Exit 2

Exit 3

Exit 4

Exit 5

D U

U D

D

U

U

D

60

60

25

54

54

Ag

e

amphibolite

calc-silicate

xenolith

grt

Znfg

157

29

42

81

17

8

80

32

45

76

16

25

20

64

17

32

36

17

29

19 31

26 26 41

33 26

32

30

34

31

27

38

24

28

28 29

28 23 28

29

29

40

26 26

32

26 26

34

24

23

20

24

27

26

37

40

33 22

28

28

31

20

27 30 18

29

29

31

25

26

20

25

70 26

28

29

25

22

24

24

17

37 31 30

27 31

26

33

27

29

30

26

35

85 33

29

33 40

44

30 28

56 22 24

28

35

41

26

30

23 88

23 32

32

33

46

2836

42

34

24 35

19

25

30

34

26

32

31 30

39 25

41

39

37

37

80

27

32

28

30

39

21

27

38

24 28

20

23

27

28

29

34

31 36

28

29 36

44

33

33

37 29

35 35

28

28 39 51

36

30

34 30

35 31

58 31 44

38

35

36

29

31

13

24

66 26

29

36

38

38

31 32 38

29

36

37 44

31

44

46

25

36

31

32 34

29

32 31

28

28

36

36

30

36

44

44 26

27

30

32

36

32

34

20

24

31

31

38 35

35

42 29

32

31

33

30

31 35

36

35 35 24

26 34

35

30

22

30

32 33

26

31

35

24

20

58

31 36 20

21

36 36

27

44 32

49

29

23 34

39 58

32 27

28

28

27

29

31

70

55

23

27

19

21

43

46

24

26

25

28

19

24

29

30

22

25

28

30

30

33

28

28

23

29

46

48

29

29

34

34

28

28

29 37 29

35

36

29

30

25 45

35

35

14

32 35

32

36

36

30

22

26 32

36

18

55

89 33 29

33

35

68 30

30

28

29

36

79

30

31 24

23

27

35

32

33

25 30

61 28

62

26

30

15

24

23

23

68

24

25

24

26

86

29 29

30

45

37 30

31

45 40

31

10

11

21

48

21 20 21

27

27 31

32

31

28

65

32

32

75

25

25

38

17

17 34

28

22 34

42

23

24

33

37

24

30

35

31

21

21

22

32

52

43

25

27

36

40

27

31

20

21

9

16 27

30

25

26

55 18

21 26

22

20

21

14

14

61

17

17 24

27

31

45

33

19 35

33

33

16

24

15

25

32

35

35

25

78 22

36

32

54

57

31

31

35

15

16

62

26

16

46

46

35

35

23

23

30

30

32 66

33

36

30 30

28

28

26

25 80

23

25

60

30

31

29

29

89

24

28

26

31 34

18

20

26 34

36

28

28

30

33

19

23

30

30

28

32

30

33 23

24

24

26

26 29

33

62

66 36

40

52

30

31

31

43

44

44

38 35

37

31

32

60 28 37

60 37

37

35

36

25

26 33

34

68

36

46

22 27

23

74

17 37

67 16 21

24

31

39

38

24

16

32

19

31

15

22

2722

14

26 72

12 16

18

18

17

7

74

15

24

28

83

14

17

18

31

5

14

40

44

13

20 21

20

21

181

24

45

30

35

29

29

44

8

36

41

42

15

15

54

16

20

31

31 58

74

20

25

57

45

17

15

31 62

76 44

48

20

36

33 62

25

29

64

45

48

55

51

50 41

64

50

56

64

65

70

24

50

54

20

69

19

19

16

24

24

43

12 20

30

20 16

17

23

23

82

21

22

21

20

21

24

24

17

17 22

22

13

21

19

24

28

28

24

28

13

34

11

26

20

24

6

20

13

15

16

17

80 28

79

72

52

6

16

20

13

21

10

79 80

72

7

16

89

57

11

86

68

14 28 84

72

50

60

37

18

36

67

17

20

26

18

19

19

21 19 21

29

30

28

42

22

25

30

44

24

27

17

32

33

38 33

22

37

27

28

35 71

35

30

33

47 39

28 34

27

40

38

38 40

31 31

29

30

43

50

33 34

14

17 34

36

15

51

40

44

20

65

26

26

31

16

17 26

26

28

28 30

30 77

24

28 25

28

24

29

24

24

29

29

21

21

13

14

17

17

16

16 19

19

30

35

36

80

22

22

23

20

21 25

22

25

14

15

61 17

34 17

16 17

18

18

19

23

14 65

19

20 19

21

16

16

16 17

25

25

17

22

10

10

32

33

24

23

12 25

18

24

21

21

17

17

29

29 72 22

74

31

31

70

21

18 20

46

19

20 18

22 14

20 23

16 21

25

19 25

36

24 31

21

26

32

32

24

32

17

24

32 39

30

18

20

22

24

21

18 22

18

30

35

26

20

19

20

12

16

17

17 31

32

16

16 20 47 15

26

15

18

78

13

