Bedrock Geologic Map of the Hanover 7.5' Quadrangle, New Hampshire N
" 72°22'30"W 72°20'0"W 72°17'30"W 72°15'0"W 0 ' N 5 " 4 0 ° ' 3 5 4 4
° 3
B' 4 DESCRIPTION OF MAP UNITS EXPLANATION OF
INT RU SIVE AND FAU L T ROCKS MAP SYMBOLS Kjd Mafic dikes (Mesozoic) — No Mesozoic diab ase dikes were foun d, Con tac t Beddin g So
although L yon s (1958) reported on e on Crafts Hill an d several in trudin g the L eb an on gran ite. (c ertain ) Foliation Sn
Con tac t md Metadiabase sills and dikes (unknown age) — A few m etadiab ase dikes of un kn own age (m d) c on sistin g of fin e- to m edium -grain ed horn b len de gn eiss (in ferred) in trude the Partridge Form ation . T heir exten t is lim ited to on e or a few Foliation S1 Con tac t outc rops.
(c on c ealed) 35
In tersec tion 35
Amphibolite (unknown age) — Am phib olite, likely m etagab b ro, c rops out Oo9B lin eation 38 as sills within the m etavolc an ic s west of Bald Hill an d in a larger b ody alon g Fault the c rest of Crafts Hill. T he m assive, b loc ky- an d b rown -weatherin g roc k Min eral
Min eral lin eation 37 seem s to b e in terc alated with quartz diorite alon g the east side of Crafts Hill.
isograd
T his b ody c on tin ues south all the way to a n ear-outc rop at an old dam site on 36
the Masc om a River upstream from the Route 4 b ridge n orth of the airport. (in ferred) Fold axis
Rum b le (pers. c om m ., 2015) reported that L yon s had suggested to a
t c on trac tor that the am phib olite m ight serve as road m etal, b ut the roc k was 29 s
g 38
so tough that it apparen tly b roke the testin g equipm en t.
39
27 ORDOVICIAN OL IVERIAN PL U T ONIC ROCKS
34 Granite (Ordovician) — T he gran ite (Oo1b ) in the c en ter of the L eb an on
Oo1b
Dom e is a pin kish gray, m edium -grain ed, weakly to n on -foliated b iotite Oo9B
gran ite, whic h has b een quarried for dim en sion ston e. 49
27
29
Oo3A Tonalite/quartz diorite (Ordovician) — Quartz diorite or ton alite (Oo3A) 23 m an tles the gran ite an d is well exposed on Starr Hill in L eb an on an d in the
23
Masc om a River b etween old m ills n orth an d south of Route 4. T he quartz
diorite is a dark to m edium gray, m edium -grain ed b iotite roc k, m ore stron gly
Oo1b N
" foliated alon g its c on tac ts with the Partridge Form ation . Valley et al. (2015) 0 3 N ' " 2 0
4 reported a U /Pb age on zirc on s from the gran ite in the En field Quadran gle as 3 ° '
3 2 4 4 °
448+/-5 Ma, an d from the quartz diorite n ear the Poverty L an e/Route 4 40 3 4
39 in tersec tion in Han over Quadran gle as 445+/-7 Ma. Field relation s suggest 44
that the gran ite is youn ger. T he Route 4 road c ut also c on tain s a xen olith of Partridge felsic volc an ic s parallel to foliation within the quartz diorite. At 39 Ops
the I-89/Route 12A in tersec tion , n orth of the Verizon W ireless b uildin g, a
white-weatherin g ton alite that in trudes the Am m on oosuc Volc an ic s was 20
dated at 466+/-8 Ma (Valley et al., 2015). T his is part of the sm all pluton )
shown b y L yon s (1955) as a b ody of L eb an on gran ite, b ut it is c learly older n o i
than the dom e roc ks, an d together with ton alite in Plain field (U /Pb 475+/-5 t
Oo6 a Ma, Valley et al., 2015), provides som e c on strain ts on the m in im um age of T r L the Am m on oosuc . e U
g A g F Oo6 Quartz Diorite a
x E
l MET ASEDIMENT ARY AND MET AVOL CANIC ROCKS C Oa a U c i
S
Op Partridge formation undifferentiated (Ordovician) — T he Partridge t
O Form ation in this quadran gle c on sists of sc hist (Ops) with felsic r 30 e
O 40 V m etavolc an ic len ses an d layers (Opf). N
O o
M Ops Sulfidic schist member — Sc hists in the Partridge are rusty-weatherin g, N (
M
b lac k to dark gray, graphitic an d sulfidic fin e- to c oarse-grain ed sc hist. T hey '
A
are c oarser away from the L eb an on Dom e, for exam ple on the west slopes of B
-
Oak Hill, where c lum ps of b iotite (pseudom orphs after staurolite?) an d Oo1b B
loc ally staurolite itself join tin y garn ets as porphyrob lasts. Closer to the
dom e the Partridge is overall fin er-grain ed b iotite sc hist, loc ally with garn et. n o i
