Bedrock Geologic Map of theT Marlborough …71 44 7 4 68 70 84 80 84 82 87 86 86 83 50 6 68 7 0 55...
1
Clinton- Newbury Fault I-395 I-495 NH-Maine Sequence (Merrimack Belt) Nashoba Terrane Avalon Terrane Narragansett Basin Location of quadrangle with respect to major geologic terranes of eastern Massachusetts Lake Char- Bloody Bluff Fault Zone Zone Rt. 3 I-90 I-495 Rt. 20 Rt. 1 Rt. 1 I-290 I-190 I-495 I-90 I-95 I-95 Rt 128 / I-95 I-93 NEO-PROTEROZOIC CAMBRIAN ORDOVICIAN SILURIAN DEVONIAN CARBONIFEROUS PERMIAN MESOZOIC CORRELATION OF MAP UNITS Westboro Formation Neo-Proterozoic intrusive rocks BLOODY BLUFF FAULT ZONE ? ? Sudbury Valley intrusive complex Indian Head Hill pluton Za Zwq Zws Zwa Zgdn Zmgru Zgbg Zgb DOsdp DOsgd DOsdf COmsg COm COms On COma COmfg COmfga COmfgm COmfgs DSap DSaqd Mig Sabf Didc Didf ? TrJd ASSABET RIVER--SPENCER BROOK AND ASSOCIATED FAULT ZONES ? Fault Fault Fault Andover granite Assabet quartz diorite Intrusive Rocks Stratified Rocks Granitic dikes and sills of uncertain affinity Alaskite NASHOBA TERRANE AVALON TERRANE Dgg ? Undifferentiated Milford and biotite poor granite 67 COm Zmgru DSap Zgb On DOsdp Zgb Zgb Zws Za Mig Zgb COma DOsgd COmfg Sabf Zgb Mig COm Didc Zgb Zgb COms Dgg+Mig DSaqd COmsg Za DOsgd Zgdn Didf DOsdf Dgg Zwq DSaqd Zgdn Zwq Zgdn Sabf Zws Sabf COms Zwq Mig Didc COmsg Zwq Zws Za Zwq Didf Zwq Zws Zgb Zws COms Zws Za Zws COmsg COma DSap COmfga DSap Didc Za Mig Zgb(?) COmfga Mig DSap Za COm Zwq Dgg(?) Zwa COmfg DOsgd COma DSap Zgbg Zgb Zwq DOsdf TrJd Zws COmfgs Mig TrJd TrJd DOsdp Mig DSaqdm Za Zna 40 75 35 30 5 45 45 45 35 45 65 50 45 40 30 25 80 ~80 85 70 75 89 40 35 65 30 ~35 70 65 85 20 38 80 70 54 71 44 74 68 70 84 80 84 82 87 86 86 83 50 66 68 70 55 40 40 80 75 13 70 80 80 33 84 64 85 85 62 82 55 40 24 30 55 72 60 67 80 35 55 75 82 85 37 65 58 74 75 70 55 45 57 60 63 75 80 70 85 45 15 40 55 70 65 78 77 55 68 52 70 56 65 60 57 55 42 35 22 32 55 24 55 46 33 37 40 35 35 32 33 30 36 34 40 80 38 50 68 55 20 65 85 60 40 85 52 85 87 43 80 55 67 64 80 10 65 83 83 85 80 29 80 45 65 75 80 30 45 48 51 60 68 70 16 54 55 28 60 60 35 45 35 38 80 33 48 65 47 50 46 45 10 32 42 52 62 29 23 30 40 55 23 26 85 68 53 34 68 55 45 58 69 49 50 52 40 47 70 55 64 84 50 59 32 41 47 34 54 32 48 56 47 54 62 35 54 48 85 66 34 43 68 52 37 43 64 30 46 30 30 42 68 34 32 13 47 23 65 56 44 41 54 70 45 77 52 73 23 77 80 71 74 73 57 55 72 75 80 42 76 76 23 85 72 75 64 78 65 42 81 82 59 66 37 70 48 78 57 14 66 40 58 56 54 75 81 51 47 72 56 31 40 55 40 40 55 80 53 50 70 48 55 35 25 32 45 30 40 36 45 60 40 30 36 33 55 46 40 41 36 36 46 38 26 36 34 32 40 50 35 80 60 65 53 36 80 39 38 52 46 75 28 32 28 40 15 38 25 45 30 58 28 87 48 82 87 50 70 80 89 45 65 83 17 32 58 66 63 45 57 67 66 42 80 60 76 45 52 84 38 35 40 52 35 30 52 50 17 47 35 39 34 45 33 34 35 30 70 48 46 70 45 36 29 32 40 40 30 34 31 33 60 87 64 8 40 25 8 12 42 30 59 45 65 35 75 80 80 65 72 60 67 72 54 65 75 75 47 82 78 33 35 47 62 45 61 50 54 65 60 50 70 28 24 85 40 80 25 78 89 75 46 43 55 65 30 57 50 22 21 46 50 63 74 82 37 54 34 38 33 23 36 28 29 45 63 35 55 70 62 47 72 63 45 47 42 67 32 55 38 56 42 46 45 24 54 54 72 33 78 74 64 64 62 63 75 28 84 61 43 47 74 47 37 37 47 87 75 55 70 45 75 77 37 42 30 33 44 75 58 49 47 39 39 52 42 35 82 65 35 52 40 58 48 25 58 37 65 55 65 50 44 52 24 53 28 27 40 68 47 62 86 58 66 79 24 60 52 40 34 42 42 29 24 38 56 55 48 28 18 34 59 40 61 47 46 60 42 22 60 70 15 64 8 7 6 9 4 9 9 9 40 45 32 20 10 28 40 12 90 23 28 28 47 33 32 25 49 66 31 10 34 33 45 19 24 11 24 17 27 14 10 18 25 14 5 50 24 6 7 7 30 62 10 11 25 40 22 14 20 13 9 8 50 53 70 17 58 18 48 80 14 34 18 12 42 65 15 11 25 36 45 20 42 26 28 25 33 14 37 45 30 73 80 46 COms ~60 TrJd Zgb Zmgru DSap COmsg DOsgd DOsdp COm COm COma DOsdp Za Zmgru Zmgru DSap METROWEST TUNNEL WACHUSETT- MARLBOROUGH TUNNEL ? ? ? Dgg NASHOBA TERRANE AVALON TERRANE Areas of abundant granitic dikes Area of abundant granitic dikes Area of abundant granitic dikes Zmgru sheared near contact with Za e e e e Approx. southe rn limit of du ctile deformation and brittle faults associated with Bloody Bluff Fault Zone App rox. northern l imit of major br ittle faults assoc iated with Bloody B luff Fault Zone BLOODY BLUFF FAULT ZONE BLOODY BLUFF / LAKE CHAR FAULT SPENCER BROOK FAULT ZONE ASSABET RIVER FAULT ZONE Zone of closely-spaced major brittle faults and mylonite exposed in Metrowest Tunnel Za AVALON TERRANE Paleozoic (?) Intrusive Rocks SUDBURY VALLEY INTRUSIVE COMPLEX (DEVONIAN TO ORDOVICIAN?) Locally sheared to biotite gneiss and chlorite schist within Bloody Bluff Fault Zone. Equivalent in part to Zv and Zdigb as mapped by Zen et al. (1983). Age inferred based on correlations with similar rocks to the northeast (Hon et al., 1993). DIORITE- Chiefly gray-weathering, mottled dark-gray to dark-greenish- gray, fine- to coarse-grained porphyritic quartz-microcline-biotite- hornblende-plagioclase±chlorite±epidote diorite to granodiorite (DOsdp; Photo 11). Characteristic plagioclase porphyroblasts up to 1 cm in diameter are abundant. Locally gneissic near margins with other units. A fine grained phase is present along the Sudbury Resevoir (DOsdf). GABBRODIORITE- Dark-gray-green to black, fine- to medium-grained plagioclase-hornblende±biotite gabbro or diorite with characteristic pink-weathering microcline megacrysts (Photo 12). Megacrysts locally occur in swarms which grade into xenoliths of granitic rock. Neo-Proterozoic Plutonic rocks Note: The Neo-Proterozoic plutonic rocks commonly contain small bodies of dark-greenish- gray, crumbly, fine-grained chloritized biotite amphibolite and biotite schist, up to 3 m in width intepreted to be altered mafic dikes or sills which are distinct from TrJd (Hepburn and DiNitto, 1978). ALASKITE (NEO-PROTEROZOIC?)- Beige- to to pink-weathering, light gray to pinkish-gray, fine-grained quartz-microcline-feldspar-±magnetite alaskite to aplite (Photo 10). Magnetite typically occurs as small dipyramids. Equivalent to the Hope-Valley Alaskite Gneiss as mapped by Walsh and Aleinikoff (in press) and Proterozoic Alaskite as mapped by Kopera et al. (2007), in part to Zhv as mapped by Zen et al. (1983), and the mafic-poor foliated Milford granite as mapped by Hepburn and DiNitto (1978). Age: 601 ± 7 Ma (SHRIMP/zircon; G. Walsh, written commun., 2006) for Zhg in the Grafton quadrangle. GRANODIORITE AT NOURSE FARM (NEO-PROTEROZOIC?) (after Markwort, 2006, in the Shrewsbury quadrangle)- Light- to medium-gray, medium- to coarse- grained plagioclase-feldspar hornblende±biotite±epidote granodiorite to diorite (Photo 14). Pods and masses of epidote are common. BIOTITE-GRANITE AND GRANITE-GNEISS (NEO-PROTEROZOIC?)- Light- pink-gray to light-pink, medium- to coarse-grained moderately to well-foliated - biotite-quartz-feldspar-microcline±magnetite granite to granodiorite (Photo 10). Rock typically contains 3-5% biotite, but locally 10% or more. Locally sheared to a biotite-magnetite gneiss (Zgbg). Partly equivalent to Zsg and Zpg as mapped by Walsh and Aleinikoff (in press) in the Grafton quadrangle, Zen et al., (1983), and the foliated Milford granite as mapped by Hepburn and DiNitto (1978). Age: 604 ± 5 Ma and 607 ± 5 Ma (SHRIMP/zircon; G. Walsh, written commun., 2006) for Zpg in Grafton quadrangle. UNDIFFERENTIATED MILFORD GRANITE AND BIOTITE-POOR GRANITE (NEO-PROTEROZOIC)- Light-pink-gray to gray medium- to coarse grained weakly to well-foliated quartz-feldspar-microcline±biotite±hornblende±magnetite granite and alaskite (Photo 13). Mafic minerals are typically found in trace amounts up to 1-3%. Biotite where present, commonly occurs in distinctive 0.5- to 1 cm-diameter clots. Magnetite commonly occurs in granular masses with biotite and hornblende, and locally as small dipyramids. Equivalent in part to Zhg as mapped by Zen et al., (1983), the Milford granite as mapped by Kopera et al. (2007), and phases of the Milford granite as mapped by Hepburn and DiNitto (1978). Late, fine-grained aplitic dikes are common. Age: 633 ± 9 Ma and 601 ± 7 Ma (SHRIMP/zircon; G. Walsh, written commun., 2006) for Zhg in the Grafton quadrangle. Approximately 606 Ma (206Pb/238U) for the Milford granite in the Holliston quadrangle (M. Thompson, written commun., 2007). Stratified Rocks Stratified rocks of the Avalon terrane have been metamorphosed under conditions of the greenschist and lower amphibolite facies. WESTBORO FORMATION (NEO-PROTEROZOIC OR YOUNGER?) QUARTZITE- Chiefly light- to dark-gray, tan, or pink-gray, fine-grained, well-bedded to massive feldspathic to pure quartzite (Photo 15). Interbeds of micaceous quartzite and quartz-mica schist are common. Light-green, fine- to medium-grained actinolite-carbonate calc-silicate granulites, light-purplish-brown fine-grained biotite granulites, or calc- silicate-bearing quartzites are common as thin layers, pods, or lenses within the quartzite. Interbeds of Zws are common. SCHIST AND GREENSTONE- Rusty weathering, dark-gray, fine- to medium-grained biotite-quartz-feldspar schist and phyllite, light-gray fine- to medium-grained muscovite-quartz schist, dark-green fine- to medium-grained chlorite schist and phyllite, and dark-bluish-gray to dark-green fine-grained chlorite-epidote greenstone with isolated pods and lenses of quartzite. Interlayers of light- to medium-gray weathering, dark-gray to dark-gray-green hornblende- plagioclase±biotite±epidote amphibolite, amphibolite gneiss, or EXPLANATION OF SYMBOLS Location of cited photo shown below Exposure Bedrock outcrop examined in field Area of abundant outcrop or shallow bedrock (within 10 feet of surface) Well or geotechnical boring used to constrain bedrock lithology in areas of poor bedrock exposure. Data obtained from Duncan and Mabee (2004), and unpublished data by D. Ashenden (written commun., 2004) Alignment of subsurface tunnel data used in construction of map Planar Features (placed over location measured. Where many symbols present placed as close to outcrop as possible) Strike and dip of foliaton and vertical foliation in all rocks, composite S 1 foliation in the Marlborough formation, composite S 1 or later foliation in the Nashoba formation, and foliation of undetermined age in plutonic rocks. In all layered rocks foliation is dominantly parallel to bedding and/or compositional layering. Approximate strike and dip of heavily contorted foliation Strike and dip of secondary foliation and crenulation cleavage (S 2 ) in Marlboro Formation. This foliation generally parallels the axial surfaces of F 2 folds and cuts the S 1 foliation. Strike and dip of axial surface of secondary fold (F 2 ) of S 1 foliation in the Nashoba terrane (Photo 1), or fold of undetermined age in Avalon Terrane. Mylonitic fabric and/or shear fabric of undetermined age Fracture cleavage of undetermined age Brittle fault observed in outcrop or tunnel interpreted to be significant at map scale. For additional outcrop-scale brittle structure information, see Mabee and Salamoff (2006). Linear Features Trend and plunge of mineral lineation of undetermined age Trend and plunge of axis of secondary fold (F 2 ) of S 1 foliation in the Nashoba terrane, or fold of undetermined age in the Avalon terrane EXPLANATION OF LINES Contact-- Accuracy of location indicated by proximity to bedrock exposures. Contacts between units within the Marlboro Formation and Neo-Proterozoic plutonic rocks are generally gradational. Trace of discrete shear zone or sheared contact. Queried in Nashoba terrane where relations to Andover granite are unknown. Zone of sheared and cataclastic rocks (e.g. Photo 16) Trace of brittle fault. Approximate dip shown where exposed in subsurface tunnel and/or outcrop. Only the traces of faults that can be supported by unequivocal field evidence are shown. Trace of axial surface of map-scale F 2 or later antiform showing plunge of axis, where estimated. Dashed where existence inferred. DOsdp DOsgd Zgdn Zmgru Zwq Zws 30 30 30 30 30 30 30 30 30 ~60 DOsdf Zgbg Zgb Zwa CITED REFERENCES Arvin, T., 2006, Bedrock geology of the Maynard quadrangle, Massachusetts [Master's Thesis]: Chestnut Hill, Ma, Boston College. Acaster, M., and Bickford, M.E., 1999, Geochronology and geochemistry of Putnam-Nashoba Terrane metavolcanic and plutonic rocks, eastern Massachusetts; constraints on the early Paleozoic evolution of eastern North America: Geological Society of America Bulletin, v. 111, p. 240- 253. Castle, R.O., Hepburn, J.C., and Kopera, J.P., (in press), Bedrock geologic map of the Lawrence quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-01. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database. Castle, R.O., Hepburn, J.C., and Kopera, J.P., (in press), Bedrock geologic map of the South Groveland quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-02. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database. Castle, R.O., Hepburn, J.C., and Kopera, J.P., (in press), Bedrock geologic map of the Wilmington quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-03. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database. DiNitto, R.G., 1983, The Bedrock Geology of the Marlborough Area, Massachusetts [Masters thesis]: Chestnut Hill, Ma, Boston College. Duncan, C., and Mabee, S.B., 2004, Well Inventory of the Marlborough quadrangle, Massachusetts, Office of the Massachusetts State Geologist Well Inventory 04-01. ESRI ArcView Database. GZA GeoEnvironmental Inc., Jacobs Associates, and Sverdup Civil Inc., 2005, Geotechnical Data Report, Metrowest Water Supply Tunnel, Construction Packages 1, 2 and 3: Massachusetts Water Resource Authority Contracts 6054, 6055, and 6059. Volumes I and II. Handford, L.S., and Staff, 1965, Rb-Sr whole-rock age study of the Andover and Chelmsford granites, Massachusetts: Massachusetts Institute of Technology, Department of Geology and Geophysics, 13th Annual Report to the U.S. Atomic Energy Commission, Contract AT(30-1)-1381, p. 11-14. Hansen, W.R., 1956, Geology and mineral resources of the Hudson and Maynard quadrangles, Massachusetts: U. S.G.S. Bulletin 1038. Hatch, N.L., Jr., editor, 1991, The bedrock geology of Massachusetts, U. S. Geological Survey Professional Paper 1366. Hepburn, J.C., 1978, Preliminary reconnaissance bedrock geologic map of the Shrewsbury Quadrangle, Worcester County, Massachusetts: U.S.G.S. Open File Report 78-951. Hepburn, J.C., and DiNitto, R.G., 1978, Preliminary bedrock geologic map of the Marlborough Quadrangle, Middlesex and Worcester counties, Massachusetts: U.S.G.S. Open File Report 78-222. Hepburn, J.C., Dunning, G.R., and Hon, R., 1995, Geochronology and regional tectonic implications of Silurian deformation in the Nashoba Terrane, southeastern New England, U.S.A: Geological Association of Canada Special Paper, v. 41, p. 349-365. Hill, M.D., Hepburn, J.C., Collins, R.D., and Hon, R., 1984, Igneous rocks of the Nashoba Block, eastern Massachusetts in Hanson, Lindley S. [editor] Geology of the Coastal Lowlands; Boston, MA to Kennebunk, ME: Salem State College, Dept. of Geological Sciences, Salem, MA. New England Intercollegiate Geological Conference Guidebook v. 76, p. 61-80. Hon, R., Paige, M.L., and Loftenius, C.J., 1993, Petrogenesis of two diverse mid-Paleozoic complexes of eastern Massachusetts; A-type Cape Ann Granite and I-type Sharpners Pond Quartz Diorite in Cheney, John T. and Hepburn, J. Christopher [editors], Field trip guidebook for the northeastern United States; 1993 Boston GSA: University of Massachusetts, Amherst, Dept. of Geosciences Contribution n. 67, p. Q1-Q28. Kopera J.P., Shaw C.E. Jr.,,and Fernandez, M., 2007, Preliminary bedrock geologic map of the Milford quadrangle, Massachusetts: Office of the Massachusetts State Geologist Open File Report 07-01. Scale 1:24,000. 4 sheets and digital product: Adobe PDF and ESRI ArcGIS database. Mabee, S.B. and S. Salamoff, 2006, Fracture characterization map of the Marlborough quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-01. Scale 1:24,000. 