Examples of modern orogenic belts - Introducing Tectonics, Rock Structures and Mountain Belts - page 90

Cambrian-Eocene
Tethyan shelf sequence
Greater Himalayan
crystalline complex:
Late Proterozoic clastics
Lesser Himalayan schists:
Mid-Proterozoic clastics

South Tibet

ITS/RZT

Tethyan shelf
sequence

STD

MCT

Lesser Himalayan
schists
Siwalik
Formation

Greater Himalayan complex

Indian foreland

Siwalik Formation:
foredeep basin

MCT

250km

HFT

A

STD

RZT

Asian
plate

MBT

HFT MCT

0km 0km

lithosphere

20

20

40

40

late orogenic granites
syn-orogenic granites

B

Figure 11.3 A, B. Map (A) and cross-section (B)
of the main Himalayan mountain belt between
the South Tibet block and the Indian foreland,
showing the main tectonic units, from north to
south: Cambrian to Eocene Tethyan shelf unit;
Greater Himalayan crystalline complex; Lesser
Himalayan schists; Siwalik foredeep basin; the
thrusts separating these units are: RZT, Renbu-
Zedong thrust (Indus-Tsangpo suture); STD, South
Tibetan detachment; MCT, Main Central thrust;
MBT, Main Boundary thrust; HFT, Himalayan Frontal
thrust. Note the syn-orogenic granites near the STD
boundary and the late orogenic granites within the
Tethyan sequence. Modified from Harrison (2006). C.
Simplified cartoon cross-section illustrating how the
general structure of the orogen may be derived from
an initial platform cover resting on Indian Archaean
basement by pushing from the leading edge of
the Asian plate, acting as a kind of plunger, along
the top of the basement. Note that, for simplicity,
the two Proterozoic formations are regarded here
as laterally equivalent and differing only in their
degree of metamorphism. Also, the platform cover
on the foreland (Siwalik formation) is approximately
time-equivalent to the Tethyan sequence in the
northern part of the belt. D. Simplified cross-
section through the central sector of the orogen
to illustrate the contrasting arrangement of crust
and lithospheric mantle between the Indian and
Asian plates, based on Searle et al. (2011).

Mesozoic-Tertiary
platform cover

Proterozoic clastic sequence

Asian plate

C

Himalayas

South Tibet

HFT MBT MCT STD

ITS North Tibet

GB

BNS

GB

brittle faulting

Indian crust

GHC

ductile flow

100km

Indian
lithospheric
mantle

Asian
lithospheric
mantle

eastward
lateral
flow

D