In the last couple weeks, I've heard a number of comments about geology terms that are unnecessary or outmoded. The Cordilleran tectonicists at the Las Vegas GSA meeting kept making jokes about how they weren't supposed to use "miogeocline" (which means essentially passive margin, and which replaced "miogeosyncline" after plate tectonics became accepted). "Greywacke" also seems to be on its way out. In the geoblogosphere, Olelog asks whether we need the word euxinic. And then there's this wisecrack from Ammon Shea, who is writing a book about reading the Oxford English Dictionary:
For instance trondhjemite is defined as ‘Any leucocratic tonalite, esp. one in which the plagioclase is oligoclase’. I have my doubts as to whether anyone has ever thought to themselves ‘I wonder what trondhjemite means?’ But if someone did, and went to look it up in the OED, it seems unlikely that this definition would clear things up much.
I disagree with Shea. I know what a tonalite is, and I know what oligoclase is, but I often need reminding of the precise definition of "trondhjemite." I've got even more problems remembering the definitions of other igneous rock names ("alaskite," "pantellerite," "hawaiite," "benmoreite," etc.) but that's partly because I've worked in Precambrian rocks, and lots of Precambrian geologists talk about trondhjemites. So I think the definition in the OED is useful, but I'm not so sure that the term itself ought to remain in active use. (By the way, if Shea wants a really impenetrable geologic definition, he should see the definition of cactolith.)
So I'm curious. If you could get rid of five geologic terms as unnecessary and/or outdated jargon, which ones would you choose?