The Geologic History and Bedrock Geology of Halifax, Nova Scotia George Hill GE254 6 May 2015

Study Area

Study Area

www.ns-hiking.com

Overview

 Bedrock Geology - Metasedimentary Rocks - Granitic Intrusions  Pleistocene Glaciation  Soil Morphology  Impacts of Storms on Coastline

Bedrock Geology From Keppie, 2000

Metasedimentary Rocks  Goldenville Formation - Deposited during Cambrian Period - Metamorphosed in Acadian Orogeny (Devonian) - Slate and sandstone turbidites  Halifax Formation - Deposited during Ordovician Period - Also metamorphosed in Acadian Orogeny - Shale and siltstone (more fine-grained)

Structural Geology of Metasedimentary Rock Units Form Keppie, 2000 From Keppie, 1979

Granitic Intrusions  Intruded during Acadian Orogeny, possibly later Hercynian Orogeny  Undeformed - Metamorphism, then intrusion  Diverse composition - Many different intrusions

Pleistocene Glaciation  Glaciated until ~ 12,000 years ago  Multiple ice-flow directions recorded  3 directions recorded by Finck and Graves (1987), possibly 4 th recorded

From Stea et al., 1992

Pleistocene Glaciation After Finck and Graves 1987

Soil Morphology  Atlantic Uplands Physiographic Province Form Stea et al., 1992

Impacts of Storms on Coasts: Historical Changes  High-energy environment  Decrease in beach width of 90 m from 1954-1992  Beach crest migration avg. 1.8 m/yr from 1991-2000 From Taylor et al., 2008a

Impacts of Storms on Coasts: Recent Storms  2007: Post-tropical Storm Noel - 8m in beach crest recession - 2.5m decrease in height - 1880 cubic m of sediment  2010: four powerful winter storms - Varied effect in Cow Bay - 4 to 7 times annual rate of erosion at Hartlen Point

Oval in both photos encircles the same marking stake.

Arrow in lower photo indicates washover extension that shows in Google Earth image two slides back.

Before (a) and after (b) post tropical storm Noel (from Taylor

et al.

, 2008b)

Questions?