Final answer:
The oldest layer is typically at the bottom, the youngest at the top. Unfossilized bones in recent layers can be dated with radiocarbon, while fossilized bones between volcanic layers can use argon-based methods. Biostratigraphy can also help correlate layers by fossils.
Step-by-step explanation:
In the context of stratigraphic dating, the oldest layer is typically found at the bottom due to the process of sedimentation over time. The youngest layer would be at the top as it is the most recent to have been deposited. To date an unfossilized bone in layer B, one could use chronometric dating methods like radiocarbon dating (C-14) if the bone is less than 50,000 years old. For older materials, other methods such as Uranium-series or luminescence dating might be more appropriate.
For a fossilized bone in layer D, with adjacent layers C and E composed of volcanic rock, one could use methods such as argon-argon (Ar-Ar) or potassium-argon (K-Ar) dating, taking advantage of the volcanic material to provide a bracketed age for the sediment containing the bone. These methods are suitable for dating materials that are several thousand to billions of years old. The exact method chosen would depend on the estimated geological age of the rock layers.
In addition to these methods, biostratigraphy can be used to correlate and date layers based on the fossils they contain, identifying and using indicator artifacts present within the layers to establish their relative ages.