5 sheets and digital product: Adobe PDF and ESRI ArcGIS database. Markwort, R., 2006, Bedrock geology of the Shrewsbury quadrangle, Massachusetts [Master's Thesis]: Chestnut Hill, MA, Boston College. Skehan, J.W., and Abu-Moustafa, A.A., 1976, Stratigraphic analysis of rocks exposed in the Wachusett-Marlborough Tunnel, East-central Massachusetts in Contributions to the stratigraphy of New England: Geological Society of America Memoir n. 148, p. 217-240. Walsh, G.J., and Aleinikoff, J.N., in press Bedrock Geologic Map of the Grafton Quadrangle, Worcester County, Massachusetts: U.S. Geological Survey Scientific Investigations Map. 2 Sheets. Zartman, R.E., and Naylor, R.S., 1984, Structural implications of some radiometric ages of igneous rocks in southeastern New England: Geological Society of America Bulletin, v. 95, p. 522-539. Zen, E.A., Goldsmith, R., Ratcliffe, N.M., Robinson, P., Stanley, R.S., Hatch, N.L., Jr., Shride, A.F., Weed, E.G.A., and Wones, D.R., 1983, Bedrock geologic map of Massachusetts: U.S.G.S., Scale 1:250,000 DSap DSaqd Mig Sabf TrJd EXPLANATION OF UNITS DIABASE- Dark gray fine- to medium-grained, locally porphyritic diabase, occuring as north to northeast trending 10 cm- to 3 meter-thick dikes and dike swarms (Photo 2). NASHOBA TERRANE Intrusive Rocks INDIAN HEAD HILL PLUTON GRANITE (MISSISSIPIAN)- Chiefly light-gray- to buff-weathering, light-gray to gray, fine- to medium-grained massive biotite-quarts- microcline-plagioclase granite, locally varying from granodiorite to quartz monzonite (Photo 3). Locally exhibits weak foliation. Age: 349±4 Ma (U-Pb/zircon, titanite; Hepburn et al., 1995). DIORITE (DEVONIAN?)- Chiefly medium-gray weathering, mottled dark-gray, coarse-grained biotite-hornblende-plagioclase ±quartz ±orthoclase diorite and granodiorite (Didc; Photo 3) locally grading into dark-gray, fine- to medium-grained diorite (Didf). Age: 402±5 Ma for Didc (Rb-Sr/whole-rock; Hill et al., 1984) GRANITE-GNEISS (DEVONIAN OR OLDER?)- Buff- to pink- weathering, fine-to-medium grained, moderately to well-foliated biotite-quartz-feldspar granite gneiss with locally distinct schlieren-like compositional segregations (Photo 7). Interfolded with Marlboro Formation. Overhatching indicates areas where extensively intruded by Mig. In part equivalent to Grafton granite in Grafton quadrangle (518 ± 5 Ma; SHRIMP/zircon; G. Walsh, written commun., 2006). ASSABET QUARTZ DIORITE (SILURIAN TO DEVONIAN?)- Medium- to dark- gray weathering, dark-gray, medium- to coarse-grained, quartz-biotite-plagioclase- hornblende±magnetite±garnet±pyrite diorite. Locally contains thin layers of rusty-weathering, silliminite-biotite-muscovite±garnet schist. Locally sheared to a biotite-pyrite schist (Photo 4), mylonite (DSaqdm), and/or faulted to a carbonate- sulfide breccia. Formerly mapped as the Straw Hollow diorite by Hepburn and DiNitto (1978), and DiNitto (1983). Possibly correlative with Sharpner's Pond pluton to northeast. Age: 430±5 (U-Pb/zircon from Sharpner's Pond diorite; Zartman and Naylor, 1984); 385± 10 Ma (U-Pb and Pb-Pb/zircon; Acaster and Bickford, 1999) ANDOVER GRANITE PEGMATITIC GRANITE (DEVONIAN TO SILURIAN?)- Buff- to pinkish-weathering, light- to medium-gray, coarse-grained to pegmatitic muscovite-biotite-placgioclase-microcline-quartz±garnet granite, granodiorite, and quartz monzonite (Photo 5). Generally displays a coarse gneissic foliation. Age: 412±2 Ma (U-Pb/zircon; Hepburn et al., 1995); 408±22 Ma (Rb-Sr/whole rock; Zartman and Naylor, 1984), 415 Ma (Rb-Sr/whole rock; Hill et al., 1984). FOLIATED BINARY GRANITE (SILURIAN TO ORDOVICIAN?)- Buff- weathering, light- to medium-gray, well to moderately foliated, medium- to coarse-grained quartz-microcline-plagioclase-biotite- muscovite granite to quartz-monzonite gneiss (Photo 6). Locally fine- to medium-grained. Locally contains xenoliths of amphibolite. Correlation with Andover granite in type locality uncertain Age: 446±32 (Rb-Sr/whole rock; Zartman and Naylor, 1984); 450±23 (Rb-Sr/whole rock; Handford et al., 1965). Areas of abundant granitic dikes and sills of undetermined age and affinity. Includes probable dikes and sills of Mig and Dgg. Didc Didf COmsg COm COms On Stratified Rocks Stratified rocks in the Nashoba terrane have been metamorphosed under conditions of the mid- to upper amphibolite facies. NASHOBA FORMATION (ORDOVICIAN OR OLDER?)- Chiefly medium- to dark- gray, fine- to coarse-grained, quartz-plagioclase biotite±microcline±silliminite ±garnet gneiss (Photo 8), with subsidiary interlayers of amphibolite, calc-silicate, marble, quartzite, granulite, and biotite-muscovite-silliminite±garnet schist. Locally migmatitic. Contains abundant dioritic to granitic dikes and sills. The Nashoba Formation is poorly exposed in the Marlborough quadrangle. MARLBORO FORMATION (CAMBRIAN TO ORDOVICIAN OR OLDER?)- FELSIC GRANULITE AT MILLHAM RESERVOIR- Light-gray- to tan-weathering, medium- to dark-gray, massive to moderately foliated, homogeneous, fine- to medium-grained, muscovite-biotite-plagioclase-quartz granulite (Photo 9). Gray- white feldspar porphyroclasts locally give rock charcteristic “mottled” appearance. Also included are lenses of rusty-weathering, fine-grained silliminite-biotite- muscovite schist (COmfgs), a light-gray weathering lineated coarse-grained biotite- plagioclase-hornblende amphibolite with distinctive pods of granite and granodiorite (COmfga). AMPHIBOLITE AND SCHIST- Interlayered rusty-weathering, black to dark-gray, fine-to coarse-grained quartz-plagioclase-muscovite-biotite±silliminite±garnet schist (COms) and light- to medium-gray weathering, black to dark-gray hornblende-plagioclase-biotite-quartz amphibolite (COma). Garnet and silliminite occur locally as thin layers within the schist. Thin layers of light-gray- to buff- to rusty-weathering, dark gray biotite-muscovite-plagioclase-quartz granulite and calc- silicate also occur locally. SCHIST AND GRANULITE- Light-gray-weathering, fine- to medium-grained biotite-muscovite-quartz-plagioclase±hornblende±garnet granulite interlayered with rusty- to silvery-white-weathering, silvery to dark brown to dark-gray, fine- grained quartz-plagioclase-muscovite-biotite±garnet schist (Photo 1, Photo 7), with local interlayers of amphibolite. Garnet coticule and calc-silicate layers locally present. UNIDFFERIENTIATED AMPHIBOLITE AND OTHER ROCKS- Chiefly dark to light gray-weathering, locally rusty weathering, black, fine- to medium-grained epidote-quartz-biotite-plagioclase-hornblende amphibolite. Locally interlayered with dark-gray to black, fine-grained quartz-muscovite-plagioclase-biotite ±hornblende±garnet schists; light gray to beige granulites, fine-grained, granulitic quartz-muscovite-biotite-plagioclase±hornblende calc-silicates; and dark-gray, medium- to coarse-grained biotite-plagioclase-quartz gneisses and schists. Epidote and calc-silicate occurs locally as thin layers, boudins, and knots ranging from 5 cm to 1 m in length (Photo 2, Photo 7). Two- to five cm-thick stringers of plagioclase and quartz commonly occur parallel to foliation. Locally migmatitic along the Bloody Bluff Fault and near mappable bodies of Cgg. Mostly equivalent to the Sandy Pond Amphibolite of Hepburn and DiNitto (1978) and DiNitto (1983). Outcrop where layers of epidote are abundant in Marlboro Formation COma COmfg COmfga COmfgs 10 Dgg DSaqdm ~10-20 e ~10-20 ~80-89 A A' MASS. QUADRANGLE LOCATION Topographic base modified from U.S. Geological Survey, 1969 Polyconic projection. Reprojected to 1983 North American Datum. 