Hello Nisha,

The topics in the syllabus for IIT-JAM Geology is - 

• The Planet Earth
• Palaeontology
• Structural Geology
• Mineralogy
• Stratigraphy
• Economic Geology
• Petrology

Some of the important reference books with all contents are - 

• Geology - Physical geology – Mukherjee
• Palaeontology - Introduction to Palaeontology by Arnold
• Mineralogy - Mineralogy - Dexter Perkins/ Cornelis Klein
• Structural Geology - Structural Geology - Prof. Haakon Fossen
• Geomorphology - Geomorphology- M. J. Selby
• Stratigraphy - Stratigraphic principles and practice by Weller, J.M
• Economic Geology - Industrial minerals and rocks of India by Deb
• Petrology - An Introduction to Igneous and Metamorphic Petrology by John D. Winter
• Applied Geology - Hydrogeology - Todd and Karanth, Ground water by H.M.Ragunath
• Other books - Engineering Geology - Krynine and Judd, Engineering Geology - K.M.Bhangar

You should start studying as soon as possible, make a time table and follow it. Practice previous sample question papers.

More Details - https://university.careers360.com/articles/how-prepare-jam-geology