosed volcanic, volcaniclastic, and sedimentary rocks. Compositions range from basalt to sodic rhyolite. Fragmental rocks dominate (tuff to tuff breccia), but include sparse mafic pillow lava and felsic lava. Sedimentary protoliths include dark-gray sulfidic shale, ironstone, siltstone, graywacke, volcanic conglomerate, and rare limestone. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

Waits River Formation - muscovite porphyroblastic carbonaceous schist member (staurolite-grade rocks) (Lower Devonian and Upper Silurian) at surface, covers 0.7 % of this area

Dark-gray to coaly-black, fine-grained plagioclase-muscovite-quartz schist and metawacke, shown southeast of Springfield; in part correlative with staurolite-grade rocks mapped as Littleton Formation (Dl) flanking the Vernon dome (shown as DSwb/Dl). Part of the Connecticut Valley Trough.

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

Pink Conway-type granite of Kingsley (1931).

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

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

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

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

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

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

Interbedded gray phyllite, in places containing feldspathic clasts, and feldspathic metasandstone, variably graded.

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

Contains minor muscovite. Found in Milford quadrangle.

Ammonoosuc Volcanics, Metabasalt (Middle - Upper Ordovician) at surface, covers 0.5 % of this area

Ammonoosuc Volcanics, Metabasalt.

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

Metabasalt interbeds.

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

Perry Mountain and Rangeley Formations, undivided.

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

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

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

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).

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

Biotite granodiorite.

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

Madrid and Smalls Falls Formations, undivided.

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

Hornblende (or alkalic amphibole) syenite.

Oliverian Plutonic Suite - granodioritic to quartz dioritic gneissic (Late Ordovician) at surface, covers 0.3 % of this area

Granodioritic to quartz dioritic gneissic border phase of Oobg, perhaps in part metasomatic. Part of the Bronson Hill arch intrusive rocks.

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

Hornblende-biotite granite.

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

Fitch and Clough Formations, undivided.

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

Frontenac Formation, Proximal bimodal volcanic facies.

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.

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.

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

Hornblende-biotite quartz syenite to syenite.

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

Granite, granodiorite, and trondhjemite.

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

Porphyritic hornblende or alkalic amphibole quartz syenite.

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

Found in Woodsville and Whitefield quadrangles and in small intrusive units in northern and southeastern New Hampshire.

Littleton Formation (Lower Devonian) at surface, covers 0.3 % of this area

Medium-dark- to dark-gray slate interlayered with light-gray, fine-grained micaceous quartzite; in southeastern Vermont near the Vernon dome Dl is equated with DSwb and may be older than in the Bradford area. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Light-colored to gray schists and gneisses, quartzites, and amphibolites. Variably migmatized and mylonized. Contact with Kittery Formation on west is the Portsmouth Fault.

Gile Mountain Formation - thick-bedded micaceous feldspathic quartzite member (Lower Devonian) at surface, covers 0.3 % of this area

Brown to gray, noncarbonaceous quartz-mica schist and feldspathic quartzite in beds 50 cm to 5 m thick; gradational to Dgqs through interbedding of phyllite beds and decrease in thickness of quartzite beds. Part of the Connecticut Valley Trough.

Lost Nation granite (Early Silurian to Middle Ordovician) at surface, covers 0.3 % of this area

Foliated biotite and (or) hornblende granite; locally diorite and lesser amounts of gabbro. Where present, potassium feldspar is microcline. Contact aureole is in the Albee Formation. U-Pb zircon ages of 442±4 Ma, no. 30 (Moench and Aleinikoff, 2003), and 444.1±2.1 Ma, no. 29 (Rankin and Tucker, 2009); and U-Pb sphene age of 443±3 Ma, no. 31 (Moench and Aleinikoff, 2003). Part of the Highlandcroft Plutonic Suite: Epizonal to mesozonal, foliated and metamorphosed (greenschist facies) plutons exposed northwest of the Ammonoosuc fault. Compositions range from granite to diorite to lesser amounts of gabbro. Part of the Bronson Hill arch intrusive rocks.

