Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
For permission to copy, contact [email protected]© 2011 Geological Society of America
Cenozoic tectonic history of the Himachal Himalaya (northwestern India) and its constraints on the formation mechanism of the Himalayan orogen
A. Alexander G. Webb1,2,*, An Yin2,3, T. Mark Harrison2, Julien Célérier4, George E. Gehrels5, Craig E. Manning2, and Marty Grove21Department of Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana 70803, USA2Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA3Structural Geology Group, China University of Geosciences Beijing, Beijing 10085, People’s Republic of China4Research School of Earth Sciences, Australia National University, Canberra, ACT 2601, Australia5Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
1013
Geosphere; August 2011; v. 7; no. 4; p. 1013–1061; doi: 10.1130/GES00627.1; 17 fi gures; 4 tables; 7 supplemental fi les.
ABSTRACT
A central debate for the evolution of the Himalayan orogen is how the Greater Himalayan Crystalline complex in its core was emplaced during the Cenozoic Indo-Asian collision. Addressing this problem requires knowledge of the structural relationship between the South Tibet detachment fault (STD) and the Main Central thrust (MCT) that bound these rocks from above and below. The fault relationship is exposed in the Himachal Himalaya of northwestern India, where they merge in their updip direction and form a frontal branch line that has been warped by subsequent top-to-the-southwest shear deformation. To elucidate how the two major crustal-scale faults evolved in the western Himalaya, we conducted integrated geologic research employing fi eld mapping, pressure-temperature (P-T) analy-ses, U-Pb zircon geochronology, trace and rare earth element (REE) geochemistry, and thermochronology. Our fi eld study reveals com-plex geometric relationships among major thrusts with large-magni-tude shortening within each thrust sheet. Three successive stages of top-to-the-southwest thrust development are recognized: (1) imbri-cate stack development, (2) translation of large thrust sheets along low-angle detachments and backthrusting along the STD, and (3) development of duplex systems via underplating. This kinematic pro-cess can be quantifi ed by our new analytical data: (1) P-T determina-tions show 7–9 kbar and 450–630 °°C conditions across the STD. The lack of a metamorphic discontinuity across the fault is consistent with a backthrust interpretation. (2) U-Pb zircon geochronology yields ca. 830 Ma and ca. 500 Ma ages of granitoids in the MCT hanging wall, ca. 1.85 Ga ages of granitic gneisses in both the MCT hanging wall and footwall, and 8–6 Ma ages of granitic pegmatites in the MCT footwall. These ages help defi ne regional chronostratigraphy, and the youngest ages reveal a previously unknown intrusion phase. (3) Trace element and REE geochemistry of 1.85 Ga, 830 Ma, and 500 Ma gran-itoids are characteristic of remelted continental crust, constraining the protolith tectonic setting. (4) U-Pb geochronology of detrital zir-con reveals that siliciclastic sedimentary sequences above the STD, below the MCT, and between these two faults have similar age spec-
tra with Neoproterozoic youngest age peaks. This result implies that the STD and MCT each duplicated the same stratigraphic section. (5) Th-Pb geochronology of monazite included in MCT hanging-wall garnet yields Paleozoic and early Tertiary ages, indicating Paleozoic and early Tertiary metamorphism in these rocks. (6) The 40Ar/39Ar thermochronology of the K-feldspar from southern MCT hanging-wall rocks evinces cooling below 220–230 °°C ca. 13–19 Ma or later, constraining the thrust development history. We use these results to derive a tectonic model of crustal shortening across the Himachal Himalaya involving early thickening, tectonic wedging emplacement of the Greater Himalayan Crystalline complex between the MCT and STD, and continued growth of the Himalayan thrust wedge by accre-tion of thrust horses from the Indian footwall.
INTRODUCTION
The fi rst-order architecture of the Himalayan orogen is expressed by two major north-dipping faults bounding a high-grade complex in the orogenic core (e.g., Argand, 1924; LeFort, 1996; Yin and Harrison, 2000; DeCelles et al., 2002; Yin, 2006). A central issue with regard to the Ceno-zoic Himalayan development is how the metamorphic core, the Greater Himalayan Crystalline complex, has been emplaced to its current position (LeFort, 1975; Burchfi el and Royden, 1985; Grujic et al., 1996; Nelson et al., 1996; Webb et al., 2007). Resolving this issue requires knowledge of the kinematic history of each bounding fault, i.e., the Main Central thrust (MCT) below and South Tibet detachment (STD) above, and the structural relationship between these faults.
The regional signifi cance of the MCT as a major Cenozoic shorten-ing structure has been recognized since the classic work of Heim and Gansser (1939) (Fig. 1) (see also Le Fort, 1975; Upreti, 1999; Hodges, 2000; DiPietro and Pogue, 2004). In contrast, the STD was discovered much later (Burg et al., 1984; Burchfi el et al., 1992). The STD is gen-erally north- dipping, features alternating top-to-the-south and top-to-the-north shearing, and juxtaposes the largely low-grade Tethyan Himalayan Sequence on top of the Greater Himalayan Crystalline complex (e.g., Patel et al., 1993; Hodges et al., 1996). Excepting the top-to-the-south
Webb et al.
1014 Geosphere, August 2011
shear indicators, these records are consistent with a normal fault inter-pretation. The apparent presence of a major normal fault within the con-tractional orogenic setting of the Himalaya has led to intense debate over the tectonic origin and dynamic role of the STD (e.g., Burg et al., 1984; Burchfi el and Royden, 1985; Yin, 1989; Hodges et al., 1992, 1996; Brown and Nazarchuk, 1993; Patel et al., 1993; Yin et al., 1994, 1999; Lee et al., 2000; Grujic et al., 2002).
Current hypotheses for the emplacement of the Greater Himalayan Crystalline complex offer different solutions to this problem (Fig. 2). Ver-tical wedge extrusion models show the STD as a normal fault at the crust of a Coulomb orogenic wedge (e.g., Burchfi el and Royden, 1985; Grujic et al., 1996). Models of southward middle-crustal channel fl ow interpret the STD as a backstop normal fault allowing the extrusion of channel rocks linked to focused denudation along the Himalayan topographic front (e.g., Nelson et al., 1996; Beaumont et al., 2001). In tectonic wedging models, the STD acts largely as a subhorizontal backthrust off of the MCT, with its top-to-the-north shear surfacing as the Great Counter thrust system (Webb et al., 2007). These competing models for the emplacement of the Greater
Himalayan Crystalline complex make different predictions (Table 1) (Fig. 2). First, the wedge extrusion model (Burchfi el and Royden, 1985) requires local extension over the highest region of the Himalaya and sug-gests that slip may be focused along a preexisting lithologic contact (Burg et al., 1984; Burchfi el and Royden, 1985). Second, both wedge extrusion and channel fl ow models require rapid erosion of the Tethyan Himalayan Sequence and exposure of the Greater Himalayan Crystalline complex during the main motion along the MCT and STD in the Early and Middle Miocene (Nelson et al., 1996; Beaumont et al., 2001; Hodges et al., 2001). In contrast, the tectonic wedging model predicts that the Tethyan Hima-layan Sequence was preserved above the Greater Himalayan Crystalline complex during STD motion. Third, the wedge extrusion model predicts the STD and MCT merge downdip to the north, the channel fl ow model predicts them to be largely subparallel, and the tectonic wedging model predicts them to merge updip to the south.
As the relationship between the STD and MCT is central in differ-entiating these models, fi eld tests must be conducted in regions where their relationships can be established. This requirement motivates our
SHIMLA
KATHMANDU
20oN
90oE80oE
20oN
20oN
N
TIBETAN PL
ATEAU
INDIA
Zanskar shear zone
South Tibet detachment
70°E 80°E 90°E 100°E
30°N
20°N70°E
30°N
Quaternary
Tethyan Himalayan Sequence: < Precambrian - Cambrian < Ordovician - Mesozoic
Late Cretaceous - Tertiary
Greater Himalayan Crystalline complex
Lesser Himalayan Crystalline Nappes (commonly interpreted as frontal Greater Himalayan Crystalline complex)
Lesser Himalayan Sequence
Asian and Indo-Burman plate rocks
Indian Craton
Main Central thrust (MCT)
South Tibet detachment (STD)
Ophiolite / Ophiolitic melange
Great Counter thrust
Figure 3.
Figure 1. Simplifi ed tectonic map of the Himalayan orogen. The dashed line denotes the Indian state of Himachal Pradesh, the box denotes the boundaries of Figure 3. Based on: Academy of Geological Sciences China (1975), Acharyya et al. (1986), Acharyya (1997), Biju-Sekhar et al. (2003), Buick et al. (2006), Deb et al. (2001), Ding et al. (2001), DiPietro and Pogue (2004), Frank et al. (1973, 1995), Fuchs and Linner (1995), Gilley et al. (2003), Jadoon et al. (1994), Johnson et al. (2001), Kapp et al. (2003), Khan et al. (2004), Leloup et al. (1995), Mitchell (1993), Mitchell et al. (2007), Murphy and Copeland (2005), Pilgrim and West (1928), Rao et al. (2000), Robinson (2005), Robinson et al. (2007), Robinson et al. (2006), Socquet and Pubellier (2005), Srikantia and Sharma (1976), Steck (2003), Thakur (1998), Thiede et al. (2006), Upreti (1999), Valdiya (1980), Vannay and Grasemann (1998), Vannay et al. (2004), Webb et al. (2007), Windley (1988), Yeats and Hussain (1987), Yin and Harrison (2000), Yin (2006); see also references cited in Figure 3.
