Savin Hill Fault

Mount Hope Fault

Newton Quadrangle Boston South Quadrangle

71o 07’ 30” W

71o 00’ W42o 15’ N

42o 22’30” N

~609 Ma

~593 Ma(MT08-01)

<596 Ma (MT99-4)

<595 Ma (MT04-20)

~584 Ma (MT03-09A)

~585 Ma (BOS22A)

~597 Ma

LYNN-MATTAPAN VOLCANICCOMPLEX (597-593 Ma) includ-ing N, Neponset Gorge Conglom

N

Undi�erentiated argillite

CAMBRIDGE ARGILLITE (<570 Ma)BOSTON BAY GROUP

SEDIMENTARY AND VOLCANIC ROCKS

ROXBURY CONGLOMERATE

Franklin Park member

Undi�erentiated Brookline-Dorchester-Squantum membersincluding B, Brighton IgneousSuite (585 Ma)

WESTWOOD GRANITE (599 Ma)

DEDHAM GRANITE (609 Ma)

INTRUSIVE IGNEOUS ROCKS

B

<599Ma (MT10-12)

U-Pb zircon date

SYMBOLSInclined, horizontal bedding Anticline, syncline Fault

C T, City Tunnel Tunnel alignment

C T E, City Tunnel Extension

M D T, Main Drainage TunnelD T, Dorchester Tunnel

25

~ 585 Ma Entries with sample #’s fromThompson et al., 2014; othersare previoulsy published)

5 Field trip stop for2014 NEIGC Trip B-2

M D T

C T E

D T

C T

1

2

4

3

5

6

7

BEDROCK GEOLOGIC MAP OF THE BOSTON BASIN & ENVIRONS

(after Thompson et al., 2014)