Dresser formation

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Dresser formation

This is a transcript of a QuickTime movie (3.4 MB) recorded in the Pilbara in 2005. Martin Van Kranendonk, of the Geolological Survey of Western Australia, introduces field trip participants to the Dresser formation.


We've got preserved here a pretty thick section of the Dresser formation. It varies from place to place quite a bit and that's part of the story that you are getting faulting during accumulation of the sediment, but we are up towards the top. The stromatolites you’ll see are all part of this succession of bedded material and in through here and right at the bottom you see beautiful ripples of the sandstone that underlie the wrinkly laminated mats and those ripples are exposed around the top there as you can see you can get a paleo current direction from this stuff. These rocks are so well preserved, that you can still get the idea of the very shallow water and the currents moving back and forth, and this is a locality that has been known about for a long time, certainly prior to any of my mapping. I was introduced to it by Arthur Hickman the first year that I came up. It is a place that takes lots of people, so it's been on film, video and camera. But there have been lots of places where you can see that blocks have been taken by, I don't know who, but there’s big chunks taken out of here. So there've been samples taken and there is a big slab of this wrinkly black laminate material that went years ago. But every year we come back there is little less material taken out and it's in a big outwash area. So if you get a big storm event you get lots of rain coming down and boulders will knock it off. That's part of natural erosion, that's fine. We try and reduce the human impact as much as possible. So these beds, they curve around a little bit, they are gently folded, they go wavy back and forth and there are lots of horizons with these structures.




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