sedimentary rocks interpretations. what do sedimentary rocks record? source of sediment erosion and...
Post on 21-Dec-2015
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What do Sedimentary Rocks Record?
• Source of sediment• Erosion and Transport Agent• Distance of Transport• Depositional Environment• Paleogeography/Tectonic Setting
Interpretation of Composition
Detrital Rocks:• Source of sediment• Exposure to Weathering (Distance of Transport) (Type of Climate)
Note About Detrital Rock Color & Composition
•Grain SizeSmaller is often darker
•CompositionCarbon - black or brownQuartz - tan, clear, whiteOrthoclase - orange
•Depositional EnvironmentIron on land - redIron in deep, oxygen poor water - green
Interpretation: Grain Size
• Gravel
• Sand
• Silt
• Clay
• River, Beach
• River, Beach, Desert
• Delta, Shallow Ocean
• Deep Ocean, Lake, Swamp
• High Energy
• Low Energy
Detrital Rock Names
(Based Primarily on Grain Size)
Sand Sized: Sandstone
Gravel Sized:Conglomerate
Siltstone Shale
Mud Sized:Mudstone
Interpretation: Sorting
Interpretation:Poorly SortedWell Sorted
Transport AgentGravity and Glaciers (and Rivers)Water and Wind
Matrix Supported Conglomerate
(Glacial/Landslide Deposits)
“Modern”Glacial Sediments
2.2 Gyr Conglomerate
Formation of Limestone
Calcite Precipitates inWarm WaterWater Under Low Pressure (Shallow)
Or
It is secreted by biological organismsClams, Mussels, Scallops, etc.CoralsForaminifera
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Intermission: QuizWhat can you say about the history
of this rock?
Quartz Sandstone
Deposited in a beach/river or desert,
very far from the source of the sediment.
Intermission: QuizWhat can you say about the history
of this rock?
Shale
Deposited in a quiet water environment (deep ocean, lake,
lagoon). Dark color implies oxygen-poor environment, rich in
organic material.