Cross-bedding in Flathead Sandstone, Wind River Canyon

This is a boulder of Cambrian-aged Flathead Sandstone, the unit overlying the Great Unconformity exposed in Wind River Canyon, Wyoming. Click to make it 5000 pixels wide. Swiss Army knife for scale. It shows a lovely example of multiple upside-down cross-beds. It also shows a heavy layer of caliche on what is (now) the upper … Read more

Two Sisters

All this talk about footprints and tail traces, and I haven’t even shown you any “for sure” dinosaur fossils. Well, let’s remedy that today. We return now to the scene: exposures of the Jurassic Morrison Formation, on the east side of the Bighorn Basin, just north of Shell, Wyoming. I was wandering around, finding things … Read more

Tall tail

Okay, so I was out photographing ripples and admiring lichens, and then I saw this: That’s a rippled slab of sandstone, but with a linear groove that obliquely cross-cuts the ripple marks. Smaller, parallel grooves lie within the main groove. Here’s another look at that same one, spun around and zoomed-in: It looks as if … Read more

Ripple marks and cross beds in the Morrison Formation

This past summer, the day after my examination of basement complex along the Colorado/Wyoming border, I drove north to Greybull, and then with Virginia Museum of Natural History paleontologist Butch Dooley to a dinosaur dig site north of Shell, Wyoming. There, in the Bighorn Basin west of the Bighorn Mountains, are dinosaur-bearing exposures of the … Read more

Pilot Peak: a classic horn

Along the Beartooth Highway, east of Cooke City, Montana, you will see this striking mountain: Click through to make it really big. That’s Pilot Peak. It’s a horn in Wyoming. My Rockies students get really jazzed when they see it. Glaciers carved away the rest of the mountain, leaving only this pyramidal spire. Awesome.

Clinker

“Clinker” is an interesting rock type seen in Wyoming’s Powder River Basin. It forms when a coal seam catches fire, and cooks the rock above and below it, including the potential for partially melting the strata immediately above. Check out a few images of this intriguing rock here.

Split concretion

Concentrically-zoned ironstone concretion in sandstone of the Morrison Formation, eastern flank of the Bighorn Mountains / western edge of the Powder River Basin, Wyoming, at the Sheridan College dinosaur fossil quarry, last week. The white stuff is caliche. A quick post to celebrate the fact that as of three hours ago, Lily & I are … Read more