FAULT ZONE · 2008. 2. 14. · t ex u r. C omp s dai nly fv gq z , c b io te. H r n ld, mu scv p ah...
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DRAFT IN REVIEW BLOODY BLUFF FAULT ZONE A A' Sap COf Sabg Sab Ong Zwb Sab Zwa Ssbh Os Sap Sap SOqd Ong Sab Ssbh Ona Si Zwa COf Zwba COf SOqt Sab Sap COf Zwbq Zwba Ssbh Sab Sab Sab Zwb SOqt Ssd Sap Ssb Jrd Sap SOqd Ssb Ona Ssbh SOqd Ssb Zwba SOqt Sab Sab Zwbq Ssbh Onh Oba Zwba SOqd Ssb Zwb SOqt Sap Ong Ssd Ssb Zwa Zwbq Ssd SOqt Zwbq Ssbh Sap Sab Ona SOqt Ong Jrd Sab Sap Ssd Oba Ssb SOqd Ssbh Ong Ssbh Zwba Ssbh Zwbq Zwba SOqd Sab Zwba Ssb Sap SOqd Sap Zwbq SOqt SOqd Sm Ong Sab Zwa Ssbh SOqd Sap SOqd SOqd SOqd Zwba Ssbh Sab Sap Ong 0 85 50 80 70 80 85 75 85 75 78 25 50 82 36 75 68 65 86 82 78 0 25 79 50 85 65 80 80 74 40 53 35 35 75 60 40 70 70 65 76 60 45 75 68 55 80 85 75 74 70 85 64 85 80 78 75 80 80 75 70 63 80 70 80 85 70 80 85 84 85 85 85 70 70 70 85 74 66 75 85 70 77 75 85 80 70 70 35 35 70 80 80 60 75 55 30 80 30 70 71 70 50 60 75 15 80 30 67 27 58 80 65 80 55 46 40 82 60 35 68 70 82 76 25 68 80 22 28 25 22 15 20 18 30 18 25 38 79 83 85 68 31 74 75 70 57 80 48 Sabg Sap Sab Ona Sap Ssbh COf Sap Ong Ong Sab Sab Sab Zwb Zwb Zwb Zwa Location approximate Lithologic Contacts Bedrock Exposure Individual Outcrop Areas of abundant outcrops or shallow bedrock (within 10 ft (3 m) of surface) Faults Contact, location generally approximate 32 32 47 50 50 Structural Symbols Strike and dip of dominant foliation / vertical foliation (includes mylonitic foliation). Compositional layering generally parallels foliation in stratified rocks Planar Features Linear Features Strike and dip of axial plane of minor fold Trend and plunge of mineral lineation Trend and plunge of minor fold axis EXPLANATION OF MAP SYMBOLS Only faults traceable at map-scale and on surface are shown Approximate strike and dip of heavily deformed foliation Mine or bedrock quarry. EXPLANATION OF LITHOLOGIC UNITS NASHOBA TERRANE Metasedimentary and Metavolcanic Rocks Nashoba Formation (Ordovician) Biotite gneiss facies--Chiefly medium-grained, foliated and layered, Ong light-gray paragneiss. Composed mainly of quartz, plagioclase and biotite, together with locally conspicuous muscovite. Commonly contains accessory garnet. Less prominent accessories include sillimanite, magnetite, ilmenite and apatite. Thin mica schist layers crop out locally, particularly in northern belt. Concordant lenses and discordant sheets of pegmatite occur in many exposures Amphibolite facies--Chiefly fine-grained, locally porphyroblastic, Ona distinctly foliated, dark-gray to black amphibolite. Composed mainly of hornblende and plagioclase. Epidote, magnetite and pyrite occur locally Hornblende gneiss facies--Fine- to coarse-grained glomeroporphyroblastic, Onh massive to slightly foliated, black to dark-gray gneiss. Composed chiefly of hornblende and plagioclase. Sphene and magnetite occur as prominent accessories Quartz-mica schist (Ordovician)--Chiefly fine- to medium-grained, Os prominently foliated and locally contorted, gray to silvery-white quartz-mica schist. Composed mainly of quartz, muscovite, plagioclase, and biotite. Commonly weathers to rusty-brown color. Similar to Brimfield Schist of Emerson (1917). Poorly exposed Boxford Formation (Ordovician)--Reduced in rank and included as Boxford "Member" of Nashoba Formation by Bell and Alvord (1976) A member--Chiefly fine- to medium-grained schist, gneiss and