<p>It depends on which classification system you're using, which varies by country. </p>

<p><strong>According to the <a href="http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/survey/class/" rel="nofollow">USDA Soil Taxonomy</a>, R is used to designate bedrock</strong>. </p>

<p>Other countries and classification systems may (or may not) use different letters. Check out the <a href="http://www.itc.nl/~rossiter/research/rsrch_ss_class.html" rel="nofollow">Compendium of On-Line Soil Survey Information</a> for other classification systems. </p>

<p>To answer your second question, there are standards, depending on which classification system or country or even discipline you're in. Soil scientists in the US use the USDA soil taxonomy, or R to designate bedrock. </p>

CC BY-SA 3.0
2014-05-08T14:10:09.120Z
2014-11-21T15:29:11.473Z
2014-11-21T15:29:11.473Z
derelict
<p>According to <a href="https://en.wikipedia.org/wiki/Soil_horizon#R_horizon" rel="noreferrer">Wikipedia</a> and <a href="http://www.nature.com/scitable/knowledge/library/what-are-soils-67647639" rel="noreferrer">Nature.com</a>, <strong>"R Horizon" is the official letter for bedrock.</strong></p>

<p><img src="https://i.sstatic.net/c2xMO.jpg" alt="Example soil with designations that communicate the soil formation processes occurring in each horizon."></p>

<p><strong><em>CAPTION:</strong> Example soil with designations that communicate the soil formation processes occurring in each horizon.</em></p>

CC BY-SA 3.0
2014-05-07T03:03:38.507Z
2014-05-07T03:03:38.507Z
blunders
<p>What is the official letter for the bedrock soil horizon? I know that the letters to represent the A, B, and C horizons are widespread, but the fourth layer (bedrock) is referred to with different names. Some call it the D-Horizon, some the R-Horizon, and some just say bedrock. Is there any standard or official term, and if so, what is it?</p>

CC BY-SA 3.0
2014-04-19T01:34:32.097Z
Is there anything in this question that the wikipedia [soil horizon](https://en.wikipedia.org/wiki/Soil_horizon) page doesn't answer? Or, to be more useful, could you reference that page, and use it to ask a more specific question?
naught101
CC BY-SA 3.0
2014-04-19T08:42:17.683Z
For geologists there is the Shell Standard Legend, but the problem is that most geologists never map bedrock as a unit (but need to differentiate it into lithologies) http://www.ogp.org.uk/news/2014/shell-releases-its-standard-legend-to-industry-and-academia/
tobias47n9e
CC BY-SA 3.0
2014-04-19T12:41:04.513Z
@naught101 Quoted from that Wikipedia page - "D horizons are not universally distinguished"
Timtech
<terminology><soil><bedrock>
Horizon letter for bedrock
Timtech
# Horizon letter for bedrock

(Asked by: username_0 on 2014-04-18)

What is the official letter for the bedrock soil horizon? I know that the letters to represent the A, B, and C horizons are widespread, but the fourth layer (bedrock) is referred to with different names. Some call it the D-Horizon, some the R-Horizon, and some just say bedrock. Is there any standard or official term, and if so, what is it?

**Tags:** terminology, soil, bedrock

> **Comments:**
> **username_1**: Is there anything in this question that the wikipedia [soil horizon](https://en.wikipedia.org/wiki/Soil_horizon) page doesn't answer? Or, to be more useful, could you reference that page, and use it to ask a more specific question?  
> **username_2**: For geologists there is the Shell Standard Legend, but the problem is that most geologists never map bedrock as a unit (but need to differentiate it into lithologies) http://www.ogp.org.uk/news/2014/shell-releases-its-standard-legend-to-industry-and-academia/  
> **username_0**: @username_1 Quoted from that Wikipedia page - "D horizons are not universally distinguished"  

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## 2 answers

### Answer by username_4 on 2014-05-07. Score: 7 | Accepted answer

According to [Wikipedia](https://en.wikipedia.org/wiki/Soil_horizon#R_horizon) and [Nature.com](http://www.nature.com/scitable/knowledge/library/what-are-soils-67647639), **"R Horizon" is the official letter for bedrock.**

![Example soil with designations that communicate the soil formation processes occurring in each horizon.](https://i.sstatic.net/c2xMO.jpg)

***CAPTION:*** Example soil with designations that communicate the soil formation processes occurring in each horizon.


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### Answer by username_3 on 2014-05-08. Score: 7

It depends on which classification system you're using, which varies by country.

**According to the [USDA Soil Taxonomy](http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/survey/class/), R is used to designate bedrock**.

Other countries and classification systems may (or may not) use different letters. Check out the [Compendium of On-Line Soil Survey Information](http://www.itc.nl/~rossiter/research/rsrch_ss_class.html) for other classification systems.

To answer your second question, there are standards, depending on which classification system or country or even discipline you're in. Soil scientists in the US use the USDA soil taxonomy, or R to designate bedrock.


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