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Geologic units containing mafic volcanic rock

Earth material > Volcanic rock
Mafic volcanic rock
A solidified body of volcanic rock having abundant dark-colored minerals in its mode
Subtopics:
Trachybasalt
Basalt

California - Massachusetts - Maine - Minnesota - New Hampshire - New Mexico - Nevada - Oregon - Washington - Wisconsin
California
Mesozoic volcanic rocks, unit 2 (Western Sierra Foothills and Western Klamath Mountains) (Jurassic)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Mesozoic volcanic rocks, unit 4 (Peninsular Ranges) (Late Jurassic to Early Cretaceous)
Undivided Mesozoic volcanic and metavolcanic rocks. Andesite and rhyolite flow rocks, greenstone, volcanic breccia and other pyroclastic rocks; in part strongly metamorphosed. Includes volcanic rocks of Franciscan Complex: basaltic pillow lava, diabase, greenstone, and minor pyroclastic rocks
Paleozoic metavolcanic rocks, unit 1 (Eastern Klamath Mountains) (Devonian and Permian)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Paleozoic metavolcanic rocks, unit 3 (Northwestern Sierra Nevada) (Permian to Jurassic)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Paleozoic metavolcanic rocks, unit 5 (Mono Lake) (Triassic to Jurassic)
Undivided Paleozoic metavolcanic rocks. Mostly flows, breccia and tuff, including greenstone, diabase, and pillow lavas; minor interbedded sedimentary rocks
Triassic marine rocks, unit 4 (West Walker River) (Triassic(?))
Shale, conglomerate, limestone and dolomite, sandstone, slate, hornfels, quartzite; minor pyroclastic rocks
Undivided pre-Cenozoic metavolcanic rocks, unit 2 (undivided) (Paleozoic(?) to Mesozoic(?))
Undivided pre-Cenozoic metavolcanic rocks. Includes latite, dacite, tuff, and greenstone; commonly schistose.
Massachusetts
Felsic and mafic volcanic rocks (Proterozoic Z)
Felsic and mafic volcanic rocks - Southwest of Boston Basin.
Mattapan Volcanic Complex (Proterozoic Z or younger)
Mattapan Volcanic Complex - Rhyolite, melaphyre, agglomerate, and tuff. Mattapan Volcanic Complex is found in west and southwest part of Boston basin and beyond, and to the south in Blue Hills. Similar in lithology to Lynn Volcanic Complex. Both units consist largely of partly porphyritic rhyolite and rhyodacite flows, welded ash-flow tuffs, vitric tuff, lapilli tuff, lithic tuff, flow breccias, breccia pipes, and extrusion domes. Mattapan's rhyolite and rhyodacites are thinner and less varied in composition and texture than Lynn's, and volcanic breccias are absent in Lynn. Both units are reported to lie nonconformably on Dedham Granite and unnamed plutonic-volcanic complex of eastern MA; however, Mattapan has been observed as dikes and stocks cutting Dedham Granite (Billings, 1976; Kaye and Zartman, 1980; Chute, 1966), and other workers have pointed out evidence that some of Mattapan may be penecontemporaneous with younger phases of Dedham batholith. Westwood Granite may be intrusive equivalent of Mattapan. Mattapan is conformably and fairly continuously overlain by Roxbury Conglomerate of Boston Bay Group. LaForge (19832) cautioned against identifying rocks interbedded within Mattapan that look like Roxbury, but are still part of Mattapan. Metavolcanic rocks in Blue Hills resembling Mattapan are assigned to Mattapan on State bedrock map (Zen and others, 1983); for years they were considered to be either Silurian and Devonian, or Carboniferous; however, they are chemically and mineralogically distinct from Ordovician and Silurian Blue Hills [sic] Granite Porphyry. Author follows usage of Chute (1966) who could find no difference between volcanic rocks in Blue Hills area and Mattapan rocks, and thus these rocks are assigned to Mattapan. Proterozoic Z age is based on U-Th-Pb zircon date of 602 +/-3 Ma (Zartman, in Kaye and Zartman, 1980). Although Billings (1979) questions reliability of zircon ages from volcanic rocks, discovery of Proterozoic Z acritarchs in overlying Cambridge Argillite indicates zircon age is appropriate (Goldsmith, 1991).
Roxbury Conglomerate (Proterozoic Z to earliest Paleozoic)
Roxbury Conglomerate - Conglomerate, sandstone, siltstone, argillite, and melaphyre. Consists of Brookline, Dorchester, and Squantum Members. Roxbury Conglomerate forms base of Boston Bay Group. Divided into Brookline, Dorchester, and Squantum Members. Conglomerate in Brookline Member contains clasts of Dedham Granite, quartzite (possibly from Westboro Formation), and volcanic rock from underlying Mattapan Volcanic Complex. Dorchester Member consists of interbedded argillite and sandstone and forms an intermediate unit between Brookline Member and overlying Cambridge Argillite. Uppermost Squantum Member is a distinctive diamictite which appears to pinch out in northern part of basin. Brighton Melaphyre lies within Brookline Member and consists of mafic volcanic rocks (quartz keratophyre, keratophyre, and spilite). Roxbury clearly lies nonconformably on Dedham Granite near Hull, MA; can be traced continuously over Mattapan Volcanic Complex. Age is Proterozoic Z and possibly Early Cambrian (Goldsmith, 1991).