Oba amphibolite. Schist commonly bluish-gray and composed mainly of muscovite, biotite and quartz with minor amounts of andalusite and fibrolitic sillimanite. Gneissic rocks composed of quartz and plagioclase with varietal amounts of actinolite. Amphibolites in part coarser-grained than those of B member of Boxford Formation. Poorly exposed Fish Brook Gneiss (Cambrian to Ordovician)--Age about 499+6/-3 (U-Pb). COf Chiefly fine- to medium-grained, distinctly foliated, white to light-gray gneiss. Composed mainly of quartz, plagioclase and biotite. Contains minor amounts of epidote, muscovite, apatite and zircon. Potassium feldspar rare, but present locally. Contains numerous amphibolite inclusions. Progressively less biotitic and less distinctly foliated toward the south Intrusive Rocks Monzogranite at Middleton Pond (Probably Silurian)--Medium- to fine Sm grained, massive, pink to red monzogranite. Composed chiefly of microcline, plagioclase and quartz with varietal amounts of biotite almost completely altered to chlorite. Contains abundant xenoliths Andover Granite (Silurian )--Age about 450 ± 25 (Rb-Sr) to 412 ± 2 (U-Pb) Pegmatitic granite facies--Chiefly medium- to extremely coarse-grained, Sap massive, pearly-white to light-bluish-gray monzogranite and pegmatite. Composed mainly of microcline, plagioclase, quartz and muscovite. Biotite occurs locally and garnet is a common accessory. Broad areas underlain entirely by pegmatite Binary granite facies--Chiefly medium-grained, massive to faintly foliated, Sab pearly-white to light-gray monzogranite. Composed mainly of microcline, plagioclase, quartz, muscovite and biotite with accessory garnet. Pegmatite prominent locally Biotite granite-gneiss facies--Chiefly coarse-grained, slightly foliated Sabg very light-gray monzogranite-gneiss. Composed mainly of microcline, plagioclase, quartz, biotite and muscovite. Accessory garnet occurs commonly throughout this unit. Cross-cut locally by pegmatite dikes and quartz veins Sharpners Pond Diorite (Silurian )--Age about 430 ± 5 (U-Pb) Biotite tonalite facies--Chiefly medium- to fine-grained, massive to Ssb distinctly foliated, light- to medium-gray tonalite. Granodiorite and monzogranite occur locally. Composed mainly of plagioclase, quartz and biotite, together with lesser amounts of microcline and hornblende. Contains accessory amounts of magnetite, apatite and sphene Biotite-hornblende tonalite facies--Chiefly medium-grained, massive Ssbh to vaguely foliated, medium to dark-gray tonalite. Composed mainly of plagioclase, hornblende, quartz and biotite, together with accessory amounts of sphene, apatite and magnetite Hornblende diorite facies--Chiefly medium- to coarse-grained, massive, Ssd medium-gray to black diorite and tonalite. Composed mainly of plagioclase and hornblende, together with variable but generally small amounts of quartz. Biotite locally composes as much as 10 percent of the rock. Main accessories include magnetite, sphene and apatite MILFORD-DEDHAM (AVALONIAN) ZONE Metasedimentary and Metavolcanic Rocks Waltham Tectonic Melange (Late Proterozoic to Silurian(?))