13 27

28

2618 12

74

11

20

26 20

24

24

34

20

18

15

22 25

29

84 30

22

25 30

21 33

29

22

25

32

32

25

67

14

16

17

45

54 53

68

37

40

36 33

34

31

35

25

28

40

39 30 32

76

73

78

11

33

28

72

35

35

32

20

60 25

30

16

16

25

25

51

75

77

58 66

29

33

24

69

32

157

U

D N

U D

R

U

R D

LL

LL

LL

LL

U

R D

UND

U DR

amphibolite

amphibolite

xenolith

xenolith

xenolith

xenolith

calc-silicate

amphibolite

calc-silicate + Zbm

xenolith

grt

grt

Znfg

xenolith

amphibolite

grt + ky

amphibolite

xenolith

81 9

81 84

21 82

74 85 55

76

55

70

29

33

44 24

25

28

59

58

17

78

51 25

83

74

80 83 72

43

87

74 76

62 24

21

81

85

78

80

74

55

20

82 7173

80

26

84

61 73

37

29

26

82

36

52 84

6

52

78

74

31

71

75 27

62

59

36

76

86

24

74

76

51 69

31 83

56

36

80

56

44

31

84 76

58

58 62

82

70

66

7029 42

86

51

64 72

65

78

74 71

68 71

34 69

36

29

41

70 19 82 74

64

7370

32 62

85

74 34

17

76

83 38

88

26

88

79

7230 50

24

61

28

86

57

66

40 28

75

78

59 26

32

26

28

66

76

35

76 68 41 32 80 32

79 78

33 64 23

76

88 46

28

79

35

57

82 25 84

31 30 56

60

83

66 82

32

67

34 74 47

85 58

84 77

74 39

76

64

68

29

67

29

61

65

33 78

28

87 77

71 61

71 77

24 64

86 23 24

76

26

37

40

76

55

65 84

28 81

84 82

81

27

20

31 6468

67

31 30

71 58

79

69 29

86

74 86

3

37

82

84

71

81

61 73

24

17

24

82 68

71

60

76 82

27

80 48

26

49

35

77

72

40 60 44 65

58

29

71

30 33

35

55 85 88 88

51

27

39

25

84 75 83

86 23

84

87

41

72

87 75

36

50

62 82

29

54 60

69

33 71

25 62

84

27 43

38

62

77

44

76

3376

29

75

23

65

65 84

39 32

62 53

33

28 84

54 68

29

88

74 82

31

55

33 67

63

83

35 44 31

83

72 26

52

45

77 70

58

48 75

32 87

54 67

70 76 54

28

31 40

66 28

68

60

54 86 44

36 81

54

35

72 35

42

65

51 35

33

79 76 44 32

47 82 64

78 61 37

36 45

27

47 80

58

46

43

36 81

35

36

76

53

31

68 32

76

64

38

78

58 66

70 43 84 29

51

82

72

34 78

62

68

28

29 74

85

36

87 76 30

47 84

30 68

28

51

74 55

58

36

75

56

80 82

30 64

85

34 28

24

54

70

71

80

66 32

36

79 36 77

71

24 74 21 83

74

11

82

74 74

21

48 70

60

84 58

30

53

31 59

24

80 80 56

79

35

64

32 81

26

23

24

69 68

71

40

41

47

51

73

54

76 74

74 76 84

60

56

66

30

56

21

76

74 71

59

82 62

76

31

32

71

83

56

64

84 57

17

60

24

55

83

57

31

55

50

54

60

16

62

62

77

56 21

67 73

81 49

41

78

71

54

82

77

83

76 80

30

80 78

60

50

82 84

85

78 12

50

69

14

78 17

82 47

57

74

26

45

87 53

30

84

16

71

44 77

55

83 68

42 32

84

21

32

50

31

78 75

53 75

72 36

49

80 36

71

30

28

37

37

16

58

47

27

60

70

61

62 58

17

55

37

32

72

86 38

26

44 34

3648

77

50 68

46

67

25

61 78

58

66

44 31

61

8254

74 58 26

52

68

82

57

64 45

42

26

56

58

62

7662

52

80

3164

33

82 80

58

33

88

59

32

77 43 40

36

78

75 35

78

28

73

82

30 77

50

26

63

72

38 83 84

31 34 87

85

74

82 47 39

85

48

7364

40

4236

84 72

17

62

80 85

51

66

33

62

60

83

74

58

30

21

72

32

38

67

78 52

71 35

62 27

82

44

44

25

68

79

39

28

84

80

57

67

84 42

78 35

81

8439

44

64 84

74 45

61

21 68

80

44

68

20 80

65

88

69

81

27

32

82 26

18

81

18

86

77

84

74

83

78

82

17

82

51 78 31

71

28

86 20 72

30

17

56

23

78 21

70

20

26

24 60

21

34

22 24

76

76

52

24

77

66

82 73

74

74

58

82

81

28

76 74

76 54

55

72

56 48

29

36

82

81

79 87

66

20

75

22

64

74

83

74

24

74 54

67

50

78 17

21

55

61

72

74

31 20

80

87

58 68

86

84

81

20

