Younger oceanic crust will have ocean sediments, while older oceanic crust will have oceanic sediments.

Younger oceanic crust will have thinner oceanic sediments because it would have not had enough time to form. As a result they are not so thick and deep yet. On the other hand, older oceanic crust will have thicker oceanic sediments or more sediment covering it. So thickness of oceanic sediments work as a geological clock. 

The beach , myrtle beach sc

Answer metamorphic rock;