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Need help identifying sedimentary rock with fossils from Soap lake area washington state, have pictures?

For my geology class, I needed to find a sedimentary rock face. No easy task since I am surrounded by igneous basalt flows. As I was driving past Soap Lake, I spotted an embankment of whitish rocks and decided to stop. The rocks almost looked like cauliflower or popcorn. I was hoping it was a carbonate rock, and would qualify as sedimentary. I hit the jackpot and found freshwater fossils. :D Having trouble classifying and describing the depositational environment though. Would it be a conglomerate because it had lots of different particles and fossils? It was overlain with basalt and contained large basalt rocks (fist size) in the carbonate strata along with smaller pieces too. (It was not a graded bed). The particle size varied quite a bit. The strata tapered over a 50 foot area with a maximum height of 20 feet or so. I can scratch it with a finger nail, but don't know about reactivity to acid. (can't find my vinegar).

Can someone help me find the type of fossils?

Update 2:

I thought it might be part of the Ringold formation, but that is younger than the basalt that overlays it, which wouldn't make sense. Could the basalt flow have baked a stream or lake causing this formation? The soap lake area is the end of the grand coulee and was the outflow for the Missoula floods. Could this have be part of the geological equation? Just really confused with the way this fits into the geological time scale.

4 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    They're gastropods, and yep it looks pretty calcareous, maybe dolomitey? All consistent with a freshwater environment but not 100% necessarily. Their looks to be some bedding preserved in the top corner of your third photo doesn't there. So some energy moving stuff around, at least then. Elsewhere, burrowing before cementation or recrystallising carbonate may have destroyed any bedding, or maybe it was just deposited very quickly. Be careful that the dolomite clasts really are part of the original rock - I mean that they haven't fallen down the cliff face and been recrystallised on the surface. But your hand specimen looks pretty convincing.

    Don't know if I would call it a conglomerate with that few clasts (don't worry about the fossils when deciding if it is a conglomerate - it only refers to the lithic parts of the the rock). But not sure what the official cut-off is, if there is one.

    Don't forget, their might be a time gap between the whitish rocks and the basalt (or the whole lot might even be overturned). The contact between the two types of rocks might give you a clue about a possible time gap. Also, lava entering the sea or a lake produces some fairly characteristic shapes, like pillow basalts and cones.

  • 1 decade ago

    Great Pictures! This is beach rock, a leached limestone deposit with marine gastropod fossils. The inclusion of basalt, or an interface with basalt, suggests a pretty interesting geologic history. At least some of the later basalts have overlapped this beach rock. Nice job!!

  • 4 years ago

    Dinosaur fossils exist a approaches decrease than the floor, yet they are not generally got here upon until some thing happens to exhibit the rock layer that they are in. apparently you do no longer understand something appropriate to the geology of the midwestern US. the finished section grew to become into eroded with the aid of advancing, then taking flight glaciation and a huge lake grew to become into left at the back of after the glaciers receded. The erosion uncovered decrease layers of rock. Dinosaur fossils and human fossils are no longer got here upon in an identical layers. Hominid fossils and dinosaur fossils might the two be got here upon close to the floor, yet no longer at the same time and not in an identical geological formation. interior sight floods take place international, twelve months after twelve months. some places flood each twelve months. some places experience vast floods each century or so. when you consider that dinosaurs existed for 60-70 million years, it relatively is various animals, various interior sight floods for them to be caught in and various river or lake beds for them to have died in. there is definitely no reason to have confidence that the style of fossils shows a international-huge flood; if certainty be told, the easy actuality that dinosaur fossils are recent in distinctive layers with less difficult types below later types surprisingly lots disproves the thought each and all of the fossils have been shaped in one experience. i'm certainly particular which you will no longer examine this, even with the undeniable fact that. Creationists have not got any interest in data, and whilst presented with certainly technological awareness will cover their eyes so as that they do no longer ought to be certain it. scientific data are merely too threatening on your international view.

  • wolf
    Lv 5
    1 decade ago

    the rock in your photos are popcorn line stone it is formed by calcite which has been reformed with volcanic acid which is why it looks the way it does. I hope I'm right, I've been out of school for a while

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