Dresser compared to Shark Bay

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Dresser compared to Shark Bay

This is a transcript of a QuickTime movie (5.3 MB) recorded in the Pilbara in 2005. Martin Van Kranendonk, of the Geolological Survey of Western Australia, compares stromatolites at the Dresser formation with Shark Bay.


Here I mean you have clear evidence for currents, because you have this sort of, you know, up and down kind of swaliness and stuff. But they’re not the same as just normal sedimentary ripples and that’s a really important, you know, very fine distinction to make. But you can also see that there’s quiet a lot of vertical stacking in these things, in that they go up over a distance. They kind of texture again through there, but again, its all does this very fine, wrinkly laminate, and that wrinkly character of that lamination is very typical of biological or microbial life and stuff. Whereas sediments typically have this more even thing. But you do always see a sandy bit, you know you get that sandstone. And there is sandstone. There are some sand layers, higher up you get some very fine sandy layers. But you get these beautiful shapes up on the top, you get all these domes and these little conical forms, like this one in through here, is a beautiful little cone. There is another cone back here. And you can see sand draping in around the side of it. There is a big dome that’s exposed in three dimensions, sort of like a broader dome, and there are these little ones on top. I mean I’ve seen a lot of this also in Shark Bay ones and other ones.

Uhuh, I’ve seen pictures of Shark Bay ones that look just like these.

Yeah, they do look just like that, you will see them again tonight, why not? And then you’ve got these sand, look you’ve got all these ripped up clasts on top.

And clasts are?

Clasts are just fragments, bits. See how the rock gets really bitty? These are pieces of that microbial life that have probably dried out and then redeposited in little troughs between all the domes. And that again is really nice, it’s just beautiful, isn’t it? I mean that is just a beauty. Here’s another little one, and another one, they are all over the place. And also lots of different shapes. That’s what’s pretty cool too.




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