You are browsing the archive for 2016 August.
31 August 2016
In Cape Town for the International Geological Congress, Callan hikes up Table Mountain and finds some superb primary sedimentary structures in sands and shales of the Graafwater Formation.
30 August 2016
It’s time to cover the third and final unconformity I observed this summer in the North-West Highlands of Scotland: the unconformity between the Neoproterozoic Torridonian Group below and the Cambrian Ardvreck Group above. Where I saw it, south of Loch Assynt on the mountain called Beinn Garbh (north of Canisp), it actually is displayed alongside the sub-Torridonian unconformity. The mountain hosts a “double unconformity”! Here is a view, looking south: …
22 August 2016
Let’s now profile the next unconformity in the sequence of pulses of erosion and deposition recorded in the North-West Highlands of Scotland. For a reminder, here’s a cartoon cross-section through the four relevant units: Today, we’ll look at the contact between the Lewisian Gneiss and the Torridonian Group (Diabeg Formation), marked with a “2” on the cartoon above, where it is exposed along the shore of Loch Assynt. There are …
19 August 2016
My friend Bill Burton (USGS, Reston) shared today’s Friday fold — Chevron folds in marble, Kings Canyon, California. Nice! Thanks for sharing, Bill!
16 August 2016
First in a series profiling the three unconformities to be found in the North-West Highlands of Scotland. Today: the sub-Stoer unconformity as exposed at Clachtoll. Explore a Proterozoic buried topography topped with coarse, angular breccia.
15 August 2016
The isle of Jura in Scotland is where George Orwell wrote 1984. It’s just across a narrow channel from the eastern side of Islay, where I spent four lovely days geologizing this summer. Looking across the gap, you can see a cluster of prominent mountains on Jura. These are the “Paps” of Jura, and they are held up by quartzite. I took these photos when driving home after an afternoon …
5 August 2016
Martin Schmidt again contributes a fold – this time from his summer trip to South Africa: Pretty great! This is part of the Cape Fold Belt. Perhaps some of you will drive by it when you go to the International Geological Congress in South Africa later this month! You can view the site in the context of Google Street view here. Thanks for sharing, Martin.
2 August 2016
This is the Split Rock at Clachtoll, on the shore of the North-West Highlands of Scotland. You’re looking out to sea, over the Minch. It’s the site that graces the cover of the excellent book A Geological Excursion Guide to the North-West Highlands of Scotland, by Kathryn Goodenough and Marten Krabbendam. “Clach toll” apparently means “Split rock” — Go figure. The Split Rock is an easy landmark to steer toward …