1. SEDIMENTARY ROCKS
A Brief Review

2. THERE ARE 4 BASIC COMPONENTS OF SEDIMENTARY ROCKS
sediments & sed. rocks are usually described according to 4 basic components:
a. grains (larger particles)
b. matrix (fines)
c. pores (air, H2O, oil, gas)
d. cement (usually post-depositional)
grains
pores
cement
matrix

3. CLASSIFICATION OF SEDIMENTARY ROCKS
Classified as either:
Detrital = composed of broken fragments & weathering products of other rocks &/or minerals
Shales
Sandstones
conglomerates
Chemical = composed of minerals precipitated from water solutions
Inorganic (direct ppt)
evaporites like rock salt which is halite
some cherts, such as at Ross Creek
Organic (indirect ppt)
fossiliferous limestones (organisms secrete CaCO3, not seawater)
some cherts (with silica skeletons of micro-organisms, diatoms)

4. DETRITAL SEDIMENT GRAIN SIZES
Grain-size is the primary basis of distinguishing different kinds of detrital sedimentary rocks:

5. CLASSIFICATION OF DETRITAL SEDIMENTARY ROCKS

6. CONGLOMERATE
Cemented sedimentary rock whose grain-size diameters are greater than 2 mm
Four categories:
2-4 mm = granule conglomerate
4-64 mm = pebble "
mm = cobble "
>256 mm = boulder "
Cements vary. Common ones are:
calcite (calcium carbonate)
quartz (silicon dioxide)
hematite (iron oxide)

7. CONGLOMERATE
Conglomerates are common in continental stream channel deposits

8. BRECCIA
A conglomerate whose grains are angular

9. SANDSTONE Grain size = 1/16th mm to 2 mm
Cements vary, commonly: calcite quartz
or iron oxides
Quartz sandstone = quartz grains predominate
Arkose
rich in feldspar grains
pink or red colour from feldspars
Graywacke
>15% clay matrix
gray to black colour
lots of feldspar & rock fragments

10. SILTSTONE Grain size: Quartz dominates Structures:
less than fine sand (<1/16th mm)
larger than clay sizes (<1/256th mm)
feels "gritty between your teeth :(
Quartz dominates
Structures:
finely laminated
rippled
cross-bedded

11. SHALE Subparallel parting splits into thin layers
Clay and silt sizes dominate
Clay minerals dominate
Colours vary:
Grey (contains organic matter)
Black:
may be rich in organic matter
some associated with coals
Red (contains iron oxides)
Preserves fossils well

12. CLASSIFICATION OF CHEMICAL SEDIMENTARY ROCKS