I will have to look into the MT geology Facebook page! Thanks for the insight. Have you heard of the Tobacco Root Geological Society? They do annual field trips and are a fun group of folks.
I am going to order the MT and ID updated Roadside Geology books. Thanks again for letting me know they've been updated. Alt and Hyndman did the originals years ago and I have been anxiously awaiting their updates. There are updated versions of the CO, UT, WA, and OR books too. Maybe even WY. They cover the areas I am most interested in.
Three books I typically carry with me for general rock and field geology identification are: Exercises in Physical Geology 10th ed. (I know there are more modern versions out there, but this one works for me), terry Maley's Field Geology Illustrated (I have the second edition from 2005), and finally a long out of print booklet from the U.K., Pat Bell and David Wright's Rocks and Minerals. Having not worked in the field for close to 20 years I've probably forgotten more than I was ever taught. These three books get the synapses popping in unison once again. Yes, all three are pretty basic, but very useful to a ROF. What do you take in the field for references? Oh, I always have a rock hammer in the 4Runner along with an old 10x hand lens. Probably should carry a squeeze bottle of 4% HCL, eh?
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I have in fact heard of the TRGS and I meant to mention that earlier. Membership is practically free and from what I've read in various prior year annual field trip guidebooks online, it does seem like a great group. With retirement looming, maybe I can schedule a TRGS annual field trip soon.
I've got you beat on elapsed time since I did field work: My last day in the field as a W-2 employee of a mineral exploration outfit was in October 1983. Some of my old Appalachian State University textbooks still refer to geosynclines and related theory, only mentioning "new emerging plate tectonic theories".
I began a slow "return to the fold" (pun intended) a few years back when one of my ASU classmates retired after 40 years in the Houston oil patch and bought a vacation home in our old college residential neighborhood. We both joined the Carolina Geological Society and have gone on 3 or 4 of the annual field trips since then. That started me getting interested in my southwestern MT Field Camp areas and the rest is sure to bore non-geologists to tears. Suffice it to say that most of my evening reading has for several years been geology related (I haven't routinely watched network or cable television in probably 5 or more years).
I have the Roadside Geology volume for all of the Rocky Mountain states as well as a number of East Coast states + some similar references related to California (notably some of the "Geology Underfoot" volumes). Between those and DeLormes, Benchmarks, NF paper folding maps, and the occasional Trails Illustrated folding map, I keep a fair load of rolling library in the truck. Enough to annoy my wife, anyway. And yes, my old rock hammer, belt holster, hand lens, and my treasured Brunton are always on board.
What I most enjoy today, as mentioned above, is "structure you can see" at all scales--macro, micro, and everything in between. Fault contacts, folds, slickenside, contact metamorphism, and in particular mineralization related to contact metamorphism (a throwback to my prospecting days). More recently, and entirely due to Rob Thomas' and Richard Gibson's terrific regular contributions to Montana Geology on FB, I've become fascinated by the Yellowstone hotspot and the related tuffs, flows, and tephra draped all over the place in SW Montana and Idaho. That, and syntectonic deposition and deformation of units like the Beaverhead Conglomerate (K-T). Next year I hope to find the outcrops of thrust fault contact with the Madison Group (M) carbonates pushed up over the Beaverhead Conglomerate (K-T). Seen some pictures, and it's right up my alley. I'm also keen to see some shatter cones from the Beaverhead Impact Structure in MT and ID, and I expect to do exactly both of those on a drive-by basis in July 2022.
Last, I here thank Ace, Byways, dierkz, and devero4 for their contributions to this discussion, not the least for their patience as two "senior geologists" burn up some bandwidth with a bit of somewhat off-topic recollections.