The Eocene! Or is it….? Oh no. It definitely is :)

August 16th, 2010

I wrote th following post while sitting in Memphis airport Friday afternoon, but finally got my internet up and running last night in my house...Reflections Post still to come!

Been a little longer than usual between posts. The past three weeks I've been picking horizons and faults along my stretch of the Mississippi. My days were spent trying to find a reasonable interpretation of the data. It was tough going without feedback for two weeks, and I definitely worried that I was making bad choices on some of the lines and that a lot of my work was going to have to be corrected before we could move forward when Beatrice returned. At the same time, I met with Brian (one of the other P.I.'s on the boat) a couple times where we tried to determine whether I really was looking at the Eocene.

The first time we met we plotted my lines in GIS, so we could search for nearby wells. There were a lot of shallow, coal mining wells right next to my site. We went and looked at the paper well logs and did a rough estimate of where my formation was in comparison to mean sea level . This allowed us to get an idea for what type of sediment was present at each site at the elevation that we expected to find my formation. The data wasn't entirely conclusive but we were near or in clay for each case so at this point we decided I was indeed looking at Eocene. Then Brian got electrical well logs that were deeper. In these he traced a marker bed of the Memphis sand which is a very thick layer of about 400 feet through all three logs. Above this he could see the Cook Mountain and Cockfield which make up the Eocene/Claiborne. The problem was that both of these layers were very clearly present at a much deeper elevation then where I was seeing my formation. As a result we thought that I was actually looking at Quaternary! Which would have been extremely exciting because that would mean all the faulting I have observed is A LOT more recent than we initially thought.

Beatrice, Brian, and I met and took another look at some of the well logs. Looking at them indepth and using our basic trigonometry skills we ended up determining that I was actually still looking at Eocene, so the excitement there died down but this interpretation makes a lot more sense.

Then Beatrice and I met and we looked at some of my lines and began correcting them. I think I've learned more about picking horizons in the past two days then I did in the two weeks that I was working on it by myself. I managed to get all of the top Eoene done during our second day working together. Then we used that horizon to interpolate to a 3D surface of the area. Which unfortunately I don't have a screen shot of but it looked really cool! After that I finished picking the second layer and started picking the unconformity that marks the base of the Alluvial which sits on top of the Eocene. We believe the Eocene was eroded away in many places so what I am looking at is actually the very bottom of what a long long time ago was a thick layer. When I finish picking the unconformity we can map it in 3D and compare it to what we see for the Eocene. If there are some trends present in both or even better yet if a fault is present in both then that would mean these faults were active in the past 170,000 years!

Unfortunately, I actually left CERI today... but Beatrice and I have discussed it and I am going to try and keep working on the horizons from home. Hopefully it won't be too slow to run landmark on my computer. I'm keeping my fingers crossed on that account. Then in October I am almost definitely going to head back up to Memphis and finish everything up!

In the meantime I've also got to start writing my abstract which we're going to collaborate on remotely. Additionally, I downloaded ArcGIS Explorer, onto my laptop. This will allow me to look at and help interpret any new data Brian can find on my slightly mysterious geological time layer.

I'm really glad I've got the chance to come back because there is a lot more I would like to do with this project before calling it a wrap. Its been an absolutely fantastic summer but I'll put those types of reflections in my next post.