Stratigraphy of the Lower Paleozoic Goldenville and Halifax groups in southwestern Nova Scotia

Regional mapping and petrological studies have led to revision of the Cambrian-Ordovician stratigraphy in southwestern Nova Scotia. The Goldenville and Halifax formations have been elevated to groups, and formations have been defined in each group. In the northwestern part of the area, the Goldenville Group is divided into the metasandstone-dominated Church Point formation and the overlying metasiltstone-dominated Bloomfield formation. The Church Point formation contains a metasiltstone unit (High Head member) with a distinctive trace-fossil assemblage characteristic of the Early Cambrian, consistent with detrital U-Pb zircon ages. The detrital U-Pb zircon data also suggests that the Goldenville Group below the High Head member is Early Cambrian but allows the Goldenville Group to extend into the Neoproterozoic. Units in the overlying Halifax Group are the slate-rich Acacia Brook formation and overlying metasandstone-dominated Bear River formation. In the southeastern part of the area, southeast of the Chebogue Point shear zone, the lowestmost unit in the Goldenville Group is a fine-grained metasandstone-slate package termed the Moses Lake formation. It is overlain by a thickly bedded, medium-grained metasandstone-dominated unit termed the Green Harbour formation that is similar in appearance to the Church Point formation. The upper part of the Goldenville Group consists of thinly bedded metasandstone/metasiltstone termed the Government Point formation. No equivalent unit is recognized in the northwestern area. The uppermost part consists of Mn-rich metasiltstone of the Moshers Island formation that is stratigraphically equivalent to the Bloomfield formation, although the latter lacks the characteristic Mn-rich beds. Units in the overlying Halifax Group include the black slate-rich Cunard formation and overlying grey slate-dominated Feltzen formation. The upper part of the Government Point formation farther east has yielded early Middle Cambrian trilobite fossils of Acado-Baltic affinity. The upper parts of the Bear River formation in the northwestern area and Feltzen formation in the southeastern areas locally contains the Early Ordovician graptolite Rhabdinopora flabelliformis, suggesting that the underlying Acacia Brook, Cunard, Bloomfield, and Moshers Island formations are Middle to Late Cambrian, and that a significant unconformity exists between the Halifax Group and the overlying Silurian White Rock Formation. A revised minimum thickness for the combined Goldenville and Halifax groups is 11 km.