Report of Activities 2014 1

Geological Mapping at Parrsboro (Cape Sharp to McKay Head), Nova Scotia

J. H. Calder, R. D. Naylor, J. W. F. Waldron1, K. Adams2, T. Fedak2, E. George3, P. S. Giles4 and R. Stevens5

History of Project Map Units

In 1997-1998, a team of geologists led by R. D. Map units span the early Carboniferous Naylor and comprising J. H. Calder, P. S. Giles, (Mississippian) to Early Jurassic, comprising the R. Stevens and J. W. F. Waldron, and assisted by Windsor, Mabou, Cumberland and Fundy groups. C. Kennedy, T. Costain and J. Hunter, undertook Many of the map units are assigned informal status mapping of the Parrsboro coastal geology to in the Lexicon of Canadian Stratigraphy (Williams provide the Fundy Geological Museum (FGM) et al., 1985), including the West Bay, Parrsboro, with an up-to-date, detailed resource to assist in and Scots Bay ‘formations.’ The West Bay and their interpretive programing and paleontological Parrsboro formations, along with the McLaughlin curation. Paleontological investigation and Bluff conglomerate, will be formally proposed and discovery along the shore included the work of the type sections identified in an accompanying paper. Sternbergs at West Bay during the 1930s, Donald Formal and informal formations represented in the Baird at West Bay and Parrsboro Harbour in the map area are summarized in Table 1. 1950s and 1960s, and the lifelong work of Eldon George from 1950 to the present. The 1997-1998 Revisions to Existing Map field seasons saw completion of mapping from Cape Sharp in the west to Greenhill, east of Interpretations McLaughlin Bluff. Clarke Head In 2012, at the urging of then Director of the FGM, Ken Adams, mapping was extended eastward to During the 2014 field season, the Clarke Head include geologically complex Clarke Head. ‘megabreccia’ (Fig. 1) was mapped in detail Subsequently in 2013, Wasson Bluff was included (1: 5000 scale) by John Waldron and the first due to its paleontological significance and focus for author, assisted by Jeff Minichello. This represents the FGM. Mapping was pushed still farther to the the most detailed mapping yet undertaken of this east during 2014 to include The Brothers (offshore enigmatic section. Although discrete stratal blocks islands) in order to help constrain revisions to the in the order of 100 metres can be assigned with geology in the cove of Swan Creek and to provide confidence to the Windsor and Mabou groups geological continuity with outcrop of North (Bromley, 1987), these units occur within the larger Mountain Basalt eastward to Five Islands. This also fault zone as broken formations. Within this broad allowed inclusion of the type section of the McCoy fault zone, a more intensely deformed zone occurs Brook Formation. Inland exposures of wherein rounded, mylonitic, allochtonous mega- predominantly Carboniferous strata have been clasts, and mafic and less commonly felsic igneous mapped north to the Cobequid Fault, effectively the elements that are variously metamorphosed (some southern limit of mapping currently in progress by forming sea stacks), occur in a pulverized matrix of Trevor MacHattie and Chris White (this volume). sedimentary affinity (Fig. 2). These ‘exotic’

1Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3 2Fundy Geological Museum, 6 Two Island Rd., Parrsboro, NS B0M 1S0 3349 Whitehall Rd., Parrsboro, NS B0M 1S0 4Geological Survey of Canada Atlantic, P.O. Box 1006, Dartmouth, NS B2Y 4A2 5Deceased

Calder, J. H., Naylor, R. D., Waldron, J. W. F., Adams, K., Fedak, T., George, E., Giles, P. S. and Stevens, R. 2015: in Geoscience and Mines Branch, Report of Activities 2014; Nova Scotia Department of Natural Resources, Report ME 2015-001, p. 1-5. 2 Geoscience and Mines Branch

Table 1. Map units of the Parrsboro map sheet. Pennsylvanian unconformity ca. 300 Ma represents a regional tectonic event coinciding with the late McCoy Brook Formation (Fundy Group) stages of the Alleghenian orogeny (Gibbons et al., North Mountain Formation (Fundy Group) 1996; Calder, 1998). Blomidon Formation (Fundy Group) ---- unconformity ---- Swan Creek

