Dolomitization may be related to times of high sea level worldwide, under favorable climatic conditions.
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Classification of Sedimentary Rocks
These lime muds lithify to form fine-grained limestone.
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Classification of Sedimentary Rocks
Carbonates Fossiliferous limestone Biomicrite Biosparite
Effect lowland areas
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Sea Level Changes Sequence Stratigraphy
Epeiric seas Seas covered continents Produced packages called sequences Led to sequence stratigraphy
Today, dolomite only forms in a few areas of the world where intense evaporation of seawater concentrates the magnesium.
Extensive areas of carbonate rocks of Precambrian, Paleozoic, and Mesozoic age have been altered to dolomite.
Much lime mud forms from the disintegration of calcareous algae (such as Halimeda and Penicillus).
When the calcareous algae die, their skeletons break down and disintegrate producing aragonite needle muds.
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Sea Level Changes
Vail Curve
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Sea Level Changes Sequence Stratigraphy
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Sea Level Changes Sequence Stratigraphy
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Classification of Sedimentary Rocks
Carbonates Oolitic limestone Oomicrite Oosparite
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Classification of Sedimentary Rocks
Carbonates Dolostone Composed of dolomite (CaMg(CO3)2)
The Dolomite “Problem”
Dolomite is believed to form when magnesium that has been concentrated in sea water replaces calcium carbonate in a previously deposited limestone.
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THE FOSSIL RECORD
Paleontology Attempts to understand all aspects of the succession
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Sea Level Changes Eustatic Sea Level Change
Global change in sea level position
Caused by: Glacial advance and retreat Change in spreading rates
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Classification of Sedimentary Rocks
Carbonates
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Classification of Sedimentary Rocks
Carbonates Origin of carbonate sediments
Clays, Mudrocks and Shales Mudrocks are a very fine-grained Composed of clay and silt-sized particles If the mudrock is fissile it is a -shale Typically form in low energy environments
SEDIMENTARY பைடு நூலகம்RCHIVES
Sea Level Changes Sequence Stratigraphy
SEDIMENTARY ARCHIVES
Sea Level Changes
Sequence Stratigraphy
A group of relatively conformable strata that represents a cycle of deposition and is bounded by unconformities or correlative conformities. Sequences are the fundamental unit of interpretation in sequence stratigraphy. Sequences comprise systems tracts.