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1015
geologic investigation of the Himachal Himalaya in northwest India (Fig. 1), where contact relationships between the MCT and STD have been proposed and locally tested (Thakur, 1998; Yin, 2006; Webb et al., 2007). This region loosely marks the transition from the western to the central Himalaya, which are in part distinguished by drastically differ-ent preservation of the Tethyan Himalayan Sequence above the STD. In the central Himalaya, the Tethyan Himalayan Sequence has been largely eroded away, leaving the MCT and STD exposed as subparallel structures above and below the Greater Himalayan Crystalline complex (e.g., Hodges et al., 1996; DeCelles et al., 2001). In contrast, the Tethyan Himalayan Sequence is well preserved in the western Himalaya. In the Himachal Himalaya, an along-strike variation of MCT juxtaposition (i.e., from a Greater Himalayan Crystalline complex over Lesser Himalayan Sequence relationship in the east to a Tethyan Himalayan Sequence over Lesser Himalayan Sequence relationship in the west) can be directly observed (Fig. 3) (Thakur, 1998; Steck, 2003; DiPietro and Pogue, 2004). Besides this advantage, the stratigraphic units above and below the MCT are correlative in Himachal (e.g., Miller et al., 2001; Myrow et al., 2003), allowing assessment of the original confi guration of the northern Indian margin before the Cenozoic Indo-Asian collision. This correlative strati-graphic relationship across the MCT in the Himachal Himalaya contrasts strongly with the geology of the central Himalaya of Nepal, where rock units across the MCT differ drastically in age and provenance (Parrish and Hodges, 1996; DeCelles et al., 2000).
In this study we compiled a regional geologic map that combines infor-mation from existing literature and our new geological and analytical data collected via structural, geochemical, thermobarometric, and U-Th-Pb geochronologic and 40Ar/39Ar thermochronologic analyses of key areas and critical samples. We integrate our new results into a tectonic model that shows that the construction of the Himachal Himalaya was mainly accomplished by footwall accretion and vertical thrust stacking of Pro-terozoic strata of the northern Indian passive margin sequence, consistent with a tectonic wedging emplacement of the Greater Himalayan Crystal-line complex.
LITHOLOGIC UNITS
Major lithologic units in the study area include the Cretaceous and Cenozoic Sub-Himalayan Sequence, the Proterozoic and Cambrian Lesser Himalayan Sequence, the high-grade Greater Himalayan Crystalline com-plex, and the Neoproterozoic to Mesozoic Tethyan Himalayan Sequence (Figs. 3 and 4; Table 2). The Lesser Himalayan Sequence, Greater Hima-layan Crystalline complex, and Tethyan Himalayan Sequence are structur-
ally divided as MCT footwall rocks, rocks encased by the MCT below and the STD above, and rocks structurally above the STD, respectively (e.g., Hodges, 2000; Yin, 2006). We describe the lithologic units briefl y herein; for an expanded description, see Appendix 1.
The Sub-Himalayan Sequence consists of lower shallow-marine strata and upper continental deposits separated by an Oligocene unconformity (Table 2). Sub-Himalayan Sequence rocks depositionally overlie rocks of the Lesser Himalayan Sequence and correlative rocks at the base of the Himalayan foreland basin (e.g., Powers et al., 1998).
Four subunits are distinguished within the Lesser Himalayan Sequence: (1) the Neoproterozoic–Cambrian Outer Lesser Himalayan Sequence in the hanging walls of the Krol and Tons thrusts, (2) the Paleoproterozoic–Neoproterozoic Damtha and Deoban Groups in the hanging wall of the Bilaspur thrust and the footwalls of the Tons and Berinag thrusts, (3) the Paleoproterozoic Berinag Group in the hanging wall of the Berinag thrust, and (4) the Paleoproterozoic Munsiari Group, dominantly in the hanging wall of the Munsiari thrust (Table 2) (Figs. 3 and 4).
The Greater Himalayan Crystalline complex is ~7–9 km thick and con-sists of paragneiss, schist, and orthogneiss intruded by minor Tertiary leu-cogranites concentrated mostly in its upper 2–3 km (Table 2). An inverted metamorphic fi eld gradient is observed across a complete section of these rocks along the Sutlej River, progressing from garnet-staurolite–bearing rocks at the base to migmatitic rocks near the top (Vannay and Grase-mann, 1998).
The Tethyan Himalayan Sequence is dominated by the Neoproterozoic–early Cambrian Haimanta Group, early Paleozoic granites, Cambrian Parahio Formation, and overlying Paleozoic–Mesozoic strata (Table 2). Its basement is likely the Paleoproterozoic Baragaon gneiss in the MCT shear zone directly below the unit (Bhanot et al., 1978; Miller et al., 2000; this study). The Haimanta Group is garnet grade across its basal 1–3 km of section, and the grade decreases upsection across the Tethyan Hima-layan Sequence.
REGIONAL TECTONIC FRAMEWORK
First-order structures in the Himachal Himalaya are represented by a stack of northern rooted thrusts, many of which are folded (Fig. 3). The main fault zones and fault systems include, from southwest to northeast, (1) the Main Frontal thrust, (2) the Sub-Himalayan thrust zone, (3) the Bilaspur-Palampur thrust system, (4) the Krol-Mandi thrust system, (5) the MCT, (6) the Tons thrust, (7) the Berinag thrust, (8) the Munsiari thrust, (9) the STD, (10) the Tethyan Himalayan fold-and-thrust belt including the Mata nappe, and (11) the Great Counter thrust system (Figs. 3 and
Wedge extrusionChannel flow / focused denudation
Tectonic wedging
N
TibetITS
ITS
ITS
Tibet
Tibet
N
N
LHS GHC
THS
MainCentral thrust
South Tibetdetachment
Great Counter thrust
South Tibetdetachment
MainCentral thrust
LHS GHCTHS
LHS
GHC
THS
South Tibetdetachment
MainCentral thrust
Early “tunneling” stage:Eocene-Oligocene
Focused denudation stage:E. Miocene - M. Miocene
(to present?)
E. Miocene - M. Miocene
E. Miocene - M. MioceneFigure 2. Himalayan tectonic models for the emplacement of the Greater Himalayan Crystalline complex (GHC): channel fl ow/focused denu-dation model (e.g., Nelson et al., 1996; Beaumont et al., 2001; Hodges et al., 2001); wedge extrusion model (e.g., Burchfi el and Royden, 1985; Grujic et al., 1996); tectonic wedging model (e.g., Yin, 2006; Webb et al., 2007). THS—Tethyan Himalayan Sequence; LHS—Lesser Himalayan Sequence; ITS—Indus-Tsangpo suture; E.—Early; M—Middle.
Webb et al.
1016 Geosphere, August 2011
TAB
LE 1
. PR
ED
ICT
ION
S O
F H
IMA
LAYA
N T
EC
TON
IC M
OD
ELS
Mod
els
Hig
h-gr
ade
rock
af
fi nity
Faul
t kin
emat
ics
Exh
umat
ion
hist
ory
Spa
tial d
istr
ibut
ion
of m
etam
orph
ism
Alo
ng-s
trik
e st
ruct
ural
and
/or
stra
tigra
phic
va
riatio
n W
edge
ext
rusi
on
(e.g
., B
urch
fi el
and
Roy
den,
19
85)
Gre
ater
Him
alay
an
Cry
stal
line
com
plex
ro
cks
are
deriv
ed
from
the
Indi
a pl
ate
ST
D to
p-to
-the
nor
th1.
Gre
ater
Him
alay
an C
ryst
allin
e co
mpl
ex
exhu
med
in th
e E
arly
Mio
cene
, syn
-ST
D
mot
ion
2. P
aleo
gene
exh
umat
ion
of T
ethy
an
Him
alay
an S
eque
nce
1. E
xpos
ed m
etam
orph
ic is
ogra
ds
subp
aral
lel t
o ap
prox
imat
ely
plan
ar M
CT,
S
TD
, the
refo
re n
orth
-dip
ping
2.
Inve
rted
met
amor
phis
m d
omin
ates
low
er
5–10
km
of M
CT
han
ging
wal
l
Ear
ly–M
iddl
e M
ioce
ne e
xtru
sion
of t
he G
reat
er
Him
alay
an C
ryst
allin
e co
mpl
ex b
etw
een
the
MC
T a
nd S
TD
at t
he s
urfa
ce r
equi
res
cont
inuo
us e
xpos
ure
of th
is u
nit b
etw
een
the
Less
er a
nd T
ethy
an H
imal
ayan
Seq
uenc
es
alon
g th
e le
ngth
of t
he o
roge
n.
Cha
nnel
fl ow
(e
.g.,
Nel
son
et
al.,
1996
)
Gre
ater
Him
alay
an
Cry
stal
line
com
plex
ro
cks
are
deriv
ed
from
the
Asi
a pl
ate
ST
D to
p-to
-the
nor
th1.
Gre
ater
Him
alay
an C
ryst
allin
e co
mpl
ex
exhu
med
in th
e E
arly
Mio
cene
, syn
-ST
D
mot
ion
2. B
asal
Tet
hyan
Him
alay
an S
eque
nce
exhu
med
prio
r to
the
Gre
ater
Him
alay
an
Cry
stal
line
Com
plex
1. E
xpos
ed m
etam
orph
ic is
ogra
ds
subp
aral
lel t
o ap
prox
imat
ely
plan
ar M
CT,
S
TD
, the
refo
re n
orth
-dip
ping
2.
Inve
rted
met
amor
phis
m d
omin
ates
low
er
5–10
km
of M
CT
han
ging
wal
l
Ear
ly–M
iddl
e M
ioce
ne e
xtru
sion
of t
he G
reat
er
Him
alay
an C
ryst
allin
e co
mpl
ex b
etw
een
the
MC
T a
nd S
TD
at t
he s
urfa
ce r
equi
res
cont
inuo
us e
xpos
ure
of th
is u
nit b
etw
een
the
Less
er a
nd T
ethy
an H
imal
ayan
Seq
uenc
es
alon
g th
e le
ngth
of t
he o
roge
n.M
odifi
ed c
hann
el
fl ow
(e.
g.,
Bea
umon
t et
al.,
2004
)
Gre
ater
Him
alay
an
Cry
stal
line
com
plex
ro
cks
are
deriv
ed
from
the
Indi
a pl
ate
ST
D to
p-to
-the
nor
th;
asym
met
ric th
rust
ex
trus
ion
mod
el
allo
ws
alte
rnat
ing
top-
to-t
he s
outh
and
to
p-to
-the
nor
th S
TD
sh
earin
g (B
eaum
ont
et a
l., 2
004)
1. G
reat
er H
imal
ayan
Cry
stal
line
com
plex
ex
hum
ed in
the
Ear
ly M
ioce
ne, s
yn-S
TD
m
otio
n 2.
