Physiographic divisions of india

                                      Indian Geology

I)                  Physiographic  divisions of India;-

The Indian sub –continent may be divided physiographically into following three divisions.

1) Peninsula     (Triangular portion of south)

2) Indo- gangatic plain (It separates peninsula from extra peninsula)

3) Extra- peninsula (mountain region bordering India on NE, N and NW Himalaya ranges. The peninsula and extra- peninsula are quite unlike each other in geological structure, geological history and physiogra

1)  Geological History: - Since Cambrian times the peninsula has always remained a landmass and has never been submerged under the sea except locally in the coastal regions. No marine deposits are found. On the other hand Extra Peninsula has been under the sea for greater part of history. Hence it covered by huge amount of marine deposits.

   2) Geological structure – Peninsula represents a stable block which has not been affected by    orogenic earth movements. The oldest rocks are gently dipping and do not show complicate folding. Extra Peninsula on the other hand represents a weak, flexible portion of the earth’s crust that has undergone the more tightly packed folds, faults and over thrust high angle dip of strata.

3) Physiography;-peninsula –mountains are Relict type and rivers reached old stage has been rejuvenated. Extra-peninsula Mountains are tectonic mountain; Rivers are youthful stage still active down cutting their channels & have produced gorges. 

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Formations.

 Recent     Holocene                         Latrite / Alluvium

Cretaceous to Eocene                            Deccan Trap

Carboniferous to Jurassic                         Gondwana system

                                                            No Deposit

                                                            Vindhyan system

Pre-Cambrian Age                              Cuddapha system

                                                              Dharwar system

                          Archean system

1)       Archean   system - Oldest, stable, Azonic  (un fossil ferrous), crystalline, highly metamorphosed rock. Folded & faulted, well foliated, intruded by plutonic intrusion. Because of all these things Archaean rocks are known as complex & hence they are known as Basement complex or Fundamental .Complex rocks are gneiss and schist.Archaean rocks covered more than 2/3 part of peninsula.

2) Dharwar system. :-

a) Introduction - The name comes from Dharwar district in Karnataka state where first studied.                                                                                                  

 b) Distribution – Dharwar, Mysore, Bellary, state of Karnataka, Goa, Nilgiris, M.P. Bihar, Orissa, Bengal, Assam, Maharashtra (Nagpur, Bhandara, Chandrapur, Nanded) Jaipur & Gujarath.

c) Lithology - Hornblende schist, chlorite schist, Talc schist, mica schist, intrusion of dolerite, pegmatite dyke.

d) Structure: - Highly folded, faulted, steeply dipping beds, intruded by dyke

e) Age: - Pre- Cambrian.