It was five years ago when I first visited Sea Point, the outcrop on the coast of the Cape Peninsula where the Cape Granite (~540 Ma) intrudes the (meta-)sedimentary rocks of the Malmesbury Group. The outcrop is (a) beautiful and evocative, and (b) of historical importance, as Charles Darwin visited it while on the voyage … Read more
A quick Friday fold – Ulundi Formation, basal Fig Tree Group of the Barberton Greenstone Belt, exposed in a creekbed etched into the trace of the Sheba Fault. This is one of the outcrops I visited one week ago today as part of the pre-IGC field trip to the Barberton. The rocks are iron-rich cherts … Read more
The news yesterday of 3.7 Ga stromatolites in Greenland prompts a closer look at 3.22 Ga microbially-induced sedimentary structures in the Barberton Greenstone Belt’s Moodies group sandstones.
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.
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 … Read more
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 … Read more
My friend Bill Burton (USGS, Reston) shared today’s Friday fold — Chevron folds in marble, Kings Canyon, California. Nice! Thanks for sharing, Bill!
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.
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 … Read more
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 … Read more