Callan reviews the geology of the superlatively auriferous Witwatersrand Supergroup of South Africa, and then zooms in on a distinctive marker bed near the base of the sequence. The deformation in this particular banded iron formation (BIF) is an aesthetic wonder, as this suite of images reveal. The layer outcrops in the heart of urban Johannesburg.
Today’s fold is an anticline and its neighboring syncline, both exposed along a newly-opened stretch of New Route 55, west of Moorefield, West Virginia. The new Route 55 is a classic porkbarrel boondoggle courtesy of the late Senator Robert Byrd, but doggone if it didn’t open up some lovely new roadcuts. Here’s a stitched image … Read more
Whilst at the JMU Field Camp in Ireland this summer, my former student Alan Pitts (author of Not Necessarily Geology), collected this lovely “pocket fold” near Derryclare Lough and brought it back to the States. A couple of weeks ago, after a graduate school advising session at a pub in Fairfax, Alan gifted me the … Read more
Callan visits the Burgess Shale in British Columbia’s Yoho National Park on a guided tour. This photo-heavy post discusses the depositional setting of this world-famous Cambrian fossil deposit, the landscape along the hike, and (of course) the fossils themselves.
West of Shell, Wyoming, on route 14, there is a lovely exposure showing the tilted stratigraphic contact between the lower Tensleep Formation (purple; Pennsylvanian period) underneath Goose Egg Formation (orange/tan; Permian to Triassic in age). The contact dips to the west because it has been deformed during Laramide mountain-building (uplift of the Bighorn block, and … Read more
I just drew up a little checklist for the different formations my Rockies students will be seeing next starting next week out in Montana: The original black and white images (two columns on two pages) come from Self-Guided Field Trips Near Bozeman (1982), by Stephan G. Custer, Donald L. Smith, Molly Walker, and 1982’s crop … Read more
Another day, another geology LOLcat challenged issued by a geoblogger… Okay, I’ll bite: Other geology LOLcats have been found curling up all over the geoblogosphere in the past 24 hours: Outside the Interzone Georneys
The Shenandoah Valley of western Virginia records the switch in late Ordovician time from passive margin sedimentation associated with the Sauk and Tippecanoe epeiric seas, to active margin sedimentation associated with the onset of the Taconian Orogeny to the east. Higher up in the stack, a similar pattern is seen: a return to passive margin … Read more