Tension gashes in Malmesbury metasediments near Sea Point Contact
A small structural geology treat – several en echelon arrays of tension gashes (quartz-filled veins) in Malmesbury Group metasediments, Sea Point, South Africa.
A small structural geology treat – several en echelon arrays of tension gashes (quartz-filled veins) in Malmesbury Group metasediments, Sea Point, South Africa.
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.
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
Pahoehoe “ropes” on a basalt, sample site unknown: Archean gneiss from the Gallatin Range of Montana: Tafoni in Malmesbury Group turbidites, South Africa:
My latest audiobook consumed during my commute was the story of Napoleon Bonaparte’s (why do we always call him by his first name?) ill-fated expedition to Egypt in 1798. Napoleon brought with him a corps of “savants,” natural historians, engineers, artists, and musicians, charged with documenting the history and natural history of Egypt, and helping … Read more
The Friday fold is a trio of hand samples of folded banded iron formation from South Africa. Collected in 2012 as float from the “contorted bed” outcrop in downtown Johannesburg, these samples are only now being cut and polished in the lab at NOVA.
My wonderfully named e-buddy Martin Bentley recently took a field trip to a quarry in South Africa (between Grahamstown and Fort Beaufort) where the Dwyka Formation is exposed: This poorly sorted sedimentary rock (a ‘diamictite’) is usually interpreted as glacial deposits (lithified till, or ’tillite’). Alfred Wegener cited these rocks and accompanying glacial striations (and … Read more