A

A'

B

B'

C

C'

Sap

Ssd

Oba

Obb

SOmb

SOme

Obb

COf

Ssd

Ssbh

Oba

Obg

Sab

Obg

Sam

Obba

Obba

Ssbh

Obb

Obba

Obb

Obba

Ssbh

Obb

Sab

Sab

Obba

Obba

Ssbh

Ssb

Ssbh

Sap

Ssd

Obba

Ssd

Obb

Obb

Sab

Obba

Obba

Obba

Ssd

Ssbh

Obba

Ssbh

Ssd

Obb

Ssb

Obb

Obb

Ssb

Ssbh

Sab

Obb

Obba

Sab

Sap

Ssd

Obba

Ssb

Ssbh

Obba

Sap

Obb

Ssd

Obb

Sap

Obba

COf

Ssd

COf

Ssbh

Sab

COf

Obb

Obb

Sab

Ssb

Obb

Obba

Ssb

Obb

Obba

Sap

Obba

Ssbh

Ssd

Sap

Sab

Sap

Ssb

Sap

0

0

0

80

78

84

80

70

80

8683

60

84

75

76

8486

48

80

86

74

74

50

65

84

20

0

0

82

80

78

75

75

75

70 50

45

60

4443

8586

41

58

81

75

85 50

85

41

7067

75

6878

70 80

7870

71

72

70 30

4130

36

76

80

63

80

6076

51

45

45

41

7470

2030

202669

3578

29

7780

77

30 31

38

7875

63

45

76

75

75

7370

80

17

8080

83

85

65

72

72

65

85

68

3540

78

50

60

68

83

78

38

4438

54

64

45

71

70

64

25

40

42

2452

65

282351

21

75

24 24

24

1933

13

78

55

16

25

34

23

41

66

15

75

72

62

75

60

48

18

57

65

51

38

18

74

25

85

70

75

65

70

70

65

65

72

87

81

78

8585

5576

15

29

15

28

27

28

85

5644

20

29

17

25

65

5

2

40

48

66

60

72

65

17

63

55

75

38

41

63

41

28

72

50

12

65

57

50

4416

30

55

42

42

57

31

23

6120

Obb

Obb

Obba

Obb

Obba

Obb

Obb

Obb

Obb

Ssd

SsdSsbh

Ssbh

Sap

Sap

Sap

Sap

Ssbh

Sab

Ssd

Ssd

Ssd

COf

CLINTON - NEWBURY FAULT ZONE

Location approximate

Lithologic Contacts

Bedrock Exposure

Individual Outcrop

Photo location

Areas of abundant outcrops or shallow bedrock

(within 10 ft (3 m) of surface)

Faults

Contact, location generally approximate

32

32

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

Strike and dip of cleavage

Trend and plunge of mineral lineation

Trend and plunge of minor fold axis

Antiformal axis, location inferred

EXPLANATION OF MAP SYMBOLS

Only faults traceable at map-scale and on surface are shown

Strike and dip of bedding

Strike and dip of overturned bedding

32

Approximate strike and dip of heavily deformedfoliation / vertical deformed foliation

Mine or bedrock quarry

A

EXPLANATION OF LITHOLOGIC UNITS

MERRIMACK BELT

Metasedimentary Rocks

Merrimack Group (Silurian or Ordovician following Lyons and others 1997)

Berwick Formation

Light-gray to purplish-gray beds from cms. to 1 meter thick of calcareous metasiltstone, biotite-feldspar-quartz granofels, impure quartzite and metasiltstone interbedded with lesser amounts of thin-bedded dark-gray micaceous phyllite, schist and impure quartzite.

Eliot Formation

Thin-bedded, well foliated, silvery-gray to dark-gray-green micaceous phyllite, schist and calcareous phyllite with interbeds of micaceous and calc-silicate bearing quartzite and metasiltstone.

NASHOBA TERRANE

Metasedimentary and Metavolcanic Rocks

Boxford Formation (Ob)

A member

Chiefly fine-grained, well foliated, thin-layered, light-gray to black schist and gneiss. Includes rocks of widely differing mineralogical composition including amphibolite, calc-silicate granolite and gneiss, andalusite-sillimanite-muscovite schist and quartz-feldspar gneiss. Contains a few beds of quartzite along the flanks of the formation.

Amphibolite of B member

Chiefly fine-grained, foliated and locally layered, rusty-brown weathering, gray to black hornblende-plagioclase amphibolite. Differentiated where amphibolite is the prominent rock type.

Quartz-Plagioclase Gneiss

Fine-grained, foliated, but generally unlayered, white to light-gray gneiss composed largely of

plagioclase and quartz with minor amounts of chlorite.

B member

Fish Brook Gneiss

Medium- to fine-grained light- gray to nearly white gneiss with a distinct swirled foliation. Composed mainly of quartz, plagioclase and biotite. Locally contains numerous amphibolite inclusions and thin micaceous interlayers.

