DECCAN TRAP - Introduction/ Geographical Distribution/ Geological Age / Geology Structure/ Petrology / Stratigraphic Classification / Age / Bagh Bed / Lameta Bed / Intertrappean bed /Infratrappean bed

                                     Deccan Trap:

Introduction:

• The deccan Trap is largely made up of lava flow of basic composition.

•  The age of these Lava flows ranges from Upper Cretaceous to Lower Eocene.

Geographical Distribution:

• The deccan Traps Covers an Area of over 500- 1000 km sq in the central and western parts of India.

•  They occupy major parts of Gujarat, Madhya Pradesh , Maharashtra and some part of the   Andhra   Pradesh. 

• The deccan Trap Attain Maximum Thickness of About 20000m.

• The approx. Thickness of the deccan Volcanies is about 3000m.

• These Volcanics are Dominantly Sub- Aerial  flows of Theolitic basalt with Subordinate picrite basalt and Alkaline Basalt.   

   

 

GEOLOGICAL AGE:

• The deccan volcanics have erupted close to the cretaceous - Tertiary Boundary (CT Boundary)  about 65 Mn.

    

     GEOLOGY:

•  The volcanism related to catastrophic event of mass extinction (like dinosaurs) throw in Bolites in beds and global climatic change.

  

    STRUCTURE:

• The deccan trap flows are generally horizontal  in Altitude but gentle dips of the order of 10 degree have also been observed at some places.

     PETROLOGY:

• The majority of the deccan trap flows are basalt with a uniform chemical composition but rocks like rhyolite, Granophyre, Nepheline , Syenite etc have also been found.

   

    STRATIGRAPHIC CLASSIFICATION:

• To study the stratigraphic classification click on the given link    CLASSIFICATION TABLE.

  AGE OF DECCAN TRAP :

      The deccan traps have been regarded as of Paleocene age on the basis of following evidences:

• The deccan traps overlie the Bagh and Lameta beds which are of middle Cretaceous age.

    

• Near Ranikot in sind (Pakistan), lava flows similar to the deccan traps occur interstratified with the "Cardita Beau Manti beds of upper Cretaceous age.

     

• In the Saurashtra area of Gujarat the "Nummulitic beds " of lower Eocene age rest unconformably over the deccan traps.

   

  BAGH BED:

   The late Cretaceous marine sediments of Central India prevalently known as Bagh Bed , have been         deposited in the east- west extending Narmada basin.

 LAMETA BED:

   The Lameta Formation also known as Infratrappean beds is a   sedimentary geological formation           found in Madhya Pradesh, , Gujarat and Maharashtra  associated with Deccan Traps.

 INTERTRAPPEAN BEDS:

• These are sedimentary beds found associated with deccan trap lava flows.

      

• They are made up of Shales, Impure Limestones and Volcanic detritus of Lacustrine and Fluviatile origin.

       

• The individual beds are usually 1-3 meter thick and extend laterally for 5-8 kms.

      

• The Intertrappean beds have yielded a rich faunal and floral assemblage.

      

• The Flora is mainly palm (Palmoxylon). The invertebrate fossils include "Physa princepii" , "Lymnaea", "Paludina", "Natica" etc.

      

• The Vertebrate fossils are mainly frogs , Tortoises and Fresh water Fishes.

      INFRATRAPPEAN BEDS:

• The rocks that underlie the deccan traps are called Infratrappean beds.

       

• They range in age from  Precambrian to upper cretaceous .

       

• However, in normal uses only these strata which are very close in age usually upper cretaceous to the deccan traps and are underlying dams are Infratrappean.

       

• Infratrappean beds are found in part of Gujarat (Balasinor) , Madhya Pradesh (Jabalpur) , Maharashtra (Mumbai)  and Andhra Pradesh (Nastal , Asifabad , Rajmudry).

      

• It is notable for Dinosaur fossils.