The style of harpoon head (carved from antler or ivory) was used through the Early, Middle and Late Dorset (700 BCE to 1000 CE). Its use included the hunting of walrus as well as small and medium marine mammals.

Sources:

Harpoon heads, 600 BC–AD 1300, Canada[1]

The modus operandi of walrus exploitation during the Palaeoeskimo period at the Tayara site, Arctic Canada[2]

Ancient Harpoon Heads of Nunavut [3]

The Dorset-Thule Succession in Arctic North America: Assessing Claims for Culture Contact[4]