Bas
al T
ethy
an H
imal
ayan
Seq
uenc
e ex
hum
ed p
rior
to o
r ap
prox
imat
ely
sync
hron
ousl
y (w
ith a
sym
met
ric th
rust
ex
trus
ion)
with
the
Gre
ater
Him
alay
an
Cry
stal
line
com
plex
1. E
xpos
ed m
etam
orph
ic is
ogra
ds
subp
aral
lel t
o ap
prox
imat
ely
plan
ar M
CT,
S
TD
, the
refo
re n
orth
-dip
ping
2.
Inve
rted
met
amor
phis
m d
omin
ates
low
er
5–10
km
of M
CT
han
ging
wal
l
Ear
ly–M
iddl
e M
ioce
ne e
xtru
sion
of t
he G
reat
er
Him
alay
an C
ryst
allin
e co
mpl
ex b
etw
een
the
MC
T a
nd S
TD
at t
he s
urfa
ce r
equi
res
cont
inuo
us e
xpos
ure
of th
is u
nit b
etw
een
the
Less
er a
nd T
ethy
an H
imal
ayan
Seq
uenc
es
alon
g th
e le
ngth
of t
he o
roge
n.
Tect
onic
wed
ging
(e
.g.,
Yin
, 200
6;
Web
b et
al.,
20
07)
Gre
ater
Him
alay
an
Cry
stal
line
com
plex
ro
cks
are
deriv
ed
from
the
Indi
a pl
ate
Alte
rnat
ing
top-
to-t
he
sout
h an
d to
p-to
-the
no
rth
ST
D s
hear
ing
1. G
reat
er H
imal
ayan
Cry
stal
line
com
plex
ex
hum
ed a
fter
the
Ear
ly M
ioce
ne, p
ost-
ST
D m
otio
n 2.
Bas
al, h
inte
rland
Tet
hyan
Him
alay
an
Seq
uenc
e ex
hum
ed a
ppro
xim
atel
y sy
nchr
onou
sly
with
the
uppe
r G
reat
er
Him
alay
an C
ryst
allin
e co
mpl
ex
1. E
xpos
ed m
etam
orph
ic is
ogra
ds
subp
aral
lel t
o th
e fo
lded
(op
en to
tigh
tly)
MC
T, S
TD
, the
refo
re fo
lded
2.
Inve
rted
met
amor
phis
m s
outh
of M
CT-
ST
D in
ters
ectio
n lin
e do
min
ates
onl
y ~
1–2
km M
CT
zon
e; s
truc
tura
lly h
ighe
r ro
cks
show
rig
ht-w
ay-u
p m
etam
orph
ism
For
elan
d M
CT
str
ands
juxt
apos
e Te
thya
n H
imal
ayan
Seq
uenc
e ro
cks
on to
p of
Les
ser
Him
alay
an S
eque
nce
rock
s; h
inte
rland
M
CT
str
ands
juxt
apos
e G
reat
er H
imal
ayan
C
ryst
allin
e co
mpl
ex r
ocks
ato
p Le
sser
H
imal
ayan
Seq
uenc
e ro
cks.
Loc
ally
, the
le
adin
g ed
ge o
f the
Gre
ater
Him
alay
an
Cry
stal
line
com
plex
rem
ains
bur
ied.
Not
e: S
TD
—S
outh
Tib
et d
etac
hmen
t; M
CT
—M
ain
Cen
tral
thru
st.
Figure 3. This fi gure is intended to be viewed at a size of 11 × 17× 17. To view the full-sized PDF fi le of Figure 3, please visit http://dx.doi.org/10.1130/GES00627.S1. Geological map of the Himachal Himalaya. Lines of cross sections drawn include A-A′ (cross section in Fig. 4A, reconstruction in Fig. 17), A-A′, A′′-A′′′ (sketch cross section in Fig. 4B), and B-B′ (sketch cross section in Supplemental File 11). Red boxes outline the positions of maps in Fig. 6A, 6B, 6C. Figure 3 is based upon our mapping, analysis of LANDSAT images, dis-cussions with A.K. Jain and S. Singh (2004, personal commun.), and previous work by Agarwal and Kumar (1973), Ahmad et al. (1999), Auden (1934), Bassi (1989), Bhargava (1976, 1980), Bhargava et al. (1991), Bhat-tacharya et al. (1982), Célérier et al. (2009a), Choudhuri et al. (1992), Das and Rastogi (1988), Dèzes (1999), Dèzes et al. (1999), Epard et al. (1995), Frank et al. (1973, 1995), Fuchs (1982), Grasemann et al. (1999), Gururajan (1990), Gururajan and Virdi (1984), Jäger et al. (1971), Jain (1972), Jain and Anand (1988), Jain et al. (1999), Kumar and Brookfi eld (1987), Pachauri (1980), Pandey et al. (2003), Pecher and Scaillet (1989), Pilgrim and West (1928), Powers et al. (1998), Raina (1981), Raiverman (2000), Rao and Pati (1980), Rat-tan (1973), Rautela and Thakur (1992), Robyr et al. (2002), Rupke (1974), Schlup (2003), Sch-lup et al. (2003), Shanker and Dua (1978), K.K. Sharma (1977), V.P. Sharma (1977), Singh and Jain (1993), Singh and Thakur (2001), Sri-kantia and Bhargava (1984, 1988), Srikantia and Sharma (1976), Steck (2003), Steck et al. (1998), Tewari et al. (1978), Thakur and Rawat (1992), Thiede et al. (2006), Thöni (1977), Valdiya (1978, 1980), Vannay and Grasemann (1998), Vannay and Steck (1995), Vannay et al. (1999, 2004), Virdi (1979), Wiesmayr and Grasemann (2002), West (1939), Wyss (2000), and Wyss et al. (1999).
1Supplemental File 1. PDF fi le of sketch cross section along profi le B-B′; see text Figure 3. The discontinuous graphitic quartzite marker lithology occurs at two levels in the Chandrabhaga River Val-ley. These occurrences are interpreted as two distinct stratigraphic horizons. Alternatively, these may re-fl ect unrecognized kilometer-scale tight to isoclinal folds. Primary sources for this section are Powers et al. (1998) (sub-Himalayan thrust zone); Srikantia and Sharma (1976) (sedimentary Lesser Himala-yan Sequence units); Frank et al. (1995) [Haimanta Group in the Main Central thrust (MCT) hanging wall]; Thakur (1998), Dèzes (1999), Yin (2006), and Webb et al. (2007) (STD, South Tibet detachment). If you are viewing the PDF of this paper or read-ing it offl ine, please visit http://dx.doi.org/10.1130/GES00627.S2 or the full-text article on www. gsapubs.org to view Supplemental File 1.
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1017
Tons R
iver
Pabbar Ri
ver
Sutlej Rive
r
Chandrabhaga River
Spiti
Sutlej
Tso Morari
Beas
River
Yamu
na
Beas Ri
ver
Alaknan
da River
Gang
es R
iver
River
River
Bhila
ngan
a Rive
r
River
Bhagira
thi
Ri
ver
Beas
Riv
er
Parbati River
Yamuna
Ri
ver
KN
TI
Z-CGHC Z-CGHC
Z-CGHC
Z-CGHC
Z-CGHC
Z-CGHC
KG
P-J
P-J
P-J
P-J
O-C
Z-CH
Z-CHZ-CH
Z-CH
Z-CH
Z-CH
Z-CH
Z-CH
Z-CH
Z-CH
Z-CH
Z-CH
XWXJ
XW
XW
XW
C-O
C-O
C-O
C-O
C-O
C-O
C-O
C-O
C-O
ZC
ZC XBA
XBA
XBA
XBE
XBE
XBE
XBE
XBE
X/X
X/X
XD XD
XD
XD
Y-Z
Y-Z
Y-Z
Y-Z
Y-ZD
Y-Z
ZB
ZB
ZB
ZS
ZS
ZS
Z-CK
Z-CK
Z-CH
CT
E/M
K/E
K/E
MLD
MUDMLS
XBA
MMS
M-Q
X/Z
CP
TL
XW
M-Q
M-Q
M-Q
M-Q
M-Q
M-Q
M-Q
MMS
MMS
MMS
MMS
MMS
MLS
MLS
MLS
MLS
MLS
MLS
MLS
K/E
K/E
K/E
K/E
MUD
MUD
MUD
MUD
MUD
CT
CT
P-J
O-C
O-C
P-J
P-J
O-C
O-C
CP
MUD
KG
KG
Q
Q
XD?
