Laurentia (Laurentian Shield) The Precambrian shield (see CRATON) of central eastern Canada. The name is derived from the St Lawrence River and has been applied to a series of granites, gneisses and metasediments that are older than 2500 Ma. The Laurentian Shield forms the ancient ‘core’ of Canada, around which younger orogenic belts have been accreted.

Laurentia(Laurentian Shield) The Precambrian shield of central eastern Canada which forms the ancient ‘core’ of Canada, around which younger mountain belts have been accreted. The name, derived from the St Lawrence River, has been applied to a series of granites, gneisses, and metasediments that are older than 2500 Ma.