Rippled Rock at Point Pleasant Park

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Point Pleasant Park occupies the southern extremity of the promontory on which the city of Halifax is built in Nova Scotia. It juts out into the harbour and was a militarily strategic position in the past, as evidenced by old structural remains and modern memorials (MacBourne et al. 1986). The bedrock underlying the park is Late Cambrian to Ordovician Period slate and minor metasiltstone which formed on the Meguma terrane lying on the continental margin of the much  larger Gondwana between 499 and 470 million years ago.

A rocky outcrop of siltstone on Black Rock Beach, seen shortly after you enter the park from the east entrance, is remarkable for the ripple marks on its sloping surface. These were formed by a turbidity current and subsequently preserved under a layer of mud. Sediments were derived from the erosion of Gondwana and transported by large rivers across the land mass before being deposited. The rocks here are called turbidites and are part of a succession of similar layers 4 kilometres deep (Hickman Hild and Barr, 2015). The rocks are the part of the Halifax Group which used to be called the Halifax Formation, which has recently been re-classified into three – the Bluestone Formation, Cunard Formation, and Beaverbank Formation (White et al. 2008). The Black Rock Beach strata belong to the Bluestone Formation.

REFERENCES

Donohoe, H. V. Jnr, White, C. E., Raeside, R. P. and Fisher, B. E, (2005) Geological Highway Map of Nova Scotia, Third Edition. Atlantic Geoscience Society Special Publication #1.

Fraser, J. A. (2010) Trends and Architecture of the Bluestone Formation Turbidites in Point Pleasant park, halifax, Nova Scotia. Submitted in Partial Fulfillment of the Requirements for the degree of bachelor of Science, Honours, Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia.

Hickman Hild, M. and Barr, S. M. (2015) Geology of Nova Scotia, A Field Guide, Touring through time at 48 scenic sites, Boulder Publications, Portugal Coce-St. Philip’s, Newfoundland and Labrador. ISBN 978-1-927099-43-8, pp 128 – 131.

MacBourne, B., Donohoe, H. and Devanney M. (1986) A Walking Tour of Rocks, Minerals and Landforms of Point Pleasant Park, Nova Scotia Department of Mines and Energy, Information Circular 7.

White, C. E., Bell, J. A., McLeish, D. F., MacDonald, M. A., Goodwin, T. A. and MacNeil, J. D. (2008) Geology of the Halifax Regional Municipality, Central Nova Scotia. In Mineral resources Branch, Report of Activities 2007, Nova Scotia Department of Natural resources, Report ME 2008-1, p. 125-139.

 

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