--Modified from LaForge (1932) B member--Chiefly fine-grained, foliated and locally layered, Zwb greenish-gray to black biotite-quartz-hornblende-plagioclase schists locally interlayered with ultra-fine-grained siliceous schists. The siliceous schists commonly are chloritic and epidotitic and crop out most conspicuously along the flanks of the Waltham Melange. Commonly mylonitic or sheared. Interlayered quartzite and quartz-feldspar gneiss occur locally. Transitional with A member Quartzite Facies of B member--Chiefly fine-grained, massive to Zwbq foliated, light-gray to white quartzite. Composed chiefly of quartz with minor amounts of chlorite and feldspar. Locally enriched with calc-silicate minerals. Mapped separately where quartzite is the predominant rock type Amphibolite facies of B member--Chiefly fine-grained, distinctly Zwba foliated and locally thinly layered, gray to black amphibolite and plagioclase amphibolite. Composed mainly of hornblende and plagioclase with lesser amounts of magnetite, chlorite and calcite. Epidote conspicuous locally. Mapped separately where amphibolite or plagioclase amphibolite is the predominant rock type A member--Chiefly medium- to coarse-grained foliated and Zwa layered, very light- to dark-gray gneiss. Commonly possesses an augen- or flaser-like texture. Composed mainly of varying amounts of quartz, plagioclase, microcline and biotite. Hornblende, muscovite, epidote and chlorite commonly present in small amounts. Contains some amphibolite and thin quartzite layers. Transitional with B member Intrusive Rocks Diabase (Early Jurassic)--Fine- to medium-grained, massive, dark-gray to black. Commonly porphyritic with tabular plagioclase phenocrysts up to 3 cm in diameter. Composed chiefly of plagioclase and pyroxene. Confined to Wilmington, Woburn, Reading, Lynnfield and Peabody areas Tonalite athwart Ipswich River at Middleton-Peabody town boundary Si (Silurian?)--Chiefly medium-grained, massive and locally foliated medium- to dark- greenish-gray tonalite. Composed mainly of plagioclase and quartz together with minor amounts of microcline. Abundant secondary chlorite and epidote. Intensely sheared and brecciated locally. Continuous with Newburyport (?) Quartz Diorite of Toulmin (1964) Diorite at Lake Quannapowitt and vicinity (Silurian or Ordovician)--Age about 444 ± 3 (U-Pb) Biotite-hornblende tonalite facies--Chiefly massive, medium-grained SOqt dark-gray, alkali-rich tonalite. Composed largely of plagioclase, hornblende, quartz and biotite Hornblende diorite facies--Chiefly massive, medium grained, gray to black, SOqd alkali-rich diorite. Composed mainly of plagioclase and hornblende, together with variable but generally small amounts of quartz and biotite. Accessories chiefly magnetite and sphene COf Jrd Oba Ona Ong Onh Os SOqd SOqt Sab Sabg Sap Si Sm Ssb Ssbh Ssd Zwa Zwb Zwba Zwbq OFFICE OF THE MASSACHUSETTS STATE GEOLOGIST UNIVERSITY OF MASSACHUSETTS Topographic base scanned from U.S. Geological Survey, 1966 Polyconic projection. 1927 North American Datum Digitally reprojected to 1983 North American Datum, 1:24,000 scale 10,000 foot grid ticks based on Massachusetts state plane coordinate system, mainland zone 1000-meter Universal Transverse Mercator grid ticks, zone19 Bedrock geology by R.O. Castle (1951-1952, 1992). Updated and revised by J.C. Hepburn and J.P. Kopera (2004). Digitized by J.P. Kopera (2005). Prepared in cooperation with the COMMONWEALTH OF MASSACHUSETTS STATE GEOLOGIST BEDROCK GEOLOGIC MAP WILMINGTON QUADRANGLE, MASSACHUSETTS v. 1.0 Stratigraphic correlation chart accompanies map This manuscript is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints for government use. This research was supported by U.S. Geological Survey, National Cooperative Geologic Mapping Program, under assistance Award No. 04HQAG0028. