Preliminary Bedrock Geology of the New Germany Map Area (NTS 21A/10), Southern Nova Scotia

Report of Activities 2007 113 Preliminary Bedrock Geology of the New Germany Map Area (NTS 21A/10), Southern Nova Scotia C. E. White Introduction to produce a 1:50 000-scale bedrock map (White and Kaul, 2007) showing the distribution of units and mineral occurrences. The Nova Scotia Department of Natural Resources continued bedrock mapping through the summer of 2007 in the New Germany map area (NTS Stratigraphy 21A/10). This work completes the northernmost part of the area covered by the South Shore Introduction Bedrock Mapping Project (Fig. 1). The project has provided a greater understanding of the The earliest regional geological mapping at a stratigraphy, structure, metamorphism and mineral reasonable scale (1 inch to 1 mile) in the current deposits of southwestern Nova Scotia. map area was done by Faribault et al. (1939a, b). As with previous map sheets in the project area They subdivided the stratified rocks into an older (e.g. White, 2005, 2006, 2007), geological data grey or blue-grey quartzite (Goldenville Formation) were collected at a scale of 1:10 000 and complied and a younger grey, green, and black slate (Halifax Figure 1. Simplified geological map of the Meguma Terrane, Nova Scotia, showing location of the New Germany map area in relation to the Southwest Nova and South Shore mapping projects (red box). White, C. E. 2008: in Mineral Resources Branch, Report of Activities 2007; Nova Scotia Department of Natural Resources, Report ME 2008-1, p. 113-124. 114 Mineral Resources Branch Formation), and placed both formations in the Meguma or “Gold-bearing” Series, which they considered to be Precambrian. They placed the boundary between the Goldenville and Halifax formations at the highest exposed bed of quartzite in the Goldenville. Faribault et al. (1939a, b) also noted that the base of their defined Halifax Formation consists of a package of green-grey slate and argillite that passes upwards into purple, green- grey, and black slate. They considered the granitoid rocks that intruded these units to be Devonian. Taylor (1967), during his 1960 to 1961 regional mapping, compiled the earlier work of Faribault et al. (1939a, b) on his maps but considered the Goldenville and Halifax formations to be Ordovician and older. Like Faribault et al. (1939a, b), he placed the contact between the two formations at the top of the highest ‘arenaceous’ bed in the Goldenville Formation but suggested that the contact, in places, is gradational with a ‘transition zone’ up to ½ mile wide. He also considered the granitoid plutons to be Devonian to Carboniferous. The granitic rocks in the map area were studied by Horne (1992) as part of the South Mountain Batholith mapping project and although the contact between the granite and metasedimentary units was slightly modified, the geology in the adjacent Meguma Group was primarily after Faribault et al. (1939a, b). The traditional two-fold division of the Meguma Group into the Goldenville and Halifax formations is currently undergoing major revisions by the Nova Scotia Department of Natural Resources (e.g. White, 2007, 2008; White et al., 2007a, b). These revisions are largely the result of mapping related to the South Shore Bedrock Mapping Project and the earlier Southwest Nova Mapping Project, which have led to the definition of regionally mappable ‘formations’ within the traditional Goldenville and Halifax formations. As a result, the Goldenville and Halifax formations have been elevated to ‘group’ status and the former Meguma Group is now Meguma Supergroup (Schenk, 1995, 1997; Horne and Pelley, 2007; White et al., 2007a, b; White 2008). White (2005, 2006, 2007) established formations in the Liverpool, Lake Rossignol and Kejimkujik map areas to the southwest of the present map area. Work done in 2007 shows that those formations continue into the present map area Report of Activities 2007 115 Figure 2. Simplified geological map of the New Germany map area (NTS 21A/10). See legend on facing page. and include the Green Harbour, Government Point, locally preserve cross-bedding, ripple marks, and and Moshers Island formations of the late graded bedding. The metasandstone locally Neoproterozoic to Cambrian Goldenville Group, contains abundant elliptical calc-silicate lenses. and the overlying Late Cambrian to Early Close to the contacts with the South Mountain Ordovician Cunard and Feltzen formations of the Batholith, the metasiltstone beds have been Halifax Group. thermally metamorphosed to hornfels and contain cordierite ± andalusite. The contact with the Goldenville Group overlying Government Point Formation is not exposed but is considered gradational as it is in the Green Harbour Formation map areas to the southwest (e.g. White, 2005, 2006, 2007). As in the map areas to the southwest (White, 2005, 2006, 2007), the distribution of the Green Harbour Government Point Formation Formation (formerly member) is controlled by the plunge of numerous northeast-trending regional The Government Point Formation (formerly folds (Fig. 