Himalayan Geology

Geology of Himalayas

Image credits : Indus discoveries

Himalayan orogeny is the most recent one and resulted in formation of some highest peaks of the world. Tectonics are continental- continental collision when Indian plate collided with Eurrasian plate about 55 Mya. As continental crusts are already thicker in themselves, collision resulted in doubling of continental crust and thus, high mountains rises.

Continental - Continental collision

In this tectonic setting, crust crumples and thickens, resulted in formation of high mountains and wide plateau. In case of Himalayas, Tibetan plateau was formed which one of world's largest plateau. Moho boundary lies very deep in these cases.

Origin 

• In Triassic, when Pangea fragmented, Indian plate separated and started moving towards north.

• Northernmost part of Himalayas is Indus Sangpo suture Zone (ITSZ) which is consisted of ophiolites and melanges (tectonic breccia).

• Next to it lies Southern Tibetan Decollement (STD). It is a normal fault.

• After it's long journey, it collided with Eurrasian plate in Eocene when Main Central Thrust (MCT) was formed. Later, Main Boundary Thrust (MBT) and Main Himalayan Thrust or Himalayan Frontal Thrust were created.

• During late pliocene, the sea was closed.

• Fore land of this collision is Ganga basin.

Divisions of Himalayas

Himalayas can be divided into 5 parts as shown in picture above

Sub-Himalayas are composed of Neogene rocks, Siwalik ranges, while Lesser Himalayas are of Paleogene rocks.

Tethys Himalayas are composed of ophiolites which are the slices of ancient sea Tethys' crust. Dras volcanics is also present in Tethys region. These are of cretaceous age.