I have known for a long time about a diamictite in the latest Devonian part of the Appalachian stratigraphic sequence, since it is exposed in the lowermost part of the section (western end of the outcrop) at Sideling Hill, Maryland. When I led field trips there, I talked students through the multiple possible origins for … Read more
As longtime readers know, late summer is when my Rockies students submit their final projects – web-based explanations of key geologic sites they examined during the trip. Today, I offer you a guest blog post by student John Leaming. You’ll notice that I’m not *completely* absent from the post, however – I make a couple … Read more
The Neoproterozoic Purcell Sill is a stark, obvious black stripe in the strata of Glacier National Park. Here it is emerging from behind “The Salamander” glacier, above Grinnell Glacier Cirque: Zooming in, you can see the “baked” (bleached) zones above and below this concordant intrusion. But this time, during my visit to this special place, … Read more
Howard Allen, a retired petroleum geologist from Calgary, and longtime reader of this blog, contributed this week’s Friday fold: Subglacial drag fold (Pleistocene) in Upper Cretaceous Horseshoe Canyon Fm. bedrock (sandstone, shale). The locality is SE of Drumheller, AB at UTM 12U 394247 5692469 (WGS84). Did you hear that right? Yes, you did: This is … Read more
A quick virtual field trip to the Neoproterozoic glaciogenic sedimentary rocks from the central Virginia Blue Ridge province: Can you feel the chill of Snowball Earth?
My friend and colleague Lauren Michel, the King Family Fellow at the Perot Museum of Nature and Science in Dallas, Texas, sent me this image from her recent trip to Antarctica: (click to enlarge) This is a beautiful example of a mafic igneous sill, probably of the rock known as “dolerite” (or diabase, to us … Read more
Today, I thought I would share some images of lovely “textbook” glacial striations from rocks I saw in the Canadian Rockies this summer…
A final guest Friday fold from reader Howard Allen, who I’m pleased to be meeting up with in Banff late next week… Howard writes the following in describing this lovely scene: Warspite Anticline, Peter Lougheed Provincial Park, Alberta. Photo is a telephoto shot (hence the strong blue alpine haze–the colour cast is an accurate rendition … Read more
While on Corridor H last week with Team “Border to Beltway” (and USGS research geologist Dan Doctor), we stopped at the putative mass transport deposit. We still haven’t figured out which unit this is (It’s not the Foreknobs), but as we approached it, Dan wondered aloud, “I wonder where the top of the Devonian is. … Read more
This is the fourth of several guest posts that appear here this week, all written by students who participated in this past summer’s Regional Field Geology of the Northern Rocky Mountains course. by Tony Robinson Old Dominion University [youtube=”www.youtube.com/watch?v=XTWNmUNbBBU”]