There's no common entrance test conducted specifically for BSC geology all over India. You need to apply for colleges/universities that you are targeting separately. The specific college might conduct an entrance exam or it is also possible that they'll only take admissions on the basis of your 12th marks. You need to apply for colleges in order to get admission. I'm attaching a link below from where you can all the necessary information like aggregate fees of college per annum, top colleges for the course, etc.

https://collegedunia.com/courses/bachelor-of-science-bsc-geology