Tonalite, diorite, granodiorite, and granite (Late Ordovician) at surface, covers 0.3 % of this area

More mafic rocks have hornblende; part of Lost Nation pluton.

Ammonoosuc Volcanics of Billings (1935) - metarhyolite tuff, lapilli tuff, tuff breccia, and lava (Upper and Middle Ordovician) at surface, covers 0.2 % of this area

Greenish-gray, light-bluish-gray, or medium-bluish-gray metarhyolite tuff, lapilli tuff, tuff breccia, and lava. Generally porphyritic with 5 to 20 percent plagioclase and, in some places, quartz phenocrysts. Generally strongly foliated with waxy sheen on foliation surfaces. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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.

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

Hornblende or alkalic amphibole quartz syenite.

Clough Quartzite (Lower Silurian (upper Llandoverian)) at surface, covers 0.2 % of this area

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.

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

Porphyritic (alkalic feldspar) biotite granite.

Frontenac Formation (Devonian and Silurian) at surface, covers 0.2 % of this area

Thick-bedded, ankeritic, micaceous, and feldspathic metasandstones interlayered with subordinate dark-gray metapelite. Metasandstone beds commonly are rusty weathering and up to 4 m thick; calc-silicate lenses locally present. Part of the Connecticut Valley Trough.

Rhyolite and fine-grained granite (Cretaceous) at surface, covers 0.2 % 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.

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

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

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

Rusty, dark metapelite containing thin coticule laminations, feldspathic metatuff, and vein quartz lenses.

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

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

Ironbound Mountain Formation, Felsic volcanic member.

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

Contains riebeckite and (or) hastingsite.

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.

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

Found in Percy quadrangle of northern New Hampshire.

Rangeley Formation (Lower Silurian) at surface, covers 0.2 % of this area

Interlayered, commonly rusty-weathering quartz-feldspar micaceous granofels and dark-gray mica schist containing porphyroblasts of garnet, staurolite, and kyanite. Calc-silicate lenses common in the granofels; granule and pebble metaconglomerate locally are present. Part of Piermont and other allochthons.

Ammonoosuc Volcanics of Billings (1935) - metamorphosed andesitic and basaltic tuff, crystal tuff, and tuff breccia (Upper and Middle Ordovician) at surface, covers 0.2 % of this area

Dark-greenish-gray to medium-bluish-gray metamorphosed andesitic and basaltic tuff, crystal tuff, and tuff breccia; minor pillow lava. Commonly contains plagioclase and (or) altered mafic phenocrysts. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

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

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

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

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

Hastingsite or hornblende and (or) hedenbergite are present.

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

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

Albee Formation - Scarritt member (Ordovician and Cambrian) at surface, covers 0.1 % of this area

Dark-gray slate interlayered with thin beds of light-gray, fine-grained micaceous and feldspathic metasandstone (typically ribby weathering). Abruptly graded beds <1 cm to 30 cm thick are locally common as is channeling and, in places, soft-sediment deformation. Commonly sulfidic and rusty weathering. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

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

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

Quartz-pebble conglomerate overlain by rusty metapelite and feldspathic quartzite.

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

Hornblende quartz monzonite.

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.

Kinsman Quartz Monzonite of Billings (1955) (Early Devonian) at surface, covers 0.1 % of this area

Medium- to coarse-grained, potassium-feldspar-megacrystic, biotite granodiorite gneiss of the Ashuelot pluton. U-Pb zircon age of 403±2 Ma (R.D. Tucker, USGS, written commun., 2008). Part of the Bronson Hill arch intrusive rocks.

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

Alkalic amphibole or fayalite may be present. Part of Ossipee Mountain Complex of Kingsley (1931).

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

Blastomylonitic quartz-feldspar granitic gneiss and pegmatite intruded the Rye Complex and formed a migmatite.

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

Ammonoosuc Volcanics, Bimodal volcanic rocks.

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

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

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

Gray metapelite containing sparse siltstone laminations and abundant lenses of vein quartz.

Trondhjemite (Late Ordovician) at surface, covers 0.1 % of this area

Contains biotite and hornblende.

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

Northernmost New Hampshire.

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

Composition ranges from quartz monzonite to diorite.

