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These limestone-clay rocks are very common in the Alps, they come from weather changes.

How many years does it take to make one of the rock bands? 7 years, equivalent to an el-nino type event? 1000 years? 20,000 years?

enter image description here From the wiki page which is only in French: https://fr.wikipedia.org/wiki/Formation_marno-calcaire

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    $\begingroup$ upper Jurassic/lower Cretaceous, warm climate, flooded continental shelves, climate cycles from orbital parameters, Milankovic cycles. Here: probably ~40ky, maybe ~20ky. $\endgroup$ – a_donda May 25 at 8:07
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The layers correspond to thousands of years, i.e. 23,000 years in Spain in the Danien timeline: enter image description here

The page sais that there is a variation of 23,000 for precession of the equinoxes and 100,000 for variation of ellipticity. https://planet-terre.ens-lyon.fr/image-de-la-semaine/Img421-2013-04-15.xml

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