Roxbury Conglomerate (Proterozoic Z to earliest Paleozoic)
Roxbury Conglomerate - Melaphyre in the Roxbury Conglomerate. Brighton Melaphyre lies within Brookline Member and consists of mafic volcanic rocks (quartz keratophyre, keratophyre, and spilite). Roxbury clearly lies nonconformably on Dedham Granite near Hull, MA; can be traced continuously over Mattapan Volcanic Complex. Age is Proterozoic Z and possibly Early Cambrian (Goldsmith, 1991).
Wamsutta Formation (Middle and Lower Pennsylvanian)
Wamsutta Formation - Rhyolite and mafic volcanic rocks in the Wamsutta Formation. Wamsutta Formation occurs in Narragansett and Norfolk basins. Consists of conglomerate, lithic graywacke, sandstone, and shale. Also contains rhyolite and basalt horizons near Attleboro. Northwest of Attleboro, Wamsutta overlies Diamond Hill Felsite as used by Skehan and Murray (in Skehan and others, 1979). Volcanic rocks similar to Diamond Hill Felsite crop out west of Lake Pearl, between Franklin and Wrentham, on west flank of Norfolk basin. These are shown within Wamsutta Formation on MA State bedrock map of Zen and others (1983) because of their proximity to Diamond Hill. They also resemble Proterozoic Z Mattapan Volcanic Complex. Chute (1966) described lenses of carbonate rock in red and green shale in Wamsutta in Norwood quad. Limestone also observed in rocks mapped as Wamsutta adjacent to exposed Dedham Granite at Manchester Pond Reservoir (J.P. Schafer, 1982, oral commun.). Red and green shales may actually be Cambrian. Upper member of Pondville Conglomerate grades into and interfingers with Wamsutta; in turn, Wamsutta interfingers with Rhode Island Formation in northwest part of Narragansett basin. Nonconformably overlies Dedham Granite. Partly equivalent to Rhode Island Formation. Age is Early and Middle Pennsylvanian. Contains a few plant fossils (Goldsmith, 1991).
Maine
Cambrian unnamed mafic volcanic rocks (Cambrian)
Cambrian unnamed mafic volcanic rocks
Cretaceous mafic to felsic volcanic rocks (Cretaceous)
Cretaceous mafic to felsic volcanic rocks
Devonian Eastport Formation mafic to felsic volcanic member (Devonian)
Devonian Eastport Formation mafic to felsic volcanic member
Devonian Hedgehog Formation (Devonian)
Devonian Hedgehog Formation
Devonian - Silurian Castine Formation (Devonian - Silurian)
Devonian - Silurian Castine Formation
Devonian unnamed mafic volcanic rocks (Devonian)
Devonian unnamed mafic volcanic rocks
Mesozoic mafic to felsic volcanic rocks (Mesozoic)
Mesozoic mafic to felsic volcanic rocks
Ordovician Ammonoosuc Volcanics (Ordovician)
Ordovician Ammonoosuc Volcanics
Ordovician - Cambrian Cookson Formation mafic to felsic volcanic rocks (Ordovician - Cambrian)
Ordovician - Cambrian Cookson Formation mafic to felsic volcanic rocks
Ordovician - Cambrian unnamed volcanic rocks (Ordovician - Cambrian)
Ordovician - Cambrian unnamed volcanic rocks
Ordovician - Precambrian Z Columbia Falls Formation (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Columbia Falls Formation
Ordovician - Precambrian Z Cushing Formation mafic volcanic member (Ordovician - Precambrian Z)
Ordovician - Precambrian Z Cushing Formation mafic volcanic member
Ordovician unnamed mafic volcanic rocks (Ordovician)
Ordovician unnamed mafic volcanic rocks
Ordovician unnamed volcanic and sedimentary rocks (Ordovician)
Ordovician unnamed volcanic and sedimentary rocks
Ordovician unnamed volcanic rocks (Ordovician)
Ordovician unnamed volcanic rocks
Silurian Dennys Formation mafic to felsic volcanic rock member (Silurian)
Silurian Dennys Formation mafic to felsic volcanic rock member
Silurian Edmunds formation (Silurian)
Silurian Edmunds formation
Silurian Leighton Formation mafic to felsic volcanic rock member (Silurian)
Silurian Leighton Formation mafic to felsic volcanic rock member
Silurian - Ordovician Dunn Brook formation (Silurian - Ordovician)
Silurian - Ordovician Dunn Brook formation
Silurian - Ordovician unnamed volcanic rocks (Silurian - Ordovician)
Silurian - Ordovician unnamed volcanic rocks
Silurian Quoddy Formation mafic to felsic volcanic rock member (Silurian)
Silurian Quoddy Formation mafic to felsic volcanic rock member
Silurian unnamed volcanic and sedimentary rocks (Silurian)
Silurian unnamed volcanic and sedimentary rocks
Undifferentiated mafic to felsic volcanic rocks (Devonian - Ordovician)
Undifferentiated mafic to felsic volcanic rocks
Unnamed volcanic rocks (Devonian - Silurian)
Unnamed volcanic rocks
Minnesota
Unnamed schistose, volcanic, and hypabyssal rocks of mafic composition and volcanic, volcaniclastic, and intrusive rocks of felsic composition (Early Proterozoic)
Unnamed schistose, volcanic, and hypabyssal rocks of mafic composition and volcanic, volcaniclastic, and intrusive rocks of felsic composition - May be correlative with rocks of the Wisconsin magmatic terranes.