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

Medium- to coarse-grained, equigranular to porphyritic, muscovite-biotite-microcline-plagioclase metaquartz monzonite; contains garnet, sillimanite-andalusite and cordierite; intrudes rocks of the Rangeley Formation in New Hampshire. U-Pb zircon age of 407±5 Ma, no. 43 (Kohn and others, 1992) at Bellows Falls. Part of the Bronson Hill arch intrusive rocks.

Oliverian Plutonic Suite - biotite granite (Late Ordovician) at surface, covers < 0.1 % of this area

Pink, medium-grained muscovite-biotite-microcline-perthite granite and gneissic granite, and aplite of the Lebanon dome. Part of the Bronson Hill arch intrusive rocks.

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.

Clough Quartzite - quartzite and quartz-cobble metaconglomerate (Lower Silurian) at surface, covers < 0.1 % of this area

Quartzite and quartz-cobble metaconglomerate. Locally contains quartz-cobble conglomerate with abundant dark-gray phyllite matrix that resembles phyllite of the Littleton Formation. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

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

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

Frontenac Formation, Mixed volcanic and sedimentary facies.

Waits River Formation - slate and phyllite member (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Predominantly dark- to light-gray, lustrous, carbonaceous chlorite-biotite-muscovite-quartz slate, phyllite, or schist; contains thin beds of quartzite and only sparse layers of punky-weathering limestone. Shown south of the Pomfret dome where rocks typical of the Gile Mountain Formation are absent, and near Randolph. Part of the Connecticut Valley Trough.

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

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

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

Augite monzodiorite.

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

Ammonoosuc Volcanics, Metasedimentary rocks.

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

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

Waits River Formation - carbonaceous phyllite and limestone member (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Dark-gray to silvery-gray, lustrous, carbonaceous muscovite-biotite-quartz (±garnet) phyllite containing abundant beds of punky-brown-weathering, dark-bluish-gray micaceous quartz-rich limestone in beds ranging from 10 cm to 10 m thick. Part of the Connecticut Valley Trough.

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

Ammonoosuc Volcanics, Volcaniclastic metagraywackes.

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

Black phyllite at western contact of the Eliot Formation.

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

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

Fitch Formation (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Metamorphosed limestone, calcareous sandstone, siltstone, and pelite. Some limestone conglomerate and polymict conglomerate with calcareous matrix. Locally equivalent to Madrid and Smalls Falls Formations in Chesterfield, N.H., area. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Amphibolite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Littleton Formation, Epiclastic metavolcanic sediments.

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

Part of Lost Nation pluton of northwestern New Hampshire.

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

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.

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

Contains hornblende, biotite, and hedenbergite.

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

Gray, medium-grained tonalite and granodiorite.

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

Contains minor muscovite. Makes up Cambridge Black pluton.

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

Thickly bedded feldspathic volcaniclastic grit and interbedded gray slate. Equivalent to Grenier Ponds Member of the Ironbound Mountain Formation in western Maine.

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

Found in northwestern New Hampshire.

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

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

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

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..

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

Biotite trondhjemite in Rumney quadrangle.

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.

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

Hornblende amphibolite and hornblende-plagioclase-quartz granofels; interpreted as metabasaltic and volcaniclastic rocks. Part of the Connecticut Valley Trough.

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

Porphyritic phase of hornblende-biotite tonalite.

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.

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

Porphyritic granite.

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

Dark-gray slate and phyllite containing sparse to moderately abundant beds of light-gray, fine-grained metasandstone and metasiltstone, 1 mm to 1 cm thick. Part of the Connecticut Valley Trough.

Ammonoosuc Volcanics of Billings (1935) - metasiltstone and phyllite (Upper and Middle Ordovician) at surface, covers < 0.1 % of this area

Medium-light-bluish-gray, medium-bluish-gray, medium-dark-gray, to medium-dark-greenish-gray metasiltstone and phyllite, and medium-gray feldspathic metawacke. Purple tinge common; coticule and magnetite locally abundant. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Chiefly in northern New Hampshire.

