<p>Yes, they are. It's not the sills or dykes that "jump", it's the magma. Depending on the various parameters such as viscosity, stress, temperature, pressure, and local conditions and availability of joints, the magma will flow either as a sill or a dyke (or some other intrusive body).</p>

<p>Notice that your two sketches are basically the same thing - it's just the in one case the sill is the dominant structure whereas the dyke is more dominant in the second sketch.</p>

<p>The flow regime can definitely change from a "dyke" to a "sill" and vice versa. Here's a schematic diagram:</p>

<p><a href="https://i.sstatic.net/0xuxm.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/0xuxm.png" alt="enter image description here"></a> (source: USGS)</p>

<p>I also had a quick Internet search and came up with this great example from nature:</p>

<p><a href="https://i.sstatic.net/KNhja.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/KNhja.jpg" alt="enter image description here"></a></p>

<p>You can read more about it at <a href="http://geotripper.blogspot.com.au/2015/03/another-cool-california-roadcut-dike.html" rel="nofollow noreferrer">Geotripper</a> blog by Garry Hayes.</p>

CC BY-SA 3.0
2016-01-27T09:16:09.723Z
2016-01-27T11:15:29.930Z
2016-01-27T11:15:29.930Z
Gimelist
<p>Transgressive sills "jump" between bedding planes, following joints:</p>

<pre><code>_______________________
_______________________
___________/  _________
_____________/_________
_______________________
</code></pre>

<p>But can dykes do the same?</p>

<pre><code>___________________  ___
__________________/ /___
_________________/ /____
____________/ ____/_____
___________/ /__________
__________/ /___________
</code></pre>

<geology><volcanology><structural-geology><magmatism><igneous>
Do discordants dykes ever travel concordantly (are transgressive dykes a thing)?
Tim
# Do discordants dykes ever travel concordantly (are transgressive dykes a thing)?

(Asked by: username_0 on 2016-01-26)

Transgressive sills "jump" between bedding planes, following joints:

```
_______________________
_______________________
___________/  _________
_____________/_________
_______________________

```

But can dykes do the same?

```
___________________  ___
__________________/ /___
_________________/ /____
____________/ ____/_____
___________/ /__________
__________/ /___________

```

**Tags:** geology, volcanology, structural-geology, magmatism, igneous


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## 1 answers

### Answer by username_1 on 2016-01-27. Score: 4 | Accepted answer

Yes, they are. It's not the sills or dykes that "jump", it's the magma. Depending on the various parameters such as viscosity, stress, temperature, pressure, and local conditions and availability of joints, the magma will flow either as a sill or a dyke (or some other intrusive body).

Notice that your two sketches are basically the same thing - it's just the in one case the sill is the dominant structure whereas the dyke is more dominant in the second sketch.

The flow regime can definitely change from a "dyke" to a "sill" and vice versa. Here's a schematic diagram:

[![enter image description here](https://i.sstatic.net/0xuxm.png)](https://i.sstatic.net/0xuxm.png) (source: USGS)

I also had a quick Internet search and came up with this great example from nature:

[![enter image description here](https://i.sstatic.net/KNhja.jpg)](https://i.sstatic.net/KNhja.jpg)

You can read more about it at [Geotripper](http://geotripper.blogspot.com.au/2015/03/another-cool-california-roadcut-dike.html) blog by Garry Hayes.


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