Today we woke up, excited to explore the amazing geology around our beautiful, peaceful, creepy mountain lodge. Our self-made breakfast and lunch packing were followed directly by a lecture from our new companion Josh. We received a brief overview of the geological history of New Zealand, and how the South Island came to be. Sitting at the convergence of the Australian and Pacific plates, the South Island is seated on both a converging plate boundary and a transform plate boundary. A really neat graphic showed how much this transform boundary has moved, bringing the South Island to the shape it is today. We also saw how quickly the mountains in the Southern Alps rose – about a centimeter a year. Over time, this should add up to mountains ~8 kilometers high. However, erosion takes off about the same amount each year, conveniently leaving the peaks in the Southern Alps approximately constant at ~3 kilometers.
Then we hopped in the van and drove out to Castle Hill. Aptly named, Castle Hill has numerous giant boulders, resembling castle towers. We studied them for a while (STC anyone?), and learned that they were marine limestones that had been brought to the surface by the same plate tectonics we had learned about with Josh earlier. We practiced taking a strike and dip on some of the deposits, then looked out at the overall geology of the surrounding landscape. As breathtaking as the view was, it was only improved by the bright yellow of the shirt of our very own Guil, who returned to us as we returned to the vans.
A few minutes down the road, we found Cave Stream. Cave Stream was the site of our main exercise for the day: to create a stratigraphic map of the region. This map would eventually include two formations, the Thomas formation, which formed 30-23 million years ago, and the Enys formation, which formed 20 – 5 million years ago. Layer by layer we analyzed the texture of the rock, taking special care to note the qualities of shell fossils found and the minerals in each rock. We also had the opportunity two see two of the beautiful limestone caves that give name to the area. Never having enough notes, as Guil reminded us, we spent about three hours at the area making observations. This was only broken up by a scenic lunch picnic on what was luckily a beautiful day. With our detailed notes done we made our way back to the vans to synthesize our data.
Back at our lodge kitchen/study space, with much thought we compiled stratigraphic logs with descriptions of each layer of the rock and interpretations of how the layers formed tens of millions of years ago. Most of the layers were deposited in shallow marine environments, forming limestone with the aid of countless marine organisms’ former calcium carbonate homes. Layers with shells more broken and worn were indicative of a higher energy marine environment. Overall, the sequence progressively shallowed, indicating New Zealand uplift! With our minds exhausted from analyzing at least 50 vertical meters of rock, we made our way over to another dinner buffet served to us by our wonderful lodge. This time it was cheesy potatoes, macaroni & cheese, and lasagna, with a berry cheesecake for dessert. What a way to end the day! The discussion of our daily activity even carried into dinner, when with much skepticism, we learned that bioturbation, from marine organisms like crabs and stingrays, is one of the reasons that grading (vertical orientation of sediment particles by grain size) is not seen in many marine depositional layers where it would be naturally expected. Truly tired, we submitted our final logs, and branched off on our own to relax for the rest of the night in our cozy lodge.
Thanks for still reading! (it’s the last week already?!)
Jagger and Robby
Tl;dr Woke up. Had breakfast. Josh lectured. Learned lots. Geology time. In vans. Castle Rock. Lime… stone. Cool stuff. Next stop. Cave stream. Saw outcrop. Many layers. Lunch time. More cave. More layers. Went home. Wrote stuff. Ate dinner. Crabs? Wrote more. Bed time.
Then we hopped in the van and drove out to Castle Hill. Aptly named, Castle Hill has numerous giant boulders, resembling castle towers. We studied them for a while (STC anyone?), and learned that they were marine limestones that had been brought to the surface by the same plate tectonics we had learned about with Josh earlier. We practiced taking a strike and dip on some of the deposits, then looked out at the overall geology of the surrounding landscape. As breathtaking as the view was, it was only improved by the bright yellow of the shirt of our very own Guil, who returned to us as we returned to the vans.
Back at our lodge kitchen/study space, with much thought we compiled stratigraphic logs with descriptions of each layer of the rock and interpretations of how the layers formed tens of millions of years ago. Most of the layers were deposited in shallow marine environments, forming limestone with the aid of countless marine organisms’ former calcium carbonate homes. Layers with shells more broken and worn were indicative of a higher energy marine environment. Overall, the sequence progressively shallowed, indicating New Zealand uplift! With our minds exhausted from analyzing at least 50 vertical meters of rock, we made our way over to another dinner buffet served to us by our wonderful lodge. This time it was cheesy potatoes, macaroni & cheese, and lasagna, with a berry cheesecake for dessert. What a way to end the day! The discussion of our daily activity even carried into dinner, when with much skepticism, we learned that bioturbation, from marine organisms like crabs and stingrays, is one of the reasons that grading (vertical orientation of sediment particles by grain size) is not seen in many marine depositional layers where it would be naturally expected. Truly tired, we submitted our final logs, and branched off on our own to relax for the rest of the night in our cozy lodge.
Thanks for still reading! (it’s the last week already?!)
Jagger and Robby
Tl;dr Woke up. Had breakfast. Josh lectured. Learned lots. Geology time. In vans. Castle Rock. Lime… stone. Cool stuff. Next stop. Cave stream. Saw outcrop. Many layers. Lunch time. More cave. More layers. Went home. Wrote stuff. Ate dinner. Crabs? Wrote more. Bed time.
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