Sedimentary Rocks
• Recycled from older rocks
• Clastic texture
• Weathering produces sediment and solutions
• Sediment is - eroded, transported, deposited, and buried
• Texture and components reflect mode of transport, environments, climate,
sea level, and changes in life through time
Sedimentary Rocks
• Sediments are deposited within broad regional low spots (basins), and
sedimentary rocks form there over time.
• The texture and composition of these sediments reflect how they got
to the basin, and the particular environments in which they were deposited…
Sedimentary Rocks - texture
• Texture
• Size,shape, and arrangement of grains
• How the sediment got there
• Energy/water depth
– Conglomerate, sandstone, shale
Sedimentary Rocks - components
• Where did the sediment come from?
• Source - Parent rock => mineral composition
• Example - sandstone with feldspar and quartz
– Source = granite in mountains
Sedimentary Rocks - components
• Fossils - remains of past life
• = part of the rocks
• Environment
– In which the creature lived
• Marine versus continental
• Specific environments
– Forests, lakes, reefs, beach, etc.
• Climate conditions
– Tropical, temperate, arid, etc.
Sedimentary Rocks - structures
• Ripples
• Ancient dunes
• Mud cracks
• Trackways
• Climate and environment
Sedimentary Rocks - environments
• Climate from rock type
• Limestone = tropical-marine
• Coal = tropical-continental
• Salts = arid
Sedimentary Rocks - stratification
• Sedimentary Rocks = layered/stratified
• Older layers towards bottom
• superposition
Question
• Discuss the following with the person next to you:
• If you interpreted the environments for all the individual layers of
sedimentary rock in the GC, what sorts of information could you interpret if
study them all together?
Metamorphic Rocks
• Rocks are transformed because of heat and pressure
• Metamorphic texture = layering and folding
• Do not melt - what would they become if they did?
Metamorphic Rocks
• Metamorphism - convergent boundaries
• Examples
– Slate, schist, and gneiss
• Indicate ancient episodes of mountain building