B.Sc Geology

JEE is only for B.Tech courses, it is not not applicable for other Bachelor's courses.

Basic eligibility for candidate to apply for B.Sc from Dr. B.R. Ambedkar Open University, Hyderabad is that candidate should have cleared their intermediate examinations with Science. You should clarify with the relevant authorities if your diploma is equivalent to intermediate examinations so that you may be eligible to apply or you should have One year work experience in any Science & Technology Organisation. Regards.

Some popular colleges which offer geology course in Chennai are mentioned below:
1) Presidency College
2) Air Force Administrative College
3) Department of Applied Geology, University of Madras
4) Department of Geology, University of Madras
Regards.

Yes, you can study geology at UG level and then after that, you can do Post Graduate Diploma or MA in Archaeology.
The best colleges are:
ICHR, New Delhi
MS University, Baroda
Banaras Hindu University
Mumbai University
Madras College of Archaeology

Please download the brochure of this particular college from the link provided below which contains important details like admission criteria, eligibility and important application dates for M.Sc courses offered by the college.
Link:
https://www.shiksha.com/college/sinhgad-college-of-science-ambegaon-bk-pune-52919

Please refer to the link provided below for details about admissions in St. Xavier's College in Ranchi. You should be able to download their brochure which contains important details like last application dates, admission criteria and eligibility for B.Sc courses in this college.
Link: https://www.shiksha.com/college/st-xaviers-college-ranchi-10300

Most colleges require that you pass all core subjects before you can successfully apply for a course in higher education. It could also mean that you can apply for a course in B.Sc. Geology provided you clear your examinations before date of commencement. Moreover, if maths is not one of your core subjects, then you can take the best 4 and apply for B.Sc in geology.