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

White-weathering, medium- to dark-gray, foliated and laminated, aphanitic to very fine grained granofels to schist or metatuff, welded tuff, and lithic tuff commonly with a few percent millimeter-size quartz and microcline phenocrysts. U-Pb zircon age of 407.5±3.9 Ma, no. 44 (Rankin and Tucker, 2000). Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Gray augite-hornblende-biotite monzonite.

Ammonoosuc Volcanics of Billings (1935) - metamorphosed aphyric rhyolite tuff (Upper and Middle Ordovician) at surface, covers < 0.1 % of this area

Metamorphosed aphyric rhyolite tuff. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Leucocratic granite to quartz syenite.

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

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.

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

Spatially associated with Spaulding Tonalite plutons.

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

Found at Red Hill in Mt. Chocorua quadrangle (see index accompanying ""Sources of Map Data"").

Ironbound Mountain Formation - rhythmically graded member (Lower Devonian) at surface, covers < 0.1 % of this area

Light- to medium-gray, fine-grained micaceous metasandstones that grade upward into subordinate dark-gray slate or phyllite; some rocks are calcareous. Graded sets range in thickness from a few centimeters to about a meter; typically they are 10 to 30 cm thick. Contact with Di gradational. Part of the Connecticut Valley Trough.

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

Hornblende granodiorite.

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

Medium-grained porphyritic granite.

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

Fine- to coarse-grained.

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

Medium-dark-gray to grayish-black lustrous slate, phyllite, and schist containing sparse to moderately abundant 1-mm to- 5-cm-thick beds of light-gray, fine-grained metasandstone and metasiltstone, commonly pyritiferous and calcareous. Some graded beds. Gradational contact with Dco above and Dir below. Interpreted to be correlative with the Meetinghouse Slate Member of the Gile Mountain Formation. Part of the Connecticut Valley Trough.

Highlandcroft Granodiorite of Billings (1935, 1937) (Early Silurian to Middle Ordovician) at surface, covers < 0.1 % of this area

Medium-greenish-gray to dark-greenish-gray, medium-grained, foliated metamorphosed granite, granodiorite, and tonalite containing quartz, microcline, saussuritized plagioclase, hornblende, biotite (chlorite alteration), and secondary calcite and sericite. Nonconformably overlain by the Clough Quartzite and Fitch Formation. U-Pb zircon age of 450±5 Ma, no. 28 (Lyons and others, 1986). Part of the Highlandcroft Plutonic Suite: Epizonal to mesozonal, foliated and metamorphosed (greenschist facies) plutons exposed northwest of the Ammonoosuc fault. Compositions range from granite to diorite to lesser amounts of gabbro. Part of the Bronson Hill arch intrusive rocks.

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

Pink to gray; hastingsite or riebeckite in some varieties.

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

Both mafic and felsic

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

Leucocratic, pink or light-brown, and mesoperthitic.

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

Has varying amounts of olivine, augite, and hornblende.

Waits River Formation - felsic volcanic member (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Light-gray to grayish-green, chlorite-biotite-muscovite-plagioclase-quartz schist and fragmental quartz-plagioclase granofels or metatuff. In Springfield, contains a dated metafelsite layer interpreted as a dike cutting the Standing Pond Volcanics, that yielded a U-Pb zircon TIMS age of 423±4 Ma, no. 32 (Aleinikoff and Karabinos, 1990; Hueber and others, 1990). Part of the Connecticut Valley Trough.

Gile Mountain Formation - quartzite and metapelite member (Lower Devonian) at surface, covers < 0.1 % of this area

Gray to light-gray, fine-grained micaceous quartzite a few centimeters to tens of centimeters thick, interbedded with dark-gray graphitic slate, phyllite, or schist. Part of the Connecticut Valley Trough.

Clough Quartzite - lower conglomerate and granofels (Lower Silurian) at surface, covers < 0.1 % of this area

On Skitchewaug Mountain, lower conglomerate and granofels. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Gray to black, coarse-grained, porphyritic. Found in Mt. Pawtuckaway quadrangle.

Fairlee Quartz Monzonite (Early Devonian) at surface, covers < 0.1 % of this area

Greenish-gray, pink-tinged, weakly foliated, coarse-grained to porphyritic biotite granite of the Fairlee pluton. U-Pb zircon age of 410±5 Ma, no. 42 (Moench and Aleinikoff, 2003). Part of the Bronson Hill arch intrusive rocks.