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. Citation: Castle, R.O, Hepburn, J.C., and Kopera, J.P., Bedrock geologic map of the Wilmington quadrangle, Massachusetts, v 1.0, Massachusetts Geologic Survey (4th), (in review, April 2005) Note: This manuscript is currently undergoing peer review, and is not a final version. Affiliations: 1 United States Geological Survey Menlo Park, CA 2 Department of Geology and Geophysics Boston College Chestnut Hill, MA, 02467 3 Corresponding Author: Office of the Massachusetts State Geologist Department of Geosciences University of Massachusetts, Amherst, MA 01003 [email protected] MAGNETIC NORTH APPROXIMATE MEAN DECLINATION, 1999 TRUE NORTH 15 / 1 2 QUADRANGLE LOCATION COf Zwa Ong Sap Sab Sab Ong SOqd SOqd Zwb Zwb Zwb SOqd Zwba Zwb Sap Sab SOqd Zwbq Sap Zwb Onh Zwb Zwbq 200 m -200 m -400 m -600 m sea level 500 ft sea level -500 ft -1000 ft -1500 ft -2000 ft A A' BLOODY BLUFF FAULT ZONE NASHOBA TERRANE MILFORD-DEHAM ZONE Route 128 Burlington Woburn Billerica Shawsheen River Burlington Folded amphibolite of the Nashoba Formation (Ona) Contorted layering characteristic of the biotite gneisses of the Nashoba Formation (Ong) Pegmatite veins crosscutting the Fish Brook gneiss. Note characteristic swirled foliation BEDROCK GEOLOGIC MAP OF THE WILMINGTON QUADRANGLE, MASSACHUSETTS By Robert O. Castle 1 , J. Christopher Hepburn 2 , and Joseph P. Kopera 3 2005 (in review)
Transcript of FAULT ZONE · 2008. 2. 14. · t ex u r. C omp s dai nly fv gq z , c b io te. H r n ld, mu scv p ah...
DRAFT IN REVIEW
BLOODY BLUFF FAULT ZONE
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Lithologic Contacts
Bedrock Exposure
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Structural Symbols
Strike and dip of dominant foliation / vertical foliation (includes mylonitic foliation). Compositional layering generally parallels foliation in stratified rocks
Planar Features
Linear Features
Strike and dip of axial plane of minor fold
Trend and plunge of mineral lineation
Trend and plunge of minor fold axis
EXPLANATION OF MAP SYMBOLS
Only faults traceable at map-scale and on surface are shown
Approximate strike and dip of heavily deformedfoliation
Mine or bedrock quarry.
EXPLANATION OF LITHOLOGIC UNITS
NASHOBA TERRANE
Metasedimentary and Metavolcanic Rocks
Nashoba Formation (Ordovician) Biotite gneiss facies--Chiefly medium-grained, foliated and layered, Ong light-gray paragneiss. Composed mainly of quartz, plagioclase and biotite, together with
locally conspicuous muscovite. Commonly contains accessory garnet. Less prominent accessories include sillimanite, magnetite, ilmenite and apatite. Thin mica schist layers crop out locally, particularly in northern belt. Concordant lenses and discordant sheets of pegmatite occur in many exposures
Amphibolite facies--Chiefly fine-grained, locally porphyroblastic, Ona distinctly foliated, dark-gray to black amphibolite. Composed mainly of hornblende and
plagioclase. Epidote, magnetite and pyrite occur locally Hornblende gneiss facies--Fine- to coarse-grained glomeroporphyroblastic,
Onh massive to slightly foliated, black to dark-gray gneiss. Composed chiefly of hornblende and plagioclase. Sphene and magnetite occur as prominent accessories
Quartz-mica schist (Ordovician)--Chiefly fine- to medium-grained, Os prominently foliated and locally contorted, gray to silvery-white quartz-mica schist.
