The Goldthwait Sea was a sea that emerged during the last deglaciation, starting around 13,000 years ago, covering what is now the Gulf of Saint Lawrence and surrounding areas.At that time, the land had been depressed under the weight of the Laurentide Ice Sheet, which was up to 2 kilometres (1.2 mi) thick.Areas on the Anticosti Island and low-lying regions of Quebec and the Maritimes bordering the Saint Lawrence were below sea level.As the land rebounded over the next 3,000 years, despite rising sea levels the sea retreated to roughly the present boundaries of the Gulf.