Geologic units in Sullivan county, New Hampshire

Additional scientific data in this geographic area

Bethlehem Granodiorite (Early Devonian) at surface, covers 29 % of this area

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

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.

Ammonoosuc Volcanics of Billings (1935) - undivided (Upper and Middle Ordovician) at surface, covers 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.

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

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

Waits River Formation - muscovite porphyroblastic carbonaceous schist member (staurolite-grade rocks) (Lower Devonian and Upper Silurian) at surface, covers 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.

Partridge Formation, undivided (Middle - Upper Ordovician) at surface, covers 5 % 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.

Gile Mountain Formation - thick-bedded micaceous feldspathic quartzite member (Lower Devonian) at surface, covers 5 % 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.

Granite, granodiorite, and trondhjemite (Late Ordovician) at surface, covers 4 % of this area

Granite, granodiorite, and trondhjemite.

Partridge Formation (Upper Ordovician) at surface, covers 3 % 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.

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

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

Lower part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 2 % 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.

Upper part of Rangeley Formation (Lower Silurian (Llandoverian)) at surface, covers 2 % 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.

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

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

Fitch and Clough Formations, undivided (Silurian) at surface, covers 2 % of this area

Fitch and Clough Formations, undivided.

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

Contains biotite and hornblende.

Waits River Formation - carbonaceous phyllite and limestone member (Lower Devonian and Upper Silurian) at surface, covers 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.

Clough Quartzite (Lower Silurian (upper Llandoverian)) at surface, covers 1 % 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.

Waits River Formation - slate and phyllite member (Lower Devonian and Upper Silurian) at surface, covers 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.

Concord Granite (Late Devonian) at surface, covers 1 % of this area

Gray two-mica granite, locally grading to tonalite.

Bethlehem Gneiss (Early Devonian) at surface, covers 0.9 % 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.

Clough Quartzite - quartzite and quartz-cobble metaconglomerate (Lower Silurian) at surface, covers 0.8 % 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.

Fitch Formation (Upper Silurian; Pridolian and Ludlovian) (Upper Silurian - (Pridolian and Ludlovian)) at surface, covers 0.8 % of this area

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

Gile Mountain Formation - amphibolite member (Lower Devonian) at surface, covers 0.7 % of this area

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

Spaulding Tonalite (Early Devonian) at surface, covers 0.5 % 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.

Rangeley Formation (Lower Silurian) at surface, covers 0.5 % 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.

Gile Mountain Formation - Meetinghouse Slate member (Lower Devonian) at surface, covers 0.4 % 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.

Littleton Formation, Upper unnamed member (Lower Devonian) at surface, covers 0.4 % of this area

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

Waits River Formation - felsic volcanic member (Lower Devonian and Upper Silurian) at surface, covers 0.3 % 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.

Member C (uppermost) of the Rangeley Formation in Maine and northeastern and southwestern New Hampshire (Lower Silurian (Llandoverian)) at surface, covers 0.3 % of this area

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

Clough Quartzite - lower conglomerate and granofels (Lower Silurian) at surface, covers 0.3 % of this area

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

Biotite-quartz diorite gneiss of Vernon dome (Late Ordovician) at surface, covers 0.2 % 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.

Granodiorite to tonalite (Late Ordovician) at surface, covers 0.2 % of this area

Granodiorite to tonalite.

Partridge Formation, Interstratified metavolcanic rocks (Middle - Upper Ordovician) at surface, covers 0.2 % of this area

Chiefly amphibolites, found in southwestern New Hampshire.

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.

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.

Ammonoosuc Volcanics of Billings (1935) - metamorphosed andesitic and basaltic tuff, crystal tuff, and tuff breccia (Upper and Middle Ordovician) at surface, covers 0.1 % 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.

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

Locally fossiliferous in Whitefield quadrangle.

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.

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.

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.

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.