physiographic division of india(2)

5.     Gondawana System. : -                                                                                     

a) Introduction --   After the deposition of Vindhyan system there was a great period of non-deposition in the stratigraphy of peninsula.

·        The name Gondawana comes from area of south of Narmada by the Gondas were first studied.

·         It is made of deposition in the slowly sinking faulted trough.      

·         B]Distribution :- 1. A large tract in West Bengal along Damodar valley & Rajmahal hills  2. along Mahanadi Valley  3. Along Godawari River & Penganga near Nagpur        4 .Cutch, Rajasthan, Saurashtra, Wardha, Yeotmal, Nagpur, Chandrapur        district of Maharashtra.

Classification:-                

          Upper Gondwana                                Umia                                        fossil

                                                                        Jabalpur                 tlyllophyllum flora

          Middle Gondwana                                 Rajmahal                Da crodium flora

                                                                        Mahadev

                                                                        Panchet

         Lower Gondwana                                    Damuda                   Raniganj [coal]

                                                                                                           Barren measure  

                                                                                                             Barakar [coal]

                                                                                                            Karharbari

                                                                        

                                                                                     Glossoptris & gongamopteris                                                                

                                                                            Talchir  

                                    

b)     Lithology: - Shale, sandstone, conglomerate, coal seam, intrusion of dolerite dyke.

c)     Age: - Carboniferous to Jurassic.                                                                                

d)     Indian coal: - The economic importance of the Gondwana is that they are the major source of coal in India. 80% of all coal comes from lower Gondwana [Damuda] i.e. both in the Barakar & Raniganj series.

 The important coal fields in India are

1.     Raniganj coal field.       2. Jhariya coal field.       3. Bokaro coal field.

      4.  Rampura coal field.        5. Singareni coal field.     6. Giridih coal field.

Coal field in Maharashtra: -     1. Kamtee coal field.      2. Bokaro coal field.

     3.Umrer coal field.          4  Wardha coal field. 5 Ballarpur coal field

6   Ghuhus coal field  7 Rajura coal field 8 Worora coal field

6. Deccan Trap :-                                                                                                        

 a) Introduction: -    At close of cretaceous period, large part of peninsula was affected by volcanic activity. This result into a thick series of lava  pyroclastic  material. Eruption of magma through  fissures.  Such type of eruption is called fissure type of  eruption .These flows are horizontal, they look like flat plateau & their composition  is basaltic so they are called plateau basalt. They are called Deccan trap because of their step like appearance.

b) Distribution: - 85% of area of Maharashtra & wide area of M. P., Gujarat, A. P., Karnataka. Maximum thickness of lava 3000 mt.

c) Lithology: - Plagioclase Augite basalt, Vesicular, compact, Amygdaloidal basalt, Trachyte, Rhyolite, Andesite  ,diorite gabbro.

d) Types of basalt:-                                                                                                                    

1) Giant phenocryst Basalt. (2 to 10 cm)  length of plagioclase.

2) Compact Aphanitic Basalt.      

 3) Hydrothermal altered Basalt.

4) Amygdaloidal Basalt with large amygdales.

 5) Amygdaloidal Basalt with medium amygdales.   

 6) Amygdaloidal Basalt with small amygdales.

 7) Amygdaloidal Basalt with pipe amygdales.

8) Vesicular Basalt.   

9) Porphyritic Basalt. 

10) Tachylytic Basalt (Red, green, black).

11) Red Tachylytic Basalt.

 12) Volcanic breccias

 13)  Volcanic breccias with gray lava matrix.

14) Volcanic breccias with R.T.B.  

 15) Volcanic breccias with Zeolite matrix.