2). The formation consists of grey thick- member) is typified by green-grey to purple bedded (1-4 m thick) metasandstone interbedded metasiltstone rhythmically interbedded with light with minor, thin (<20 cm thick) green, cleaved grey metasandstone (Fig. 3b). Beds range from metasiltstone. The metasandstone typically lacks 10 cm to 1 m in thickness. The metasandstone sedimentary structures, although in places it is locally displays spectacular cross-bedding, whereas thinly bedded (Fig. 3a). Metasiltstone interbeds metasiltstone interbeds are generally parallel 116 Mineral Resources Branch laminated. At one location north of Farmington, a that the contact between the Goldenville and thin (10 cm thick) metalimestone bed was Halifax groups in southwestern Nova Scotia be observed, but unlike the calc-silicate nodules in a placed at the base of the Cunard Formation, where similar stratigraphic position to the southwest abundant black sulphide-rich slate enters the (White, 2007) it did not yield any shelly fossils. stratigraphy. This interpretation is supported This formation is similar to the lower green and further by whole-rock geochemistry of the purple slates described by Faribault et al. (1939a, Meguma Supergroup in the Pubnico-Chester area, b) at the base of their defined Halifax Formation. which indicates a gradual increase in MnO content As metamorphic grade increases toward the South up section from the Green Harbour to Government Mountain Batholith, the metasiltstone is spotted Point formations, culminating with MnO contents with cordierite ± andalusite. This unit is best up to 25 wt.% in the manganese-rich Moshers exposed along logging roads in the area west of Island Formation, followed by a dramatic decrease Parkdale (Fig. 2). to 0 wt.% MnO in the overlying Cunard Formation (Toole, 2006; White et al., 2008; unpublished data, Moshers Island Formation Nova Scotia Department of Natural Resources). The presence of MnO in the Green Harbour, As in the Liverpool, Lake Rossignol and Government Point and Moshers Island formations Kejimkujik map areas to the south (White, 2005, suggests a genetic relationship among these units 2006, 2007), the Moshers Island Formation in the which is distinct from the overlying MnO-depleted present map area (Fig. 2) is a narrow (<100-500 m Cunard Formation. Such a distinctive geochemical wide) unit of green to green-grey to grey, well signature can be used to define stratigraphic units laminated metasiltstone to slate, interlayered with 1 (North American Commission on Stratigraphic to 5 cm-thick metasandstone beds. A characteristic Nonenclature Code, 2005). feature in this unit is thin (2 to 20 mm wide), ptygmatically folded, pink coticule beds and lenses. Halifax Group The pink colour is due to the presence of spessartine garnet. Where metamorphic grade is Cunard and Feltzen Formations lower, coticules are not present and these beds and lenses are typically weathered out and the resulting The Cunard Formation occupies the core of a major cavities and proximal fractures are stained with northeast-trending regional syncline (Fig. 2) and steel-blue manganese (Figs. 3c, d). The contact consists of black to rust-brown slate (Fig. 4a) with with the overlying Cunard Formation is well thin beds and lenses of minor black metasiltstone exposed in a slate pit southwest of Parkdale and interbedded with cross-bedded, fine-grained, appears to be gradational over a few metres. pyritiferous metasandstone beds. Metasandstone As previously argued by White (2005, 2006, beds, up to 30 cm thick, are common in the middle 2007) and White et al. (2007a, b, 2008), the and upper parts of the Cunard Formation but are Government Point and Moshers Island formations generally lacking in the basal section. The slate are more closely linked with the Goldenville Group locally contains abundant pyrite, arsenopyrite and than with the Halifax Group. Previous workers pyrrhotite that form beds and nodules up to 5 cm (e.g. Faribault et al., 1939a, b; Taylor, 1967) place thick. A curious feature noted in the slate is that the boundary at the top of the last metasandstone some of the pyrite is hosted in 5 mm wide oolite- bed. This definition was considered arbitrary by rich carbonate beds. Stratigraphically above the White et al. (2007a, b) as no thickness was Cunard Formation, in the keel of the major assigned to this last metasandstone bed. In addition, northeast-trending syncline, is a poorly exposed the Government Point and Moshers Island grey-green well laminated metasiltstone (Fig. 2). formations have been shown to contain abundant Because of its stratigraphic position, it is assigned metasandstone beds (albeit thin) and lack abundant tentatively to the Feltzen Formation, although it black sulphide-rich slate, a characteristic of the differs from the grey slate and metasandstone overlying Halifax Group as defined by White exposed in the type section near Mahone Bay (2005, 2006, 2007). White (2006, 2007) proposed (O’Brien, 1988). Close to the contacts with the Report of Activities 2007 117 Figure 3.

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