Sedimentary Rocks
Made from Sediments!!
AIM: What are the characteristics
of sedimentary rocks?
• Sedimentary rocks are formed from the
accumulation and lithification of
sediments
Sed Rocks
• 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
Clastic Rocks
• Clastic Rocks – the particles consist of
weathered existing rocks.
• Particle sizes vary
Clastic Sed Rocks
• Large accumulations of clastic sediments
exist where rivers meet still bodies of
water
Clastic Sed Rocks
• 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
Cementation occurs when dissolved minerals
precipitate in the pores between the particles
and glue them together. Ex: silica, calcite,
hematite
Crystalline Sed Rocks
• Crystalline Rocks – the minerals
dissolved in solution are precipitated
from water by evaporation or
chemical action.
Bioclastic Sed Rocks
• Bioclastic or Organic rocks are formed
from accumulations of remains of living
things. YES, rocks made of dead stuff
Sed Rocks – Secondary Features
• Secondary Sedimentary Features:
see these in a rock and it’s probably
sedimentary.
• Stratification – the arrangement of
sedimentary rock in visible layers that
may separate easily
Sed Rocks Secondary Features
• Fossils – the remains, impressions, or
any other evidence of the existence of
life preserved in the rock
Sed Rocks Secondary Structures
• Ripple Marks – seen on the surface of
a bed of sandstone formed from wave
action on the sand sediment before
lithification
Sed Rocks Secondary Structures
• Mud Cracks – these develop when
deposits of wet clay dry out and crack.
Cracks often fill with different material