Stratigraphy of the Aroostook–Percé Anticlinorium in the Gaspé Peninsula, Quebec

Abstract

In Quebec, the Aroostook–Percé Anticlinorium exposes two stratigraphic groups: the Honorat and the Matapédia. The terrigenous units of the Honorat Group form the core of the anticlinorium and are overlain by the carbonate sequence of the Matapédia Group. Each group comprises two formations. The Honorat is herein divided into two new formations, the Arsenault and the Garin, which are defined for the first time. The Matapédia Group includes the Pabos and White Head formations. The Pabos Formation, a transitional unit between the noncalcareous strata of the Honorat Group and the carbonate facies of the White Head Formation, is here redefined. The White Head Formation comprises four members. These two groups represent continuous sedimentation from the Late Ordovician (Caradocian) to the Early Silurian (Llandoverian).The lithostratigraphy of the type areas of the Honorat Group (Honorat Township region) and Pabos Formation (Chandler region) are fully described, whereas the lithostratigraphy of the type area of the White Head Formation (Percé area) is summarized only. The Arsenault, Garin, and Pabos formations and the Burmingham, Côte de la Surprise, L'Irlande, and Des Jean members of the White Head Formation constitute the stratigraphic sequence in the eastern part of the Aroostook–Percé Anticlinorium. These units are extended to the western part of the anticlinorium in Quebec and in New Brunswick, and also to other Late Ordovician – Early Silurian rocks in the Chaleur Bay and Gaspé – Connecticut Valley synclinoria.Rocks of the Aroostook–Percé Anticlinorium are interpreted as having been deposited by turbidity currents in a relatively deep water basin. Deposition evolved through time from terrigenous to limestone, reflecting a change in source areas.The Grand Pabos fault divides the Aroostook–Percé Anticlinorium between Percé and Carleton into two areas with stratigraphically different sequences. The northern area is dominated by carbonate rocks of the Matapédia Group, whereas the southern area is composed mainly of terrigenous facies of the Honorat Group. Carbonate sedimentation of the White Head Formation started during Late Ordovician time in the northern area but only during Early Silurian times in the southern area. The thickness of the carbonate strata, which reaches 2000 m in the northern area, diminishes to 150 m in the southern area.