<p>Normally, limestone is going to be dated via the fossil record and with the relationship it has with other formations above and below.</p>
<p>They can be dated using isotopes, potassium - argon I would suspect. However, that is quite rare to date limestone like this as it takes time and it's not cheap, couple hundred dollars I think.</p>
<p>You may ask how they know the age of the fossils; by using other fossils that they are found with and knowing these fossils age etc. Obviously at the start of the 'chain of relationships' isotope dating had to be used, but like I said, due to the price and time, relational dating is what you will mostly be doing when in the field.</p>
<p>Professionally, there's no real use in knowing the age of the rock to the 1Ma. Knowing the relationship between this strata and the rest is much more important in identifying the strata in question.</p>

CC BY-SA 4.0
2024-05-25T18:00:17.660Z
2024-05-25T18:00:17.660Z
Mr.inquisitive
<p>Usually you date Limestone, and in fact almost any sedimentary rock, <a href="https://en.wikipedia.org/wiki/Stratigraphy" rel="nofollow noreferrer">Strategraphically</a>, that is to say in relation to other rocks around them. Strategraphic dating relies on a couple of factors:</p>
<ul>
<li><p>The first is sediment pulses, in most environments the rate of sediment supply varies throughout the year. This means that individual layers within the sedimentary unit represent particular periods of time (mush like tree rings), usually a year each.</p>
</li>
<li><p>Secondly sediments can be dated according to the intrusion through them of igneous rocks that can be geophysically dated using the ratios of certain radioisotopes such as <a href="https://en.wikipedia.org/wiki/K%E2%80%93Ar_dating" rel="nofollow noreferrer">Potassium-Argon</a> or <a href="https://en.wikipedia.org/wiki/Uranium%E2%80%93lead_dating" rel="nofollow noreferrer">Uranium-Lead</a> datings.</p>
</li>
</ul>
<p>Sometimes, when there are discernible fossils in the formation, dates for the layers in which fossils are found can give you a date based on records of when those species lived. Fossils can be vanishingly rare in some Limestones while others teem with them.</p>

CC BY-SA 4.0
2024-05-28T07:04:47.527Z
2024-05-28T07:04:47.527Z
Ash
<p>Typically uncontaminated rock layers can be dated based on isotope's often found in the rock strata. Carbon isotopes like 13,14 differ than marine limestone deposits thus determining which formed above water and which below.</p>

CC BY-SA 4.0
2024-05-25T18:04:59.403Z
I don't think Carbon isotopes are used much for dating limestone, I think Carbon is only used for dating up to 80000 years. Most limestone I've encountered is 11Ma or older. 
Vast majority of limestone is formed in the ocean. The only limestones that I am aware of that aren't from the ocean would be karstic formations, however that's formed by the dissolution of the preexisting limestone formation, forming a cave, then the subsequent precipitation of stalagmites etc.
Mr.inquisitive
CC BY-SA 4.0
2024-05-26T19:07:59.537Z
@Mr.inquisitive  I ran into a young-Earth creationist who was maintaining that all limestone is less than 10k years old.  It was hard not to just laugh.  But I couldn't think of how limestone formations are dated so there wasn't much I could say except that geologists would vehemently disagree.
Traildude
CC BY-SA 4.0
2024-05-24T04:50:27.583Z
2024-05-24T04:50:27.583Z
LazyReader
<p>I know that limestone is found in a variety of geological formations, and I thought it would be useful if some knowledgeable people weighed in on how the ages of these layers are determined.</p>

<geology><dating><limestone><age>
How is limestone dated?
Traildude
# How is limestone dated?

(Asked by: username_0 on 2024-05-24)

I know that limestone is found in a variety of geological formations, and I thought it would be useful if some knowledgeable people weighed in on how the ages of these layers are determined.

**Tags:** geology, dating, limestone, age


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## 3 answers

### Answer by username_1 on 2024-05-25. Score: 1

Normally, limestone is going to be dated via the fossil record and with the relationship it has with other formations above and below.

They can be dated using isotopes, potassium - argon I would suspect. However, that is quite rare to date limestone like this as it takes time and it's not cheap, couple hundred dollars I think.

You may ask how they know the age of the fossils; by using other fossils that they are found with and knowing these fossils age etc. Obviously at the start of the 'chain of relationships' isotope dating had to be used, but like I said, due to the price and time, relational dating is what you will mostly be doing when in the field.

Professionally, there's no real use in knowing the age of the rock to the 1Ma. Knowing the relationship between this strata and the rest is much more important in identifying the strata in question.


---

### Answer by username_2 on 2024-05-28. Score: 0

Usually you date Limestone, and in fact almost any sedimentary rock, [Strategraphically](https://en.wikipedia.org/wiki/Stratigraphy), that is to say in relation to other rocks around them. Strategraphic dating relies on a couple of factors:

* The first is sediment pulses, in most environments the rate of sediment supply varies throughout the year. This means that individual layers within the sedimentary unit represent particular periods of time (mush like tree rings), usually a year each.
* Secondly sediments can be dated according to the intrusion through them of igneous rocks that can be geophysically dated using the ratios of certain radioisotopes such as [Potassium-Argon](https://en.wikipedia.org/wiki/K%E2%80%93Ar_dating) or [Uranium-Lead](https://en.wikipedia.org/wiki/Uranium%E2%80%93lead_dating) datings.

Sometimes, when there are discernible fossils in the formation, dates for the layers in which fossils are found can give you a date based on records of when those species lived. Fossils can be vanishingly rare in some Limestones while others teem with them.


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### Answer by username_3 on 2024-05-24. Score: -1

Typically uncontaminated rock layers can be dated based on isotope's often found in the rock strata. Carbon isotopes like 13,14 differ than marine limestone deposits thus determining which formed above water and which below.

> **Comments:**
> **username_1**: I don't think Carbon isotopes are used much for dating limestone, I think Carbon is only used for dating up to 80000 years. Most limestone I've encountered is 11Ma or older.  Vast majority of limestone is formed in the ocean. The only limestones that I am aware of that aren't from the ocean would be karstic formations, however that's formed by the dissolution of the preexisting limestone formation, forming a cave, then the subsequent precipitation of stalagmites etc.  
> **username_0**: @username_1  I ran into a young-Earth creationist who was maintaining that all limestone is less than 10k years old.  It was hard not to just laugh.  But I couldn't think of how limestone formations are dated so there wasn't much I could say except that geologists would vehemently disagree.  

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