It's impossible to say definitively which is older, sandstone or shale, because both can form from a wide range of ages.

Here's why:

* Formation: Both sandstone and shale are sedimentary rocks, meaning they form from sediment deposited over time.

* Sediment Source: The sediments that form sandstone (sand) and shale (clay) come from different sources and are formed through different weathering processes.

* Time: The age of a rock depends on when the sediments were deposited and lithified (turned into solid rock). This can range from very recent to billions of years old.

Example: You could find a very old shale formed from ancient mud deposits, and a much younger sandstone formed from sand eroded from a recent mountain range.

Therefore, the age of a rock is determined by its specific geological history, not simply its type.