Ammonoosuc Volcanics of Billings (1935) - sulfidic slate and phyllite (Upper and Middle Ordovician) at surface, covers < 0.1 % of this area

Dark-gray to grayish-black, rusty-weathering sulfidic slate and phyllite interlay-ered with felsic tuffs and minor sandy rocks; locally forms the base of the Ammonoosuc Volcanics. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

Albee Formation - magnetite-rich areas (Ordovician and Cambrian) at surface, covers < 0.1 % of this area

Magnetite-rich areas of the Albee Formation (OCal) - Shown as an overprint. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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.

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

Locally fossiliferous in Whitefield quadrangle.

Biotite-quartz diorite gneiss of Vernon dome (Late Ordovician) at surface, covers < 0.1 % of this area

Light-gray, well-foliated subporphyritic biotite (±hornblende)-quartz diorite and trondhjemite gneiss; forms sills in overlying Ammonoosuc Volcanics. Part of the Bronson Hill arch intrusive rocks.

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.

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

Ammonoosuc Volcanics, Felsic metavolcanic rocks.

Sawyer Mountain Formation (Devonian and Silurian) at surface, covers < 0.1 % of this area

Greenish-gray to dark-gray, pyritic, locally calcareous phyllite and light-gray, locally pyritic and calcareous, fine- to medium-grained, feldspar-rich metasandstone; some beds punky weathering. Graded grit and conglomerate beds (having cobble-size clasts of quartz and felsite) toward base. Interpreted as transitional between Connecticut Valley and Bronson Hill sequences and correlative with Frontenac Formation. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Within unit Sr; rusty sulfidic schist occurs in Fall Mountain nappe near Bellows Falls. Part of Piermont and other allochthons.

Moulton Diorite (Early Devonian) at surface, covers < 0.1 % of this area

Dark-gray, medium-grained metadiorite composed mainly of secondary minerals such as saussuritized plagioclase, amphibole, epidote, chlorite, and calcite. Part of the Bronson Hill arch intrusive rocks.

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

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

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

Thin-bedded muscovite-biotite-garnet-staurolite-kyanite schist and micaceous quartz-feldspar granofels; some calc-silicate lenses and layers. Part of Piermont and other allochthons.

French Pond Granite (Late Devonian) at surface, covers < 0.1 % of this area

Pink to gray, nonfoliated, porphyritic to coarse-grained biotite granite; phenocrysts of potassium feldspar are as large as 2 by 3 cm. U-Pb zircon age of 364±5 Ma, no. 50 (Moench and Aleinikoff, 2003). Part of the Bronson Hill arch intrusive rocks.

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

Devonian - Silurian Rindgemere Formation lower member

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

Hornblende-biotite tonalite.

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

Chiefly amphibolites, found in southwestern New Hampshire.

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

Ironbound Mountain Formation, Euxinic metashale member.

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.

Clough Quartzite - upper quartzite (Lower Silurian) at surface, covers < 0.1 % of this area

On Skitchewaug Mountain, upper quartzite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

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

Joslin Turn Tonalite (Early Silurian to Middle Ordovician) at surface, covers < 0.1 % of this area

Greenish-gray to light-brownish-gray, medium-grained, weakly foliated metamorphosed tonalite. Primary minerals include quartz, plagioclase, biotite, magnetite, pyrite, and apatite; secondary minerals include chlorite, epidote, sericite, and calcite. Granophyric intergrowths of quartz and plagioclase. U-Pb zircon age of 469±1.5 Ma, no. 27 (Moench and Aleinikoff, 2003). Part of the Highlandcroft Plutonic Suite: Epizonal to mesozonal, foliated and metamorphosed (greenschist facies) plutons exposed northwest of the Ammonoosuc fault. Compositions range from granite to diorite to lesser amounts of gabbro. Part of the Bronson Hill arch intrusive rocks.

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

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

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

Ironbound Mountain Formation, Basaltic to andesitic member.

