Uppermost Ordovician rocks document an episode of widespread extinction and expansion of glaciers near the south pole that we know was related to that extinction.
Step-by-step explanation:
Based on geologic time, Ordovician period was considered as the second period of the Paleozoic Era. The Ordovician period began after the Cambrian period. Ordovician rocks generally occur at the highest elevation on Earth. It was commonly found on the top of Mount Everest.
The specific phase of the Ordovician period was regarded by the fall of sea level due to glaciation. Glaciers are moving ice which is formed due to persistence of snow in the same area for many years.