80 22

25

78

32

51 48

84

62 86

24

85 82

23 85

32

39 64

66

75

52

31

35

20

85 86

80

26

58

25

57

69

84

29

16

56

25

82

36

24 74

55

81

78

13 36

60

68

79 81 84

78

72 78

82 71

73 57

78 72 25 80

45 78

37 62 3 76

82 85 19

87

87 74

83 78

84 76

68

88

80

81 86

76 86

77

75

31

25

74

78

76

26

88

85 17

60

56

68

16 82

69

24

29

33

58

66

75

77

Brittle Structures Map

Structures on this map include joints, brittle faults, and parting fractures. Where parting fractures occur parallel to dikes, veins, axial 

surfaces of folds, shear bands, cleavage, and foliation, the same symbols used on the geologic map (to left) are used on this map. 

PALEOZOIC INTRUSIVE ROCKS

Quartz vein (Permian?)—Quartz veins locally contain variable amounts 

of amphibole, graphite, muscovite, magnetite, epidote, hematite, 

biotite, chlorite, carbonate minerals, and potassium (K-) feldspar. Milky 

to smoky quartz veins are generally tabular and locally irregularly 

shaped, show sharp boundaries with the host rock, and locally contain 

blocky to elongate quartz crystals having euhedral terminations in vugs 

and measuring as much as several centimeters (cm) across along the 

median line. Strike and dip symbols show the location and orientation 

of veins. Measured veins are as much as 1 meter (m) thick. Strikes are 

variable and dips are moderate to steep. Sixty-nine measured veins 

show an average orientation of 130° strike and 60° dip

Pegmatite dike (Permian)—Pink and white, white-weathering, 

coarse-grained, unfoliated, steeply dipping, tabular, muscovite and (or) 

biotite granitic pegmatite dikes. Red strike and dip symbols show the 

location and orientation of 15 pegmatite dikes. Dikes range from 1 to 

80 cm thick. Tabular dikes postdate the foliation. Strikes and dips are 

variable. A Permian age for the pegmatite dikes is inferred from 

regional correlations with similar dikes in Connecticut and Rhode Island 

(Zartman and Hermes, 1987; Wintsch and Aleinikoff, 1987; Zartman 

and others, 1988; Walsh and others, 2007)

NEOPROTEROZOIC INTRUSIVE ROCKS

Hope Valley Alaskite Gneiss—Light-pink, tan- to rusty-weathering or 

light-gray- to white-weathering, medium-grained, equigranular, 

well-foliated plagioclase-quartz-K-feldspar alkali granite gneiss. Contains 

approximately 25 percent plagioclase, 30 to 40 percent quartz, 30 to 

40 percent K-feldspar, and a trace to no biotite. Contains as much as 4 

percent muscovite and as much as 1 percent magnetite. Contains trace 

amounts of garnet, apatite, epidote-clinozoisite, and hematite. 

Recrystallized quartz and feldspar define a faintly visible mineral 

aggregate lineation. Occurs as two map units and as sills shown by 

strike and dip symbols. The map units are exposed at roadcuts along 

Route 146. Ten locations show strike and dip symbols for gently to 

moderately dipping fine-grained sill-like bodies that are subparallel to the 

foliation and as much as 4 m thick (13 locations are included in the 

database). The sills intrude the Ponaganset Gneiss, the Northbridge 

Granite Gneiss, and the tonalite gneiss. Walsh and others (2011) report 

a SHRIMP U-Pb zircon age of 606±5 Ma from the adjacent Grafton 

quadrangle. Two vertical alaskite dikes, 8 cm and 40 cm thick, cut the 

foliation and the Northbridge Granite Gneiss at a roadcut along the 

Route 146 northbound onramp at Exit 3; these two dikes may be 

Permian in age

Northbridge Granite Gneiss

Coarse-grained biotite granite gneiss—Light-gray to light-pink, very light 

gray to yellowish-tan and locally rusty-weathering, coarse-grained and 

locally medium- to coarse-grained, equigranular, weakly to moderately 

well-foliated, biotite-plagioclase-quartz-K-feldspar monzogranite gneiss. 

