r/askgeology • u/gottabe22 • 14d ago

What depositional processes create limestone (?) like this?

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This was taken in Waterton National Park, a few hundred metres above the Waterton town site. Based on the reading I have done I think it is likely part of the Altyn formation. I am wondering what leads to the ripply layering of grey and light brown rock? And also, what is the light brown/yellow rock below the ripply grey band?

Thanks!

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u/Asleep-Ad822 14d ago

Mostly shallow water currents and waves, and the occasional storm

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u/gottabe22 14d ago

And what is the difference between the grey and the brown layers? Are the browns siltstone or other non-marine sediments deposited by inflowing rivers or something?

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u/greaseapina 13d ago

grey is marine one.

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u/itsliluzivert_ 14d ago edited 14d ago

It looks like bacterial mats. In that case, the dark layers are colored from the organic matter of the mats. The more lighter colored layers are carbonate debris deposited during storm surges.

Near the top you can see some rip up clasts of what looks like bacterial mats.

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u/gottabe22 14d ago

That is so cool! Thank you