10,000 foot grid ticks based on Massachusetts state plane coordinate system, mainland zone, 1927 North American Datum 1000-meter Universal Transverse Mercator grid ticks from 1927 North American Datum, zone 19 Hydrography from MassGIS (http://www.mass.gov/mgis) Data Sources: -Fieldwork by J. P. Kopera (2003-2006), assisted by A. Koenigsberg (2005) -Hepburn and DiNitto, 1978 (USGS Open File Report 78-222) -DiNitto, 1983 (M.S. Thesis, Boston College) -Unpublished data by D. Ashenden (written commun., 2004) -Skehan and Abu-Moustafa, 1976 (Wachusett-Marlborough Tunnel) -Unpublished data by Hager Geoscience (written commun., 2006; Metrowest Tunnel) -Duncan and Mabee, 2004 (borehole data) -GZA GeoEnvironmental, Inc., et al., 2005 (Metrowest Tunnel) -Digital cartography and editing by J.P. Kopera (2006, 2008) MAGNETIC NORTH APPROXIMATE MEAN DECLINATION, 1999 TRUE NORTH 15 / 1 2 OMSG Geologic Map No. 06-01 Bedrock Geology Marlborough Quadrangle 2006 Map last modified 3/13/08 Comments to the Map User A geologic map displays information on the distribution, nature, orientation and age relationships of rock and deposits and the occurrence of structural features. Geologic and fault contacts are irregular surfaces that form boundaries between different types or ages of units. Data depicted on this geologic quadrangle map are based on reconnaissance field geologic mapping, compilation of published and unpublished work, and photogeologic interpretation. Locations of contacts are not surveyed, but are plotted by interpretation of the position of a given contact onto a topographic base map; therefore, the accuracy of contact locations depends on the scale of mapping and the interpretation of the geologist(s). Any enlargement of this map could cause misunderstanding in the detail of mapping and may result in erroneous interpretations. Site-specific conditions should be verified by detailed surface mapping or subsurface exploration. Topographic and cultural changes associated with recent development may not be shown. We recommend reading Reading Maps with a Critical Eye: Becoming an Informed Map Reader by the Maine Geologic Survey (http://www.maine.gov/doc/nrimc/mgs/mapuse/informed/informed.htm), to make the best use of a geologic map. Cross sections are constructed based upon the interpretations of the authors made from geologic mapping, and available geophysical and subsurface (drillhole) data. Cross sections should be used as an aid to understanding the general geologic framework of the map area, and not be the sole source of information for use in locating or designing wells, buildings, roads, or other man-made structures. This research was supported by U.S. Geological Survey, National Cooperative Geologic Mapping Program, under assistance Award No. 03HQAG0067 and an NSF REU Grant to the Association of American State Geologists. The authors wish to thank Gregory J. Walsh, David Ashenden, and Patrick J. Barosh for thoughtful and thorough reviews. Citation: Kopera J., Hepburn J.C., and DiNitto R., 2006, Bedrock geologic map of the Marlborough quadrangle, Massachusetts: Office of the Massachusetts State Geologist Geologic Map 06-01. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database. This map was produced on request directly from digital files (PDF format) on an electronic plotter. A digital copy of this map (PDF format), including GIS datalayers, is available at http://www.geo.umass.edu/stategeologist Author Affiliations: 1 Corresponding Author: Office of the Massachusetts State Geologist E-mail: [email protected] 2 Department of Geology and Geophysics, Boston College, Chestnut Hill, MA 02467 3 Sleeman, Hanley, & DiNitto, 50 Congress St, Boston, MA 02109 Bedrock Geologic Map of the Marlborough Quadrangle, Massachusetts by: Joseph P. Kopera 1 , J. Christopher Hepburn 2 , and Richard G. DiNitto 3 O F F I C E O F T H E S T A T E G E O L O G I S T U N I V E R S I T Y O F M A S S A C H U S E T T S Office of the Massachusetts State Geologist University of Massachusetts, Amherst Address: 269 Morrill Science Center, 611 North Pleasant Street, Amherst, MA 01003 Phone: 413-545-4814 E-mail: [email protected] WWW: http://www.geo.umass.edu/stategeologist Photo 1. Compositional layering and parallel foliation (S 1 ) defining F 2 folds about S 2 in the schist and granulite member (COmsg) of the Marlboro Formation. S 2 S 1 Photo 2. A Mesozoic diabse dike (TrJd) cross- cutting compositional layering in the Marlboro Formation (COm). The light green streaks are layers of epidote and are common in the Marlboro Formation. TrJd COm Photo 3. Coarse-grained granite (Mig) intruding well-foliated, coarse-grained diorite (Didc) of the Indian Head Hill Pluton. The fine-grained black layers in the diorite are xenoliths of amphibolite of the Marlboro Formation (COm) Mig Didc COm Photo 4. A shear zone cross-cutting the Assabet quartz diorite (DSaqd) near the Assabet River fault zone. Quartz veins that were stretched into boudins form the white blebs in the photograph. A dike of sheared Andover granite (DSap) is shown near the top of the photograph. DSaqd Shear Zone DSap Photo 5. A pavement outcrop of the pegmatitic phase of the Andover granite (DSap). The granite is a heterogeneous mix of pegmatite and finer- grained granite, and exhibits a weak gneissic foliation parallel to regional foliation. Photograph taken in southeasternmost portion of the Hudson quadrangle, approximately .5 miles west of intersection of Hudson Rd. and Broad St., in the town of Marlborough. Photo 6. Foliated binary Andover Granite (Sabf). Streaks of biotite and muscovite locally define the foliation. Photograph taken from the Hudson quadrangle at intersection of Marlboro St. and Reed Rd. in the town of Hudson. Photo 7. Dike of granite gneiss of the Indian Head Hill pluton(Dgg) cross-cutting foliation of the schist and granulite of the Marlboro Formation (COmsg). A phase of regional deformation post-dated the intrusion of the granite-gneiss, resulting in folded (F 2 ) intrusive contacts. Dgg COmsg Photo 8. Sheared and folded migmatitic gneiss of the Nashoba formation (On). Photo taken in Hudson quadrangle, approximately 50 meters north of intersection of Crescent St. and Hartley Rd. in Stowe center. Photo 9. Felsic granulite at Milham Resevoir (COmfg). Foliation is defined by layers of white-weathering felspar porhyroclasts. The entire unit is intensley sheared by the Assabet River fault zone. Photo 10. Fine-grained alaskite (Za) intruding foliated coarse-grained Neo-Proterozoic biotite-granite (Zbg). Photo 11. Porphyritic diorite (DOsdp) of the Sudbury Valley intrusive complex. The white-weathering plagioclase phenocrysts are characteristic of this unit. Photo 12. Gabbrodiorite (DOsgd) of the Sudbury Valley Intrusive complex with a xenolith of Neo- Proterozoic granite. The contacts between the xenoliths and gabbrodiorite are commonly gradational, and are characterized by bright pink-weathering feldspars in a gabbro-diorite matrix. The green epidote vein cross-cutting the contact is related to motion along the Bloody Bluff Fault zone just to the north of the outcrop. Photo taken in the Framingham quadrangle, approximately 0.25 miles east of the intersection of Broad Meadow St. with the boundary between the Marlborough and Framingham quadrangles. DOsgd Granite xenolith Photo 13. Undifferentiated Milford granite and biotite-poor granite (Zmgru) with trace mafic minerals. Photo 14. Granodiorite at Nourse Farm (Zgdn). Zgdn characteristially contains pods and masses of epidote, as shown in the above photograph. Photo 15. Sheared quartzite (Zwq) of the Westborough formation. Shearing has obliterated bedding at this outcrop and has formed finely laminated foliation planes on which the pencil is resting. Photo 16. Sheared and altered granite within the Bloody Bluff fault zone. 1 2 3 4 7 9 10 11 13 14 15 16 Zna Zbg Zone of intense shearing and cataclasis Sheared and altered granite Epidote Zwq Zhg PZa Zws Zgb DOsdp Mig Cgg TrJd COmsg COma On COmfg SEA LEVE L 500 -1500 ft 1500 ft 1000 500 1000 SEA LEVE L 500 -500 -1000 BEND IN SECTION East Main Street Penn. Central RR Hayes Memorial Drive Wachusett-Marlborough Tunnel A A' Massachusetts Turnpike Sudbury River Cedar Swamp Route 9 Newton's Hill Walnut Hill (Drumlin) Wachusett Aqueduct I-290 Assabet River -1500 ft 1500 ft 1000 COm BLOODY BLUFF FAULT ZONE ASSABET RIVER FAULT ZONE Brittle faults observed in tunnel Mig }
Transcript of Bedrock Geologic Map of theT Marlborough …71 44 7 4 68 70 84 80 84 82 87 86 86 83 50 6 68 7 0 55...