Contains an average of 33 percent plagioclase, 35 percent quartz, 26 

percent K-feldspar, and 4 percent biotite. Locally the rock is alaskitic 

and contains as much as 6 percent muscovite and 3 percent or less 

biotite. Contains trace amounts of epidote/clinozoisite, magnetite, 

chlorite, apatite, allanite, garnet, hematite, and titanite. Distinguished 

from the Ponaganset Gneiss by its equigranular texture and the lack of 

alkali feldspar megacrysts. Recrystallized quartz and feldspar and aligned 

biotite flakes define the foliation and mineral aggregate lineations. 

Walsh and others (2011) report a SHRIMP U-Pb zircon age of 607±5 

Ma from the adjacent Grafton quadrangle. Contacts with Zpg are 

exposed in several places in the northwestern part of the map area; 

there they are sharp and show that the equigranular Northbridge 

intrudes the inequigranular Ponaganset. Sixteen strike and dip symbols 

show the locations of sills of medium-grained biotite granite gneiss, as 

much as 3 m thick, that intrude the Ponaganset Gneiss and the 

Blackstone Group. One sill occurs within the Zncgm unit at a roadcut 

along Route 122 in Northbridge. Good exposures occur at Exits 2 and 

3 on Route 146

Megacrystic biotite granite gneiss—Light-gray to light-pink, very light gray 

to tan and locally rusty-weathering, coarse-grained and locally mediumto coarse-grained, equigranular to inequigranular, weakly to moderately 

well-foliated, biotite-plagioclase-quartz-K-feldspar monzogranite gneiss 

with recognizable, small, white-weathering, light-pink perthitic microcline megacrysts or augen. Megacrysts are anhedral to subhedral grains 

as much 1 cm long, and their presence is diagnostic of this unit. Rock 

is similar in composition and chemistry to the Northbridge Granite 

Gneiss, unit Zncg, and to the Ponaganset Gneiss, unit Zpg. The texture 

and distribution of the rock suggest that it is transitional between the 

Zncg and Zpg units. A sill of Zncg observed within Zncgm on Route 

122 suggests that Zncgm is older than Zncg. Contacts with adjacent 

units are not exposed. Contains an average of 37 percent plagioclase, 

32 percent quartz, 24 percent K-feldspar, and 5 percent biotite. 

Contains trace amounts of muscovite, epidote/clinozoisite, magnetite, 

chlorite, apatite, allanite, titanite, and hematite. Unit is distinguished 

from the Ponaganset Gneiss by the smaller size and lesser abundance of 

alkali feldspar megacrysts. Recrystallized quartz and feldspar and 

aligned biotite flakes define the foliation and mineral aggregate 

lineations. Good exposures occur east of downtown Whitinsville in 

Northbridge, at Quarry Hill in Uxbridge, and along Route 146 in the 

area between Dunleavey Pond and William Hill in Uxbridge

Fine-grained biotite granite gneiss—Light-pinkish-gray to pink, very light 

gray-weathering to tan-weathering, fine- to medium-grained, largely 

equigranular, weakly to moderately well-foliated and well-lineated, 

biotite-plagioclase-quartz-K-feldspar granite gneiss. Recrystallized quartz 

and feldspar and aligned biotite flakes define the foliation. Contains a 

distinctive mineral lineation defined by elongate spots and streaks of 

aggregated flakes of biotite as much as 1 cm wide and 10 cm long. 

Locally contains small augen of K-feldspar as much as 1 cm across. 

