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diagenesis

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anchimetamorphism

Overview page. Subjects: Earth Sciences and Geography.

A metamorphic grade in sedimentary rocks where changes due to diagenesis are overtaken by the very earliest phases of metamorphism.

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ankerite

Overview page. Subjects: Earth Sciences and Geography.

Mineral, Ca(Mg.Fe)(CO3)2; sp. gr. 2.9–3.2; hardness 3.5–4.0; trigonal; yellowish-brown, sometimes white, yellow, or grey; white streak; vitreous lustre; crystals can be rhombohedral, but...

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biosparite

Overview page. Subjects: Earth Sciences and Geography.

A limestone consisting of bioclasts together with a sparry calcite cement (sparite). It is the product of an accumulation of clean-washed, mud-free shell debris, with diagenetic cement...

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carbon isotopes

Overview page. Subjects: Ecology and Conservation.

The naturally occurring isotopes of carbon, of which there are three: 12C making up about 98.9 per cent; 13C about 1.1 per cent; and 14C whose amount is negligible, but which is detectable...

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catagenesis

Overview page. Subjects: Earth Sciences and Geography.

Following diagenesis, in which sedimentary material is compressed and undergoes chemical changes, a phase in the formation of petroleum and natural gas during which continuing sedimentation...

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chert

Overview page. Subjects: Science and Mathematics.

1 Chalcedonic (see chalcedony) variety of cryptocrystalline silica, SiO2, that occurs as nodules or irregular masses in a sedimentary environment, often in association with...

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Choquette and Pray classification

Overview page. Subjects: Earth Sciences and Geography.

A widely used, descriptive classification of porosity types developed in carbonates. Primary porosity types are classified as: interparticle (pores between the grains); framework (pore...

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consolidation

Overview page. Subjects: Earth Sciences and Geography.

In geology, any process by which loose earth materials become compacted, including cementation, diagenesis, recrystallization, dehydration, and metamorphism. In soil mechanics, the term...

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desert rose

Overview page. Subjects: Earth Sciences and Geography.

A radiating series of petal-shaped calcite or gypsum minerals, sometimes resembling the form of a rose, developed in the early stages of sand diagenesis in arid regions, and particularly in...

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dolomitization

Overview page. Subjects: Earth Sciences and Geography.

The transformation of limestone to dolomite (1), by the conversion of CaCO3 to CaMg(CO3)2. This occurs by the addition of magnesium to the sediment or rock and may take place soon after...

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elite

Overview page. Subjects: Earth Sciences and Geography.

In ichnology, applied (a) to a structure constructed within a sediment by living organisms that indicates a high level of biological activity because of its high content of oxygen or...

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halmyrolysis

Overview page. Subjects: Earth Sciences and Geography.

Early diagenesis, modification, or decomposition of sediments on the sea floor. For example, both the breakdown of ferromagnesian minerals, and the growth of glauconite aggregates in...

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iron formation

Overview page. Subjects: Earth Sciences and Geography.

Iron-rich sedimentary rocks, mostly of Precambrian age, containing at least 15% iron. The iron occurs as an oxide, silicate, carbonate, or sulphide, deposited as laminated, deep-water,...

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ironstone

Overview page. Subjects: Earth Sciences and Geography.

Iron-rich sedimentary rock. The source of the iron is primary and/or diagenetic (see diagenesis), developed by a number of possible processes. These include: (a) replacement of carbonate...

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lithification

Overview page. Subjects: Earth Sciences and Geography.

Processes by which sediments are converted into hard rock. These include the expulsion of air, or the suffusion into the rock of cementing agents in solution, like quartz.

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neomorphism

Overview page. Subjects: Earth Sciences and Geography.

The diagenetic replacement (see diagenesis) of a mineral by a different crystal form of the same mineral. In limestones neomorphism often results in the replacement of calcite by coarser...

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oxygen isotope

Overview page. Subjects: Earth Sciences and Geography — Environmental Science.

Any of the oxygen atoms that have the same atomic number (number of protons) but different mass numbers (different numbers of neutrons). The two common stable isotopes of oxygen are 16O and null...

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phosphorite

Overview page. Subjects: Earth Sciences and Geography.

A sedimentary rock rich in phosphate, usually in the form of carbonate hydroxyl fluorapatite (Ca10(PO4CO3)6F2–3). Phosphorites occur as nodules and crusts formed in oceanic areas where...

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post-depositional remanent magnetization

Overview page. Subjects: Earth Sciences and Geography.

The magnetization acquired by a sedimentary rock after deposition and before undergoing metamorphism, mostly associated with chemical remanent magnetization as ferromagnetic minerals grow...

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sandstone

Overview page. Subjects: Science and Mathematics — Architecture.

Sedimentary rock composed of consolidated sand or grit bound together, with a high silica or calcite content. It can be soft and easily damaged by rain, etc., or it can be very hard. It has...

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