(Kinsman Quartz Monzonite of Billings, 1955) - Foliated granite, granodiorite, tonalite, and minor quartz diorite; large megacrysts of potassium feldspar characteristic; garnet locally abundant.
(Bethlehem Gneiss of Billings, 1955) - Gray, strongly foliated biotite-muscovite granodiorite and associated tonalite and granite.
Typically pink, coarse-grained mesoperthitic biotite (amphibole-free) granite; locally fine-grained or porphyritic.
Ammonoosuc Volcanics, Bimodal volcanic rocks - Locally includes unmapped Oals.
Thinly or poorly bedded aluminous lower part, somewhat rusty. Rare quartzite lentils. Carrabassett Formation in northwestern Maine is probably correlative.
Pink, moderately to weakly foliated.
Light-gray metaturbidite, lithologically identical to, and probably correlative with, the Seboomook Formation of Maine. Coticule layers common.
Gray two-mica granite, locally grading to tonalite.
Granodiorite to tonalite.
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.
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.
Mount Osceola Granite, Granite containing hornblende and, locally, hastingsite, ferrohedenbergite, or fayalite.
Gray metapelite and metawacke and subordinate metavolcanic rocks; generally, but not everywhere, conformable with underlying Fitch or Madrid Formations. Fossiliferous in western New Hampshire.
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.
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.
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).
Sharply interbedded quartzites, light-gray nongraphitic metapelite, and "fast-graded" meta-turbidites. Coticule layers common.
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.
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.
Black, rusty-weathering sulfidic-graphitic slate or schist and sparse to abundant metagraywacke. Lies stratigraphically between upper and lower parts of the Ammonoosuc Volcanics.
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.
Found in Woodsville and Whitefield quadrangles and in small intrusive units in northern and southeastern New Hampshire.
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.
Fitch and Clough Formations, undivided.
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 granodiorite.
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.
(Winnipesaukee Quartz Diorite of Billings, 1955) - Gray, massive to foliated tonalite and minor quartz diorite, granodiorite, and granite. Probably coeval with Spaulding Tonalite.
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.
Ammonoosuc Volcanics, Metabasalt.
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.
Ammonoosuc Volcanics, Bimodal volcanic rocks.
Granodioritic to quartz dioritic gneissic border phase of Oobg, perhaps in part metasomatic. Part of the Bronson Hill arch intrusive rocks.
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.
Perry Mountain Formation, Sedimentary and subordinate distal felsic and mafic volcanic facies in Piermont allochthon.
Porphyritic hornblende or alkalic amphibole quartz syenite.
Rangeley Formation, undivided.
(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.
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.
Littleton Formation, Epiclastic metavolcanic sediments.
Ammonoosuc Volcanics, Metasedimentary rocks.
Amphibolite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
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.
Formations unidentifiable owing to obliteration of original sedimentary or volcanic characteristics by anatexis or by numerous intrusions.
Porphyritic (alkalic feldspar) biotite granite.
Biotite trondhjemite in Rumney quadrangle.
Hastingsite or hornblende and (or) hedenbergite are present.
Dark-gray; found in southeastern and western New Hampshire.
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.
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.
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.
Similar to Concord Granite.
Hornblende (or alkalic amphibole) syenite.
Hornblende granodiorite.
Metamorphosed aphyric rhyolite tuff. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
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.
Metamorphosed limestone, calcareous sandstone, siltstone, and dark pelitic schist; lower contact is disconformable on the Clough Quartzite. Fossiliferous.
Gray augite-hornblende-biotite monzonite.
Both mafic and felsic
Bedded and ignimbritic tuffs, flows, and breccias; also porphyritic rhyolite and minor trachyte.
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.
Ammonoosuc Volcanics, Volcaniclastic metagraywackes.
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.
Has varying amounts of olivine, augite, and hornblende.
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.
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.
Magnetite-rich areas of the Albee Formation (OCal) - Shown as an overprint. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Ammonoosuc Volcanics, Felsic metavolcanic rocks.
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.
Alkalic amphibole or fayalite may be present. Part of Ossipee Mountain Complex of Kingsley (1931).
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.
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.
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.
Black graphitic-sulfidic rusty-weathering schist and thickly bedded metagraywacke.
Fine- to coarse-grained.
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.
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.
Possibly equivalent in part to Hildreths Formation of Maine but not restricted to one horizon. Locally fossiliferous, as in Moosilauke quadrangle.
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.
Hornblende or alkalic amphibole quartz syenite.
Locally fossiliferous in Whitefield quadrangle.
Dark-green, coarse-grained, well-foliated hornblende-andesine metagabbro. Part of the Bronson Hill arch intrusive rocks.
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).
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.
Found in Mt. Cube quadrangle.
Perry Mountain Formation, Volcanic facies in Piermont allochthon.
Metavolcanic and metasedimentary rocks of the lower part of Ammonoosuc Volcanics, undivided.
Binary and biotite granite and granodiorite, undifferentiated. Includes small dikes labeled Dg. Part of the New Hampshire Plutonic Suite.
Littleton Formation, Metabasaltic greenstone or amphibolite.
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).
Metamorphosed mafic volcanic rocks. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Siliceous and argillaceous dolomite and calcareous pelite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.
Contains riebeckite and (or) hastingsite.
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.
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.
Chiefly in northern New Hampshire.
Includes volcanic debris flow, laminated tuff, and strongly foliated felsite. Stratified rocks of the Bronson Hill arch and Sawyer Mountain belt.