Bluestone Formation Rock Textures at Point Pleasant Park 1

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On the southwest shore of Point Pleasant Park in Halifax, Nova Scotia, Bluestone Formation bedrock with an early Ordovician age outcrops on the beach. It comprises thinly bedded metasiltstone and slate with occasional calcareous concretions. The rock originated as deep sea muds and fine-grained sands which were compacted and lithified into shale 450 million years ago (MacBourne et al., 1986). The rock was later metamorphosed into slate by heat and pressure that built up during massive movements of the earth’s crust. It was further “baked” by the heat generated by an intrusion of molten magma (a batholith of granite was created) at which time new crystals of anadalusite and cordierite were formed in the Bluestone Formation strata. The closer the Bluestone slates and metasediments had been positioned relative to the injection of granite, the greater the heat, and the greater the number of the crystals formed. The small crystals are now weathering out from the surface of the rock by the action of the elements. This is leaving many characteristic small pits and embuing the exposed rock s with a strange texture.

Some of the layers in the rock cross-sections in the illustrated outcrops near Chain Rock Beach (above) show undulating bedding planes and cross-stratification. I think that these are the equivalent of the stone sand ripples on the surface of exposed bedding planes in similar rock on Black Rock Beach at the other side of the park (see the previous post – Rippled Rock at Point Pleasant Park).

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.

2 Replies to “Bluestone Formation Rock Textures at Point Pleasant Park 1”

  1. Hi Jessica thanks for stopping by today – I have one of your photos in mind to help with a painting I’m struggling with – will have a good look through all your new posts soon. Love all the geology terms here – ordovician, batholith, anadalusite! (delicious words you can’t use every day.)

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