Sedimentary & Metamorphic
Rocks
Objectives
• Discuss the major types of sedimentary rocks,
how they form, and what they tell us about
past environments
• Explain the formation of metamorphic rocks
• Introduce the concept of the rock cycle
Sedimentary Rocks
• Results from the
deposition,
compaction, and
cementation of
rock fragments
• Lithification
– The process
where
sediments are
formed into
rocks
Sedimentary Rocks
• Clastic
– Made from particles
of other rocks
– e.g. conglomerate
• Non-clastic
– Formed from
chemical solution of
from organic
deposition
Salt pan at Badwater, Death Valley, CA.
© National Park Service
Sedimentary Rocks
• Clastic Rocks
– Conglomerate
• Poorly-sorted clastic
rock
• Made up of gravels,
pebbles, and sand
– Sandstone
• Sand-sized sediments
– Shale
• Fine-grained mud
Insert Fig. 29.5 shale
Sedimentary Rocks
• Non-clastic rocks
– Limestone (CaCO3)
• Accumulation of marine
shell fragments
– Evaporites
• Halite (salt)
• Gypsum
• Anhydrite
Mauv Limestone at Grand Canyon’s South Kaibab trail.
© USGS
Records of Past Environments
• Cross-bedding
– Horizontal beds composed of inclined layers
– Indicate directional flow
Cross-bedding found in the Glen Canyon Formation
at Dinosaur National Park. ©National Park Service.
Records of Past Environments
• Stratigraphy
– The study of rock
layers
• Stratification
– Formation of
sedimentary rocks
layers
• Strata
– A layer of of
sedimentary rock or
soil
Records of Past Environments
• Unconformity
– Gap in the rock record
– Contact between two
beds of different rock
types or of different
ages
Metamorphic Rocks
• Changed rock
• Altered rock by varying
degrees of heat and
pressure
• If changed by heat, the
process is contact
metamorphism
Metamorphic Rock Types
• Parent rock can be sedimentary, igneous or
metamorphic rocks
Parent Rock (rock type)
Metamorphic Rock
Metamorphic Features
Sandstone (sedimentary rock)
Quartzite
Quartz with silica cement
Limestone (sedimentary rock)
Marble
Fizzes with dilute HCl acid
Shale (sedimentary rock)
Slate
Sheet-like
Slate (metamorphic rock)
Schist
Displays flat shiny surfaces
Granite (igneous rock)
Gneiss
Alternating dark and light layers
The Rock Cycle
• The transformation of one rock type into another Igneous rocks are
weathered into sedimentary rocks
– Sedimentary, igneous or metamorphic rocks can be changed to metamorphic
rocks
– Metamorphic rocks melt to form igneous rocks