SEDIMENTARY ARCHIVES Classification of Sedimentary Rocks Carbonates.

SEDIMENTARY ARCHIVESClassification of Sedimentary Rocks

Carbonates


CarbonatesOrigin of carbonate sediments

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.

These lime muds lithify to form fine-grained limestone.

SEDIMENTARY ARCHIVES

SEDIMENTARY ARCHIVESClassification of Sedimentary RocksCarbonates

Fossiliferous limestoneBiomicriteBiosparite


Oolitic limestoneOomicriteOosparite


DolostoneComposed 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.

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.

Dolomitization may be related to times of high sea level worldwide, under favorable climatic conditions.


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 ARCHIVESSea Level Changes

Eustatic Sea Level ChangeGlobal change in sea level position

Caused by: Glacial advance and retreatChange in spreading rates

Effect lowland areas


Sequence Stratigraphy

Epeiric seasSeas covered continentsProduced packages called sequencesLed to sequence stratigraphy

SEDIMENTARY ARCHIVESSea 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.


http://www.glossary.oilfield.slb.com/Display.cfm?Term=group


Vail Curve

http://strata.geol.sc.edu/clastic-movie.html



http://strata.geol.sc.edu/clastic-movie.html

THE FOSSIL RECORDPaleontology

Attempts to understand all aspects of the successionof plants and animals over time.

Based on study of fossils

Archaeopteryx

THE FOSSIL RECORDPaleontology

Fossil PreservationCover this aspect in laboratory

Fossilization fortuitous

Chances enhanced byHard partsRapid burial

Environments Oceans, lakes and streams

THE FOSSIL RECORDTaphonomy

What happens to an organism from time of death to preservation as a fossil

Soft parts usually lost

SEDIMENTARY ARCHIVES Classification of Sedimentary Rocks Carbonates.

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