Y-Z
Z-CH
KN
Kullu
Manali
KhoksarSissu
Keylong
Larji
Patli Kuhl
Manikaran
WangtuRecong Peo
Morang
RampurSangla
Tiuni
Sankri
Harkidun
Tandi
Naura
Chaupal
Narkanda
Mikkim
Muth
Baldar
Tos
Batal
Darcha
Dharmsala
Rohru
Puh
Rohtang La
Mandi
Kangra
Chamba
Kalka
Chandigar Uttarkashi
Bilaspur
Sundarnagar
Gangotri
Rishikesh
Mussoorie
New Tehri
Nahan
Paonta Sahib
Sarchu
SHIMLA
rr
77oE 78oE
79oE
33o N
32o N
31o N
78oE 79oE
33oN
32oN
31oN
30oN
A
A’
Bilaspur thrust
Bilaspur thrust
Main Frontal thrust
Main Frontal thrust
Palampur
Great Counter Great Counter thrust systemthrust system
DEHRA DUN
Chaura thrustChaura thrust
Mata Nappe
Mata Nappe
Main Frontal thrust
Main Frontal thrust
South Tibet detachment
South Tibet detachment
Krol thrust
Krol thrust Tons thrustTons thrust
Berinag thrust
Berinag thrust
Munsiari thrust
Munsiari thrust
Sarchu Normal Fault
Spiti Synclinorium
Spiti Synclinorium
Chamba Synclinorium
Chamba Synclinorium
Tandi Syncline
Tandi Syncline
LeoLeoPargilPargilDomeDome
Phojal Anticline
Phojal Anticline
Main Central thrust
Main Central thrust
Dehra Dun Reentrant
Dehra Dun Reentrant
Mandi
Mandi
Indo-GangeticIndo-GangeticPlainPlain
Nahan beltNahan belt
Kullu
Window
Reentrant
thrust
thrust
thrust
thrust
A’’
A’’’
M
llalall M
a
ma
aaPalal
ma
PalaalalalalPalaal
mam
B
B’Tso Morari UHP dome
Tso Morari UHP dome
Ribil fault
Ribil fault
Spiti Synclinorium
Spiti Synclinorium
Dutung-Thaktote thrust
Dutung-Thaktote thrustParang La thrust
Parang La thrust
NarkandaHalf-Window
Uttarkashi
Half-Window
Zanskar shear zone
Zanskar shear zone
Lansdowne klippeLansdowne klippe
Almora klippeAlmora klippe
50 km0 10 20 30 40
N
Sub-Himalayan Sequence
M-Q Upper Siwalik
Q Active depocenters
MLS Lower Siwalik
MMS Middle Siwalik
MUD Upper Dharamsala
MLD Lower Dharamsala
K/E Singtali / Subathu
E/M Undifferentiated Subathu / Lower Dharamsala
Lesser Himalayan Sequence
Out
er L
esse
r H
imal
aya
Berinag
Mun
siar
iG
roup
XBE
XW
XJ
CT Tal
Z-CK Krol
ZS Simla
ZB Basantpur
Y-Z Deoban
XD Damtha
Wangtu
Jeori
Darla volcanics
Undifferentiated Berinag / DamthaX/X
X/Z
Map Units (described in Table 2)
Tethyan Himalayan Sequence
Sed
imen
tary
Roc
ksIg
neou
s R
ocks
KG
P-J
O-C
CP
XBA
Giumal-Chikkim
Tandi
Thaple-Muth-Lipak
Parahio
Haimanta (with graphitic quartzite marker beds)
Early Paleozoic granite
~830 Ma granite / gneiss
Baragaon granitic gneiss
Z-CH
C-O
Indus Suture Zone
KN Nidar Ophiolite
TI Indus Molasse
Z-CGHC
Tertiary LeucograniteTL
Greater Himalayan Crystalline complex
river
lake
TownSouth Tibet detachment
Overturned South Tibet detachment
Main Central thrust
Munsiari thrust
Berinag thrust
Tons thrust
Krol thrust
Phojal anticline
Geological SymbolsContacts and Folds
Key Structures
Solid: well located; dashed: approximately located; dotted: concealed and inferred
Lithologic Thrust fault
Anticline overturned overturnedSyncline
Normal fault
ZC
overturned synformal anticline
Fig. 6A.
Fig. 6B.
Fig. 6C.
Webb et al.
1018 Geosphere, August 2011
ZS
ZB
Y-Z XD
XB
E
Y-Z
XD
M-Q
MM
SM
LS
MU
D
K/E
MLD
Z-C
HZ
-CH
ZC
Z-C
H
C-O
Z-C
GH
CX
BA
A
km 5 0 -5 -10
-15
-20
A′ km 5 0 -
5
-10
-15
-20
XW
XJ
P-J
P-J
O-C
CP
KG
K/E
XW/X
J
30 k
m0
1020
no v
ertic
al e
xagg
erat
ion
XB
E
Y-Z
C-O
XW/X
J
Z-C
KK
/E
Bila
spur
thru
st
Kro
l thr
ust
Tons
thru
stB
erin
ag th
rustM
unsi
ari t
hrus
tM
ain
Fron
tal t
hrus
t
Sub
-Him
alay
an th
rust
zon
e
Cha
ura
thru
stM
ain
Cen
tral
thru
stS
outh
Tib
et d
etac
hmen
t
AS
elec
ted
dat
a, c
olo
r-co
ded
: met
amor
phic
con
ditio
ns (
pres
sure
in k
bar,
tem
pera
ture
in °
C),
met
amor
phic
cry
stal
lizat
ion
age
(Ma)
, 40 A
r/39
Ar
mus
covi
te a
ge
(Ma)
, zirc
on fi
ssio
n tr
ack
age
(Ma)
, apa
tite
fissi
on tr
ack
age
(Ma)
. Ref
eren
ces
liste
d in
figu
re c
aptio
n an
d de
note
d by
cap
italiz
ed s
uper
scrip
ts (
e.g.
, 70X
).
6-10
A3-
5A,B
10.5
-12B
0-2A
,C,D
,E2-
3D2-
5B13
-16B
1.7-
2.7B
25-2
15F
10-1
9F
9.7B
15.4
-17.
7B4-
7B,E
13-1
6B,E
16-1
9B,E
23-4
0G27
-34H
(E.)
Pal
eozo
ic, ~
41.5
-28.
5TS
9TS
6-9H
,L,M
580-
660H
,L,M
300N
200N
8M
base
:600
->to
p:75
0Mba
se:6
00->
top:
700B
,I,J,
L,M
7-9T
Sba
se:9
->to
p:7B
,I,J,
L,M
450-
630K
,TS
570T
S
A
km 5 0 -5 -10
-15
-20
-25
A′
A′′
A′′′ km 5 0 -5 -1
0
-15
-20
-25
-30
KG
STD
50 k
m0
1020
3040
no v
ertic
al e
xagg
erat
ion
O-C
Z-C
H
P-J X
W
Z-C
GH
C
KN
TI
KN
KN
Z-C
GH
C (
UH
P)
XB
E
MC
T
MC
TG
CT
Mat
a N
appe
Lada
kh b
atho
lith
(Asi
a pl
ate)
B
Fig
ure
4. (
A)
Cro
ss s
ecti
on o
f th
e H
imac
hal H
imal
aya.
Sec
tion
dra
wn
alon
g lin
e A
-A′ o
f F
igur
e 3.
Uni
ts a
nd s
ymbo
ls a
re a
s in
Fig
ure
3. B
row
n cu
rve
repr
esen
ts E
arth
’s s
ur-
face
, sho
rt b
lack
line
s al
ong
Ear
th’s
sur
face
rep
rese
nt b
eddi
ng a
nd/o
r fo
liati
on a
ttit
udes
. All
faul
ts a
re to
p-to
-the
-sou
thw
est w
ith
the
exce
ptio
n of
the
Sout
h T
ibet
det
achm
ent,
w
hich
dis
play
s re
cord
s of
bot
h to
p-to
-the
-sou
thw
est
and
top-
to-t
he-n
orth
east
mot
ion.
Ref
eren
ces
for
anal
ytic
al d
ata
are:
AT
hied
e et
al.,
200
9; B
Van
nay
et a
l., 2
004;
CJa
in e
t al
., 20
00;
DT
hied
e et
al.,
200
4; E
Thi
ede
et a
l., 2
005;
FSc
hlup
, 200
3; G
E. C
atlo
s, 2
004,
per
sona
l com
mun
.; H
Cha
mbe
rs e
t al
., 20
09;
I Cha
mbe
rs e
t al
., 20
08;
J Cad
dick
et
al.,
2007
; KG
rego
ry, 2
004;
LV
anna
y an
d G
rase
man
n, 1
998;
MV
anna
y et
al.,
199
9; N
Wie
smay
r an
d G
rase
man
n, 2
002;
TS t
his
stud
y. (
B)
Sket
ch c
ross
sec
tion
of
the
Him
acha
l and
Lad
akh
Him
alay
a. M
CT
—M
ain
Cen
tral
thr
ust;
ST
D—
Sout
h T
ibet
det
achm
ent;
GC
T—
Gre
at C
ount
er t
hrus
t sy
stem
; U
HP
—ul
trah
igh
pres
sure
. The
abb
revi
atio
ns a
re t
he s
ame
as
in t
he le
gend
in F
igur
e 3.
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1019
TAB
LE 2
. TE
CTO
NO
ST
RAT
IGR
AP
HY
OF
TH
E H
IMA
CH
AL
HIM
ALA
YA
Uni
t nam
e (a
ltern
ativ
e na
me)
Lith
olog
ic d
escr
iptio
nT
hick
ness
(m)
Age
con
stra
ints
Nd,
Sr
isot
opic
co
nstr
aint
s*H
imal
ayan
For
elan
d U
pper
Siw
alik
Fm
†ss
, con
glD
D§
~17
00 -
230
0DD
depo
sitio
n 7
Ma
to P
leis
toce
ne: M
SZ
#N
.D.
Mid
dle
Siw
alik
Fm
ss w
ith m
inor
slts
, sh,
con
glD
D~
1300
- 2
000D
Dde
posi
tion
11 to
7 M
a: M
SZ
#N
.D.
Low
er S
iwal
ik F
msl
ts w
ith m
inor
ss,
shD
D~
700
- 13
00D
D
depo
sitio
n 13
to 1
1 M
a: M
SZ
, AA
#N
.D.
Upp
er D
hara
msa
la F
m (
Kas
auli)
grey
ss,
min
or s
h (fl
uvi
al /
allu
vial
)CC
, TT
~10
00 -
130
0DD
depo
sitio
n 16
.5 to
13
Ma:
MS
AA, c
f. de
trita
l mic
aBB
#N
.D.
Low
er D
hara
msa
la F
m (
Dag
shai
)ss
, slts
, sh,
cal
iche
(fl u
vial
/ al
luvi
al)C
C, T
Tup
to 1
300D
D**
depo
sitio
n 20
to 1
6.5
Ma:
MS
AA, c
f. de
trita
l mic
aBB
, UU
#N
.D.
Sub
athu
Fm
ls, s
h, m
inor
fi ne
gra
ined
ss
(sha
llow
mar
ine)
CC
, TT
up to
200
DD**
, FF,
GG
late
st P
aleo
cene
-M
iddl
e E
ocen
e: fo
ssils
CC
N.D
.S
ingt
ali F
mls
, min
or q
uart
z ar
enite
(sh
allo
w m
arin
e)C
C~
50, d
isco
ntin
uous
CC
Late
Cre
tace
ous
- P
aleo
cene
: fos
sils
CC
††N
.D.
