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UndercoverN

Could this be a bivalve mollusk fossil shell that i found in a Western Washington River?

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UndercoverN

Hello, I recently found what I believe is a mollusk fossil in a western washington river. Is it possibly a freshwater mollusk fossil (as I found it in a river that currently has freshwater mussels that live there)? You can see size comparison to my average womens sized hands :)

20170903_013207.jpg

20170903_013310.jpg

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Kane

Welcome to the forum. :) 

 

It might be a fossil containing bivalves, but we would need to see some pictures in brighter lighting to make out the details.

 

Whether or not it is a freshwater or marine fossil will not be contingent upon what the area looks like today. For example, in certain periods of the Paleozoic, your area might have been an ocean environment as opposed to landlocked as it is today, all due to continental drift.

 

One way of better determining that would be to get a hold of a geologic map of your area to determine age of the deposits. You can then also search for any range of paleo-maps that show what the area would have looked like as linked to the age of the deposit. 

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UndercoverN

Awesome, I will look that up right now and provide other pictures as well. Thank You !

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UndercoverN

This is what i found:  

Geologic Unit Label: Tc
Geologic Age: Tertiary
Lithology: Tertiary continental sedimentary rocks
Geologic Unit Description: Pliocene poorly indurated coarse sand and gravel stream terrace deposits; weakly cemented, moderately sorted cobble to pebble gravel with thin sand, silt, clay, and tephra interbeds. Pliocene-Miocene conglomerate (Pleistocene and Pliocene in Stoffel and others, 1991; now known to be Pliocene and Miocene, Schuster and others, 1997), pebble to cobble fanglomerate; fine and coarse semi-indurated fluvial and lacustrine deposits; locally includes mass-wasting deposits, diatomite beds, and tephra beds; locally fossiliferous. Miocene sandstone, siltstone, conglomerate, carbonaceous shale, claystone, and debris-flow breccia; commonly tuffaceous; locally includes tuff breccias, lahars, lignite, peat, and diatomite beds. Oligocene sandstone, variegated tuffaceous shale, and conglomerate with minor silicic tuff. Oligocene-Eocene sandstone, pebble and cobble conglomerate, siltstone, shale, claystone, and coal. Middle and upper Eocene feldspathic sandstone, siltstone, shale, conglomerate, and rare crystal-lithic tuff. Lower and middle Eocene interbedded shale, feldspathic sandstone and siltstone, and conglomerate; local minor crystal tuff and porphyritic dacite and rhyolite flows. Eocene conglomerate, commonly lithofeldspathic to feldspatholithic sandstone, siltstone, shale, mudstone, claystone, and coal; locally interbedded with basaltic to rhyolitic tuffaceous and pumiceous sandstone and tuff, volcaniclastic breccias, and lava flows; local fanglomerate and brackish-water deposits.
 
 
 
 
 
 
 
 
 

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Hapchazzard

I'm personally not seeing a fossil here, unfortunately. It looks like a suggestively shaped, eroded piece of conglomerate(though Cenozoic freshwater environments are an area of paleontology I'm definitely not versed in at all, so I might be wrong :) ). 

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