What's on my mind.

19 November 2008

Alabama Geology 101

Yesterday I actually got to go out and look at some real rocks. (Wo0t!1!) I took a bunch of pictures so of which were actually geological in nature. I thought I'd share a few to give my far-flung readers an idea of what it is like doing field work in Alabama.

First off, it was chilly (around 40°F/4.5C); although it wasn't so bad since I could do my work wearing real gloves and a hat didn't seem weird, as opposed to being in the office where I can only wear half-finger gloves to type and wearing my hat seems a bit of overkill.* It was almost nice in the sun for a little while. And it isn't nearly as bad as it can be (it is Alabama after all). Heck it was WAY nicer than field work in August and there's less foliage to deal with. Procuring lunch can be difficult is some areas. Ashville has a relatively new Mexican restaurant (in the shopping center with Ashville Drug, towards the interstate) that was pretty good. It is definitely a positive addition to the area. And to be fair, we were looking for shale outcrops in the 'mushwad'^, so large fresh exposures don't exist.

First stop was the longest and highest (3-5 feet tall by 160-180 feet long or 1-1.65 m by 56-60m), here's a representative picture:

It was a little too sunny for good pictures. There's a mylonitic zone right where my boss is looking about where the shadow starts. The contrast between sun and shade is almost too much to make zone visible in pictures.

Second stop was in the ditch on the side of a road:

This outcrop is about 1 foot high and 2.5 feet long (.3m high and .75m long).

Here are my co-workers take a strike and dip. The book is to even out and extend the tiny bit of rock sticking out of the weathered material. It doesn't give you much room to work with though. This outcrop does have the advantage that every few years the county will come and scrap it out potentially and temporarily creating better exposure.

Third stop by the railroad, very interesting, very complex:

We could spend days just getting data from this stop but it might give some clues to the internal structures of the mushwad.

Fourth stop by the railroad tracks further down, yay for resistant beds:

We tried to get a strike while the train went by but that amount of steel completely screwed up the compass. So all we could do was count cars until it passed.

The fifth outcrop we went looking for has been sodded over by the highway department. DOT is one out the best outcrop makers in Alabama (probably throughout the SE) and in Alabama we can stop and look at the rocks (in VA that's not allowed). Unfortunately the DOT doesn't appreciate the need to keep outcrops free of trees and bushes and likes to (at least try) to grass over rocks. They also have a tendency to shotcrete less competent strata - gunite running parallel to bedded - likely shale, gunite at high angle to bedding - likely fault, gunite over the entire outcrop - g@ddamn engineers, the secrets of the Birmingham anticlinorium could be hidden behind that.

*Actually, right now the system seems to working and it's comfortable. This may or may not last.
^area of thick structurally complex Conasuaga

No comments: