Age and correlation of the Honorat Group, southern Gaspé Peninsula

Abstract

The Honorat Group of southern Gaspé consists of two formations: the Arsenault and the Garin. The Arsenault Formation, heretofore considered barren, has yielded a graptolite faunule indicative of a Llanvirn–Llandeilo age (early Middle Ordovician), suggesting a correlation with the lower Mictaw Group of Gaspé as revised by de Broucker. A hiatus of indeterminate magnitude, corresponding to the Taconic unconformity, probably separates the Arsenault Formation from the overlying Garin Formation. The Garin has yielded graptolites ranging from the upper Climacograptus spiniferus Zone to the Paraclimatograptus manitoulinensis Zone (late Middle to early Late Ordovician). The C. spiniferus Zone graptolites are identical to those of the upper γ sequence of the Cloridorme Formation of northern Gaspé and the Blind Brook Formation of the Munsungun Anticlinorium of Maine but differ somewhat from those from the upper Tetagouche Group of New Brunswick, which are closer to those from the Summerford and Exploits groups of north-central Newfoundland. The C. spiniferus zone has a wide distribution in eastern North America. It correlates with the Orthograptus amplexicaulis Zone of the southwestern United States and with the Climacograptus baragwathi Zone (Ea2) of the Pacific faunal province.The Matapédia Group, stratigraphically above the Honorat Group, has yielded both shelly fossils and a few graptolites. The ages of the graptolites now date it as Late Ordovician to late Early Silurian (Dicellograptus complanatus Zone – Monograptus sedgwickii Zone).