Compositionally similar to Zncg, but finer grained. Contacts with Zpg 

and Zb are exposed in the south-central part of the map area; there 

they are sharp and show that Znfg intrudes the Ponaganset Gneiss and 

the Blackstone Group rocks. One strike and dip symbol shows the 

location and orientation of a sill of Znfg west of Route 98, about 0.4 

kilometers (km) north of the State line. Good exposures occur along 

Crescent Lane in Douglas (street name is not on the base map). A 

xenolith that is lithologically similar to the main body of Znfg occurs 

within Zncg on southbound Route 146 at the eastern edge of the map 

area, and for this reason Znfg is interpreted as being older than the 

main body of Zncg

Ponaganset Gneiss

Megacrystic biotite granite gneiss—Light-gray to light-pinkish-gray, very 

light gray-weathering, medium- to coarse-grained, inequigranular, 

moderately to well-foliated, biotite-K-feldspar-plagioclase-quartz 

monzogranite gneiss with distinct white-weathering, light-pink perthitic 

microcline megacrysts or augen. Megacrysts are anhedral to subhedral 

semi-rectangular grains as much 6 cm long, and their presence is 

diagnostic of this unit. The megacrysts typically consist of recrystallized 

K-feldspar and plagioclase, and locally the plagioclase mantles the alkali 

feldspar cores. Rock is similar in composition and chemistry to the 

Northbridge Granite Gneiss, unit Zncg. Contacts with Zncg are exposed 

in several places in the northwestern part of the map area; there they 

are sharp and show that the equigranular Northbridge intrudes the 

inequigranular Ponaganset. Contains an average of 33 percent quartz, 

32 percent plagioclase, 24 percent K-feldspar, 10 percent biotite, and 

minor to trace amounts of magnetite, muscovite, chlorite, hornblende, 

epidote, clinozoisite, allanite, titanite, apatite, and pyrite. Recrystallized 

quartz and feldspar and aligned biotite flakes define the foliation and 

mineral aggregate lineations. Walsh and others (2011) report a 

SHRIMP U-Pb zircon age of 612±5 Ma from the adjacent Grafton 

quadrangle. Good exposures occur around Reservoir No. 5 in Sutton, 

in Linwood and on Goat Hill in Northbridge, at Douglas High School 

off Davis Street, and at the Ocean State Power (OSP) powerplant 

(labeled “substa” on map) in Burrillville

Megacrystic hornblende-biotite granite gneiss—Medium-gray to pinkish-gray, 

light-gray-weathering, medium- to coarse-grained, inequigranular, 

well-foliated, hornblende-biotite-plagioclase-quartz-K-feldspar monzogranite to granodiorite gneiss with distinct white-weathering, light-pink perthitic 

microcline megacrysts or augen. Megacrysts are anhedral to subhedral 

semi-rectangular grains as much 5 cm long, and their presence, along with 

conspicuous hornblende, are diagnostic features for mapping this rock. 

Contains an average of 30 percent plagioclase, 35 percent quartz, 23 

percent K-feldspar, 8 percent biotite, 2 percent hornblende and 

epidote/clinozoisite, and minor to trace amounts of muscovite, chlorite, 

magnetite, titanite, allanite, and apatite. Recrystallized quartz and feldspar 

and aligned biotite flakes define the foliation and mineral aggregate 

lineations. Hornblende forms both aligned syntectonic mineral grain 

lineations and post-tectonic random crystals oriented in the plane of the 

foliation. Good exposures occur along Whitin Road in Sutton and along 

Davis Street in Douglas 

Tonalite to granodiorite gneiss at Uxbridge—Light- to dark-gray or 

white and black (salt and pepper colored), hornblende-biotite tonalite 

gneiss to biotite granodiorite gneiss. Locally weakly foliated but strongly 

lineated; an L-tectonite. Occurs as several small bodies in the southeastern part of the map area and as one large unit along the eastern border. 

The small bodies tend to be finer grained. Fine-grained rocks are 

hornblende-plagioclase-biotite-quartz metatonalite with minor amounts 

of epidote and trace amounts of K-feldspar, titanite, chlorite, and 

opaque minerals. Contains rounded, dark gray-green to black mafic 

enclaves of epidote-quartz-biotite-hornblende-plagioclase metadiorite in 

the southeastern corner of the map area. Medium-grained rocks consist 

of hornblende-biotite-K-feldspar-quartz-plagioclase tonalite or granodiorite with minor amounts of chlorite and apatite, and trace amounts of 

epidote, titanite, and opaque minerals; and muscovite-biotiteK-feldspar-quartz-plagioclase granodiorite with minor amounts of 

chlorite and trace amounts of epidote, allanite, and apatite. The rock 

contains an average of 29 percent quartz, 45 percent plagioclase, 5 

percent K-feldspar, 13 percent biotite, 4 percent hornblende, and 

minor to trace amounts of epidote/clinozoisite, muscovite, pyrite, 

chlorite, titanite, allanite, and apatite. Medium-grained rocks locally 

contain small white augen, as much as 1 cm across, of recrystallized 

quartz, plagioclase, and K-feldspar. Well-exposed at an abandoned 

quarry on Granite Street in Uxbridge along the eastern edge of the map 

area. May be an older, more mafic phase of the Ponaganset Gneiss

Ironstone quartz diorite of Emerson (1917)—Very dark gray to 

greenish-gray or black, locally rusty-weathering, fine- to 

medium-grained, weakly foliated, irregularly fractured, 

biotite-quartz-plagioclase-hornblende quartz diorite. The rock contains 

an average of 7 percent biotite, 11 percent quartz, 27 percent 

plagioclase, 52 percent hornblende, and minor to trace amounts of 

epidote, apatite, chalcopyrite, pyrite, and chlorite. The rock occurs in 

one unit mapped at outcrops located between Elmwood Avenue and 

East Ironstone Road in Uxbridge along the eastern edge of the map 

area, but better exposures occur in the adjacent Blackstone quadrangle 

in a cornfield north of East Ironstone Road, just north of the State line, 

and those outcrops are shown on this map. The unit intrudes the 

Blackstone Group and is bordered by a zone of migmatitic rocks (Zbm). 

