Tuesday, January 23, 2018

New Year - The Final Countdown

This semester is the final push to graduate on time.

No pressure.

I need to have my thesis ready to submit to my committee by March 12th.

So far I have drafts up to my results section. I'll be submitted monograph style as opposed to manuscript style. I hope I'll be able to put together a manuscript together afterwards.

I've crushed an adequate selection of samples and submitted them for XRD analysis. I tried to represent a range of diapirs, and rock textures at the different sites.  These include crystalline diapir material which is soft but has high toughness (scratches easily, but does not break easily), a friable "crust" which is very vuggy, and an intermediate rock which has varying degrees of friability, but is not vuggy, and surficial salts that crystallized on the surface of non-diagenetically related rocks and soils. The crust rock is frequently found in association with the intermediate rocks, suggesting that these samples represent different degrees of weathering.

Crystalline Rock

Crusty Rock, containing vugs and botryoidal crystal growths
Surficial Salts - Rock was found at the edge of a stream bed
with white salt minerals encrusting it.

"Intermediate" Rock - Friable, but lacking the vugs and
microcrystalline structure of the crust

In choosing samples in the field, and in the lab, I ran into a few difficulties.

One, is that not every sample type (i.e. crystalline, crust, intermediate, surficial) were present at each site.  This would be scientifically interesting.  However, it is possible that each type were present at each site, but I either:

1. Didn't sample them
2. Didn't see them
3. Didn't adequately define the types

I am mostly able to rule out #1, because I established early-on what I wanted to sample to gain a representative rock selection. However, at a few sites (like Whitsunday Bay Diapir, at which the helicopter landed in two places and we jumped out to go grab some rocks while it was still running) it is entirely possible I just didn't have enough time to search thoroughly. The absence of evidence isn't evidence of absence. Third, by its own definition, the intermediate rock has variable degrees of friability, and is often found in close associate with both crystalline and the crust rock. I separated it out to see if we can learn anything about the nature of weathering. As such, there is wiggle-room in determining which category some of the samples best fit.

Another problem is that it was terribly challenging to sample the surficial sediments. The best sample I was able to prepare for XRD required me to scrape off a sufficient amount of salt minerals off of a few pebbles I collected from a stream. The worst samples were where I found the salt precipitating on sand, and scooped up the salt and sand together. As a result, I only submitted a couple for XRD that I thought might provide reliable results, so data in this type may be lacking.

I should get some of the results back this week. It will be cool to see how the diapirs are weathering between anhydrite and gypsum, and how that is affecting their surface textures. 

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