first of all it should be considered that for appearing in gate exam you have to have a graduation degree of atleast four years . however for gate exam bsc would be better in my view . checkout the ligibility criteria of gate exam

https://engineering.careers360.com/articles/gate-eligibility-criteria

for getting a better answer you should compare the syllabus of bsc geology and gate geology exam .here is gate geology syllabus

http://www.gate.iitg.ac.in/Syllabi/GG_Geology-and-Geophysics.pdf

.check out the syllabus of BA/b.sc of your college and compare it with gate exam

Hi Candidate,

The eligibility criteria to give GATE exam in Geology is given below:

Candidate must have a minimum of 60%* aggregate marks in B. Sc. also additionally, eligible candidates must have passed Mathematics in Std. XII. All applicants opting to be considered on the basis of a GATE Score should have a valid GATE-2018 or GATE-2019 Score in 'Geology and Geophysics'. All the best