<p>The main interest of tephrochronology (i.e. dating sediments using volcanic ash layer) is specifically its instantaneity (relatively to geological timescale of course). It is precisely used for higher-resolution dating. An example would be the Kawakawa/Oruanui tephra from New Zealand which is a good isochronous marker bed at 26.5 ka, spread over 1500km, but represents probably only a few months of volcanic activity (see e. g. <strong>Manville &amp; Wilson 2006</strong>)</p>

<p>Important factors vis-à-vis the usefulness of a specific ash layer however are its geographical extent (a volcanic event that will spread an ash layer over a whole basin would be more useful in that it will be used to correlate a large number of sites together) and maybe its volume (you need a minimum amount of material to work with, I'll assume).</p>

<p><sub>Reference: Manville V. &amp; Wilson C. J. N., 2006. <a href="http://dx.doi.org/10.1080/00288306.2004.9515074">The 26.5 ka Oruanui eruption, New Zealand: A review of the roles of volcanism and climate in the post‐eruptive sedimentary response.</a> New Zealand Journal of Geology and Geophysics, 47: 525-547. </sub></p>

CC BY-SA 3.0
2014-06-20T08:34:40.250Z
2014-06-21T10:51:45.773Z
2014-06-21T10:51:45.773Z
plannapus
<p>I wanted to know if volcanic ash deposits found in the geologic record are most useful in correlating the age of rock layers if the volcanic ash was distributed over a large area during a short period of time or large area during a long period of time</p>

<p>I was thinking over a long period of time because it helps more with determining a rocks age.</p>

<geology><volcanology><sedimentology><stratigraphy>
Determining a rock age using volcanic ash layer
charlston
# Determining a rock age using volcanic ash layer

(Asked by: username_0 on 2014-06-19)

I wanted to know if volcanic ash deposits found in the geologic record are most useful in correlating the age of rock layers if the volcanic ash was distributed over a large area during a short period of time or large area during a long period of time

I was thinking over a long period of time because it helps more with determining a rocks age.

**Tags:** geology, volcanology, sedimentology, stratigraphy


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## 1 answers

### Answer by username_1 on 2014-06-20. Score: 8

The main interest of tephrochronology (i.e. dating sediments using volcanic ash layer) is specifically its instantaneity (relatively to geological timescale of course). It is precisely used for higher-resolution dating. An example would be the Kawakawa/Oruanui tephra from New Zealand which is a good isochronous marker bed at 26.5 ka, spread over 1500km, but represents probably only a few months of volcanic activity (see e. g. **Manville & Wilson 2006**)

Important factors vis-à-vis the usefulness of a specific ash layer however are its geographical extent (a volcanic event that will spread an ash layer over a whole basin would be more useful in that it will be used to correlate a large number of sites together) and maybe its volume (you need a minimum amount of material to work with, I'll assume).

Reference: Manville V. & Wilson C. J. N., 2006. [The 26.5 ka Oruanui eruption, New Zealand: A review of the roles of volcanism and climate in the post‐eruptive sedimentary response.](http://dx.doi.org/10.1080/00288306.2004.9515074) New Zealand Journal of Geology and Geophysics, 47: 525-547.


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