T he staurolite isograd tren ds n ortheast toward a well defin ed c on tin uation in t
the L ym e Quadran gle (T hom pson , 2008). (A study of feldspar c om position s c e S
in the m afic roc ks would c on trib ute to loc atin g the c om parab le am phib olite s
fac ies lim its.) s
47 o r
Opf Felsic volcanics member — Felsic m etavolc an ic s of the Partridge ran ge LEBANON C
from rusty weatherin g, light gray fin e-grain ed sulfidic felsite to rusty,
e 31 DOME m edium -grain ed b iotite feldspar-studded gn eiss. Sulfide prospec ts are v
53 i c om m on in this un it, espec ially n ear Farn um Hill in the North Hartlan d t e
Quadran gle, where a series of tren c hes an d pits were dug in the 1880’s r
42 42 50 p
r N " (L yon s, 1958) in m etavolc an ic roc ks an d what appears to b e a quartz diorite 0
' e N
0 " t 4 0 ° sill. Material in spoils piles c on sists of vein quartz an d gossan -like m aterial. 65 '
3 0 4 n 4 °
3
I
Ab out 1500 m eters n orth, in the Han over Quadran gle n orth of the Old Kin gs 4
t
s
Highway, an other tren c h was foun d durin g this study, where the roc ks are so
49 g
ric h in pyrrhotite that c om pass b earin gs were disturb ed. 48
52
40 Oa Ammonoosuc Volcanics undifferentiated (Ordovician) — Ran ge from Opf 49
dark green -b lac k fin e- to m edium -grain ed horn b len de gn eisses to b lac k an d Oo9B
white m etavolc an ic s with distin c t altern atin g horn b len de-ric h an d feldspathic
layers in the Han over quadran gle. T he un it is well exposed on the 56
60 Dartm outh College c am pus, where a sill of white-weatherin g feldspar-garn et 45 64
gn eiss with horn b len de fasc ic les lies parallel to m ore typic al m afic roc ks.
A Som e layers c on tain epidote-ric h len ses up to 30 c en tim eters lon g, som e of
Opf 52
57 whic h have pillow-like shapes. T he Am m on oosuc is also exposed in a sm all
quarry east of Route 10 n ear Cam p Brook, on Cham b ers Road just south of 73 the Han over lin e, an d from W ilder Dam south alon g a ridge east of Route 10
to the outskirts of W est L eb an on , where it disappears b en eath Quatern ary c over. T he on ly exposures south of there are at the I-89/Route 12A 59 in tersec tion (disc ussed further b elow) an d on Poverty L an e at the south
b order of the quadran gle, where it is a well foliated, c oarse-grain ed Oo9B am phib ole-epidote-c hlorite gn eiss.
Dg/Dgm Gile Mountain Formation/ Meetinghouse Slate Member (Devon ian) —
No outc rop presen t in study area, un derlies youn ger un its.
Oa Ops
Oa
82
51
40 52 75
Oo3A Opf
Oo6
Ops
67 N
" 68 57 55
0 3 N ' "
7 B 71 md 87 0 3 77 3 ° ' 3 7
4 A' 3 ° 3 4 72°22'30"W 72°20'0"W 72°17'30"W 72°15'0"W Scale 1:24,000 Topographic basemap from the USGS 1998 Hanover 7.5' quadrangle Projection: North American Datum 1983 New Hampshire State Plane Feet. 0 1,450 2,900 5,800 1000 meter grid in UTM zone 18 North, Contour Interval 20 ft NHGS Open-File Disclaimer: This map and the accompanying legend(s) are understood to be Feet open-file products. They are draft versions of an unpublished report and represent mapping Hillshade produced from high resolution (1 meter) LiDAR data 0 0.5 1 2 progress at the time of completion. Newer information may exist. If you have questions, please acquired from 2015 Connecticut River Joint Project contact the New Hampshire Geological Survey (NHGS) at: [email protected] or (603) 271-1976 0 1 Mi2les 4
Kilometers LYME
HANOVER ENFIELD
NORTH NORTH HARTLAND GRANTHAM Bedrock Geologic Map of the Interpretive Cross Section A - A' (No Vertical Exaggeration) Hanover 7.5' Quadrangle, New Hampshire
Geology b y Peter J. T hom pson , 2014 Digital Com pilation b y Sarah W . Baker an d Gregory A. Barker, 2016 New Ham pshire State Geologist: Frederic k H. Chorm an n
Bedroc k Geologic Map Open -File Series GEO-091-024000-BMOF
This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under StateMap award number G14AC00427
New Hampshire Geological Survey NH Department of Environmental Services 29 Hazen Drive, P.O. Box 95 Concord, NH 03302-0095 Phone: 603-271-1976 E-mail: [email protected]