My research history, in time and P-T

I like Chris Rowan's idea of placing his research on a geologic time scale, so I stole his image and edited it:



Since I did some geochronology (actually, a major part of my PhD was explaining that it was impossible for my data to be meaningful), I felt like I should include the bad data as well as my preferred ages for events.

But the time scale doesn't have enough dimensions for my research, so here's version in pressure-temperature space.



All the green is actual data from Vermont. The blue arrow is supposed to represent my PhD work, except that the rocks were really lousy for finding any kind of data, and I didn't work on the low-pressure ones that told a better story. The red is Colorado, both my senior thesis and current work with senior thesis students. The yellow is one rock deformation experiment that a couple of my undergrad students in Vermont did one summer. And I figured if I was going to include the really low-pressure stuff, I ought to include the water quality stuff I've advised, but it doesn't really fit on the diagram.

The world's oldest rock is punny

I finally found time to read the paper describing the new World's Oldest Rock. I wanted to blog about why news reports seemed cautious about trusting its age (for instance, see Richard Kerr's write-up in Science). I need to spend more time thinking through the isotope geochemistry of the heavy rare-earth elements before that's possible, unfortunately. (Maybe a fan of extinct isotopes could help, since the argument is based on decay of 146Sm?)

But the problem, really, is that I got distracted by the mineralogy of the gneiss in question. The rock is described as a "faux-amphibolite," and is made of plagioclase, biotite, quartz, some garnet, and...

...wait...

...cummingtonite.

That's right. The world's oldest rock contains one of the favorite minerals of dirty-minded geology majors.

Other discussions in the geoblogosphere:

The Volcanism Blog
NOVA Geoblog
goodSchist (Chris mentions familiarity with the 146Sm-142Nd system; maybe he could help evaluate the paper)
olelog
About.com geology

(And they did a good job of linking to discussions in the media, so I won't try.)

Dude, what happened to Cenozoic stratigraphy when I wasn't looking?

There's all this discussion going on about the existence (or not) of the Quaternary Period, and whether we ought to declare a new epoch called the Anthropocene. Now, it's pretty scary, realizing that humans have had geologic-scale effects, especially on climate. But I've heard talk about the Anthropocene already. (Elizabeth Kolbert discusses it in her excellent book Field Notes From a Catastrophe.)

But I was shocked by another, much more mundane comment:

In recent decades, ICS--with the consent of the International Union of Geological Sciences (IUGS), the world's ruling body on such matters--dropped the Tertiary as well. (From the Science article about the Quaternary.)

Now, I've never worked on Cenozoic rocks. (Mesozoic, Paleozoic, and Precambrian, yeah, but never young stuff.) But my house is sitting on rocks that are mapped, even in very recent maps, as Tertiary. I live in a state where "Tertiary volcanics" is as common a phrase as "Quaternary alluvium." And, probably most embarrassingly, I've made students memorize a geologic time scale that included the Tertiary. (Not recently; my current institution has an excellent Historical Geology class, and I let the sed/strat/paleo guy deal with the time scale.)

I understand that stratigraphers have good reasons for wanting names that make sense, and for wanting worldwide correlations to be possible. But I like my Tertiary volcanics. And the K-T boundary.

Of course, I still haven't gotten over the change from "sphene" to "titanite"...