The St. Pierre Group formed 581 million years ago with felsic and pyroclastic flows.
Together with mafic rocks and andesite, they are evidence of back arc environment.
[1] In the Mesozoic, the Orpheus Graben opened, widening into the St. Pierre Block and filled with thick sediments in the Jurassic, Cretaceous and Paleogene.
Estimates in 1992 suggested 250 billion cubic meters of natural gas and up to 700 million barrels of oil.
[2] Analysis of glacial till suggests that the islands were covered by ice sheets from Newfoundland in the Pleistocene with the islands displaying marine edge deposits.