Less
er H
imal
ayan
Seq
uenc
e: O
uter
Les
ser
Him
alay
aTa
l Fm
ss, s
ltsE
EE
, S~
500S
Low
er C
ambr
ian:
trilo
bite
sA, E
EE, R
e-O
s is
ochr
onB
≤ L
PtC
*K
rol G
pdl
, ls
with
min
or s
h, s
ltsR
, FF
F
~15
00 -
220
0HH
, S, F
FF
~59
0-54
3 M
a: fo
ssils
GG
G, R
, EE
E,
13C
shi
ftHH
H≤
LPtM
Shi
mla
Gp
(Cha
ndpu
r +
Nag
that
+
Bla
ini)
sh (
min
or s
late
), s
lts, s
s, w
ith m
inor
gw
, till
ite, c
ongl
CC
C,
FF,
BB
B, D
DD
~38
00 -
410
0II ,
cf.
~33
00F
F<
~62
0 M
a: d
etrit
al U
-Pb
zrcT
S; s
trat
igra
phic
ally
bel
ow K
rol G
pS≤
L P
tE, M
, Y
Bas
antp
ur F
m (
Man
dhal
i)in
terb
edde
d ls
, slts
, sh
(min
or s
late
)FF,
BB
B>
~30
0-64
0S, J
J , cf
.>~
1360
FF
839±
138
Ma:
Re-
Os
isoc
hron
B, N
eo-P
t: st
rom
O, Y
Y≤
L P
tE, M
Less
er H
imal
ayan
Seq
uenc
e: P
arau
toch
thon
Deo
ban
Gp
(Sha
li)dl
, ls
with
min
or s
h, c
hert
, ssS
>~
3000
HH
, II
≥ 2
leve
ls, l
ower
: (la
test
Pal
eo?-
)Mes
o-P
t, up
per:
Neo
-Pt.
stro
m a
nd o
ther
foss
ilsS
, N, O
, P, Q
, WW
, XX
, YY,
ZZ
≥ M
PtM
, Y*
Dam
tha
Gp
(Sun
darn
agar
; Cha
krat
a [lo
wer
mem
ber]
, Rau
tgar
a [u
pper
])
gw, s
lts, s
late
suc
ceed
ed b
y qt
zt, s
l, ba
sic
sills
and
di
kesS
>~
2900
HH
≥ P
aleo
-Pt,
stra
tigra
phic
ally
bel
ow D
eoba
n G
pSN
.D.
Less
er H
imal
ayan
Seq
uenc
e: B
erin
ag th
rust
han
ging
wal
l roc
ks
Ber
inag
Gp
(Ram
pur,
Man
ikar
an)
gree
nsch
ist-
faci
es s
eric
itic
quar
tz-a
reni
te, m
etab
asal
t (s
ills,
dik
es, fl
ow
s), m
inor
slS
, J>
~10
00K
K~
1.85
- 1
.8 G
a: d
etrit
al U
-Pb
zrcM
, TS, U
-Pb
zrc
from
m
etab
asal
tJqt
zt: ≥
M P
tM, Y
, m
eta-
basa
lt: ≤
L
PtJ,
JJJ
, VV
Less
er H
imal
ayan
Seq
uenc
e: M
unsi
ari G
roup
Wan
gtu
gnei
ss (
Ban
dal)
dom
inan
tly g
rani
tic a
ugen
gne
issL
L>
~20
00LL
~1.
85 G
a: R
b-S
r w
hole
roc
kK, J
, U-P
b zr
cJ, L
, M≥
M P
tJ, M
Jeor
i met
ased
imen
tary
roc
kspa
ragn
eiss
, mic
a sc
hist
, min
or m
etab
asite
, qtz
t, gr
aniti
c gn
eiss
LL
unkn
own
som
e la
yers
<~
1.9
Ga,
oth
er l
ayer
s >
~20
68 M
a: d
etrit
al U
- P
b zr
cM, T
S, i
gneo
us U
-Pb
zrcI
II
≥ M
PtJ,
M
Fel
sic
pegm
atite
(cr
oss-
cuts
Wan
gtu
gnei
ss fo
liatio
n)up
to ~
4 m
thic
k di
kes
~8-
6 M
a: U
-Pb
zrc,
Th-
Pb
mon
azite
TS
N.D
.G
reat
er H
imal
ayan
Cry
stal
line
com
plex
para
gnei
ss, s
chis
t, or
thog
neis
s~
4500
-800
0LL
som
e la
yers
you
nger
than
~85
0 M
a: d
etrit
al z
rcM
, TS, 4
95 M
a or
thog
neis
s: R
b/S
rK≤
L P
tM, Y
Leuc
ogra
nite
up to
~10
0’s
m th
ick
~27
-20
Ma:
U-P
b m
onaz
ite, u
rani
nite
H, T
h-P
b m
onaz
iteT
SN
.D.
Teth
yan
Him
alay
an S
eque
nce:
sed
imen
tary
roc
ksG
ium
al-C
hikk
im s
ucce
ssio
nss
, bla
ck s
h, ls
EE
~35
0RR
Cre
tace
ous:
foss
ilsR
RN
.D.
Tand
i Gp
carb
onat
e, s
h, s
lts, q
tztM
M>
~19
20M
MP
erm
ian
- Ju
rass
ic: f
ossi
lsT,
U, V
N.D
.T
hapl
e-M
uth-
Lipa
k su
cces
sion
sh, s
lts, q
tzt,
quar
tz-a
reni
te, c
arbo
nate
, con
glM
M~
1650
MM, c
f. ~
1100
NN
Ord
ovic
ian
- C
arbo
nife
rous
: fos
sils
VN
.D.
Par
ahio
Fm
ss
, sh
(sili
cicl
astic
del
taic
)AA
A
~70
0NN, c
f. >
1350
AA
Aup
perm
ost L
ower
Cam
bria
n-m
iddl
e M
iddl
e C
ambr
ian:
foss
ilsA
,
W, A
AA
N.D
.H
aim
anta
Gp
phyl
lite,
sch
ist,
garn
et s
chis
t, gr
aphi
tic s
chis
t, ps
amm
itic
schi
st, m
inor
car
bona
te, m
inor
met
abas
alt
>~
6250
MM, c
f. ~
2000
-35
00N
N<
~55
0 M
a -
Ear
ly C
ambr
ian:
trilo
bite
sX, c
ross
-cut
ting
igne
ous
ages
E, K
, det
rital
U-P
b zr
cTS
≤ L
PtE
, M, Y
(con
tinue
d)
Webb et al.
1020 Geosphere, August 2011
TAB
LE 2
. TE
CTO
NO
ST
RAT
IGR
AP
HY
OF
TH
E H
IMA
CH
AL
HIM
ALA
YA (
cont
inue
d)
Uni
t nam
e (a
ltern
ativ
e na
me)
Lith
olog
ic d
escr
iptio
nT
hick
ness
(m)
Age
con
stra
ints
Nd,
Sr
isot
opic
co
nstr
aint
s*Te
thya
n H
imal
ayan
Seq
uenc
e: ig
neou
s ro
cks
Ear
ly P
aleo
zoic
gra
nito
ids
gran
ite, m
inor
mafi
c e
ncla
ves,
min
or a
plite
, loc
ally
gn
eiss
icup
to a
t lea
st ~
2000
OO
Cam
bro-
Ord
ovic
ian:
Rb-
Sr
who
le r
ockD
, U-P
b zr
cE, F
, TS
≤ L
PtE
~83
0 M
a (C
haur
-Bla
ck M
tn)
gran
itegr
anite
, gra
nitic
gne
iss
up to
~30
00Q
Q~
830
Ma:
U-P
b zr
cG, T
SN
.D.
Bar
agao
n gr
aniti
c gn
eiss
myl
oniti
c gr
aniti
od g
neis
sup
to ~
1100
PP
~1.
85 G
a: R
b-S
r w
hole
roc
kI, J
, U-P
b zr
cTS
≥ M
PtJ,
M
Indu
s S
utur
e Z
one
Nid
ar O
phio
lite
ultr
amafi
cs,
gab
bros
, pill
ow b
asal
tsS
S~
2100
-270
0SS
140.
5±5.
3 M
a: S
m-N
d (p
lagi
ocla
se-c
linop
yrox
ene)
SS
N.D
.In
dus
Mol
asse
sh, s
lts, s
s, c
ongl
EE
unkn
own
early
Eoc
eneE
EN
.D.
*Him
alay
an p
re-C
enoz
oic
rock
s pl
ot in
two
larg
ely
dist
inct
gro
ups
in N
d an
d S
r is
otop
ic s
pace
(se
e S
uppl
emen
tal F
ile 2
2 ). T
hese
gro
ups
can
be d
istin
guis
hed
by a
ge: M
iddl
e P
rote
rozo
ic a
nd o
lder
roc
ks y
ield
ε N
d(50
0) <
~-1
4 an
d a
broa
d ra
nge
of 8
7 Sr/
86S
r(50
0) v
alue
s (t
his
grou
p is
abb
revi
ated
as
“ ≥ M
Pt”
in th
e ta
ble)
, whe
reas
Lat
e P
rote
rozo
ic a
nd y
oung
er r
ocks
yie
ld ε
Nd(
500)
> ~
-14
and
a na
rrow
ran
ge o
f 87 S
r/86
Sr(
500)
va
lues
(th
is g
roup
is a
bbre
viat
ed a
s “≤
L P
t” in
the
tabl
e).
† Add
ition
al a
bbre
viat
ions
in th
is ta
ble
are:
Fm
= F
orm
atio
n, G
p =
Gro
up, c
ongl
= c
ongl
omer
ate,
ss
= s
ands
tone
, slts
= s
iltst
one,
sh
= s
hale
, gw
= g
reyw
acke
, ls
= li
mes
tone
, dl =
dol
omite
, qtz
t = q
uart
zite
, N.D
. =
not d
eter
min
ed, M
S =
mag
neto
stra
tigra
phy,
zrc
= z
ircon
, str
om =
str
omat
olite
s, P
t = P
rote
rozo
ic.