New Hampshire
Perry Mountain Formation, Volcanic facies in Piermont allochthon (Lower? - Middle? Silurian)
Perry Mountain Formation, Volcanic facies in Piermont allochthon.
New Mexico
andesite and basaltic andesite flows and associated volcaniclastic units (Phanerozoic | Cenozoic | Tertiary)
Lower Tertiary, (Lower Oligocene and Eocene) andesite and basaltic andesite flows, and associated volcaniclastic units. Includes Rubio Peak Formation, and andesite of Dry Leggett Canyon
andesites and basaltic andesites (Phanerozoic | Cenozoic | Tertiary)
Upper Oligocene andesites and basaltic andesites (26-29 Ma); includes La Jara Peak Basaltic Andesite, Uvas Basalt, the basaltic andesite of Poverty Creek, and Squirrel Springs Andesite, the Razorback, Bear Springs Canyon, Salt Creek, Gila Flat, and Middle Mountain Formations, and the Alum Mountain Group; locally includes more silicic flows
basaltic andesites (Phanerozoic | Cenozoic | Tertiary)
Lower Miocene and uppermost Oligocene basaltic andesites (22-26 Ma). Includes Bearwallow Mountain Andesite and basaltic andesite of Mangas Mountain
basalt or basaltic andesite (Phanerozoic | Cenozoic | Quaternary)
Basalt or basaltic andesite; middle and lower Pleistocene
Nevada
Horse Spring Formation (Late Oligocene to Middle Miocene)
HORSE SPRING FORMATION-Tuffaceous sedimentary rocks, southern Nevada
Tuffaceous sedimentary rocks (Late Eocene to Late Miocene)
TUFFACEOUS SEDIMENTARY ROCKS-Locally includes minor amounts of tuff
Oregon
Continental sedimentary rocks (upper and middle Miocene) (Middle Miocene to Late Miocene)
Poorly sorted and poorly bedded, fine- to coarse-grained tuffaceous siltstone, sandstone, pebble conglomerate, agglomerate, volcanic cobble conglomerate, air-fall tuff, and rare basaltic andesite flows equivalent to those in unit Tba. Included in the Miocene Sardine Formation by Peck and others (1964)
Ridge-capping basalt and basaltic andesite (Pliocene and upper Miocene) (Late Miocene to Pliocene)
Flows and flow breccia of basaltic andesite and lesser diktytaxitic to intergranular olivine basalt. Includes some dense, aphyric flows, commonly with either cryptocrystalline or pilotaxitic to trachytic texture, and porphyritic flows with phenocrysts and glomerocrysts of olivine, hypersthene, and labradorite. A few flows contain both hypersthene and calcic augite phenocrysts. Olivine mostly fresh or slightly altered to iddingsite in flows high in section; flows low in section show some alteration to clays (nontronite and saponite), secondary silica minerals, and calcite; pinkish-brown glass in some flows unaltered. Locally includes some andesite and dacite. Some flows of this unit are lithologically similar to flow rocks of the High Cascade volcanic sequence and some are more like flows that in the past have been mapped as part of the Sardine Formation (Peck and others, 1964) and Elk Lake Formation of McBirney and others (1974) and Sutter (1978). Potassium-argon ages of rocks from this unit range from about 4 to 8 or 9 Ma. Includes some rocks formerly mapped as Rhododendron Formation by Peck and others (1964)
Subaqueous pyroclastic ejecta of basaltic cinder cones (lower Pliocene? and Miocene?) (Miocene to Early Pliocene)
Deposits of bombs, breccia, and mafic to intermediate tuff; occurs as palagonitic tuff and breccia cones, rings, and ridges. In places interbedded with lacustrine sedimentary rocks
Washington
Upper upper Eocene nonmarine and marine rocks (Middle Eocene)
Massive to thin-bedded, feldspathic to arkosic sandstone, siltstone, shale, and carbonaceous shale; becomes mostly marine in the western foothills of Cascade Mountains where coal beds are abundant. Basaltic sandstone and siltstone in northern Olympic Peninsula.
Wisconsin
Volcanic rocks, undivided (Early Proterozoic)
Volcanic rocks, undivided - Mafic to felsic flows, pyroclastic rocks, impure quartzite, and conglomerate in Eau Claire River, Eau Claire and northern Clark Counties. Rhyolite has zircon ages of 1,858 +/- 5 Ma. Possibly correlative with Milladore Volcanic Complex.

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