Download GEOS 254 Sedimentary Rocks

Types of Sediment
• Sediments are lithified into sedimentary rocks.
• There are seven types of sediment:
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Epiclastic or terrigenous (normal)
Pyroclastic
Orthochemical
Allochemical
Residual or pedogenic
Cosmogenic
Polygenetic.
Characteristics of the Components of
Sedimentary Rocks
• Clastic components
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Mineralogy or for lithic clasts, petrography
Grain/clast size
Grain/clast morphology (sphericity, roundness)
Grain/clast sorting
• Orthochemical components.
– Mineralogy, crystal size, crystal shape & fabric
Mineral Chemical Stability Series
• Most Stable: quartz, zircon, tourmaline
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micro-quartz (chert & chalcedony)
Muscovite
K-feldspar
albite____________________________________
plagioclase feldspars
hornblende, biotite
pyroxene
olivine
Least Stable: From albite and above minerals form
in the sedimentary environment (authigenic).
Relative Abundance of Minerals
• Terrigenous Minerals
• Quartz 30-50%, Clay minerals 25-35,
Metamorphic rock fragments 5-15%, Feldspar 515%, Chert 1-4%, Micas 0.1-0.4%, Carbonates
0.2-0.4%, Heavy Minerals 0.1- 1.0
• Chemical Minerals
• Carbonates 70-85%, Silica 10-15%, Sulphates
and salts 2-7%, Miscellaneous 2-7%.
CARBONATE ROCKS
• Deposited Loose (may not be totally clear)
>90% lime mud: mudstone (deposited loose)
<90% lime mud: wackestone (deposited loose)
grain supported with muddy matrix: packstone
grain supported well sorted: grainstone
Deposited bound together during deposition
boundstone (e.g. stromatolite)
No depositional texture preserved.
crystalline carbonate.
CARBONATE STAINING
• Rocks and slides are stained using dilute
acid and two dyes.
• Calcite is red if Fe-free, purple if Fe-rich
• Pure dolomite does not stain, Fe-dolomite
stains blue.