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Lecture 5

Environmental Science
Course Code
Nick Eyles

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6th Feb 2009
Sedimentary basins: accumulation of sedimentary rock
1. Occur in different tectonic settings
2. Have distinct sedimentary rock fills
- If basin close to volcanoes, it will be fills with volcanically-influenced basin
- Foreland basins (in the foreland of mountain ranges)
o E.g. Alberta
o Thick continental crust
o Erosion off mountains accumulate
o A lot of organic material e.g. coal, oil, gas
- Forearc basin
o Dominated by sediments that have been deposited by gravity
o Frequent occurrence of large earthquakes causes landslides (sediment gravity flows)
- Extensional (rift) settings
o Divergence
o Plume pushes continental crust apart
o Evaporates (salt deposits) accumulate when rifts dries out (e.g. dead sea)
o Also igneous rocks (e.g. basalt)
- Basin analysis
o Used for finding resources
o Used as a investigating tool in constructing what the surface of the earth looked like in
the past
Oil and gas on continental margins
1. Continent undergoes extension. The crust is thinned and a rift valley forms
2. Continent tears in two. Continent edges are faulted and uplifted. Basalt eruptions form oceanic
3. }v]vvo]uvovlZµ]]vP^]À_uP]v}(}u}v]vvoZoÀXdZ
ocean widens and a MOR develops, e.g. Atlantic Ocean
- Oil accumulates near the coast e.g. Hibernia, Sable Island
Metamorphic rock (change of appearance)
- Form from pre-existing rocks, altered by heat pressure
- Can be formed from sedimentary, igneous, or even metamorphic rocks themselves
- Close to melting
- Common metamorphic rocks:
o Low - Slate, phyllite, schist, gneiss - high
- Various degrees of metamorphism is referred to as grade
- The hotter, the higher the grade
- After gneiss is magma if it gets any hotter
- Most metamorphic rocks are foliated (banded, sheeted)
o Minerals lined in sheets
- What causes foliation?
o Preferential growth of minerals after the influence of pressure
1. Conglomerate t rounded
2. Stretched pebble conglomerate - squeezed
3. Foliation
o Protolith t parent rock that got metamorphosed
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