Over 90% of ancient carbonates are biogenic. Key agents:
Subaerial carbonate crusts formed in soils within arid or semi-arid zones due to evaporation of groundwater. 5. Classification Systems
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Once deposited, carbonate sediments undergo profound physical and chemical transformations during burial. Because carbonate minerals are highly soluble, they are far more susceptible to diagenesis than quartz sands. origin of carbonate sedimentary rocks pdf extra quality
To understand the origin of carbonate sedimentary rocks, scientists employ several classification systems that group rocks by their texture and composition. The two most widely used are:
), shallow, photic zone waters clear of siliciclastic mud. It features high accumulation rates driven by corals, green algae, and larger benthic foraminifera. The Cool-Water Factory
Spherical to sub-oval microcrystalline carbonate grains that lack internal structure. While some originate by the mechanical rounding of semi-lithified carbonate mud clasts, the vast majority are fecal pellets produced by endobenthic gastropods, crustaceans, and polychaetes. Over 90% of ancient carbonates are biogenic
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Abiotic precipitation occurs when physical forces drive supersaturation. Examples include:
): Fluctuations reflect shifts in the global carbon cycle, rates of organic matter burial, and major biotic crises. Sharp negative excursions often correlate with mass extinction events and massive releases of greenhouse gases. Oxygen Isotopes ( Classification Systems This article is structured into the
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The origin of , primarily limestones and dolostones , is a complex interplay of biological activity and chemical precipitation. Unlike siliciclastic rocks (like sandstone), which form from the erosion of pre-existing landmasses, carbonates are largely "born, not made". They typically form in situ within "carbonate factories"—warm, shallow marine environments where life flourishes. 1. Biological and Chemical Foundations
. It is precipitated by modern echinoderms, coralline algae, and bryozoans, but is metastable and readily converts to LMC during diagenesis. Aragonite ( CaCO3CaCO sub 3