On Field Geology

I hate to blog about blogs, and have made a point of not doing so here - but involvement in this very interdisciplinary project has brought the diversity within the concepts of data and evidence, and how that diversity translates into field practice, to the front of my thinking lately.

Rapidly becoming one of my twice-daily-checks-for-new-posts is Kim Hannula's blog All of My Faults Are Stress-Related. Kim is a structure professor at Fort Lewis College in Durango. Already that sounds like a lot of fun.

Anyway, Kim just posted this excellent discussion about the practice of collecting field data - especially structural data - where so much of the information we have comes directly in the field, without any instruments fancier than a compass to rely on. Although we collect a lot of rocks (and probably some of the biggest rocks, with exception of the zircon pickers), there is usually absolutely nothing we can do to those rocks back in the lab which will make up for missing, or incorrectly interpreted, one little piece of the key field data.

In the process, we keep all the data in our heads as we collect it... rolling it around until it fits one or two or ten hypotheses, differentiating these hypotheses by using them to make predictions, then testing them, rejecting some, developing others. Sometimes I come to a set of hypotheses that require a detailed look at the microstructure, or some specific information on a rock's chemistry, to sort them out. Only then can we fall back on the lab. And even then, the field relations form the basis of the interpreted history of the rocks. That's how I see it. And that's why I need a lot more time in the field than some of my colleagues who can bring a lot of their data collection home with them.

Structural geology is the lens through which I view the rocks; but I need to know a lot more than my specialty in order to practice it. Being a structural geologist is like being a specialist in remodeling. I better know all about demolition, but I better know plumbing, framing, brick & mortar, etc. to get the job done. Since "structures" are the result of deformation and/or fluid flow through any existing rock, I have to know everything I can about all kinds of rocks, what they should look like when pristine or partially or fully damaged and altered. I have to know enough about chemistry to know what minerals will react with fluids or with each other, and I have to know enough about physics to interpret the relationships between the structures we see in the field and the stress which could have caused them. Then I have to put it all together in 4D. If I do my job well.

I complain a lot about the geochemists who have crawled over South southern Africa, collected miscellany and analysed the major, minor, trace, elements, REE and LREE and PGE and isotope ratios, of every rock on the side of the road - excuse the hyperbole - without a map to pin the data on. To me this is backwards geology, but as it's been driven by exploration, and as two of the three world record mineral resources on which empires have been built are primary and igneous (diamond-bearing kimberlites and the platinum-bearing Bushveld Complex) it was probably the best way forward for some time. In addition, this focus has built a cadre of world-class expertise in high concentration in a country with a relatively small academic community, in geographic isolation from larger academia. Our students all get jobs as geologists. Imagine for a moment the impact of that simple fact.

However, a holistic approach is needed to tell the African geologic story and recent moves in South African domestic and international collaborative work streams show that the community is moving toward interdisciplinary teams. Let's hope it will lead to a move toward more recognition of interdisciplinary people. I think that is the way things are going - generally - but just like at home, we are watching intently as the era of the sitting government winds to a close, wondering what the next administration will bring to all of us.


Kim said...

In the process, we keep all the data in our heads as we collect it... rolling it around until it fits one or two or ten hypotheses, differentiating these hypotheses by using them to make predictions, then testing them, rejecting some, developing others.

My field notebooks are usually a long string of questions, occasionally interrupted by some measurements. It's a good thing that I'm doing research for myself, and not for a client in industry - the chaos while I try to work out a reasonable explanation would confuse anyone who just wanted to know the conclusion (and who had questions about my competence).

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