January 23, 2012
I’m back home in Cape Town, so I thought I’d post a local picture for this week’s Monday Geology Picture. The above picture shows a small, dark-colored xenolith in the Cape Granite, a 550 million year old granite that has megacrysts (very big crystals) of feldspar. This xenolith is most likely a small piece of the Malmesbury Group, an older group of rocks that consists of alternating grackwacke sandstone and slate that have experienced significant uplift and metamorphism. The above xenolith was observed at Clifton Beach, a fancy beach area known for its bright white beaches which result from the weathering of the Cape Granite. Abundant xenoliths, such as the one above, can be observed in the granite boulders at Clifton Beach. I took the above picture when we took my husband’s cousin around to look at a few geological sites in the Cape Town area .There is a 5-Rand South African coin for scale in the picture; this coin is slightly smaller than an American quarter.
I have a few thesis deadlines looming, so for the next 2-3 months as I prepare for my thesis defense this blog may consist mostly of short picture posts. If time permits, I’ll try to slip in a few geology words and longer posts, but my thesis comes first at the moment. Hopefully the pictures will be enough to tide over my readers as I wrap up this PhD of mine.