Unit named by Emerson (1917) and mapped at Ironstone by McKniff 

(1964), and interpreted here as correlative with rocks exposed at the 

type locality about 1.5 km northeast of where Card Machine Brook 

exits the Uxbridge quadrangle

NEOPROTEROZOIC METASEDIMENTARY ROCKS

Blackstone Group

Migmatitic plagioclase porphyroblast gneiss—Gray, fine- to 

medium-grained, weakly to strongly foliated, epidotebiotite-quartz-plagioclase granofels to gneiss characterized by abundant 

white plagioclase porphyroblasts as much as 5 millimeters (mm) across 

and discontinuous, contorted layering. The rock contains 

approximately 2 percent epidote, 16 percent biotite, 30 percent quartz, 

50 percent plagioclase, and minor to trace amounts of chlorite, apatite, 

allanite, and opaque minerals. Locally contains disarticulated layers and 

boudins of biotite schist, quartzite, and rare amphibolite; contains 

sheet-like layers of biotite-quartz-feldspar tonalitic to granodioritic gneiss 

and biotite-quartz-plagioclase-hornblende dioritic gneiss interpreted as 

intrusive sills. Occurs in a contact metamorphic zone in the Blackstone 

Group around the Ironstone quartz diorite. Also observed at one place 

on Route 146 northbound, south of Mill Street, adjacent to the tonalite 

and granodiorite gneiss unit (Zt)

Schist and quartzite—Undifferentiated, interlayered, locally rusty- and 

slabby-weathering, carbonaceous quartz-plagioclase-biotite schist and 

biotite-plagioclase-quartz quartzite. Ratio of schist to quartzite is highly 

variable and ranges from mostly schist with approximately 10 percent 

quartzite to vice versa. Schist is a very dark gray to gray, and dark-gray 

to black-and-white-laminated, quartz-plagioclase-biotite rock with minor 

amounts of muscovite and chlorite, and trace amounts of epidote, 

hornblende, apatite, titanite, and zircon. Quartzite is a very light gray to 

white, locally tan-weathering, biotite-plagioclase-quartz rock with as 

much as 5 percent biotite, 15 percent plagioclase, and 75 percent or 

more quartz. Locally, along the margins of the plutonic rocks, the schist 

contains garnet, plagioclase, and (or) kyanite porphyroblasts as much as 

10 mm across. At one location northeast of Joel’s Pond in Uxbridge, 

the schist contains porphyroblastic quartz-garnet knots (as much as 10 

cm long and 2 cm across) that are elongated parallel to the L2 mineral 

lineation. Kyanite was observed only in thin section. Schist xenoliths 

found in the granitic rocks consist of titanite-epidotequartz-plagioclase-biotite rock with variable amounts of hornblende and 

trace amounts of chlorite, muscovite, apatite, zircon, and opaques. The 

Blackstone Group locally contains calc-silicate rocks, and those locations 

are indicated on the map. Calc-silicate rocks include light-gray to 

dark-gray or black, carbonaceous, rusty-weathering, epidotequartz-plagioclase-tremolite schist with minor amounts of biotite and 

trace amounts of titanite, hematite, and graphite; dark-green 

titanite-epidote-plagioclase-quartz-hornblende-biotite schist; gray-green 

tremolite-biotite-plagioclase-quartz quartzite with trace amounts of 

titanite and epidote; pale-green quartz-plagioclase-diopside-tremolite 

gneiss with minor amounts of titanite and trace amounts of calcite; and 

very light gray to white, chlorite-biotite-muscovite-quartz-plagioclase 

granofels with dark-green to pink, retrograded garnet clots, as much as 

1 cm across, consisting of quartz, biotite, chlorite, and garnet. 

Weathered calc-silicate schists display subrounded holes as much as 10 

cm across. Good exposures of the Blackstone Group occur at roadcuts 

along Route 146 north of Exit 2, and at outcrops north of Route 16 in 

the vicinity of the Douglas-Uxbridge town line

DESCRIPTION OF MAP UNITS

[Major minerals are listed in order of increasing abundance]

BBfz – Bloody Bluff fault zone

CNf

BBfz

OXFORD

GRAFTON

UXBRIDGE BLACKSTONE

THOMPSON CHEPACHET GEORGIAVILLE

MILFORD WORCESTER

SOUTH

Merrimack zone

Nashoba zone

Avalon zone

CNf – Clinton Newbury fault

Fault

Figure A.—Map showing 7.5-minute quadrangle 

locations and generalized regional structure.

Mass.

Conn. R.I.

Milford 

antiform Oxford 

anticline

A

4000

2000

3000

4000

1000

3000

1000

2000

FEET

4000

2000

3000

4000

1000

3000

1000

2000

FEET

SEA LEVEL 0 0

4000

2000

3000

4000

1000

3000

1000

2000

FEET

SEA LEVEL

4000

2000

3000

4000

1000

3000

1000

2000

FEET

A'

B B'

1000 feet = 305 meters

Surficial deposits not shown

1000 feet = 305 meters

Surficial deposits not shown

NO VERTICAL EXAGGERATION Apparent dip of dominant foliation NO VERTICAL EXAGGERATION

A T

T A

Apparent dip of dominant foliation

Southwick Brook

Dunleavey Brook

State Route 146

Linwood Pond

State Route 122

Blackstone River

Mass.–R.I. State boundary

Round Top Brook

Cedar Swamp

Aldrich Brook

A'

A

B

B'

Base from U.S. Geological Survey, 1969

Photorevision as of 1979

Polyconic projection. 1927 North American Datum

10,000-foot grid ticks based on Massachusetts coordinate 

system, mainland zone, and Rhode Island coordinate 

system.