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

Commonly contains alkalic amphibole and mesoperthite.

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

Almost-white to dark-gray, locally pink, medium- to coarse-grained hypidiomorphic, granular, biotite-muscovite-microcline-plagioclase granite; accessories include apatite, sphene, pyrite, and magnetite. Igneous rocks of the Northeast Kingdom batholith of Ayuso and Arth (1992). Part of the New Hampshire Plutonic Suite.

Oliverian Plutonic Suite - hornblende metagabbro (Late Ordovician) at surface, covers < 0.1 % of this area

Dark-green, coarse-grained, well-foliated hornblende-andesine metagabbro. Part of the Bronson Hill arch intrusive rocks.

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

Devonian granite

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

Foliated to nonfoliated, fine-grained to pegmatitic metagabbro, metadiorite, and metatonalite; aplitic metatonalite; and metadiabase. U-Pb zircon ages of pegmatitic metadiorite from three bodies (Comerford quarry, Leighton Hill, and Peaked Mountain) are, respectively, 419.8±2.6 Ma, no. 33; 419.3±1.3 Ma, no. 34; and 418.5±2.0 Ma, no. 35 (Rankin and others, 2007). Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).

Ammonoosuc Volcanics of Billings (1935) - metarhyolite tuff, lapilli tuff, and tuff breccia (Upper and Middle Ordovician) at surface, covers < 0.1 % of this area

Coarsely porphyritic, greenish-gray, light-bluish-gray, or medium-bluish-gray metarhyolite tuff, lapilli tuff, and tuff breccia. Quartz and plagioclase phenocrysts commonly as large as 5 mm. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Found in Mt. Cube quadrangle.

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.

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.

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

Found in south-central New Hampshire.

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

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).

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

Binary and biotite granite and granodiorite, undifferentiated. Includes small dikes labeled Dg. Part of the New Hampshire Plutonic Suite.

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

Ordovician - Cambrian Dead River formation lower member

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

Littleton Formation, Metabasaltic greenstone or amphibolite.

Granite and trondhjemite dikes of Chester and Athens domes and west of the Connecticut Valley trough (Devonian) at surface, covers < 0.1 % of this area

Light-gray to white, garnet-muscovite-biotite granodiorite at Gassetts quarry, having a U-Pb zircon SHRIMP age of 392±6 Ma, no. 46 (Aleinikoff and others, 2011), from rims on Proterozoic-age cores (J.N. Aleinikoff, USGS, written commun., 2002); and whitish-gray muscovite-rich quartz monzonite and granodiorite, granite pegmatite, and aplite which occur as crosscutting nonfoliated dikes within the core of the domes and as folded and well-foliated dikes on the east and west flanks of the domes; also granite dikes and small stocks of very light gray to white, muscovite-rich, locally garnet-bearing, fine- to medium-grained biotite-muscovite quartz monzonite and granodiorite, locally orbicular, that intrude cover rocks east of the Green Mountain massif from Jamaica to Northfield, including the Liberty Hill locality and the granodiorite stock east of Plymouth. The latter contains inherited zircon with rims having an imprecise SHRIMP age of about 380 to 390 Ma (Aleinikoff and others, 2011); a similar dike south of Plymouth has a U-Pb zircon SHRIMP age of 365±5 Ma, no. 49 (Aleinikoff and others, 2011). These closely resemble undated white granodiorites of the Bethel area and dikes in the Chester and Athens domes; also resemble small dikes of granite, trondhjemite, and quartz monzonite largely west of the Connecti-cut Valley trough. Devonian granitic rocks of southern Vermont. Part of the New Hampshire Plutonic Suite.

Waits River Formation - muscovite porphyroblastic carbonaceous schist member (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Dark-gray to coaly-black, fine-grained plagioclase-muscovite-quartz schist and metawacke, shown southeast of Springfield; in part correlative with staurolite-grade rocks mapped as Littleton Formation (Dl) flanking the Vernon dome (shown as DSwb/Dl). Part of the Connecticut Valley Trough.

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.

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

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).

