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SEDIMENTARY ARCHIVES Classification of Sedimentary Rocks Carbonates SEDIMENTARY ARCHIVES Classification of Sedimentary Rocks Carbonates Origin 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 ARCHIVES Classification of Sedimentary Rocks Carbonates Fossiliferous limestone Biomicrite Biosparite SEDIMENTARY ARCHIVES Classification of Sedimentary Rocks Carbonates Oolitic limestone Oomicrite Oosparite SEDIMENTARY ARCHIVES 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. 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. SEDIMENTARY ARCHIVES Classification of Sedimentary Rocks 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 ARCHIVES Sea Level Changes Eustatic Sea Level Change Global change in sea level position Caused by: Glacial advance and retreat Change in spreading rates Effect lowland areas SEDIMENTARY ARCHIVES Sea Level Changes Sequence Stratigraphy Epeiric seas Seas covered continents Produced packages called sequences Led to sequence stratigraphy SEDIMENTARY ARCHIVES 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. SEDIMENTARY ARCHIVES Sea Level Changes Vail Curve SEDIMENTARY ARCHIVES Sea Level Changes Sequence Stratigraphy SEDIMENTARY ARCHIVES Sea Level Changes Sequence Stratigraphy http://strata.geol.sc.edu/clastic-movie.html THE FOSSIL RECORD Paleontology Attempts to understand all aspects of the succession of plants and animals over time. Based on study of fossils Archaeopteryx THE FOSSIL RECORD Paleontology Fossil Preservation Cover this aspect in laboratory Fossilization fortuitous Chances enhanced by Hard parts Rapid burial Environments Oceans, lakes and streams THE FOSSIL RECORD Taphonomy What happens to an organism from time of death to preservation as a fossil Soft parts usually lost