1,000-meter Universal Transverse Mercator grid ticks, 

zone 19, shown in blue

Geology mapped in 2007–09

Map compiled from a GIS database using 

ArcGIS version 9.3. Topographic base produced 

by scanning photo positive separates at 400 dpi. 

Cartography compiled in Adobe Illustrator, 

version CS4.

SCIENTIFIC INVESTIGATIONS MAP 3295

Explanatory pamphlet accompanies map

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY 

Prepared in cooperation with the

COMMONWEALTH OF MASSACHUSETTS

MASSACHUSETTS GEOLOGICAL SURVEY

BEDROCK GEOLOGIC MAP OF THE UXBRIDGE QUADRANGLE, WORCESTER COUNTY, MASSACHUSETTS, AND PROVIDENCE COUNTY, RHODE ISLAND

By

Gregory J. Walsh1

1U.S. Geological Survey, Montpelier, VT 05601.

2014

1 MILE

CONTOUR INTERVAL 10 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 .5 0 1 KILOMETER

SCALE 1:24 000

1 1/2 0 1 MILE

CONTOUR INTERVAL 10 FEET

NATIONAL GEODETIC VERTICAL DATUM OF 1929

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 .5 0 1 KILOMETER

SCALE 1:24 000

MAGNETIC

1 1/2 0

 NORTH

TRUE NORTH

14 / ° 1 2

MAP LOCATION

MASSACHUSETTS

RHODE ISLAND

Any use of firm, trade, or product names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government

For sale by U.S. Geological Survey, Box 25286, Denver Federal Center, Denver, CO 80225; 

http://store.usgs.gov; 1–888–ASK–USGS (1–888–275–8747)

Suggested citation: Walsh, G.J., 2014, Bedrock geologic map of the Uxbridge quadrangle, Worcester 

County, Massachusetts, and Providence County, Rhode Island: U.S. Geological Survey Scientific 

Investigations Map 3295, 1 sheet, scale 1:24,000, and 36 p. pamphlet, http://dx.doi.org/10.3133/sim3295.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3295

e

e

e

Ag

UX–1434

UX–1025 UX–1434

GR–283

UX–1425

UX–1001-A

UX–1001

UX–1043

UX–1398

UX–1042

UX–1092

UX–1157-A

UX–1105

UX–1237

UX–1276

UX–1274

UX–1591

UX–1087

UX–1082

UX–1179

UX–1148

UX–1291

UX–1121-A UX–1116

UX–1122

UX–1016

UX–1134

UX–1112

UX–1004

EXPLANATION OF MAP SYMBOLS

Contact—Approximately located; dotted where concealed by water

Outcrops—Areas of exposed bedrock or closely spaced contiguous

 bedrock exposures examined in this study; dashed line surrounds 

outcrops that consist of closely spaced loose blocks where rock type 

was identified, but no structural measurements were made

FAULTS

Mylonitic fault—Approximately located; dotted where concealed by 

water. Parallel to S3; paired arrows indicate relative motion where 

known; U, upthrown side; D, downthrown side. In cross section B–B': 

T, toward observer; A, away from observer

FOLDS

[Showing trace of axial surface, direction of dip of limbs, and direction of plunge

where known or inferred]

Approximate trace of the Milford antiform (F3, Alleghanian)

PLANAR FEATURES

[Symbols may be combined; point of intersection shows location of measurement]

Strike and dip of brittle features—Outcrop-scale brittle fault. Movement 

sense indicated by N, normal; R, reverse; LL, left lateral; U, upthrown 

side; D, downthrown side

Inclined

Vertical

Joints, joint zones, and joint sets—Shown only on the Brittle Structures Map

Inclined

Vertical

Strike and dip of pegmatite dike (Permian)

Inclined

Vertical

Strike and dip of quartz vein (Permian?)

Inclined

Vertical

Strike and dip of alaskite dike (Permian?)