Clinto
n-N
ewbu
ry
Fault
I-395
I-495
NH-Maine Sequence(Merrimack Belt)
Nasho
ba Terr
ane
Avalon Terra
ne
Narragansett Basin
Location of quadrangle with respect to major geologic terranes of eastern Massachusetts
Lake C
har-
Bloody BluffFa
ult
Zone
Zone
Rt. 3
I-90
I-495
Rt. 2
0
Rt. 1
Rt. 1
I-290
I-190
I-495
I-90
I-95
I-95
Rt 1
28 /
I-95
I-93
NE
O-P
RO
TER
OZO
ICC
AM
BR
IAN
OR
DO
VIC
IAN
SIL
UR
IAN
DE
VO
NIA
NC
AR
BO
NIF
ER
OU
SP
ER
MIA
NM
ES
OZO
IC
CORRELATION OF MAP UNITS
Westboro Formation
Neo-Proterozoic intrusive rocks
BLO
OD
Y B
LUFF FA
ULT ZO
NE
?
?
Sudbury Valleyintrusive complex
Indian Head Hillpluton
Za
ZwqZws
ZwaZgdn
Zmgru
ZgbgZgb
DOsdpDOsgd
DOsdf
COmsgCOm
COms
On
COma
COmfgCOmfga
COmfgm
COmfgs
DSapDSaqd
Mig
Sabf
Didc Didf
?
TrJd
AS
SAB
ET R
IVE
R--S
PEN
CE
R B
RO
OK
AN
D A
SS
OC
IATE
D FA
ULT ZO
NE
S
?
Fault
Fault
Fault
Andovergranite
Assabetquartz diorite
Intrusive Rocks
Stratified Rocks
Granitic dikes and sillsof uncertain affinity
Alaskite
NASHOBATERRANE
AVALONTERRANE
Dgg
?
Undifferentiated Milford and biotite poor granite
67
COm
Zmgru
DSap
Zgb
On
DOsdp
Zgb
Zgb
Zws
Za
Mig
Zgb
COma
DOsgd
COmfg
Sabf
Zgb
Mig
COm
Didc
ZgbZgb
COms
Dgg+Mig
DSaqd
COmsg
Za
DOsgd
Zgdn
Didf
DOsdf
Dgg
Zwq
DSaqd
Zgdn
Zwq
Zgdn
Sabf
Zws
Sabf
COms
Zwq
Mig
Didc
COmsg
Zwq
Zws
Za
Zwq
Didf
Zwq
Zws
Zgb
Zws
COms
Zws
Za
Zws
COmsg
COma
DSap
COmfga
DSap
Didc
Za
Mig
Zgb(?)
COmfga
Mig
DSap
Za
COm
Zwq
Dgg(?)
Zwa
COmfg
DOsgd
COma
DSap
Zgbg
Zgb
Zwq
DOsdf
TrJd
Zws
COmfgs
Mig
TrJdTrJd
DOsdp
Mig
DSaqdm
Za
Zna
40
7535
30
545
45
45
35
456550
45
40
3025
80
~80
85
70
7589
40
35
65
30
~35
70
65
85
20
38
80
70
54
71
44
74
68
7084
80
84
82
87
86
86
83
50
66
68
70
55
40
40
8075
13
70
80
80
3384
64
85
85
62
82
55
40
24
30
55
72
60
6780
3555
75
82
8537
65
58
74
75
70
5545
57
60
6375
80
70
85
45
15
40
55
70
65
78
77
5568
52
7056
65
605755
42
35
22
3255
24
55
46
3337
40
35
35
3233
30
36
34
40
80
38
50
68
55
20
65
85
6040
85
52
85
87
43
80
55 67
64
80 10
65
83
83
85
80
29
80
45
65
75
8030
45
48
51
60
6870
16
54
55
28
60
6035
45
3538
80
33
48
65
47
50
46
45
10
32
42
52
62
29
23
30
40
55
23
26
85
68
53
34
68
55
45
58
69
4950
52
40
47 70
55
64
8450
59
32
4147
34
54
32
48
56
47
54
62
35
54
48
85
66
34
43
68
52
37
43
64
3046
30
30
42
68
34
32
13
4723
6556
44
41
54
70
45
77
52
73
23
7780
71
74
73
57
55
72
75
80
4276
76
23
85
72
75
64
78 6542
818259
6637
70
48
78
57
14
66
40
58
56
54
75
81
51
4772
56
31
40
55
40
40
55
80
53
50
70
48
55
35
2532
45 30
40
36
45
60
4030
36
33
55
4640
4136
36
46
38
2636
34
32
40
50
35
8060
6553
36
80
39
38
52
46
75
28
32
28
40
15
38
2545
30
58
28
87
48
8287
50
70
80
89
45
65
8317
32
5866
63
45
57
6766
42
80
60
76
45
52
84
38
35
40
52
35
30
52
50
17
47
35
39
34
45
33
34
35
30
70
48
46
70
45
36
29
32
40
40
30
3431
33
60
87
64
8
40
25
812
42
30
59
4565
35
75
80
80
65
72
60
67
72
54
65
75
75
47
82
78
33
35
47
62
45
61
50
54
65
60
50
70
28
24
8540
80
25
7889 75
46
43
55
65
30
57
50
22 21
46
50
63
74
82
37
54
3438
33
23
36
28
29 45
63
35
55
7062
4772
63
45
47
42
67
32
55
38
56
42
46
45
24
54
54
72
33
78
74
64
64
62
63
7528
84
6143
47
74
47
3737
47
87
75
55
70
45
75
77
37
42
30
33
44
75
58
4947
39
395242
35
8265
35
52
40
5848
2558
37
65
55
65
50
44
52
24
53
28
27
40
68
47
62
86
58
66
79
24
60
52
4034
42
42
29
24
38
5655
48
28
18
34
59
40
61
47
46
60
42
2260
70
15
64
8
7
6
9
4
9
9
9
40
45
32
20
10
28
40
12
90
23
28
28
4733
32
25
49
66
31
10
34
33
45
19 2411
24
17
27
14
10
18
25
14
5
50
24
6
7
7
30
62
10
11
25
40
22
14
20
13
9
8
50
53
70
17
58
18
48
80
14
34
18
12 42
65
1511
25
36
45
20
42
26
2825
33
14
37
45
30
7380 46
COms
~60
TrJd
Zgb
Zmgru
DSap
COmsg
DOsgd
DOsdp
COm
COmCOma
DOsdp
Za
Zmgru
Zmgru
DSap
METROWESTTUNNEL
WACHUSETT-MARLBOROUGH
TUNNEL
?
?
?
Dgg
NA
SHO
BA TER
RA
NE
AVALO
N TER
RA
NE
Areas of abundantgranitic dikes
Area of abundantgranitic dikes
Area of abundantgranitic dikes
Zmgru shearednear contact with Za
ee
e
e
Approx. southern limit of ductile deformation and brittle faults associated with Bloody Bluff Fault Zone
Approx. northern limit of major brittle
faults associated with Bloody Bluff Fault Zone
BLOODY BLUFF FAULT ZONE
BLOODY BLUFF / LAKE CHAR FAULT
SPENCER BROOK FAULT ZONE
ASSABET RIVER FAULT ZONE
Zone of closely-spaced major brittle faultsand mylonite exposed in Metrowest Tunnel
Za
AVALON TERRANE
Paleozoic (?) Intrusive Rocks
SUDBURY VALLEY INTRUSIVE COMPLEX (DEVONIAN TO ORDOVICIAN?)Locally sheared to biotite gneiss and chlorite schist within Bloody Bluff Fault Zone. Equivalent in part to Zv and Zdigb as mapped by Zen et al. (1983). Age inferred based on correlations with similar rocks to the northeast (Hon et al., 1993).
DIORITE- Chiefly gray-weathering, mottled dark-gray to dark-greenish-gray, fine- to coarse-grained porphyritic quartz-microcline-biotite-hornblende-plagioclase±chlorite±epidote diorite to granodiorite (DOsdp; Photo 11). Characteristic plagioclase porphyroblasts up to 1 cm in diameter are abundant. Locally gneissic near margins with other units. A fine grained phase is present along the Sudbury Resevoir (DOsdf).
GABBRODIORITE- Dark-gray-green to black, fine- to medium-grained plagioclase-hornblende±biotite gabbro or diorite with characteristic pink-weathering microcline megacrysts (Photo 12). Megacrysts locally occur in swarms which grade into xenoliths of granitic rock.
Neo-Proterozoic Plutonic rocksNote: The Neo-Proterozoic plutonic rocks commonly contain small bodies of dark-greenish-gray, crumbly, fine-grained chloritized biotite amphibolite and biotite schist, up to 3 m in width intepreted to be altered mafic dikes or sills which are distinct from TrJd (Hepburn and DiNitto, 1978).
ALASKITE (NEO-PROTEROZOIC?)- Beige- to to pink-weathering, light gray to pinkish-gray, fine-grained quartz-microcline-feldspar-±magnetite alaskite to aplite (Photo 10). Magnetite typically occurs as small dipyramids. Equivalent to the Hope-Valley Alaskite Gneiss as mapped by Walsh and Aleinikoff (in press) and Proterozoic Alaskite as mapped by Kopera et al. (2007), in part to Zhv as mapped by Zen et al. (1983), and the mafic-poor foliated Milford granite as mapped by Hepburn and DiNitto (1978). Age: 601 ± 7 Ma (SHRIMP/zircon; G. Walsh, written commun., 2006) for Zhg in the Grafton quadrangle.
GRANODIORITE AT NOURSE FARM (NEO-PROTEROZOIC?) (after Markwort, 2006, in the Shrewsbury quadrangle)- Light- to medium-gray, medium- to coarse-grained plagioclase-feldspar hornblende±biotite±epidote granodiorite to diorite (Photo 14). Pods and masses of epidote are common.