§ Cap
italiz
ed, s
uper
scrip
t let
ters
ref
er to
sou
rces
: AH
ughe
s an
d Je
ll, 1
999;
BS
ingh
et a
l., 1
999;
CM
yrow
et a
l., 2
003;
DJä
ger
et a
l., 1
971;
EM
iller
et a
l., 2
001;
FM
arqu
er e
t al.,
200
0; G
Sin
gh e
t al.,
200
2; H
Wal
ker
et
al.,
1999
; ITr
ived
i et a
l., 1
984;
J Mill
er e
t al.,
200
0; K
Fran
k et
al.,
197
7; L
Sin
gh e
t al.,
199
4; M
Ric
hard
s et
al.,
200
5; N
Val
diya
, 196
9; O
Rah
a an
d S
astr
y, 1
982;
PS
rivas
tava
and
Kum
ar, 2
003;
QTe
war
i, 20
03; R
Sin
gh a
nd
Rai
, 198
3; S
Val
diya
, 198
0; T
Pow
ell a
nd C
onag
han,
197
3; U
Srik
antia
and
Bha
rgav
a, 1
979;
VS
rikan
tia a
nd B
harg
ava,
199
8; W
Gar
zant
i et a
l., 1
986;
XH
ughe
s an
d D
rose
r, 19
92; Y
Ahm
ad e
t al.,
200
0; Z
Mei
gs e
t al.,
199
5;
AAW
hite
et a
l., 2
001;
BBN
ajm
an e
t al.,
199
7; C
CN
ajm
an e
t al.,
199
3; D
DP
ower
s et
al.,
199
8; E
ES
teck
, 200
3; F
FS
rikan
tia a
nd S
harm
a, 1
976;
GGR
aive
rman
, 200
0; H
HR
upke
, 197
4; II
Sriv
asta
va a
nd M
itra,
199
4; JJ
Bha
rgav
a,
1976
; KKV.
P. S
harm
a, 1
977;
LL V
anna
y an
d G
rase
man
n, 1
998;
MMW
iesm
ayr
and
Gra
sem
ann,
200
2; N
NV
anna
y an
d S
teck
, 199
5; O
OW
yss
et a
l., 1
999;
PPG
rase
man
n et
al.,
199
9; Q
QS
rikan
tia a
nd B
harg
ava,
198
8;
RRS
teck
et a
l., 1
998;
SSLi
nner
et a
l., 2
001;
TTN
ajm
an a
nd G
arza
nti,
2000
; UUW
hite
et a
l., 2
002;
VVB
hat a
nd L
eFor
t, 19
93; W
WV
enka
tach
ala
and
Kum
ar, 1
998;
XXS
rivas
tava
and
Kum
ar, 1
997;
YYS
inha
, 197
5; Z
ZR
aha,
19
80; A
AAM
yrow
et a
l., 2
006;
BB
BK
umar
and
Bro
okfi e
ld, 1
987;
CC
CP
ilgrim
and
Wes
t, 19
28; D
DDV
aldi
ya, 1
970;
EE
EH
ughe
s et
al.,
200
5; F
FFJa
ing
et a
l., 2
003;
GG
GJa
ing
et a
l., 2
002;
HH
HA
haro
n et
al.,
198
7; II
I Sin
gh e
t al.,
20
06; J
JJB
hat a
nd L
eFor
t, 19
92; T
ST
his
stud
y.# T
he a
ge e
stim
ates
for
the
Mio
cene
and
you
nger
SH
roc
ks la
rgel
y de
pend
on
mag
neto
stra
tigra
phic
cor
rela
tion.
How
ever
, the
you
nges
t 40 A
r/39
Ar
age
of d
etrit
al w
hite
mic
as, w
hich
rec
ord
the
time
at w
hich
the
mic
a co
oled
bel
ow ~
370
°C, p
rovi
de a
max
imum
age
of d
epos
ition
. Det
rital
mic
a ag
es o
f ~22
Ma
at th
e ba
se o
f the
Low
er D
hara
msa
la, a
nd ~
16 M
a in
the
Upp
er D
hara
msa
la (
BB
,UU
) ar
e on
ly c
onsi
sten
t with
the
prop
osed
mag
neto
stra
tigra
phic
age
s if
extr
aord
inar
y co
olin
g ra
tes
are
invo
ked
(see
Yin
(20
06))
. The
you
nges
t whi
te m
ica
ages
obt
aine
d fr
om H
imal
yan
bedr
ock
are
>4 M
a (C
eler
ier
et a
l., 2
009b
), s
o us
ing
~4 m
.y. a
s a
min
imum
lag
time
betw
een
the
cool
ing
age
and
depo
sitio
nal a
ge s
ugge
sts
that
the
mag
neto
stra
tigra
phic
age
s fo
r th
e Lo
wer
and
Upp
er D
hara
msa
la a
re a
t lea
st ~
2 m
.y. t
oo o
ld. A
djus
ting
the
ages
of t
hese
uni
ts
may
als
o af
fect
inte
rpre
ted
ages
of t
he S
iwal
ik s
trat
a.**
Acc
ordi
ng to
the
DDP
ower
s et
al.
(199
8) m
odel
, the
Mai
n H
imal
ayan
Det
achm
ent r
eact
ivat
es th
e on
lapp
ing
depo
sitio
nal c
onta
ct o
f the
Ter
tiary
fore
land
bas
in o
ver
the
Vin
dhya
n G
roup
. In
this
sch
eme,
the
Low
er D
harm
sala
and
Sub
athu
pin
ch o
ut a
long
the
reac
tivat
ed p
ortio
n of
the
cont
act,
and
thus
hav
e 0
thic
knes
s at
the
pinc
h ou
t. T
he e
xpos
ed s
ectio
ns o
f the
se u
nits
hav
e th
ickn
esse
s te
ndin
g to
war
d th
e up
per
thic
knes
s va
lues
giv
en in
the
tabl
e.††
SV
aldi
ya (
1980
) no
tes
that
the
“low
er S
ingt
ali”
may
be
equi
vale
nt to
the
Gon
dwan
as (
i.e.,
late
Pal
eozo
ic-E
arly
Mes
ozoi
c).
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1021
4). Excepting the STD and the Great Counter thrust system, all major structures are southwest-directed thrusts. Several large structural culmina-tions are also exposed in the map area due to folding of major thrusts and the development of low-angle detachment faults. We refer to these struc-tures as (1) the Narkanda half-window, (2) the Uttarkashi half-window, (3) the Kullu window, (4) the Leo Pargil dome, and (5) the Tso Morari gneiss dome (Fig. 3). We briefl y describe this regional tectonic framework herein; for an expanded description, see Appendix 2.
MCT Footwall Structures
The Sub-Himalayan thrust zone is bounded by the Main Frontal thrust below and the Krol and Mandi thrusts above (Fig. 3). The Main Frontal thrust places Neogene–Quaternary strata over the modern Indo-Gangetic Plain deposits; the Mandi and Krol thrusts place Lesser Himalayan Sequence rocks over Paleogene–Quaternary strata of the Sub-Himalayan Sequence (Kumar et al., 2006; Srikantia and Sharma, 1976; Powers et al., 1998; Raiverman, 2000).
The Tons thrust, exposed along the Sutlej River near Shimla and across the southern margin of the Uttarkashi half-window, places the Outer Lesser Himalayan Sequence over the Deoban and Damtha Groups (Fig. 3) (e.g., Valdiya, 1980; Célérier et al., 2009a). The Mun-siari thrust can be traced along most of the central Himalayan orogen (e.g., Upreti, 1999; Yin, 2006; Searle et al., 2008; see discussions in Célérier et al., 2009a, 2009b), and is referred to as the MCT I in Nepal (Bordet et al., 1972; Arita, 1981; Harrison et al., 1998). The thrust crops out in the Kullu window and the Uttarkashi half-window, where it places the Munsiari Group (Wangtu and Jeori gneiss) over the Berinag Group (Figs. 3, 4, 6B, and 6C) (e.g., V.P. Sharma, 1977; Valdiya, 1980; Vannay et al., 2004). The Berinag thrust appears in both the hanging wall and footwall of the Munsiari thrust, where it juxtaposes Berinag Group rocks over the Wangtu gneiss and the Damtha Group, respec-tively (Fig. 3) (e.g., V.P. Sharma, 1977; Valdiya, 1980; Vannay et al., 2004; Célérier et al., 2009a).
MCT
The MCT is classically defi ned as the tectonic boundary between the Greater Himalayan Crystalline complex above and the Lesser Himalayan Sequence below (e.g., Heim and Gansser, 1939; Le Fort, 1996; Hodges, 2000; Yin, 2006). This defi nition is uncertain because of debates over which local lithological units should be attributed to which tectonic unit, and it is circular, since the Greater Himalayan Crystalline complex and Lesser Himalayan Sequence are defi ned by their bounding structures (see discussion by Upreti, 1999). Nonetheless, for the Himachal Himalaya most workers share a consensus interpretation of the MCT as a continu-ous, folded, southwest-directed thrust shear zone as much as 2 km thick that was active in the Early and Middle Miocene and has a largely estab-lished map trace (as shown in Fig. 3) (e.g., Thakur and Rawat, 1992; Frank et al., 1995; Steck, 2003; Vannay et al., 2004). This interpretation is based on congruent lithology, strain concentration, metamorphic grade, and ther-mochronologic ages along the mapped shear zone (e.g., Frank et al., 1995; Grasemann et al., 1999; Vannay et al., 2004; Thiede et al., 2005). The MCT hanging-wall rocks show variation; at its northeasternmost trace along the Sutlej River, the MCT underlies a well-established inverted metamorphic sequence that is universally acknowledged as Greater Himalayan Crystal-line complex rocks (Fig. 3) (e.g., Vannay and Grasemann, 1998; Hodges, 2000; Steck, 2003; DiPietro and Pogue, 2004; Yin, 2006). Conversely, it has long been recognized that the MCT hanging-wall rocks to the west of Mandi (i.e., west of ~31°50′N, 77°E) display a right-way-up metamorphic fi eld gradient to chlorite zone conditions and are structurally continuous with the Tethyan Himalayan Sequence to the northeast (Fig. 3) (Frank et al., 1995; Fuchs and Linner, 1995; Thakur, 1998; Steck, 2003; DiPietro and Pogue, 2004; Yin, 2006). Therefore the Himachal region requires a relaxation of the MCT defi nition as the boundary between the Greater Himalayan Crystalline complex and the Lesser Himalayan Sequence.