Igneous Rocks

Andover Granite (Sa)

Sap Andover Granite, pegmatite facies

Medium to extreamly coarse-grained, massive, white to light-gray pegmatite and monzogranite. Composed mainly of microcline, plagioclase, quartz and muscovite. Biotite occurs locally and garnet is a common accessory. Broad areas underlain entirely by pegmatite.

Sab Andover Granite, binary granite facies

Medium-grained, massive to weakly foliated, white to light-gray monzogranite composed mainly of plagioclase, quartz, muscovite and biotite with accessory garnet. Pegmatites too small to map separately are locally prominent.

Sharpners Pond Tonalite (Ss) Ssd Sharpners Pond Tonalite, hornblende diorite facies

Medium- to coarse-grained, massive, medium-gray to black hornblende diorite and tonalite composed mainly of plagioclase and hornblende with variable small amounts of quartz. Biotite only locally composes as much as 10% of the rock. Principal accessories include magnetite, sphene and apatite.

Ssbh Sharpners Pond Tonalite, biotite-hornblende tonalite facies

Medium-grained, massive to weakly foliated, medium to dark-gray hornblende-biotite tonalite composed mainly of plagioclase, hornblende, quartz and biotite.

Ssb Sharpners Pond Tonalite, biotite tonalite facies

Medium- to fine-grained, massive to foliated, light- to medium-gray tonalite; granodiorite and monzogranite occur locally. Composed mainly of plagioclase, quartz and biotite with lesser amounts of microcline and hornblende.

Sj Andover Granite, muscovite granite-gneiss facies

Chiefly coarse-grained, foliated, light- to medium-gray monzogranite. Composed mainly of microcline, plagioclase and smoky quartz. Moderately deformed and altered. Considered to bevariant of Andover muscovite granite-gneiss facies in Lawrence quadrangle.

Gneissic rocks are composed of quartz and plagioclase with minor actinolite. Amphibolites, in part, are coarser-grained than those of the “B” Unit of the Boxford Fm. Poorly exposed.

COf

Oba

Obb

Obba

Obg

Sab

Sam

Sap

SOmb

SOme

Ssb

Ssbh

Ssd

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

SOUTH GROVELAND 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 South Groveland 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 jkopera@geo.umass.edu

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TR

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QUADRANGLE LOCATION

Sap Ssbh

Oba

SabSab

Ssbh

SabSap

Sab SapObbSsbh

Obb200 m

-200 m

-400 m

-600 m

sea level

500 ft

sea level

-500 ft

-1000 ft

-1500 ft

-2000 ft

CC'

Hol

e H

ill

And

over

Nor

th A

ndov

er

Continuous with A-A' in Reading Quadrangle (Castle, et al., 2005)

200 m

-200 m

-400 m

-600 m

sea level

500 ft

sea level

-500 ft

-1000 ft

-1500 ft

-2000 ft

BA'

Geo

rget

own

Gro

vela

nd

Gro

vela

ndB

oxfo

rd

Park

er R

iver

Section A-A'Bend in SectionBend in Section

Bye

rs H

ill

LakeCochichewick

Haveys Pond

MER

RIM

AC

K B

ELT

NA

SHO

BA

TER

RA

NE

CLINTON - NEWBURYFAULT ZONE

SOmb

SOme

Sap

Obba

Obb

Obba Obba

Sab

Sam

Obb

ObgOba

Obg

500 ft

sea level

-500 ft

-1000 ft

-1500 ft

-2000 ft

Johnsons Pond NA

SHO

BA

TER

RA

NE

MER

RIM

AC

K B

ELT

Cited References

Lyons, J.B., Bothner, W.A., Moench, R.H., and Thompson, J.B. Jr., 1997: Bedrock geologic map of New Hampshire: U. S. Geological Survey, 2 sheets, scale 1:250,000, Reston Virginia.

Fish

Bro

ok

Park

er R

iverSection B-B'

200 m

-200 m

-400 m

-600 m

sea level

Bend in section

SOmb

SOmeSam

Obb Obba Obba

Obb Obb

Obg Obg

Oba Obb Obb

Obba

Obba

Obb

Ssd Ssd

Obba

Obb

COf

COf

AA'

CLINTON - NEWBURYFAULT ZONE

Layered amphibolite and calc-silicates of the B member of the Boxford Formation (Obb)

Schist and gneiss of the B member of the Boxford Formation (Obb)

Layered amphibolite of the A member of the Boxford Formation (Oba). Amphibolites of this member are typically coarser grained than those in the B member

The Fish Brook gneiss (COf) with characteristic swirling foliation

A

B

C

D

A

B

C

D

BEDROCK GEOLOGIC MAP OF THE SOUTH GROVELAND QUADRANGLE, MASSACHUSETTSBy

Robert O. Castle1, J. Christopher Hepburn2, and Joseph P. Kopera3

2005 (in review)