Posted by: Alan Pitts | May 12, 2010

Structural Geology Trip Part 5: WV Rt 55

After two days of some exciting geologic observations, our last day in the field brought us to some amazing outcrops along the  new route 55 in West Virginia. This new highway is in many ways a road to nowhere, we saw hardly any traffic, and if you follow the massive roadway to the end, you’ll find yourself in some pretty sparsely populated areas of WV.  During the massive construction project an immense amount of material was removed which left some handsome road cuts exposed.  A few of which we stopped at and spent a good hour poking around.

Here is a great picture of the Hanging Rock Anticline  taken by Nik D.

Here is a wide view of our stop in the Hampshire formation where most of the pictures and analysis of this entry come from:

This exposure is of the Hampshire formation, Devonian in age ( 360-410 million years ago) and is characterized by sandstones and siltstones as part of  river and floodplain deposits.

With out looking too hard we were able to find several interesting structures:

The picture above is of some well defined flame structures taken by Nik D. This an example of soft sediment deformation, the lighter colored material is a more competent sandy layer that is pushing down and  displacing a less competent mud layer below. The mud layer shoots upward making these “flames” as a response to the displacement. This was one of my favorite structures we spotted all weekend. I especially like the crisp edges and genuine flame-like shape of the up-shooting mud layer.  I think a picture this great deserves at least a quick annotation.

Here is an annotated version of the picture above:

The green arrows indicate that downward pushing of the sand layer above. The blue arrow idicates the mud unit being squished up ( like toothpaste) as a response to the downward force..

Here is another larger scale feature of the outcrop that I found particularly interesting: In case you cant see it, there is a noticeable “slump” shape in the outcrop. You can see the normal orientation of the bedding is interrupted by this trough-shaped feature

Here is another view in case you are having trouble seeing it.

This is an ancient stream bed which once flowed perpendicular to the the strike of these beds. The stream left a deposit of muds and a U-shaped impression marking its path. This was really cool to me and resulted in an “ah ha ” moment . This feature really helped me tie it all together in 3 dimensions. I am so used to looking at outcrops more or less as 2 dimensional features,  like looking at a really detailed poster. Its difficult to train your mind to imagine the outcrop  as 3 dimensional features.  To see  this stream channel helped be bridge the relationship between the outcrop face and the larger rock body which it represented. A new axis  of observation opened it all up for me, and allowed me to see and imagine in 3 dimensions ( and I didn’t even have to buy any of those cheesy glasses). In this picture the stream would have been flowing right out of the picture, or right into it. At this point I cant say for sure which direction the stream was flowing, but what I can say for sure, is that I know what type of evidence to look for.

And here it is:This is another great photo from the Nik D collection (in case anyone was wondering,  I was with out a camera for most of the latter part of this trip, hence the sketches and constant use of my fellow students pictures). It shows same really amazing ripple marks. Unfortunately it is not in situ so we really cant use to to evaluate current direction (bummer), and these ripples are nearly symmetrical, which makes it a little more difficult to interpret than asymmetrical ripples. But a very cool primary sedimentary structure nonetheless.

Another great piece I found and probably the best new addition to my rapidly expanding rock collection:Some nice slickenlines on this siltstone I found while exploring the outcrop in the Hampshire formation. These silcken lines indicate faulting, basically as two rock bodies slid past each other, a smooth surface was left along the plane of slippage. This also gives a sense of kinematics, in the picture above the rock that was it was in contact with was moving up in relation to this rock.

Another closer view:In this photo the surface in contact with this rock was moving from lower right to upper left.

All in all this was the best geology trip of my life and I cant wait to return to some of these places, namely the Limberlost Trail and Veach Gap anticline land. This was a wonderful experience and gave me a chance to apply all my geologic training thus far in the field.  Talking about rocks in lab and examining  rocks under the microscope is one thing, but nothing quite beats getting your hands on some rocks in the field. Being in the field certainly  has its own set of discomforts, but  I will gladly take ticks, poison ivy and sunburn over traffic, “microscope eye” and sitting in the windowless lab all day. I have to thank my “van-mates” for the interesting conversation and all the great jokes along the way.

This last picture is from Aaron B. (far left), van-mate and fellow journeyman geoblogger . Also pictured is Jeremy and I, standing with only the most  sophisticated geologic research vehicle on the road these days. It might not look like much but this baby comes specially fitted with an advanced voice-activated command system ( which of course only responds to  Captain Jean-Luc Picard impersonations), audio inputs for some sweet tunes, and plenty of cup ( or beef jerky) holders.

TurboVan For Life.

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Responses

  1. This geology…. ROCKS. Well done!


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