Composed mainly of quartz, muscovite, plagioclase, and biotite. Commonly weathers to rusty-brown color. Similar to Brimfield Schist of Emerson (1917). Poorly exposed
Boxford Formation (Ordovician)--Reduced in rank and included as Boxford "Member" of
Nashoba Formation by Bell and Alvord (1976) A member--Chiefly fine- to medium-grained schist, gneiss and Oba amphibolite. Schist commonly bluish-gray and composed mainly of muscovite, biotite
and quartz with minor amounts of andalusite and fibrolitic sillimanite. Gneissic rocks composed of quartz and plagioclase with varietal amounts of actinolite. Amphibolites in part coarser-grained than those of B member of Boxford Formation. Poorly exposed
Fish Brook Gneiss (Cambrian to Ordovician)--Age about 499+6/-3 (U-Pb). COf Chiefly fine- to medium-grained, distinctly foliated, white to light-gray gneiss. Composed
mainly of quartz, plagioclase and biotite. Contains minor amounts of epidote, muscovite, apatite and zircon. Potassium feldspar rare, but present locally. Contains numerous amphibolite inclusions. Progressively less biotitic and less distinctly foliated toward the south
Intrusive Rocks
Monzogranite at Middleton Pond (Probably Silurian)--Medium- to fine Sm grained, massive, pink to red monzogranite. Composed chiefly of microcline, plagioclase and
quartz with varietal amounts of biotite almost completely altered to chlorite. Contains abundant xenoliths
Andover Granite (Silurian )--Age about 450 ± 25 (Rb-Sr) to 412 ± 2 (U-Pb) Pegmatitic granite facies--Chiefly medium- to extremely coarse-grained, Sap massive, pearly-white to light-bluish-gray monzogranite and pegmatite. Composed
mainly of microcline, plagioclase, quartz and muscovite. Biotite occurs locally and garnet is a common accessory. Broad areas underlain entirely by pegmatite
Binary granite facies--Chiefly medium-grained, massive to faintly foliated, Sab pearly-white to light-gray monzogranite. Composed mainly of microcline, plagioclase,
quartz, muscovite and biotite with accessory garnet. Pegmatite prominent locally Biotite granite-gneiss facies--Chiefly coarse-grained, slightly foliated Sabg very light-gray monzogranite-gneiss. Composed mainly of microcline, plagioclase,
quartz, biotite and muscovite. Accessory garnet occurs commonly throughout this unit. Cross-cut locally by pegmatite dikes and quartz veins
Sharpners Pond Diorite (Silurian )--Age about 430 ± 5 (U-Pb) Biotite tonalite facies--Chiefly medium- to fine-grained, massive to Ssb distinctly foliated, light- to medium-gray tonalite. Granodiorite and monzogranite occur
locally. Composed mainly of plagioclase, quartz and biotite, together with lesser amounts of microcline and hornblende. Contains accessory amounts of magnetite, apatite and sphene
Biotite-hornblende tonalite facies--Chiefly medium-grained, massive Ssbh to vaguely foliated, medium to dark-gray tonalite. Composed mainly of plagioclase,
hornblende, quartz and biotite, together with accessory amounts of sphene, apatite and magnetite
Hornblende diorite facies--Chiefly medium- to coarse-grained, massive, Ssd medium-gray to black diorite and tonalite. Composed mainly of plagioclase and
hornblende, together with variable but generally small amounts of quartz. Biotite locally composes as much as 10 percent of the rock. Main accessories include magnetite, sphene and apatite
MILFORD-DEDHAM (AVALONIAN) ZONE
Metasedimentary and Metavolcanic Rocks Waltham Tectonic Melange (Late Proterozoic to Silurian(?))--Modified from LaForge
(1932) B member--Chiefly fine-grained, foliated and locally layered, Zwb greenish-gray to black biotite-quartz-hornblende-plagioclase schists locally interlayered
with ultra-fine-grained siliceous schists. The siliceous schists commonly are chloritic and epidotitic and crop out most conspicuously along the flanks of the Waltham Melange. Commonly mylonitic or sheared. Interlayered quartzite and quartz-feldspar gneiss occur locally. Transitional with A member
Quartzite Facies of B member--Chiefly fine-grained, massive to Zwbq foliated, light-gray to white quartzite. Composed chiefly of quartz with minor amounts of
chlorite and feldspar. Locally enriched with calc-silicate minerals. Mapped separately where quartzite is the predominant rock type
Amphibolite facies of B member--Chiefly fine-grained, distinctly Zwba foliated and locally thinly layered, gray to black amphibolite and plagioclase amphibolite.
