NOTES: Sedimentary ROCKS
AIM: What are the characteristics of sedimentary
rocks?
1. Sedimentary rocks are formed from the
accumulation and lithification of sediments.
2. There are 3 types of sedimentary rocks:
 Clastic sedimentary rocks are formed
from clay, sand, and gravel (fragments)
 Crystalline sedimentary rocks are formed
from mineral grains and crystals that
precipitate out of solution by evaporation
or chemical action
 Bioclastic or Organic rocks are formed
from the remains of plants and animals
3. Clastic Rocks – the particles consist of
weathered existing rocks.
Particle sizes vary
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 Large accumulations of clastic sediments
exist where rivers meet still bodies of water
 Clastic rocks are lithified by compaction
and cementation
Compaction occurs when the weight of overlying
sediments compresses the material and squishes
out most of the water
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Cementation occurs when dissolved minerals
precipitate in the pores between the particles and
glue them together. Ex: silica, calcite, hematite
4. Crystalline Rocks – the minerals dissolved
in solution are precipitated from water by
evaporation or chemical action.
5. Bioclastic or Organic rocks are formed
from accumulations of remains of living
things. YES, rocks made of dead stuff.
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6. Secondary Sedimentary Features: see
these in a rock and it’s probably
sedimentary.
a) Stratification – the arrangement of
sedimentary rock in visible layers
that may separate easily
b) Fossils – the remains, impressions,
or any other evidence of the
existence of life preserved in the
rock
Ex:
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c) Ripple Marks – seen on the surface
of a bed of sandstone formed from
wave action on the sand sediment
before lithification
d) Mud Cracks – these develop when
deposits of wet clay dry out and
crack. Cracks often fill with
different material
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