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Wednesday, 5 October 2022

Marine Isotope stages -- alternating glacials and interglacials


A vast store of marine (sea floor) cores, used for the refinement of MIS data

It can be confusing when MIS numbers are given instead of familiar names for glacial and interglacial stages.  There is a good explanation on Wikipedia:

https://en.wikipedia.org/wiki/Marine_isotope_stages 

Part of the problem in understanding is that the sequence begins with MIS-1 (the most recent episode) at the top, and MIS-20 (c 814,000 years ago) towards the bottom.  The reason is that the information is obtained from deep sea cores, and nobody s quite certain where the bottom is........

In contrast, in geology the PreCambrian would be given number 1 and successive geological eras (with younger strata) would be given higher and higher numbers.

Anyway, in the UK the sequence looks something like this:

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MIS 2 – 29,000 yrs BP Late Devensian or LGM -- peak glaciation. COLD

MIS 3 – 57,000 mid-Devensian

MIS 4 – 71,000 Onset of Last Glacial Period / Weichselian / Devensian / Wisconsin in North America

MIS 5 – 130,000 Eemian interglacial, or Ipswichian in Britain -- many substages. WARM

MIS 6 – 191,000 Illinoian glacial in North America, Saalian in northern Europe and Late Wolstonian in Britain)

MIS 7 – 243,000 (Aveley Interglacial in Britain) WARM

MIS 8 – 300,000 Early Wolstonian in Britain. COLD

MIS 9 – 337,000 (Purfleet Interglacial in Britain) WARM

MIS 10 – 374,000 COLD

MIS 11 – 424,000 Hoxnian Interglacial in Britain WARM

MIS 12 – 478,000 Anglian Glacial in Britain, Elster glaciation in northern Europe. COLD\

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Beware -- that sequence is not universally agreed!  Some sub-phases are given the letters a, b, c, d etc -- but these are difficult because smaller phases are not always synchronous in different areas.

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