Based on the change in hanging-wall rocks, we divide the MCT into northern and southern segments. The northern MCT juxtaposes the Greater Himalayan Crystalline complex over the Lesser Himalayan Sequence; the southern MCT places the Tethyan Himalayan Sequence and the Baragaon gneiss over the Lesser Himalayan Sequence (Fig. 3). The intersection line of the STD and the MCT marks the boundary between the two segments of the MCT to the north and south (Thakur, 1998; Yin, 2006; Webb et al., 2007). In subsequent text, we refer to the “MCT zone” if the ~2 km thick-ness of the shear zone is relevant.
In the map area the MCT is folded and displays large full and half- windows and isolated klippes (Fig. 3). Cutoff relationships in the MCT foot-wall suggest that the thrust cuts upsection to the southwest in its transport direction. However, the presence of a large footwall ramp along the MCT in the map area raises the question of whether the Lesser Himalayan Sequence strata in the footwall ramp were horizontal when the MCT was initially cut-ting across them. As Cretaceous–Eocene beds overlie the Shimla Group and Tal Formation of the younger Outer Lesser Himalayan Sequence units in the south and the Deoban-Damtha strata in the north (Srikantia and Sharma, 1976; Valdiya, 1980) (Fig. 3), the Proterozoic–Cambrian sequence of the northern Indian passive margin must have been tilted to the south prior to the emplacement of the MCT hanging wall in the region.
Minimum displacement along the MCT in the map area is ~115 km, determined from the northernmost and southernmost exposures of the fault. Early to Late Miocene activity on the northern segment of the MCT has been inferred from U-Th monazite-inclusion dating, 40Ar/39Ar mus-covite cooling ages, and zircon fi ssion track ages from the Greater Hima-layan Crystalline complex hanging-wall rocks (Fig. 4A) (Walker et al., 1999; Schlup, 2003; Vannay et al., 2004; Thiede et al., 2005). The portion of the MCT across the Kullu and Uttarkashi windows must have ceased
2Supplemental File 2. PDF fi le of 87Sr/86Sr (500 Ma) vs. εNd
(500 Ma) plots for the western and central Himalaya. In the Nepal Himalaya, Nd and Sr isotopic compositions and detrital zircon age distributions are different in the Lesser Hi-malayan Sequence (LHS), Greater Himalayan Crystalline complex (GHC), and Tethyan Himalayan Sequence (THS). It has been proposed that such data can be used to identify the structural setting of Himalayan strata (e.g., Parrish and Hodges, 1996). However, rocks of the same age in the Lesser Himalayan Sequence, Great-er Himalayan Crystalline complex, and Tethyan Himalayan Sequence have the same isotopic compositions and detrital zircon patterns (e.g., Myrow et al., 2003; Richards et al., 2005). This suggests that distinctions from isotopic and detrital zircon signatures in Himalayan rocks cannot be used directly to infer structural setting. Such distinctions are nonetheless valuable for constraining age ranges of Himalayan strata and thus for making stratigraphic comparisons. Neoproterozoic and younger rocks are generally distinguishable from Mesoproterozoic and older rocks in 87Sr/86Sr (500 Ma) vs. ε
Nd (500 Ma) space. (A) 87Sr/86Sr (500 Ma) vs.
εNd
(500 Ma) plot for western and central Himalaya rocks. Data for this plot are divided into three plots to ease tracking of data for individual units. (B) 87Sr/86Sr (500 Ma) vs. ε
Nd (500 Ma) plot for Himachal Himalaya rocks. Data from Bhat
and Le Fort (1992, 1993), Miller et al. (2000, 2001), and Richards et al. (2005). (C) 87Sr/86Sr (500 Ma) vs. ε
Nd (500 Ma) plot for Kumaun and Nepal Himalaya
rocks (Kumaun Himalaya—northwest India Himalaya to the east of Himachal Pradesh). Data from Ahmad et al. (2000), Deniel et al. (1987), France-Lanord et al. (1993), Inger and Harris (1993), and Prince (1999). (D) 87Sr/86Sr (500 Ma) vs. ε
Nd (500 Ma) plot for western Himalayan (Nanga Parbat) syntaxis rocks. Data
from Argles et al. (2003), Foster et al. (2000, 2002), Gazis et al. (1998), George et al. (1993), and Whittington et al. (1999). If you are viewing the PDF of this paper or reading it offl ine, please visit http://dx.doi.org/10.1130/GES00627.S3 or the full-text article on www.gsapubs.org to view Supplemental File 2.
Webb et al.
1022 Geosphere, August 2011
motion in the Late Miocene when these windows were developed and caused folding of the MCT, as indicated by cooling ages (Vannay et al., 2004; Thiede et al., 2005; Caddick et al., 2007; Chambers et al., 2008). However, the relationship does not preclude the southernmost MCT link-ing younger thrusts in the Lesser Himalayan Sequence to continue its motion after the Middle Miocene.
STD
The STD juxtaposing the Tethyan Himalayan Sequence over the Greater Himalayan Crystalline complex can be traced continuously from the central Himalaya to the northern end of the Kullu window (Figs. 1 and 3) (Burg et al., 1984; Burchfi el et al., 1992; Choudhuri et al., 1992; Thakur, 1998; Dèzes et al., 1999è; Jain et al., 1999; Wyss et al., 1999; Steck, 2003; DiPietro and Pogue, 2004; Yin, 2006). Here the STD is folded and overturned within the southwest-verging Phojal anticline, and the overturned fault trace extends back to the southeast and intersects the MCT on the north and south sides of the eastern Kullu window and at the northwestern rim of the Uttarkashi window (Fig. 3) (Thakur, 1998; Webb et al., 2007). The MCT-STD branch line trends to the northwest, parallel to the strike of the orogen. It is largely buried to the northwest and eroded to the southeast. In the Himachal Himalaya the fault features both top-to-the-northeast and top-to-the-southwest structures, including S-C fabric,
normal drag shear bands, σ-type porphyroclasts, and asymmetric isocli-nal to tight folds, across a 300–600-m-thick shear zone (Choudhuri et al., 1992; Jain et al., 1999; Vannay et al., 2004; our observations).
The Zanskar shear zone represents a possible northwestern extension of the STD (Figs. 1 and 3) (e.g., Searle, 1986; Herren, 1987; Patel et al., 1993; Dèzes et al., 1999; Epard and Steck, 2004). The northwest-trending, northeastern segment of this shear zone has been interpreted as (1) an along-strike continuation of the STD, connected in map view to the right-way-up STD across the Himachal Himalaya (e.g., Searle et al., 1988; Jain et al., 1999), or (2) as part of an STD window (Thakur, 1998; Dèzes, 1999; Yin, 2006). We follow the second interpretation because of the established continuity of the Tethyan Himalayan Sequence from Chamba to the Tso Morari, i.e., weakly deformed rocks cross the path of the proposed STD–Zanskar shear zone map-view connection (e.g., Frank et al., 1995; Fuchs and Linner, 1995). Because the Zanskar STD window is warped but not overturned, it follows that the Phojal anticline is a local structure along the northern margin of the Kullu and Uttarkashi windows that does not extend to the Zanskar region.
The amount of displacement along the STD is diffi cult to determine because rocks above and below the fault share the same protoliths in this region. Also, there is no pronounced metamorphic offset across the fault: metamorphic isograds are subparallel to the STD (Fig. 5). Therefore, despite the signifi cant evidence for shear deformation across the STD
Sillimanite-in isograd
Kyanite-in isograd
Biotite-in isograd
Garnet-in isograd
Ultra-highpressure(UHP) rocks
Isograd minerals occur on the side of each isograd curve marked by a filled semi-circle.
Tso Morari UHP dome
Tso Morari UHP dome UHP
Sillimanite / Andalusite contact
metamorphism
Sillimanite / Kyanite contact metamorphism?
Figure 5. Metamorphic isograd map of the Himachal Himalaya, with (1) largely continuous garnet-in and kyanite-in iso-grads and (2) discontinuous biotite-in and sillimanite-in isograds (due to incomplete metamorphic mapping). Main references are Frank et al. (1973), Epard et al. (1995), and Vannay and Grasemann (1998); see Appendix 1 for additional references.
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1023
zone, local lithologic and petrologic information do not constrain the mag-nitude of fault offset. The fault may have initiated in the Eocene as a basal décollement of the Tethyan Himalayan fold-thrust belt (Wiesmayr and Grasemann, 2002). Early to Middle Miocene 40Ar/39Ar muscovite ages in the immediate STD hanging wall and footwall suggest that plastic defor-mation along the STD ceased in that period (Walker et al., 1999; Vannay et al., 2004; Thiede et al., 2005).
Most Tethyan Himalayan Sequence strata northeast of the right-way-up STD are involved in the dominantly top-to-the-southwest Tethyan Hima-layan fold-thrust belt within the Spiti Synclinorium (Figs. 3 and 4B) (e.g., Frank et al., 1995; Fuchs and Linner, 1995; Vannay and Steck, 1995; Steck et al., 1998; Wiesmayr and Grasemann, 2002). Similar relationships also occur across the Chamba Synclinorium in the northwest of our map area (e.g., Frank et al., 1995; Fuchs and Linner, 1995). To the north, Tethyan Himalayan Sequence rocks and suture zone rocks are thrust northeastward over the Indus molasse along strands of the latest Oligocene–Miocene Great Counter thrust system (e.g., Schlup et al., 2003; de Sigoyer et al., 2004). The Great Counter thrust system may represent the northern exten-sion of the STD (e.g., Yin et al., 1994, 1999).