Comerford Intrusive Complex - metatholeiitic mafic dikes (Late Silurian) at surface, covers < 0.1 % of this area

Abundant, foliated to weakly foliated, metatholeiitic mafic dikes; some sheeted. Shown as overprint. Part of the Lake Memphremagog Intrusive Suite (425±3 Ma to 418.5±2 Ma).

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

Ironbound Mountain Formation, Metarhyolite and microgranite intrusions.

Littleton Formation - metamorphosed mafic volcanic rocks (Lower Devonian) at surface, covers < 0.1 % of this area

Metamorphosed mafic volcanic rocks. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Silurian granite

Ammonoosuc Volcanics of Billings (1935) - siliceous and argillaceous dolomite and calcareous pelite (Upper and Middle Ordovician) at surface, covers < 0.1 % of this area

Siliceous and argillaceous dolomite and calcareous pelite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Biotite granodiorite

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.

Monadnock Mountain pluton - quartz syenite (Middle Jurassic) at surface, covers < 0.1 % of this area

Greenish-gray to pink hornblende-biotite quartz syenite. Monadnock Mountain pluton: Composite stock of quartz syenite, syenite granite, and essexite. K-Ar age of 175±4 Ma (Foland and Faul, 1977). Part of the White Mountain Igneous Suite.

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

Ordovician - Cambrian unnamed volcanic rocks

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

Greenish-gray, light-bluish-gray, or medium-bluish-gray metarhyolite tuff, lapilli tuff, tuff breccia, and lava. Generally porphyritic with 5 to 20 percent plagioclase and, in some places, quartz phenocrysts and minor amphibolite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

Jurassic granite - Jurassic biotite granite undivided

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

Devonian Ironbound Mountain Formation

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

Muscovite-biotite granite

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

Cambrian Hurricane Mountain Formation

Massabesic Gneiss Complex (Late Proterozoic) at surface, covers < 0.1 % of this area

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

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

Ordovician - Cambrian Aziscohos Formation

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

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).

Waits River Formation - volcaniclastic rock member (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Silvery-grayish-green to light-gray, muscovite-biotite (chlorite)-plagioclase-quartz schist and granofels. Part of the Connecticut Valley Trough.

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

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).

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

Devonian - Precambrian Z Gonic Formation

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

Silurian - Ordovician Frontenac Formation

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

Silurian - Precambrian Z Kittery Formation

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

Biotite-hornblende granodiorite.

Rangeley Formation - quartz conglomerate (Lower Silurian) at surface, covers < 0.1 % of this area

Within unit Sr; quartz conglomerate occurs in Fall Mountain nappe near Bellows Falls. Part of Piermont and other allochthons.

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

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

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

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).

Dikes and sills of porphyritic and nonporphyritic metarhyolite of Hunt Mountain intrusive into the Albee Formation (Early Devonian) at surface, covers < 0.1 % of this area

Some contain xenoliths of dikes of the Comerford Intrusive Complex (Scd). U-Pb zircon ages of 414±4 Ma, no. 40, and 412±2 Ma, no. 41 (Lyons and others, 1997; Moench and others, 1995). Part of the Bronson Hill arch intrusive rocks.

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

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

Ordovician unnamed volcanic and sedimentary rocks

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

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).

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

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

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

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

Cambrian Jim Pond Formation graywacke

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

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

Ordovician gabbro/diorite/ultramafic rocks

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

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).

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

Includes volcanic debris flow, laminated tuff, and strongly foliated felsite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.

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

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).

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

Devonian pyroxene-hornblende quartz monzodiorite and quartz diorite - pyroxene-hornblende-biotite quartz monzodiorite, and pyroxene-hornblende-biotite quartz diorite

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

Muscovite-biotite granite

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

Ordovician - Cambrian Dead River formation

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

In the Townsend area; commonly contains pink magnetite-bearing pegmatite identical to granite of Milford, New Hampshire; intrudes OZma and Sp.

Waits River Formation - mafic member (Lower Devonian and Upper Silurian) at surface, covers < 0.1 % of this area

Massive, coarse-grained hornblende-plagioclase gneiss and granofels; finely foliated hornblende-plagioclase amphibolite; actinolite-epidote-chlorite greenstone. Part of the Connecticut Valley Trough.