Sedimentary Formations

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Sedimentary Formations

• Interpretation of Sedimentary Rocks
• Source Area
• Environment of Deposition
• Plate Tectonics and Sedimentary Rocks  

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Mud Cracks
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Preserved mud cracks
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Ripple Marks Model
Symmetric
Asymmetric
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Tidal Flat Ripples
Current Direction
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Preserved Ripple Marks
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Preserved Bivalve Fossils
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Vertebrate (Fish) Fossil
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Dinosaur Footprint
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Sedimentary Sequences on Mars
NASA-MOC image Candor Chasma - Each layer is 10
m thick
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Formation Definitions

• Body of rock of considerable thickness
• Characteristics must be distinguishable from
  adjacent units
• Usually composed of one or more beds
• Often based on rock type (lithology or
  lithofacies)
• Contacts are the boundary surfaces between two
  rock units of different lithology or age

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Upper Grand Canyon Sequence
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Marine Transgression and Regression
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Distance from Source
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Lithofacies - Paleocurrent Maps
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Environments of Deposition

• Glacial Environments
• Alluvial Fan
• River Channel and Floodplain
• Lakes
• Marine Deltas
• Beach, Barrier Islands, Dunes
• Lagoon
• Shallow Marine Shelves
• Reefs
• Deep Marine Environments

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Sedimentary Environments
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Alluvial Fan Deposits - Baja, CA
Coarse channel deposit (conglomerate)
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Fluvial Environments
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Convergent Margin Environment
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Rift Sedimentary Environment
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Chapter 7Metamorphism, Metamorphic Rocks, and
Hydrothermal Rocks
.
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The Rock Cycle
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Factors Controlling the Characteristics of
Metamorphic Rocks

• Composition of the Parent Rock
• Temperature
• Pressure
• Fluids
• Time

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Classification of Metamorphic Rocks

• Major Types of Metamorphism
• Contact Metamorphism
• Regional Metamorphism
• Prograde Increasing T P
• Retrograde Decreasing T P
• Shock Metamorphism

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Plate Tectonics and Metamorphism

• Hydrothermal Processes
• Hydrothermal Activity at Divergent Plate
  Boundaries 
• Metasomatism
• Hydrothermal Rocks and Minerals 
• Sources of Water

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Folded - Micas photomicrograph
2 cm
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3.7 ByBP Amitsoq Gneiss
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The Effect of Pressure
Pressure increases with depth Volume
decreases with depth
Hydrostatic Stress s1 s2 s3
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Normal vs. Shear Stress
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Flattened Pebbles
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Normal vs. Shear Stress Fabric Development
Original Fabric
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Fabric Terminology

• Metamorphic fabrics develop as a result of
  differential (deviatoric) stress, i.e. stress is
  NOT equal in all directions.
• Foliation - Development of a planar texture or
  fabric within the rock.
• Lineation - Development of linear texture or
  fabric within the rock.
• Slaty cleavage (pre-existing platy minerals
  aligned during metamorphism).
• Schistose texture (platy or needle-shaped
  minerals grow in response to differential stress.

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Foliations and Lineations
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Non-foliated rock - photomicrograph
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Foliated rock - photomicrograph