BIOTITE-GRANITE AND GRANITE-GNEISS (NEO-PROTEROZOIC?)- Light-pink-gray to light-pink, medium- to coarse-grained moderately to well-foliated -biotite-quartz-feldspar-microcline±magnetite granite to granodiorite (Photo 10). Rock typically contains 3-5% biotite, but locally 10% or more. Locally sheared to a biotite-magnetite gneiss (Zgbg). Partly equivalent to Zsg and Zpg as mapped by Walsh and Aleinikoff (in press) in the Grafton quadrangle, Zen et al., (1983), and the foliated Milford granite as mapped by Hepburn and DiNitto (1978).Age: 604 ± 5 Ma and 607 ± 5 Ma (SHRIMP/zircon; G. Walsh, written commun., 2006) for Zpg in Grafton quadrangle.
UNDIFFERENTIATED MILFORD GRANITE AND BIOTITE-POOR GRANITE (NEO-PROTEROZOIC)- Light-pink-gray to gray medium- to coarse grained weakly to well-foliated quartz-feldspar-microcline±biotite±hornblende±magnetite granite and alaskite (Photo 13). Mafic minerals are typically found in trace amounts up to 1-3%. Biotite where present, commonly occurs in distinctive 0.5- to 1 cm-diameter clots. Magnetite commonly occurs in granular masses with biotite and hornblende, and locally as small dipyramids. Equivalent in part to Zhg as mapped by Zen et al., (1983), the Milford granite as mapped by Kopera et al. (2007), and phases of the Milford granite as mapped by Hepburn and DiNitto (1978). Late, fine-grained aplitic dikes are common. Age: 633 ± 9 Ma and 601 ± 7 Ma (SHRIMP/zircon; G. Walsh, written commun., 2006) for Zhg in the Grafton quadrangle. Approximately 606 Ma (206Pb/238U) for the Milford granite in the Holliston quadrangle (M. Thompson, written commun., 2007).
Stratified RocksStratified rocks of the Avalon terrane have been metamorphosed under conditions of the greenschist and lower amphibolite facies.
WESTBORO FORMATION (NEO-PROTEROZOIC OR YOUNGER?)
QUARTZITE- Chiefly light- to dark-gray, tan, or pink-gray, fine-grained, well-bedded to massive feldspathic to pure quartzite (Photo 15). Interbeds of micaceous quartzite and quartz-mica schist are common. Light-green, fine- to medium-grained actinolite-carbonate calc-silicate granulites, light-purplish-brown fine-grained biotite granulites, or calc-silicate-bearing quartzites are common as thin layers, pods, or lenses within the quartzite. Interbeds of Zws are common.
SCHIST AND GREENSTONE- Rusty weathering, dark-gray, fine- to medium-grained biotite-quartz-feldspar schist and phyllite, light-gray fine- to medium-grained muscovite-quartz schist, dark-green fine- to medium-grained chlorite schist and phyllite, and dark-bluish-gray to dark-green fine-grained chlorite-epidote greenstone with isolated pods and lenses of quartzite. Interlayers of light- to medium-gray weathering, dark-gray to dark-gray-green hornblende-plagioclase±biotite±epidote amphibolite, amphibolite gneiss, or
EXPLANATION OF SYMBOLS
Location of cited photo shown below
Exposure
Bedrock outcrop examined in field
Area of abundant outcrop or shallow bedrock (within 10 feet of surface)
Well or geotechnical boring used to constrain bedrock lithology in areas of poor bedrock exposure. Data obtained from Duncan and Mabee (2004), and unpublished data by D. Ashenden (written commun., 2004)
Alignment of subsurface tunnel data used in construction of map
Planar Features (placed over location measured. Where many symbols present placed as close to outcrop as possible)
Strike and dip of foliaton and vertical foliation in all rocks, composite S1 foliation in the Marlborough formation, composite S1 or later foliation in the Nashoba formation, and foliation of undetermined age in plutonic rocks. In all layered rocks foliation is dominantly parallel to bedding and/or compositional layering.
Approximate strike and dip of heavily contorted foliation
Strike and dip of secondary foliation and crenulation cleavage (S2) in Marlboro Formation. This foliation generally parallels the axial surfaces of F2 folds and cuts the S1 foliation.
Strike and dip of axial surface of secondary fold (F2) of S1 foliation in the Nashoba terrane (Photo 1), or fold of undetermined age in Avalon Terrane.
Mylonitic fabric and/or shear fabric of undetermined age
Fracture cleavage of undetermined age
Brittle fault observed in outcrop or tunnel interpreted to be significant at map scale. For additional outcrop-scale brittle structure information, see Mabee and Salamoff (2006).
Linear Features
Trend and plunge of mineral lineation of undetermined age
Trend and plunge of axis of secondary fold (F2) of S1 foliation in the Nashoba terrane, or fold of undetermined age in the Avalon terrane
EXPLANATION OF LINES
Contact-- Accuracy of location indicated by proximity to bedrock exposures. Contacts between units within the Marlboro Formation and Neo-Proterozoic plutonic rocks are generally gradational.
Trace of discrete shear zone or sheared contact. Queried in Nashoba terrane where relations to Andover granite are unknown.
Zone of sheared and cataclastic rocks (e.g. Photo 16)
Trace of brittle fault. Approximate dip shown where exposed in subsurface tunnel and/or outcrop. Only the traces of faults that can be supported by unequivocal field evidence are shown.
Trace of axial surface of map-scale F2 or later antiform showing plunge of axis, where estimated. Dashed where existence inferred.
DOsdp
DOsgd
Zgdn
Zmgru
Zwq
Zws
30
30
30
30
30
30
30
30
30
~60 DOsdf
ZgbgZgb
Zwa
CITED REFERENCES
Arvin, T., 2006, Bedrock geology of the Maynard quadrangle, Massachusetts [Master's Thesis]: Chestnut Hill, Ma, Boston College.
Acaster, M., and Bickford, M.E., 1999, Geochronology and geochemistry of Putnam-Nashoba Terrane metavolcanic and plutonic rocks, eastern Massachusetts; constraints on the early Paleozoic evolution of eastern North America: Geological Society of America Bulletin, v. 111, p. 240-253.
Castle, R.O., Hepburn, J.C., and Kopera, J.P., (in press), Bedrock geologic map of the Lawrence quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-01. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database.
Castle, R.O., Hepburn, J.C., and Kopera, J.P., (in press), Bedrock geologic map of the South Groveland quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-02. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database.
Castle, R.O., Hepburn, J.C., and Kopera, J.P., (in press), Bedrock geologic map of the Wilmington quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-03. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database.
DiNitto, R.G., 1983, The Bedrock Geology of the Marlborough Area, Massachusetts [Masters thesis]: Chestnut Hill, Ma, Boston College.
Duncan, C., and Mabee, S.B., 2004, Well Inventory of the Marlborough quadrangle, Massachusetts, Office of the Massachusetts State Geologist Well Inventory 04-01. ESRI ArcView Database.
GZA GeoEnvironmental Inc., Jacobs Associates, and Sverdup Civil Inc., 2005, Geotechnical Data Report, Metrowest Water Supply Tunnel, Construction Packages 1, 2 and 3: Massachusetts Water Resource Authority Contracts 6054, 6055, and 6059. Volumes I and II.
Handford, L.S., and Staff, 1965, Rb-Sr whole-rock age study of the Andover and Chelmsford granites, Massachusetts: Massachusetts Institute of Technology, Department of Geology and Geophysics, 13th Annual Report to the U.S. Atomic Energy Commission, Contract AT(30-1)-1381, p. 11-14.
Hansen, W.R., 1956, Geology and mineral resources of the Hudson and Maynard quadrangles, Massachusetts: U. S.G.S. Bulletin 1038.
Hatch, N.L., Jr., editor, 1991, The bedrock geology of Massachusetts, U. S. Geological Survey Professional Paper 1366.
Hepburn, J.C., 1978, Preliminary reconnaissance bedrock geologic map of the Shrewsbury Quadrangle, Worcester County, Massachusetts: U.S.G.S. Open File Report 78-951.
Hepburn, J.C., and DiNitto, R.G., 1978, Preliminary bedrock geologic map of the Marlborough Quadrangle, Middlesex and Worcester counties, Massachusetts: U.S.G.S. Open File Report 78-222.
Hepburn, J.C., Dunning, G.R., and Hon, R., 1995, Geochronology and regional tectonic implications of Silurian deformation in the Nashoba Terrane, southeastern New England, U.S.A: Geological Association of Canada Special Paper, v. 41, p. 349-365.
Hill, M.D., Hepburn, J.C., Collins, R.D., and Hon, R., 1984, Igneous rocks of the Nashoba Block, eastern Massachusetts in Hanson, Lindley S. [editor] Geology of the Coastal Lowlands; Boston, MA to Kennebunk, ME: Salem State College, Dept. of Geological Sciences, Salem, MA. New England Intercollegiate Geological Conference Guidebook v. 76, p. 61-80.
Hon, R., Paige, M.L., and Loftenius, C.J., 1993, Petrogenesis of two diverse mid-Paleozoic complexes of eastern Massachusetts; A-type Cape Ann Granite and I-type Sharpners Pond Quartz Diorite in Cheney, John T. and Hepburn, J. Christopher [editors], Field trip guidebook for the northeastern United States; 1993 Boston GSA: University of Massachusetts, Amherst, Dept. of Geosciences Contribution n. 67, p. Q1-Q28.
