Marine isotope stage

Oxygen isotope stage ( engl. Marine Isotopic Stage, MIS or abbreviation Oxygen Isotopic Stage, abbreviation OIS ) or Isotope Stage is a term used in geology. He referred datings based on the ratio of the isotopes 16O and 18O of oxygen. In the calcite, which can be found in the sediments of the ocean floor including in the skeletons of fossil foraminifera, different amounts of available oxygen isotopes are incorporated depending on hot or cold period. This also statements about the course of the Earth's climate in the cold periods of the Quaternary can be made. Similar studies exist for the entire Tertiary.

Principle

Local affect the reduced ocean temperatures during the cold times on the isotope ratio of the calcareous foraminifera, because these fractionated during installation of the calcium carbonate in their case the 16O/18O-Verhältnis at lower temperatures towards the heavier isotope (temperature effect). An increased evaporation in the habitat of the foraminifera, but also an increased input of isotopically lighter meltwater leads to a shift of the 16O/18O-Verhältnis in the water and thus in the case of calcareous ( Salinitätseffekt ). Due to the fact that the ice effect causes the greatest impact and the effect of temperature shifts of 16O/18O-Verhältnisses in the same direction, from this you can develop a stratigraphy of marine sediments, the marine oxygen isotope stratigraphy. The normalized ratio of 16O/18O is called Δ18O or delta -O -18.

The first systematic studies of the variation of oxygen isotopes in ocean sediments were made in the 1950s by Cesare Emiliani of planktonic foraminifera in deep-sea cores from the Caribbean. He noticed the cyclical fluctuations of the measured values ​​and concluded that they represent cold and warm periods. He numbered the fluctuations by starting counting at 1 from the present time backwards. In the following years, numerous studies have been conducted in this area, and at the beginning of the 1970s were still many additional scientific work that eventually led to the development of an oxygen - isotope stratigraphy of the Quaternary. Here in the Pleistocene more than a hundred cycles were distinguished that correspond to various hot - cold period cycles.

Mid-1970s, the principle by Nicholas Shackleton and James Kennett and the Working Group of Samuel Savin to the entire Cenozoic was extended. It was found that the oxygen isotope ratios after the Cretaceous / Tertiary boundary were also subject to substantial fluctuations. However, the observed in the Quaternary rapid change of isotope ratios are not clearly discernible, even if individual, well-studied sections show clear evidence that such cycles also existed in the Tertiary.

Marine oxygen isotope stratigraphy of the Quaternary

The current ice age is divided from the base of the Quaternary ( the beginning of the Gelasiums ) in front of a little less than 2.6 million years ago in 103 isotope stages and backward numbered. This odd numbers denote the warm periods ( interstadials or interglacials ), but just cold periods ( glacials ). The current warm period thus corresponds to the marine oxygen isotope stage 1 (abbreviated to MIS 1 for the internationally common Marine Isotope Stage 1), the " climax " of the last glacial period corresponds to the MIS 2 Since after the first statement of the structure further isotopic variations could be detected, additional stages were erected by attaching a letter, for example 5e for the Eemian.