List of top Geology Questions on Geochronology

An unconformity where sedimentary layers are deposited over eroded igneous or metamorphic rocks is called a?

Which type of fault occurs when the hanging wall moves downward relative to the footwall?

If the Rb-Sr isochron formed by a suite of gabbro samples has a slope of 0.0265, then the calculated age of the gabbro in million years is_____. (in integer).
[Use λ(⁸⁷Rb) = 1.42 x 10^-11 year^-1]

The rate of spreading about a symmetric spreading center at the middle of a 4000 km wide sea is 40 mm/year. The spreading began $\underline{\hspace{1cm}}$ million years before present. [in integer]

The given section with uniform lithology and sedimentation rate records two ash layers dated at 77 Ma and 76 Ma, respectively. An index fossil species present in the lower part of the section becomes extinct at a horizon 7 m above the base. The estimated age of the extinction event is _________ Ma. (Answer in integer.)

If the activity of a radioactive mineral falls from 800 counts/s to 500 counts/s in 80 minutes, the half-life of the mineral is ________ minutes. (Round off to two decimal places.)

The number of alpha ($\alpha$) particles emitted to produce a daughter isotope of $^{206}\text{Pb}$ from a parent isotope of $^{238}\text{U}$ by radioactive decay is ........