Composed mainly of hornblende and plagioclase with lesser amounts of magnetite, chlorite and calcite. Epidote conspicuous locally. Mapped separately where amphibolite or plagioclase amphibolite is the predominant rock type
A member--Chiefly medium- to coarse-grained foliated and Zwa layered, very light- to dark-gray gneiss. Commonly possesses an augen- or flaser-like
texture. Composed mainly of varying amounts of quartz, plagioclase, microcline and biotite. Hornblende, muscovite, epidote and chlorite commonly present in small amounts. Contains some amphibolite and thin quartzite layers. Transitional with B member
Intrusive Rocks
Diabase (Early Jurassic)--Fine- to medium-grained, massive, dark-gray to black. Commonly porphyritic with tabular plagioclase phenocrysts up to 3 cm in diameter. Composed chiefly of plagioclase and pyroxene. Confined to Wilmington, Woburn, Reading, Lynnfield and Peabody areas
Tonalite athwart Ipswich River at Middleton-Peabody town boundary Si (Silurian?)--Chiefly medium-grained, massive and locally foliated medium- to dark-
greenish-gray tonalite. Composed mainly of plagioclase and quartz together with minor amounts of microcline. Abundant secondary chlorite and epidote. Intensely sheared and brecciated locally. Continuous with Newburyport (?) Quartz Diorite of Toulmin (1964)
Diorite at Lake Quannapowitt and vicinity (Silurian or Ordovician)--Age about 444
± 3 (U-Pb) Biotite-hornblende tonalite facies--Chiefly massive, medium-grained SOqt dark-gray, alkali-rich tonalite. Composed largely of plagioclase, hornblende, quartz and
biotite Hornblende diorite facies--Chiefly massive, medium grained, gray to black, SOqd alkali-rich diorite. Composed mainly of plagioclase and hornblende, together with variable but generally small amounts of quartz and biotite. Accessories
chiefly magnetite and sphene
COf
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OFFICE OF THE MASSACHUSETTS STATE GEOLOGISTUNIVERSITY OF MASSACHUSETTS
Topographic base scanned from U.S. Geological Survey, 1966 Polyconic projection. 1927 North American DatumDigitally reprojected to 1983 North American Datum, 1:24,000 scale10,000 foot grid ticks based on Massachusetts state plane coordinate system, mainland zone1000-meter Universal Transverse Mercator grid ticks, zone19
Bedrock geology by R.O. Castle (1951-1952, 1992).Updated and revised by J.C. Hepburn and J.P. Kopera (2004). Digitized by J.P. Kopera (2005).
Prepared in cooperation with the COMMONWEALTH OF MASSACHUSETTS
STATE GEOLOGISTBEDROCK GEOLOGIC MAP
WILMINGTON QUADRANGLE, MASSACHUSETTSv. 1.0
Stratigraphic correlation chart accompanies map
This manuscript is submitted for publication with the understanding that the United States Government is authorized to reproduce and distribute reprints for government use.
This research was supported by U.S. Geological Survey, National Cooperative Geologic Mapping Program, under assistance Award No. 04HQAG0028. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
Citation:Castle, R.O, Hepburn, J.C., and Kopera, J.P., Bedrock geologic map of the Wilmington quadrangle, Massachusetts, v 1.0, Massachusetts Geologic Survey (4th), (in review, April 2005)
Note: This manuscript is currently undergoing peer review, and is not a final version.
Affiliations:
1United States Geological Survey Menlo Park, CA2Department of Geology and Geophysics Boston College Chestnut Hill, MA, 02467
3Corresponding Author: Office of the Massachusetts State Geologist Department of Geosciences University of Massachusetts, Amherst, MA 01003 [email protected]
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QUADRANGLE LOCATION
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ZwbqSap ZwbOnh Zwb Zwbq200 m
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Folded amphibolite of the Nashoba Formation (Ona)
Contorted layering characteristic of the biotite gneisses of the Nashoba Formation (Ong)
Pegmatite veins crosscutting the Fish Brook gneiss.Note characteristic swirled foliation
BEDROCK GEOLOGIC MAP OF THE WILMINGTON QUADRANGLE, MASSACHUSETTSBy
Robert O. Castle1, J. Christopher Hepburn2, and Joseph P. Kopera3
2005 (in review)
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