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27 June 2013

Paleoproterozoic dikes in Archean granite, Laramie Range, Wyoming

At Morton Pass, where highway 34 crosses the crest of the Laramie Range, you can see a nice set of (younger) mafic dikes cutting (older) granite/gneiss basement complex. The pink stuff is Archean; the black stuff is Paleoproterozoic; around 2 billion years old. Click to enlarge I got to check out this outcrop on Tuesday with colleagues from the University of Missouri and the University of Wyoming. Deformation in the …


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24 January 2012

Paleoproterozoic stromatolites from the Malmani Dolomite (Transvaal Supergroup)

After our safari, Lily and I were taken up onto the Great Escarpment in northern South Africa. The escarpment is supported by sedimentary strata of the Transvaal Supergroup that overlie the Archean basement rock of the Kaapvaal Craton. The Transvaal strata are Paleoproterozoic in age, somewhere between 2.5 and 2.0 billion years old. They are a mix of siliciclastic sediment and carbonates. Here’s the view from an overlook dubbed “God’s …


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23 January 2012

An ancient delta at the Three Rondawels?

Here’s a look at what you see if you go to the Three Rondawels viewpoint above the Blyde River Nature Reserve in northern South Africa: A lovely scene. The three mega-hoodoos on the left are the eponymous “rondawels” (pronounced ron-da-vulz), which is the Afrikaans word for a round hut. These erosional remnants are more or less cylindrical and of the same dimensional ratio as the huts, so this name seems …


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29 March 2011

Tillite in outwash

Hoo boy. This one made me yelp… While on the glacial geology of western Pennsylvania trip last Saturday, we visited a gravel quarrying operation. The operators were extracting gravel from a glacial lake delta deposit, and it was full of glacial outwash — sediments washed out from the melting front of the Erie lobe of the Laurentide ice sheet. We were there to look at the Pleistocene features, but several …


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