Knowra Carbon isotope excursion Carbon isotope excursion A marked shift in the ratio of carbon isotopes, usually expressed as δ¹³C, recorded in rocks or fossils. It can signal changes in the global carbon cycle or in the sources and sinks of carbon.
Carbon isotope ratio : The proportion of carbon isotopes in a sample, commonly expressed as δ¹³C relative to a standard. Excursions are measured as changes in this ratio through a rock sequence.
Paleocene–Eocene Thermal Maximum : A brief interval about 56 million years ago marked by rapid global warming and major environmental change. Its prominent negative carbon isotope excursion is a defining geological signal.
Chemostratigraphy : The correlation and subdivision of rock layers using their chemical signatures. Carbon isotope patterns can identify and correlate strata across distant sites.
Carbon isotope mass balance : The accounting of carbon amounts and isotope compositions entering, leaving, and stored in a system. Mass-balance models test which source and sink changes could produce an excursion.
Isotope fractionation : The separation of isotopes caused by differences in their physical, chemical, or biological behavior. Fractionation gives carbon sources and processes distinct isotope signatures.
End-Permian extinction : The largest known mass extinction, occurring about 252 million years ago at the Permian–Triassic boundary. A pronounced isotope disturbance accompanies evidence for severe carbon-cycle disruption.
Stable isotope analysis : The measurement of stable-isotope abundances in materials to investigate their origins and histories. It provides the analytical basis for detecting carbon isotope excursions.
Carbonate carbon isotope record : The carbon isotope composition preserved in sedimentary carbonate minerals. Its fidelity can be affected by water chemistry, ecology, and later alteration.
Carbon cycle : The movement of carbon among the atmosphere, oceans, living things, soils, and rocks. Large excursions record major reorganizations of carbon reservoirs and fluxes.
Toarcian Oceanic Anoxic Event : A Jurassic interval of widespread marine oxygen depletion, associated with warming and carbon-cycle change. Its negative carbon isotope excursion is linked to substantial carbon input.
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