North Central Arkansas; clam shell, but what compressed it?

[casadelshawn]

Got this clam with a mixed lot of fossils recently; this would normally go in the "leaverite" pile, but something odd caught my eye. I'm pretty good with Rorschachery, however, I'm wondering if this one's been bitten. It's about 5" long overall and has a line running through both sides that makes me wonder if something mouthed it at some point. It's most likely geological compression, but more eyes=better. 

 

Thoughts?

 

Thanks!

[Rockwood]

Looks very like post deposition movement of some sort to me.

[Oxytropidoceras]

From the flatting of the fossil, I would guess it is the result of the initial compaction of the sediment prior to it being lithified. Compaction is the process by which the volume of a newly deposited sediment is decreased and its density is increased. Typically, it happens in response to the weight (loading) of additional sediment on top the layer of sediment. The reduction in void space results from dewatering of the sediment and rearrangement of the sedimentary particles by downward displacement and reduction in inclination angle.

 

Compaction (geology) Wikipedia

 

Allsop, T., 1994. Early compaction history of marine siliciclastic sediments (Doctoral dissertation, Durham University).

 

PDF of Allsop (1994)

 

Yours,

 

Paul H.

[casadelshawn]

Woohoo! Great stuff, folks, as usual. Appreciate the help!