What is the time period of these chalk/clay layers? 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? 


From the wiki page which is only in French: https://fr.wikipedia.org/wiki/Formation_marno-calcaire
The layers correspond to thousands of years, i.e. 23,000 years in the Danien timeline: 
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