Disconformity in northern Colorado
Have a look at this lovely (almost glowing) example of a disconformity between Coloradan limestone and overlying sandstone.
Callan Bentley
What do you see here?
Any observations? Any subsequent interpretations?
Absaroka volcanic breccia
A lovely example of a volcanic breccia (from the Eocene Absaroka Volcanics of southern Montana) is showcased, in two different photographs.
Monday macrobug: Huge honkin’ horsefly
Horseflies have such lovely eyes… …but man, they sure can open up a welt.
Friday fold: four more Proterozoic folds from the Laramie Range
To this and this, add these: Some interesting fold shapes here. Bob Bauer, who took me to this site, interprets these as interference patterns, evidence of two generations of folding: Happy Friday – for me, there’s only a week of summer break left, and then a week from today, I’ll be back at work.
Friday fold: 2Z
Two Z folds from the Proterozoic rocks of the Laramie Range, Wyoming – you get two since I’ve been so delinquent about blogging over the past month.
New Rockies GigaPannery
Several new GigaPans I’ve produced over the past few weeks in the Rocky Mountains of Montana and Wyoming: link link link link link link link link
Rockies 5 concludes
My Rockies field course has wrapped up for another year – the fifth year in a row I’ve run this intermediate-level ‘regional field geology’ course in collaboration with Pete Berquist of Thomas Nelson Community College. We were fortunate to be joined by two other professional geologists this year: Chris Khourey of NOVA and Tom Biggs … Read more
Which is older?
Using your relative dating prowess to determine which of these two rock units is older, the schist (dark gray) or the granite (light pink): Click to enlarge Click to enlarge Justify your answer by citing a principle of relative dating.
Friday fold: Summer sample #1
First sample of the summer – a new “pocket fold” showing Paleoproterozoic deformation in the northern Laramie Range, Wyoming.
Paleoproterozoic dikes in Archean granite, Laramie Range, Wyoming
At Morton Pass, where highway 34 crosses the crest of the Laramie Range, you can see a nice set of (younger) mafic dikes cutting (older) granite/gneiss basement complex. The pink stuff is Archean; the black stuff is Paleoproterozoic; around 2 billion years old. Click to enlarge I got to check out this outcrop on Tuesday … Read more
Monday macrobug: Jumping spiders that “Attack the Block”
A few weeks ago, I started seeing a new kind of jumping spider around our house. It was distinctive primarily because of its iridescent green chelicerae (think of them as “jaws”). I took a couple of blurry shots, but nothing I considered good enough for “Monday macrobug” treatment… These spiders reminded me of the unique … Read more
Friday fold: a lovely three-dimensional exposure
The Friday fold series returns to Kootenay National Park in Canada for a look at some folded Cambrian limestones.
Headin’ west
Well, it’s that time of the year again. Tomorrow morning, I pack up the car and head west. I’m giving myself five days to drive out to Bozeman, Montana, with three stops along the way to see people I like and talk about interesting stuff. Next week, my family flies out to join me. It’ll … Read more
Dwyka Tillite in South Africa
My wonderfully named e-buddy Martin Bentley recently took a field trip to a quarry in South Africa (between Grahamstown and Fort Beaufort) where the Dwyka Formation is exposed: This poorly sorted sedimentary rock (a ‘diamictite’) is usually interpreted as glacial deposits (lithified till, or ’tillite’). Alfred Wegener cited these rocks and accompanying glacial striations (and … Read more
Monday macrobug: Cranefly
Craneflies look like giant mosquitoes. They’re harmless to people – kind of like the giraffes of the insect world… In flagrante delicto…. Side-view portrait…
Sunset serenade
We had a lovely sunset last Thursday night:
Another example of the perplexing mystery “fossil”
In April, I posted some images of an odd structure from some of the fossiliferous siltstones of the Fort Valley. Some of the commenters suggested it was no fossil, but simply a very small scale version of soft-sediment deformation. Now, another “Fortian” has shown me another example, and this one is better preserved. Its lobes … Read more
Weathering rinds
Some cobbles from Wyoming, showing lovely weathering rinds: …And here’s another, with a “slice” off the front. It reminds me of a slice through a sushi roll!
Monday macrobug: Sarosesthes fulminans
This lovely longhorned beetle was on my house last week. Bugguide.net helped me identify him as Sarosesthes fulminans.