Kopera J.P., Shaw C.E. Jr.,,and Fernandez, M., 2007, Preliminary bedrock geologic map of the Milford quadrangle, Massachusetts: Office of theMassachusetts State Geologist Open File Report 07-01. Scale 1:24,000. 4 sheets and digital product: Adobe PDF and ESRI ArcGIS database.Mabee, S.B. and S. Salamoff, 2006, Fracture characterization map of the Marlborough quadrangle, Office of the Massachusetts State Geologist Geologic Map 07-01. Scale 1:24,000. 5 sheets and digital product: Adobe PDF and ESRI ArcGIS database.
Markwort, R., 2006, Bedrock geology of the Shrewsbury quadrangle, Massachusetts [Master's Thesis]: Chestnut Hill, MA, Boston College.
Skehan, J.W., and Abu-Moustafa, A.A., 1976, Stratigraphic analysis of rocks exposed in the Wachusett-Marlborough Tunnel, East-central Massachusetts in Contributions to the stratigraphy of New England: Geological Society of America Memoir n. 148, p. 217-240.
Walsh, G.J., and Aleinikoff, J.N., in press Bedrock Geologic Map of the Grafton Quadrangle, Worcester County, Massachusetts: U.S. Geological Survey Scientific Investigations Map. 2 Sheets.
Zartman, R.E., and Naylor, R.S., 1984, Structural implications of some radiometric ages of igneous rocks in southeastern New England: Geological Society of America Bulletin, v. 95, p. 522-539.
Zen, E.A., Goldsmith, R., Ratcliffe, N.M., Robinson, P., Stanley, R.S., Hatch, N.L., Jr., Shride, A.F., Weed, E.G.A., and Wones, D.R., 1983, Bedrock geologic map of Massachusetts: U.S.G.S., Scale 1:250,000
DSap
DSaqd
Mig
Sabf
TrJd
EXPLANATION OF UNITS
DIABASE- Dark gray fine- to medium-grained, locally porphyritic diabase, occuring as north to northeast trending 10 cm- to 3 meter-thick dikes and dike swarms (Photo 2).
NASHOBA TERRANE
Intrusive Rocks
INDIAN HEAD HILL PLUTON
GRANITE (MISSISSIPIAN)- Chiefly light-gray- to buff-weathering, light-gray to gray, fine- to medium-grained massive biotite-quarts-microcline-plagioclase granite, locally varying from granodiorite to quartz monzonite (Photo 3). Locally exhibits weak foliation.Age: 349±4 Ma (U-Pb/zircon, titanite; Hepburn et al., 1995).
DIORITE (DEVONIAN?)- Chiefly medium-gray weathering, mottled dark-gray, coarse-grained biotite-hornblende-plagioclase ±quartz ±orthoclase diorite and granodiorite (Didc; Photo 3) locally grading into dark-gray, fine- to medium-grained diorite (Didf).Age: 402±5 Ma for Didc (Rb-Sr/whole-rock; Hill et al., 1984)
GRANITE-GNEISS (DEVONIAN OR OLDER?)- Buff- to pink-weathering, fine-to-medium grained, moderately to well-foliated biotite-quartz-feldspar granite gneiss with locally distinct schlieren-like compositional segregations (Photo 7). Interfolded with Marlboro Formation. Overhatching indicates areas where extensively intruded by Mig. In part equivalent to Grafton granite in Grafton quadrangle (518 ± 5 Ma; SHRIMP/zircon; G. Walsh, written commun., 2006).
ASSABET QUARTZ DIORITE (SILURIAN TO DEVONIAN?)- Medium- to dark-gray weathering, dark-gray, medium- to coarse-grained, quartz-biotite-plagioclase-hornblende±magnetite±garnet±pyrite diorite. Locally contains thin layers of rusty-weathering, silliminite-biotite-muscovite±garnet schist. Locally sheared to a biotite-pyrite schist (Photo 4), mylonite (DSaqdm), and/or faulted to a carbonate-sulfide breccia. Formerly mapped as the Straw Hollow diorite by Hepburn and DiNitto (1978), and DiNitto (1983). Possibly correlative with Sharpner's Pond pluton to northeast.Age: 430±5 (U-Pb/zircon from Sharpner's Pond diorite; Zartman and Naylor, 1984); 385± 10 Ma (U-Pb and Pb-Pb/zircon; Acaster and Bickford, 1999)
ANDOVER GRANITE
PEGMATITIC GRANITE (DEVONIAN TO SILURIAN?)- Buff- to pinkish-weathering, light- to medium-gray, coarse-grained to pegmatitic muscovite-biotite-placgioclase-microcline-quartz±garnet granite, granodiorite, and quartz monzonite (Photo 5). Generally displays a coarse gneissic foliation. Age: 412±2 Ma (U-Pb/zircon; Hepburn et al., 1995); 408±22 Ma (Rb-Sr/whole rock; Zartman and Naylor, 1984), 415 Ma (Rb-Sr/whole rock; Hill et al., 1984).
FOLIATED BINARY GRANITE (SILURIAN TO ORDOVICIAN?)- Buff-weathering, light- to medium-gray, well to moderately foliated, medium- to coarse-grained quartz-microcline-plagioclase-biotite-muscovite granite to quartz-monzonite gneiss (Photo 6). Locally fine- to medium-grained. Locally contains xenoliths of amphibolite. Correlation with Andover granite in type locality uncertainAge: 446±32 (Rb-Sr/whole rock; Zartman and Naylor, 1984); 450±23 (Rb-Sr/whole rock; Handford et al., 1965).
Areas of abundant granitic dikes and sills of undetermined age and affinity. Includes probable dikes and sills of Mig and Dgg.
Didc Didf
COmsg
COm
COms
On
Stratified RocksStratified rocks in the Nashoba terrane have been metamorphosed under conditions of the mid- to upper amphibolite facies.
NASHOBA FORMATION (ORDOVICIAN OR OLDER?)- Chiefly medium- to dark-gray, fine- to coarse-grained, quartz-plagioclase biotite±microcline±silliminite ±garnet gneiss (Photo 8), with subsidiary interlayers of amphibolite, calc-silicate, marble, quartzite, granulite, and biotite-muscovite-silliminite±garnet schist. Locally migmatitic. Contains abundant dioritic to granitic dikes and sills. The Nashoba Formation is poorly exposed in the Marlborough quadrangle.
MARLBORO FORMATION (CAMBRIAN TO ORDOVICIAN OR OLDER?)-
FELSIC GRANULITE AT MILLHAM RESERVOIR- Light-gray- to tan-weathering, medium- to dark-gray, massive to moderately foliated, homogeneous, fine- to medium-grained, muscovite-biotite-plagioclase-quartz granulite (Photo 9). Gray-white feldspar porphyroclasts locally give rock charcteristic “mottled” appearance. Also included are lenses of rusty-weathering, fine-grained silliminite-biotite-muscovite schist (COmfgs), a light-gray weathering lineated coarse-grained biotite-plagioclase-hornblende amphibolite with distinctive pods of granite and granodiorite (COmfga).
AMPHIBOLITE AND SCHIST- Interlayered rusty-weathering, black to dark-gray, fine-to coarse-grained quartz-plagioclase-muscovite-biotite±silliminite±garnet schist (COms) and light- to medium-gray weathering, black to dark-gray hornblende-plagioclase-biotite-quartz amphibolite (COma). Garnet and silliminite occur locally as thin layers within the schist. Thin layers of light-gray- to buff- to rusty-weathering, dark gray biotite-muscovite-plagioclase-quartz granulite and calc-silicate also occur locally.
SCHIST AND GRANULITE- Light-gray-weathering, fine- to medium-grained biotite-muscovite-quartz-plagioclase±hornblende±garnet granulite interlayered with rusty- to silvery-white-weathering, silvery to dark brown to dark-gray, fine-grained quartz-plagioclase-muscovite-biotite±garnet schist (Photo 1, Photo 7), with local interlayers of amphibolite. Garnet coticule and calc-silicate layers locally present.
UNIDFFERIENTIATED AMPHIBOLITE AND OTHER ROCKS- Chiefly dark to light gray-weathering, locally rusty weathering, black, fine- to medium-grained epidote-quartz-biotite-plagioclase-hornblende amphibolite. Locally interlayered with dark-gray to black, fine-grained quartz-muscovite-plagioclase-biotite ±hornblende±garnet schists; light gray to beige granulites, fine-grained, granulitic quartz-muscovite-biotite-plagioclase±hornblende calc-silicates; and dark-gray, medium- to coarse-grained biotite-plagioclase-quartz gneisses and schists. Epidote and calc-silicate occurs locally as thin layers, boudins, and knots ranging from 5 cm to 1 m in length (Photo 2, Photo 7). Two- to five cm-thick stringers of plagioclase and quartz commonly occur parallel to foliation. Locally migmatitic along the Bloody Bluff Fault and near mappable bodies of Cgg. Mostly equivalent to the Sandy Pond Amphibolite of Hepburn and DiNitto (1978) and DiNitto (1983). Outcrop where layers of epidote are abundant in Marlboro Formation
COma
COmfgCOmfga
COmfgs
10
Dgg
DSaqdm
~10-20
e
~10-20
~80-89
A
A'
MASS.