Parrsboro formation (Cumberland Group) The relationship of North Mountain basaltic flows McLaughlin Bluff conglomerate (Cumberland Group) and underlying Mesozoic sedimentary strata north ---- unconformity ---- of Clarke Head and south of Swan Creek has been reinterpreted as a conformable contact (Figs. 3, 4). West Bay formation (Mabou Group) Earlier interpretations (Donohoe and Wallace, Windsor limestone (unassigned Windsor Group) 1982; Withjack et al., 1995; Olsen et al., 2005; Waldron et al., 2005) have depicted a reverse fault elements were sampled for petrographic, whole-rock, displacing North Mountain basalt over younger and potentially geochronological analyses. The Jurassic strata of the McCoy Brook Formation. complex history of the Clarke Head section spans Sedimentary strata east of Swan Creek incorporate initiation of ductile shearing in the late Devonian basaltic boulders of the North Mountain Formation (369 Ma based on U-Pb from granulite-grade and therefore post-date the North Mountain mylonite; Gibbons et al., 1996) to the Formation (Olsen et al., 2005), and their megabrecciation event. Our mapping indicates that assignment to the McCoy Brook Formation the megabrecciation event is constrained to (Donohoe and Wallace, 1982) is supported by our post-Mabou Group deposition and pre-Cumberland mapping. West of Swan Creek, however, the Group deposition, presumably at the Mississippian- sedimentary strata conformably underlie the North Pennsylvanian boundary. The Mississippian- Mountain Formation and are assignable to the Late

Figure 1. The Clarke Head megabreccia. Report of Activities 2014 3

Figure 2. Gabbroic clast within mylonitized gypsum, from within the Clarke Head megabreccia.

Triassic Blomidon Formation. These two map of Greenhill. The presence of the inferred Swan relations can only be accommodated by a normal Creek fault had a role in the decision to extend the fault in the vicinity of Swan Creek, which is map eastward to address the position of the basaltic supported by the pronounced topographic signature islands of The Brothers.

Figure 3. Basalt flow conformably overlying sedimentary strata reassigned to the Blomidon Formation. 4 Geoscience and Mines Branch

Figure 4. Close-up of the chilled contact of North Mountain Formation basalt overlying Blomidon Formation sedimentary strata.

A New Template for a Calder, J. H. 1998: The Carboniferous evolution of Nova Scotia; in Lyell: the Past is the Key to the Geological Map Present, eds. D. J. Blundell and A. C. Scott; Geological Society of London, Special Publication The map units represented in the map area record 143, p. 261-302. the assembly of Pangea during the Carboniferous and the initiation of its breakup in the Late Triassic- Donohoe, H. V. Jr. and Wallace, P. I. 1982: Early Jurassic. The history of life bears witness to Geological Map of the Cobequid Highlands, early tetrapod evolution and the rise of dinosaurs. Cumberland Colchester and Pictou Counties, Nova Both are exceptional opportunities for geological Scotia; Nova Scotia Department of Mines and education and research, and the map is being Energy, Map 82-7, Sheet 2, scale 1:50 000. designed with this in mind in collaboration with Tim Fedak, Director of the Fundy Geological Gibbons, W., Doig, R., Gordon, T., Murphy, B., Museum. Reynolds, P. and White, J. C. 1996: Mylonite to megabreccia: tracking fault events within a References transcurrent terrane boundary in Nova Scotia, Canada; Geology, v. 24, p. 411-414. Bromley, M. H. 1987: Geology of the mélange at Clarke Head, Cumberland County, Nova Scotia; Olsen, P., Whiteside, J. and Fedak, T. 2005: The BSc. thesis, Acadia University, Wolfville, N.S., Triassic-Jurassic faunal and floral transition in the 114 p. Fundy Basin, Nova Scotia; Geological Association Report of Activities 2014 5 of Canada Annual Meeting Field trip A7; Atlantic Lexicon of Canadian Stratigraphy, Volume VI, Geoscience Society, Special Publication no. 26, 53 p. Atlantic Region; Canadian Society of Petroleum Geologists, Calgary, 572 p. Waldron, J. W. F., White, J. C., MacInnes, E. and Roselli, C. G. 2005: Transtension and transpression Withjack, M. O., Olsen, P. E. and Schlische, R. W. along a continental transform fault: Minas Fault 1995: Tectonic evolution of the Fundy basin, Zone, Nova Scotia; Geological Association of Canada: evidence of extension and shortening Canada Annual Meeting Field trip B7; Atlantic during passive-margin development; Tectonics, Geoscience Society, Special Publication no. 33, 65 p. v. 14, p. 390-405.

Williams, G. L, Fyffe, L. R., Wardle, R. J., Colman-Sadd, S. P. and Boehner, R. C. 1985: