The oldest period among the options provided is the Ordovician Period. The geological time scale places the Ordovician Period after the Cambrian Period and before the Silurian Period, making it older than both the Silurian and the subsequent Carboniferous and Quaternary periods.
To summarize:
- Ordovician Period: Older
- Silurian Period: After Ordovician
- Carboniferous Period: After Silurian
- Quaternary Period: Most recent
So, the correct answer is the Ordovician Period.