STRUCTURAL GEOLOGY
Thrusting is the dominant expression of contractional deformation in the footwall of the MCT. Although many of these thrusts are well defi ned locally, the relationships among the structures and deformation in individ-ual thrust systems have not been studied in detail. Further issues include: (1) MCT-STD geometric relationships, (2) internal deformation of units to address the assumption of constant bed thickness in line-length balancing, and (3) variable deformation style and strain as functions of both lithology and structural positions relative to nearby faults. To address these issues, we conducted detailed geologic mapping and outcrop-scale observations across the Himachal Himalaya. We summarize the main results of our structural observations in the following.
Mandi-Bilaspur Thrust System Hanging-Wall Structures
Bedding in the Deoban and Damtha Groups is deformed by brittle structures, including dominantly southwest-verging parallel folds and dominantly southwest-directed brittle faults (Figs. 6B, 6D [stereoplots L3, L4, L6, L7], 7A, and 7B). Fold amplitudes range from 50-m-thick schuppen zone comprising 2–15-m-thick horses of quartzite, granitic schist, and granitic gneiss. Gneissic fabric across the Munsiari Group is characterized by a dominantly north-northeast–trending stretching linea-tion (Figs. 6B–6D). Gneissic foliation in the Jeori gneiss unit exposed in the Sutlej River Valley (~15 km northeast of Rampur) is penetratively deformed by kink folds with centimeter- to meter-scale wavelengths and ~90° interlimb angles (Fig. 7H). Along a 10 km stretch of the Sutlej River in the eastern Kullu window (centered on the town of Wangtu), unfoliated pegmatitic granites crosscut the foliation of the Wangtu granitic gneiss (Fig. 7I). The Late Miocene ages of these granites provide a lower limit for the development of the gneissic fabric (see following Geochronology dis-cussion). These granites are the only unit within the Munsiari thrust hang-ing wall, and indeed within the Lesser Himalayan Sequence, for which we did not observe outcrop-scale deformation.
Webb et al.
1024 Geosphere, August 2011
MCT and Hanging-Wall Structures
We divide the MCT into northern and southern portions based on Greater Himalayan Crystalline complex and Tethyan Himalayan Sequence hanging-wall lithologies, respectively. This division is structurally defi ned by the overturned South Tibet detachment, which is folded with the south-west-verging Phojal anticline. In this interpretation, the southern MCT hanging wall is continuous with the STD hanging wall. Therefore deter-mining the deformation style and strain of the southern MCT hanging wall, the northern MCT hanging wall, and the STD hanging wall provides key tests of the interpretation. We review our main structural observations from each area in the following.
Southern MCT and Hanging-Wall StructuresObservations of deformation in the MCT hanging wall south of the
Kullu window are limited because (1) most preserved rocks are near the
base of the thrust sheet, with structurally high rocks largely eroded away, and (2) despite this knowledge, the undulatory folding of the thrust sheet limits our ability to tightly constrain structural elevation above the MCT base across much of the thrust sheet. This portion of the MCT is defi ned by a 1–2 km top-to-the-southwest shear zone featuring S-C fabrics with northeast-trending stretching lineations defi ned by biotite and feldspar, normal drag shear bands, ultramylonites, σ-type porphyroclasts of feld-spar, brittle-ductile synthetic and antithetic microfaulting of feldspar, and tight to isoclinal folds [Figs. 6A, 6B, 6D (stereoplots TG1, T5, T6, T7, T8), 8A, and 8B]. The base of the shear zone is largely coincident with the garnet isograd within an inverted metamorphic fi eld gradient (Fig. 5). Where the MCT juxtaposes Haimanta rocks directly above Outer Lesser Himalaya rocks (at Narkanda and along the Shimla klippe), mylonitic garnet schist of the MCT zone concordantly overlies pelitic phyllite, chlorite-pyrite schists, and graphitic phyllite, and graphitic schist. Here shear bands and isoclinal folds persist across ~400 m structurally below
Figure 6 (continued on following pages). (A) Geological map of the Upper Beas Val-ley region. (B) Geological map of the central Sutlej River region. Gray structural data are from this study; blue structural data are taken from the literature and were used for cross section construction. (C) Geologi-cal map of the northeastern Sutlej River region. Topographic contours in A, B, and C are from the Shuttle Radar Topography Mission; in some areas these data are dis-torted (e.g., at 32°25′N, 76°50′E). (D) Equal area stereoplots for regions labeled in A, B, and C. The regions were selected on the basis of shared and/or similar structural set-ting and geographic proximity. The regions and stereoplots are labeled with letters and numbers in order to denote different regions (numbers) within different tectonic units (denoted by letters) (e.g., L1—Lesser Himalayan Sequence, area 1; G2—Greater Himalayan Crystalline complex, area 2; T4—Tethyan Himalayan Sequence, area 3). The abbreviations are the same as in the leg-end in Figure 3.
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1025
Figure 6 (continued).
Webb et al.
1026 Geosphere, August 2011
Figure 6 (continued).
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1027
Figure 6 (continued).
N total = 10n=4 (foliation)n=5 (stretching lineation)n=1 (fold axis)
0°
N total = 11n=1 (bedding)n=6 (foliation)n=2 (stretching lineation)n=2 (fold axis)
0°
N total = 55n=27 (foliation)n=22 (stretching lineation)
n=3 (axial plane)n=2 (fold axis)
n=1 (R1 shear)
0°
N total = 33n=15 (foliation)n=13 (stretching lineation)n=5 (fold axis)
0°
N total = 19n=11 (foliation)n=6 (stretching lineation)n=2 (fold axis)
0°
N total = 27n=14 (foliation)n=13 (stretching lineation)
0°
N total = 17n=4 (bedding)n=6 (foliation)
n=5 (fault)n=1 (fold axis)
n=1 (stria)
0°
N total = 74n=32 (bedding)n=14 (foliation)
n=9 (fault)n=1 (stria)
n=2 (axial plane)n=4 (fold axis)
n=1 (R1 shear)
n=9 (stretching lineation)
0°
N total = 7n=3 (foliation)n=1 (stretching lineation)n=3 (fold axis)
0°
N total = 61n=29 (foliation)n=12 (stretching lineation)
n=3 (axial plane)n=9 (fold axis)n=4 (S Plane)n=3 (C plane)
n=1 (fault)
0°
N total = 60
n=28 (foliation)n=21 (stretching lineation)
n=1 (bedding)
n=3 (fault)n=2 (axial plane)n=5 (fold axis)
0°
N total = 29n=11 (foliation)n=7 (stretching lineation)
n=4 (fold axis)n=2 (axial plane)
n=2 (C plane)n=2 (S plane)
n=1 (Extensional shear band)
0°
N total = 23n=13 (foliation)n=10 (stretching lineation)
0°
N total = 15n=8 (foliation)n=7 (stretching lineation)
0°
N total = 47n=22 (foliation)n=18 (stretching lineation)
n=3 (axial plane)
n=1 (C plane)n=3 (fold axis)
0°
N total = 16n=8 (bedding)n=6 (fold axis)n=2 (fault)
0°
N total = 92
n=13 (fold axis)
n=47 (foliation)n=26 (stretching lineation)
n=2 (fault)n=2 (stria)
n=1 (C plane)n=1 (S plane)
0°
N total = 411n=227 (foliation)n=107 (stretching lineation)
n=35 (fold axis)n=6 (S plane)n=11 (C plane)
n=3 (R1 shear)
n=13 (fault)n=3 (stria)
n=5 (axial plane)
0°
N total = 37n=18 (foliation)n=14 (stretching lineation)n=4 (fold axis)n=1 (fault)
0°
N total = 52n=26 (foliation)n=21 (stretching lineation)n=3 (fold axis)n=2 (axial plane)
0°
N total = 36n=24 (foliation)n=9 (stretching lineation)n=2 (fold axis)n=1 (axial plane)
0°
N total = 24n=4 (bedding)
n=2 (fault)
n=1 (fold axis)n=1 (axial plane)
n=9 (foliation)n=6 (stretching lineation)
n=1 (stria)
0°
N total = 63n=4 (bedding)n=36 (foliation)
n=8 (fold axis)n=10 (stretching lineation)
n=3 (fault)n=1 (R1 shear)
n=1 (axial plane)
0°
T1 T3T2
T4 T6T5
T7 T9T8
GT1 G2G1
L1 L3L2
G3 G5G4
L4 L6L5
L7 L8
D
Webb et al.
1028 Geosphere, August 2011
AA
cover
Southwest
1 m
Southwest
1 m
10 m
Southwest
MCT
DeobanGroupcarbonates
Baragaon gneiss
Southwest
MCT
10 m
BB
Southwest
5 cm
Southwest
5 cm
Quartzvein
CC
Northwest
10 cm
coverDD
Cenozoic tectonic history of the Himachal Himalaya
Geosphere, August 2011 1029
30 cm
N
150 cm
300 cm
260 cm
Total restored bed lengthis 560 cm
Final bed length
Horizontal shortening strain = (150-560)/560 = -73%
S1
S1
S0
E
Figure 7 (continued on following pages). Field photographs of the Main Central thrust (MCT) footwall (locations marked in Figs. 6A, 6B, 6C). All photographs were taken in the Sutlej River Valley except for 6D, which was taken along the Shimla-Narkanda Road. (A) Thrust fault system within the Deoban Group with associated folds. (B) Folding and duplexing of Deoban carbonates beneath the MCT. Here the base of the MCT is a brittle fault, with fractures interpreted as Riedel shears. (C) Tight similar folds in Deoban carbonaceous schist within the MCT zone. (D) Tight folding of Shimla Group rocks. (E) Folding of Shimla Formation rocks with preserved S0, shortening estimate. (F) Cross-bedding preserved in Berinag Group quartzites. (G) Tight to isoclinal folds in Berinag Group quartzites, same site as F. (H) Kink folds of Jeori