<p>The layers correspond to thousands of years, i.e. 23,000 years in the Danien timeline: <a href="https://i.sstatic.net/Rzaen.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Rzaen.jpg" alt="enter image description here" /></a></p>
<p>The page sais that there is a variation of 23,000 for precession of the equinoxes and 100,000 for variation of ellipticity. <a href="https://planet-terre.ens-lyon.fr/image-de-la-semaine/Img421-2013-04-15.xml" rel="nofollow noreferrer">https://planet-terre.ens-lyon.fr/image-de-la-semaine/Img421-2013-04-15.xml</a></p>

CC BY-SA 4.0
2020-05-25T08:51:05.477Z
here is some background information about how and why the equinoxes changes https://en.wikipedia.org/wiki/Precession#Axial_precession_(precession_of_the_equinoxes)
trond hansen
CC BY-SA 4.0
2020-05-24T10:54:12.180Z
2021-01-20T07:47:13.173Z
2021-01-20T07:47:13.173Z
bandybabboon
<p>These limestone-clay rocks are very common in the Alps, they come from weather changes. </p>

<p>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? </p>

<p><a href="https://i.sstatic.net/xQmMR.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/xQmMR.jpg" alt="enter image description here"></a>
From the wiki page which is only in French: <a href="https://fr.wikipedia.org/wiki/Formation_marno-calcaire" rel="nofollow noreferrer">https://fr.wikipedia.org/wiki/Formation_marno-calcaire</a></p>

<rocks><fossils><stratigraphy><limestone>
What is the time period of these chalk/clay layers?
bandybabboon
# What is the time period of these chalk/clay layers?

(Asked by: username_0 on 2020-05-24)

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](https://i.sstatic.net/xQmMR.jpg)](https://i.sstatic.net/xQmMR.jpg)
From the wiki page which is only in French: <https://fr.wikipedia.org/wiki/Formation_marno-calcaire>

**Tags:** rocks, fossils, stratigraphy, limestone


---

## 1 answers

### Answer by username_0 on 2020-05-24. Score: 2

The layers correspond to thousands of years, i.e. 23,000 years in the Danien timeline: [![enter image description here](https://i.sstatic.net/Rzaen.jpg)](https://i.sstatic.net/Rzaen.jpg)

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>

> **Comments:**
> **username_1**: here is some background information about how and why the equinoxes changes https://en.wikipedia.org/wiki/Precession#Axial_precession_(precession_of_the_equinoxes)  

---