QUADRANGLE LOCATION
Topographic base modified from U.S. Geological Survey, 1969Polyconic projection. Reprojected to 1983 North American Datum.
10,000 foot grid ticks based on Massachusetts state plane coordinate system, mainland zone, 1927 North American Datum
1000-meter Universal Transverse Mercator grid ticks from 1927 North American Datum, zone 19 Hydrography from MassGIS (http://www.mass.gov/mgis)
Data Sources:-Fieldwork by J. P. Kopera (2003-2006), assisted by A. Koenigsberg (2005)-Hepburn and DiNitto, 1978 (USGS Open File Report 78-222)-DiNitto, 1983 (M.S. Thesis, Boston College)-Unpublished data by D. Ashenden (written commun., 2004)-Skehan and Abu-Moustafa, 1976 (Wachusett-Marlborough Tunnel)-Unpublished data by Hager Geoscience (written commun., 2006; Metrowest Tunnel)-Duncan and Mabee, 2004 (borehole data)-GZA GeoEnvironmental, Inc., et al., 2005 (Metrowest Tunnel)-Digital cartography and editing by J.P. Kopera (2006, 2008)
MA
GN
ET
IC N
OR
TH
AP P R O X IMAT E ME ANDE C L IN AT IO N , 1999
TR
UE
NO
RT
H
15 / 1 2
OMSG Geologic Map No. 06-01Bedrock Geology
Marlborough Quadrangle 2006
Map last modified 3/13/08
Comments to the Map User
A geologic map displays information on the distribution, nature, orientation and age relationships of rock and deposits and the occurrence of structural features. Geologic and fault contacts are irregular surfaces that form boundaries between different types or ages of units. Data depicted on this geologic quadrangle map are based on reconnaissance field geologic mapping, compilation of published and unpublished work, and photogeologic interpretation. Locations of contacts are not surveyed, but are plotted by interpretation of the position of a given contact onto a topographic base map; therefore, the accuracy of contact locations depends on the scale of mapping and the interpretation of the geologist(s). Any enlargement of this map could cause misunderstanding in the detail of mapping and may result in erroneous interpretations. Site-specific conditions should be verified by detailed surface mapping or subsurface exploration. Topographic and cultural changes associated with recent development may not be shown.
We recommend reading Reading Maps with a Critical Eye: Becoming an Informed Map Reader by the Maine Geologic Survey (http://www.maine.gov/doc/nrimc/mgs/mapuse/informed/informed.htm), to make the best use of a geologic map.
Cross sections are constructed based upon the interpretations of the authors made from geologic mapping, and available geophysical and subsurface (drillhole) data. Cross sections should be used as an aid to understanding the general geologic framework of the map area, and not be the sole source of information for use in locating or designing wells, buildings, roads, or other man-made structures.
This research was supported by U.S. Geological Survey, National Cooperative Geologic Mapping Program, under assistance Award No. 03HQAG0067 and an NSF REU Grant to the Association of American State Geologists.
The authors wish to thank Gregory J. Walsh, David Ashenden, and Patrick J. Barosh for thoughtful and thorough reviews.
Citation:Kopera J., Hepburn J.C., and DiNitto R., 2006, Bedrock geologic map of the Marlborough quadrangle, Massachusetts: Office of the Massachusetts State Geologist Geologic Map 06-01. Scale 1:24,000. 1 sheet and digital product: Adobe PDF and ESRI ArcGIS database.
This map was produced on request directly from digital files (PDF format) on an electronic plotter.
A digital copy of this map (PDF format), including GIS datalayers, is available at http://www.geo.umass.edu/stategeologist
Author Affiliations: 1Corresponding Author: Office of the Massachusetts State Geologist E-mail: [email protected] Department of Geology and Geophysics, Boston College, Chestnut Hill, MA 02467
3 Sleeman, Hanley, & DiNitto, 50 Congress St, Boston, MA 02109
Bedrock Geologic Map of the Marlborough Quadrangle, Massachusettsby: Joseph P. Kopera1, J. Christopher Hepburn2, and Richard G. DiNitto3
OFF
ICE O
F THE STATE GEOLOGIST
UN
IVERS ITY OF MAS SACHUSETTS
Office of the Massachusetts State GeologistUniversity of Massachusetts, AmherstAddress: 269 Morrill Science Center, 611 North Pleasant Street, Amherst, MA 01003Phone: 413-545-4814 E-mail: [email protected]: http://www.geo.umass.edu/stategeologist
Photo 1. Compositional layering and parallel foliation (S1) defining F2 folds about S2 in the schist and granulite member (COmsg) of the Marlboro Formation.
S 2
S1
Photo 2. A Mesozoic diabse dike (TrJd) cross-cutting compositional layering in the Marlboro Formation (COm). The light green streaks are layers of epidote and are common in the Marlboro Formation.
TrJdCOm
Photo 3. Coarse-grained granite (Mig) intruding well-foliated, coarse-grained diorite (Didc) of the Indian Head Hill Pluton. The fine-grained black layers in the diorite are xenoliths of amphibolite of the Marlboro Formation (COm)
Mig
Didc
COm
Photo 4. A shear zone cross-cutting the Assabet quartz diorite (DSaqd) near the Assabet River fault zone. Quartz veins that were stretched into boudins form the white blebs in the photograph. A dike of sheared Andover granite (DSap) is shown near the top of the photograph.
DSaqd
Shear Zone
DSap
Photo 5. A pavement outcrop of the pegmatitic phase of the Andover granite (DSap). The granite is a heterogeneous mix of pegmatite and finer-grained granite, and exhibits a weak gneissic foliation parallel to regional foliation. Photograph taken in southeasternmost portion of the Hudson quadrangle, approximately .5 miles west of intersection of Hudson Rd. and Broad St., in the town of Marlborough.
Photo 6. Foliated binary Andover Granite (Sabf). Streaks of biotite and muscovite locally define the foliation. Photograph taken from the Hudson quadrangle at intersection of Marlboro St. and Reed Rd. in the town of Hudson.
Photo 7. Dike of granite gneiss of the Indian Head Hill pluton(Dgg) cross-cutting foliation of the schist and granulite of the Marlboro Formation (COmsg). A phase of regional deformation post-dated the intrusion of the granite-gneiss, resulting in folded (F2) intrusive contacts.
Dgg
COmsg
Photo 8. Sheared and folded migmatitic gneiss of the Nashoba formation (On). Photo taken in Hudson quadrangle, approximately 50 meters north of intersection of Crescent St. and Hartley Rd. in Stowe center.
Photo 9. Felsic granulite at Milham Resevoir (COmfg). Foliation is defined by layers of white-weathering felspar porhyroclasts. The entire unit is intensley sheared by the Assabet River fault zone.
Photo 10. Fine-grained alaskite (Za) intruding foliated coarse-grained Neo-Proterozoic biotite-granite (Zbg).
Photo 11. Porphyritic diorite (DOsdp) of the Sudbury Valley intrusive complex. The white-weathering plagioclase phenocrysts are characteristic of this unit.
Photo 12. Gabbrodiorite (DOsgd) of the Sudbury Valley Intrusive complex with a xenolith of Neo-Proterozoic granite. The contacts between the xenoliths and gabbrodiorite are commonly gradational, and are characterized by bright pink-weathering feldspars in a gabbro-diorite matrix. The green epidote vein cross-cutting the contact is related to motion along the Bloody Bluff Fault zone just to the north of the outcrop. Photo taken in the Framingham quadrangle, approximately 0.25 miles east of the intersection of Broad Meadow St. with the boundary between the Marlborough and Framingham quadrangles.
DOsgd
Granitexenolith
Photo 13. Undifferentiated Milford granite and biotite-poor granite (Zmgru) with trace mafic minerals.
Photo 14. Granodiorite at Nourse Farm (Zgdn). Zgdn characteristially contains pods and masses of epidote, as shown in the above photograph.
Photo 15. Sheared quartzite (Zwq) of the Westborough formation. Shearing has obliterated bedding at this outcrop and has formed finely laminated foliation planes on which the pencil is resting.
Photo 16. Sheared and altered granite within the Bloody Bluff fault zone.
1 2
3
4
7
9
10
11
13
14
1516
Zna
Zbg
Zone of intense shearing
and cataclasis
Sheared and altered granite
Epidote
Zwq
Zhg
PZa
Zws
Zgb
DO
sdp
Mig
Cgg
TrJd
CO
msg
CO
ma
On
CO
mfg
SE
A LE
VE
L
500
-150
0 ft
1500
ft
1000 500
1000
SE
A LE
VE
L
500
-500
-100
0
BEND IN SECTION
East Main Street
Penn. Central RR
Hayes Memorial Drive
Wac
huse
tt-M
arlb
orou
ghT
unne
l
AA
'
Massachusetts Turnpike
Sudbury River
Ced
ar S
wam
p
Route 9
New
ton'
s H
illW
alnu
t Hill
(D
rum
lin)
Wac
huse
tt A
qued
uct
I-290
Assabet River
-150
0 ft
1500
ft
1000
CO
m
BLO
OD
Y B
LUFF
FAU
LT Z
ON
E
ASS
AB
ET R
IVER
FAU
LT Z
ON
E
Brit
tle fa
ults
ob
serv
ed in
tunn
el
Mig
}