Vertical

Strike and dip of dike or sill of alaskite (Zhv) (Neoproterozoic)

Inclined

Strike and dip of sill of Znfg (Neoproterozoic)

Inclined

Strike and dip of sill of Zncg (Neoproterozoic)

Inclined

Strike and dip of deformed relict foliation (S1)—Parallel to bedding in 

the Blackstone Group; probably Neoproterozoic

Inclined

Strike and dip of dominant foliation (S2)—A schistosity in the 

Blackstone Group and a gneissosity in the intrusive rocks; probably 

Alleghanian

Inclined

Vertical

Strike and dip of mylonitic foliation—Parallel to S2 in zones a few 

centimeters to a few meters thick

Inclined

Strike and dip of mylonitic foliation—Parallel to S3 in zones a few 

centimeters to a few meters thick

Inclined

Crenulation cleavage S3—Mostly observed in the Blackstone Group; 

probably Alleghanian

Inclined

Strike and dip of axial surface of F2 minor fold—Parallel to S2

foliation. Tight to isoclinal, locally rootless folds in the Blackstone 

Group; probably Alleghanian

Inclined

Strike and dip of axial surface of F3 minor fold—Open to tight, late 

fold mostly observed in the Blackstone Group; probably Alleghanian

Inclined

Vertical

Strike and dip of F3 shear band—Shear bands or kink bands locally 

associated with extensional veins or pegmatites; probably Alleghanian

Inclined

Strike and dip of F4 minor fold—Open, late fold that deforms S3, 

observed at one location north of Whitinsville; probably Alleghanian

Inclined

LINEAR FEATURES

[Symbols may be combined with symbols for planar features; point

of intersection shows location of measurement]

Trend of glacial striations or grooves

Trend and plunge of slickenlines on brittle fault

Bearing and plunge of L2 mineral lineation—Aggregate lineation or 

grain lineation associated with the dominant foliation (S2); consists of 

quartz, biotite, amphibole, or K-feldspar

Bearing and plunge of L3 mineral lineation—Aggregate lineation or 

grain lineation associated with S3 shear bands or thin mylonite zones; 

consists of quartz, biotite, K-feldspar, or amphibole 

Bearing and plunge of F2 minor fold axis—Intersection lineation 

between S1 and S2 or fold axis of tight, isoclinal, or rootless fold 

associated with the dominant foliation (S2)

Bearing and plunge of F3 minor fold axis—Intersection lineation between 

S2 and S3 crenulation axis or fold axis of late, open to tight fold

Bearing and plunge of F4 minor fold axis—Fold axis of late open fold

OTHER FEATURES

Geochemistry sample location

Abandoned granite quarries—Quarried bedrock; quarried erratics along 

Locust Avenue in Uxbridge

Abandoned mine—Scadden Silver Mine, about 1 km west of Chockalog 

Pond in southeast Uxbridge

Location of small amphibolite bodies within Zncg, Zpg, and Zbm

Location of calc-silicate rocks within Zb—Shown as calc-silicate + Zbm

at one place along Route 146 east of Happy Hollow Brook in Uxbridge

Location of xenolith of Zb

Location of xenolith of Znfg

Location of conspicuous garnet porphyroblasts—Shown as grt+ky 

where kyanite was identified in thin section

Blackstone

Group

METASEDIMENTARY

ROCKS

INTRUSIVE ROCKS

PALEOZOIC INTRUSIVE ROCKS

CORRELATION OF MAP UNITS

AVALON

ZONE

PERMIAN

NEOPROTEROZOIC

Quartz vein

Pegmatite dike

Alaskite dike

?

?

Zpg

Zpg

Zpg

Zb

Zncgm

Zncg

Zpg

Zncg

Zt

Zb

Zncg

Zb

Zb

Zb

Zphg

Znfg

Zncg

Zncg

Zpg

Zbm

Zt

Zt

Zncgm

Ziqd

Zpg

Zpg

Zhv

Zncgm

Zb

Zhv

Zt

Zt

Zt

Zphg

Zb

Znfg

Znfg

Zpg

Zpg

Zncgm

Zpg

Zpg

Zncgm

Zncg

Zpg

Zncg

Zt

Zb

Zb

Zb

Zb

Zphg

Znfg

Zncg

Zncg

Zpg

Zbm

Zt

Zt

Zpg

Zhv

Zncgm

Zb

Zhv

Zt

Zt

Zt

Zphg

Zb

Znfg

Zpg

Zncgm

Zb

Zncg

Zphg Zpg

Ziqd

Zt

Zb

Zbm

Zncgm Znfg

Zhv

Zb

Zb

Zb

Zb Zb Zb

Zt

Zb

Zhv

Zpg Zpg Zpg

Zpg

Zpg

Zhv

Zpg Zpg Zpg Zpg

Zncg Zncg Zncg

Znfg

Zphg Zncgm Zncg Zncg Znfg

Zncgm

Zncgm SURFACE SURFACE

Zncg

Zncgm

Zpg

Znfg

Zpg

Zb

Zbm

Ziqd

Zhv

Zncg

Zncgm

Znfg

Zpg

Zphg

Zt

Zphg

Ziqd

Zncg

APPROXIMATE MEAN

DECLINATION, 2014